Darkshot

iTrader: (4)

Everything about my suspension is brand new...including stock height iroc springs. I do have poly bushings and Koni red shocks, but thats the only thing thats not a stock style replacement. My car has horrible wheel hop. I cant give it anything in first gear or it will hop like mad. And if I manage to make it through first gear without hop, on the 1-2 shift it starts hopping as bad as ever. I cant imagine my bolt on L05 is making more power than the most powerful factory thirdgen, so my question is did these cars wheel hop like this from the factory? And if not, what is so different about my car that is making it hop?

duckmanquacker

check your trans mount they break and give you the effect of wheelhop

sofakingdom

iTrader: (1)

Yes.

The design of their suspension is seriously flawed, in ONE small detail. Fix that, and it becomes a PRETTY GOOD design.

That detail is the rear control arm angle. As the car comes from the factory, the arms are roughly level. When you accelerate, the rear of the car tends to "squat" (a VERY VERY VERY BAD thing, but hold that thought for a minute). In other words, the car DROPS in the rear, which most people would consider "normal". But... when the car drops, the angle of the control arm suddenly becomes MUCH worse. The front ends of them, where they attach to the frame, become lower than the rear ends of them, where they attach to the axle. In other words, the control arm is then angled UPWARDS from the frame to the axle.

Think about that for a moment. Go out and look at your car, and visualize this in your mind if you need to. Remember, those control arms are THE ONLY thing transmitting the force generated by the tires, to the car; ALL of the force accelerating the car passes through them. So, as you look at your car, let's say you're looking at the left side, and that piece is just about level; but if the rear of the car moves DOWNWARD, the front end of the LCA (the left end, as you're looking at it) becomes lower than its rear end (the right end); and the axle is trying to PUSH as hard as it can TO THE LEFT, in order to accelerate the car. Right? Get that whole picture firmly in your mind, and come back and read the rest of the answer.

Now.... what happens if the axle is pushing straight to the left, but the arm is angled upwards from left to right? Exactly... the rear end will attempt to rotate itself up off the ground, just by the force it puts on that arm!!! So what happens is, the axle begins to push on the car; the car squats; the arm beomes angled that "wrong" way; the axle attempts to lift itself; that reduces the traction of the tires; the tires (or, more accurately, the right one) begin to spin; the force pushing the axle goes away; the force trying to lift the rear off the ground goes away; the springs push the rear back down; the tires suddenly get traction again; the pushing force is restored; the car squats; the arm becomes angled the "wrong way; the axle attempts to lift itself; ........ and the process repeats, about 7 times a second or thereabouts, usually. Sound familiar?

We call that action "wheel hop".

The solution is to alter the suspension so that the control arm is angled slightly DOWNWARDS, so that in case the car squats, it doesn't end up angled UPWARDS any more. Voilà! Instant wheel hop cure!! In fact, you can angle it downwards SO MUCH, that instead of SQUATTING, the act of accelerating actually DRIVES the tires INTO the ground HARDER by RAISING the rear of the car, instead of trying to LIFT the tires off the ground by DROPPING the rear of the car. You don't generally want to go far enough to make it do that (or at least, not very much of it) on a street car, for other reasons; but for a single-purpose strip-only setup, it's pretty common.

The part that does this is called "lower control arm relocation brackets". They weld onto the axle where the control arms attach, and fix the faulty factory geometry. Very cheap, very easy, UNBELIEVABLY effective. Here's a crappy picture of what they look like. These are from Spohn (board sponsor, link located along the right edge of this page).



Better control arms help too. I have the Lakewoods; again, cheap, but HIGHLY effective, for a street car. The next step from there is a better torque arm, that doesn't flex and thereby store and release energy; such as the Spohn one. When I put that into my car, it was like taking a giant rubber band out of my drive line somewhere.

But the absolute biggest traction "bang for the buck", maybe bigger than tires even, is those brackets. Start with a set of those and new aftermarket LCAs, and see where that gets you.

EvilCartman

iTrader: (1)

That bracket doesn't look right to me unless the design is different than mine. Think I remember in the instructions saying the bottom should be parallel to the ground. I'd think with it angled like that you'd have to move the axle forward or backwards for things to line up.

InfernalVortex

iTrader: (4)

So the lower control arm angle stock is bad for launches, but I've heard it's actually good for handling. Is there any truth to that?

Sonix

iTrader: (1)

Having it parallel is better for handling. He recommended *slightly* angled (down in the rear), so that under power it'd be parallel.
I think having too much (down in the rear) angle would induce "roll oversteer". Do a search, I know Dean explained this before, once upon a time.

sofakingdom

iTrader: (1)

Looks like EXACTLY the same bracket as mine? Installed EXACTLY the same way?

Note that my pic isn't exactly horizontal; the camera is sort of tilted. Kind of skews the view somewhat.

I don't know about "bottom parallel to the ground"; but, mine are installed such that all the bolt holes, including the stock one, are in one arc, centered on the front LCA bolt on the frame; so no matter which hole you put them in, the wheelbase stays the same. I think that's the objection?

Yeah Dean likes to argue about that, has actually got himself banned for that very argument. Pretty humorous actually. For someone that's as overall smart, experienced, and knowledgeable as he is, he SURE DOES have a couple of blind spots, including that one. Another of which is, his general manner of speaking.... he's even more abrasive than me, which I could hardly believe possible without seeing it.

Duracell Bunny

Dean just has to repetitively deal with blind explanations like the one you just butchered above.

Most peoples problems are multiple. They add LCARB's as a bandaid fix to other problems like shocks and coilsprings being insuficiant, or worn bushing elsewear causing poor geometry during thrust deflection.

So if everthing else under the car is 20 years old and abused from time then adding LCARB's and keep lowering them time after time until the back gets low enough the wheelhop WILL eventually go away. But you've just cause yourself an unsafe handle car at freeway speed in an energency. Fix the real problems and sop doing band aid fixs. IF you can't afford to fix the other probelm areas then stop doing burnouts and you will not have a wheel hop problem. You shouldn't be doing burnouts if you can afford to keep a car in good maintinace. BUt to each his own- its your wallets.

Food for thought- THey did not want you doing burnouts in these cars from the dealerships under warantee. THe rest of the car IN STOCK FORM is not intended to hold up to abuse like that. THey were sold as a generic daily commuter with a sports car look and feel. ITs not a race car in stock form- especially one 20 years old and in need of maintenace (bushing replacements, metal fatigue, poor shocks,etc...)

So now I will make it complex. If you have built the entire car with adjustable heavy duty aftermarket parts and braced the frame and are now prepared for raw HP abuse on launches, you will want to have you IC set through tqarm length and LCA angle so that the transfer weight load makes the LCA's parallel to the forward thrust angle (generally speaking this is PARALLEL to the ground) so that bushing deflection is to a lateral thrust and all inertia is transfered directly as forward momentum as possible.

You picked your own name Sofa not me. I just try to help and weed through the constant BS.

sofakingdom

iTrader: (1)

Hi Dean!! Glad to see you re-registered with yet another userID! That makes how many now.... about 30 or so? I do like the name you picked this time though, describes your situation fairly accurately.

I'm sure we'll be seeing each other around; especially every time you try to argue with what's KNOWN to people who use it, to WORK; and people, like me, who can easily back it up with science and theory, and don't have to rely on invective.

Nice to have you back again!

Guest

Yes, some did hop right from the factory. I remember flogging one 87 350 Formula out in the back roads near Santa Maria, CA one day on a 6 or 7 mile car and we left some nasty black marks on the pavement a few times. That little 210HP 350 had enough power to wheel hop on what was not the best pavement (but not too bad, just enough to get the suspension in a bad position) so...

Anyway, your choice what you want to do. Both the above are right. The factory LCA angle sucks. I think the combination of rubber, the parallel LCA's and the torque arm just make life worse. A spring/shock combination that can control the axle is a good idea, and having the correct geometry on YOUR car is a good idea as well. None of these cars sat equally from the factory, so look at yours and go from there.

What springs? You didnt say. Loosen up those bushings while the car is on the ground, then tighten them up again while the car is still on the ground to make sure they arent binding from the get-go.

Dewey316

Lets see this science and theory.

(back from my leave of absence to stir the pot.)

Zepher

iTrader: (1)

Tires can cause wheel hop as well, at least it does on my car.
My Nitto 555RII's usually hop more than my Nitto 555's. both tires are the same size, just one is much stickier than the other (RII is the sticky one)

EvilCartman

iTrader: (1)

Cool, as long as it works out all the same in the end

Darkshot

iTrader: (4)

Well as far as worn out factory parts, my car has the following parts involving the rear end:

Subframe connectors
Koni red shocks on high
Brand new Moog IROC springs (stock height)
Brand new UMI tubular panhard bar (w/ poly)
Brand new UMI tubular LCAs (w/ poly)
Poly sway bar endlinks and bushings
Cheap Kumho tires (AST 245/50/16)

I think I've clearly eliminated all the usual "problems" that plague the typical daily driven thirdgen in this day and age. Funny part is when I got the car, before it had ANY of this (and consequently sat lower due to the old springs) it did not wheel hop at all.

Guess its time for the relocation brackets.

sofakingdom

iTrader: (1)

Right; the comment up there about "old worn out parts" is not to be taken seriously. As you have already found out anyway, so it's not much of a surprise I don't guess.

These cars did that from day one; as anyone who drove them when they were new, would know.

The more your tires hook up, the worse the problem will be. More traction = more force available to start the whole system to resonating as I described. I don't know how "sticky" those tires are; but if they hook real good, better than whatever was there before, then they may have been able to cross the line between merely spinning, and the whole "hop" scenario.

Wheel hop can be described in terms of Instant Center (IC) as well; but that's a little hazier to see how it does what it does. Much easier IMO to imagine what happens when you push on the end of a long hinged thing that's at an angle to the pushing force.

Looks to me like the brackets should help, since you have most of the other energy store-and-release problems taken care of (like the stock LCAs).

Duracell Bunny

Described in terms of IC.. Saywhat? ...long hinged thingy..Huh?

Sofukingdumb, Does your mailbox read MALEBOX ?

This is just good cheap entertainment. Dude stop really, you are confusing the poor guy.
Do you realise who you are up against in this pissing contest to out knowledge me and try to make me look bad? Do you know I am a Crewcheif on a NASCAR team? I didn't think so. And what is your credentials? (yes it was time I pulled out that trump card for this mental giant.) I am the tall one on the right. Jesse is an aquaintance of mine and has driven our Supertruck in our driver development program.
http://www.cardomain.com/ride/518752/11

sofakingdom

iTrader: (1)

Dean, I'm so glad you're back! I've missed you for all this time you've been banned. Thanks for re-joining (under yet another userID) and giving us your "entertainment".

Guest

I see lots of poly. When you tightened up all the parts was the car in the air? I dont know what UMI is using, but make sure you loosen all the bolts and tighten them when the car is sitting on the ground, level. Poly has a known tendency to bind and its possible you preloaded the poly adding an unknown variable spring force via bushing bind. Lets eliminate that first, if you already havent.

Duracell Bunny

Darkshot,

Even though you have what you self describe as "cheap Kumhos" They are still better than the tire compound that came new on the IROCs back in the 80's and early 90's. THe cars suffered from this new with new bushings. So your new poly bushings aren't going to be much better than brand new urethane bushings (they are better, but not by much when new- Urethane last so much longer so used urethane against used rubber is where they shine) so the urethane LCA's are not any cure (nor would rodend LCA's be either).

Koni reds are a step up better than factory IROC shocks, but not a whole lot more compression force at all. Better on rebound, but again not much. SO- the addition of better shocks is counterbalanced by better grip tires and you are back where you started basically in the balance of good and bad= wheel hop. You will need stiffer spring rates and higher damper shock valving to couhter balance the higher grip tires. Just by dropping the relocation brackets adjustment can and will get better off the line charateristics, but will cause mild to severe roll oversteer which can be downright dangerous on a daily driver at freeway speed. All so you can burnout without wheelhop.
You are armed with knowledge, its ultimartely your decision on how you what to set things, or buy the heavier duty parts and keep the geometry safe and allow you to burnout without wheelhop.

Where does this stop? Next time you buy even better grip tires (and technology is heading that way) are you just going to drop the LCA's at a steeper angle and become even more dangerous at speed? You have to marry your componants for your needs and keep adjustnments so the geometry stays safe and proper.

i_love_thirdgen

iTrader: (3)

the number one thing I love about these arugments Is that I get to sit back and watch, while taking notes for when it's time to do my suspension.

dennisbernal91z

iTrader: (2)

I run Nitto 555rs, tube LCAs, PHR, TQ arm and all that. Stock springs and KYB AGX shocks. I set the rear at 6 of 8 (8 hardest) and mash the pedal, and there is no wheel hop. I do not have relocation brackets. I feel like I do not hop due to my stiff rear springs. I also run -1 pinion angle. Not sure if that has something to due with it, but it should. LCA are level with the ground pretty much.

Anyways, thought I would just chime in.

PS- my car makes 344 RWHP and about the same TQ, over 300 TQ by 3K. .... still no hop.

Sonix

iTrader: (1)

Does the car launch dennis bernal, or does it go up in smoke?

I'm about to weld on some LCARB's right now, because I get fairly bad wheel hop. Main thing is that i'll have adjustability, I can use the stock hole if I wanted to. Either way, I think with my tall tires my geometry isn't perfect anyway.

"Roll oversteer on the highway" - Can you describe this Dean? I mean, how would I know this is happening? Car would feel like it wants to fishtail when i'm passing someone under acceleration?

Dewey316

Nice, brough this up again. Care to show us how this works. I am really excited to get to learn something new.

BTW, You promised earlier, to prove with science and theory, let see it. I'm still waiting.

Sonix,

Roll over steer is when you end up with rear steering. As you turn one side of the rear suspension compresses (such as in a corner), its effective top view length changes, causing the rear axle to move for/aft on opposing sides of the car, this gives you rear steering. If this is bad, you make a hard lane change, and the suspension makes the rear oversteer. You end up having to make tons (relative of course) of correction steering, you end up sawing the wheel, and that makes the car very unsorted. Think of it like really bad bump-steer, but at the back of your car.

--John

Duracell Bunny

Yep, what John Dewey said, He knows his stuff.

Sonix, It basically would be a problem when in an emergency situation and you have to react with a fast steering imput at higher speeds.

Remember recently when Eddy Griffin (The actor from Redline- that movie was filmed in the very garages I scale my racecar in for races at Irwindale) was driving that Ferrari Enzo and crashed it into the wall. He went in too hot and when he braked and cranked it to turn it induced roll understeer and keep going straight. Even a high performance car is aligned and setup to be more safety friendly and take a hit head on rather than inducing roll oversteer and *** ending the car into the barrier or hitting it sideways and t-boning the driver into the door with side impact. Car designers purposely setup cars from the factory to induce roll Understeer to help keep people safe. Readjusting and inducing roll oversteer will make the rear of the car shoot out rapidly and uncontrolably you will never save it. A fine balance inbetween is what you really desire for a well handling sports car with respectably skilled driver behind the wheel. But even a neutral car can hurt an unsavoy driver that has not one bit of recovery skills and wipe out everyone around them. The reason why that Enzo sucked to turn is front alignment settings were conservative so it would not bite. Proof that even a high end exotic sports car sucks unless soone skilled adjusts away from the factory alignment specs and makes it bite on turn in.

If its any conselation- My car is setup on the roll understeer side- and is balanced using the front alignment adjustments as a tool to get it to rotate quickly but not shoot out rapidly and non stoppable causing the car to spin.. My car is not roll neutral, nor roll oversteer. You hear from reports of its ability that it is no slouch in corners. Roll understeer keeps your slip angles of your tire treads more consistant front conpared to rear. It helps keep the tire heat ranges more even keeping the overall front to rear grip coeficiant neutral when the core temps rise from track usage. When either the front or rear tire temps breach grip level temps, that front or rear will break traction first and completely go away until the car sits and the core temps cool back down. Roll understeer lets the rears steer and create more a slip angle like the front tires that do actually steer. Best way to give an analogy in this is to compare 2wheel drive to 4 wheel drive for traction, well, roll understeer is like 4 wheel steering to pull the car in that direction. The wheels that steer the car are the inside wheels of a corner. Most people think its the outer front wheel that steers the car- wrong.

Just another tunning tool for keep race tires in even temp ranges.

Zepher

iTrader: (1)

What happens when the two inside wheels come off of the ground when you corner? My friend Toms' BMW 3 Series does this quite often on the auto-x course.

Shagwell

both inside tires? Too stiff of spring, or too stiff of anti roll bar, or too high of CG. If the outers hold well enough to lift both inside tires, I would tend think his entire combination is off.
Many improperly set-up cars will run too heavy of a front anti-roll bar, thus the inside front tire will lift. When this happens, usually you need a stiffer rear bar and a lighter front bar so that they are better balanced.


As for the original post, I've read the arguements from both sides of the story. For handling, neutral is said best, for straight line traction, lower to the diff is said best for anti-squat = traction. IMO, a street car should be set to have a very slight angle downward to the back, thus through its range of travel, the angle doesn't get overly aggressive, therefore doesn't induce large amounts of oversteer or understeer. At the same time, the downward angle helps keep the rear from squating a.k.a. lifting the tires off the ground during a launch.More pinion anlge also helps provide more "anti-squat". - The less body roll you allow in the rear, the less likely it is to induce rear steer, no matter the bar angle.
My car worked well with the lca's in the bottom hole, but with my ride height, this made them about -2 degrees, downward to the back. I never noticed any stability problems, even during a few "emergency" swerves(I live in Florida, old farts coming off side roads can kill).

Dewey316

At the same time, I run mine with the axle side just slightly upward (maybe 1* at most), and I have no wheel hop issues at all. sure you can get a bit more anti-squat, but too much anti-squat is bad, and there are other ways to get more A/S, other than the LCA angle. There are trade offs in suspension, once change such as the LCA angle, changes a lot of other things. There is one cause/effect in this stuff. If wheel hop was as easy as one change, without cuasing other poblems, crew chiefs in upper levels of racing wouldn't be making the money they are.

--John

Shagwell

- very well spoken truth.

Duracell Bunny

If that was a stab at me, I am not that high up in the ranks yet . Just Whelen series right now and a labor of love. I crewchief for a Spec truck/Supertruck.
http://www.cardomain.com/member_page...2_148_full.jpg
I get a few bucks here and there but its generally going over the wall on pitstops for a few teams in the Grand National West series as a fuel man. Gotta be tall for that job. Climbing over a wall and stuffing a 65lb can of fuel is not as easy as it looks. It takes height leverage.

Dewey316

Dean, It wasn't a stab at you at all. It was a point that there are a lot of interacting parts in this, it is not as easy as making one change for a cure. There is a reason that guys in F1, Nextel cup, IRL, LeMans, etc. Make some serious money, it is because these are very complex systems with lots of interacting parts. This is why relocation brackets aren't the end-all fix, because it effects so many other things. It was more of a stab at sofaking, as I assume he is not a designer or crew cheif for one of the above mentioned ranks of racing.

Duracell Bunny

I just want you to know I still think of myself as a blue collar reddneck
The worse part is when you have a break down in the system like a tire guy not realizing he has a slow leak in a tire. All the while you've been altering settings and you do not find out till you check the charts and guage it yourself- Then realise for core heat and cooldown speculation what the real problem has been all along. Oh the fun in complexities.

Never trust a new tire guy to do what you ask.

Guest

Based on the photo date and the tires... that car was like that when we did our little ESP day. The LCA's sit *fairly* close to level when the car is down with the springs I have in there.

Global West brackets.

sofakingdom

iTrader: (1)

Mine look about like madmax's (when you can see them); just BARELY angled down, I'd say ½" at the most; kind of on the same order of magnitude as the difference between a full tank of gas and an empty tank; just enough so that when under power (unlike anything one can experience on 6-cyl cars) and the rear of the car tries to squat, the frame end of the LCA DOES NOT go below the rear end end. Doesn't take much. Keep in mind, that the more of an angle that the LCA is at, the LESS the car squats; and past some point, the rear of the car actually will RAISE instead of squatting, when power is applied. That's clearly too much.

There's no "safety" issue involved. That's horse dung. That guy that came up with that makes up plenty more laughably and patently bogus stuff, trying to appear like he knows everything there is to know about suspensions. Like the thing about the tires on the inside corners doing the steering work.... sure, they help; sure, getting them to work better will get the car around the corners faster; sure, race car setup, especially on oval tracks (both dirt and asphalt) consists in getting the inner tires to share as much as possible of the load, with the outer ones; but basic physics tells you the outside tires will be doing the bulk of the work. They're the part that pushes the car toward the center of the radius of the corner, as evidenced by Zepher's simple observation.

Additionally, because the angle affects the tendency of the rear to squat in the first place, when they're properly set, the whole thing is basically NEUTRAL under power, anyway. Meaning, once it's set up right, the amount of power that you have, produces LITTLE OR NO need to angle it any farther. More hooey, there.

Like Shagwell and madmax and about everybody else WITH SOME POWER that has actually USED them ON ONE OF THESE CARS, I'm a satisfied customer.

Duracell Bunny

Sofakingdom, Trying to explain to you where my LCA's are set, their length, the spring rate changes, bunpstop combined forces, and shock damper rates, the roll center and the combined roll couple to the front and what exactly it is all doing when I actually turn under throttle or braking and the car squats and leans would take a novel to try to explain to you and you probably wtill would not grasp it(and that is not a slam to you particularly, It would be hard for 99.9 % of those here to understand.

You would be amazed- Its why my car is so damn fast and Chris (Madmax) and a few other of the locals I think would graciously agree for my behalf.

If it were easy to understand then we all would be doing it.

Yes it is unsafe if set too low. Get in your car and try to follow me do an 80mph 4 lane change phasewarp in about 2 seconds and then brake down hard to stop and lets see how many dounuts you do as you spin past me and hit the accident feild. Your car could not hold a candle to the magnitude of g force my car holds as it remains user friendly. You just will never ever know unless you go for a ride. THis car isn't like any other 3rdgen you have ever driven and its all in the setup and weight bias.

The difference betwwen you and I is you make one change on your car and it is hadly felt- until its too late anyways. You make one change on my car and the slightest change is felt.

Guest

Bah, your car is SLOW.

At the dragstrip.

Too bad we were at the future location of said dragstrip and they had cones there that day instead

Yea, I'm nearly level right now, with the bolt location as shown above. Slightly lower in back.

Duracell Bunny

Thats when I open the stable doors and bring out another car more ment for that purpose

Really though, THats why I never drive my Vette anymore. It is so devastaing there is just no challange- in all venues Autox Dragracing, or road coursing it We even showed it for years and campaigned it in a shoping mall car show circuit here in So Calf with only Corvettes. I've had much more fun stealing my wifes Camaro over the past few years and grudging peolpe with the unexpected, and in part, making it challanging for myself when I shoot my mouth off in an underdog and have to come through.

sofakingdom

iTrader: (1)

You just don't know when you're beat, do you?

"It is better to be thought a fool than to open your mouth and remove all doubt".

The post is about WHEEL HOP. LCARBs are an EXTREMELY effective means of getting rid of it. Used properly, they are safe, don't hurt handling, etc. etc. etc. Get yourself ONE OF THESE CARS (not a Vette) with some POWER, not a 6-cyl, and you'll IMMEDIATELY understand.

The guy didn't ask about g-forces. When he does, I promise I won't suggest LCARBs to improve them. In the meantime, since he asked about WHEEL HOP, it's best (IMO) to stick to THAT topic, and not start the same argument you always start about SOMETHING ELSE.

Dewey316

Still waiting for the science.

Or are you just not going to bring that, since you would rather not remove all doubt about your being a fool?

What do you think controls the unpsrung weight that is actualy hopping?

I am so glad to see that you have such a huge grasp of this TGO only tech that you seem to flaunt so well. Lets try a little exercise. Pull up google. Type in "Wheel Hop" Suspension AND causes.

Look at the FSAE acticles, and various other sources, all of them refrence documents of SHOCK VALVING. Because the rest of the freakin' engineering world understands this. Yes increasing the A/S on this cars can mask over the issue. But it is just that, it is masking the real issue, and causing other problems in the process. Read a F---ing book, read what the Millikens have to say on the subject, and bring your tech.

naf

iTrader: (7)

According to Duracell we wouldn't be able to understand it anyway...

antman89iroc

Ok I'm not going to get into the science nor theory. But I will tell you what has worked for me. 89 IROC 5.7. Sub frame connectors, poly torque arm mount and trans mount, boxed stock lower control arms with stock rubber bushings, new gas shocks, lower control arm relocation brackets, stock springs/stock ride height. My car has absolutly no wheel hop at all when burning tires. Great traction on controlled starts. I set the LCA's so the rear is about 1-1 1/2" below the fronts when parked. When I read your car specs and symptoms it sounded to me like something may be loose or mis alligned. I would suggest double checking everything and adding LCARB's.

Dewey316

I didn't say that. Sofaking however, DID say that he has all the science and theory. And I am still waiting on that. He brought it up. I would have stayed out of this, but when someone claims they are going to bring the tech, they better bring it. I hope that people see by the LACK of him bringing tech, that he really don't know what he is talking about, and DOESN'T have the science to prove his point. You want to know why he hasn't posted this "science and theory" ? Because all of the books on this, and all the data out there for wheel hop, is about shock valving and properly tuning the shocks to control wheel hop.

sofakingdom

iTrader: (1)

What would you like?Springs, shocks, tires; the usual. Same as always in any car situation.No, it's the other way around; the geometry of the suspension causes the FORWARD application of power to attempt to LIFT the rear off the ground; and dinking with the shocks MASKS the "hop" behavior by damping it. But the basic problem - the LCA being angled UPWARDS from the "frame" to the rear end - remains.

Here's a simple, crude pic that shows what happens. Sorry for the crudeness. Science can be crude sometimes.

Blue is the frame, red is bushings, green is the LCA. The right end of the LCA is the rear end, the left end is where it joins the frame. We're looking at the car from the left.

There's a spring pushing down on the rear end, against a part that's connected to the "frame".

Imagine applying power to that system, at the "rear end", like trying to accelerate the car. Obviously, this force will be pushing on the end of that LCA, leftwards. Assume for the moment that the car doesn't move instantly up to whatever speed the force is trying to make it go at (which of course is pretty much real-world); that is, the force is applied, and remains applied.

Now: WHAT IS THAT LCA GOING TO DO?????

It's going to rotate upwards, right?

So, the rear end tries to lift itself off the ground; which sounds ridiculous, because the car is pushing it back down. But, the car can only fall JUST SO FAST; all that's pushing down on it, is gravity. 32 ft / sec / sec. So for some short interval oftime as the car begins to accelerate downwards toward the earth, the rear can manage to lift itself up against the force of the spring, storing energy in the springs, and reducing the normal force on the tires. Well we all know what hapens to a frictional situation when the normal force goes away.... so does the friction. The tires spin. When that happens, the leftward force goes away. When that happens, the rear end isn't trying to lift itself any more. When that happens, the energy stored in the spring, starts pushing the rear end back down. When that happens, the tires bite. When that happens, the spinning stops. When that happens, the leftward force returns. When that happens, the rear end tries to rotate itself upwards. And so forth.... about 7 times a second, in one of these cars.

Where did "shock valving" come into play ANYWHERE in that description of the ACTUAL behavior at hand? It didn't, sis it? All that it will do, is to attempt to stabilize the faulty geometry, against the forces improperly applied to everything.

Instead of fixing the SYMPTOM, LCARBs fix THE PROBLEM. All they do, is restore the geometry to WHERE IT SHOULD BE IN THE FIRST PLACE: i.e., with the LCA LEVEL instead of angled upwards toward the rear end. With the LCA level when power is applied, there is no longer an upward-rotating tendency, and the whole "hop" behavior cycle is eliminated. A very slight downward angle, AT MOST, is all that's required to stabilize the suspension; and then, you get to valve the shocks for other MORE USEFUL purposes, like handling or cornering or ride quality or whatever, instead of band-aiding this other problem.

This is why lowered cars do this so much worse even than stock height ones; although, as anybody who drove these cars OFF THE SHOWROOM FLOOR would know, they did this from the day they were built. Some of us don't need "books" and Google to KNOW THAT, because WE WERE THERE; or to tell us why it does it, because WE ARE WILLING TO LOOK AND THINK FOR OURSELVES.

Dewey316

Quote: From Collegiate Design Series Suspension 101, Steve Lyman DiamlerChrystler Corp.

Rear Suspension
Ride steer / roll steer:

independent
small toe in in jounce preferred
consider toe in in both jounce and rebound
gives toe in with roll and with load
toe in on braking when the rear rises

beam
increasing roll understeer with load desired
10 percent roll understeer loaded is enough
roll oversteer at light load hurts directional stability

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My input:

Note, this is rear suspension design, from a pro. Note roll understeer is to be designed in. Keep this in mind, because we are talking about ideal suspension, and "flaws" in GM's design.

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Quote: From above author. on dampers

Primary function: dampen the sprung and unsprung motions of the vehicle, through the dissipation of energy.

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Definition:
WHEEL HOP FREQUENCY OR UNSPRUNG MASS RESONANT FREQUENCY - The wheel hop frequency is the resonant frequency of the unsprung mass relative to the suspension tester platform.

At the resonant frequency of the unsprung mass (wheel hop resonance frequency) the displacement between the unsprung mass and the suspension tester platform is a maximum, or adhesion is minimum. Wheel hop resonance usually occurs between 10 - 20 Hertz, and can be seen graphically as the minimum inflection point on the adhesion verse's frequency graph.



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Quote: Anatoly Tsymberov, Hunter Engineering Company.

"At wheel hop resonant frequency, increasing damping reduces wheel displacement and increases phase angle."

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Now, I agree, that the instant center location does effect this. But, there are other effects, and other things happening. Even with an exteme amount of anti-squat dialed in, without dampers it will still hop. PERIOD. Go unbolt your shocks, and then go do a burn-out. Tell me what it does.

naf

iTrader: (7)

Sofa says LCARB's can be used to correct improper LCA angle and Dean apparently uses them on his car as well. From his CarDomain site:

"BMR bolt-on relocation brackets (I welded them into place) Why bolt-ons? They have a secondary support brace that the weld-on styles don't- strengthens the shock mount for a future coilover rear conversion. I was thinking ahead, but don't now think I'll ever bother doing it."

Dean uses them (I assume) to correct improper angle after lowering. Sofa claims the stock angle needs correction. What are we arguing about?

Unless my assumptions are incorrect????

Guest

Thats a stupid argument. Go put in a LCARB to fix the geometry without changing the shocks, do a burnout, and tell me what it does.

Dewey316

Not it is not. Because I have pointed out, that my LCA's sit the way that you are saying is bad, and I have no wheel hop. But, take the proper damping out, and I promise you the car will hop.

I am not joking about my above mentioned google search. Search it out, look up wheel hop frequency and sprung vs unsprung frenquencies, and look and damper dyno graphs and the corilation with damper valving. I posted quotes from people who design this stuff for a living (hint: google search their papers and read them), if I was someone just reading that, I would take the information from the pro's over some guys MSPaint diagram any day.

Guest

So mount your LCA 3" above the axle and see how your car does then.

sofakingdom

iTrader: (1)

Madmax is right; that's a stupid argument. Actually thius whole thing is a stupid argument, I'm sorry I even got dragged into it. I should know better by now than to take the Dean bait.

You can't take a general statement like that one about "bump steer", and assume that it applies equally and identicaly in all cases. It assumes that the REST of the suspension is already correct. Worrying about "roll steer" on a drag-raced car (or for that matter, 99.9999% of all street cars) while the rear end is busy trying to hop itself out of the chassis, is a waste of time. You might just as well go adjust the idle mixture on a motor with a knocking rod.

I'm pretty damn stupid; but I've learned a few things over the course of my assignment to this planet.

If you have little volunteer plants coming up in your yard, you can mow them all you want; they'll come back. If you want to stop them, you kill the roots.

If you're putting out a fire, you don't shoot your fire extinguisher at the flames; you shoot it below the flames, where you can't see. That's where the burning thing is. You can't make the flames go away, except by putting out the fire at its source.

If people keep falling off a cliff and getting killed, you don't put an ambulance (or a hearse) at the bottom of the cliff. You put a fence at the top.

If you're walking down the street and you see an old lady laying there looking pale and gray, you don't put makeup on her so she's not so pale and gray any more. You give her CPR so she doesn't die.

In other words, no matter what problem you're trying to solve, you DON'T try to attack it by solving the symptom. You go looking for the UNDERLYING CAUSE, and fix that. The symptom will then go away all by itself.

If you have wheel hop, you fix it by restoring the geometry of the rear suspension in such a way that the forces applied by it don't try to hop the wheels. Once you've got it as good as it can get that way, THEN AND ONLY THEN you go to work on it with shocks and such.

You FIX THE WHEEL HOP PROBLEM with LCARBs. Once you minimize it that way, the shocks and whatever else have a much easier time dealing with the last little residue of it.

Or at least, those of us who want something quick, cheap, maintenance-free, and applied at the SOURCE of the problem instead of at the SYMPTOM, do it that way.

Duracell Bunny

My posting started out by basically saying do not use the LCARB's to drop the rear of the lca downward more than slightly.

I never said LCARB's are bad- I even stated I have them on my car.

I see it time and time again where people simply weld on LCARB's and immediately just put the rear mount into the lowest position trying the get the steepest downward angle possible "thinking more is better"

Thats what this whole topic and my contribution was about.

Edit: Oh yeah, and John is correct in saying Dampers have alot to do with it. Sofa, if your car example had better dampers, the LCA's would not travel into that steep angl;e to be a problem. The dampers would control the rate of inversion and disallow it to progress that far inverted.

And as for Sofa? Remember, you called me out in this post saying I have blind spots in my logic.

Dewey316

Sofa, I am here because you said you had science and theory for this. So far all I have seen, is a mspaint drawing, and then what YOU think is going on. All I am asking is that you bring the tech. I posted quotes from two reliable sources taking about this. You have so far brought nothing to the table.

Think about this. Why is it that when wheel hop is discussed, the first things brought up, are worn bushings? Why would those effect this if it was purley a geometry issue? The reason is, that as the bushings wear out, the the frequency of the sprung mass changes. AHHH HAH! Maybe there I am not so crazy after all. Why don't you go ahead a provide some sort of data or study, or equation that shows how the instant centers location actualy effects brake hop. I can sure post equations that show the changes in frequency will effect wheel hop.

Once again, I will quote someone else.

---------------------------------

Wheelhop is the unsprung mass of the suspension oscillating against the spring forces (compliances) involved. If there isn't enough damping in the system, wheelhop will occur.

If you install bushings with more radial stiffness, the resonant frequency of the unsprung mass will go way up which will reduce the amount of energy that the sprung mass resonant frequency will couple to it. This will reduce the likelyhood of wheelhop a lot.

Jack Hidley
Maximum Motorsports

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Keep posting your drawings sofaking, they always make me smile. But I am going to come back with quote after quote from qualified people talking about dampers when they talk about wheel hop.

--John