25mm tyre clearance issue with Ultegra 6800 rear brake
Moderator: robbosmans
Hi all,
I have 2012 CAAD10 and decided to try 25mm clincher tyres and simultaneously put Shimano Ultegra 6800 brakes. If I recall correctly, I had read somewhere (but can't recall really where) that this new model offered better setup for 25mm tyres. Unfortunately, this is not my case.
I run 25mm Continental GP4000s tyres, I inflate them to 7.5 bars. Then there is very small clearance. I haven't measured it, but maybe 2 or 3 milimetres (see photo), which I consider to be not enough. Yes, there is still space and the wheel rotates smoothly, but when something sticks on the tyre during the ride (gravel, e.g., from hot asphalt), it runs into brake and scratches it.
It may be problem of the frame, the hanger for brake is too low and the frame may be "little bit old" for 25mm tyres. At the front, tyre and brake are ok, only the rear is the problem.
Please, is there any way how to tune it to get more clearance? There are 2 screws on the brake but none of them seems to solve the problem.
Thanks.
I have 2012 CAAD10 and decided to try 25mm clincher tyres and simultaneously put Shimano Ultegra 6800 brakes. If I recall correctly, I had read somewhere (but can't recall really where) that this new model offered better setup for 25mm tyres. Unfortunately, this is not my case.
I run 25mm Continental GP4000s tyres, I inflate them to 7.5 bars. Then there is very small clearance. I haven't measured it, but maybe 2 or 3 milimetres (see photo), which I consider to be not enough. Yes, there is still space and the wheel rotates smoothly, but when something sticks on the tyre during the ride (gravel, e.g., from hot asphalt), it runs into brake and scratches it.
It may be problem of the frame, the hanger for brake is too low and the frame may be "little bit old" for 25mm tyres. At the front, tyre and brake are ok, only the rear is the problem.
Please, is there any way how to tune it to get more clearance? There are 2 screws on the brake but none of them seems to solve the problem.
Thanks.
Last edited by martinko on Sat Sep 13, 2014 8:52 pm, edited 1 time in total.
can you provide another angle to compare? I think you may not be putting enough space between the brake and the bracket (you may need a spacer/longer nut to push the caliper out). My wife is running 25c tires with Ultegra 6800 calipers with no problems.
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different frames have the ss bridge and brake mount in different places. just because one frame fits the same tires with the same brake doesn't mean another will. not to mention the variance with tire sizes from that marked on the sidewall, or the true size mounted to the rim.
i did have an old frame that had trouble clearing some bigger tires with the brakes and what i did was clamp the wheel into the dropouts 2 or 3 mm from resting completely in the drops. rode for a few thousand mi without dying. so id suggest that, though I'm sure others wouldn't. ymmv and whatnot.
i did have an old frame that had trouble clearing some bigger tires with the brakes and what i did was clamp the wheel into the dropouts 2 or 3 mm from resting completely in the drops. rode for a few thousand mi without dying. so id suggest that, though I'm sure others wouldn't. ymmv and whatnot.
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Thats enough clearance.
Bikes will ALWAYS get scratched on down tubes and under brakes due to stuff flicking up. Normal and not a worry mate.
Bikes will ALWAYS get scratched on down tubes and under brakes due to stuff flicking up. Normal and not a worry mate.
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Some ways of getting more space:
Inflate to 6 bar and enjoy the extra comfort (unless you weigh 90+ kilo, 25mm doesn't need 7.5 bar. Even 23mm doesn't need 7 bar, but I see you have some uncomfortable tires with the Continental, so probably you won't gain too much on the comfort side of things.
Get the widest rims.
Inflate to 6 bar and enjoy the extra comfort (unless you weigh 90+ kilo, 25mm doesn't need 7.5 bar. Even 23mm doesn't need 7 bar, but I see you have some uncomfortable tires with the Continental, so probably you won't gain too much on the comfort side of things.
Get the widest rims.
caadforce wrote:I couldn't run gp4000 or Michelin pro 4 in 25c on my caad10. Bontrager R3 fit with plenty of clearance
25mm Pro4 Service Course tires are actually 28mm wide. Thats the reason you couldn't run them I guess.
Here is a photo of my 25mm Pro4 tires on Ultegra 6800 brakes and HF-FM066SL frame. 80PSI...
So I think frames are more important than the brakes...
I find the CAAD10 quite stiff and uncomfortable in the BB.
I'm still feeling echos 2 days after a 150km ride.
I'm still feeling echos 2 days after a 150km ride.
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TIP: Here's another tip. In reference to the post above which says the rear tire/tyre will throw dirt, sand, water up on the calipers, the same is true of throwing dirt, sand, water onto the back of your seatpost/seat tube. After awhile, this 'gunk' will 'weld' the post into the tube. Solution, use some electrical tape and wrap the opening to prevent anything from getting inside.