Clincher tire profile height difference on 14C vs 19C rims
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Clincher tire profile height difference on 14C vs 19C rims
Assume one mounts the same 35mm wide tire on a 14-622 vs 19-622 rim. It is often discussed that the actual tire *width* when mounted on a wider rim grows by measurable millimetres. Has anyone tried comparing the profile height difference? Is it negligible or reaching beyond 2mm?
I am asking because of mudguard clearance issue in a fork which seems to attract sticky mud right around the cantis area and above, while there’s no problem with the rear wheel which seems to have perhaps only 2mm extra vertical clearance. I tried to move the mudguard as high as possible even filing off some bracket material to get where it is now but that’s very much where it touches the fork already.
I am asking because of mudguard clearance issue in a fork which seems to attract sticky mud right around the cantis area and above, while there’s no problem with the rear wheel which seems to have perhaps only 2mm extra vertical clearance. I tried to move the mudguard as high as possible even filing off some bracket material to get where it is now but that’s very much where it touches the fork already.
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Fair enough, though the tires cross-section is not exactly circles and squeezing it in "diameter" does not cause the "excess" material to disappear but protrude. There are the classic bulb-shaped diagrams with the "too narrow", "just fine" and "too wide" scenarios, but they always focus on width only.
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There are articles about this if you search on Google. There are also a few forum threads.
I imagine the tire width could maybe increase up to 2mm if you're increasing the rim width by 5mm.
The height, don't know, I think it depends on the circular cross section of the tire. I would guess that the height may decreased a little bit, but it could also increase. You could also cut some notches into your fenders, so that they can get around the fork welds and sit further up and away from the tire for more clearance.
I imagine the tire width could maybe increase up to 2mm if you're increasing the rim width by 5mm.
The height, don't know, I think it depends on the circular cross section of the tire. I would guess that the height may decreased a little bit, but it could also increase. You could also cut some notches into your fenders, so that they can get around the fork welds and sit further up and away from the tire for more clearance.
Last edited by tomtomtom123; 01-15-20 at 02:36 PM.
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The "height" increases as does the width. This graphic has been posted many times. There is no reliable way to calculate as tires respond differently.
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A 35mm tire on a 19c rim is probably closer to being standard per ETRTO standards and would be likely closer to nominal sizing than on a 14c rim. That said, I don't know enough to say whether possibly on the 14c rim, that tire might end up even be higher than on a 19c rim. The chart above is showing inflation sizes when on rims larger than ETRTO would have recommended back then.
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Perplexing to me anyhow because I thought when I squeeze something like a tire it goes narrower and protrudes and when I relieve that pressure it goes wider and shallower.
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A 35mm tire on a 19c rim is probably closer to being standard per ETRTO standards and would be likely closer to nominal sizing than on a 14c rim. That said, I don't know enough to say whether possibly on the 14c rim, that tire might end up even be higher than on a 19c rim. The chart above is showing inflation sizes when on rims larger than ETRTO would have recommended back then.
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^This. Fender fitting is custom for pretty much every installation for best results. Just be sure to make/leave rounded corners on the slots so that a crack does not start there. I do this by punching holes with a Roper-Whitney punch clone at the end/corners of the planned slots and cutting between them. https://www.amazon.com/dp/B0002T87CW
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Is it me or the chart actually shows that with the same nominal tire witdh at same pressure ... the height is the same whilst the width increases stepping up the rim sizing only?
Perplexing to me anyhow because I thought when I squeeze something like a tire it goes narrower and protrudes and when I relieve that pressure it goes wider and shallower.
Perplexing to me anyhow because I thought when I squeeze something like a tire it goes narrower and protrudes and when I relieve that pressure it goes wider and shallower.
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I wonder how representative it is what one would typically do with wider tires. I mean ... I am talking 35 on 21 vs on 14 whereas these tests are for combo where rim with is almost as wide as tire. I also can’t see having 100 PSI in a 35mm tire so it would be less of a balloon effect.
Interesting anyhow, just inconclusive I guess for my case still ...
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1) I basically don’t care about how long it is around the cross section but how much of that extra protrudes which way.
2) One might argue it would protrude equally each direction but into the rim bed, however that’s not how tires behave, their walls are thicker on the contact patch and thinner on the sidewalls.
3) I don’t think adding 2-4mm to the rim width is same “extra circumference” effect as would be adding 25PSI, it’s not as even. All else equal, if you pinch a tire at the beads it would like to go narrower and gain more height for instance.
I am not arguing about the answer which I seek here but I can’t accept tires cross section behaving like perfect geometric shape of a circle.
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If you're moving to wider rims but are concerned about having enough clearance at the tire tread, I'd probably size down the tires by one step.
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The graphic has me puzzled - it appears that the tire casing increases as the rim width increases. For example, look at two of the curves for 25mm GP4000 – the “100psi on Ardennes” (light blue curve), and “100psi on 19mm” (white curve). The blue curve totally encompasses the white curve. So the increase in rim width appears to expand both the tire’s height and width … in other words, the tire casing itself appears to expand. Magic?
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It is hard to grasp, isn't it? I don't know if it's geometry, trig or some other such but it's beyond me as well. Maybe someone who understands these things can explain it.
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The graphic has me puzzled - it appears that the tire casing increases as the rim width increases. For example, look at two of the curves for 25mm GP4000 – the “100psi on Ardennes” (light blue curve), and “100psi on 19mm” (white curve). The blue curve totally encompasses the white curve. So the increase in rim width appears to expand both the tire’s height and width … in other words, the tire casing itself appears to expand. Magic?