Steering wheel shake when the car is warm.

[zimmerDN]

I have a problem with the steering wheel shaking like when the car has warped rotors. When I apply brakes at speed exceeding 50mph the steering wheel would start pulling left & right.

However, this only happens when the car has been driven for a while and everything is warmed up.

I don't know how temp is related to the cause but I suspect it has to do with the brake fluid being warm. Why would I say that? Because I have driven the car at high speed for 2+ hours without using the brakes once and the first time I used it the steering wheel would shake. Also I found some sign of oil leak from the master cylinder but the dealership says it's normal because it's only seepage. What a bunch of #@$%! huh, I hate dealership mechanics.

So my question is, what is an easy way to tell if the rotor is warped without having to remove the rotor? If I know the rotors aren't warped then I can bring the car back without having to worry being charged.

There are also grooves forming on the pass. side of the front rotor. Could this have an affect?

 

[porcupine73]

Yep, you can measure the disc warpage (runout) without removing the disc by using a dial indicator with a magnetic base. This is how the OE service manual says to do it. You can get these items CHEAP at Harbor Freight, like $7 for the indicator and maybe $11 for the magnetic base, compared to easily $100 for each for a Starett (though they are nice!).

Anyway there a lot of things that can cause shaking like that, a good front end shake down to check for loose components might be in order.

 

[Tosh]

I'm becoming more and more a believer in the pad material transfer theory as put forth in this stop tech article.
It seems my 'warp' comes and goes, leaving only such a scenario as a plausible explanation. Apparently, more aggressive pads will cure it. I am a little sceptical about improper bedding in of new pads being the cause, though.

 

[Shannow]

Tosh,
there's a little more to bedding in than matching profiles.

One of the great Oz race teams in the early 70s found that instead of light and heavy braking with the car to season the pads in an unscientific way, they would use an old flywheel machined to thickness, mount a caliper to it, get the flywheel near red hot, then clamp the pads to the hot metal.

An "ash" line would progress from the hot face through the pad. When it was half way through (about 1/4"), they'd dismount the pad, and keep it to swap in during the race..."preseasoned"

 

[Trav]

You may also want to look at the caliper pins,sometimes the rubber boots get a bit tired and moisture gets in causing them to rust,sometimes so severely the caliper will freeze.When the brakes get warm parts expand and the inner pad maybe applying pressure on the rotor,if one pad is worn more than the other this is a good indication.As posted a dial indicator is the only accurate way to check the run out,when mounting new rotors its important to wire brush the hub face to make sure there is no buildup,this will cause immediate run out issues.

 

[tomit]

ZimmerDN,

I'm with porcupine73 on doing your own runout checks. If your car has rear disc brakes, check the runout on them also.

You can use the dial indicator to shift the rotor in relation to the hub to minimize runout. If a rotor has dark spots on the braking surface, I would replace them.

Good luck!

Tom

 

[Gary Allan]

Let's make sure we're getting the true story here. Is the wheel wobbling (steering) or is the car truly PULLING left and then right. One you are not changing direction ..the other the car physically turns.

The reason that I ask is that at low speeds a seized caliper can go unnoticed ..at high speed ..probably not. Now naturally the vehicle may/will "PULL" and then, when released, PULL the other way. The same can be due to kinked or restricted brake hoses ..but that's due to the phase difference between application and release with the delay due to the restriction.

Just making sure that we're on the same page. CV joints can also be an issue in wheel vibration ..but your temp requirements are, perhaps, clouding the diagnosis.

 

[zimmerDN]

Hey guys I turned one of the front rotors and now the car is running great again. I have no idea why this problem was temp related but it was.

Thanks for the advice.

 

[ChrisW]

a leaking master cylinder is a leaking master cylinder, bar none. there should be no seepage; seepage is still a leak, it means that one of the rubber cups on the piston is worn and bypassing fluid inside the cylinder.

 

[Tosh]

Quote:

---

Tosh,
there's a little more to bedding in than matching profiles.

One of the great Oz race teams in the early 70s found that instead of light and heavy braking with the car to season the pads in an unscientific way, they would use an old flywheel machined to thickness, mount a caliper to it, get the flywheel near red hot, then clamp the pads to the hot metal.

An "ash" line would progress from the hot face through the pad. When it was half way through (about 1/4"), they'd dismount the pad, and keep it to swap in during the race..."preseasoned"

---

I agree that some racing compounds need burning-in, as you describe, Shannow. But on my 2001 CL-S, these are factory Acura pads on new Acura OEM rotors, and the directions are to brake gently for the first 500 (right?) miles. There is no mention of repeated 60-5 MPH stops to burn in these pads, like on some Repco pads for another car. And now, at 33k miles on this second pair of front rotors (dealer repl rotors and pads under warranty at 48k after cutting first pair at 34k), they've become worse, just like the first set. I will borrow an indicator and mag stand next to measure runout.