Pairing disc rotor sizes
- Thread starter ishaw
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I was considering 180 at both ends. Not for any particular reason other than I have a pair if rotors. Not checked rear clearance yet, may just get a 160 for the rear, just wondering if there will be any issues. Assume a larger rotor could stress the frame more?
Theoretically more risk of glazing pads as you'll never get them hot enough, though 180/180 are unlikely to be more of an issue than 180/160 anyway. Unless you are a hardcore brake dragger.
I've done 180/160, 160/160 and 160/140 and none of them make a huge difference until you're really going for it. Costs you virtually nothing in weight either.
I've done 180/160, 160/160 and 160/140 and none of them make a huge difference until you're really going for it. Costs you virtually nothing in weight either.
Interesting you mention glazing. Ive had an issue with a set of brakes which I think this keeps happening too. 180/160 rotors, tried everything from new pads, sanding pads, sanding rotors, cleaning everything with brake cleaner and they always seem to glaze and squeal. Never had this with any other brake.
It is why I'm asking this question actually, as thinking about simply swapping them out for some hopes and have some 180 rotors on the way.
It is why I'm asking this question actually, as thinking about simply swapping them out for some hopes and have some 180 rotors on the way.
captaincowelly
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Only have one bike with discs so I'm certainly no expert in this area but from experience of other applications (road vehicles/motorbikes) glazing occurs when the pads are overheated,not from under-use.Don't know the exact science but I'm assuming the higher temperatures 'draw out' something from the compound (possibly resin?) which leaves a hard,glass like coating on the surface.
My theory on size is this (assuming we're talking XC not DH) F+R 180's have awesome stopping power on an XC bike but if they're 'too much' and only get used gently,more chance of calipers sticking over time.Sometimes better to go less powerful but use them more.
180 Front/160 Rear I can imagine being a great combo but I can't help but lean towards having them both the same.
But that's just me.
Yes, sorry, sloppy use of language and a lazy post!
You're right though, glazing or polishing is usually from maintaining them at the same, high, temp for ages, under pressure, without either stopping or releasing the brake.
Dragging on overly large discs *seems* to be a fairly common cause of this. Possibly as those who get overly large discs tend to do it because they aren't particularly good descenders!
Using the brakes hard (and getting them hot) then stopping doesn't have the same issue as getting them hot, then baking them under pressure for ages!
captaincowelly
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The dragging would make sense,could see that happening.Every day's a school day!
Does size matter? 
I don’t think it matters all that much, 160/160 was pretty standard on my Xc bikes, should be enough braking for most situations. Actual brakes and pads make more of a difference,
I use 180/160 now on my full-sus bike, makes sense to have the larger disc at the front and not the other way around!
if you have 180 rotors just use those, assuming you have the adapters needed.
I don’t think it matters all that much, 160/160 was pretty standard on my Xc bikes, should be enough braking for most situations. Actual brakes and pads make more of a difference,
I use 180/160 now on my full-sus bike, makes sense to have the larger disc at the front and not the other way around!
if you have 180 rotors just use those, assuming you have the adapters needed.
