MegaSack DRAW - This year's winner is user - rgwb
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I have the opportunity to swap from a 160 disk to a 185 disk for no extra charge.
The bike is a 2008 Marin Rift Zone
The brakes are Avid Juicy 5
The fork is a Fox 32 RLC
The shock is a Fox R
is it worth changing to the bigger disk or not, would I feel a marked difference. Riding is XC with some fairly fast downhill sections going on for a couple of miles
You may as well.
There is no sensible reason why you should run the smaller disc.
Go large.
do it, better control and lower temperatures.
unless your a weight weenie, then go to 140s...
180 will look better and as we all know [b][u]looks do matter[/b][/u], e.g. [img] 
[/img] vs. [img] 
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Just upgraded from the standard 160 to a 180 on the front (Juicy 5s) .
160 was fine in the dry on stuff that wasn't steep for a long time, but underpowered in the wet and faded on long steeps.
180 is definitely worth it for the few extra grams.
Cheers Guys, swap them I will then
Def worth it, I had forgotten how much better bigger rotors perform until I swapped current brakes last weekend.
185mm are ideal for most of the riding in the UK. I'd agree that unless your really trying to cut the weight of the bike down 160mm aren't worth having.
The forks you've got will easily be able to handle 185mm rotors, 203mm and your gonna have potential problems (08 Fox 32s' running QR axle)
JB405, why will the OP have potential problems with running a bigger disc?
Float 32s are warrantied for 203mm discs.
I have been running a 203 rotor with a recon qr fork for the last 9 months with no problems.
I run them on everything, Rond, Bomber, Manitou. No issues ever.
I heard that it can put too much stress on the fork legs damaging the forks, this apparently could make your warranty invalid.
I'm regurgitating this so if it's flawed please correct me!
Your only limit on disc size is that covered by the fork warranty.
185mm is the way forward on the front of a bike, saying that I've got 203mm on my Pitch and 185 on the Handjob