Confused with disc rotors....

einriba

Hi all

Please forgive me - I've checked the FAQ, I've checked the disc mount thread and done a search.....but I'm still confused!!

I've got a giant nrs 2 (the 04 model as shown in the photo below)



I got rid of the giant mph hydraulic discs as they kept over heating on descents (I know...don't brake so much...) and replaced them with some hayes mechanical discs. I also crashed (as a result of brakes locking up) so replaced the forks with rock shox reba.

I'm planning on getting back in to mtb'ing after a 3 year stretch of triathlons but really want to sort out the brakes. I've managed to buy some avid juicy 3's very cheap (and they're new!) but am worried that the puny 160mm rotor size will still overheat the brakes. I want to put a 203mm on the front and a 180mm on the rear. I've got a couple of questions:

> What adaptor will I need for going bigger on the rotors? I checked chain reaction and just got lost in what the hell I need.
> When a rotor says "for shimano", is that true? Isn't just a piece of metal? Can you mix say an avid rotor with hayes calipers?


Sorry for blabbering on!!!!

nicklouse

IS to 203 post for the front
and a rear IS to 180 (5) disc dependant.

fork and frame are IS and the brakes are POST.

supersonic

The reason your old brakes cooked was because they were a closed hydraulic system

Open systems like the Avid Juicy are far better at handling heat.

How much do you weigh?

einriba

supersonic wrote:

The reason your old brakes cooked was because they were a closed hydraulic system

Open systems like the Avid Juicy are far better at handling heat.

How much do you weigh?

I'm 71kg.

Are the juicy 3's open then? and what does that mean!!!

supersonic

Means there is a bladder that expands as the oil expands due to heat. You lose the thumbwheel adjuster (at least on this model though).

Larger discs still dissipate heat better, and if you must go that way, as nick says, but possibly overkill for an XC bike and relatively low weight. 180 on the front usually a good bet as more braking is done on the fornt.

einriba

nicklouse wrote:

IS to 203 post for the front
and a rear IS to 180 (5) disc dependant.

fork and frame are IS and the brakes are POST.

Brilliant! Thank you!

nicklouse

but you will not need bigger than 180(5) and 160

einriba

supersonic wrote:

Means there is a bladder that expands as the oil expands due to heat. You lose the thumbwheel adjuster (at least on this model though).

Larger discs still dissipate heat better, and if you must go that way, as nick says, but possibly overkill for an XC bike and relatively low weight. 180 on the front usually a good bet as more braking is done on the fornt.

Ah, thank you.

I do a fair bit of downhill on the bike (or used to!). Did a lot at cwmcarn, machen, afan etc when I was in wales.

More recently I ride at Cann woods near plymouth. So do you think a 180mm on the front and stick to the 160mm on the back with the new juicys?

and is this the bad boy that I need for the front?

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

supersonic

Yep ;-)

einriba

supersonic wrote:

Yep ;-)

Excellent! Thank you folks.

And am I right in thinking that rotors can be mix and matched?....ie hayes rotor + avid caliper?

supersonic

Sometimes. Lots of combos, sometimes the pads will catch the rotor arms, or maybe too thick. Look for the same brand or listed compatibilty to be on the safe side.

MarvintheAndroid

I uprated my front disc from 160 to 180 mm and can confirm that the brake power and modulation improved noticeably.

Marv