35mm tire on 21 internal rim or 33mm on 25 internal?

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Mr.Gib
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by Mr.Gib

Which is better?

Mrs Gib needs new gravel wheels (hooked) and her gravel bike only has clearance for 36mm WAM tires. My instinct is to go with the wider rims for future proofing, but I assume no 33mm tire will have been designed with that rim width in mind. Might be fine but I defer to the wisdom of the gravel crowd.

Tire choice is likely Michelin Power Gravel, or Terreno Dry.

FWIW Mrs Gib is light - 105lbs/49kg.
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

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frnchy
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by frnchy

I use 30 mm on 25 internal with no problem, and it feels great. I've also used 35 mm on 25 internal for my gravel bike this past winter and again it's been great. IMO the straighter sidewall from narrow tire + wider rim promotes sidewall flex, up to a point - I used 28 mm on 25 internal for a while and the sidewall was a bit too exposed and cornering didn't feel quite as good as 30 mm.

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jcrr
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by jcrr

Hope this works as another data point for you, and please don't judge my choices, but I've been happily running Spez Roubaix 32mm tires on Mavic Crossride 21mm internal for tens of thousands of training miles, on/off road. The tires balloon out to 36mm when mounted. I have run them anywhere btwn 45-90psi.
"If it ain't broken, it could be lighter"

warthog101
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by warthog101

I've got a 28mm p zero tlr on my front WR50 hookless.
25mm int width.
It's been fine.

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Mr.Gib
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by Mr.Gib

Thanks for the input guys, but my concern is not so much if it works (on the road I run 28mm 5000TR on WR50's :wink:), but rather about rim protection from rocks, etc. with a 33mm tire on the wider rim. A 33mm tire will probably blow up to 35 on the 25 internal rim. That gives scant side protection for the rim's 32mm external dimension. Wonder how the rim would fair on coarse gravel.

And there is the issue of tread design. A 33mm tire on 25mm internal will be "opened up" probably more then the designer intended. Could one end up on the side knobs when running straight more than desired? Could handling and traction be less then optimal? I suspect this would be very minor if it is an issue at all but I really have no idea. Curious if anyone has done this.
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

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cerro
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by cerro

I would say 35mm tire on a a 21mm rim. More comfort with a bigger "bubble" and 33mm tires are mostly made for cx so more focus on grip than rolling and comfort.

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