Wet weather braking (lack of it)
- Thread starter Audijarvis
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can you describe the problem?
If the brakes are working properly, they should easily be able to overpower the tyres in wet weather (and dry if you try hard enough), meaning the braking performance will be limited entirely by the rubbers grip on the road.
This generally means that under heavy braking in the wet, you'd lock up the wheels and the ABS would kick in. ABS activation generally lengthens stopping distances however.
If you cant get this to occur, then your brakes are probably a bit past it. Given you have a 1.6, you'll probably have the unvented 280mm disks on the front, which for a car as big as an A4 is a bit useless. To upgrade you'll need a pair of calipers from a 1.8T or better, and then you can fit the 288x25mm vented disks.
If the problem is the brake lock up far too early, then you need to be looking at better tyres too.
If the brakes are working properly, they should easily be able to overpower the tyres in wet weather (and dry if you try hard enough), meaning the braking performance will be limited entirely by the rubbers grip on the road.
This generally means that under heavy braking in the wet, you'd lock up the wheels and the ABS would kick in. ABS activation generally lengthens stopping distances however.
If you cant get this to occur, then your brakes are probably a bit past it. Given you have a 1.6, you'll probably have the unvented 280mm disks on the front, which for a car as big as an A4 is a bit useless. To upgrade you'll need a pair of calipers from a 1.8T or better, and then you can fit the 288x25mm vented disks.
If the problem is the brake lock up far too early, then you need to be looking at better tyres too.
Audijarvis
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The brakes in the dry are eyeball popping, certainly no problems with the pads, tires or the system.
The problem started when on the motorway in a down pour and continued until the roads dried up.
Basically, when approaching junctions, roundabouts etc, I found I had very little braking power until the discs were cleared of water, then as has been pointed out, the brake comes in so strong its easy to lock a wheel.
I think whats needed is a shield to prevent the disc becoming water logged in the first place
That or I'm going to have to change my driving style and learn to drive around the problem
The problem started when on the motorway in a down pour and continued until the roads dried up.
Basically, when approaching junctions, roundabouts etc, I found I had very little braking power until the discs were cleared of water, then as has been pointed out, the brake comes in so strong its easy to lock a wheel.
I think whats needed is a shield to prevent the disc becoming water logged in the first place
That or I'm going to have to change my driving style and learn to drive around the problem
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the pads sit less than a few thou from the disk, and really should be clearing the water off as the disk rotates normally.
Perhaps you have one or more worn wheelbearings, allowing the caliper pistons to get knocked back?
Perhaps you have one or more worn wheelbearings, allowing the caliper pistons to get knocked back?
Its a common failing due to poor splash gaurd design on the front brakes. IIRC there is a larger sheild that you can use thay encases more of the rear of the disc to preven them getting too much spray on them.
I used to have this withe the 280s, but wehn i went 288, i also changed the shields and that cured it,it also stayed away when i went 312, as i kept the same shields.
I used to have this withe the 280s, but wehn i went 288, i also changed the shields and that cured it,it also stayed away when i went 312, as i kept the same shields.
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i ran no splash guards on my previous cars, and the A4 hasnt been modified and theres no scary "oh crap theres no brakes" moments...
I deffo had it on the SET before fitting the larger splash gaurds.
Maybe it was one of the other components i changed, but thats what i put it down to.
I havent checked this car to see if it has the little credit card sized gaurd or the full size one
Maybe it was one of the other components i changed, but thats what i put it down to.
I havent checked this car to see if it has the little credit card sized gaurd or the full size one
Audijarvis
Registered User
Where can I get a set of these guards?
aragorn
I here what your saying about the bearings pushing back the brake pads, my bike has fully floating discs and this can be a issue on high speed bump ridden roads (that'll be most of them then) although I will say that on the bike you will loose the brakes wet or dry until you pump the lever to set the pads against the disc.
Going to give the brakes a look over at the weekend and treat the pins to some copper grease
Site issue. Is everyone having trouble getting on the site tonight, been difficult to logon
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I suspect it might just be a flaw with the smaller calipers, as they're a different design to the larger ones.
Mark had it with his 280's and it went away when he upgraded, but i'd put money on the fact that his current car wont have the upgraded guards, yet they're fine....
i'd be getting some 288's!
Mark had it with his 280's and it went away when he upgraded, but i'd put money on the fact that his current car wont have the upgraded guards, yet they're fine....
i'd be getting some 288's!
If all else fails a have a set of 288mm calipers,discs,half decent pads etc from a 2003 Passat, direct bolt on.
I have no gaurds front or back, never had a problem with wet braking because of it
that said I have some RS4 brake guards if you want them, yours for postage!
that said I have some RS4 brake guards if you want them, yours for postage!
Audijarvis
Registered User
Thanks
Will pm you tomorrow
Audi obviously new there was an issue.
There's little detail in the link bellow other than a description of how they've up graded the brakes on some of the latest models
http://www.audi.com.sg/sea/brand/sg/models/a5/a5_coupe/audi_a5_3_0_tdi__quattro.html
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Sounds like a load of crap to me. Useful way to wear out brake pads/disks in cars that do a lot of motorway mileage though....
If there is "obviously" an issue, why does no-one on here with 288's have the same problem? Even jcb's positively huge 360mm disks with no guards dont have a problem, and he lives in scotland, where it rains a lot.
If there is "obviously" an issue, why does no-one on here with 288's have the same problem? Even jcb's positively huge 360mm disks with no guards dont have a problem, and he lives in scotland, where it rains a lot.
Audijarvis
Registered User
I've a theory on this
As we've just come out of a particularly bad winter we've been gentle on the brake pedal trying to keep the wheels from locking. Now the weather has picked up we still are being quite tentative with the pedal, slowing the rate at which the film of water is cleared from the surface of the disc.
I could be wrong of course but the next time it rains I'm going to stamp on the brake pedal and see what happens
Audijarvis
Registered User
Looks like my theory was correct, well the heavy wet weather braking worked for me.
Still, I don't see why I should need to put so much effort into stopping but I guess that's just all part of the A4 experience!
