29er rims for road?

[d_douglas]

I am planning a new set of disc wheels for my cx/commuter bike and am looking into rims. In terms of handbuilts, anything is possible, but for prebuilts, is it possible (or advised) to use a standard 29er rim with 25mm slicks?

I guess what I am asking is: what downsides are there to using a narrowish 29er rim vs a standard road rim (without a MSW)?

Can 29er rims withstand 100psi on a skinny tire?

I anticipate a set of new or used DT 240 or 240 disc hubs and the rims are up in the air as of now.



Please educate me!

[d_douglas]

Anyone? I need to start ruling in or out!

[keevon]

No issues with a "standard" 29er rim and road tires at 100 psi. Most 29er rims are in the 22-25mm range for outside width.

Plenty of rims straddle the line between road and mountain: Salsa Delgado Cross, for example. I believe Ergott has used Stan's MTB rims on the road.

Just be sure you pair disc rims with disc hubs. The sidewalls of a "disc-only" rim won't hold up to caliper brakes.

[Jack Brunk]

My Ergott built stan's crest rims are rated max pressure of 55PSI on down to 45PSI based on size of tire. I know that many have had issues trying higher pressures. Maybe it's not the way to go for what you looking for although I've been wrong at least a half dozen times today alone.

[gdw]

Jack's right, 29er mtb disc rims aren't designed to handle high tire pressures. Old Potatoe and Ergott can probably tell you a suitable model for road use but you can rule out the popular mtb models.

Standard Stan's disclaimer:
"The ZTR 29er Race Gold is a low pressure rim and it must be run at pressures of 15-33 psi. Higher pressures may cause damage to the rim and will not be covered in the warranty.
If you prefer to run high pressures, please consider purchasing a different rim from the ZTR product line."

[cetuximab]

I bought a disc cyclocross steel lemond frame for my commuter bike. I found a cheap 29r wheelset for 125 ish. I run 700x25 at 90 and 100 psi. They work great. The force inside a tube is determined by the psi and the radius. So 700x25 at 90 psi has similar force to a 29r x 2.1 inch at 35 psi.

[KidWok]

I'm using DT TK's up to 100 PSI with no problems. They come in both MSW and non-MSW versions. Nice solid rim.

Tai

[fogrider]

I bought a disc cyclocross steel lemond frame for my commuter bike. I found a cheap 29r wheelset for 125 ish. I run 700x25 at 90 and 100 psi. They work great. The force inside a tube is determined by the psi and the radius. So 700x25 at 90 psi has similar force to a 29r x 2.1 inch at 35 psi.

this makes no sense...the radius of a 29r is the same as a 700c rim. products are designed with a margin of safety (often times 3x the design), so sure it may work with 90 to 100 psi but after hitting a few potholes and jumping a few curbs, you may not think so.

[vqdriver]

I took it to mean the radius of the cross section of whatever tire.

[cetuximab]

The tension in a hollow cylinder depends on the radius of that cylinder and the inside pressure.
T = p x r.
T - tension force.
p - inside pressure (psi)
r - radius. In a 700x25 tire it is 25/2 or 12.5 mm. In a 29rx2.1, it is 2.1 / 2 * 25.4 mm/inch = 26.7 mm

"stan's crest rims are rated max pressure of 55PSI on down to 45PSI based on size of tire"

So running this rim with a 29rx2.1 tire at 50 psi has similar tension to running that rim with a 700x25 at 100 psi.

Laplace equation explains why there is more tension force on the wall of an aneurysm. The aneurysm has a larger radius. Larger radius, more force, higher risk of rupture. The blood pressure is similar the adjacent normal vessel.

[Ramjm_2000]

Per Stan's the low PSi rating is only when running tubeless. They told me to go by the tire recs when using a tube. I'm running ZTR 355s with vittoria 28 and 32c rubber without issue.

[d_douglas]

Per Stan's the low PSi rating is only when running tubeless. They told me to go by the tire recs when using a tube. I'm running ZTR 355s with vittoria 28 and 32c rubber without issue.

Wait, so all the previous stuff is irrelevant if I am using tubes (i.e.., clinchers) ?

I forgot to add that I will be using low-tech clinchers etc. so, my interpretation is that I can run 28mm slicks at 100psi if desired.

Am I correct>?


PS Cetuximab: thanks for the dissertation - very cool and wayyyyy over my head. Ill just trust you on that one.

[redir]

I was researching this as well since I want to do some road rides on my MTB. From what I gathered the pressure is not an issue but the width of the rim is. If you are running wide rims then you need wide tires. So a lot of 29r rims are quite wide and would be dangerous to ride 23 or 25's on. You would need more like a 35 at the least.

[d_douglas]

Yep, I am aware of the tire width issues. I was looking to use a 'skinny' 29er rim anyways.

FYI, I had a set of wheels built for my wife's city bike. I used Velocity Blunts and 32mm Conti city tires. I consulted Velocity directly and mentioned the tire width and they said that it was no problem.

Blunts are on the wide side, so with narrowish rims, I would think that 25mm tires would be OK. I plan on 28mm tires if road riding (and fatties for trail riding), so I am not too concerned.

[Ramjm_2000]

Wait, so all the previous stuff is irrelevant if I am using tubes (i.e.., clinchers) ?

I forgot to add that I will be using low-tech clinchers etc. so, my interpretation is that I can run 28mm slicks at 100psi if desired.

Am I correct>?


PS Cetuximab: thanks for the dissertation - very cool and wayyyyy over my head. Ill just trust you on that one.

You are correct. Width is the limfac, I wouldn't recommend going below 25c (28 seem to be the sweet spot). That said 28c at 100psi sounds kinda harsh.

[ergott]

My personal experience is with the ZTR 29er rims. I used them with anything from Hutchinson Fusion/Intense run tubeless to Michelin Pro Race 2s. I always kept pressure at 95psi or less (tubeless 85psi or less). The whole point of the wider rims and is that you can run them at lower pressures. I think that regardless of rider weight, you are better off at 100psi or less.