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wider inner rim width .. same tire width

1103 Views 51 Replies 9 Participants Last post by Lombard, 41 m ago

zero7404

Discussion Starter · 10 d ago (Edited)

is there any info out there that tests pinch protection vs inner rim/tire width ratios ?

edit: any testing or folks with some experience on that …

initial thought is that there’s some ratio or range that still works well for pinch protection, when a wheel inner width is wide and the tire is ‘narrow’ compared to it …

examples:

1.12 ratio - a 28mm tire on a 25mm inner width

1.33 ratio - a 28mm tire on a 21mm inner width

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Lombard

· #2 · 10 d ago

Not that I know of. A wider rim makes the tire effectively wider, so you would have a slightly smaller chance of pinch flatting.....in theory.

That being said, a wider rim exposes more of the tire sidewall to objects below, so you would have a slightly greater chance of getting a sidewall puncture.......in theory.

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cxwrench

· #3 · 10 d ago

Zipp for example has a range of tire widths ranging from 25-35mm for certain wheels. They don't say anything about which might work better or not, just what will fit on the rims. I'm guessing that 'better' is subjective enough and depends on riding style and terrain to the point that it would be really hard to quantify.

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Lombard

· #4 · 10 d ago

zero7404 said:
1.12 ratio - a 28mm tire on a 25mm inner width

1.33 ratio - a 28mm tire on a 21mm inner width

Now that you added this, I will give you my take.

If it were me, I would go with the 21mm rim. IMO, we have gone too far in the other direction. We used to run road tires with 14 and 15mm rims which was narrow for sure. I was glad to see wider rims in the range of 17 to 21mm. 25mm is ridiculous for a 28mm tire and just asking for a sidewall cut.

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zero7404

Discussion Starter · #5 · 9 d ago

yes, the ratio of 28-25 would be almost 1:1 which is not ideal for the natural curvature of the tread in contact with the road.

but i can see 32 or 35 on a 25mm wide rim

duriel

· #6 · 9 d ago (Edited)

zero7404 said:
yes, the ratio of 28-25 would be almost 1:1 which is not ideal

What are you basing this on?
What is the ratio for a motoGP tire/rim?
edit: ignore that fh, he is a troll that follows everyone around, he don't know shiet. Where is the info?

Lombard

· #7 · 9 d ago

duriel said:
What are you basing this on?
What is the ratio for a motoGP tire/rim?

Apples to cheesesteaks comparison.

Lombard

· #8 · 9 d ago

zero7404 said:
yes, the ratio of 28-25 would be almost 1:1 which is not ideal for the natural curvature of the tread in contact with the road.

but i can see 32 or 35 on a 25mm wide rim

35mm tires on a 25mm rim, maybe. I'm running my 42mm gravel tires on 21mm rims.

Heck, we used to have mountain bike tires that were 53mm on 17mm rims. We have gone full extreme from ridiculously narrow rims to ridiculously wide rims. Where does it end?

zero7404

Discussion Starter · #9 · 9 d ago

there is some minimum ratio that’s tolerable on road .. maybe 1.3 - 2.0 or something like that

the general benefit to wider rim is a more even contact patch and more consistent tire deflection in cornering.

in a cornering maneuver, a light bulb shaped tire on a rim will deform in a way that more of the tire winds up on the opposite side of the road surface

there’s a graphic in the middle of this article that shows this effect, although it shows the deformation correctly, the road surface curves in the picture are not really realistic

www.bikeradar.com

Rim width explained for road bikes, mountain bikes and gravel bikes

What is wheel rim width and why is it important?

www.bikeradar.com

zero7404

Discussion Starter · #10 · 9 d ago

when the wheel axis is parallel with the road, a=b
otherwise, a is larger than b

for those who run very low pressures, the deformation shown in the picture becomes more pronounced than what you see

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duriel

· #11 · 9 d ago

That is an interesting article. For me, I like to run wider rims making the same assumption as the article that your cornering power & control are greater. I tend to lean that way cause wider tires have more tread on the ground, ergo more traction.
I really don't see any relationship rim/tire effecting the pinch flat situation. The tire once compressed all the way to the rim in a pinch flat situation, the tire is always going to be wider than the rim unless you are running a very vertically short tire.
IMO, pinch flats are more related to PSI in the tire, if you have sharp edges/pot holes, you will want to run higher pressures to limit the total collapse of the tire to the rim. Granted with a wider rim one will probably be running less PSI cause it is more comfortable, but I don't think running a wide rim will necessitate running low pressures, you could run higher pressures with a wide rim.
When I used to do a certain training ride where we were in a peleton, I always would run 10PSI higher pressure, cause I knew if there was a pothole, I was going to have to take the hit rather than crash into the bike beside me.

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zero7404

Discussion Starter · #12 · 9 d ago

taking a hit on cracked road surfaces is one reason why i prefer running 10-15 psi above what silca recommends

my tire spec says 45 - 95 psi, i run just a few psi higher than the middle of the spec.

with the tpu tubes, some additional confidence in not flatting due to a puncture that would compromise butyl .. and that allows me to keep on at the pressure i chose, or tone it down a little depending on road conditions and weather.

choosing a wider rim for my spare set by a few mm with the same tire, i think may improve my traction when the bike is tilted at some speed such as with turning at an intersection.

and the tire itself has proven to be pretty tough for me, save for one odd-ball instance when it punctured just off to the side where the tread thickness begins to narrow … but the shoe goo is holding well in that small spot.

craiger_ny

· #13 · 9 d ago

I had a lone tire from having a bike that I didn't have any more that I figured I'd burn thru. So I put it on the back with a 25 or nearly 25 inside dim rim, the tire was a 25. I immediately noticed it looked ridiculous but like I said, I figured I'd run it through its course and be done with it. It showed significant sidewall abrasion very early on.

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Lombard

· #14 · 9 d ago

craiger_ny said:
I had a lone tire from having a bike that I didn't have any more that I figured I'd burn thru. So I put it on the back with a 25 or nearly 25 inside dim rim, the tire was a 25. I immediately noticed it looked ridiculous but like I said, I figured I'd run it through its course and be done with it. It showed significant sidewall abrasion very early on.

At the end of the day, you don't want a light bulb, but you don't want a bell either.

Moderation.

zero7404

Discussion Starter · #15 · 9 d ago

craiger_ny said:
I had a lone tire from having a bike that I didn't have any more that I figured I'd burn thru. So I put it on the back with a 25 or nearly 25 inside dim rim, the tire was a 25. I immediately noticed it looked ridiculous but like I said, I figured I'd run it through its course and be done with it. It showed significant sidewall abrasion very early on.

the outside of your rim would be wider than the tire ...

did it look like this ? .. or maybe close enough

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craiger_ny

· #16 · 9 d ago

zero7404 said:
the outside of your rim would be wider than the tire ...

did it look like this ? .. or maybe close enough

View attachment 488691

No, it was more of a dome like shape that filled out. That is exaggerated and nothing like I experienced. That is a car.

zero7404

Discussion Starter · #17 · 9 d ago

i realize it's a car ... that's the closest thing i could think of to show you for what i visualized as a wider rim and narrower tire. the picture, sadly, depicts something mechanically unintended, dangerous, and plain stupid ...

but the people that do that with their cars must think it's the the cat's meow or something like that.

Lombard

· #18 · 8 d ago

2

zero7404 said:
i realize it's a car ... that's the closest thing i could think of to show you for what i visualized as a wider rim and narrower tire. the picture, sadly, depicts something mechanically unintended, dangerous, and plain stupid ...

but the people that do that with their cars must think it's the the cat's meow or something like that.

People do a lot of stupid things with cars:

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zero7404

Discussion Starter · #19 · 8 d ago

the $$$ spent making those Frankenstein creations could have bought them what they really wanted in the first place …

cxwrench

· #20 · 8 d ago

I don't think you understand. That IS what they wanted in the first place.

Reactions: 2

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