How to change front discs e85 / e86

[mattimus]

Hi, I have wheel wobble when heavy braking, and when slowing right down the brakes ‘catch’ then release, like a slow-mo ABS.
So I intend to change the front disks and got a good deal on the pagit disks kindly posted about on here a few weeks back.
I’ve searched on the forum for a how-to and have found snippets of info but nothing comprehensive, can anyone point me at a good write-up please?
Cheers!

 

[plenty]

Sounds more like a sticky caliper than bad discs. Check the wheels after a drive - if one is especially warm, that'll be the caliper.

 

[enuff_zed]

[ref]mattimus[/ref], where are you? I’d be happy to help you fix it and ‘supervise’ you through what is in fact a very easy job.
However, I too suspect it sounds like a sticking calliper

 

[mattimus]

Thanks both.

I’ll check for a hot wheel / brake after my next trip!

Alas I’m near York, so far from your neck of the woods enuff_zed - very kind of you to offer though

 

[colb]

The symptoms you have could well be warped discs, to measure the run out you really need a Dial Test Indicator guage to see if they are warped. Alternative is to have a helper press the brake whilst the wheel is jacked up as you spin the wheel. When the brakes are released the caliper pistons should be retracting as the pressure is released and the pads move away from the disc. If you find they are tending to stay on then give some attention to the sliding pins of the caliper these should be smooth in operation and lightly lubed with suitable grease, dust shields should also be intact.A good clean of the flat areas the pads slide on and a smear of copper grease on the sliding surfaces wouldn't go amiss. The actual caliper pistons can also seize in their bores usually a tell tale sign is the wheel centre getting hot after a drive and braking. Repair kits are available for the calipers but probably best to obtain replacements if your not sure on how to go about a refurb.

 

[raymond.harper]

https://www.pelicanparts.com/techarticles/BMW_Z4M/91-BRAKES-Brake_Rotor_Replacement/91-BRAKES-Brake_Rotor_Replacement.htm

 

[smorris_12]

I’ve searched on the forum for a how-to and have found snippets of info but nothing comprehensive, can anyone point me at a good write-up please?

No idea on that score specifically but the braking arrangement is the same for any (ordinary) BMW in the last 30 years and almost every other car on the road. Have a search for DIYs on E46 or E90s; you shouldn't be able to throw a stick without hitting 3 well illustrated write-ups that are basically the same as the Z4.

 

[Lynchy]

Search on YouTube, I’ve found it to be very useful

 

[mattimus]

Checked the temperature of the wheels after a long run with a bit of braking today - all cool.
In fact all 4 discs were very roughly the same temperature (according to the backs-of-my-fingers thermometer).
Given the steering wheel wobble only happens when braking at high speed, and then vanishes the instant I stop braking, makes me think that changing the discs anyway, but examining the condition of the callipers in the process, would be a good way to go. Will get some YouTube vids watched and give it a crack.

 

[j3nks79]

Check your lower arms and bushes for play. Also check for movement in tierod and track rod ends.