Everybody knows that the recommended tire clearance is 4mm, or “one rock and it’s over.” However I’m wondering if this year’s Roubaix has anyone rethinking running overspec tires on their road bike.
Of all races, I would think that Roubaix has the HIGHEST risk of a rock getting caught in a fork. However, despite all the focus on tire choice at this year’s race - in particular Tadej’s 38mm WAM on a Y1RS rated for 32mm - I didn’t see any reports of frame damage or crashes due to debris caught in overspec tires.
You might say - “Pogacar doesn’t pay for his bikes, he doesn’t care if they’re damaged.” True, but would they risk a crash on this race if it was that likely? At best he’d need a bike change (not easy, see Van Der Poel), at worst he goes over the bars and crashes on his face.
Of course everyone has their own risk tolerance, but I wonder if the actual risk is being over-estimated. Maybe we’ve taken a standard (4mm) and assumed probability. Or, maybe the risk increases until you go WAY overspec, and there’s not enough enough room for a rock to get in?
I’m going to try going overspeed, just a bit. My Time ADH is rated for 28mm. 32mm tires spin freely but are probably as tight as Pogacar’s 35s on the YiRS. I’m going to add some paint protection film to the fork and chain stays, mount a set of 30s and give it a shot.
I’d just be wary of the tire “growing” with time. On a Look 595 I had, I mounted 28mm GP5000 clinchers, and they spun freely. After a couple of weeks of riding, though, the front tire started rubbing the underside of the fork crown, so I had to go back to a 25mm on the front. That was a rim brake bike though.
I suspect you’re right - apart from front fenders (which can crumple and get sucked forward) the risk of a perfectly-sized pebble sticking to the tire all the way up,and getting wedges, seems very small.
I wonder if the received wisdom comes from liability-possibility analysis (to shops and bike companies) or from an actual sense of risk rates.
Another possible/related source is what happens if you break a spoke. Which is much different these days since some QC improved so much, rims got much stiffer. But it seems plausible that Van Ghils’ crash in the finale of Classica Jain was caused by his front wheel locking to (and not really by the UAE rider deviating), which could have been a broken spoke.