Why do brake mount bolts have all those washers?

My rear post to post has just one thin washer per bolt but the front has those curved spacer type ones with cups to seat into etc. Can I just lose all the gubbins and run shorter bolts?

The bolts are not perpendicular to the caliper surface because of the adaptor, they won’t fit properly without the washers.

The little cuppy things help take up any small alignment issues.

You trying to shave some weight? 😉

Just want to go Ti and assumed you could just use the bolt and a single washer.

You very often can. I don’t think I have the cup things on my bikes, but I’ve had them previously and that’s what they’re for.

Try it. Probably be just fine.

I think they’re needed on post-post adapters where one long bolt goes through the calliper, adapter and into the frame. If the two faces of the adapter aren’t parallel. Not necessarily a tolerance or accuracy issue, just that the calliper needs to be rotated forwards a bit as it’s spaced out. Possibly more of an issue with 4 pot brakes which need lining up with the disk surface so the brake track runs along the pad properly.

Where a 2 pot is probably fine as long as the disk doesn’t foul the caliper.

I wasn’t aware of them either until I saw some recently. It’s not like the avid system which is to compensate for less than perfect frame alignment.

Normally fine to bin them off but can help aligning the caliper sometimes – if the surfaces aren’t quite square the caliper can move when you tighten the bolt down which is a right ballache.

Was working on the brakes last night and had a shimano centre lock caliper (which I’ve not used before) foul two different calipers in their normal configuration – needed to space them back up the rotor using these disks, which doesn’t seem ideal. The rotor is a disk mounted onto quite a prominent spider which was catching the caliper.

With post-mount often needed to space the caliper enough such that it doesn’t foul the disc. It might work, it might not.

You can get titanium bolts which work with the curved washers, you can also get the washers themselves in titanium.

The washer are aluminium mind so not much point in replacing with ti. The bolts are just plain M6 bolts

I remove them personally, I’ve never found any issues. Obviously doesn’t work as easily with Avid tri-align.

I’m feeling old here, as I remember, updating my cantilevers v brakes. Also initially being a little confused with our newer bikes not having, nor apparently needing spacer and or alignment washers.
However the collection includes 1980s through to 2019 bikes so the whole range of brakes, so need spacing some need help aligning. On some older bikes we have corrected alignment through filing and changed the mount size to get rid of the extra washers. On the odd one we have needed extra thick spacers / extra washers to clear the disc. And some really need shaped washers help to align.

Old avids needed them and unthreaded bolt through adapters need them, so it depends on your adapters, I personally only use NSB adapters because they’re cnc machined, Hope are also CNC’d but only available in black or silver, I’ll never use cast/forged adapters they are garbage, some aren’t even flat where the caliper rests.

They’re different mounting systems, the cps washers, which take up the alignments issues are designer into the calliper, so can’t be used with out & vice versa,
If you have the cps cup washers then you can by all means use a Ti bolt, but pretty sure the washers need to stay.

http://www.bike-discount.de/media/org/orgb_A/orgid_3/thumbs/52329_298569.jpg

As far as I have come across panzar is correct, if you have the conical washers you have to keep them as the adapter they go with make up the correct spacing for the given rotor size. Good link by the way panzar I’ve bookmaked that for when I refit the couple sets of avids in the spares box.

Thanks

Tim

timoth27

Subscriber

As far as I have come across panzar is correct, if you have the conical washers you have to keep them as the adapter they go with make up the correct spacing for the given rotor size.

That’s the case when they go under the caliper, like with avid tri-align (a bloody awful idea, introducing an extra direction of alignment adjustment in which to set it up squint, instead of the normal totally nonadjustable, always square fitment) but sometimes you get them only above the caliper, for postmount adaptors. You can get away without them on the latter but as you say with teh former, they’re part of the stack height

I was taught, early on in mtbing, by my LBS owner, that ti bolts weren’t a great idea. Don’t go as tight as steel as ti is softer, or something… slightly more stretch in it. This was back in the 90s, so it might’ve been anther reason that I’ve forgotten!
Still, not something I’d want in my brake calipers.
I’m probably the only person in the world who doesn’t use them, but I’ve never had a brake caliper come loose, so I’m happy.

When I bought a 160PM – 180PM Shimano adapter is came supplied with the bolts (1 long and 1 short[er]) and washers. I’ve never been entirely sure why they’re there but they clearly have to go on top of the calliper, under the head of the bolts; without them in place I’d guess that the bolts would be too long.

When I bought a 160mm PM – 180mm IS adapter no bolts were supplied and I’ve just used standard M6 bolt without a washer stack.

I’d agree with DezB on the ti. bolts things. Titanium is stronger than steel by weight but in a fixed dimension situation (such as bolts) titanium bolts with be lighter & weaker than steel.