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Is there such a thing as too wide a rim?

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Is there such a thing as too wide a rim?

Old 05-12-17, 02:11 PM
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Is there such a thing as too wide a rim?

The 2017 Roval Control SL wheel have rims with an inside width of 25mm. When we're talking about 35mm tires, is this even better than the typically 21-23mm? What is too wide?
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Old 05-12-17, 03:27 PM
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Depends on usage, intended bike its supposed to go in.
Rim only, you can always find a usage and a bike it'd make sense in.
But I'm assuming there are some frames/forks which can't take the (smallest) width tire that'd make sense on a certain rim. Or maybe even where the rim itself is too wide.
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Old 05-12-17, 03:56 PM
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My rims are 25 mm internal and I put 28s on them (which stretch out to 32 mm).
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Old 05-12-17, 04:09 PM
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Originally Posted by Seattle Forrest
My rims are 25 mm internal and I put 28s on them (which stretch out to 32 mm).
Excellent reference point, thanks.
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Old 05-12-17, 04:27 PM
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There's plenty of latitude relating to rim and nominal tire width, however there are considerations.

Ideally, a tire should assume an Omega shaped cross section, so the dominant interior profile is roughly circular. This ensures evenly distributed (hoop) tension across the section. If the rim is too wide, the tire is more like an inverted U, so the stress is uneven, and the tire is fighting within itself to assume the more natural circular profile. This isn't necessarily harmful or problematic, but it may cause a harsher ride.

At the other extreme, a wide tire on an overly narrow rim, doesn't resist side forces well, especially if the pressure is low. This can cause wallowing or control problems when turning.

However, as I intitially said, there's plenty of latitude, even beyond what tire width charts like this one recommend.

Here's more on the subject for those interested.
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Old 05-12-17, 04:50 PM
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Seems there's a trend for wider rims. Less difference between rim/tire width means more aero.

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Old 05-12-17, 04:54 PM
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Originally Posted by tyrion
Seems there's a trend for wider rims. Less difference between rim/tire width means more aero.
Yes, this is the bike world, and there's always a trend moving from center in one direction or the other. this is true, not only of rims and tires but just about everything bicycle related.

This is why I prefer to post information about the effects of changing from the norm, and let people decide for themselves. In any case, all trends away from long held practices, must be considered in the light of the history of trendiness.
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Old 05-12-17, 06:04 PM
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Originally Posted by FBinNY
There's plenty of latitude relating to rim and nominal tire width, however there are considerations.

Ideally, a tire should assume an Omega shaped cross section, so the dominant interior profile is roughly circular. This ensures evenly distributed (hoop) tension across the section. If the rim is too wide, the tire is more like an inverted U, so the stress is uneven, and the tire is fighting within itself to assume the more natural circular profile. This isn't necessarily harmful or problematic, but it may cause a harsher ride.

At the other extreme, a wide tire on an overly narrow rim, doesn't resist side forces well, especially if the pressure is low. This can cause wallowing or control problems when turning.

However, as I intitially said, there's plenty of latitude, even beyond what tire width charts like this one recommend.

Here's more on the subject for those interested.
I take it then that these guidelines are evolving as well? Below is in the description from Enve's website regarding Seattle Forest's 4.5 AR Disc wheels. Based on the charts online 19-20mm is about the widest recommended inner width for 30mm tires but Enve obviously feels otherwise (28-30mm is probably where you get the maximum aero benefit). Similarly, Roval says their CLX 32mm wheels with 21mm inner width were designed around 26mm tires (with aero in mind).


"The SES 4.5 AR Disc is an uncompromising aero wheel designed specifically for disc brake equipped bikes and large volume 28 to 30mm road tires."



Last edited by vinuneuro; 05-12-17 at 06:12 PM.
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Old 05-12-17, 06:17 PM
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There are multiple factors involved with every decision like this.

In the case of tire width ratios, there are weight, aero, rolling drag, comfort, structural strain on the tire, and so on.

So, the trends may reflect changing priorities, or simply that trends tend to feed on themselves, until they reach a point where oter problems become more significant, then the pendulum swings back.

Not that long ago, the "wisdom was that narrower tires were faster, and trend went from 25mm tires for road racing all the way down to 18, before moving back to 25 then to 28 or more.

We see this pattern in all sorts of things, running from diet to how to raise children. part of the reason is that the need for reportable news, where saying things are makes sense will never cut the mustard.

I find it all intersting since I've been doing roughly the same things for 50 years. Sometimes my tires are too wide, others, too narrow, and roughly every 10-20 years I'm "trendy".

But, as I posted initially There's plenty of latitude, so feel free to experiment, and make an adjustment if you feel you're starting to notice issues relating to being too far to one side or the other.
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Old 05-12-17, 06:29 PM
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Originally Posted by FBinNY
There are multiple factors involved with every decision like this.

In the case of tire width ratios, there are weight, aero, rolling drag, comfort, structural strain on the tire, and so on.

So, the trends may reflect changing priorities, or simply that trends tend to feed on themselves, until they reach a point where oter problems become more significant, then the pendulum swings back.

Not that long ago, the "wisdom was that narrower tires were faster, and trend went from 25mm tires for road racing all the way down to 18, before moving back to 25 then to 28 or more.

We see this pattern in all sorts of things, running from diet to how to raise children. part of the reason is that the need for reportable news, where saying things are makes sense will never cut the mustard.

I find it all intersting since I've been doing roughly the same things for 50 years. Sometimes my tires are too wide, others, too narrow, and roughly every 10-20 years I'm "trendy".

But, as I posted initially There's plenty of latitude, so feel free to experiment, and make an adjustment if you feel you're starting to notice issues relating to being too far to one side or the other.
I hear ya. For gravel riding I'd like to max out the tire size my frame will allow 35-38mm. Harder to experiment with wheels than the other way around.
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Old 05-12-17, 06:40 PM
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Originally Posted by FBinNY
Yes, this is the bike world, and there's always a trend moving from center in one direction or the other. this is true, not only of rims and tires but just about everything bicycle related.

This is why I prefer to post information about the effects of changing from the norm, and let people decide for themselves. In any case, all trends away from long held practices, must be considered in the light of the history of trendiness.
Like say the history of 700A, 700B, 700C, and 700D.
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