30mm tires with Shimano direct mount brakes?

[dreikant]

Has anyone ever tried to mount 30mm tires on a roadbike which uses Shimano's direct mount brakes (e.g. Dura Ace BR-R9110 or Ultegra BR-R8010). The official maximum tire width is 28mm. I was wondering if it is possible to mount slightly wider tires.

[samarskyrider]

I'm running BR-9110 on Tarmac SL6. 28mm tire on 21mm rim ballooned to 32mm - fits okay, but I wouldn't go more than that


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[pdlpsher1]

The tire clearance limitation on rim brakes is based on the positions of mounting holes (i.e. the bike frame/fork), not the brakes themselves. The higher the mounting points the additional vertical/horizontal clearance. The same brake mounted on two different bikes will likely have two different clearances. When it comes to direct mounted rim brake tire clearances, Colnago is the worst and Trek is the best. For example, a Trek Domane fork can clear a 32mm tire with room to spare. This is due to the fork's long ATC (axle to crown) distance which allows the brake attachment holes to be higher and further from the front wheel's axle.

[samarskyrider]

Problem is side clearance, not top. With 30mm+ tire is very close to mount bolts of DM brakes and it has little to do with vertical clearance






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[pdlpsher1]

Vertical and horizontal clearances are both increased when the mounting holes are higher. The higher mounting holes raise the pivot bolt. The position of the mounting holes vary by the frame/fork. To illustrate my point, do you see increased clearance if you drop the wheel by 5mm?

[DHG01]

Vertical and horizontal clearances are both increased when the mounting holes are higher. The higher mounting holes raise the pivot bolt. The position of the mounting holes vary by the frame/fork. To illustrate my point, do you see increased clearance if you drop the wheel by 5mm?

Very useful; thank you. We were taking about exactly this topic on Foromtb. Would the Trek Emonda fork have similar clearance? The Axel to crown distance is about 1cm more than the standard 368 mm.

[samarskyrider]

Vertical and horizontal clearances are both increased when the mounting holes are higher. The higher mounting holes raise the pivot bolt. The position of the mounting holes vary by the frame/fork. To illustrate my point, do you see increased clearance if you drop the wheel by 5mm?

I see a point, but there is little I can do


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[dreikant]

I can clearly see now how the position of the mounting holes affects the tire clearance. Thank you for providing insight into that.
I have a Tarmac SL6 and currently run a 26mm Turbo Cotton tire on a rim with 17mm internal width. With this setup I have very little side clearance left. I guess, that a 28mm tire really is the maximum for my Tarmac SL6 setup. If I am not mistaken Specialized claims that the Tarmac SL6 Rim Brake can fit tires up to 30mm. But I guess that they refer to tire width when mounted. So for example a 28mm Turbo Cotton tire which effectively measures to 30mm when mounted.

[greycat]

I ran 30mm gp5000 on 18/19 inner rims with 8010 direct mounts last weekend. They fit close enough I made sure rims were true. The tires are closer a couple mm to non-cable side of brakes.

On my chainstay dm 6810 or 9110 they could handle much larger tires. The chainstays/seatpost have been the limiting factor for tire size. Simply if the brakes are mounted under the frame then the bike was probably designed for aero.

[dreikant]

Which frame do you have? The non-cable side of my brakes are also a little closer to the tire. In the rear I got a little bit less space than in the front.

[Mr.Gib]

@dreikant, you might also be able to buy yourself some additional space with Cane Creek EE brakes. They really seem be designed to maximize clearance. The material around the pivots, like the rest of EE, is quite "lean".

Off topic, anyone else wondering about the exact pronunciation of the dreikant?

[pdlpsher1]

Vertical and horizontal clearances are both increased when the mounting holes are higher. The higher mounting holes raise the pivot bolt. The position of the mounting holes vary by the frame/fork. To illustrate my point, do you see increased clearance if you drop the wheel by 5mm?

Very useful; thank you. We were taking about exactly this topic on Foromtb. Would the Trek Emonda fork have similar clearance? The Axel to crown distance is about 1cm more than the standard 368 mm.

I have a Domane fork and the CTA is 380mm and the rake is 48mm. They have several vesions of varying rake but the CTA are all the same. It's possible that the earlier version with DM brake has less CTA, that I'm not sure of. I have a Domane fork but not a Domane bike. I purchased the fork separately from Trek to go with my custom Ti frame which has a DM brake on the rear. On the rear I made sure that the mounting holes are raised to give the maximum tire clearance.

The reason why I point out that the positions of the mounting holes matter is that the same brake on two different bikes will give two different clearances. Hence when asking for tire clearance one has to specify the brake and bike model.