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Wobble during high speed braking
https://forums.tipec.net/viewtopic.php?f=25&t=18877
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Author:  benjj [ Fri Nov 14, 2014 9:56 am ]
Post subject:  Wobble during high speed braking

Gents,

I've got some time to address a few issues on the 944 over the weekend. The first thing is to sort the wobble.

Anyone got any ideas where best to start diagnosing the issue?

Issue: big wobble felt through wheel when hitting the brakes (hard or medium) from higher speeds. No wobble without brakes applied. No wobble on brakes at lower speeds (pottering in town etc.)

I'm pretty sure it isn't a warped disc or issues with the brakes themselves.

The majority of the front suspension is Powerflex polybushed so unlikely a warn bush.

Am thinking along the lines of a failed balljoint.

Any suggestions most welcome.

Cheers,

Ben

Author:  EDDIE [ Fri Nov 14, 2014 10:25 am ]
Post subject:  Re: Wobble during high speed braking

discs or stuck/sticking pots in calipers.

Hope you get it sorted.

Nick

Author:  tr7v8 [ Fri Nov 14, 2014 11:04 am ]
Post subject:  Re: Wobble during high speed braking

EDDIE wrote:
discs or stuck/sticking pots in calipers.

Hope you get it sorted.

Nick

This, quite common on 944s. Make sure that the hubs are 100% clean before you replace the discs

Author:  benjj [ Fri Nov 14, 2014 11:13 am ]
Post subject:  Re: Wobble during high speed braking

Thanks chaps, will have a good poke around.

Calipers had a full rebuild before last rally, could be a sticking piston though. Will get under there and have a look see.

Author:  scam75 [ Fri Nov 14, 2014 11:24 am ]
Post subject:  Re: Wobble during high speed braking

As they have all said. I had the same issue, new discs and a good clean of the mating surfaces sorted it eventually.

Stuart

Author:  broady_6 [ Sat Nov 15, 2014 9:44 am ]
Post subject:  Re: Wobble during high speed braking

Wheels gone out of balance? A lock up during braking can cause that

Author:  Brett928S2 [ Sat Nov 15, 2014 7:52 pm ]
Post subject:  Re: Wobble during high speed braking

Hi :)

Agree with the above post...... Brakes OR Wheel balance.....

All the best Brett :)

Author:  white944 [ Sat Nov 15, 2014 8:22 pm ]
Post subject:  Re: Wobble during high speed braking

Almost certainly brake discs. Wheel balance would not cause shake under braking only.

Author:  Brett928S2 [ Sat Nov 15, 2014 10:04 pm ]
Post subject:  Re: Wobble during high speed braking

white944 wrote:
Almost certainly brake discs. Wheel balance would not cause shake under braking only.



Hi :)

As an ex race mechanic, I can assure you it can.....

Also easy to check and fix BEFORE expensive brakes.....

Imagine he changes the discs and pads and its still there.....

If he has the same size wheels front/back... he just swaps them....if problem vanishes...its balance..if still there...brakes or suspension....

All the best Brett :)

Author:  944 Man [ Sun Nov 16, 2014 2:20 pm ]
Post subject:  Re: Wobble during high speed braking

Untrue discs (fitting, not the discs themselves which don't warp) - less likely.

Build up of material on pads, probably due to incorrect bedding in - quite likely.

Author:  benjj [ Sun Nov 16, 2014 5:52 pm ]
Post subject:  Re: Wobble during high speed braking

Cheers gents.

Might go and put them through a spirited cycle to confirm or write off pad deposits.

Have the knobber winter wheels going on shortly so that'll count in/out balance.

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