26" wheel with road bike brakes.

I'm having new touring frame built. I'm going with mtb 26" wheels, but would like to have Sti shifters. I wonder if the Dual-pivot Caliper Brake for road bike is compatible with wide 1.75" mtb tyres.

 

Maybe, maybe not ... It really depends on at least TWO things ...

1. the distance between the fender mounting holes which you will need to use to mount the brake calipers ...
2. and, your willingness to squeeze a partially inflated tire between the brake pads when installing & removing the wheels
   • this presumes calipers with at least a 49mm-59mm reach ...

If the reach is greater than 75mm, then 'I' think that it will be a dodgy choice because of the probable flex of the caliper arms ... If your MTB frame has mounting bosses for V-brakes OR Cantilever calipers, you can use MINI V-BRAKE calipers with your STI shifters ... However, the issue of indexing may exist if the frame uses a TOP PULL front derailleur ... Regardless, if the bike will really be used for touring then you may want to consider either BAR END shifters or Campagnolo shifters.

 

Thanks for very prompt and kind+ detailed advices. The frame will be custom built, so the mounting holes will be proper.


I'm more concerned with the clearance between the tyre and the brake's pads. I wonder if the quick-release lever will provide sufficient clearance.

 

I absolutely do NOT think that you will be happy with the results of using a brake caliper whose reach is 39mm-49mm like the Shimano 105 caliper which you pictured with the suggested tyre size ...

By my reckoning, the distance between the center of the brake bolt & the underside of the caliper arms is about 3/4" ... so a 49mm reach's tyre clearance is hard pressed at 30mm ...

In other words, YOU are asking the impossible by wanting to fit a 1.75" (44,45mm) tire in a 30mm space ...

Similarly, then, a 49mm-59mm may only have 40mm of clearance & also be woefully unsatisfactory.

So, even the Shimano & Tektro LONG REACH (49mm-59mm) brake calipers won't work for the suggested tyre size which you plan to use

If you are planning to use the bike for TOURING then I would really be shooting for more than a 63mm REACH between the brake bridge & the center of the rim's brake surface ...

You probably need to add another 1/2" to 3/4" reach if you want to be able to fit mudguards on the bike.

• I think that the next size up on dual pivot calipers is 63mm-75mm ... and so, something close to 72mm is what I would be spec'ing for the reach

BTW. The distance between the caliper arms & the tyre's sidewalls should be "okay" ...

Having the fork spec'd with a 50mm rake will probably expedite fitting the extra-long dual pivot caliper & the 1.75" tyre to some extent.

 

I guess I don't see much advantage to 26"x1.75" MTB tires on a touring bike. If this is going to be on the road, they will provide LESS traction, not more, and only make the ride more work with only a marginal gain in comfort. You might look into hybrid tires if you're looking for comfort and durability for touring.

 

Bundle of thanks for detailed advices. Of course, I have desires, but I live with reality, that's why I seek expert advices here./img/vbsmilies/smilies/biggrin.gif Actually, I'd go with 1.5" tyres, but quoted 1.75" so I'll have room to play with. In the end, I think I"d probably go with tried & true center pull brakes,


and get the Sti shifter and 26" wheels. BTW, I don't need mud guard. I only plan to tour in the dry season. Also the load I expect to carry will be a bit less, since I'll mostly doe credit card type touring( sagged).

 

Good. Either the traditional Cantilever Brake Calipers or the previously mentioned Mini V-Brakes will probably be the most satisfactory for Touring ... particularly, if you do not anticipate riding on wet roadways or when it is raining ...

• I am NOT keen on disc brakes on Road bikes even though about a dozen years ago I had asked Richard Schwinn (WATERFORD / GUNNAR) if he could cobble up a GUNNAR frame for me with disc brake mounts ... at the time, he said he couldn't, but that they had actually begun working on the possibility for future frames ...
• nonetheless, if your framebuilder has also fabricated MTB frames in the past then consider having him/her add a disc brake mount to the frame's stays BECAUSE you never know what your future 'needs' may be ...

• spec 135mm rear spacing
• and, even if you are going to have Cantilever Brake bosses on the frame, I think that you should would ask your framebuilder to set the brake bridge at the previously mentioned height of ~70mm (?) above the brake surface (c-c) of a 26" wheel's rim (~8.9mm/[3.5"] actually seems to be the "norm")... plus, have the forward facing hole large enough to accept a recessed brake mounting nut ... 8.0mm might be better ... but, discuss it with your framebuilder
• BTW. there are some racks which use the cantilever brake mounting bosses as the mounting point, so if you do go with a dual pivot brake caliper, the cantilever brake mounting bosses do not have to go unused ...

Regardless, unless you are only 4'10" tall, then you may really want to give some serious consideration to 700c wheels & tyres ...

• if you are sub-5' tall, then you may want to consider 650b wheels & tyres.

 

Thanks again. Will do per your recommendation. I'm5'7'. The reason for wanting 26" tyres is because they're more available thru out the country. 700c tyres are less available, and generally in 23. Frame and forks will have plenty of bosses and mounting eyelets. Heaps of thanks again.