17 replies to this topic

[Brams96]

What would be the most likely cause of vibrating under braking? There is only a standard brake master cylinder with no assisted servo, it's got poly bushes on the tiebars & lower arms and running 6x12" minilites. Would it be the brake discs themselves or should I be looking at things like the track rod ends, swivels etc??

[L400RAS]

Warped discs or sticky piston in the caliper get my vote

[matthew_leech]

My mini juddered when braking when I first got it. You couldn't feel it through the steering wheel, it turned out to be the nuts that hold the damper to the radius arm were very loose!

[Brams96]

Another question: When changing to from the old tin vertical mounted master cylinder to the more modern assisted servo type what difference is there in the pedal linkages? What parts do I need other than the servo itself and the main bracket?

[Dan]

Poly bushes on the tie bars would be a prime candidte for the cause, what poly bushes have you used? If they are too hard they cause this kind of juddering and eventually cause the end of the bar to snap off.

[Brams96]

Not sure what type they are but they are orange, installed by the previous owner. I was actually going to change them anyway as there are poly on the inside & outside of the mount point, which I know is a no-no. I have some rubber bushes to replace the outside ones but will keep the inside bushes on. Once the engine is back in I will check & recheck every nut, bolt & bush when the suspension goes back together. Anything else I should check?

[Dan]

I'd check that the dreaded previous owner hasn't also fitted poly to the bottom arms, possibly the worst place to use it on a Mini. It just deforms plasticly very rapidly and then isn't doing anything. Fitting rubber to half of the tie bar bushings is a good start but since you don't know the grade of the orange poly, and given that contrary to popular belief poly has a very short service life on a car in certain locations (which is one of the many sensible reasons that manufacturers don't use it for suspension bushes) I'd be tempted to swap it all out. Mini Spares sell a pack that is ideal for the bushes of a road car which has a harder than standard rubber bush for the outside and a softer than normal poly (still harder than rubber) for the inside. You might well find this will solve the braking judder. You might also find that the ends of the bars snap off when you go to undo them so don't do it when you need to use the car shortly after!

[Tommyboy12]

Could just be a warped disc. They do happen. Best bet is to check them with a steel rule first before you start replacing things.

[wardyxxx]

+1 to the warped disc.

[mini93]

check behind the flanges, where the disk bolts to it, if theres any corosion on that face it can cause vibration.

just had it on my peugeot and fixed alot of the juddering thru taking a wire wheel grinder to the surface

[Mini Mad Drakeley]

my vote goes for the warped disc, my mates polo has the juddering on a warped disc lol

[mini wannabe]

my vote goes for the warped disc, my mates polo has the juddering on a warped disc lol

you would know if its warped disc,s as it sometimes travels through the brake pedal too causing it to move up and down..............

[Jacko-lah]

Could just be a warped disc. They do happen. Best bet is to check them with a steel rule first before you start replacing things.

Mine turned out to be the drive shaft flange, and wheel bearings all being knacked so that there was 2-3 cm free play on the wheel which was effectively being held on by the pads and the disk. Luckily the drive to the flange from the CV joint stopped being driven (as the whole thing was goosed) so I was forced to investigate. Whilst I was repairing it I realised that 2 of the ball joints were functionally difficient too.

[1984mini25]

I'd check that the dreaded previous owner hasn't also fitted poly to the bottom arms, possibly the worst place to use it on a Mini. It just deforms plasticly very rapidly and then isn't doing anything. Fitting rubber to half of the tie bar bushings is a good start but since you don't know the grade of the orange poly, and given that contrary to popular belief poly has a very short service life on a car in certain locations (which is one of the many sensible reasons that manufacturers don't use it for suspension bushes) I'd be tempted to swap it all out. Mini Spares sell a pack that is ideal for the bushes of a road car which has a harder than standard rubber bush for the outside and a softer than normal poly (still harder than rubber) for the inside. You might well find this will solve the braking judder. You might also find that the ends of the bars snap off when you go to undo them so don't do it when you need to use the car shortly after!

I’ve had Polly (yellow) bushes on the bottom arms and tie bars of the daily 25 for years and I’ve NEVER had any juddering problems.
I'd be going with warped brake disks, if they are old, thin or over worked you can easily warp them.

[GTIAlex06]

Checking everything...its the only safe way