Hey guys, during the holiday sales I'd like to pick up a trans crossmember and mounted TQ arm for the car. Its the last peice of the suspension puzzle. The car is being built as RR/Auto-X car with the possible 1/4 mile every now and then but probably nothing more than street night. I've got a LS1/T56 I'm building for it so a T56 swap xmember is already needed, plus I really like the idea of moving the TQ arm mount off the trans.

The only two options are Spohn and BMR. I like the look of Spohns, it has the optional front DS loop, Del Sphere joint instead of poly TQ arm mount, and adjustable TQ arm. - $418 shipped with the 15% holiday discounts

What I like alot about the BMR over the Spohn is the xmember itself. It looks alot smaller and tucked compared to Spohns which is big to me since I'll have long tubes to worry about plumbing. But I dont like that BMR only offers it with the stock style clamshell mount just moved. I also dont like how you have to buy the TQ arm seperately and with the NON adjustable TQ arm, total is $425 shipped with the same 15% discount or $492 with the adjustable TQ arm.

So what are your opinions? Ive never used Spohn or BMR before I usually stick to UMI but they dont offer anything like this. Of course I always hear the Spohn fitment issues so experience's would be great. Thanks in advance!

James

 

I have the BMR piece idk which is better but I already had a umi torque arm and the BMR piece gives u some torque arm adjustment up and down .. I think I need to raise mine about 2 holes idk .... After a launch at the track my car started to want to bounce the front end under hard braking .... So ism if I need to adjust my torque arm or the control arms .... Hmmmm

 

I use to have a BMR Xtreme which mounts to the subframes on my old iroc-z. I liked it enough that I am building one for my new camaro. The nice thing about it is you don't ever have to worry about what trans you put in the car. But you need a welder to install it

However I just ordered my dad a UMI setup with crossmember (700r4) and its a very nice heavy duty piece.

Either brand you will be good. IMO. I buy a lot of UMI stuff because their prices usually a a tad better than BMR/spohn

Jay


http://umiperformance.com/catalog/in...ort=20a&page=2

edit just realized umi doesnt offer a t56 option! Surprised

 

Probably smart... The fourth gen axles move the trans mount farther back. Adding a torque arm mount to that just gives the assembly even more leverage to pull against the frame rails. It's not super common, but sometimes they can peel the sub frame rails apart like a sardine can.

 

I've never heard of anything like that happening before, but I suppose anything is possible. My options are pretty limited. I cant fab in a decoupled TQ arm as much as I'd love to because I just replaced 3/4 of the drivers side floor pan and I wouldnt want to have the TQ arm mount there. Also I want the mount of the tailhousing. So it leaves BMR and Spohn.

 

Well it's not as big of ad eal with a T5 or a 700r4 etc, but with a 4th gen trans like the T56, with the trans mount relocated farther back, it gives the trans a lot more leverage to pull against the frame rail.



https://www.thirdgen.org/forums/fabr...hn-torque.html

Not guaranteed to happen or anything, probably fairly rare. But it's just one of those things that's possible and when you are dealing with a transmission that's pulling on those crossmember bolts from a high leverage position... you're not helping the odds.

It's not that much different in theory than having it on the tailshaft, but the difference is that the aftermarket TA mounts on the crossmembers are mounted much more solidly than the factory rubber bushing. That's the point of doing it for the most part. But that factory rubber bushing softens a lot of the pulls and impacts and pushes the torque arm makes against the transmission. I would imagine keeping the crossmember bolts tight and snug will help drastically reduce the odds, but those are not bolts I want to risk stripping. They're notoriously weak to begin with and very easy to crossthread.

 

Well this seems to be quite the dilemma. Maybe with the right SFC's I could tie in a seperate mount for the TQ arm. I'm going to have do some more digging and see what some other people have done. If I'm going to go that far I might as well find a way to fab in a true decoupled set up.

I've looked at BMR's and UMI's set up that come with a new mounting locationg. But those are shortened TQ arms and I know the help acceleration but I've heard they can have negative effects on braking coming into a corner, which this car really is mostly going to be doing AutoX/RR

 

And thats exactly the reason I still have the factory torque arm.

 

Ouch...!!!! Never seen that till today guess I going to check my stuff out next time I am under the car... I do have sub-frame connectors and a full roll cage I am probably ok but OUCH!!

I am running one of sphon prototype slider toque arms from the late nineties broke it a few times but not the frame...

 

I thought i heard someone say that the negative effects of a short torque arm can be compensated with aggressive shock valving in the rear? Dont quote me on that though, let me see if i can dig up the post. I could be imagining the whole thing.

 

If you could find that itd be great. I do have Koni yellows in the back.

 

I know there are autocross/track guys on frrax who have a short torque arm. I remember them saying something to the same effect, but it's beyond my expertise level at this point.

 

"This is where a shorter Tqarm setup I think would pay off in unsprung weight, but you need to focus on acheveing this without brake wheelhop through higher rate rear springs, lower rear RC and shock valving." Said on here by Dean aka Vettruck.

 

https://www.thirdgen.org/forums/susp...orque-arm.html
https://www.thirdgen.org/forums/susp...torque-vs.html
https://www.thirdgen.org/forums/orga...rque-arms.html
http://www.yellowbullet.com/forum/sh...d.php?t=506618
Lots of info on here about it, but basically it really depends how you like your car set up, brake bias, spring rates, weight, shocks, ect.... is my take on it after reading all this stuff. I think the decoupled torque arm is the best of both worlds, but carries a hefty price tag. If your any good at fabricating you can always build your own and save some money.

 

Thats exactly who I've been trying to find some TQ arm info from.

 

I'm going to have to take some time going through those. Right now the cars still being built but as of now its got 200lb/in rear springs with koni yellows. Decoupled is how Id really liked to go but $735 for the one that ties into the cage is alot of money.

 

Ok after some research and though I think the best way to go for me is a modified Spohn set up. The pic I used is of the UMI set-up for T-5 but you get the idea. The biggest issue will be finding a way to bolt in the extra brace's. The extra bracing should hopefully minimize any frame rail distortion. The car is also getting SFC's and I have an 8pt cage going in as well.

 

Here is the BMR piece on my car with umi torque arm and a T5 trans

 

Yea seems alot of drag racers like the long arm set up since it tends to soften the hit to the tires off the line especially on the higher hp cars. But then again theres some guys in those same high hp cars who swear by the short arms. So i am guessing it comes down to overall car set up. As for the wheel hop under braking it seems to be that same mixed bag. Some say they experience it some say they dont.


edit: I think both designs have pro's and cons, some less than others. Seems there are ways to hide some of the inherent weaknesses. But it seems like the really top competitive guys use the decoupled torque arm since its the best of both worlds as far as handling is concerned.

 

I put the BMR crossmember (expensive) adjustable lower control arms(homemade) , and adjustable panhard (60$) on my car all at the same time .. I already had the umi torque arm (100$) on craigslist ..... After the crossmember and stuff I lost .1 on my 60ft ... But that could be due to the tire change went from 15" to 18" wheels .... But I noticed after a hard acceleration then a hard braking my front end wanted to bounce up and down like the tires were out of round ... I set the torque arm 2 holes lower than stock ... Should I move it up ? Anyone have any links to suspension tuning threads ? .... My control arms are set exactly at the stock length and panhard has the rear centered perfectly ... Any tuning tips ?

 

There seems to be so much debate on that. Dean and Sam Strano both made similar points about a "weird" handling feel during cornering when it couples/uncouples.

The GW Tracklink seems to have an overall good reputation but once again this one bolts to the floorpan and there have been people who have ripped there floor. Like I said I just did the pan so I'm not to comfortable with that. Ugh this is quite the situation haha.

 

lol yea that one bolt seems a bit hairy. I wish i had driven a car with a decoupled torque arm to see exactly what it would feel like. Big_mods on here i think thats his name built his own said it helps to have a full cage to help absorb the shock of the arm decouple/couple. But again his car is a full on race car. Dont know how serious you are about getting the max handling potential out of your car.

 

Heres some stuff Dean wrote about the short/long torque arms.

"I like progressive rear springs because they reduce rear jacking of the chassis under hard braking. However, They need to build rate quickly to eliminate wheel hop under extreme braking while promoting rear chassis set into a corner earlier than a higher linear rate spring. I would combine this onto a Penske 4-way coilover so I could independently control both lower piston speed compression and rebound as well as higher piston speed compression and rebound to get control of wheel hop at low speeds but keep rates from building too quickly and allow rebound drop at higher levels and eliminate wheel skipping. These rates and shock dampers would be adequate for massive power with the shorter GW trac link setup used to lay down power and get acceleration bit off the corner with its shorter length, YET not being too soft to cause the dreaded short TQarm braking wheelhop experienced with lower rates. i would also (and here is the major key to it working also with progressive rates) is to outfit the front TQarm mount with a Tq Absorber designed for 3rd link rearends that would act as my slider and in essence a decoupler to take away hard brake pedal wheel hop "initial shock" (this is a secret design- sorry, no more to be said on this topic= it is theory I would have to experiment and work the bugs out. A trial and error process to get the outcome I would be searching for). Otherwise, just use a Xmember mounted TQarm and use the shock and spring rates I have already somewhat perfected on my prior setup and adjust from there to get front to rear balance of the chassis. The progressive rate building as the chassis sets wil keep the car;s rear low and tight on initial turning yet allowing rotation as it sets and the rate builds, it then reverses this principle reducing off corner rear rate again tightening the tailend under hard throttle exits. shock valving aids this process to a pefected dynamic balance of entrance and exit states."

 

I figure when the time comes I will just put a bar across my sfc's and mount a torque arm off of that. It may be shorter, but at least it's not going to damage the car. I do like the idea of the auxiliary mounting pads for the crossmember, but that wont work in my case since I have a double-hump crossmember for long tubes.

 

I have longtubes as well but I think I'm just going to have to make it work. The modified Spohn peice seems to be my best option.

Like I said the car is mostly going to be a track car. It is still going to be road legal for cruises. As of right now the car is set-up in the back with Koni Yellows, 200lb linear Eibach springs on 3" adjusters, Founders PHB with rod ends, and Founders swivel joint LCA's.

This car is going to mostly do AutoX and track days, I dont plan on doing any competition RR but I'm going to use this car to get an idea for what will work when the time comes to build a CMC/SCCA car.

But with that said this is going to be very far from a street car. No heat/AC, radio, windshield wipers, emissions. In front it has UMI Kmember/A-arms, 900lb springs, Konis, and Founders CC plates. I have an 8pt cage to put in. I got a LS1/T56 I'm building in the neighborhood of 500fwhp. I mean the list goes on and on. I guess its going to be like a porche GT3 RS type thing, race car for the street.

Its not going to be completely gutted but all the brackets for the rear seats and any other un needed bracket have been cut out. It will be a very basic interior.

This is one of those personal cars I didnt want to turn into a full race car, but could still enjoy on the street on nice days. I mean its a little past a street car but its not built to any class specs and I'd rather use another car I dont really care about for real competition.

 

I think I just found the solution. This S&W SFC+TQ arm relocation kit and Hawks double hump xmember. Plus I love the way the S&W's tie the car together. I wont even bother bolting them in just fully weld them. It also looks like they extend under the 2 crossmember bolts for added support.


http://www.swracecars.com/store/82-9...71=40-600.aspx

 

Not trying to resurrect the thread but I was gonna say I didn't think the spohn or bmr T56 xmember would clear longtubes anyway???????

I see you are going with the hawks xmember now anyway though. I will probably do the hawks xmember and a UMI weld in torque arm when I do my long tubes

 

Yeah I've been told the same but since the car iisn't going to see much street I was going to try them out and see what I could come up with.