Interchangeability of discs

[Berlinbybike]

I have a newly acquired MTB and I need new discs. The brakes are Formula (no marking, so not sure what model) and I have noticed that there are various notes of suitability against various discs listed on various websites. Other than different fitting methods and diameters, what other issues should I address? I note that 6-bolt discs by Shimano in the correct diameters are available at reasonable prices. Are there likely to be incompatibility issues, or material mismatches, with these in some (likely as not) ten year old Formula brakes?

I'd appreciate any and all advice.

Thankyou all, Bbb.

 

[GrumpyGregry]

not every brand rotor is a good match for every brand of pad as not every rotor has the same swept area.

in an ideal world you compare old disc with new disc just to be sure. provided the disc is the same diameter, same fixing, a compatible thickness and the swept area is deeper than your originals you should be ok.

I once fitted a cheap 'pattern' disc in place of an avid original. the swept area was slightly narrower meaning the 'spokes' of the disc hit the brake pads, this manifested itself as vibration and noise when braking. Cured when I put a new Avid disc on. back-to-back comparison show the only difference was the narrower swept area and more 'spokes'

 

[jethro10]

Generally speaking, they should all be much of a muchness, but Greg is right, some do catch now and then, or seem a little "off" now and then, and some brake on only part (albeit large part) of the surface.

but if your brakes art 10 yr old, you probably don't have much choice other than to go generic - it's' likely to work ok.

I also had one catching once, when fitting, right on the top edge of the wavy bits, the Wife spun the wheel while I ground 1mm of the top of the points, a little touch up of the rough edges with a file and it was ok.

Jeff