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Daily Archives: December 4, 2019

Gravel and Dirt Road Cycling: Maximum Tire Width and What to Do If Your Tires Rub the Chainstays

I had a problem with my 2017 Specialized Diverge. The bike is said to take 32 mm tires.

Sure enough, 32 mm tires do fit. Barely.

Sadly, when one takes a corner, the tires flex ever so slightly and the edge of the tire can run the inside of the chainstay. Add mud and guess what you have? A grinding wheel.

I wore a nice little groove in my chainstay without knowing I’d done it. That is, until I got home and cleaned the bike.

To fix this, I thought about getting the same tire, but in 28 mm for the back.  I’d run a 32 up front, where it fits, and a 28 in the back. No big deal, another $50 for both gravel bikes…

First I had to have the frame looked at by someone who knows a lot more than I do about bike frames. It was recommended the groove be filed out, flush, thereby making the frame smooth again.  The idea is, with a grove in the aluminum, every single movement the frame goes through, ends right at that groove, where the frame is now weak.  Filing it smooth “fixes” this.  He then applied primer and a coat of flat black paint.

He recommended, rather than a different tire, grinding the side edges down so the tire can’t hit the frame…

Those are my winter slippers, by the way. I didn’t turn into bigfoot. Or a werewolf.

He recommended a grinding wheel, but I don’t have one, so I improvised. 80 grit sandpaper and a wood block… turn the crank real fast, apply the paper, and Bob’s your uncle – in about five minutes.

I gave the wheel a little flex to make sure it wouldn’t rub the frame, and I should be good… and now I can give that girl a bath.

Dirt riding is a delicate balance between traction, rolling resistance, speed, and effort.  Classic road bikes are easier in this regard. With a road slick, you choose between suppleness, rolling resistance, and cornering grip.

With road tires, suppleness is important because it takes some of the shock out of the asphalt.  On dirt roads, suppleness is imperative.  Traction on paved roads is important, but if you’ve ever slid on sand on a paved road, you know how much more important traction is on a dirt road.

I’ve ridden slick(ish) 28’s on my gravel bike and I really don’t like them.  They were all over the place on anything by pristine dirt roads.  The Protek Cross tires are fantastic for riding dirt and I liked the extra 4mm of width – and I didn’t want to give up traction to go with a smaller tire, so working the rough edges off made a lot of sense… and it saved my Fifty Bucks in the process.