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post #1 of 5 (permalink) Old 03-18-17, 08:52 PM Thread Starter
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Brake problem

On my 2006 Crown Vic w/110K on it.

It was a cop car from a local department. I bought from the city at auction.

It has a problem w/the brakes. It has never happened to me, but my wife has had problems w/it 3x.

The 1st time, It was possibly wet and she re-ended another car.

I drove it home and had no problems w/it....other than the brake light would come on when you abused the brakes (I abused the snot out of them). We put a master cylinder on it and nothing changed. The shop had no ideas...they seem fine.

Then about 3 months after that, she couldn't stop at a stop sign. We went back to the spot and there was no moisture on the ground or etc....so the ABS should not have kicked in.

The ABS appears to work correctly when it is icy/snowy out.

We had the rear rotors & pads changed as they were grooved and nothing seemed to change.

Some time in there, the brake light was coming on, just for an instance....the 1st thing that the shop checked was the BF level. It was a tad low, they topped it off and they couldn't find anything wrong w/it.

I've never found anything wrong w/the brakes and neither has the shop.

Then, another 3 months go by, or more, and yesterday the wife said that it wouldn't stop. She pumped the brakes, and put it in park (which wouldn't do anything) and it stopped.

All she can tell me is that it won't stop. There are no warning lights on the dash.

The tires are not the same from and rear....Blizzaks in the front and M&S in the back. Before that, it had the M&S in the back and road tires in the front. Then, before that, standard 17" tires on it...I don't know if it had those on it when it had its incidents or not.

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post #2 of 5 (permalink) Old 03-19-17, 04:48 AM
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Re: Brake problem

As they say here Frequently Asked Questions - eiretyres.com

Quote:
It’s important to keep to the same OE (original equipment) tyre size and rolling circumference when fitting new tyres on vehicles fitted with ABS or ASR systems, otherwise this could lead to system failure.
On dry roads block tread mud and snow tyres can also behave a little like bald tyres (sliding more) making the ABS system think that the tyres have lost grip (which they have albeit not a skid situation) invoking the anti-lock mechanism.
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post #3 of 5 (permalink) Old 03-19-17, 04:49 AM
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Re: Brake problem

If the pedal went hard when the incidents occurred , would suspect the brake booster but you would think it would happen more often .Getting the brake system scanned with appropriate equipment wouldn't go wrong even though no lights showing .

Never, never, never give up.
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post #4 of 5 (permalink) Old 03-19-17, 05:28 AM
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Re: Brake problem

" It’s important to keep to the same OE (original equipment) tyre size and rolling circumference when fitting new tyres on vehicles fitted with ABS or ASR systems, otherwise this could lead to system failure. "

Just an aside , knowing this , nowadays a lot of manufacturers only supply a smaller " space saver wheel " as standard spec ?????

Never, never, never give up.
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post #5 of 5 (permalink) Old 03-19-17, 05:36 AM
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Re: Brake problem

Quote:
The ABS appears to work correctly when it is icy/snowy out.
This does point somewhat to the Mud and Snow tyres losing grip on dry road engaging the anti-skid feature so they don't lock on. They will tend to slip both at medium high speed braking but they will also slip a little at initial take off (especially under heavy throttle) so the ABS engages if you then almost immediately brake even at low speed. Perhaps best keep the M&S for winter only driving.

I found similar things with my Australian V8 Ford Fairlane which had a similar weight and drivetrain to the Crown Vic. If I allowed the tyres to get low (but barely legal) tread depth the tyres would no longer have optimal grip and the car would sometimes engage the ABS in unexpected circumstances and take longer than expected to pull up (at least I had an automatic reminder of when to buy new tyres). It did vary with tyre brands and quality so I learnt to invest in better quality tyres.

Snow isn't ever an issue where I live (it never ever snows) so I am no expert on snow tyres although I have driven extensively in snow while holidaying in Tasmania.But my first new car back in the early 70's came equipped with Bridgestone Mud and Snow Tyres (albeit they never saw snow; just mud) so I know how those tyres can behave on hot dry or even just wet tarmac.

Regards Blue
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