Tire size vs rim size aerogeek

Hello,

Working on HIM…I have seen that it is better to have 23 mm tires on 25 mm rim because when it inflates, the size of the tire is the same as the bigger rim. This makes the wheel+tire more aero.
I just purchased a 25 mm SAT wheel and wanted to know if this is the same for tubeless:
1- Would a 23mm TL tire latch on a 25 mm rim?
2- Would I benefit on a 23mmTL tire on a 25 mm rim?

Thanks,
E-

Depends on the inside width of the rim, but generally yes.

Aerodynamically speaking if the outside width of your rim is 25mm you want your inflated tire to be no more than 23.8mm wide. This known as the Rule of 105. You can read about it on Silca’s blog ( among other places ):

2 Likes

Rule of 105: 25mm tire on 25 mm rim is almost impossible to achieve.
Too bad the new cont 5000 TL doesn’t come in 23mm

Does it not?

I have only seen 25mm and not 23mm for cont 5000 tl

Yeah, that may definitely be true from a practical standpoint. Supposedly they make a 32 GP5k, too, but good luck finding it. You’re correct that Conti don’t list the 23mm on their website.

https://www.continental-tires.com/bicycle/tires/race-tires/grand-prix-5000-tl

More food for thought regarding this in the tire width vs rim width at various pressures attached. We should probably all definitely be riding at less than 7 bar…and 6 is just fine in most cases.


So you’re not far off the rule of 105 with just a 25mm tire at reasonable pressures. Plus, you get a decent rolling resistance advantage going from 23mm to 25mm. So in a headwind you’re probably slightly ahead of the game with a 25mm…at higher yaw angles you may be costing yourself a few watts but nothing huge.

That link isn’t for tubeless. The 5000 TL comes in 25, 28, and 32.