- My model of MX-5 is: __na 1.6 auto
- I’m based near: ulster
- I’m looking for technical help or recommendations on: __above brake judder issue
New discs (and pads) usually stop brake Judder. Make sure all contact surfaces are free from rust and dirt to ensure that the disc is perfectly flat on the hub. If you have a DTI you can measure before and after runout to confirm the repair. Measure the runout before buying the discs if you want to confirm before spending any money. Should be less than 0.1mm
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It may be a seized caliper. Check the wheels are not getting hotter than normal.
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bought mid july, tidy 100k well serviced looked after auto mk1, drove it 500 miles home, has full years test, drove very well just a brake issue light judder on application got slighty worse when brakes heated after a bendy early morning 2am 90 miles on the A75… on examination discs front and rear like new , pads slight wear but nothing that should have contributed to pulsing pedal. no abs here, no visible movement in any suspension or stub axle or wheel bearings… i had an issue with this on a Mercedes, however it had 4 pots and one of the pots had a sticky piston, freed up and left good the issue was gone, so i though perhaps a pair of new bare calipers would be advisable, the thing is the supplier of the left one is challenging the fit of his for mine when he asked for my reg, now i have 2 mk1’s and told him both cars same year same caliper, personally i think its the extra paperwork he has to do for posting the caliper to me in Ulster, afaik and my extensive research tell me while there may be many suppliers of replacements the std caliper for mk1 and mk2 are same and just differ when the 270mm disc brakes use a bigger caliper… am i totally wrong, thinking that a sticky piston would show this sort of behaviour…my tek guy says that on very detailed inspection of both existing calipers the slides and all moving parts are free…
Did you or your tech check the back face of the discs? I had judder on a previous car, it showed up particularly when braking hard than just gentle braking. All discs pads looked fine, infact I had new pads fitted to the front. Turned out the rear faces of both front discs were rusted, literally flaking rust (you can’t see them properly unless the wheel is off) new discs of course sorted it and more new pads🤔
I didn’t but would bet he did check, he’s an ex racer and a hard one… he leaves nought to chance. said they looked like new…he hates autos and didnt drive this machine although i took him a run just after i left her with him for his total chassis up looksee… he did the cam belt and front ancillary belts removed air con, all new hoses, antiroll bars and their bushes and full sus change…2nd previous owner back had prepared very well it for a daughter who got married , had a kid and never set a foot in it so its been in storage apart from a couple of weeks each year over the past couple… the chap i bought it from lost his storage and had only covered a few hundred miles in it in the past 2 years… it had its valves decarbonised on my run home…will
Check discs for warping as Robbie described with a DTI. Do you feel it through the steering? If so that would indicate it’s front discs (potentially rear too). It is possible a caliper issue could cause it, but most likely disc warp.
This is pretty useful to try and narrow down your issues. Juddering Brakes - Motorworx Market
I agree with Robbie, especially if the discs are fairly new. It takes about 3,000 miles for disc thickness variation to cause juddering. Unless the hub and disc mating surfaces are spotlessly clean when fitting the new disc, you get a bit of runout. This doesn’t show up at first, because it’s a floating caliper and can move with the disc during braking. However, the pads are kissing the disc in the same two spots when the brakes are off, with every rotation, and this wears the discs thinner there by a few hundredths of a mm. After a few thousand miles, the thinner spots cause judder when braking, and you have to replace the whole lot again. Using a different mechanic!
If you don’t have a dial gauge, clean the hub with a rotary wire brush before installing the new disc. When it’s all back together, pump the pedal to set the pads, spin the wheel and you should hear an even whooshing sound all the way around the rotation. Any variation means the disc is not running true. It is not hard to get it right - I’ve done several disc/pad changes on various cars - but pro mechanics can be appallingly lazy.
Thanks guys , it was a cracked disc, showed up more after a warm run. almost unnoticeable when cold… appreciate your inputs…will
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