It seems that I have to replace my front brake-disks now. The problem is that there is quite a hard ridge of corrosion that is slowly growing in from the outer edge towards the centre. The back disks are not so bad and should see a few thousand miles yet. I guess I can't complain too much with a 7-year old car and 72,000 miles on the clock! My question is - what are the best disks to get as replacements or - perhaps better - what are the pro's and con's of the different types of disks that are available. (7/00)
I got a pair of grooved front discs from Moss in Bradford for about 90 quid. I needed discs quickly (hours!) so didn't shop around, but this seemed like a good price. (7/00)
Oh! The thing I forgot to ask is, " Is there any difference between the front/back disks for a Mk1 and Mk 2"? (7/00)

Yep - the front and back disks are different on both Mk 1's and Mk 2's :-)

1.6 and 1.8 Mk 1 disks are different (the 1.8 has bigger disks). Not sure what happened after 95 - does the later 1.6 have the bigger brakes? And Mk 2's - same brakes on 1.6 and 1.8? I think they are the same as Mk1 brakes? There is a brake conversion detailed on miata.net (garage - suspension) to fit 1.8 disks to a 1.6., but otherwise you need Mk 1 1.6 disks. (7/00)

I have started to notice a slight grating sound from my n/s front wheel which I presumed to be the brake pads wearing down, however on checking on saturday I found it is the actual disc that is "wobbling" and hitting the bottom of the brake mounting where the calliper is bolted in. Does anyone know whether this is adjustable and part of the alignment or is it a bit more serious than that! (5/01)
Sounds like a warped disk to me. If so you will need to get the pair replaced... (5/01)

How did you test for wobble?

The disc is fixed by being sandwiched between the the wheel and hub flange and is held tight by the wheel nuts themselves. If you simply took the wheel off and spun the disc it would be loose (unless rusted on) and wobble.

I suggest you take the wheel off and then replace the nuts and tighten them to clamp the disc.(if the threads don't go right to the bottom you will have to put some washers or something similar on to make up the difference) If when you spin the disc now it still wobbles you do have problems. It may not be a warped disc though. If the mating faces between the disc and the hub flange are rusty this will prevent the disc seating squarely - the remedy is to take the full caliper bracket off, remove the disc and clean the mating surfaces with coarse emery paper.

May sound obvious but have you checked the wheel bearing - you would normally hear a duff one of these but it's just possible it's silent but loose - also you haven't said if the grating sound is there all the time or only when you press the brake. If it's continuous then it very possible it's the bearings. Just an alert - make certain you support the car really well before trying to loosen any of the bolts - the ones holding the caliper bracket and especially the hub are very tight. If it is the bearings you will get them at a very good pice from your local Bearing Services depot but you do need to know what you are doing to knock the old ones out and press in new ones. (5/01)
It might be warped, or it might be that rust has developed between the disc and hub. Try taking the disc off (just remove the caliper mounting bracket). Clean and derust the faces between disc and hub very carefully, and put a /very/ light smear of grease (lithium grease, not copper grease) there. Do both sides. (5/01)
After the disintegration of my pads at Oulton Park, I'm thinking of converting my brakes to 1.8's. I know several of you have done this - have you done front and rear, or has anyone done front only? If I do front only, will it significantly alter my brake balance? (5/01)
I wouldn't have thought it would affect the balance significantly. Running EBC Greenstuff front / OE rear should theoretically upset the balance due to the higher friction coefficient of the EBC pads, but it's not apparent in practice ........ unless you make a habit of braking hard half way round corners, but you wouldn't do that, would you? ;-) (5/01)
Also, I thought your brake bias is quite high to towards the front discs, withthe rears mostly being used for the handbrake, not sure what the bias is though. This being the case wouldnt have thought it would harm it to have 1.8 discs on the front and 1.6s on the rear. Have you checked out the 1.6>1.8 disc swap on miata.net, very good. (5/01)
I've done front only. As all the photo's of my car into the first bend at Curborough show, they certainly work!! Brake balance doesn't feel adversely affected under normal road braking though. (5/01)
I've done the 1.8 conversion from Miata Net (actually I got someone to do it for me) Definitely makes difference - primarily in maximum applications( on track and emergency "hat in a Volvo" situations) and fade/overheating on track (i.e.. none) I also did front and back for "balance" reasons altho' Mr. Millman said it would be of negligible effect in the "real world" As my discs are drilled I thought it would look better too (OK I know!) So - it will make difference , especially on track Yes, front only should be OK If you go the "Miq Millman route" i.e.. add 1.8 discs and caliper BRACKETS rather than whole 1.8 caliper unit you'll need to bend the dust shields back from new discs - come to think of it you'll need to do that with a full replacement anyway. Sounds "shoddy" but if done carefully looks fine. As ever I also recommend S/S brake lines for the "improved modulation" effect. (5/01)
Just to throw in an alternative, I uprated my discs to the Moss slotted discs all round, Greenstuff pads at the front, changed to Dot 5 fluid and s/s goodrich lines, and after 2 donnys have never had any brake fade, which if you ask anyone whose ever followed me is quite an achievement. (5/01)
Did think of that, but reckon that if I'm buying new discs I might as well get bigger 1.8 size ones. I too have never had brake fade, but I regard Oulton Park as way harder than Donny on brakes. (Oulton Park has a lot of longish straights followed by slowish corners, rather than a long series of sweeping bends as Donny is mostly. - OK I generalise) Also Donny gives time for brakes to cool during the sweep through Craner and on the main straight - Oulton never gives them that chance - the straights aren't /that/ long and two of the serious braking areas are downhill (Knickerbrook chicane and into Cascades). It's the chicanes ( 2 between Shell hairpin and Knickerbrook) what done it. I didn't get fade, but the pads disintegrated (Mintex) which is a symptom of excess heat. (5/01)
Yet another setup: 91 Miata Stock disks, stock pads, SS brake lines, ATE Superblue brake fluid. No brake problems at Goodwood Spa Nurburgring (Nordschleife and GP track) Salzburgring and during frequent alpine trips. (5/01)
The Mk 2 brake parts are identical to 1.8 Mk 1s. You can fit mk 2 brackets (1.6 and 1.8 are the same on Mk 2s) - again, all you need are brackets, discs and pads. I'd assume you buy new discs and pads - actually I got a virtually new set of Mazda (Sumitomo) pads with my front calipers/brackets (couldn't buy the brackets alone) so I used them. You may have to do without shims unless you buy Mazda pads, and at the rear you need different guide plates (the stainless steel clips which hold the pads into the brackets) (the front ones are the same as 1.6). These guide plates are hard to find but essential - they only come with Mazda pads. A friendly Mazda garage (?) or independent service chap may be able to provide a used set. Re getting brackets made - I suspect the tooling costs would be horrendous. It's a complex casting, and needs machining. To be even slightly economical, the batch size would need to be huge - and there just isn't that much demand. Mazda will sell you the brackets, but they're about 70 ish each. Meanwhile, there's a steady supply in scrapyards! The calipers you'll get as well have their value! (4/03)
Curiously, I just priced a set of Brembo discs at lunch time... £40 IRP a corner.... is this good?? I have ABS on my Roadster, is there any difference between the discs on non-abs and abs cars??? (5/01)
They're the same. The ABS toothed wheels are part of the hubs (which are different, although ABS hubs will fit none-ABS cars OK) (5/01)