Rotor sizes

stowei · June 2007

Apologies if this issue is in a basics guide somewhere, but I can't find it. Question is, what determines what size front brake rotor I can run?

Question applies to any fork and wheel I guess, but the fork in question is a Rockshox Judy with non-post mounts running a Shimano caliper with a 160mm rotor. Can I increase the rotor size, to say 165mm, or 180mm or 205mm (I think those are the standard sizes from what I can see?)

1) Is rotor size determined by the fork? (ie are the caliper mountings further up the stanchion if the fork is designed for a bigger rotor?)

2) Or does the caliper determine the rotor size? (ie stanchion mountings always in the same place and the caliper being designed to move the pistons further away from the mount)

3) Or are the mounts always in the same place on the fork and the caliper, with different spacer-brackets between fork and caliper used to move the caliper further away from the spindle for larger and larger rotors?

Have re-read that to try to make sure it makes sense but I'm stuill not sure! Hope so!

Thanks

Ian

ROCHA · June 2007

Read all of it fast! Nick will probably not have the patience...
http://www.mbuk.com/forum/topic.asp?TOPIC_ID=190919
[:D]

WD-40? GT-85?? I'd rather use the old AK-47!

nicklouse · June 2007

looking the sticky above.

disc size is determined by the fork maker, the use. and the caliper and or adaptor.

on the judy you could fit a 160,165,180,185,200,203,205,225,230mm discs.

but the makes will say 180/185mm max. useage will also sugest 160 to 185mm

nick
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stowei · June 2007

Thanks. Don't feel too bad about posting the question because I had read that sticky and although I am a good mechanic (on road and motor bikes at least) I still couldn't work it out.

If I take this link as an example:
http://www.wiggle.co.uk/ProductDetail.a ... 5360029617

It says that the caliper is compatible with various sizes of 6 bolt rotor but they only offer one size of caliper (at least if you place an order they don't seem to ask what size rotor you intend to run). If the difference is therefore in the mountings on the fork, is there a measurement that I can take to tell for a particular fork what size rotor is intended(ie how far the mountings are from the spindle/axle centre). (Sheldon Brown publishes this kind of data for lots of bike things but doesn't really seem to have moved into suspension and hydraulics much. The SRAM site is equally silent on what size rotor I should be running with my particular fork.)

If the answer is in buying brackets, where do I go for those?

PS Don't know why I said its a Judy by the way; its a Duke.

Thanks but still very confused, in spite of being able to strip anything from a Norton Commando to a Honda CBR 600 via any number of roadbikes.

Ian

nicklouse · June 2007

linky dont work. i guess the calipers are post mount? so you just get an IS to Post adaptor for whatever disc you want.

shimano LX?

duke 180/185mm which depends on the brake maker. if you have a look at the links at the bottom of the sticky there are drawings. might help.

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stowei · June 2007

Thanks. Not sure how I managed to paste the link wrong. Here it is again:
http://www.wiggle.co.uk/ProductDetail.a ... 5360029617

It doesn't say whther IS or post; it refers to 'shim-less' which I had assumed meant IS because my current Shimano caliper is IS si I assumed that was the Shimano standard, but upon reflection perhaps it does mean post-mount?

Ian

nicklouse · June 2007

nope they are postmount. Did you look at the drawings? if you did you should not be really asking this question.

if you read the sticky you should know there is IS and Post, the makers dont have a standard. Post is also known as the Hayes mount but hayes do make calipers that are IS mount only.

this from the add is a bit of a give away <blockquote id="quote">quote:<hr height="1" noshade id="quote">Front and rear bled kit comes without adapters or rotors giving you the freedom to customise to suite your bike<hr height="1" noshade id="quote"></blockquote id="quote">

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stowei · June 2007

Thanks Nick.

However, I'm not thick and its obvious from what I've written that I've twigged the essential distinction between IS and post. Yes, on reflection I could have zoomed in on the photo and noticed the alignment of the holes, but that would be a pretty unreliable test for someone only getting to grips with the technology.

If you reckon that 'shimless' or the quote that you have posted will tell someone like me whether its post or IS then you take much more powerful drugs that I do - respect!

I do read the manuals and the stickies but if I can't understand them I'll ask. Thought that was the point of these sites.

Look forward to helping you out with your first Commando clutch-strip.

Get out more mate!

Ian

nicklouse · June 2007

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by stowei

Thanks Nick.

However, I'm not thick and its obvious from what I've written that I've twigged the essential distinction between IS and post. Yes, on reflection I could have zoomed in on the photo and noticed the alignment of the holes, but that would be a pretty unreliable test for someone only getting to grips with the technology.

If you reckon that 'shimless' or the quote that you have posted will tell someone like me whether its post or IS then you take much more powerful drugs that I do - respect!

I do read the manuals and the stickies but if I can't understand them I'll ask. Thought that was the point of these sites.

Look forward to helping you out with your first Commando clutch-strip.

Get out more mate!

Ian
<hr height="1" noshade id="quote"></blockquote id="quote">

a clutch strip sure no probs. engine build which? race car suspension set up sure when.

Oh do you need a car designing?

for a person that i took as having some sence and aptitude i an really supprised.

if there is a picture of something i tend to get as much info from it as posible and then compare it to other infos. be that parts or drawings etc.

what supprses me is that you as someone with some mechanical aptitude did not/could not see from the picture and the info in the sticky what was going on.

if you would like to rewrite the sticky so all can understand it please do. Maybe i have just been playing with bikes and cars too long.

nick
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Stinkyboy · June 2007

just a quick add, some forks wont warrenty disks over a certain size, eg 888's over 205
(i wouldnt argue with nick he knows everything mechanical....ask him to make a sponge cake however! :-p

HUDDERSFIELD DH SCENE

nicklouse · June 2007

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Stinkyboy

just a quick add, some forks wont warrenty disks over a certain size, eg 888's over 205
(i wouldnt argue with nick he knows everything mechanical....ask him to make a sponge cake however! :-p

HUDDERSFIELD DH SCENE

<hr height="1" noshade id="quote"></blockquote id="quote">

i have been know to make the Odd soufl‚.

But cake takes too long.

nick
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Stinkyboy · June 2007

hahahaha, nick when you out in france i'm going in less than 10 days, did you say you were popping over?

HUDDERSFIELD DH SCENE

nicklouse · June 2007

nope not doing france this year.

but Jon and E'beth will be setting of in a weel for 2. so look out for Jon on the white Dragster and E'beth on the Kawa green and White Dragster.

i will be in re for the first few weeks of August.

nick
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Stinkyboy · June 2007

ok then, will pop over and say hi, i'll be on a ODC eight 2five, tom'll be on his apple, ritch on his vandal and rob on his dragster beardy on his demo8 and platty on his stinkydelux, so theyre bound to spot one of us! where is
A(funkydoodahontop)re

HUDDERSFIELD DH SCENE

Rotor sizes

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