Bad shimmy upon heavy braking Toyota 4Runner (why?)

Sounds like rotors, and it sound like you found your problem with that .005 thickness variation spot on the passenger side rotor you described.

Ah, Excellent idea. I didn't think it was the rear only because they have drum brakes and I didn't think brake shudder could be caused by drum brakes (how?).

But this is a good isolation test if it works.

Is this the test:

- Drive on the highway in a safe spot with no traffic

- Press on the brakes (brake shimmy will occur)

- Let up on the brakes (brake shimmy stops)

- Pull hard on the emergency brake

- If the brake shimmy occurs, the problem is in the rear

- If there is no shudder, the problem is in the front

Is that the way to isolate the front from the rear as the cause of the brake shudder?

Stu

SnoMan wrote in news: snipped-for-privacy@4ax.com:

You may be on to something here SnoMan!

I bought the 4runner new and it has over 50K miles on it yet the pads are thick as Ronald Reagan's hair. I was amazed at the condition of the pads given the number of city miles that are on this vehicle (I don't take many long trips so it's mostly around town driving). Maybe my Toyota OEM brake pads glazed something somewhere to cause the brake shudder at highway speeds.

Also, I had not thought about the runout being different when the rotors are hot vs when they are cold. I guess I could drive hard and then quickly stop and remove the wheels and check the runout but probably that is a losing cause as they'd cool pretty quickly I'd think.

I'm getting closer and closer to just replacing the rotors and pads just to see what happens although I don't like just replacing stuff that I didn't diagnose as being faulty. I don't mind replacing faulty parts. But it feels bad to replace good parts just on a whim.

Thanks for the advice. Stu

"Shep" wrote in news:1141136768 snipped-for-privacy@sp6iad.superfeed.net:

Thanks Shep. I did check only one spot since the rotors seemed in good shape visually. That was when I still suspected runout but when I checked runout, it was within spec (0.0028 inches).

In hind sight, I should have mic'd the rotors in multiple spots. I did put a vernier caliper on the rotor but all that did was get the high spot.

I think I'll remove the wheels and mic the rotors in multiple spots again but this time I think I'll remove the caliper (it's only four bolts ... these Toyota 4-piston front calipers are beautiful to work on) so I can get a good spot on the rotor.

Come to think of it, I may as well remove the rotor itself if I remove the caliper as there is nothing holding them on (it's a 2WD 4Runner) at that point. Then I can mic it all over the place.

Thanks for the advice, I know what I'll be doing this Saturday! Stu

"sdlomi2" wrote in news:gOWMf.1994$ snipped-for-privacy@fe06.lga:

When I tried this test to isolate whether the brake shudder is coming from the front or the rear todayI almost skidded out of control. Luckily nobody was near me and the road was five lanes where I tested it.

I guess I should've waited until the roads were dry (I don't have ABS and it's been raining for a while now). I'll try again when the roads are dry.

While I'm waiting, do you guys get your brake rotors and pads and shims from the dealer or do you get them elsewhere? Any recommended Internet suppliers for northern California?

I looked on froogle for pads, hardware, & rotors for:

- 1998 Toyota 4Runner 2WD 3RZ-FE stock everything and I found a WIDE range of suppliers, Brembo, RayBestos, Akebono, EBC, Hawk, etc.

Do you guys go to the dealer for OEM spec brake pads & rotors or do you have a favorite internet supplier I can order from. Which brand do you go for?

Thanks, Stu

Don wrote in news: snipped-for-privacy@4ax.com:

Thanks Don for your advice and thanks everyone else too! I had never thought of these two tests:

- Use the rear brake to isolate the location of the shimmy

- Note whether the steering wheel or just the brakes are affected

After test driving just now I can emphatically say that not only does the shuddering not occur with the rear wheels, but, with all this rain, I would never recommend jamming on the rear brake at speed on the freeway as I skidded sideways more than a few times during my 80 mph tests.

Also, the Toyota high-speed brake shudder DOES affect the steering wheel, although I can feel the front end body of the 4Runner shake with the seat of my pants more than I can feel it in the steering wheel. Still, I can feel the shimmy ever so slightly in the steering wheel. So, now it's time to turn them or replace them. I'm inclined to replace the Toyota rotors as they've got 50,000 miles on them already and that's more than they typically last according to the Toyota dealership when I priced them today.

I hate to buy without knowing what I'm buying. I already know there is no government or private standard for brake pads so they could put toilet paper in there and call it friction material. It's all advertising.

Is it the same with rotors? Is there a government or private standard for rotors that I can rely on (like that of tires, oils, greases, etc.)?

Stu

Scott in Florida wrote in news: snipped-for-privacy@4ax.com:

Based on the Babcox

and PerformanceOil articles, it seems going OEM is the ONLY way. For example, we could go to the local parts store and ask for ceramics and get the exact same pads as someone who asks for semi-metallics!

That makes the local parts store useless from a trust standpoint. It leaves only OEM at the dealership.

For my Nissan, there is one dealership in the USA that stands above all others in garnering the loyalty and trust of those who work on their own cars. This dealership of choice sells Nissan/Infiniti parts for 20% to 40% lower than any other dealership in America (including tax and shipping), and is the dealership of choice that we all partonize. We want HIM to stay in business because he actually cares about US (I've spoken to him many times and he's great!).

Is there a similar Internet dealership of choice who actually cares enough about us in the Toyota/Lexus world to give us the mechanic's discount every day?

Stu