Advice on rim width for a disc build.

[Mr.Gib]

I'm building up a new disc bike and it's wheel selection time. I am pretty certain for this bike I want to run 28mm tires so 30mm rim width is the logical choice. My ideal depth is 40 - 45mm, but I can't seem to find that depth in 30mm width.
Farsports has 50mm depth at 30mm width (FS50/30G). And Light Bicycle has the Falcon Pro WR38, but that is 32mm wide. Their popular AR56 is just too deep for this build. My resistance to deeper wheels is for aesthetics, not handling issues. The frame is not an aero bike - more of a climber. An AR46 that was 30mm wide would be perfect but alas that depth is 28mm wide.

I guess the question is how are people finding the 32mm wide rim for serious road riding? 25mm internal is getting up there. Or is the smarter move to stick with the various 28mm wide rims and ride 25mm tires for a faster and lighter setup? Other suggestions?


I'm 170lb (76kg), no more racing, but I do a lot of miles and push it pretty hard in the corners, descending, etc. Roads here are decent but some pebbly chip seal also.

[alcatraz]

The difference in aero between an AR56 and WR38 is not going to be small.

If looks trump aero then WR38 does seem to be the better choice. Who knows, you might even put a 32C tire on one day. A conti 28c is going to become ~30mm on that rim. If you're riding offroad then a wider tire like a 32C will better protect the rim.

My 95kg friend reluctantly went to 35C for a 4000k tour he did, and now that he's back he doesn't want to go back to his older 25/28c bike.

[Aeo]

https://www.nextie.com/2020-all-road-31mm
https://www.nextie.com/gravel-GX-700C

[alcatraz]

Great looking rims.

[Mr.Gib]

No doubt big tires are an advantage in everyway but speed and weight. Desire for a bit of aero is why I like the idea of a 45mm deep rim. I think it's a good comprimise. I'm a committed Vittoria Corsa fan, so I'll be using their 28mm which is pretty fat. I suspect it will be at least 30mm wide on any internal width over 22mm.

[frnchy]

I adore my WR50 wheels; the extra width is beneficial to comfort and cornering IMO. No aero concerns whatsoever using a 28 mm Corsa Control, which comes to about 31-32 mm on the 25 mm inner width. I will personally never go back to anything narrower. Whatever aero microwatts I lose with a 2 mm wider rim, I gain many multiples of in ride comfort and traction. I highly recommend using the widest rim you can reasonably fit in your frame.

[Mr.Gib]

What do you guys think about going with all Sapim Sprint instead of the usual CX ray? Maybe with flyweight rims.

[Hexsense]

Sprint drive side and Ray NDS on rear wheel and reverse on front wheel (sprint disc side, ray non-disc side) make a wheelset with more balanced tension.
That should make a stiffer wheelset than all cx-sprint.

[alcatraz]

It's not about tension exactly. CX-ray can withstand 300kgf before breaking, similarly to cx sprint.

The spoke angle on the rear ds is less advantageous and it helps to pick a spoke that doesn't stretch as much. X mm stretch on the DS spokes will allow for a greater rim deflection, than X mm stretch on the NDS side will.

On a front disc brake hub the wheel is indeed dished aswell but not significantly. Sure it depends on the geometry but if the tension is any indication of spoke angle (which it is to a big extent), then the rear will have a much greater difference between the flanges than the front. The rear can differ 50-60kgf between flanges and the front merely 10kgf.

So if you want low rim deflection you pick a spoke that doesn't stretch as much, (or if dished = an asymmetric rim). A 5gr spoke will stretch less than a 4gr and so on. But the DS side is the lower hanging fruit if one wants to get the least amount of deflection for the weight added.

Still picking a good hub will help much more than obsessing about spokes. The priority should be the hub first. A good hub with cx-rays can outperform an average hub with cx-sprints. If you use all the tricks in the book, it adds up. Good hub, asymmetric rim, a size larger spoke on DS, internal nippes etc.

[wheelsONfire]

I'm building up a new disc bike and it's wheel selection time. I am pretty certain for this bike I want to run 28mm tires so 30mm rim width is the logical choice. My ideal depth is 40 - 45mm, but I can't seem to find that depth in 30mm width.
Farsports has 50mm depth at 30mm width (FS50/30G). And Light Bicycle has the Falcon Pro WR38, but that is 32mm wide. Their popular AR56 is just too deep for this build. My resistance to deeper wheels is for aesthetics, not handling issues. The frame is not an aero bike - more of a climber. An AR46 that was 30mm wide would be perfect but alas that depth is 28mm wide.

I guess the question is how are people finding the 32mm wide rim for serious road riding? 25mm internal is getting up there. Or is the smarter move to stick with the various 28mm wide rims and ride 25mm tires for a faster and lighter setup? Other suggestions?


I'm 170lb (76kg), no more racing, but I do a lot of miles and push it pretty hard in the corners, descending, etc. Roads here are decent but some pebbly chip seal also.

You should have had the phantom rim test protocol from Easton, 28mm wide rims. All tires over 22mm did offset aero. If a tire as wide as rim or even wider were used, the rims were no more than dead weight you carried around. So, perhaps you should contemplate something like 30-35mm deep rims with 30mm tires?

[Mr.Gib]

It's not about tension exactly. CX-ray can withstand 300kgf before breaking, similarly to cx sprint.

The spoke angle on the rear ds is less advantageous and it helps to pick a spoke that doesn't stretch as much. X mm stretch on the DS spokes will allow for a greater rim deflection, than X mm stretch on the NDS side will.

On a front disc brake hub the wheel is indeed dished aswell but not significantly. Sure it depends on the geometry but if the tension is any indication of spoke angle (which it is to a big extent), then the rear will have a much greater difference between the flanges than the front. The rear can differ 50-60kgf between flanges and the front merely 10kgf.

So if you want low rim deflection you pick a spoke that doesn't stretch as much, (or if dished = an asymmetric rim). A 5gr spoke will stretch less than a 4gr and so on. But the DS side is the lower hanging fruit if one wants to get the least amount of deflection for the weight added.

Still picking a good hub will help much more than obsessing about spokes. The priority should be the hub first. A good hub with cx-rays can outperform an average hub with cx-sprints. If you use all the tricks in the book, it adds up. Good hub, asymmetric rim, a size larger spoke on DS, internal nippes etc.

Re the hub, DT Swiss 240 for this build. I am happy with Carbon Ti for my rim builds but the odd mention of cracked flanges has me thinking the DT Swiss is a better option for a disc brake wheel.

My other disc wheels are 28 spoke and they are rock solid. I did once try some 2:1 24 spoke wheels on I9 hubs. Granted the rims were alloy and not that deep, but there was a bit more wind-up in the front under hard braking than I felt was acceptable. I'm hoping with a 40 or 50mm deep wheel that 24 spokes up front will be adequate under hard braking.

[alcatraz]

In another thread many agreed that campy front disc wheels had probably the least flex when braking. It's interesting because they are triplet. It's just that they have a massive flange on the left side. 16 spokes on a massive flange seem to torsionally outperform 24 spokes on two average sized flanges. Interesting. It must be all about the angles then? How heavy are those spokes I wonder.

[emotive]

The LB AR45 is 30mm wide at the widest point. A great wheel choice for a 25mm tyre if you want to meet the rule of 105.

If you want to run 28mm tyres and achieve rule of 105 then go with the WR45.

[Mr.Gib]

Ended up going with LB Falcon Pro WR50 Flyweight on Carbon Ti, CX rays, with Sprints on the rear drive side. I am hoping the 50mm deep wheel and the relatively shorter spokes and better bracing angles will provide an adequately stiff wheel. Lots of folks bigger than me on such wheels. I should be OK. In the end the 32mm width was a no brainer. Just took a bit to wrap my head around being limited to 28mm and up for tires. Based on passed experience I imagine I'll be running no more than 60 psi. Now I have to buy a bunch of Corsa 28mm TLR. Wider rim, wider tires, disc... just more weight on top of more weight, etc. Moving from a 6kg rim brake VAM to a relative tank. I have accepted my destiny.

[bilwit]

Wider rim, wider tires, disc... just more weight on top of more weight, etc. Moving from a 6kg rim brake VAM to a relative tank. I have accepted my destiny.

No need to compromise, you can have both if you really want different horses for different courses, a concept that seems to get lost in the disc vs. rim armageddon debate