I have a set of those that I'll put on the car some day.

 

I tend to agree with you. If we look at the wins at the Solo National Finals in my class(CP) I think Strut cars have won 7 out of the last 10 but I only think 1 of those was a third gen camaro, the rest where in Mustangs. The other 3 wins where with cars that have fully scienced out SLA suspensions. Not bad in a class that is supposed to be full on race cars and is really a testiment as to how well strut cars can actually work.

 

Can't open it. Win Vista says the compressed folder is invalid.


Norm

 

Welcome to the party Big, I cant validate your chart but it is impressive.

I noticed though a "problem" with the camber curve's on the chart though that is typical of a strut. It's most obvious on the "lowered 2" curve, at about 2 1/2" compression the curve essentialy flattens out. Thats where the inside edge of the out side tire begins to lift and cost traction.

The rebound curve wich will be effecting the inboard tire is better but since the load is concentrated on the out side tire camber under compression is whats most important.

the adjustable balljoints in the links should help out because with a significantly lower car (2+ inches) the stock balljoint is definitely stealing camber at 2 1/2" compression.

I also agree that the F body package is really very good. Thats why I'm not going extreme with this project. I'd proabably be the only one to use it and my car is definitely not going to be a full on race car.


Last year i was asked on a Mazda forum if a Mazda MX-3 could be made competitive in national solo racing and I responded that the car is very well engeneered light weight and nimble and it's a great platform to start with.

Another member chimed in and said that NO strut car could EVER compete with a double wish bone Honda. I feel that is complete ignorance, though the class the OP was interested in was proabably 90% Honda and he would be a true underdog for many reasons ( and many seasons the truth is that if you only placed 5th you still beat a dozen or more of the supposedly un-touchable Hondas out there.

1st and second gen RX7's are proven winners with struts as well as the smaller BMW's and 924/944 Porsches among others.


It's also worth noting that the "ideal" camber curve can change due to many factors, mostly roll resistance and tire dimentions and construction.

Wider tires and lower profile tires each are more sensitive to too much or too little camber. If you have camber issues and you cant do any radical suspension work and dont want to give up tread width you can try stepping up your sidewall a bit and/or use a tire with a less rigid sidewall.

The extra compliance can help keep tread on the ground and inprove overall traction.

I know the AutoX mentality is to have the shortest stiffest sidewall possible for better response and I dont want to start an arguement (again) but response issues can be resolved with the driver tweaking his style a bit.

 

That’s exactly why I put in the "raised 1" curve. That would be stock ride height with a 1" drop on the mono ball joint. Or for example, "lowered 1" could be a 2" drop with 1" from the suspension and 1" from the mono ball joint.

 

Was wondering about that! I just figured you were grtting into rallyX lol.

But a1" lift isnt the same as a 1" baljoint drop, it adds in the effect of the strut starting in a different position where the uniball on a stock ride height carwould have a slightly inverse effect on the curve.

 

No, the strut would compressed 1" shorter. The pivot points remain in the same spots (BJ, strut bearing in shock tower, and LCA pivots) so the geometry remains the same.

 

But you need to realise that raising the car 1" extents the strut by 1", as you can see in your own chart the camber changes with bith compression and droop.

The strut ads it's own peculiar aspect to the camber curve so any change in it's static state will effect the static camber and the entire curve, just the movement of the balljoint dose not change the position of the strut or it's movement at all where as a 1" raise would have the same effect on the balljoint position in addition to the change in the strut position and geometry.


You could thereticaly re set the alignement using basic alignment tools but unless you took that into consideration with your model then the 1" raised curve is invalid as anything other than a refference. But as it is ats a great tool for observing the effects ofa wide range of motions being imparted to the suspension.

 

No, the pivots define the camber curve.

 

Ok, I think might see where there is some confusion.

I assumed that the alignment was always set to -.5 deg at ride height for each curve. You could change this to 0, -1.5, or whatever you want. It would effect the camber curve a little bit, but I had to baseline it somehow. I did this because I was trying to look at it from the point of view that the suspension will spend most of its time at static camber and bumps and body roll with cause it to move up and down from there.

The way you are looking at it you could just look at the stock curve and ignore the rest. If you lower the car 1” using springs and do not touch the alignment your static camber would be about -1.25 deg, for example.

 

I see, so each curve was plotted from the same base camber setting regardless of static ride height.

 

https://www.thirdgen.org/forums/fabr...gine-shot.html


Check it out This is pretty much what we were talking about rayar.

 

Thanks - that was a Lot of info - I'm glad you noticed that post with that dumb title

anyway -

using the 2D design software I had to lower the lower control pivot point about 1.5 inches to get good camber curves and consistent roll center height (about 4 inches above ground)

for antidive the frame is already angled upwardly toward the front where I mounted the upper arms - it can be calculated and shock settings, weight and other things have an affect on it - so I went with the frame angle

I set caster to 10 degrees - now theres slightly more space ahead of the tire than behind looking at the fender

I couldn't weld a caliper bracket to the B-body spindles I started with so I used the
C4s which changed my design with respecgt to the vehicle height and tire size because of the change in the upper and lower ball joints and spindle center line spacing

Last thing my tie rod are at kinda of a large angle - seems ok so far - but the Type 2 PW pump, under drive pulleys and those 275/35/18 makes it tough to steer

I'll post the 2D lay out I settled on and camber curves fyi

 

That exactly what I was talking about but I would probably still use the factory spring pocket and an externally mounted shock(since I have a weight jack in the way) like we used to do on our dirt track cars. Coilovers like on Mell's car also look like a good option and if I did that then I would run them from the Lower A-arm through the upper arm up to mounts on the cage. It would mean a lot of redisign on my part to go coilovers for very little if any improvement. The only reason I would have used G-body spindle is I still have stock brakes so it would be a bolt on deal and they work fine for autocross. Going with the Vette parts would make it easy to go with the vette brakes so that looks like a real good option.

 

The roll center calculator is what I used - the link shows the suspension layout

http://performancetrends.com/rc.htm


Right Height Left Height
A 24 20.5 UBJ 24 20.5 G
B 17 19.75 UFP 17 19.75 H
C 28.37 7 LBJ 28.37 7 I
D 11.65 7 LFP 11.65 7 J
E 21.5 18.75 USP 21.5 18.75 K
F 25.37 7 LSP 25.37 7 L

right and left distances are from the car center line – lower frame pivot (LFP) is the difference between the front the rear bushing distance from the centerline since they are not equidistant from the centerline

Upper arm dimension calculated
Length 7.04 – angle 6.12

Lower arm dimension calculated
Length 16.81 – angle 0

C4 spindle info:
Hub distance 3.75 - horizontal distance between the center of the lower ball joint to the wheel mounting surface
5.875 in distance between upper ball joint and center of the rotor
7.5 in distance between lower ball joint and center of the rotor
Spindle angle 16 deg

Track 60.7
Scrub radius -.3
Roll center height 1.6

Camber gain -.59deg at 1 in dive; -1.01deg at 1.5 in; -1.5 deg at 2 in

Roll camber change shows the loaded tire losing camber at 0 degrees dive
.74 deg at 1 deg roll; 1.41 at 2 deg; 2 at 3 deg

and the unloaded tire gaining camber at 0 degrees dive
-.82 deg at 1 deg roll; -1.72 deg at 2 deg; -2.7 deg at 3deg

Static camber is 1deg

That software was helpful ($80 back in 2003) since I didnt intend to keep any stock susp parts-
hth

 

not that it really matters to you guys, but looking around. i found that the 5th has gone back to no upper control arm. i found that odd




some pics, and there's a link to a pdf file of what looks like the hardest coil over kit ever! lol

http://www.camaro5.com/forums/showthread.php?p=999477

 

oh and finally found a pic of a 4th front end.
i was wandering around a junkyard and looking at one while thinking about this thread. the 4th gen upper arm, just bolts to the strut mount and uses the long upper ball joint mount. since most of us, or atleast me. have conveted to 4th gen front brakes anyways, wouldn't finding a way make an upper tie into the bottom of the strut mount like the 4th gens, and use their spindle be a pretty easy/good idea? it would also make swapping to a steering rack easier.







or does this type of upper a arm being so far up there, have some camber side effects that make it not worth while?

 

Well by my reconing if everything is the same raising the upper arm reduces camber gain for a given compression, that means that the upper arm either needs to be shorter or have a steeper angle at static ride height to compensate.

I also believe that having the arms so far apart reduces slop in the suspension due to bushing and arm deflection compared to a traditional setup without resorting to harder bushings or more rigid and thus expensive to manufacture control arms.


As far as instaling the 4th gen spindle with upper arm the main problem I encountered was 1 the upper ball joint and the related areas of the suspension would hit the underside of the stock 3rd gen strut tower, you can see where the 4th gen tower is formed to allow the suspension to clear the structure. This is evident on many other cars as well like SLA Hondas and Mitsubishis/Chryslers.

A rack or a custom set of steering links would be needed also since the 4th gen spindles have shorter steering arms and would introduce a host of bump steer and roll steer issues.

For someone willing to cut up their car it wouldnt be the most dificult job though.

I'm on my way to a basic prototype setup as we speak It'll look almost production btw so dont get freaked if I post pics of a 16 ga sheet metal origami looking thing!

Since I have constrained my self to the space available I'll have to build it to fit first then go about insuring improved geometry and such.

I suspect I'll have to resort to lowering the LCA like Mell did in order to control the wild camber gain I might be looking at, if I'm lucky I can do this with off set bushings like are available for my Mazda.


The 5th gen was almost an after thought and is based on an Australian family sedan, just like the 1st and 2nd gens and even the 3rd gen to an extent the 5th gen is based on current conventional technology.

Designing a whole new front end just for the F body would have the car priced nearer the Vette and Viper except it would still have a family sedan's fairly basic IRS compared to the expensive space consuming and very effective rear ends used in those cars. on the back burner is a plan to swap the rear from a final gen GTO (or Caddy Cattera) into a 3rd or 4th gen to compliment the SLA front.

 

Sounds about right. These tweaks also affect lateral tire scrub as well (Marks' "Standard Handbook for Mechanical Engineers" even has a sketch and brief discussion about this specific item).


Loads applied to the basic chassis structure also tend to go down with a tall knuckle design. On the other hand, deflection in the knuckle itself tends to increase and clearance issues around the top of the tire may limit the wheel sizing in some ways. Seems like there's always going to be a little give-and-take.


Norm

 

The scrub radius is unaffected by the upper arm, the only things that dictate scrub radius are kingpin inclination (steering axis angle), wheel diameter and offset w a given size hub and spindle snout. Basically it's the result of where the kingpin axis intersects ground level and where the wheel centerline intersects ground level. The distance between the 2 is the scrub radius.

 

I'm talking about lateral tire scrub as the suspension moves through its travel. Not the same thing.


Norm

 

Oh OK, mistread my bad.

That lateral tire scrub is almost completely the result of the effective horizontal lower control arm component changing length when the arm swings around. It's obviously longest when the arm is horizontal from bushing centerline to balljoint center. A longer lower control arm will have less change here. Longer lower control arm = less balljoint angularity.

 

Fabbing a longer LCA has been on my mind but I have been trying to avoid that for cast reasons, especialy since the suspension will retain the stock spring location and proabably use a shock in the same location. The LCA would need to be quite strong and resistant to fatigue.

What many people dont realise is that while the tubular components they can buy from various vendors are stiffer and lighter than the OE stamped parts they replace the fatigue life of many of those components may not be near what you see in the OE stampings. For all their flexability they are usualy very resiliant and rigid tubular replacements will tend to crack and fail outright rather than bend.

For a coil over car like my mazda i wouldnt have any problem fabbing a light tubular piece as there is little bending pressure being applied but for our style suspensions a lot of attention needs to be paid to how the stresses imposed by the spring and or shock are handeled.

 

The bending force entirely depends on where your coilover or our spring is mounted, not familiar with your mazda but if the coil over is mounted close to the balljoint for a closer spring/shock to wheel ratio relationship then yes,that would be true.

 

It's a typical coil over strut design. The only bending force being applied to the arm verticaly is from the swaybar.

 

Noobe question.....

Why not use something like this


And mount it in the frame rails like this ? The spring and shock look preety short so maybe will miss the Upper strut mounts. Some sheet metal needs to be taken away. if geometry is right...is the 3rd gen frame rails in that area strong enough to take the stress?

 

Thread brought back from the dead but I haven't been able to stop thinking about it so that is good.

That shows pretty much what we are talking about but for me I am talking about optimizing the front suspension and I don't believe that can be done with an off the shelf kit.

My main drawback I had is trying to retain the 5X4.75 bolt pattern and stock brakes, Other then parts availability I am not real sure why I want to do that. Now I have started thinking about either a wide five or the 5X5 stockcar style spindle and that really opens up options as far as how tall the spindle is as I am starting to think that any OEM spindle will be too short.

Even though I haven't purchased anything yet I have been able to locate all of the needed parts, A-arms(of different lengths), spindles, hubs and even rotors and calipers for under $300.00 total. The spindles I found are wide 5 spindles and are 9 inches tall. Does anyone happen to know the height of a G-body spindle? I guess I will just need to get a computer program or start making a scale model and see what I come up with

 

And as far as my goals that setup would require cutting away the lower strut tower and a lot of bracing of the lower frame horns.

If you look at the second picture you'll see the crossmember going from one side to the other, that is pretty much the boltin X member in our cars. The froe/aft frame members in the pic would be the lower frame horns in our cars.

The horns are rather light sheetmetal box sections integrated with the rest of the unibody, alone they are not strong enough to suppoer the load that will be acting on the upper arm brackets that would need to be welded or attached in that area.

The horns are further weakened by cutting away the strut tower sheetmetal, btw there would be no reason to keep the rest of the towers since they would serve no purpose other than to keep dust and road grime out of the engine bay.

It's a project that would take an amature a long time and a lot of expensive tools to perform. It would be nearly 100% irreversable where my concept is for an easily bolted in (and un-bolted in) system that anyone with a few hand tools and some jackstands could do.

 

G-body spindle is 7.5" outside measurements (top of upper balljoint ear to bottom of lower ball joint ear).

The center of the UBJ looks like it's about 1.25" above the top of the upper ear (what's left of my UBJ is too badly damaged to tell any closer). Note that there are taller then OE ball joints that you can use to effectifely make the knuckle taller anyway - Mark Savitske's www.scandc.com is one source that I know of specifically for the G-body.

I don't have a lower ball joint to even guess at its effective length.

Sometimes keeping a 'retired auto parts' museum pays off . . .


Norm

 

My plans(and rule book) require keeping the original K member so everything would be built off of the original k member. The front unibody frame horns(Firewall forward) would serve no usefull purpose and would likely be removed. I would build brackets off of the K member for the steering box and sway bar, very likely go with a 3 piece sway bar. I think I would move the radiator to the back of the car. I would need to run larger bars from the roll cage to brace the front better since it won't have the original frame horns to bolt it to and add a few tabs to bolt the fenders to. essentially from the K member back the car would end up being a tube framed car but the K member would also be so heavily modified that it wouldn't resemble a factory part much. Just keeping the front K member should keep me from needing to take the 10% weight penalty for tubed framed cars.

Thanks for the measurments Norm

 

Out of curiosity - exactly what rule book (and/or class)?


Norm

 

SCCA autocross C prepared.
Allthough by reading the rules again this might screw my idea.

D. Replacement of any chassis component (e.g. subframe) in its
entirety by one of alternate construction, unless specifically
permitted, shall result in the vehicle being “in excess” of these
rules and weight penalties and/or competitive adjustments may

apply.

Now I could remove the strut towers and inner fenders completly, notch the front subframe for upper a arm clearance and use a hole saw to swiss cheese the front subframe and still be legal. Sure would be easier just to remove everything in front of the firewall.

On the other hand I wouldn't be replacing the subframe in it entirety. All of the stock subframe from the firewall back would still be intact. Plus the suspension would still be attatched to the factory K-member. It would sure be easier to do something like this to a 2nd gen rather then a 3rd gen

I do know of one Fox bodied Mustang that did exactly what I am talking about and ran that way for years without protest. There is also a 1970 Mustang that I might have mentioned earlier in this thread that was IMHO a full tube framed car. The firewall and floor boards where cut out from Rocker panel to rocker panel and replaced with fabricated parts. The frame was welded to the rockers. I know he still had parts of the original front subframe(That IMHO where only there to satisfy the rules) but from the firewall back it was 100 % tube framed. I wish there was still a website of its build because that is where I got the idea to do the same to my car.

 

"Replaced in its entirety" is probably the key - maybe as long as there's enough of the OE structure remaining to allow the car to drive at least gently without collapsing, it's still not quite into "in excess" status. I hope that's not too generous of an interpretation. Then again, you can always ask the SCCA. Probably start at seb@scca.com .

One guy whose opinion counts for a lot more than mine is Dave W. I think he's been on or is on the Prepared Action Committee. I know you can find him over on SCCAForums.com and I think also on Corral.net and/or corner-carvers.


Norm

 

I am a member of the CP e-mail list and Dave W. has allways given straight forward answears to my questions. His and Gene Baird's advice have been the biggest help in getting my car from DFL to a fairly consistent top 10 overall(sometimes top 5) car at our local events. In fact everyone on the e-mail list has been very helpfull. Still have a long ways to go as I have a feeling I would be very close to DFL if I ever make it to nationals but I probably have one of the lowest budget cars in CP so I guess I really can't complain. This last year ended up being a struggle though as I made some fairly big changes that just didn't work.

 

I'm touched! Wow. You're never done with a CP car, even if you're head of the class. Everyone continues to raise the bar. It's the big hole in the garage you dump money into! I'm afraid we'd finish well back in the class if we went to Nationals right now, though, as everyone is running around raising the bar all the time.

While I think you can still do well in a class like SCCA C Prepared solo with a 3rd Gen front strut setup, this SLA work intrigues me. It would be cool to see something that improves the front geometry while also pulling weight off the nose that's fairly easy to install. Interesting thread.

Gene Beaird,
Pearland, Texas

 

Well Gene, It was a few years back but I was struggling with a car that I was about ready to give up on. Both you and Dave replied very quick with advice that worked. The next year I was mid pack the year after I finally started getting consistent top 5's(And 5th in overall region points) this year I tried some of my own ideas and went back to mid pack finishes. If I am racing next season I am going to take a step back again and just try to improve on that setup.

 

Turbo, says the cheapest way to go fast is with a strut 3rd gen F-body. If anyone should know it is him.

I am also intrigued with the thought of a SLA. With a little searching the parts can be found cheap. Like I said $300 could get me all the parts needed to do this including wide five Spindles(9 inch tall), Hubs, rotors calipers and Upper a-arms and mounts. I would reuse the factory lower arms. Of course then I would need to buy a wide 5 rearend and new wheels so it is not that cheap anymore. Maybe if I found some 5X5 spindles the 5X4.75 hubs that are made for the floater rear axles would work. Not sure but it would save me from needing to buy new wheels right away.

 

Turbo's been going plenty fast in a 2nd Gen lately. The Turd has been having problems staying in one piece, but yes, it's a rocketship when it does run. I wished he'd get it back together and running again, it's awesome to hear the turbo spool up on launch.

I'd be careful of wide-five stuff if you don't already have hubs and wheels. They've gotten expen$ive in the last few years. Used to, it was the cheap way to go, but the vendors seem to think everyone who races has deep pockets.

Gene Beaird,
Pearland, Texas

 

Even staying with 5X4.75 or 5X5, Lightweight aluminum wheels are very expensive. I really want CCW's but at $2400 for a set they are out of my price range. Real racing wheel are still $1600 so still very expensive. I wasen't able to find any other options in the 16X12 wheels. My steel Diamond racing wheels set me back less then $400 and are actually fairly light. Like I said I found all the parts in wide 5, Hubs to a-arms, for under $300. Wheels would end up being a big expense but I am sure I could still find them for $1600 for a set so wheel price is actually a wash.