I found out that my 305/55 rears were the cause of the brake hydralic pressure drop when I put my 295's back on the rear and the symtoms immediately left. As I explained before, there isn't a pulsing, just a pedal drop, like the pressure to the rear has been dumped.
Anyone else experience this with this tire combo? Am thinking about disconnecting ABS, not much rain in SoCal.

 

If you are running a different tire height on the rears then that can trigger the ABS. The ABS is designed to monitor wheel speed, and if it sees a wheel going faster than the others, it sees that as the wheel is slipping.

 

I have the same problem and didn't know where it came from. I can live with it but is there any loss of braking power?

 

Definitely an increase in stopping distance with me. I loose rear braking. Where do I disconnect the ABS (fuse)? Will it store an error code? Is this something a tuner can adjust for?

 

Sal - can we do anything about that? Because I really want to put slightly taller tires on the rear of my truck and stock on the front, but not at the comprise of stopping power.


trabuco - I haven't seen you post in ahwile, hows everything been?

 

The guy who designed our ABS systems is an old customer of mine. I'll get with him and find out better info... Stay tuned

 

That would be a big help Sal. Would like to retain ABS.

 

this happens not only with differet tires sizes but also with different gear ratios, happened in my mustangs when I went from 3.27 to 3.73.

I believe the only way to fix it is with a chip, you can program it for different gear ratios. With taller tires and same gears you would have to figure out the closest ratio to program the computer to.

You could also do a gear swap I would think going to 3.73's with those tires would fix the problem that is as long as you own an 00 or 99 (sorry to lazy to look) otherwise some 4.10's m ight help.

EDIT: I see you have an 01 with 55 series tires your adding about 10% to your gear ratio. 10% of factory 3.73 would put you at 4.10 exactly. So installing 4.10's would fix your problem and restore your truck to the factory gear ratio with 55 series tires.

 

ArgentL,

4.10's will put my '01 right back to 3.73's, which is what I plan to do, (this current set-up gives me an effective ratio of 3.40, pretty weak). So if I program for 4.10's, the ABS will be fixed, ( but my speedo will still be off)?

Edit: As I see it, the gear swap will give me my stock ratio and speedo back without reprogramming for the gears, but I will still need to adress the ABS software.

 

If you put 4.10s no chip reprogram will be neccesary, youll be back to factory ratio, speedo will be accurate and ABS will work properly.

 

Thanks, and sorry Argent L about my post editing. I will re-post in the future (you can't be sure what you're answering to with me). Won't the wheel sensors still read a diffenence in wheel velocities front to rear and trigger an ABS condition?

 

nope, the tone ring for the rear axle is on the outside of the diff. carrier. No matter what gear ratio you have, the reading will be the same. It is all relative to the speed of the wheel on the ground, and no matter what , the tires have to be the same diameter for the abs to see them as turning the same speed.

Now, what you are saying would make the speedo more accurate since it is measured at driveshaft speed.

 

droptail is correct

 

Wonder if there is a different tone ring (higher frequency)? Hope there is a solution, hardware or software.

 

Nope, only 1 made to fit the carrier. This type of problem has been going on with mustangs at work since 94. No solution as yet other than run the same size tire.