31 January 2018 ~ 0 Comments

How To Add More Tire Clearance To Your Road Bike — DYI

For the past many years I have been using the Continental 4000S II tire in 25mm width on all my road bikes. After a tough 1000K this past summer, I wanted to try out some 28s and see if the ride was better. During the winter of 2017–18 I started experimenting with 28mm 4000S tires on my Trek Domane. Although they fit, the tolerances were very tight. I also wanted to use the set of full-length Bontrager fenders with these tires. For the rear tire, I have plenty of space behind my bottom bracket, near the chain stays, but oddly enough, the room below the brake bridge was tight. It left little room to spare (yet my stock Ultegra brake had plenty of adjustability). I inquired into having a custom frame builder move the bridge up a few millimeters, but the cost was $800 — way too much.

I came up the idea of taking either a small piece of wood or plastic and epoxying it inside the drop-outs. In my business I have lots of 1.5mm (.062″) HDPE scraps, so I took a piece of plastic, about 5 x10mm and bent it gently and glued it in place, making a shim of sorts. I also filed it down so the edges so they were smoother. I have done this on two of my road bikes, my Trek Domane to accommodate 28mm tires and also my Cervelo P3C TT bike (on the front fork only) so I can get 25mm tires on that frame. Because the skewers are pushed down a little more, I am most careful about tightening a lot now. (On the Domane I have to crank them down a ton anyway, otherwise it creaks!) On the Cervelo fork, I filed down the lawyer-tabs so they were smoother, as the fit was too funky without doing that.

With the 700c x 28mm 4000S tires I am getting width measurements of between 29 and 30.5mm on an 18mm I.D. alloy rim.

I have only had these in place for a few months now, but so far, it is working. Time will tell, but, it is better than investing $5,500 on a new carbon-fiber Domane with disc brakes!


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