[Guest]

im a bit confused, is it the uca or lca or both that bind when aftermarket arms are used? im looking into getting a set of the umi performance uca/lca combo.

 

[Guest]

UCA ....due to angle and twist when suspension flexes...the stockers dont bind they twist so best way is an UCA with some type of "ball" joint/fixture on the frame end....

 

[Guest]

so im better off leaving the uca stock for now?

 

[Guest]

the umi uca's are a good one !! they have the ability to move the way they should with out binding so get them !!!! wish I could

 

[Guest]

is it the uca or lca or both that bind when aftermarket arms are used?

The combination of the stock arms with stock bushings in upper and lower allow the "necessary" flex. So, if you put stiff bushings in the stock arms you lose some bushing difflection, but the arms can still flex. If you put stock bushings in tubed or boxed arms you lose the arm flex but the bushings will still offer some compliance.

Bind can occur when all of the compliance points are removed... stiff arms with stiff bushings... when you ask your rear suspension to move too far.

the umi uca's are a good one !! they have the ability to move the way they should with out binding so get them !!!!

This is an interesting statment. What "ability to move" do they have that all the other arms on the marked don't. It looks to me that the UMI arms are of a very basic design... very similar to BMR's. I'm not trying to say they are not built well... but I don't see anything unique about them

 

[Guest]

interesting points guys, so whats a affordable alternative?

also when does this bind occur? severe cornering? like autocrossing/road racing or during everyday driving? highway canyon carving?

just putting the suspension together and dont want to throw money away on the wrong parts, thanks guys.

spyder, have you used the umi's? or are you refering to these:
http://cgi.ebay.com/ebaymotors/78-96-Impala-SS-Caprice-Adjustable-Upper-Control-Arms_W0QQcmdZViewItemQQcategoryZ33583QQitemZ8029097905QQrdZ1QQsspagenameZWDVW

 

[Guest]

Originally posted by Rustic:
</font><blockquote>quote:</font><hr />

This is an interesting statment. What "ability to move" do they have that all the other arms on the marked don't. It looks to me that the UMI arms are of a very basic design... very similar to BMR's. I'm not trying to say they are not built well... but I don't see anything unique about them </font>[/QUOTE]I think he is referring to our upper control arm's that are offered with spherical rod ends. I do not of an item like this listed on BMR's site, just an adjustable upper with polyurethane bushings.

http://www.umiperformance.com/3617.aspx

Thanks,
Ryan

 

[Guest]

hey if those dont bind then ill be ordering up a set of uppers and lowers soon!

 

[Guest]

A spherical rod end like that is a great part for a race car... it allows freedom of movment and is a solid connection. But it may be a bit harsh for a street/daily driver car. If you use a stock rubber bushing at the diff. end of that upper arm it will help take out the harshness. That same stock rubber bushing will help prevent bind.

also when does this bind occur? severe cornering? like autocrossing/road racing or during everyday driving? highway canyon carving?

The rear suspension is a "triangulated 4-link"... with the upper arms providing the "triangulation." The angle of the uppers keep the rear end from moving side to side, and the lower arms (with some help from the uppers locate the rear end front to back. The uppers are shorter than the lowers.

So.. with that picture in mind, imagine what happens when you have a trunk full of stuff and you go over a speed bump. As the chassis/suspension is compressed, the rear end is effectively moving up, compressing the springs and shocks. The rear of both the upper and lower arms is also raised (or the fronts are lowered depending on your point of view). Since the rear is anchored front to back by the arms the rear actually moves in an arc, not straight up and down.

The upper arms are not only shorter to start with, but they are also set at a ~45 deg angle... so they are effectively even shorter front to rear. So when the rear tries to move through it's arc (especially in a lowered car) it tries to "stretch" the upper arms to match the arc the lower arms want to swing in and to maintain pinion angle.

Now imagine that only one side of you car goes over the speed bump or you are cornering hard during autocross. As one side of the suspension compresses and the other side tries to lift. I'm sure you can imagine the motion the arms "try" to make in this situation. The soft factory bushings and flexable amrs will allow some of this motion but stiff arms with stiff bushings will not. This is the most common bind situation. It can make the rear suspension feel VERY stiff and give you oversteer if you're racing.

 

[Guest]

WOW thanks for that explanation. what would you recomend on a daily driver? stock UCA's? i will be lowered using your GP vogtland springs and bils, and i want newer suspension, so just change out the bushings for new stock ones?

 

[Guest]

what would you recomend on a daily driver? stock UCA's?

For most situations, the stock arms are fine... and new bushings may freshen them up. But most all of the aftermarket arms are a huge improvement in lateral stability and prevention of wheel hop. As long as you keep a stock bushings in your differential mounts... you will most likely keep the "bind at bay." But again, in normal driving, bind isn't a huge issue anyway.... but it will ruin bushings.

 

[Guest]

I put my stock uppers BACK ON after the BMR uppers started diggning into and tearing the urethane diff bushings. I'm a believer in the bind theory!
Bill

 

[Guest]

thanks a lot chris for your input!!!

 

[Guest]

I replaced my uppers with stock ones from Dal. Painted and new bushings...the lowers will be from Rustic, eventually. I think that'll be a pretty good setup for a daily driver. Bind is never, EVER a good thing! EVER!

Problem is, these cars understeer so bad, that bind can make the car feel neutral, so you'll see a lot of endorsements for "certain setups" that lead to bind. Just be aware.

 

[Guest]

Originally posted by Rustic:
A spherical rod end like that is a great part for a race car... it allows freedom of movment and is a solid connection. But it may be a bit harsh for a street/daily driver car. If you use a stock rubber bushing at the diff. end of that upper arm it will help take out the harshness. That same stock rubber bushing will help prevent bind.

The spherical rod ends are a very good cure for rear end bind. This is why we offer this arm; it not only offers free movement through out the rear end but also allows adjustability when needed. We have found the QA1 Eudura series rod ends very street able and find no harsh ride from this item. Unlike less expensive rod ends these rod ends are supplied with a Teflon lining that prevents metal to metal contact. The Teflon lining is also oil impregnated so the bearing is self lubricating. This helps to prolong life as well as reduce road noise. We recommend these arms for any street driven car.

Hope that helps,
Ryan