I ride a 2024 Factor Ostro with BlackInc wheels.
I know the frame is optimized for a 28mm tire, but it will fit a 32 easily.
I know the wheels’ 21mm internal width is not ideal for a 32mm tire, but these are the wheels I have.
And I wanted to try 32mm, so I put 32mm GP5k’s on them.
Generally I like this for the grip and being able to roll at 60psi, but I don’ have experience on wider wheels. Cornering feels a bit sluggish but I may no
Just curious - exactly how suboptimal is this? Exactly how different would the bike handle with, say, a 23mm IW wheel?
The biggest area where your setup will be sub-optimal is aero…but you are gaining in other areas (comfort, cornering, Crr, etc). Do those things offer the loss of aero?
Sounds like you prefer the setup, so roll with it. You’re not likely to notice any huge difference in feel with a 23mm wheel.
I have rocal rapides that are optimised for a 26mm tyre. They also have a 21mm internal width from memory. I run 30mm GP5ks and find it to be a great setup. Bike is very smooth and still feels fast. I’m sure there may be a marginal aero loss but I doubt you’d notice.
Going far beyond the rim width a tyre is designed for can have the unfortunate side effect of making the part of the tyre designed for contact during cornering … err … not. Obviously not something you want.
I put Limus tyres on a 22 mm internal width rim and they came out at nearly 36mm wide over the 32 they should be. The profile of the tyre definitely looked odd as well.
21mm internal not optimized for 32mm, yet here we have Scott slapping a 45mm tire on a 21mm internal wheelset on their gravel bikes
I wouldn’t worry about it, and the wider you go the more sluggish cornering will feel, in general, because the tire tends to tip over less since it’s rounder. The biggest advantage (unless you want to aero optimize of course) of a bigger internal width is more air volume = more comfort.
That is very good advice… when I was very poor and parts binning everything I initially set up my Karate Monkey with 2.0 inch Maxxis MTB tires on Mavic Open pro road wheels. No problemo. I followed up with a 29 x 3.0 inch Knard on a 21 mm MTB rim also with no problem. Actually raced it at Singlespeed nationals.
Let’s just remember (or know) that in the not too distant past; if you asked a rider what the internal width of their rims is they would look at you with a blank stare. We are in a bit of a golden age with options for wheels and tires right now but let’s not over think it. 65 PSI might not feel sluggish in the corners.
According to ISO 5775-1 the design rim for a 32mm tire (in this case a 32-622) is 21mm. For every mm increase or decrease, the tire’s section with will change by 0.4 the difference from the design rim. What plenty of wheel (rim) manufacturers fail to clearly communicate is if the combined aero performance of the tire + rim is an in-service measurement of 'XX’mm is optimal or if the ISO size of the tire is optimal.
"With all tires adjusted to air pressures that result in roughly the same comfort level, we see that all tires now perform nearly the same. "
“Our conclusion for road bike tires is that there is nothing to gain in rolling resistance when moving to rims wider than 72% of the (specified) tire width.”
“Peak rolling resistance performance seems to be reached when the rim width is somewhere between 65% and 75% of the specified width of the tire. Our other conclusion is that a rim width that is within 50 to 80% of the specified tire width results in performance that is within 99% of peak performance.”
Your 21mm internal rim width with a 32mm tire is a 65.5% ratio which, according to bicyclerollingresistance.com, would put you within the top 1% of peak performance in terms of rolling resistance.
