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Durable QUIET aftermarket k-member and lower A-arms
I want the quietest, most durable aftermarket k-member and lower A-arm setup for street use.
When I hear terms like "polyurthane" and "rod end", I think of noise.
Since this is a street car, I'm thinking that the boxed adj lower a-arms with the roto-joints would be much better and much less noisy than rod ends/polyurethane setup.
Are upper aftermarket A-arms worth the upgrade for a street car? How much weight savings are we talking? Are they noisy?
Anyone running the road race UMI and boxed roto-end A-arms on the street and how quiet is it?
I've read that the UMI k-member road race is the best, most durable for street use, and that MWC, BMR, and PA-racing are best for track use.
I gotta ask, if the car is just a street car why go through all the trouble for such little weight savings?
It would be different if you were chasing down times at the dragstrip, but I think for a street car you could put money elsewhere.
Poly shouldn't make noise if its greased, but can cause bind and stiction, even when greased.
The rotojoints from my experience with the rear LCA's is they are quiet as stock when the rotojoint themselves are tightened down, but if they come loose with will click/clunk.
FWIW I wouldn't trust any aftermarket K-member on the street other than the UMI RR one, Ive seen many others break on here, you can find them by searching.
I have the UMI RR model and it has held up great over the years on the street. I still have the stock A arms, but I do have the rear LCAs in poly/roto. They are completely silent, so I would suspect having A arms in the same configuration would be just as quiet. Even though it is a bit of work and money for little weight savings, I would recommend it just based on how easy it makes working on the engine. It literally feels like working on a new car with all of the space.
Id have no problem driving around on a MWC k member after seeing a few cars with his setup taking hits like in that thread above. And I know that all there heim joints on my rear set up are quiet and no extra noise what so ever
Any mild steel K member will be good for street use. Don't be hung up on ultimate weight savings. The lighter the K, the less durable and street-able it will be. Honestly, I wouldn't do the upper arms unless you are all out racing or lowering more than 2". Uppers will promote a lot of NVH, especially with a rod end style upper arm.
Id have no problem driving around on a MWC k member after seeing a few cars with his setup taking hits like in that thread above. And I know that all there heim joints on my rear set up are quiet and no extra noise what so ever
Thoughts on an MWC k-member on an auto-x car? I've been in the mindset of keep the stock k-member or maybe the UMI RR.
Thoughts on an MWC k-member on an auto-x car? I've been in the mindset of keep the stock k-member or maybe the UMI RR.
The only one durable enough to replace the stock K for handling applications is the UMI RR.
To the OP, the K member and lower arms would be the last thing I replaced on a street car. I see no point in doing it. There are no aftermarket pieces that are as quiet or as strong as stock.
Id have no problem driving around on a MWC k member after seeing a few cars with his setup taking hits like in that thread above. And I know that all there heim joints on my rear set up are quiet and no extra noise what so ever
Thank you. This is why we use a quality maintenance free heim joints.
Originally Posted by blackandgold
Thoughts on an MWC k-member on an auto-x car? I've been in the mindset of keep the stock k-member or maybe the UMI RR.
All though we don't push it we have built k-members for road race specific vehicles. They still end up lighter than anyone else's on the market. A light K-member absolutely does not mean weaker as items get strength by design.
We do however have customers with our mild steel K-member's multi purposing between street, drag race, and auto-X.
Thank you. This is why we use a quality maintenance free heim joints.
All though we don't push it we have built k-members for road race specific vehicles. They still end up lighter than anyone else's on the market. A light K-member absolutely does not mean weaker as items get strength by design.
We do however have customers with our mild steel K-member's multi purposing between street, drag race, and auto-X.
For sure, I was just curious if you guys had a mainstream solution for the Auto-x crowd. (I'm not in the market for one yet).
A little off topic but I'm still curious... MWC, you always use the term "heim joint" I'm assuming that's the same as a rod end? Are the two terms interchangeable, or is their an actual difference between the two
Last edited by Corvett z07; 11-09-2015 at 11:53 AM.
Reason: Spelling
A little off topic but I'm still curious... MWC, you always use the term "heim joint" I'm assuming that's the same as a rod end? Are the two terms interchangeable, or is their an actual difference between the two
A little off topic but I'm still curious... MWC, you always use the term "heim joint" I'm assuming that's the same as a rod end? Are the two terms interchangeable, or is their an actual difference between the two
No they are the same some say heim joint when referring to them.
Back when UMI was going to build a K-member Ryan and I had a meeting. At that time I told him if he built a single tube version I'd never sell one.
In fact a lot of what you see in that part was based on my recommendation, like the two cross tubes, the seam welding, the gusseting, and the larger alignment slots. I'm proud to have helped and UMI's willingness to listen to such advice is one reason I use them for things like this. Since then they have added things like the slugs to make sure the camber won't slip in hardcore handling situations like autocross and track work (RR version only).
It was a little bit of discussion because of weight. But simply put the front suspension attaches to the K-member, and high cornering loads go directly into the K-member. And all one has to do is look at the stock boxed type one to know that needs to be more beefy than one tube supporting all that lateral load.
There was, once upon a time, a video a company put up of a car wheelstanding, then slamming down and not busting the K. That, to them, showed how strong it was. Except for the detail that the loads in that case go into the shocks, springs, and the shock towers... not the k-member. Think about that, then think about a suspension company posting such a thing to prove how strong that part is. It's like trying to prove how strong the engine was because it didn't break either.
The UMI K is the best one out there for this car for the reasons mentioned above. And it's ONLY one I'll sell. And yes, I can sell others through other vendors, including one "big name" one.
As for the control arms. If you want the best ride and most quiet. Stock is the way to go. But there are high end rod-ends that are very quiet, at least for a while. I carry those ends if/when you want or need to replace them. Or you can go Roto-joint and have the option to rebuild and tighten those instead. But there is a reason you don't find such parts on cars from OEM. Rubber bushings are the best for keeping NVH down. Period.
The UMI RR K is what I run. I would also strongly suggest if you are going to put a lower A arm on as well to stay away from the round tube versions. I broke a set of chrome moly ones. I have UMIs RR boxed ones now.
In Sept I did 7 Time Attacks, 3 auto crosses and 1 half mile in 5 days. Lots of bumping of curbing. All is still 100% solid.
If you are drag racing you can go for the lightest stuff. Tracking and the street are hard on parts.
As for noise, I can not say. I went all rod ends for lowest friction and most accurate locating of the wheel under load.
On one track we were seeing 168mph into one corner. I do not want anything to break!
Absolutely I'd run Boxes vs. tube front arms. That was another discussion and why you only see UMI doing it today. Tube arms are lighter, but that's not much of a matter if you bust one and you screw something up. I've seen tubular front arms break, it happens when you put a lot of lateral load into them.... There is no free lunch.
Back when UMI was going to build a K-member Ryan and I had a meeting. At that time I told him if he built a single tube version I'd never sell one.
In fact a lot of what you see in that part was based on my recommendation, like the two cross tubes, the seam welding, the gusseting, and the larger alignment slots. I'm proud to have helped and UMI's willingness to listen to such advice is one reason I use them for things like this. Since then they have added things like the slugs to make sure the camber won't slip in hardcore handling situations like autocross and track work (RR version only).
It was a little bit of discussion because of weight. But simply put the front suspension attaches to the K-member, and high cornering loads go directly into the K-member. And all one has to do is look at the stock boxed type one to know that needs to be more beefy than one tube supporting all that lateral load.
There was, once upon a time, a video a company put up of a car wheelstanding, then slamming down and not busting the K. That, to them, showed how strong it was. Except for the detail that the loads in that case go into the shocks, springs, and the shock towers... not the k-member. Think about that, then think about a suspension company posting such a thing to prove how strong that part is. It's like trying to prove how strong the engine was because it didn't break either.
The UMI K is the best one out there for this car for the reasons mentioned above. And it's ONLY one I'll sell. And yes, I can sell others through other vendors, including one "big name" one.
As for the control arms. If you want the best ride and most quiet. Stock is the way to go. But there are high end rod-ends that are very quiet, at least for a while. I carry those ends if/when you want or need to replace them. Or you can go Roto-joint and have the option to rebuild and tighten those instead. But there is a reason you don't find such parts on cars from OEM. Rubber bushings are the best for keeping NVH down. Period.
This is a rare instance where I will agree with Sam lol. Design will only do so much without material.
However, I do have to raise one point where it comes to the strength testament example. When the front of an f-body slams down, what is the first part of the car to touch the ground?
Well none of it should, but when folks do stupid things that allow it to hit, then sure the K-member would be what hits. Of course it'd be the steel tubing in the center which I don't think shows you anything about how good a design something is, but rather how strong a steel tube is.
10-31-2015, 06:24 PM
Durable QUIET aftermarket k-member and lower A-arms 
