Ok.. help me diagnose this..

First, the following have already been replaced:
Front Rotors
Front Pads
Rear Rotors
Rear Pads
Shocks
Springs
Front LCAs
Wheels
Tires.

Car is aligned perfectly, car ONLY shakes under moderate to hard braking.. any other suggestions?

 

Control arm bushings?

 

On all surfaces? Stupid question, but is it the ABS modulating? sounds like you've replaced just about everything logical..sounds like rotor warpage, but you say you replaced those....

 

the only things left are the calipers.
i had a bad brake shimmy on my old gsr even after i replaced the front rotors. i took it to acura and they discovered the left front caliper had broken - replaced under warranty.

 

The problem started at ~12,000 miles, hasn't worsened yet (31,000 miles..).. it's not ABS, I don't have to be braking anywhere near THAT hard for it to shake.. and I can tell when abs does modulate still.

I think I'll rebuild the calipers, didn't think of that. Screw, I'll just make Acura fix it.. although I doubt they will (Crown Acura in Clearwater, FL has the WORSE service department in the world.. at least of any I've dealt with..)

 

y not just go to another acura dealer?

 

Bent hub? Why did you replaced all those parts? Did you whack a curb or pothole. A bent hub will give the shake, and the hubs bend pretty easy.

 

try checking the rotor runout on the car. Make sure the rotor is firmly mounted and check it with a runout guage. Get five washers that are big enough to fit over the studs and thick enough to give some space between the rotor and lugnut. Tighten them down to about 30-40 ft lbs and then hand spin the rotor and see how much runout it has. There should be less than .002". Any more could mean a messed up hub or warped rotor.

Sometimes even new rotors need trueing as they may have been dropped or stacked on during shipping. The optimal way is to turn them with an "on the car" brake lathe but very few shops have these or the mechanics who know how to use them properly.

Hopefully its something easy like a stuck caliper slide, but my money on the rotors, keep us posted.


[Modified by 98_ITR#396, 5:35 AM 6/20/2001]

 

Id say the rotors are out of round. I have seen many times where people replace rotors with new and they are warped.


Boba-whod be pissed if he replaced his rotors and they were warped.

 

There's probably nothing actually out of spec, or mechanically wrong!

Are these 120-50 mph sudden stops (decelerations)?
The heat just can't be dissipated quickly enough, and the rotor develops distinct discolored hot spots!
Modulate your braking, or upgrade!

I used to see those spots on my R's rotors (as well as the shuddering).
Changed braking practices and things are much better! HTH ed


[Modified by zygspeed, 8:42 AM 6/20/2001]

 

Dave,
i was actually describing the same exact problem that i'm experiencing to willard.
brake shudder under moderate to hard braking, moderate to high speed. feels like warped rotors, but doesn't make sense because rotors are new. my wheels are new, tires are alright, and i'm getting an alignment today.
so, will also suggested replacing some of the suspension bushings. i have 1 new LCA, hub, bearing etc.... so calipers is sounding like a possibility also... btw i have 63k miles on my R.
anyway, i'm in troubleshooting stage here also... post again if you find something that clears up the situation.

D

 

imnot: the next closest is a fairly good drive considering I'd have to take the car there during the week and have someone take me back to work.. unless I take a day off.. and If I do that I'll just replace everything myself.

00ITR: The only parts replaced to try to fix the problem were the rotors. The problem spanned everything else. The LCA was replaced due to a pothole however, but this was a good 5-8K after the shake started. I will check the hub though.

98_ITR: The fronts are slotted, can't turn em. They are going to be replaced with OEM rotors though.

zyg: These are 70mph slowdowns under moderate (at worse) braking, nothing nearly hard enough to generate that kind of heat. It has seen high temps from track events though (on the old and new rotors).

D: I think I'll try the hub next (with another set of rotors). If the problem still continues, I'll take in into Acura and have them figure out the problem. I'll let you know.

Currently the car aligns good, caster is a little off on the RF and the RF camber is a bit more than the LF, this was only after the shocks/springs though and the problem was occuring before that..

 

Dave,
i also have slotted rotors up front. OEM pads... i had a quick thought that this might be the cause, but someone swayed me otherwise...

also, new hubs from acura aren't cheap. prolly ~$100 each, plus you'll need a new wheel bearing for each one you change out... ~$50 each.

btw, i just found out the the caster on my right front is pretty good out of spec. any ideas as to what might be bent? camber and toe are within spec.

D

 

Dave,

One other thing I thought about, hows the balance of the tires. Sometimes this can be culprit.


Boba- who just got his tires balanced.

 

D: I'll try to find someone willing to swap over some parts first.. we'll see My caster was WAAAYYY off due to a bent LCA, it's suspected that the upper arm is also slightly bent but there's not enough of a caster difference now to worry that much about it. I have the alignment rack printout at home, I'll find it and post the numbers

Boba: The shake is the same on my street wheels/tires and the race wheels/tires (which are perfectly balanced).. I thought of that one too I'm due for some new rear rotors again anyways and I think I'll switch to OEM fronts as well, if they doesn't cure the problem then it'll be time to look into the hubs.. I'll test the runout as well.

Thanks for all the replies so far guys