Thoughts on rear rotor size - 6, 7, or 8 inch?

[kootenaytallboy]

Right now I'm running an Avid 203 mm rotor in the rear. Physics tells me that there really isn't much need for such a big rotor in the rear, as the majority of braking force comes from the front. For instance, my street motorbike has two rotors in the front that are nearly double the size of its rear rotor, and nearly all other types of machines have bigger front rotors as well. So, what's the deal with same size rotors front and rear? Anyone running 6 inch rotors in the rear? 7 inch? I know some world cup racers are using smaller rotors, but they're very likely using less brake than me, at least on average.

As for beta on me, I'm around 205 lbs, and ride pretty fast on an 05 Stab Supreme (41 lbs) here in Vancouver and in Whistler.

[norbar]

I prefer to use lighter brakes and bigger rotor just in case. Sometimes you just find yourself on a gnarly trail and the extra inch is needed. Would never go 6'' but I'm thinking about 7''.

[rico]

Depends on your riding style.

If you drag brakes a lot, then a smaller brake will heat up quicker and lose power.

If you're hard on your brakes for a shorter time, then smaller brakes will work fine and save a bit of weight.

[bullcrew]

i run 7 rear! love it.

[Sandwich]

I run 7 in the rear and am considering going to 8 this year. I've never had a problem, really, but I do have small wheels, and am switching to 26.

[poonstar]

i run a 8" rotor up front and a 6" rotor in the rear with avid ultimate levers and code calipers on my sunday factory...and they're great! i may even go downt to a 7" front rotor.

[manhattanprjkt83]

i run 8 on my bottlerocket...for internet riding 6" makes sense but when you are running a gnarly wet shoot at whistler you are thanking the man above you have that big pie plate on the back...

my $.02

[Damo]

Hmmm... I just recieved my Formula Ones, but with the 180mm rotors. To get the 200mm setup, I'm having to fork out another 90 euro.
Still going to do it though. Gotta have the bigger discs around these parts...

[ridiculous]

Im running a 7" rear with my formulas, its plenty.

[mandown]

for racing, i'd say the smaller rotor in the rear might be fine if you are looking to save weight. however, for long runs, like at whistler (as mentioned aboved) the extra rotor is nice after a long day of bombing and the shakes are starting to set in. it also lets you use a lighter touch to get the same amount of power to the rear, which will keep arm pump off for a bit longer. of course this is all theory. i ran a 7" on the back of my bottlerocket and now i run an 8" on the back of my UFO. i don't notice much of a difference.

[bullcrew]

for racing, i'd say the smaller rotor in the rear might be fine if you are looking to save weight. however, for long runs, like at whistler (as mentioned aboved) the extra rotor is nice after a long day of bombing and the shakes are starting to set in. it also lets you use a lighter touch to get the same amount of power to the rear, which will keep arm pump off for a bit longer. of course this is all theory. i ran a 7" on the back of my bottlerocket and now i run an 8" on the back of my UFO. i don't notice much of a difference.

Mandown likes 12" in the rear, no heat build up but tons of @$$ romping oops I mean stopping power! :D:monkeydance:

[- seb]

Im running a 7" rear with my formulas, its plenty.

I have an 8" rear on my Formula One, and it's way overkill. Waiting for a 7" to turn up at the moment. Don't think I'd ever go to 6", I imagine heat on long alpine descents would become an issue.

[cjcrashesalot]

I run 8" front and rear just for the interchangeablity. You don't need to have multiple different size backups this way, so you have fewer spare parts to carry around. Plus the weight loss is minimal... and other than that what is the real benefit?

[- seb]

Ah I don't have that excuse since I've got 2 sets of wheels so 4 rotors anyway. You're right, weight loss is fairly minimal (about 40g for Oro rotors) but it's all of those minimal savings that end up with a light bike, yada yada, etc, you've-heard-it-all-before.

Only other minor benefits are that a smaller rotor will be harder to bend (but conversely may warp more due to not dissipating heat fast enough!) and you won't hit it on as many things (but smacking your rotor on something is pretty unusual anyway).

[tlproject7]

with codes. 7 is fine front and back in my opinion. rode whistler like that, and a heli drop right near whistler which was steep braking for an hour.

[manhattanprjkt83]

I run 8" front and rear just for the interchangeablity. You don't need to have multiple different size backups this way, so you have fewer spare parts to carry around. Plus the weight loss is minimal... and other than that what is the real benefit?

another great point

[Lollapalooza]

I'm running Codes with a 7" front and 6" rear rotor. It seems fine. I'm only 135 with riding gear though...

[Zark]

10-20 minute runs.....yeah, I better stick with the 8" rotor

[Horror Business]

I run 8" front and rear. People who claim they use a smaller rotor for the weight savings are jokers.

[Sandwich]

i use one because that's what mine came with...i might buy a new rotor this year so i can do 8/8....but it depends on how much riding I do.

[dh415]

i have formula brakes with an 8 inch rotor in front and a six in the rear its plenty of power.

[DirtyMike]

Curently I have 8's front and rear, I would rather have a seven in the rear for a bit of a differnet reason..... The 8 feels overkill on the power, and I dont like locking up the rearwheel when I dont intend to. Parts Compatability is something to be concered with, seeing how thats why I do not have a seven in the rear currently, Rotor/Pad contact issue in which Hayes gave me the eight in rotor and adapter untill they can correct the issue with the stroker v7's.

You are absolutly correct in your thinking about power/modulation being mostly in the front of the bike, and I like having the rear brake being just a touch less powerfull than the front. I think it balances out the feel of the bike better. But thats just me.

[Damo]

Hmmm. I'm thinking I may just order the 8 inch kit for the front and leave the rear as a 7 for now then... I can always upgrade later...

[buckoW]

Hmmm. I'm thinking I may just order the 8 inch kit for the front and leave the rear as a 7 for now then... I can always upgrade later...

Hey Damo

You should be fine with the Ones and 7 in rotors. An 8 in front might be better but there is plenty of power in the Ones for around here. I am running the 8 & 7 and it works fine.
Give a call if you want to come over and ride some trains before the season starts.
Ben

[Damo]

Hey Damo

Give a call if you want to come over and ride some trains before the season starts.
Ben

Sweet. Will do.

I've always loved riding trains...
http://www.pedalcarsandretro.com/store/files/images/large/d_715.jpg

[buckoW]

haha, me too. Where is your conductors hat?

[zahgurim]

8 and 8 on all my disc wheels. Race, play, whatever...
Being able to swap wheels and parts around is nice, without having to fook around with the adapters.

[Rick205]

With 1.5-3min runs being my local, i run a 6" rear, when i go back to the alps the 8" will be coming back out...all depends on where you ride i suppose (and how).

[buckoW]

I normally run the 8 inch discs and have many 20 to 45min runs around here but with the extra power of the Ones I can drop a size with pretty much equal performance (only tried in the back).

[-C-]

8" F, 7" R - seems to work fine for me.

Always used to run 8" front & back, but never really felt the need. When it was time to change I figured it made sense to go for the smaller rotor.

Will see how it holds up this summer with 3 weeks of alpine riding :)

[PepperJester]

With 1.5-3min runs being my local, i run a 6" rear, when i go back to the alps the 8" will be coming back out...all depends on where you ride i suppose (and how).

same here. Our local DH trails are 3min runs tops. I've never had an issue with the 6" rear. I like the little bit of extra clearance it provides just as much as the weight savings.

[- seb]

Dammit, I'm blatantly going to have to buy myself a 6" kit and see how I get on with it aren't I :p and maybe even a 7" for the front - the Formulas are just that damn good (so far anyway)!

[-C-]

I run 6" F&R on my Blur 4x with Oro's & they were more than capable riding a day of DH up at Hamsterley - i'm not sure how they would hold up on anything bigger though. I wouldn't mind trying!

[Socket]

Depends on your riding style.

If you drag brakes a lot, then a smaller brake will heat up quicker and lose power.

If you're hard on your brakes for a shorter time, then smaller brakes will work fine and save a bit of weight.

Totally, 100% agree with this. Braking in automotive/moto applications tends to be much cleaner than on mtbs, you're never dabbing or dragging them, it's almost always either on or off so heat is not so much of an issue, especially on the rear. However with bikes it's very very easy to drag the rear brake, especially on steep terrain, and so you need to be able to dissipate a lot of heat even though the amount of stopping power being generated is nowhere near what the front can do. If you're confident in your ability to brake cleanly then 6" might work for you, but otherwise I think there's almost more benefit to running a larger rear rotor than front. Sounds backarsewards I know, but my experience both with my own bikes and from riding others' is that the rear brakes are more commonly overheated anyway.

[- seb]

I know weights can be found in various places, but since my 180mm has literally just arrived in the post I thought I'd let you know the difference. Formula Oro rotors: 200mm = 177g, 180mm = 136g. 180mm mount is (surprisingly) 2g heavier than the 200mm mount (which is much thinner).

So the weight saving for an Oro/One user is a MASSIVE 37g :p

[lovebunny]

10-20 minute runs.....yeah, I better stick with the 8" rotor

and with how much you drag your brakes you need it:biggrin:

[Zark]

and with how much you drag your brakes you need it:biggrin:

Yeah, you were too busy crashing for your brakes to get hot:shocked: