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Wet weather braking (lack of it)

Discussion in 'A4/S4 forum(B5 Chassis)' started by Audijarvis, Mar 22, 2010.

  1. Audijarvis
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    Audijarvis Member

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    [Mar 22, 2010]
    Are B5 brakes all terrible in the wet and if so is there an easy fix?
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  3. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Mar 23, 2010]
    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.
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  4. olds_kool
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    olds_kool Active Member VCDS Map User

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    [Mar 23, 2010]
    ive got some 1.8t calipers and carriers if you want them
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  5. jcb
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    jcb Active Member VCDS Map User

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    [Mar 23, 2010]
    mine were pants wet and dry,
    no danger they could lock up in the dry after a while
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  6. Matt82
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    Matt82 Active Member

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    [Mar 23, 2010]
    jarvis

    brakes or tyre problem? give us a clue!
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  7. Audijarvis
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    Audijarvis Member

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    [Mar 23, 2010]
    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
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  8. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Mar 23, 2010]
    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?
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  9. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator VCDS Map User

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    [Mar 23, 2010]
    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.
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  10. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Mar 23, 2010]
    i ran no splash guards on my previous cars, and the A4 hasnt been modified and theres no scary "oh **** theres no brakes" moments...
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  11. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator VCDS Map User

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    [Mar 23, 2010]
    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
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  12. Audijarvis
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    Audijarvis Member

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    [Mar 23, 2010]
    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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  13. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Mar 23, 2010]
    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!
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  14. Broken Byzan
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    [Mar 23, 2010]
    If all else fails a have a set of 288mm calipers,discs,half decent pads etc from a 2003 Passat, direct bolt on.
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  15. jcb
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    jcb Active Member VCDS Map User

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    [Mar 23, 2010]
    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!
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  16. Audijarvis
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    Audijarvis Member

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    [Mar 24, 2010]
    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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  17. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Mar 24, 2010]
    Sounds like a load of **** 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.
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  18. jcb
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    jcb Active Member VCDS Map User

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    [Mar 24, 2010]
    we invented rain!!
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  19. Geeman
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    Geeman Low Life

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    [Mar 26, 2010]
    I experienced this last night on the way home from London in hard rain/spray on the M25/A1 - It can be a little disconcerting at times!
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  20. Audijarvis
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    Audijarvis Member

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    [Mar 26, 2010]
    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
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  21. Audijarvis
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    Audijarvis Member

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    [Mar 29, 2010]
    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!
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