Running 203mm rotor with QR forks?

Yahoobedoo

I've bought a Specialized Enduro FSR 2006 in bits and am in the process of building it up.

Stock brakes are Hayes Sole 8" rotor front and 7" rotor rear fitted to stock wheels.

As they need replacing I'm looking at Avid Juicy 7, Avid Juicy Carbon, Shimano XT or Shimano XTR.

I was going to go with 203mm front and 185 rear (roughly the same as the Soles) but my son reckons 203 front would be too much for the 2007 Rock Shox Revelations I've bought - his explanation being that the forks are QR, not bolt-through (more flex?), and the brakes I'm looking at are all more powerful than the stock Soles.

Is this right? Am I likely to be better off running 185mm all round or even 185mm front and 160mm rear?

I'm 15(ish) stone (roughly 210lbs) and intended use is All Mountain, long descents but no DH'ing.

Cheers.

artillerydave

I would agree with your son but not for the points he raised 203 is an overkill if you are going for any of the brakes you describe, a 180mm front 160mm rear wuold be a far better option and should prove more than an improvement over your old hayes soles. however Revelations are not flexy forks they are fantastic, and could handle 203mm if you chose to run them. I'd go for the new XT brakes, with Servowave levers, I've got a set and they are fantastic.

Splasher

I'm a few pounds heavier than you and I run 180/180.

You don't need as much braking force on the rear as your weight shifts forward as you brake meaning there is more grip available at the front and this is why people tend to fit smaller to the rear.

This is fine for short braking bursts where balancing brake force allows you to save a bit of weight off the rear rotor. However, on steep extended decents, the rear is the brake that tends to get dragged and a larger rotor keeps the heat down (bigger heat capacity and radiator). So if you were speccing up an XC bike at your weight, I'd say 180/160, but for AM, I'd go 180/180.

Sir HC

See what the manual says.

If your into long descents and all mountain, then go 7 inch front and 6 or 7 on the back.

nicklouse

the fork is fine for 203mm discs as can be found in the manual or on RS's webby.

if you want 203mm fit them. but you do not need them.

180(5)'s will be a good compromise for most riding.

clarkson

you're putting revelations on enduro? arent they 130mm travel? the enduro frames designed for 140-1500m travel.

my enduro has juicy 5's 203mm/185mm and are perfectly good enough for me, they give plenty of power. they are the standard rotor sizes anyway.

Cunobelin

There was some concern a few years ago that there was a possibility of severe braking pulling the wheel out i they were quick release. This was exacerbated by the forces from larger rotors.


The consensus was that if you have a recess for the QQR heads (lawyers lips) and the QR is done up properly there shouldn't be a problem.

Some discussion at BikeBiz...

http://www.bikebiz.co.uk/news/20476/Disc-brakes-and-MTB-forks-Independent-testers-verify-axle-slippage-and-QR-loosening-

Yahoobedoo

Many thanks for all the replies folks - it's always nice to get other people's opinions and has given me plenty food for thought.

artillerydave wrote:

... however Revelations are not flexy forks they are fantastic, and could handle 203mm if you chose to run them.....

Sorry, I've attributed his comments to the Revelations but he was speaking in general terms about a QR fork was more likely to flex than a 20mm bolt through.

Splasher wrote:

...but for AM, I'd go 180/180.

nicklouse wrote:

....180(5)'s will be a good compromise for most riding.

Sir HC wrote:

....If your into long descents and all mountain, then go 7 inch front and 6 or 7 on the back.

You're in good company, that's what my son reckons I should do!

clarkson wrote:

you're putting revelations on enduro? arent they 130mm travel? the enduro frames designed for 140-1500m travel.......

According to the manual it'll take up to 160mm but as stock it would have come with Marzocchi All Mountain SL 130mm travel forks - I couldn't find any similar at a decent price so went with the coil Revelations. I could have gone longer travel but as I'm stepping up from my Spesh FSR XC with 100mm travel J3's I thought 130mm would be plenty.

clarkson wrote:

....my enduro has juicy 5's 203mm/185mm and are perfectly good enough for me, they give plenty of power. they are the standard rotor sizes anyway.

That's the way I'm thinking as well.

Cunobelin wrote:

There was some concern a few years ago that there was a possibility of severe braking pulling the wheel out i they were quick release. This was exacerbated by the forces from larger rotors.

The consensus was that if you have a recess for the QQR heads (lawyers lips) and the QR is done up properly there shouldn't be a problem.

Some discussion at BikeBiz...

http://www.bikebiz.co.uk/news/20476/Disc-brakes-and-MTB-forks-Independent-testers-verify-axle-slippage-and-QR-loosening-

Thanks very much for the link, I'd tried Google but not had any luck.


Decisions, decisions - will need to decide tonight or tomorrow as looking to buy from Merlin who are having a VAT-free weekend.

Cheers.

clarkson

ah i see get your point about the fork. sorry. id go fort he stock configuration. i cant say ive noticed the weight difference on mine, especially as it weighs nearly 35lbs anyway!

Splasher

2006 All Mountain SL was a 150mm fork I think you'll find. It's a shame you've bought the Revelation as I have a 2006 All Mountain 1 (130-150) for sale (£150 in mint condition).

Yahoobedoo

Splasher wrote:

2006 All Mountain SL was a 150mm fork I think you'll find.

Frayed knot :

FORK Marzocchi All Mountain SL, coil spring, air assist, external rebound adjustment, 130mm travel, alloy steerer.

Splasher wrote:

It's a shame you've bought the Revelation as I have a 2006 All Mountain 1 (130-150) for sale (£150 in mint condition).

Might still be interested - any pictures?

Cunobelin

For more info on the failure "problem" google "James Annan"

Splasher

Might still be interested - any pictures?

Fitted:



off the bike:

Yahoobedoo

@ Splasher

PM sent.

Cheers.

Yahoobedoo

Thanks for all the help and advice.

Ended up going for a set of 185 Juicy Carbons front and rear.

Were going to be fitted to the Revelations but will now be going on the 130-150mm All Mountains 1s that will be arriving next week courtesy of Splasher. The Revelations will be going on the 2006 FSR XC.

In my ignorance of these things I've just realised that the Revelations are IS mount whilst the All Mountains appear to be Post mount - does this mean I'll require one of these?

http://www.chainreactioncycles.com/Mode ... elID=13717

Splasher

Yes

Yahoobedoo

Cheers.

dave_s

Decent choice, I use 180/185 front rotor and 160/165 rear rotor for All Mountain setup on my bikes and have never had probs.

Don't forget you used to be able to lockup your back wheel easy with V-brakes so with hydros it's even easier so 160/165 on the rear is generally ample unless you live in the Alps or weigh 20stone.

Your front brake is your main stopper and nowadays Avid brakes have loads of power so a 180/185 is plenty too.