Dogma and tire sizes
Moderator: robbosmans
Best way is to try it. From the pic I'd say a 25mm tire on that rim in that fork with that brake would be fine. Keep in mind that the same clincher tire will sit higher on a wider rim than a narrower one if height is an issue. There are just so many combinations of tires, rims, and clearances and brakemounts around that your best bet is to just try it in your situation. Tubular tires will not vary as much since the only thing affecting their ultimate inflated size and shape is the casing they're enclosed in and to a lesser extent the shape of the rim bed they are glued to.
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Honestly tyres don't sit higher on wider rims how canit the ETRTO is 622mm which is the same for all rims.
Different tyres come up at different heights though. Conti tyres are taller for the "same width" compared to Vittoria's but the actual width is rarley the same. For example the GP4000s is 1mm or so taller than the open corsa on the same rim.
Different tyres come up at different heights though. Conti tyres are taller for the "same width" compared to Vittoria's but the actual width is rarley the same. For example the GP4000s is 1mm or so taller than the open corsa on the same rim.
Tire cross sections have a larger circumference on wider rims so they come out wider and taller, at least in my experience from MTBs and road bikes.
ETRTO specifies the rim, not the tire. Take out a tape measure and check.
To the OP, looks like 2mm more should be fine. Do you have the same clearance in the rear? Chainstay rub can be an issue under power.
ETRTO specifies the rim, not the tire. Take out a tape measure and check.
To the OP, looks like 2mm more should be fine. Do you have the same clearance in the rear? Chainstay rub can be an issue under power.
The same clincher tire will be higher on a wider rim than a narrower rim because it no longer has to conform to that "hourglass" shape. The whole idea behind the wider rims is to let the clincher go straight up at the sides instead of "out and up", making it more "aero" (god I hate saying that). Given the same width tire bead to bead, it will create a greater overall diameter on a wider rim than a narrow rim, even though the ETRTO is identical on both. Put a 25mm clincher on a standard size rim and inflate it and put it in a bike you know to have very tight clearance. Now take that same tire and put it on a wider rim, say like and Enve 3.4, HED Belgium or something, and put it in the same tight clearance frame. I've seen where the tire mounted on the standard rim will clear the brake bridge yet that same tire on the wider rim will not.
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I have the oppostie experience and with tyres on narrow rims and the same tyre on a wider rim. They do spread and I like that but I have not noticed a height gain. The width bead to bead is wider on a wider rim compared to narrower one so I really don't follow that bit of what you are saying. I think it may depend on the tyre as some tyres spread more than others.
Not a lot of space between the chain stays on a 60.1. Less space than under the fork crown iirc.
bm0p700f wrote:I have the oppostie experience and with tyres on narrow rims and the same tyre on a wider rim. They do spread and I like that but I have not noticed a height gain. The width bead to bead is wider on a wider rim compared to narrower one so I really don't follow that bit of what you are saying. I think it may depend on the tyre as some tyres spread more than others.
When I said the width bead to bead is the same, I'm talking about the tire width measured if you were to spread the tire out flat and measure bead to bead, unmounted on a flat surface. Not the distance between the beads when mounted. That distance is of course, as you point out, always going to be wider on the wider rim.
Let me take one more stab at explaining it. And keep in mind that we're talking clinchers only here. If you take a 25mm tire, mounted on say a 20.5mm Campy Neutron rim, it will have a bulbous shape upon leaving the bead of the rim (the hourglass shape that people talk of). Now if you spread that rim bead width out a bit, that same tire will take on a more "dome" like shape. It effectively goes straight up from the bead instead of out and around as it does on a narrow rim. That straight up shape is what the aero pundits go "ooh ahh" over and claim they are so much faster because of it. But let's ignore that part for purposes of this explanation because I can't help laughing when they talk like that.
At the width where the clincher tire can go straight up on the sides, that's where the tire will have it's greatest overall circumference. If you were to keep expanding that width beyond that point, that same tire would start to spread out and the overall circumference would start to become smaller again. Hope that makes sense, as far as the changing tire height with respect to clinchers and different rim widths.
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