[SinglePivot]

I ran one on my X5 for the weekend. Lots of power that is fine on flat or mildly steep terrain but just way too much power for steep terrain. Very hard to modulate. It becomes on/off. I had issues with some very strange and extremely noticeable chatter with it also. I checked it after the first day and the bolts holding the caliper had worked loose. I tightened it and thought that was the problem but the next day the chatter was still there. Anyone experience this? Brakes are hayes HFX-9, hub is a WTB Speed Disc, koolstop pads.
I took it of after that weekend since it was too powerful and am curious about 185mm rotors. Just looking for a tiny bit more bite in the back. Maybe the 8" rotor + 2.5" tire would have worked better than the 2.2" tire I had back there.

-Sp

 

[FoShizzle]

seems odd.....i see no reason to not run an 8" rear rotor, other than weight savings.

i ran 8" rotors front and back on my Bullit using Hayes and NEVER had an issue; worked flawlessly.

 

[SinglePivot]

Weight distribution from the bullit to x5 is different for a given size. The bullit has a shorter front center so when you lean back you can get more of your weight over the rear tire. I think it is partially the smaller tire I am running also. I have a harder time tossing the rear around on the x5 so I went to a smaller tire (less traction) that has seemed to help that issue a great deal. But my main concern is the chattering.

-Sp

seems odd.....i see no reason to not run an 8" rear rotor, other than weight savings.

i ran 8" rotors front and back on my Bullit using Hayes and NEVER had an issue; worked flawlessly.

 

[icegeek]

8/7 maguras. nothing but sweetness, and none of those racerboi tires.

 

[ajr]

I ran one on my X5 for the weekend. Lots of power that is fine on flat or mildly steep terrain but just way too much power for steep terrain. Very hard to modulate. It becomes on/off. I had issues with some very strange and extremely noticeable chatter with it also. I checked it after the first day and the bolts holding the caliper had worked loose. I tightened it and thought that was the problem but the next day the chatter was still there. Anyone experience this? Brakes are hayes HFX-9, hub is a WTB Speed Disc, koolstop pads.
I took it of after that weekend since it was too powerful and am curious about 185mm rotors. Just looking for a tiny bit more bite in the back. Maybe the 8" rotor + 2.5" tire would have worked better than the 2.2" tire I had back there.

-Sp

I think if you were to run an 8" rotor fulltime you would have to upgrade to a HD swingarm as it puts a greater stress into it than a standard one was designed for. I think as weight transfer puts the main bite on your front tyre a larger than 180 of 190 is not needed. I have X5s with both and dont feel any benefit with a disc above 180mm. I feel front disc size is much more noticeable and have a 210mm on one and a 200mm on the other.

 

[FoShizzle]

good points

 

[Soupboy]

No clue as to what the chatter might be attributable to - rotor/stays, rotor/caliper?

8" is a lot for a rear brake unless you're a dedicated DH rider and need the bigger rotor for better heat dissapation. Otherwise it just adds weight. I've never run more than 8"fr/7"rr and typically prefer 8"fr/6"rr. You're rear brake isn't doing too much anyways.

Having a full 8" out front is always a good thing.

 

[SinglePivot]

That rear brake does a lot more than most people think. With the 8" rear rotor, I was either on or off so I relied more on the front brake. Let me tell you it was much harder to slow down and setup for corners. Ended up carrying too much speed through the corners and would just totally screw them up. Not to mention my front rotor is nice and brown right down the center of the rotor.

-Sp

You're rear brake isn't doing too much anyways.

Having a full 8" out front is always a good thing.

 

[FoShizzle]

just an idea....you may want to post this as well on the Turner forum. Word on the street is that both Squeaky Wheel and Aquaholic really like 8" in the rear, not that there is anything wrong with that.

 

[Soupboy]

That rear brake does a lot more than most people think.

I go (gulp) now >260# and have ridden down some extensive DH. I also ride a 29er which provides more leverage for the brake to stop. Rear brake power is not an issue. I can lock up a 6" rotor if I want to. Modulation is a non-issue either. It is all about dumping heating during protracted braking. Sure, you can have your preference and if doing a lot of DH why not go with an 8" rear. For those that spend as much or more time going up hill or on rolling terrain vs. strictly DH an 8" rear is overkill. Bikes are no different than cars - your front brake is doing the vast majority of the work. Once your rear tire loses adhesion it is doing zilch for you other than maybe acting as a rudder. Skid steering is fun.

 

[ajr]

just an idea....you may want to post this as well on the Turner forum. Word on the street is that both Squeaky Wheel and Aquaholic really like 8" in the rear, not that there is anything wrong with that.

Always remember to use some form of protection when practicing 8" rear braking. Just a few moments of wild braking with 8" in the rear can lead into a world of pain.