Why no alloy rim brake rim over 25mm wide?

[cyan]

Just curious, given all the "wider rim wider tire" trend on road bikes (esp. noticeable with carbon wheels), why alloy rim brake rims (clincher or tubular) still stay under 25mm for external width (in fact, most are still <=23mm)? Is it a manufacturing or cost issue? Or the brands have decided to leave alloy rim brake behind because of disc?

Take HED belgium plus for example, with a 21mm internal width and 25mm external width, a 25mm tires (GP 5000) will inflate to almost 28mm wide at ~80 psi, not a nice shape in terms of aerodynamics or cornering stability. If most people have moved to 25mm or wider tires, why not evolve accordingly with a wider rim?

[jtbadge]

The 23-25mm rim width seems to be the sweet spot between giving tires a wider profile while also fitting in most frames/forks with correct clearance and proper brake alignment/leverage.

[fa63]

HED Belgium Plus Eroica is 25 mm internal / 30 mm external width.

[jtbadge]

HED Belgium Plus Eroica is 25 mm internal / 30 mm external width.

Not made for rim brakes, though.

[CMiller]

I wonder if it might be related to extra weight? As tiny of an amount as it would be.

The brake leverage point is interesting, probably a bigger concern with caliper brakes as compared to v-brakes.

[cyan]

The potential brake clearance/leverage issues also apply to carbon wheels, but there are many rim brake options with 26-28mm external width.

[fa63]

Not made for rim brakes, though.

Oh, I thought it was made for both disc and rim brakes. Thanks for the clarification!

[smead]

Simple - carbon rims are the trendy must have go fast thing, same deal with crazy wide road tires. :banana:

[robt57]

Isn't/wasn't the plan/idea that the rim/tire combo was more aero?

23/23, 25/25 and like that..

[JAGI410]

Velo Orange Voyager is rim brake, tubeless compatible, and 27mm external/22.1 internal.

For more performance/lighter rim, the Velocity Quill is 24.5 mm external/21mm internal. Also rim brake/tubeless.

Velocity Cliffhanger is 30mm external/25mm internal.

[ColonelJLloyd]

proper brake alignment/leverage.

This.

The brake leverage point is interesting, probably a bigger concern with caliper brakes as compared to v-brakes.

Likely to be worse with cantilevers and linear pull brakes, I'd think. Pads like Kool Stop Thinlines would help mitigate it, but on most frames and forks rims wider than 25mm are going to be an issue.

[bikinchris]

Because the space between the rim and the fork or stay wouldn't be enough to let the wheel turn for most bikes.

[davidb]

Or, because the market for rims/wheels is driving to disc brake only rims.

[jtbadge]

Likely to be worse with cantilevers and linear pull brakes, I'd think. Pads like Kool Stop Thinlines would help mitigate it, but on most frames and forks rims wider than 25mm are going to be an issue.


Agreed, setting up 25mm Belgium Plus with mini-Vs was much more finicky than narrower 23mm Archetypes or R460s. Less margin for adjustment.

[ultraman6970]

The people that published stuff like that did a lot of tests but at the same time you have to take it with a grain of salt because they found a way to defy the laws of physics :) Specially the ones related to FRICTION with the pavement and the wind :D Honestly I was hoping a few years back when all that stuff about wider and wider came out that the same guys were going to say that they found a way for us to have warp capabilities.


Isn't/wasn't the plan/idea that the rim/tire combo was more aero?

23/23, 25/25 and like that..

[nachetetm]

Because the aero in wheels under 40mm depth is pretty much irrelevant, and more depth with an alu rim would be too heavy.

[AngryScientist]

The 23-25mm rim width seems to be the sweet spot between giving tires a wider profile while also fitting in most frames/forks with correct clearance and proper brake alignment/leverage.

yes, this. i have some wider carbon wheels and they just dont work as well with rim brakes. 25 is the comfortable limit i would say.

i'm all rim brake all the time, and my "sweet spot" is 24/25mm at the brake track for the gravel bike and 23/24 for road application.

The Velocity Quill and Easton EC90SL are almost the same width @ 24mm external and are excellent and as about as wide as i want.

[cyan]

yes, this. i have some wider carbon wheels and they just dont work as well with rim brakes. 25 is the comfortable limit i would say.

Is this still a problem for brake calipers like DA9100 which officially support 28mm rims?

[thirdgenbird]

Is this still a problem for brake calipers like DA9100 which officially support 28mm rims?

Rims or tires? The only claim I see is clearance for 28mm tires.

Edit: never mind. It does say 28mm rim. They only claim tire specs in the main marketing information. I had to dig a bit further.

[robertbb]

yes, this. i have some wider carbon wheels and they just dont work as well with rim brakes. 25 is the comfortable limit i would say.

i'm all rim brake all the time, and my "sweet spot" is 24/25mm at the brake track for the gravel bike and 23/24 for road application.

The Velocity Quill and Easton EC90SL are almost the same width @ 24mm external and are excellent and as about as wide as i want.

Do you mean the Easton R90SL?

[cmbicycles]

If wider rims are more aero, doesnt the same principle apply to the rider getting wider? More desert for me please ;)

[prototoast]

A lot of it is wall thickness. A HED Belgium Plus is 25mm external, 21 internal. A Zipp 303 Firecrest is 26.4 external, 17 internal. Enve 4.5 SES is 27 external, 18.5 internal (front). A lot of the "wide" carbon rims aren't so wide on the inside. Aluminum is 50% denser than carbon fiber, and would be very heavy if made with such thick walls.

If there were an aluminum rim with a 27 outer, 23 inner (Hed Belgium++), you probably wouldn't want to run anything narrower than a 28 tire, which would likely measure at 30+ width, and you're still outpacing your rim in terms of "optimal" aerodynamic shape.

[dmurphey]

Simple - carbon rims are the trendy must have go fast thing, same deal with crazy wide road tires. :banana:

Try it, you might like it.