38c tires on 15c rims?

Adam O

New Member
Aug 15, 2019
A shop installed Panaracer Gravelking 700 x 38c tires on my Ultegra 622 x15c rims. I didn't know anything about tire or wheel sizes, other than I wanted something better-suited for gravel than the skinny tires I was running before, so I left it up entirely to the bike shop to install a tire compatible with my rims. On my first ride with the new tires, I had a blowout that caused me to crash and seriously injure my knee. There was no sign of puncture on the tire and nothing in the road which would have caused a puncture. Based on some charts I found online, it seems like the tire was too wide for the rim. Does anyone on here have an opinion on whether the tire was too wide for the rim? If so, could that have contributed to the blowout? I checked the tire pressure before the ride and it was nominal, and the blowout happened in the last mile of a 17-mile that covered an equal mix of pavement and gravel. Any feedback at all is appreciated. If the shop was in error, I'd like to let them know to prevent anyone else from getting hurt like I did.

I should add that I noticed the rear tire was low on air prior to the ride, and I pumped it up and monitored it over the course of the ride. I thought this was odd because I'd gotten the bike back from the shop only a couple days before and hadn't ridden it yet.


Well-Known Member
Aug 13, 2013
It's certainly possible to run wide tires on narrow rims and I've done it. It's not ideal, but it's not necessarily unsafe.

There are a lot of possibilities for the problem you had, but much more information is needed in order to make an informed guess as to the problem.
  • You say they were "tubeless tires", but were you running them tubeless or with tubes? Are the rims full tubeless or tubeless compatible?
  • Did you check to make sure that the tires were evenly and properly seated?
  • You said you had a "blowout", but that's not particularly descriptive. Did the tire blow off the rim? Is the tire damaged? If so, in what way (failed bead, torn sidewall, large cut in the tread, something else)?
  • You don't specify how much pressure you were running; "nominal" is meaningless to anyone other than you. This is a critical piece of information. Knowing how much you weigh wouldn't hurt, either.