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Discussion Starter · #1 ·
I am planning to upgrade from the BB5 to BB7's. I'm not very happy with the performance of the 5's with 185mm rotors. Is there some kind of "rule of thumb" for choosing a rotor size? I am 185 lbs, do mostly XC with a little all mountain. I would say I am a novice rider but improving.

I can get BB7's with 160mm rotors for $54, with 185mm rotors for $73, or with 203mm rotors for $61.

My guess is that 160's are fine but I don't want to end up upgrading rotors in the future.
 

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Holy Land Rider.
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Hi,

i am 105 Kg and ride 160mm rotors with no issue on both hydro brakes and BB7.
i also ride XC and never encountered and brake fade on the BB7 or no enough bite.
i use SD7 levers.

my dial up is for less modulation and more of a snappy bite. of the BB7 and they do it just fine.
 

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You can use the BB7 with the same 185mm. rotor you are now using. I'd put a 185mm. on the front and a 160mm. on the back.
 

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Bedwards Of The West
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I have the 185's front and back on my 29er commuter. I like them a lot. I'm 215 pounds and always ride that bike with a full backpack. I commute all winter in snow, slush, etc...they have been awesome brakes. The 185 is not 'too much' brake for the back, for me.... I like having the same size rotors on both ends.
 

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I've got 160mm on both F & R, and have no issues (205 lbs before gear). I would feel a little more comfortable with a 185 up front on the long, steep descents.
 

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I think you will get a lot of improvement just from the more solid caliper body and the improved adjustability of the BB7s. I run around 200 lbs, and don't have any issues with 160mm rotors w BB7s on my Karate Monkey.
 

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I use 203 on everything front and rear. I weigh 210, and ride aggressively. I also race cars and the parallel on cars is that the larger rotor gives a more immediate and predictable "bite". More predictable and consistent to your brain.


This is the same on the bike. I also like the same size F-R, and a 203 rear is easier to skid if you need to.

In terms of the weight difference for 2 rotors, it is 8 tablespoons of water. (or urine). Think about that.

Jay
 

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Huckin' trails
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I use 203mm everywhere, and I'm 110#.... I love disc brakes :D

160mm looks silly, 185mm look good, and 203mm looks even better.... But I prefer 185mm rotor to 160mm, mostly for look, and also for better clearance of the braking zone and the hub, so less chance to touch the brake zone when cleaning the wheel...

David
 
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