Tough Brakes Questions

07 Expedition. At 1,800 miles the truck started pulling to the left while braking at freeway speeds. New front pads, nothing. New rear pads, nothing. Rode with engineer who said while braking/pulling the
driver side rear tires is spinning 3-5mph slower than the rest, causing the pull. They then replaced both rear calipers, pads, rotors, and lines. Still pulls the same. Any ideas?
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snipped-for-privacy@hotmail.com wrote:

Take it back to the dealer.
It might even be the computer that controls the ABS.
Jeff
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It could also be a tire causing it. KB
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Ditto that. If the computer told the engineer that the RIGHT side is going slower, but it pulls LEFT then it could be a bogus reading causing the ABS modulator to ease up on the right side. Your wheel speed sensor is probably good since it reports okay while not brakiing, which means the bad data are appearing higher up the chain.
Calvin
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No, the driver rear tire is going slower.
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On Oct 2, 11:56 am, snipped-for-privacy@hotmail.com wrote:

Yeah, but how do you know that? Because the computer says so? Maybe the computer is wrong. Unless you put your own counter on the wheel you have to take the computer's word for how fast each wheel is spinning.
Calvin
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Well true, but it makes sense. If the left rear wheel has more braking power than the rest, it would pull to the left.
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On Oct 2, 1:23 pm, snipped-for-privacy@hotmail.com wrote:

The right wheel having less braking power would also make it pull left. The ABS can't increase braking power beyond what you input, but it can reduce it.
I'm not trying to argue with you, which I hope you see. I'm just trying to think out loud about other options.
Calvin
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No harm. This problem happens even when the ABS was disconnected.
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wrote:

A dead simple way to see if it's ABS. Discommect the darn thing. However,I'm betting it's NOT ABS. I'd be checking tires first (switch left to right and see what happens) I'd also do an ACCURATE 4 wheel alignment to rule out alignment issues, and check the suspension integrety to be sure the rear axle is not shifting under braking. I'd also be checking the brake hoses. Particularly on the front. Rear brake inbalance rarely causes a "simple" pull. Premature locking of a right rear wheel is just as liable to cause a drift to the right as a pull to the right.
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On Oct 2, 6:48 pm, clare at snyder.on.ca wrote:

I really think it is a caliper or valve failing when it heats up. All four tires have been ruled out as they have been rotated in every position. Suspension has been checked.
The pulling doesn't happen on the first hard brake. It is the braking after that that it gets progressively worse up to a point, which leads me to believe its heat related. Alignment is dead on.
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On Mon, 01 Oct 2007 15:19:58 -0700, snipped-for-privacy@hotmail.com wrote:

I have a '93 F150 that had a similar if not identical problem. Ford spent something over $7K under warranty attempting to correct the problem. They finally offered to buy it back under the lemon law. We worked out an extended warranty agreement since the buyback on a vehicle with high mileage at the time was prohibitive. Soon afterward, I did a front brake job and replaced the front calipers with recon units partly because one was weeping a trace and partly because this was the only components that were not replaced by Ford in their attempts to correct the brakes. The problem was immediately corrected with the recon calipers and has not returned in more than 150K miles since. I still have the original calipers ans we were never able to detect any abnormal conditions. The curious thing is that the first stop leaving home never had the problem but, if it had been cruising at highway speed for a few minutes, you had better have a good grip on the wheel or it was headed for the wall in a hurry. IT also had an almost imperceptible pull with no brake application. It was wearing my ass out to drive a full day and I had not realized I was constantly correcting and steering against it. It did require a wheel alignment afterward to take out the adjustment the front end man had dialed in to counter the normal steering pull.
Also, someone mentioned a rear wheel turning slower than the other. For that to actually happen with the vehicle traveling straight ahead, one tire has to be larger than the other by a significant and measureable amount. The slow wheel would be the larger in that case and would provide less braking effect than the smaller one. IOW, it should pull toward the faster wheel if that is the problem.
Good luck
Lugnut
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Yeah, I suspect it will turn out to be the front rotors and or calipers. But I can't tell them what to replace.
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