Hi folks,
The saga continues. My car still pulls to the side while when under heavy braking. The wheel does not seem to turn much, but the car just arcs slightly to the left or to the right. Since I last asked for input, I have:

Cleaned calipers, pistons, rotors, etc
"deglazed" pads with sandpaper
rebled all four corners
tightened all bolts
switched to raybestos (el cheapo) pads in the back
tried setting front shocks to full stiff to slow weight transition

This helped a small amount, but the car now pulls both left and right (as opposed to always right). I ran the car at the Jefferson circuit and it does okay as long as you are below 100 or so. Above that and it gets worse.
If you ease into the brakes, it seems to pull a little less. Also, the car does a little "nose wiggle" as the nose comes up when you get off the brakes. It is hard to describe, just a quick side to side wiggle as the suspension rebounds.

The New Theory:
Both of my forward, inner, lower control arm bushings are moderately, but not horrendously, torn. Could this allow enough tow-out to "arc" the car when the front is heavily loaded during deceleration. Seems like a stretch, but maybe.

Possible alternate theory:
Blown shock. This seems less likely as the car should straighten out once the weight is transitioned, but I am open to suggestions.

All thoughts and opinions are welcome.
FYI - As a reminder, the setup is:
Willwood superlites on 11.75" rotors up front (Panther +)
11" rear kit, stock calipers, Raybestos pads
Ground Control coilovers (350f/ 275r)
Tokico Illuminas (set full stiff all the way around)
Brakes are all nearly new and in great condition
Camber is 2.0 all the way around. Castor is equal left to right (1.8?)

 

BLEED! If a caliper has some air in the line, less pressure will be exerted on the piston, therefore it will pull to the opposite side. Bleed the system and you should be good.

 

Hi,
Thanks for the input. Unfortunately, I would bet a $1000 there is no air in the lines - I have gone through quarts of motul 600 trying the same approach. Please keep the ideas coming.

 

Are you running toe out up front? How about out back? Toe out up front will help with turn in. Too much will cause the car to dance over rough pavement. Toe out in back will help the car to rotate. Too much will cause the *** to dance under (heavy) braking. Just some ideas since you didn't mention that aspect of your alignment. Bushings: I did notice that, to me, the car felt more stable when I switched to ES all around. If your bushing are shot, it might be something to consider. I don't think that it will be a cure all though. Shock settings: I don't think that having the Illuminas set on 5 f & 5 r should be nessasary (sp) with the spring rates listed. It will slow the response/transistion but it will still happen. I would think that you are overdamped for those rates. I would try maybe 3 f & 4 r. JMHO.

Oh yeah. You talked about stuff you did to the brakes. Did you lube the slides too? You might have a slow/sticky caliper.


[Modified by civicrr, 6:40 PM 7/14/2002]

 

Whoops, didnt see this before. Sorry. An agressive alignment shouldnt make the car pull to a side if both side are the same. Thats the thing I would check next as previosly mentioned.
Also, dont think chaning settings on shocks would do anything.

 

Note that he said the car will pull "both left & right". The car might be 'hunting' because of the agressive alignment. i.e. trying to follow the crown of the road or inperfections in it.
I don't think changing the shock settings will change anything either. I was trying to say it was a band-aid that wasn't helping anyway. Again, I think that it is overdamped for the listed spring rates.

 

I am not saying it is incorrect but I would assume that unless you had 4 individual masters - one for each corner, air in ANY corner would allow compression of hydraulic fluid thus creating a spongy pedal and exerting less than full force to all 4 corners not just one.


Mike, does camber affect the car's tendency to veer to and fro under braking? I would have thought toe. ITR, out of curiosity are you running a wide low profile tire (and does this braking instability coincide with a change in tire profile or width)? I ask because I experienced what other P-car guys describe as "Tram-steer" when I went from a 215/55-15 to 245/45-16 on the 44 and the car suddenly felt darty as hell - esp. under harder braking. No clue, just guessing.

 

I'd think toe would lead to an increased tendency to wander under braking. Phil, have you checked your toe recently? I know my Integra tries to pick its own line under hard braking with the slightly more than 1/8" toe-out I had on it.

Can anyone think of anything in the suspension that would allow a toe change under braking without making an identifiable noise? I'd think a bad balljoint could allow for some motion in the suspension that might allow for a slight toe change, but I'd also think it would make some sort of clunking noise.

 

How bad is it? As in, "It's noticable" versus "I almost went off."

If its the former, I'd say its the nature of a nose heavy car just doing its thing under braking. If its the latter...I'd look and see if you have a sticking caliper.

 

I see your point but I dont think its the case. If a line has a small bubble at the end (closest to the caliper), than when the pedal is depressed, that small bubble causes a loss in surface area between the fluid and piston. Obviously, the less pressure exerted on the piston, the less braking force is applied. Ive had my car pull; bled the system, and the car was fine. Braking systems are finiky. Ramble much?

 

IMO, if you pull either way under braking, 90% of the time, it will be a suspension/alignment issue, not a brake issue.

Look for bad bushings. After I replaced a toasted swaybar bushing/endlink, the car was MUCH better under braking.

Warren

 

I wonder if it is an wheel offset issue. I have heard of some weird things happening with imporper offset wheels.

Since you say that some of your bushing are toast (torn), why not replace them. It is something that will need to be done anyway.

I went from toe out to 0 toe in the rear. The car just felt too loose for me & my co-driver under hard braking.

 

Wow folks - thanks for all the great input. A few answers of my own to your questions:

Karl, while not consistent, it can be significant/scary. As in "I was track left at turn 1 at summit (and trying to stay track left) and was often going mid-track by the time I got to the turn-in point.

Toe (accoring to Merchant's) is set to zero all the way around. Or at least very close (< .0-.2 degrees or so)

Warren, I am suprised a sway bar bushing made that big a difference. Any thoughts.

Any chance I am picking up dynamic toe out in the rear as the tail comes up under braking? This seems like more of a stretch than flex from the front bushings.

Calipers recently dissasembled, greased, etc.

Wheels are 15*7 Koseis = 38 mil offset. Tires are 205/50 AVS Intermediates.

-Phillip

 

how old are the tires? have you tried different rim/tire combo? i had braking issues witha set of kosei's and old bfg r-1's.....after i replaced those braking and handling changed drastically!

 

I go for this theory. Torn bushings would tend to flex more than they should. Heavy braking and flexy bushings would increase toe-out. This would make the car more liable to follow the crown of the road, or any other small factor that could send it off in a random direction.

 

Just a theory and I may be way off but do you have an LSD installed? In the ITR that I drive it is always pulling to one side or another under heavy breaking like you described. I just wait for it and counter steer a little. Doesn't bother me much, kinda got used to it. I just assumed it was the LSD because I went from a GSR without having that problem to an R that did. They were both running panther plus pads.

 

The LSD doesn't work that way. Your problem was probably either a toe issue, or not enough rear braking power.

 

Bushings. Damn near impossible to diagnose a problem if ither broken **** is adding noise. Fix these, then see if the issue continues.

 

Brake Balance Controller, I think they run about 10,500. [joking, gt3 0wns]

 

just another option

worn steering rack. check the adjustment.

 

How old are the calipers? Are you sure they're not just old and sticky?

 

Hi again,
Thanks for all the input. I really appreciate it.

FYI Calipers are allnearly brand new.

After consolidating info from Wilwood, OPM motorsports, and the impressive knowledge of this board, from control arm bushings seem to be the most likely problem. I will let folks know the results once they are changed.

Please see my new post if you have thoughts on which bushings I should go for...

 

Can you provide a source for this explanation? My limited understanding of hydraulics makes me think that an air bubble (or vapor if you will) will be compressed by the fluid as the air is substantially easier to compress. Its that compression that gives you a spongy pedal - if what you were saying was correct, you would have the same pedal but less effective brake force - not what happens with air in brake lines from my experience. Also, if what you were saying were correct, you would have no problems with air 2 inches away from the caliper??? That doesn't compute for me - perhaps it is my lack of understanding.

Agreed, that is "obvious" but what you are saying doesn't make sense so this should not happen from air in your brake lines unless you have more than one master cylinder or some sort of (very intelligent) check valve.

Actually, I am not sure I fully agree.


I will gladly admit my lack of brake comprehension but this line of resoning doesn't make sense to me. I would be glad to be educated otherwise.

 

Phat-S...
I think most of the questions you had of my previous post had to do with the idea that compressing the vapor in the system causes a loss (or not) in braking ability. Compressing air in the line will aid in braking to a point, but will exert nowhere near as much pressure as the fluid will due to the density of the fluid vs. air. Correct?
As for your statement about 2 feet away from the caliper... It seems that this would have the same effect as having a bubble close to the caliper. It just seems to me that most bubbles occur closest to the caliper due to the heat the caliper puts off (which can cause the fluid to boil), and also the bleeder screw (which is a good place for the system to leak, esp. with speed bleeders/old worn bleeder screws) is right there.

Let me just close this off by saying I have NO technical "proof" to back up my statements. MEARLY my understanding!

 

do you have your SPRINGS in the right place....are you sure you didn't mix them up when putting them on.....crisscross?