Buggy Disaster

iTrader: (1)

I am on the fence with getting a Tubular K member, most likely from PA racing.


The car will be most importantly, a daily driver (ls1/6 speed), that will see some autocross events, and be Road Raced at Road Atlanta about once or twice a year.

The car will have no AC and Long tube headers.


I have read so many mixed reviews on whether or not the K member was worth it, and I still am undecided. So those of you with Tubular K members, chime in and post your thoughts. Did you notice a difference? Was it worth it? Should I invest the money elsewhere? Please post what K member you have/

Marc 85Z28

iTrader: (3)

I have a PA Racing K-member on my LS swap. I don't have the road racing option and I wouldn't dare try autocross or road racing with this thing I don't think I've ever seen a road race version of the PA Racing K-member for ANY platform. Even with additional bracing I don't see how it would last that type of stress without a complete redesign. Their design is for drag racing and weight reduction moreso than many other brands.

plum92_camaro

I'm doing the same swap as soon as it warms up but I plan to keep AC. and I'm using the factory K-member. I would like to try UMI's road race K-member but this swap is costing enough and the factory k-member is said to be as strong as it gets.

I've only read a few horror stories about tubular K-members and A-arms breaking but thats enough to make me hesitant to ever use them at all for my street/autoX/RR car but there are lots of people who have them with no issues. The UMI RR k-member is new but seems to pick up where most fall short for a street/autoX/RR car.

IROCtheThird

iTrader: (15)

What he said, I bought PA racing k member/ a-arms and sent them back and bought the UMI set up. Its the only K member I'd even consider running on a street/RR/AutoX car. The road course there building here is only 1.7 miles long and the straight isnt too long but Road America is a fast track and I'd want to know everything will hold up well.

jbenge

iTrader: (2)

I've done 2 LS swaps, one with a Spohn tubular k-member and one with the stock k-member. For a mostly street driven car I would stick with the stock k-member so I wouldn't have to worry about any durability issues. If you ever decide to put AC on the car it would be much easier with the stock k-member.

For a mostly drag race application where you are concerned with weight and plan on working on the car a lot where more access to the lower engine is a factor I would go with a tubular k-member.

It boils down to this.

Stock k-member
+no fitment issues with mild fabrication
+no durability questions
+cheaper
-more weight than a tubular k-member
-less engine access
-doesn't look as cool(looks nice when cleaned and painted though)

Tubular k-member
+Better lower engine access
+less weight
+ looks cool
-possible fitment issues
-more expensive
-durability questions on a daily driven vehicle

Pocket

iTrader: (24)

Weight loss is minimal from stock to tubular k-members. The main benefit is increased clearance for Ac, headers and/or oil pan

Avoid the spohn k-member

Buggy Disaster

iTrader: (1)

Looks like I am going to avoid tubular K members in general. Too many negatives, and so little gains. Ill spend the 500-700 elsewhere in the car.

Thanks for the replies!

carattini

I believe you have made a good desition...

jazzdadss

I am just curious here. I hear a lot of questions concerning the durability of the tubular k-members but I have not seen a link or pics of one actually cracking or breaking? Everyone sais that they have heard of these nightmares but is there any proof?

Marc 85Z28

iTrader: (3)

Is this a serious question? Proof has been all over the internet on nearly every F-body and Mustang oriented forum since the late 90s.

jazzdadss

Well, it was a serious question.......... May be I have been living under a rock or something????? I have been on this forum for 5 years now and have never seen a post saying "My K-member broke" or something of that tune????

Just sayin...

Carry on.

InfernalVortex

iTrader: (4)

Most people that use these are not daily driving them. They are often on lightly driven show cars or quarter mile drag cars that get driven to and from the track, if that.

A tube and welds is a lot stronger than the factory parts in most cases, but a lot more brittle. I've NEVER heard of a factory k-member failing. The safety margin designed into those is obscene. But I've heard of aftermarket tubular parts breaking.

The question with K-members, is that there are a LOT of welds, and a LOT of heat treat concerns, and a LOT of stresses on them. Everything that happens to the front of the car goes through that piece and tubular parts dont handle shock loads nearly as well as factory parts. Put it on a track and you're fine. Drive it on a typical country road or over some rail road tracks... eh... Roulette.

The UMI piece looks pretty beefy, if I got one, i'd go with theirs. But for the money... I can get more performance in other areas.

I suggest you read through this thread:

https://www.thirdgen.org/forums/susp...arm-broke.html

It's pretty insightful.

With that said, there's a guy on frrax who has a road race PA racing k-member on his thirdgen with no issues. Definitely not a daily driven street car, though.

I honestly feel like there's no way to know how strong these things are until someone breaks one, and even then you never know if maybe one of them had better welds than another. It's just a very complex piece with a LOT of stresses going through it. Every single weld is another potential point of failure. Tubular a-arms scare me too (See above thread) just because tubular pieces aren't good at handling those kinds of stresses. I have all tubular pieces in the back of the car but the stresses seen by the rear parts are much different than the fronts.

articwhiteZ

iTrader: (56)

iv never seen any post showing cracks. all the post iv seen with probs are fit probs..and most of them the cars are...well we will just say.cars with alot of miles on them..

no telling what sorta dukes of hazzard driving was done ..if any before install
and a broken A arm is not a broken K member.
the only A Arm i seen fail it was not a weld. but a brake in the tube itself.

and even OEM parts fail. even when new.. just look at all the recalls done over the last few years. spendles. drive lines wheels.and thats just Dodge.

iv seen ARP rod bolts fail after 5 years of week end driving and 2400rpm (bolt fell apart.not just broke)
so nothing last forever...go fig...as the years pass. things would get better ya would think?

not so bad.. and nothing more in what 9 years?

and dropping 25lbs by going to a tube K member is a lot.
ya can drop almost 100 lbs of the front of the 3rd gen.with just bolt on parts
alum heads 40lbs
Kmember
A arms
Coil overs 38lbs
plastic head lights 5lbs
aftermarket calipers 7lbs
headers 11lbs.
ya add a fiberglass hood 18lbs
ya get over 100lbs off the car. so almost 1/4 in just a K member is alot.
and its gone..
putting the bat in the back...your still packing it... but its off the front ya take another 35lbs off the front..

Pocket

iTrader: (24)

The fitment concerns with most k-members have nothing to do with age/condition of the chassis. If half the holes don't like up, sure point to a tweaked chassis. If the engine sits crooked in most of the installs, it's a faulty part. You can't age a chassis to the point of the driveline being crooked or steering components rubbing

FYI, the stock k-member is around the same weight if not lighter than any tubular design stop posting weight loss on the k-member

InfernalVortex

iTrader: (4)

Just depends on whether or not it's a risk you're willing to take I guess. It's a calculated risk for sure, but I personally cant justify it.

jazzdadss

Thanks for the insight fellas. Not trying to jack your thread Buggy, Just tryin to get down to the "NITTY GRITTY"

Marc 85Z28

iTrader: (3)

My mild steel PA Racing K-member with LS mounts and spring perches is 22 lbs. My stock K-member was 51 lbs.

Buggy Disaster

iTrader: (1)

Lol, no problem! I was wondering the same. The more information given the better!

articwhiteZ

iTrader: (56)

Dont want be a pain...but I have this thing called a scale.. and you can put things on it. To see the different weights. Works fantastic...ya should check into it some time.ya see I dont just take a stab at things. And see if its going to work..not into the shot in the dark sorta thing.....
want to add.. the lbs I listed above. Are the difference in replacement parts..just so you know

LX_SS

If your ever in doubt with such a product ask for the on road testing data specs, If none can be provided to you, this gives you your answer indirectly. I generally request such data on major suspension, steering and braking components. Another thread on this forum in fabrication is talking about custom wheels, another product that will be either a go or no go based off the testing data sheets that are yet to be done.

The factory k-member isn't light, but it certainly has a lot more strength than the tubular k-members, this part isn't questionable. The aftermarket k-members/a-arms only have weight reduction going for it, which is great if your a drag/racing car only.

1500hp in 400m of road is very different to 300hp in 10k-15k miles/kilometers per year.

articwhiteZ

iTrader: (56)

Thay are made to hold larger spring rates..as the spring that far in needs to be. Almost 3TIMES what a coil over spring rate would be..rebound and compression still placed on the shock tower.along with the new spring rate..the average coilovers spring rate is going to be under two hundred and twenty pounds.but .let's just say. Its for us drag race guys my car mid 10 sec with a factory K memeber and front end parts..Now with twice the motor and blown I want to go faster so I drop pounds off the car...I think it's pretty safe for me...now if everything fits iI'll be happy

dennisschreuer

iTrader: (3)

I have a PA racing K member in my car for 2 years now, I told Kenny when I bought it, that I was going to do some road racing and canyon carving, he beefed it, I've had zero issues
I drive the crappy streets in LA at times and run at Irwindale, going to Fontana for the extreme course soon.
Dennis

customblackbird

iTrader: (15)

Ive got a moly race craft Kmember installed… waiting till the cars done but it will be driven on the street…

Moly isn't as brittle as people think, airplane frames are made with moly and they flex a WHOLE lot! The UMI piece is beefy but doesn't offer as much room as the single tube designs. I have a 521BBF hanging over mine and I hope it holds up well on the street.

Marc 85Z28

iTrader: (3)

Aircraft are subjected to different types of loads. Furthermore, the CM is normalized before going into service, and many types of repairs/welding in the field are prohibited. And rather than compare your CAR to aircraft, compare it to something a little more similar, like a stock car in NASCAR, where chromoly is prohibited.

Chromoly will fracture where mild steel will bend. I'll take a bent K-member over a broken one anyday, especially at speed.

Pocket

iTrader: (24)

CM also gets weak points extremely easily. Scratches and gouges dont really bother mild steel but create major fatigue points and promote stress fractures. Not a big deal for more parts but if you bottom out like all Spohn K-members will, the gouges will compromise the already weak main hoop

articwhiteZ

iTrader: (56)

Thats one thing for sure...stay away from spohns K member...it is absolute junk installed one for about an hour. just to move a car it fit nice. but its design was absolute junk nothing else would fit right.!

Picked up a UMI K member...it was like it was made by GM...fell into place..and all the other parts just like before.