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This could be a really dumb question...
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This could be a really dumb and obvious question, but I figure it's better to ask than to risk having a bad incident out on the road in the middle of a pandemic!

Is there any risk in running a clincher tyre that comes up marginally narrower than the rim once mounted and inflated?

These are the specifics:

Rims: Roval CL64 (disc-brake)
Tyres: Continental Grand Prix TT (23 / 25 mm - front / rear)
Tubes: Vittoria Latex
Pressure: 80 psi

So the Roval CL64s were a new purchase this year and the Continental GP TTs are my "summer-best" tyres; I've just fitted them and the wide rims of the CL64s mean that the 23 mm tyre that I'd normally run on the front actually comes up ever-so-slightly narrower than the rim itself, probably <1 mm each side.

I've never come across this scenario before and just wanted to check that it's not going to explode or roll off the rim when I hit the road tomorrow?!

Furthermore, am I going to see massive aero gainz and suddenly save 10W for holding the same speed?!

Many thanks
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Re: This could be a really dumb question... [awenborn] [ In reply to ]
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That's actually exactly what you want, purely from an aero perspective at least. The commonly accepted rule, touted primarily by Josh Poertner, is that you want the rim width to be 105% of the inflated tire width. So pretty close to what you're measuring there. Hard to know exactly what you're looking for without calipers to measure the tire though. 10w? Probably not? A watt or two? Probable.

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Re: This could be a really dumb question... [realbdeal] [ In reply to ]
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Thanks for the reply, that's really helpful!

I was aware that a "lightbulb" profile is a big aero no-no, but didn't realise that you probably want to go slightly the other way. Do you have links to any articles about that, because I'd be interested to read a bit more.

I do have some vernier calipers but even then, it might be difficult to measure accurately because the CL64 rim profile appears slightly narrower at the bead and then bulges out slightly before tapering down towards the spoke-bed. I guess the 105% is only a rule-of-thumb and every tyre-rim combo is going to be unique but it's nice to know that I'm in the right ballpark.

And yes, the 10W was a slightly tongue-in-cheek comment(!) but I'm always optimistic :D
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