So the tires screech when I slam on the brakes. This is the 2nd time. Is something wrong with my ABS? Shouldn't it pulsate?v I have Toyo Proxis 4's. Its under warranty. Will the dealer charge me if they don't find anything wrong with it. Thanks!

 

On other vehicles that I own when I step on the brakes that hard (which is rare) there is a bit of tire screeching drama before ABS kicks in. (The ABS doesn't know to engage until the tire has stopped spinning and the car is still moving.) Once it engages, you'll know it likely by the sound. I don't think that I've ever had it engage on the F-T.

 

Just because you're tires screech does not mean you've locked them up. Also when ABS engages you'll still have tire squeal, because 3 wheels are locked up at any one time, thus the pulsation.

If you take it into the dealer and find nothing wrong under warranty, generally they will not charge you.

 

That not quite how ABS works. ABS uses wheel speed sensors to determine if one or more wheels are trying to lock up during braking. If a wheel tries to lock up, a series of hydraulic valves limit or reduce the braking on that wheel. This prevents skidding and allows you to maintain steering control. This is done on an individual wheel basis. The computer does not wait for 3 wheels to lock up.

 

Hmmm. Stohlen is an automotive engineer, and Unhinged is the resident Jedi master. Interesting to see where this goes.

 

If you look at tire marks from max pedal application with ABS braking, it will look something like:

= = =
= = =

If you look at tire marks from non-ABS braking, it will look something like:

==~
==~

So yes, technically ABS allows wheels briefly to lose traction and pulses braking to unlock them before it produces skid. However in everyday use locking refers to skid (~) part and not (=) part that preceded it.

I also agree with Unhingd, the ABS control system on F-type is quite advanced and is independent on each wheel. At least on my car equipped with vectoring it is. I have seen evidence of that when I overcooked with threshold braking, few puffs of smoke from rear wheels and the car turned me in and bailed me out from a bad situation. For that ride I was just a loose nut behind steering wheel - it was all car.

I also can confirm that tires will screech with ABS during (=) phase. They will screech more without ABS, as (==) is longer and without operator input (manual pulsing) is longer.

 

Yes, I agree these systems act on an independent basis, but the wheels have to achieve lockup prior to activating ABS. Once that occurs the oscillation of the ABS is so fast braking force looks more like a sine wave, than a step force. This keeps the wheels as close to the threshold of lockup as possible and usually causes 2-3 wheels to be locked up at any one time; but because the locked up wheels are moved so quickly from corner to corner, steering (while reduced from standard) remains.

Granted I've not researched Jaguar's specific system, but this is how most of the systems we use work.

 

Yes, this is the way I understand ABS systems to work.

 

There has to be some skidding... that's how abs works. Basically the car threshold brakes but by rapidly modulating.
It shouldn't be excessive like what you hear with full lockup, however. Also exactly what Stohen said. I suspect it is behaving normally, but you could record a video with sound and share.

 

This happened to me a few weeks ago as well...I was very surprised. It's the only modern car I have had where I was able to lock up the wheels. This happened on the freeway with what I would call moderate "panic" braking. I wonder if it's a tire problem or a brake problem.

 

I would not take the car into the shop over squealing tires. That is normal on most tires as they approach the limit of what they can handle. Heat and noise are the byproduct of the massive amount of friction the tire is trying to absorb. If your car didn't weigh as much, it would probably squeal less

 

Obviously if the tyres were to screech when you accelerate as well as brake hard you should take the car to the dealership and ask them to check the nut that's behind the steering wheel. If there's something wrong with this it can adversely affect the performance of the car in general.

HTH