themealonwheels

iTrader: (20)

I've got a 383 LS6 in a 2002 Z28. When I had the motor out, I was pleased to find I came in ~$1000 under what I had budgeted for the build. In celebration, I blew it on front end suspension goodies: Tubular BMR K-member, adjustable UMI lower A-Arms, and some urethane bushings for the sway bar. After everything was back in the car, I discovered a few threads on here talking about tubular K-member failure.

https://ls1tech.com/forums/suspensio...really-do.html

https://ls1tech.com/forums/suspensio...-k-member.html

It doesn't seem common, but it got me worried since this car sees mostly DD service. Next to replacing it with stock, what else can I do to prevent breakage?

I posted in the STB thread a few days back without much success... would a STB help to compensate for the lower lateral rigidity of the tubular K-member? Anyone have any information on the subject? UMI? BMR? Founders?

UMI Sales

iTrader: (1)

Hey mealonwheels.

We have hundreds of K-members out there and have never had a customer complaint concerning failure on their daily driver. The main benefit is decreased front end weight. As other threads have mentioned, the stock K-member is the strongest but when something is over-strong (such as the factory) it leaves room for us in the aftermarket to make something completely suitable at a lower weight.

As a side note, Ryan (UMI President) heard from a customer that one of our K-members plowed a groove in a dragstrip when the front end came down too hard. The only damage was chipped paint.

As for a strut tower brace, since that thread is pages and pages long, my two cents is they are an easy upgrade and I choose them on all my vehicles. Quantitative data or not.

BMR Tech2

iTrader: (5)

We sell anywhere between 400-500 K-Members a year and we seldom, if ever, have customers call us up and tell us theirs is broken. So, if it were a real concern, I would expect at least a call every month...or every other month...or every year. Not really the case. Just a seldom isolated incident here and there. We did, however, have some issues with our first design, but not with our new design that was changed about 5/6 years ago.

You should be just fine!

themealonwheels

iTrader: (20)

Hey thanks for the reassuring response! I've done more reading, and it's reasonable to expect that the information about failed K-members is skewed a bit from the population's experience. After all, how often does someone seek out an opportunity to say their K-member is working great compared to when it fails? Cool, thanks for providing some experience feedback there

On the strut bar, I'm still not convinced. The main mode of failure of tubular K-members appears to be in DD applications on the center bar between the two sides. I'm not a mechanical engineer, but it just seems like this is indicative of side-to-side stress, more pronounced in a DD/road race application where turns are much more common (hopefully) than at a drag strip. And since the STB adds 7lbs, it negates some of the benefit of the K-member. So, if it's a real failure mitigation piece for tubular K-members, I would sacrifice the 7lbs for an overall weight loss of ~18bs. So, any data?

themealonwheels

iTrader: (20)

That is also reassuring, thanks for chiming in! Sounds like I would be just adding weight with a Strut Tower Brace? I mean, beyond the claims people are making in the STB/waffles thread in the Suspension/Brakes section? I mean, basically, a STB wouldn't affect the durability of a tubular K-member in a DD application?

spy2520

iTrader: (3)

I just recently drove my car from MD to Metlife Stadium in Jersey. It is a road race UMI k-member but believe me, if there was a time for it to break, it would have been then. Those roads have craters in them.

themealonwheels

iTrader: (20)

I'm almost certain I know the answer to this, but do you have a strut tower brace? Good input, I hear ya loud and clear... I'm in Wilmington, DE and it seems like a good suspension test site anywhere you go!

UMI Performance

iTrader: (77)

Thanks for the feedback and this is great to hear. My current project car has had one since 2006 with 30k miles and no damage or wear. This is just another great example of how well these can hold up.

The picture below is customers car that Ramey was referring too. He is running a best 60-foot time of 1.27. The car has popped up twice and startled him and came back down and hit the ground. Our K-member has smacked the ground twice, once leaving a deep divot in the track. Neither time has effected the K-member other than the powder coat.

SSHAWK

iTrader: (14)

I have both and had no problems with the UMI K-Member and STB combo. As to tell you if it helped me anymore without having one I can't tell.

DropTopBird

iTrader: (17)

No scientific data here, but my UMI road race kmember doesnt show any wear from crappy PA roads. I went with the road race one due to the extra bracing on it just for piece of mind. I can jack it from the front just like the stock k member with no issues either. Like I said not scientific, but just my experiences with it.

themealonwheels

iTrader: (20)

Well, I didn't do enough research before I bought my K-member and didn't get the road race version so yesterday my STB arrived and within 20 minutes it was on my car. Hopefully this will just provide peace of mind and I'll eventually stop worrying about my K-member

To be honest, I'm not sure if it will though. I bought the Founders' piece, and though I was pleasantly surprised with the lightweight yet beefy nature of it, the mounting surfaces were slotted in the way the force would be applied. I torqued down the strut nuts, but if force were applied in the lateral direction in the magnitude that would cause K-member failure, I would think the STB would give first due to the lateral slots in the mounting surface... I guess time will tell?

BMR Tech2

iTrader: (5)

We have never associated a problem with our K-Member and STB being used together. The paring happens quite often, actually.

mitchntx

iTrader: (14)

From folks who regularly abuse their cars ... these guys crack stock K-Members!

http://www.frrax.com/rrforum/index.php?showtopic=13841

http://www.frrax.com/rrforum/index.php?showtopic=8071


I wouldn't even consider anything but a UMI unit.

sjsingle1

iTrader: (1)

linkee no workee

mitchntx

iTrader: (14)

:dunno:

Seems to work for me ...

themealonwheels

iTrader: (20)

I'm not saying the STB would complicate any issues with using a tubular K-member, I'm asking if adding a STB may mitigate any structural compromises (if there are any) with lateral forces in a tubular k-member scenario. Basically, IF a tubular k-member fails laterally due to less rigidity side-to-side than a stock k-member (again, that's IF), then would the additional lateral support at the shock tower help solve some of this additional flex in the k-member? I have a feeling this won't be resolved technically, but I've got a STB on now and hopefully some peace of mind someday

Not arguing which unit to use, I've already got a BMR unit in there (Thanks BMR!) And though the links do not work for me, it appears to be to a road race site. I don't road race, but I had heard of tubular k-members breaking in daily driven applications.

BMR Tech2

iTrader: (5)

Understandable concern. But, like I said, we hardly are presented with a failed K-Member to begin with. As a matter of fact, we just looked into it and we have not been presented with a single failure with our second generation K-member that we have been building for the past 6 years. Talk about assurance in a product! Adding a STB on there would only serve to strengthen the connection as the forces would have more area to spread.

As for the broken stock K-Member...if you break a stock K-member, you're going to break anything. A factory A-arm, a factory hard mounting point, a wheel, etc. This is not the norm, and it shouldn't deter anyone from buying an aftermarket K-member, IMO.

UMI Sales

iTrader: (1)

Even though we're in friendly competition as suspension manufacturers, I agree with Kevin. We have customers on standard and road race K-members and most use STB's, and a few don't. Failures are statistically non-existent.

ramey

themealonwheels

iTrader: (20)

Agreed. Break a stock K-member? You're doing it wrong kidding, that's just impressive!

Wow, great! To hear of virtually no failures nowadays is very reassuring, thanks for the feedback guys

TruBloodTransAm

iTrader: (24)

Glad I saw this thread! I'm planning on swapping my kmember soon but recently I've been reluctant. I saw some posts on here about the aftermarket kmembers breaking. Glad to read that its very isolated. This will be going on my daily driver.