Brake discs

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Parrot of Doom

Original Poster:

23,075 posts

236 months

Friday 21st January 2011
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Any reason why I can't use an Avid disc with an XT caliper?

frontbum

5,414 posts

161 months

Friday 21st January 2011
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It'll be fine presuming it is the correct size for the calliper/adapter you have.

Shimano adapters generally fit 160/180/200 mm rotors, some brands of rotors are made in different sizes (e.g. Hope and possibly Avid use 183 and 210mm IIRC).

You can try and bodge it in anyway, but you might find the rotor rubs on the calliper.

Edited by frontbum on Friday 21st January 12:22

P-Jay

10,625 posts

193 months

Friday 21st January 2011
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Yeah shouldn't be a problem, even the old metric / imperial thing 203mm instead of 200mm etc is usually no more than a little space on the caliper away from perfection. The outside edge of the discs are usually so non uniform - wavy etc that 3mm won’t make any difference.

Not always the case though, I've just come unstuck. Ordered a set of Hope V2 DH brakes, instead of the floating Hope discs ordered a set of Aztec fancy Dan ones instead as I'd used them before with Juicy 7's and Codes on my DH bike and they work really nicely. Sadly for me, Hope rely on a 'taller' pad rather than a 'longer' one like most companies do for extra surface on DH brakes so the disc only really hits the bottom half of the pads - bugger, less power than a cable disc.

Camoradi

4,298 posts

258 months

Friday 21st January 2011
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I have the caliper / disc combination you are suggesting on my Giant. No problems to report.

Parrot of Doom

Original Poster:

23,075 posts

236 months

Friday 21st January 2011
quotequote all
Cool. The XT disc is smaller than the Avid disc but I have the Avid spacer for the caliper, should be the same size non?

Uriel

3,244 posts

253 months

Friday 21st January 2011
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While we're on the topic, maybe someone can help me before my head explodes. I have a bike with rigid forks with an IS mount and I'm running a Hope M4 caliper with a 203mm disc. All is well. Except I got a good deal on a bouncy fork and thought I'd see what all the fuss is about, but it turns out that the fork (RS Tora) has post mounts for the caliper.

It seems that I'm in a tiny minority that have this problem whereas if I had it the other way round, I'd have adaptors up the ying yang to solve my issues.

The only thing I can find that seem to offer hope (pardon the pun) is this.

But I'm confused by the +20mm part. If the caliper mounts to a standard IS fork and takes a 203mm disc, would this adaptor move it out further so that it would want a 223mm disc? If so, why do they not make a regular adaptor that doesn't change the disc sizing?

I did come across this which seems to be what I need, but I'm in denial because of the fact it's almost 5 times more expensive than every other adaptor they have!

ndg

560 posts

239 months

Friday 21st January 2011
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Hope used different caliper halves to change to disc rotor size (my mini's are a no.3, so 163 on the rear 183 on the front).

To get your brakes to work you would need a post to IS 160mm bracket I think (like this). I'm only about 50% sure though!

N.

ScarlettRado

14 posts

202 months

Saturday 22nd January 2011
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Uriel said:
While we're on the topic, maybe someone can help me before my head explodes. I have a bike with rigid forks with an IS mount and I'm running a Hope M4 caliper with a 203mm disc. All is well. Except I got a good deal on a bouncy fork and thought I'd see what all the fuss is about, but it turns out that the fork (RS Tora) has post mounts for the caliper.

It seems that I'm in a tiny minority that have this problem whereas if I had it the other way round, I'd have adaptors up the ying yang to solve my issues.

The only thing I can find that seem to offer hope (pardon the pun) is this.

But I'm confused by the +20mm part. If the caliper mounts to a standard IS fork and takes a 203mm disc, would this adaptor move it out further so that it would want a 223mm disc? If so, why do they not make a regular adaptor that doesn't change the disc sizing?

I did come across this which seems to be what I need, but I'm in denial because of the fact it's almost 5 times more expensive than every other adaptor they have!
http://superstar.tibolts.co.uk/product_info.php?cPath=57&products_id=359 - Type 8, PM-PM F203

Job done.

Uriel

3,244 posts

253 months

Saturday 22nd January 2011
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If I'm reading that correctly, Type 8, PM-PM F203 is for post mount caliper to post mount fork, no? I have an IS caliper and a PM fork.

ScarlettRado

14 posts

202 months

Saturday 22nd January 2011
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As far as I'm aware, all calipers are 74mm post mount, including Hope M4s...

Uriel

3,244 posts

253 months

Sunday 23rd January 2011
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ndg

560 posts

239 months

Sunday 23rd January 2011
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The hope HBSM20H bracket would require a 20mm bigger disc than you have here. They don't make one that retains the disc size, I've been told in the past that it's not possible due to the geometry.

Happy to be proved wrong though.

N.


gradeAfailure

651 posts

203 months

Monday 24th January 2011
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Uriel said:
(Previously posted under OH's username, Scarlett) Well I never - never seen a Hope caliper like that before!

Don't think I've seen an IS-PM adaptor anywhere other than the one you posted earlier then, sorry!

Edited by gradeAfailure on Monday 24th January 09:25

Pablo16v

2,112 posts

199 months

Monday 24th January 2011
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I had exactly the same issue as this a few years ago when I changed from IS forks to PM forks (also with older Hope Enduro 4 pot brakes). I had to buy the +20 adaptor and I contacted Hope to get them to make a 225mm disc to replace the 205 one. It might work out cheaper to buy a complete PM front brake off Ebay otherwise get the adaptor and see if the later "saw" type disc is compatible as you can get a 223mm one from here http://www.ukbikestore.co.uk/product/69/hope_saw_d...

ndg

560 posts

239 months

Monday 31st January 2011
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Spotted this on another forum:
https://clee-cycles.co.uk/cc/catalog/product_info....

may be of use.

Uriel

3,244 posts

253 months

Tuesday 1st February 2011
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Thank you! That looks perfect.

I ordered the one from Disco Brakes, but despite it being listed as IS-PM, 203mm rotor, when you put it all together, you'd need a 225+ rotor to fit into the caliper.