drewfio

I was curious your thoughts about how the same size tire on different width rims would affect ride feel.

For example, I have some Pasela tires and some Continental 4 seasons, and got new wider wheels recently. The same exact tires measure around 2-3mm wider (depending on the tire) when moved to the wider rim. Would you expect the same ride feel, or would you need to upsize on the narrower rim to get the same actual width, to get a similar ride feel? On one hand I would imagine the same tire would have same volume, and would potentially have the same cushiness, but on the other hand, the contact patch with the road is different, wider and shorter on the wider rim. Hopefully this makes sense.

I'm posting this here since I've found the C&V crowd very knowledgable, but feel free to move to a more appropriate place if you think it belongs elsewhere. Thanks!

randyjawa 

In days gone bye, I ran 700c x 25 on the rear and 700c x 23 on the front. Later on I learned to appreciate 700c x 28 front and back. These days, I prefer to run 700c x 32 front and back. How does this seem to impact performance?

700c x 25(rear) and 700c x 23 front = (comparatively speaking) fast and harsh

700c x 28 front and back = not quite as fast and less harsh = more comfort and more fewer flats

700c x 32 front and back = darn near perfect in the comfort/dependable sense and I could (at my age) care less how fast I go these days and have never had a flat(so far)

The above is based on experience.

SpedFast

I started with 25s on narrow rims and they measured 25mm. I got some new rims that were a tinch wider (not intentionally-just a good deal) and decided I had clearance on the frame to go up to 28s. They measured 32mm on the wider rims and the ride was smooooooooth. But the clearances on the frame were marginal so I put the 28s on the narrower rims and they measured 29mm and the ride was a tad firmer, yet they were the same tires. So from experience I have found a wider rim equates to a smoother ride all other factors being equal. Caveat=different tires might respond differently depending on sidewall construction. These tires were foldable. Wire bead might be different.

shoota 

Having done this many times I would put money down that in a blind test the vast majority of people wouldn't be able to tell the difference in 2-3mm difference on the same tire, all other variables remaining the same. The biggest difference is tire pressure. And no, "expanding" a tire with a wider rim doesn't add air volume.

bamboobike4

Kind of my experience, too.

When the extremes are there, i.e. a 700x18 Panaracer Technova vs. a Veloflex Master 700x25, sure.
But otherwise, I don't really notice. The only time I start to try and "feel" a tire is when I think I have a flat.

I have a set of Challenge Strada 700x28's that are supposed to have mediocre rolling resistance.
I can barely tell when my brakes are rubbing, much less discern rolling resistance.
Every time I climb, though, I swear my tires are low and my brakes are rubbing.

When I look down at a fat tire, I automatically feel more tired.

drewfio

This is getting at what I wanted to know. What about the reverse? I'd guess you feel the same. But if you took a claimed 28mm tire that was 28mm on one rim, and moved it to a narrower rim, you could expect the same level of cushiness, even if it measured closer to 25mm on that rim, since the air volume should be the same?

shoota 

That's been my experience. The tire will be more "bulbous" on a narrower rim, which doesn't seem to affect cushiness too much. I think I can notice cornering characteristics though, the bulbous tire feel less planted to me.

Classtime 

I guess it is too cold/snowy to feel for yourself?
GP4000 25s are more plush on TB-14s than on Open-Pros for me.

Dfrost 

Gotta disagree on the air volume statement. The wider rim is essentially creating a slightly larger circumference in the tire section, so the internal volume for the same tire is greater by 5-10% depending on the difference in actual internal tire widths. (Section area = Pi X tire section radius squared.) I will fully agree that most if not all of us wouldn’t notice the difference.

Andy_K 

I'm with @Dfrost on this, on both points. I guess our inner math nerds are coming out. The cross section of the tire is effectively a circle with a piece cut out at the bottom and a box tacked on. The partial circle circumference provided by the tire is constant, but with the wider rim it's part of a larger circle. Depending on the cross section of the rim, the size of the box at the bottom is also likely bigger.

On the less nerdy and more practical side, what really makes a difference is the tire pressure and suppleness. It's possible that changing to a wider rim would let you run at a lower pressure without pinch flatting, but most people aren't pushing that limit. It also possible that changing the rim might change which part of the casing flexes, this changing the suppleness, but that seems unlikely.

The biggest issue is probably handling. A wider tire on a narrow rim can roll a bit (laterally) under hard cornering, making it feel a bit squirrelly. I think that takes a big mismatch though. I've felt it with 700x35 cyclocross tires on a narrow rim at low pressure (~30 psi). I can't say I've noticed it with a road tire.

masi61

If you are wanting to teach yourself about ride feel with different width rims, I would think you don't want dull, heavy commuter tires to palpate the changes. You should strongly consider latex tubes and open tubular clinchers then play around with different tire widths and pressures.

rm -rf

I agree that a wider rim would increase the air volume. The beads are farther apart.

Since a circle's area is proportional to the square of the diameter of the circle, a small change in diameter makes a significant difference in area. Area=Pi * radius squared, or 1/2*Pi*diameter squared. So air volume goes up by the square of the difference. 29mm diameter vs 27mm is 15% more volume. So, in theory, I can lower air pressure that much.

I notice more comfort with the lower pressure, wider tires, rather than an obvious better cornering. But the extreme case was riding 38mm lightweight road tires vs 25mm. The 38s felt extremely secure while cornering, "on rails".

shoota 

How do you account for the tire’s loss in height as the width expands?

SurferRosa

I prefer lighter, skinnier rims on my road bikes.

Andy_K 

I'm sorry I don't do accounting. My training is as a software engineer.

But seriously, I've never examined it closely to see which one has a more circular cross section. I could be wrong in what I said previously, but I'm sticking with it.

HTupolev

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