Vibration When Braking.. Out of Round Feel In Brake Pedal??

04e46conv · 01-20-2008, 08:12 PM

Hey Guys,

I am getting a vibration in the front end when braking over 40-50 MPH then when I brake at low speeds I am getting an out of round feel in brake pedal??

so when I take the truck out of gear and cost at 35 MPH when I apply the brake the car slows then theres a little "lump" or out of round feel behind the pedal and the truck continues to stop and drops more speed when hitting the "lump" or out of round feel and then repeats until I have come to a complete stop...

I just installed my Avic D3 and I am thinking that I might have messed something electronic up when working around the ECU I tool my XM unit and Velcro it to the side of the ECU so I wounder if they are messing with each other and might be affecting the ABS system?? But when I brake I don't hear any relays click like a system is coming on...

So I think that cancels that problem out plus I prob would have thrown a code and lit some light on the dash right?

Any Ideas??

Gadget · 01-20-2008, 08:26 PM

You likely have warped rotors and need to have them turned or replaced.

Gadget

**FJVP** · 01-20-2008, 08:33 PM

Quote:

Gadget previously said:

You likely have warped rotors and need to have them turned or replaced.

Gadget

X2.....

04e46conv · 01-20-2008, 08:35 PM

Forgot to mention I have 5200 miles on the truck... if its a rotor it must be defective....

BamBam · 01-20-2008, 09:00 PM

Have you taken a wheel off? I have seen guys over torque lugs and have it screw up their rotors (warping). That would give you that feel. Or they take off the rotors and put them back on slightly crooked and crank the wheel down.

You might also want to check and make sure you don't have a high spot on a rotor, or some brake dust or other crap trapped in there. Blast your wheels out good with a pressure washer (like at a do-it-yourself car wash) and see if it dislodges anything.

k44 · 01-20-2008, 09:26 PM

Couldn't tell by your description just what an "out of round feel" is.

Sounds like you're braking and decelerating normally from 35 mph, then the pedal does some weird vibration at about 30 mph, then you continue braking and it's back to normal till you get down to maybe 20 mph and the brake pedal vibrates again, and smooths out again, and then you finish the stop?

Maybe your vehicle speed sensor is hooked up to the wrong wire and you're overloading that part of the ECM and it's having trouble figuring out how fast you're going. While it's confused it might be activating ABS or ATRAC or something.

***Bostonian1976*** · 01-20-2008, 09:39 PM

Yeah warped rotors. Can easily be caused by not equally torquing each lug nut

04e46conv · 01-20-2008, 09:52 PM

Quote:

BamBam previously said:

Have you taken a wheel off? I have seen guys over torque lugs and have it screw up their rotors (warping). That would give you that feel. Or they take off the rotors and put them back on slightly crooked and crank the wheel down.

You might also want to check and make sure you don't have a high spot on a rotor, or some brake dust or other crap trapped in there. Blast your wheels out good with a pressure washer (like at a do-it-yourself car wash) and see if it dislodges anything.

I haven't removed a wheel yet it been at the dealer once for an oil change so they shouldn't have removed any wheels..

Quote:

k44 previously said:

Couldn't tell by your description just what an "out of round feel" is.

Sounds like you're braking and decelerating normally from 35 mph, then the pedal does some weird vibration at about 30 mph, then you continue braking and it's back to normal till you get down to maybe 20 mph and the brake pedal vibrates again, and smooths out again, and then you finish the stop?

Maybe your vehicle speed sensor is hooked up to the wrong wire and you're overloading that part of the ECM and it's having trouble figuring out how fast you're going. While it's confused it might be activating ABS or ATRAC or something.

When I am at any speed it does it but what I have been doing to try and diagnose it was get up to 30-35mph and take it out of gear and just coast then apply the brakes about an inch or too and keep my foot in the same spot and i get the feeling... the feeling is smooth then a bump smooth then bump and its constant so the faster i go the faster the bump comes around...

When I go to the settings on the Avic D3 head unit and click the vehicle Speed Signal Wire Test it is reading the same speed the car is traveling so I assume it is hooked up correctly..

JDMSi92 · 01-20-2008, 10:31 PM

x8 on warpped rotors. Not to be rude but its more than likely caused from excesive braking or riding of the brakes. The FJ is heavy and it would not be difficult to heat them up to the point to where they can warp. If the rotors have hot spots in them from getting way to hot, then you will need to replace them. I don't think the dealer will give you new rotors but they may warrenty a turning of the rotors.

BamBam · 01-20-2008, 10:48 PM

Interesting thought here..... you haven't had the wheel off, and the dealer hasn't, but it very easily could have happened when they put the wheels on. All you need is one joker to torque a lug wrong when putting on your wheels at assembly (or if they put the nice wheels on at the port or at the dealership).

A good lesson is to always hand torque your lugs with a torque wrench right to factory specs. I've seen a few clowns at the dealership put on accessories with an impact wrench and totally spin things down way too hard. I was reading here that some guys have had problems with the roof rack being too tight. Chances are somebody along the line did the same thing with your wheel. It was probably that way from day 1, you're just noticing it more and more as it gets more and more warped because of the expansion and contraction of braking.

I had a similar problem on a Mitsubishi. I swapped out the rotors on the front and always demanded that they hand torque the lugs on rotations and never had a problem again.