JoeSmo88

Anyone running one or know anything about them. it looks like a nice piece, if not how about race craft was also looking into there k members, especailly the road race version. any input would be helpful
http://americanracecomponents.com/82...t-kme8292.html
http://www.racecraft.com/index.php?m...dex&cPath=7_16

Guest

Aftermarket Kmembers are a waste of money unless you are looking for a lightweight nosed drag car. There is absolutely nothing wrong with the factory kmemer. Loosing 40 lbs or whatever off the chassis weight is not desireable down low when it comes to sprung weight reduction. You are lessening your sprung to unsprung weight ratio which lessens your ride quality, you are weakening your chassis with those less bulky kmembers and risking impact damgae from road debris (That factory unit is large for that particular reason) you are lightening your pocketbook with money that could be better spent in life, AND lastly these kmembers do nothing different to factory geometry.

So I ask everyone, not just you...WHY?

The stock one works perfect.

Now for a show car to be different? Yes I guess. I just never understood why people buy and build cars they do not drive. a car is designed to drive...drive it. Show cars are a waste of time and money in my book- but I am a minority on that subject. I think its for people inadequate to drive. Gives them something to boast about haow fast there car is BUT."I can't drive that, its a show car" -and they hide behind that statement because they can't drive.God forbid the tires ever touch asphalt...just plain stupid.

1MeanZ

iTrader: (9)

Dean I couldn't agree more. I wonder the exact same thing every time someone brings this up. Unless it's a max effort drag car, it is a waste of money. The other thing that I worry about is what happens if, God forbid, you get in an accident on the street? The car was designed with the stock K-member in mind, when that is replaced with toothpicks, what happens in a wreck? I wonder the same thing about the tubular front lower control arms. I've seen problems with them breaking which could lead to a huge catastrophe. The stock pieces aren't pretty, but they are STRONG which is a must for a street car or a car built to handle. I think too often we forget the amount of engineering that goes into stock parts so we can have the latest shiny parts out of someone's catalog.

87350IROC

iTrader: (2)

While I generally agree with you guys, the tubular K makes working on the underside of the engine really, really easy. Off the top of my head, I can think of the following operations that are easier:

spark plugs
oil pan
motor mounts
integrated tow hook

I would imagine it would also improve custom exhaust and turbo pipe options.

I have had no trouble with mine so far on the street or for track days. However my car doesn't necessarily test the rigors of daily driving.

1MeanZ

iTrader: (9)

Different strokes for different folks. IMO, none of the beneifts you listed would justify a reduction in chassis rigidity, reduction in crash safety, or especially the reduced life due to cyclic loading of the weld joints. The function and durability of the car comes before spark plug access in my book...

87350IROC

iTrader: (2)

For sure. However I have seen zero PROOF that any of the negatives you mentioned are actually true or significant. Regarding crash safety, you could make similar arguments for many modifications, (parts being too strong or too weak). I have always wondered how a 3 point strut tower brace would affect the front crumple zone. At least with a k-member, the strength is really side to side, not front to back, so I don't think it would have much effect on the front crumple zone. Most of the stronger rear suspension parts probably negatively effect the rear crumple zone. Not sure on this, I don't work in the automotive industry. In my industry we build products that are not designed to crash, and when they do its never graceful.

Maybe one day when I'm bored I'll model the two and test in my stress software.

1MeanZ

iTrader: (9)

I've seen pictures and read accounts of road race guys breaking tubular A-arms and having issues with tubular crossmembers. I'll have to dig up some links...

Here is a post on frrax talking about the 4th gen UMI K-member. These guys like it....
http://www.frrax.com/rrforum/index.p...tubular+member

here are control arm issues:
http://www.frrax.com/rrforum/index.p...&hl=arms&st=20

http://www.frrax.com/rrforum/index.p...tubular+member

http://www.frrax.com/rrforum/index.p...hl=BMR+bending

paul_huryk

I'm not sure of the differences between the stock K member and aftermarket tubular ones, but based on the control arms, TQ arm, and other suspension items made of sheet metal, you can bet the factory one is made that way based purely on cost.

That being said, I do think if you are going to go for a decent drag race or road race effort, it is probably worth the effort and cost. I would love to shop another 30 or 40lbs off my front end and get more space around the engine for a larger oil pan or headers. Don't forget the third gen V8s are all front heavy and taking off 20lbs here or 40lbs there adds up. I would never do any sort of LS1 car without an aftermarket K-member, even if the stock one could be reused.

87350IROC

iTrader: (2)

I know I have heard of one case of A-Arms breaking. But they were some pretty poor looking a-arms to begin with. I am interested to see what you find.

1MeanZ

iTrader: (9)

above is about all I found. I did find where a guy broke a PA Racing k-member but he just welded it up and fixed it.

Again, note that these are 4th gen units. Not seen anyone with a tubular unit on a thridgen road racing it. Much of the community seems a bit divided on the issue, but failures seem to be rare as well. I can't bash a tubular k-member based on the evidence I've provided, but they still make me uneasy. thats just my $.02

There is a whole other world of cars running tubular k-members that I did not sample (mustangs) so maybe they would be a better group to sample for tubular k-member failures during RR or AX use.

Maybe Dean will blast in here in a blaze of glory like he sometimes does and give us more info... :-)

87350IROC

iTrader: (2)

Thanks for the links.

That UMI 4th gen upper a-arm is a really horrible design. I think some of the concerns of the lower a-arms are addressed by Spohn's design. They use a really long threaded end, there must be at least an inch of thread engagement. Also the arm is stiffened by the spring perch.

We'll see how they hold up.

My k-member and a-arms have about 100 track miles and 1000 street miles on them so far. So far so good.

jharrison5

For me tubular is the way to go the stamped pieces are too heavy and outdated. If the tubular parts are made of quality materials and welded properly they will out perform the stock parts any day.

Guest

All I know is what I have experienced in life....

...I have taken several good hits on the kmember on every car I have owned with one. My truck for one has marks on it that I guarantee if it were tubular it would have been destroyed.

I hit something one night in the Camaro on the 57 fwy so hard I have no idea what it was. It ripped my y-pipe in half and guoged the floorboard. It also wiped out the airdam and the radiator deflector, but the kmember was fine. I think it was a big rig tire retread, but I will tell you it did some major damage to the exhaust tubing like you can not believe.

My truck A-arms are aftermarket but I have gusseted and weldel them with alot of reinfocrment after I had that experience of a control arm breaking on me and almost killing me. My truck A-arms are very beefy compared to any 3rd gen arms- yet they still make me nervous. I just need them for the geometry I can not get with the stock truck arms.

If my life goes as planned in the next year I amy have to eat crow becasue I have on heck of an idea that may constitute a front end geometry that will not be friendly to factory stamped a-arms... thats all I wil say- but the kmember will be a factory unit with a few little modifications...

articwhiteZ

iTrader: (56)

i can say from what i know. and have put on my Z28. is the Tube K member was the way to go.. its a drag car show car. that i dont drive like the Dukes of Hazzard. or in the rain. it shaved Lbs off the car. and made alot more room. and have had no probs with install or up keep. but then i keep an eye on all my parts and up keep.. coming in 2nd at a car show. in your class.. is the first looser...it's no fun

ihatemustangs

iTrader: (3)

To each is own, but I have used them in many different cars and tey are great for a street/strip car. The room and ease of all the space is great, as well as the wieght loss. But for those questioning structural rigidity, a buddy hit a car ( he t-boned it when they ran a stop sign) with his 91 z28 with a UMI K member, and it didn't crack, but , flex, a stock frame wouldn't have done much more to help. Most companies recommend running road race style k members in street cars. They are braced alot more to be stronger than the drag setups. Just my .02

87350IROC

iTrader: (2)

LOL UMI doesn't make a K-member for third gens.

ihatemustangs

iTrader: (3)

HAHA DUH! Must have been Spohn. We only use UMI stuuf in our 4th gens.. My bad

Guest

Here's a copy of some info I wrote on another thread. I will copy and paste it here where it is under the kmember topic- far better useful info for this thread:

{...people need to realize that one little change like this where someone things they are gaining track width so they are always gaining grip is so wrong. THe sus[pension could be balanced and one little change like this changes geometry and leverage and can potentially cause the entire suspension to be readjusted and rates changed to make something go from good to soso , then alot of readjustment and other parts changing to go to the actual 'better'. It does not just always go from good to better.

Start messing with this stuff and you had better know what you are doing otherwise 99% of the time you are hurting and not helping.

Let me give an example of something in recent topics here on TGO.
Alot of talk has been on aftermarket Kmembers and their usefullness. Are they worth it? and main talk is are they strong enough. Thats only half of it. the weight savings which everybody thinks is great is actually terrible.

Why? How can loosing weight be terrible?

Well, you are loosing weight in the wrong place unless you car nothing about cornering (THUS WHY I SAY AFTERMARKET KMEMBERS ARE GREAT FOR DRAG CARS ONLY)

Why is it the wrong place? afterall it looses weight off the heavier front half of the car making a better 50/50.....YES this is true, but the evil outweighs the benefit.

You are loosing lower lateral weight. You are better off loosing upper lateral weight in the hood, aluminum heads, battery box relocation, windsheild glass, aluminum bumpers, plastic headlights, lexan hatch glass....all mid level to upper level roll weight.

Here is the explination so you get the big picture. Cars have a 'center of gravity' or 'cg' as we will refer. They have a fore and aft cg, they have a vertical cg, they have a lateral cg. You need to think of the chassis as for what it is...3 dimensional. So now we look at what is body roll and how does weight affect it? Well body roll is about the imaginary 'roll axis'. The lateral cg is what influences roll based on its verticval osition to the roll axis. The higher off the ground the roll weight is (measured off the ground since the ground ultimately is where the grip is from the tire contact patches) the more the leverage or polar motion of the weight. these contact patches connect through the suspension and gewometrically determine where the imaginary roll axis is that the weight moves laterally over or under. Weight and leverage over this imaginay line causes roll of the body, weight under this imaginay line causes ANTiroll of the body. Roll is positive, anti roll is negative.

Now, a typical thirdgen has a very positive roll weight- hence why we need preety big sway bars like the 36mm up front to control that positive roll weight. Older cars like 70 chevelles need even larger bars because they have even heavier positive roll weight that needs to be controlled.

Starting to understand what swaybars do and how size is determined? yep I hope.

So back to that kmember we just replaced with an aftermarker tubular unit that is something like 50lbs lighter. That Kmember is low. Laterally most if not all of that lateral weight is negative that counter acts the heavier positive roll weight. For every pound you have lets say up near the hood which is about lets say 20" higher than the roll axis, you need about 20lbs of negative anti roll weight to counter act it if the negative is only 1" lower than the roll axis. See how the money would be much better spent on a fiberglss hood?.... so now you know. }

Next page:

{...So now that you all have read my last post, lets get back into wider tires that also end up making wider track. THis is just making more lateral grip 'hopefully" if lets say you are in fact getting you setup correct and getting all of that tire contact patch width planted for extra help...then what? well as a result you are now producing more body roll since the force of positive roll weight is even greater. You are lifing weight of the inside tires and just simply replacing it on the outside tire.

Why not leave the smaller 8" wide tire and reduce the roll weight which leaves less eight on the outside tire and more weight on the inside tire in hard corners compared to the example I just listed with wider tires.

Now think how transition cornering will improve. Yes it will be much quicker to change directions if the roll is less nad chassis weight is changed direction faster and lighter in roll. footprints will stay better planted.

Now you see why my little V6 car was so deadly to race against in cornering when I had merely little factory 8" wheels on it. Lighter car with less positive roll weight and the tires more evenly distrubuted weight upon all 4 in hard corners- I did not need the wide tires to bear alot of you V8 guys with large meats and lots of power.

Most inportant in part purchase is how you adjust things. Life is all about leverage. A small enough man can lift the weight of the world if he had a long enough lever and the understand to make it work. }

ihatemustangs

iTrader: (3)

That couldn't be put any better. All I am saying is that I have never met anyone from street to drag to road race that experienced any of these problems. I anyone has it would be great to hear and we could really benefit from it. I am far from knowing evreything but we used tubular k-members in 3rd and 4th gens, and mustangs, from 300 to our 1100 rwhp street car and we found all positive results. Again, just my .02 and mean no offense to anyone.

Guest

No doubt, but take the knowledge I just showed you and the car can be built even better with optimum weight balance through weight reduction placement. Its all about loading the tires and how the chassis weight moves about and what percentage each tire is carrying of that chassis weight at all times of a race course, or street, or whatever. Drag racing sees no lateral percentage changes when compared to street driving or road racing.
That money is far better spent elsewhere unless its a full time drag car.

C Murda

i totalled a car with a spohn CM k member on a 4th gen once and it just bent with the frame rails... even the tubular a arms survived

thisjustaintme

Im Running the Racecraft Kmember not the roadrace one tho. Everything fits extremely well its one of the best kmembers on the market.

articwhiteZ

iTrader: (56)

i say. if you want one..join the club and buy one!

then you will see.

after all. going with a all alum SBC. you have to adjst for the loss of lbs also.. put the car together with the money parts you want. then get some time at the wheel. you will get what im saying..

get what you want... spend the money on the parts you want..and see for your self.. 2nd place sucks at the track.. and show..

all alum ZL1 427 BBC $14.000
but you get a cool leather jacket with it!

some say they would never pay that much for a leather jacket!!
and yes it will make your car faster!

Kat

iTrader: (4)

Dean I've put quite a few thousand street miles on my vert over the years. I have Steve's k member on there for 3 years now, along with the coil over kit and tube arms for about 5 years now. So far so good. I drive the crap out of the car also. (Been to floriduh and back a few times and all over the NE here.) along with drag racing the crap out of it when I can. (It runs 11.50's) I'd like to do auto crossing with it, buttt heh I need to work on the brakes. (the engine makes about 10" of vac.)

As for the flex issue, I noticed that my front end felt way more rigid than it with the factory k member.

built91Z28

I have one in my car. I have it for a few reasons.

#1, and most important, I got it for almost free.
#2, it makes working on the car a lot easier. I can drop the oil pan without raising the motor. Also more room for headers to fit. I have Dougs longtubes and I can take both headers out of the car in about 15 minutes.
#3, it looks nice.

I will say though that I am not worried about the life span of the K-member on my car because I drive my car less than 1000 miles a year. Hell, so far its been less than 500 miles a year. I would not put one of these on a daily driver, or a car that sees lots of road use.