The discs on my 2008 848 are a little pitted, I’m assuming they are the original discs but I’m not sure as the calipers have been upgraded to Brembo M4s. Any recommendations for a place that can skim them in the north west?
How much material is left on them, IOW are they above min thickness. If close to it and/or the pitting is deep set, you're better off buying a new set. If they are only lightly pitted you'll probably achieve decent enough results with some fine grade wet and dry emery cloth. I'm not sure skimming them is worth the time and expense TBH.
Never seen it done….. The discs are semi floating and at best have a wear tolerance of 1mm, I think stock 848 discs have 0.5mm. Unless you remove the bobbins, skim the discs and reassemble, you’ll never get them flat and true. Then you’ve got source suitable bobbins to rebuild.
You can hone the surface of a used disc, 'flexhone' make a bit specifically for the job, similar results can be achieved with a red Scottish brite Roloc disc, or a poly Clean & Strip disc on a grinder. You have to be realistic with your expectations though, if the surface is heavily scored or deeply pitted then it's time for new discs
Right, sounds like new discs then! I’ll get some photos tomorrow but the pitting looks more than 0.5mm, you can feel the pits with your finger nail. If the callipers have been upgraded to M4s will the discs be the same diameter as standard?
Calipers won't have any bearing on disc diameter. Stock discs are 320mm. It's possible to up them to 330mm with the addition of spacers on the caliper mounts. If you're not sure, pop a picture up of the caliper mountings. Brembo Serie Oro are a decent upgrade and not as expensive as the OEM discs.
I'd be inclined to compare that inner 5mm or so of disc surface, which looks as if it isn't being swept by the pads, with the same area on the other side, and the same again on the other disc. I don't know how this should look with these brakes, but it's not uncommon to see car discs, especially on the rear, which have a scabby stripe around them where a chunk of pad is missing, or whatever. It's easy enough to check the pads anyway. Otherwise my inclination would be to treat this as mainly a question of cosmetics, although I'd check the disc thickness in a few places with against whatever the minimum specification is.
I’m planning on a full strip down over the winter, I’ve got a new master cylinder and hoses to fit so I’ll take a look at the pads and check the piston movement ect then. I do like the bike to look it’s best but I won’t compromise on parts that look better than they perform if that makes sense.
About 3/4 way through this video there's a DIY approach to using the "flexhone" approach, using a pillar drill and home-made turntable to restrict the honing to the area of the disc that the pads grip. I guess an alternative way would be to find some way to attach a circular "mask" to restrict the area to which any grinding/sanding treatment is applied.
