hard shimmy on the downhill when braking???

So I have done some research into this issue since my first post..... when the brake shimmy happened for me there were 2 things that I noticed, I had the shimmy, and I had some brake fade. Brake fade is cause by 2 things... brake material gassing and/or brake fluid boiling. The shimmy can be caused by the gassing and venting but it is more likely thermal expansion of the rotor from the heat. Since I only experienced it at highway speeds in mountain downhills, both events seem very likely. I regularly inspect my brakes and I have no runout issues, no glazing, heat checking or cracking. I also have a manual transmission and use engine braking to lighten the load on the brake system. So, I have always felt the issue is the undersized rotors that Toyota put on the Tacoma. For me, the solution that makes the most sense is upgrading to 4Runner front rotors. This will provide a larger thermal sink and improve braking under highway speed, downhill conditions.

Just for reference, the Tacoma rotor is 10.75" in diameter while the 4Runner rotor is 13.3" in diameter according to 2017 Toyota Products Specification literature. That is a significant increase in rotor size. The only possible downside to some would be the need to run 17" or larger wheels to accommodate the larger rotors. Something I had already planned on when purchasing my new wheels.

 

You're going to need more than just 4runner rotors to make it work.

I'm going to eventually just get this:

https://www.extremeterrain.com/powe...tow-6lug-brake-pad-kit-front-0519-tacoma.html

If you are worried about overheating

You can swap out the rubber lines for steel braided lines so that the fluid doesn't expand the rubber lines and you then lose brake pressure on the pedal. You can swap fluid out for fluid that has a higher boiling point as well.

 

You are right, I will need more than just the rotors. I understand that.

I will be using this guide: https://www.tacomaworld.com/threads...unner-bbk-upgrade-for-2nd-gen-tacomas.504234/

I also prefer the factory swap over aftermarket for 1 reason. If I travel anywhere, and I have an issue with some brake component, I would rather have parts that will be readily available at most parts stores vs. something that would have to be special ordered.

 

I notice the same symptoms under hard-ish braking on the new to me 12k mile TRD OR DCLB. Feels like it’s coming from the rear, not typical front rotor warp.

Light braking doesn’t encourage it to happen, harder braking does and going downhill makes it happen easier with even light braking.

Just bought this truck and am already annoyed that I’m having similar issues as I did in years of owning my second gen.

 

I get the vibrations (feels like the rear) during "medium" braking around 40 mph.

 

If you feel it in your foot it's the rotors . Otherwise I'd look elsewhere.

 

i got this the other day after going through a car wash. decelerating from 55 to a stop it happened at about 40 mph... i think maybe the drums got wet or something because the brakes are fine 99% of the time.

 

I'm curious to know if you've discovered the real issue and what it is/was?

 

If the vibrations feel like they are coming from the body of the truck, could it still be the brakes or should I be focusing on suspension? I don't notice any vibrations in the pedals or wheel.

 

Go faster, shed that water with speed.

 

It could be drive line vibrations in the rear or if your lifted and 4wd the clamshell bushing . You may have flat spotted tires or be out of balance also . Just a couple places to look . I hope it helps .

 

Took it in for my last free oil change and mentioned the vibrations to the service rep. They found some run out on one of the front rotors and resurfaced it under warranty. Drives great now

 

oh ok