this brings back memories. Pythons were big around early 2000s. Now, this tire shares only the name but still.
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That’s not really why they do that.
Thinner ID gives the tire a more rounded shape and allows them to corner better. DH teams run a ton of sealant and roof tar inside their tires to prevent flats. Also a ton of PSI.
It’s really apples to oranges so it’s not really relevant to this discussion IMO.
Actually, it is relevant. By increasing the effective tread width, you’re shortening the sidewalls, which decreases “travel” of the tire.
Pressure and Volume does play a role, but the diagram you’re showing isn’t to scale and ignores that as you go from 22.5 → 40mm, the mounted tire is getting shorter (assuming using the same tire)
And actually, now that I think about it, compressing the tire could have the same effect to the point where going wider “could” make the tire taller too ( I think) - depends on the tire.
DH racers run 24-27 PSI so they have enough support to run those narrower rims without getting super floppy.
Yes, you are correct they are taller with 25mm ID but that’s also a helpful trait for DH racers who lean their bikes much further than XC racers tend to at much higher speed.
More power to people who can ride these types of tires with low 20’s/high teens PSI and 25mm ID. Not for me personally, hate the squirrely feeling.
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Actually, if you ignore the labeled widths, the image is very close to scale and does a great job of illustrating the point of increasing volume as you increase rim width. In the image, the tire portion is the same for all 3 cases (you can measure the inside perimeter of the tire only and they’re within 1% of each other) and you can clearly see (and measure) that the cross sectional area (and therefore volume) grows as the rim width increases. I’m also not sure the sidewall height actually decreases all that much as the rim width increases. I understand your theory that as the tread spreads out it’s no longer contributing to sidewall height, however you’re also moving the bead outwards which allows for more of the sidewall to contribute to height and not ballooning out to the proper tire width (i.e. the sidewall gets “steeper” as viewed in a cross section). This is also illustrated pretty well in the images above.
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You’re incorrect in assuming that the tread must get closer to the rim when increasing rim width. If you had a 1.5” rim with a 2” tire, then you are correct, wider shortens the tread height and reduces volume. But imagine the opposite. Take a 2” tire and mount it to a 10mm rim. It would almost be a complete circle. Now make that rim 0mm wide. The tire beads have to move in and touch, which makes the tread lower and decreases the volume. So clearly there’s a rim to tire ratio where the behavior reverses.
In the range we’re talking about (20-35 mm rim with 2”+ tire) increasing rim width has very little effect on tread height. This is because the tire sidewall is not vertical, it’s angled out. (See the red triangles below). So some of the sidewall is reaching horizontally and some is reaching vertically. As the rim width increases, the tire sidewall has less horizontal distance to reach, so the tread might move upwards. Then again, the tread can also get flatter. There’s no easy math to say which it will do (plus tread design and tire construction probably have a significant effect).
The below graphic can be representative of this situation. The tread height (distance from the rim) doesn’t have to change any significant distance with a realistic range of rim widths.
Now I hope that you can see that, given a tire width and a realistic range of rim widths for that tire, a wider rim is unquestionably going to increase the air volume contained by the tire and rim (assuming no inserts are used). What is uncertain is how much it affects the tread shape and ride characteristics for knobby tires.
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No, you’re right, I posted this elsewhere too after thinking about it, sidewall height can actually go both ways depending on the combo but should change and shouldn’t be viewed as constant. I have seen fork clearance increase though with a rim width that went up (gravel fork 25-30 mm rim and gravel tires) - so I suspect tire design and casing plays a role too.
I’m going to measure some specific tires I have, I think at the end of the they day with the small changes we’re talking about, we’re mostly splitting hairs on the differences. I’m not sure most would even be able to tell the difference.
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Looking at some new tires. I was thinking either Vittoria Barzo F/Mezcal R. Or Schwalbe Racing Ray F/Thunderburt R. Would there be a lot different in these sets? Or mostly just brand preference?
Your Vittoria equivalent would be a Ralph not a TB. TB is more like a peyote.
But realistically all of these tyres are much of a muchness.
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My very first set of tubeless tires where hutchinson pythons size 26 on mavic rims. Yeah, I am old and so is this model of hutchinsons. Off course it has evolved a lot, but just saying.
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I was on Mezcal/Mezcal for 5 years. This year I went to Ray/Ralph. I’m never going back. They feel just as fast and I have more grip. I tried Barzo as a front for a few rides years ago and didn’t like it, but I don’t remember why.
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With the arrival of the wet autumn weather I removed the Aspens after a few crashes and went back to a new set of Racing Ray/Ralph 2.35. The bike feels (emphasis on “feels”, I can’t measure this) faster to accelerate, but much more nervous over any irregularities, even at very low pressures and much less comfortable. But on wet conditions, specially if any clay is involved, things are much safer with the Racing Ray up front. Although, in proper deep mud they’re no better than the Aspens and the Aspens were packing much less with mud.
I really wish Schwalbe would do a proper 2.4 or 2.5 version of the Ray/Ralph, it seems to me that pure volume is what makes the 2.4 Aspen an exceptional dry conditions tire
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Does the Aspen actually measure 2.4"? Both tires are mounted on 28mm internal width rims inflated to 30 PSI
Maxxis Rekon 29x2.4"
And the Schwalbe Racing Ralph 29x2.35 that replaced it
When would you choose a narrow tire over a wider tire?
Mud? Sand? Deep leaf litter?
I don’t think I would.
Like a 2.35 over a 2.4 or a 2.25 Conti for example? Or same tire just different sizing? If I want the Ray/Ralph combo and I know they only come in 2.35, I’m not going to pass on them because Aspens are 2.4s. Now if the Ray/Ralph combo was 2.25 and there’s a 2.35, I wouldn’t even think of the 2.25 regardless of the conditions.
My Aspens measured precisely 2.5 on 30mm rims (63.5mm).
My Ray/Ralph, Super Race, measure 57mm on the same wheels, so 2.25
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My totally non scientific assessment is that the Ray works better on wet, greasy over hard conditions than the Aspen purely because it has proper lugs. I find the Aspens to be murderous in those conditions, to the point of sliding around even going on a straight line.
On actual deep mud I find the Ray no better than the Aspens, maybe even marginally worse
I tried running the Ray/Ralph combo, just couldn’t get used to the grip. I’m running Wicked Will f/r now, but they are wearing pretty fast.
Thinking of switching to something else on my next purchase.
Maybe Kendas?
When the narrower tyre gives you a faster ride because it is just a better tyre than the competition (eg raceking), or when you need clearance for mud.
Sadly not looking good for the Kenda Booster SCT at BRR, 12 votes out and will drop off after this month.
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