In this edition of Ask a Wrench, pulled from the members-only segment of the Geek Warning podcast, tech editor Dave Rome and pro mechanic Zach Edwards take on three listener questions. They cover how to save a nearly-new road tire after a sidewall slice, whether you can hack a Cannondale crankset for a 1x drivetrain, and the pros and cons of different tire setups for road, cyclocross, and mountain biking.
Geek Warning is tailored for riders who love to tweak, tune, and push their setups. The answers have been edited for length and clarity—but if you want the full nuance and discussion, you can listen to the complete members-only episode embedded below.
Q1: Craig from Dubbo, New South Wales
“I’m riding a 2014 Cannondale SuperSix. I treated myself to a set of GP 5000s which, on their maiden voyage, I ran over some glass and got a cut in the rear tire. It wouldn’t seal with the Orange Seal Endurance that I use. I put in a Dynaplug, which stopped the leak and got me home. So, I’m curious—on a road tire, would you advise leaving the Dynaplug in place, or is it better to remove it and patch the tire somehow? I’ve left Dynaplugs in place in many gravel and mountain bike tires without any issues at all, but with a road tire, I’m wondering if there’s a difference given the pressures involved. The tires are measuring about 29 across, and I run them at around 74–75 psi.”
A: Zach Edwards
If it’s in a mountain bike or gravel tire, I’ll just leave it in until the tire is worn out. On the road, there’s less rubber to work with, so it depends on where the puncture is. If it’s in the thick part of the tread, it might hold. But if it’s near the sidewall, or where the tread wraps into the sidewall, it’s much thinner there. That spot flexes more during riding, and it’s more likely to start leaking.
If the plug is holding, sure—run it. I’d trim the excess so you don’t feel it. But yeah, it’s always a bit of a heartbreak cutting a brand-new tire. In road setups, the casing has more tension from the pressure. That tension can push the plug out, or start to widen the cut.
A: Dave Rome
Exactly. With road tires, sometimes the plug seals great and becomes a long-term fix. But other times, it just won’t stop seeping. You’ll either get slow leaks or eventually start seeing sealant spray again. In those cases, the foolproof fix is replacing the tire.
That said, I’ve had good success patching from the inside. Clean the area really well and use a generic glueless patch. I clamp it down with a quick-grip clamp—like what you’d use for woodworking—and let it sit for a couple of hours. That helps the adhesive stick properly. I was surprised the sealant didn’t break it down, but I’ve had those patches last the life of the tire.
So, you’ve got a few options. Keep using the plug if it’s holding, but watch for signs like a bulge or raised area at the puncture—that suggests the casing is starting to fail. If you see that, replace the tire. And yes, always carry Dynaplugs. They’re the best emergency fix out there.
Q2: John from Toronto
“What are your recommendations for tire setups by discipline for a competitive amateur racer? For cyclocross, would you suggest tubeless with inserts? For XC mountain biking, tubeless? And for road—tubeless, TPU, or latex?”
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