Tubular road rim for 29er wheel build?

Discuss light weight issues concerning mountain bikes & parts.

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AndrewL
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by AndrewL

This may be a dumb question, but I was wondering if anyone has tried building up a set of 29er wheels with carbon tubular road rims since they are, to my understanding, approximately the same size. Farsports' rims and wheels have been getting good reviews over in the road forum and it looks like they do a 260g, 24mm-deep rim with up to 32 hole drilling that might work. Of course, it might be slightly too small for a 29er tire.
Andrew "Jersey" L

by Weenie


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yourdaguy
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by yourdaguy

Road rims are generally not rated for disc brakes and also generally do not have enough spoke holes for a durable 29er wheel. In most cases you need at least 28 spokes and everything disc rated. Since there are few hubs and rims with 28 holes you will probably end up at 32.
For certain parts stiffer is more important than lighter.

AndrewL
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by AndrewL

It looks like the one I mentioned above from Farsports can be 28 or 32 holes so that would not be a problem. As for being rated for disc brakes I'm not sure what you mean. To my understanding rims are usually more stressed out by rim brakes than from discs. As in, a rim with a rim brake track will usually be heavier than the same rim without because it will require more material not only for the track but on the inside ("bridge?") to withstand the force of being pinched by the caliper. Correct me if I'm wrong.

It seems like the only factor would be the outer diameter in this case.
Andrew "Jersey" L

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yourdaguy
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by yourdaguy

The spoke holes have to be stronger on disc wheels since all the braking force is transmitted through the spokes to the rim and tire. A non-disc rated rim will soon start to crack the spoke holes on the spokes that pull when you use the disc. Also, a rim with a brake track will generally weigh more than a disc rated rim so I don't see the advantage of this build.
For certain parts stiffer is more important than lighter.

pushstart
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by pushstart

yourdaguy wrote:The spoke holes have to be stronger on disc wheels since all the braking force is transmitted through the spokes to the rim and tire. A non-disc rated rim will soon start to crack the spoke holes on the spokes that pull when you use the disc. Also, a rim with a brake track will generally weigh more than a disc rated rim so I don't see the advantage of this build.


This may be true in theory (I don't know that it is or isn't), but in practice folks like Velocity and Stans (and I am sure many others) offer disc builds with their road rims which to my knowledge have no additional material added to the spoke holes. It would probably be a good idea to use washers, but then that probably never hurts. And 28h is a pretty commonly available drilling for road rims ...

I believe Farsports offers disc builds of their CX rims? Or maybe I am confusing them with one of the others.

mentok
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by mentok

the farsport 24/25mm wide "CX" rims might be worthy candidates, though they are significantly heavier than the 260g rims you're talking about.

interested to see how this goes...

Oswald
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by Oswald

Planet X do carbon cyclocross wheelsets with disc hubs. Price is pretty damn impressive also...

AndrewL
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by AndrewL

Those are a good price and the weight is pretty good, too, but I'm looking for rims that are sub-300g or tubular wheels that are sub 1200g and far below the price bracket of Extralite and AX Lightness.

I guess it doesn't matter that much since a pair of tubular 29er tires weigh 200g more than their clincher counterparts and there are several reasonably priced 29er clincher wheelsets in the 1400g range. While I love Stan's bead hook I would like something stiffer than the Race Golds at the same weight; though I have not tried the that wheelset, I'm just going on reviews. Farsports' carbon 29er wheelset is advertised at 1410g but I'm leery of running them tubeless. Even though they are probably stiffer it's not worth the trouble dealing with burping tires if they don't have the tight interface with the bead. So I was thinking that a carbon tubular wheelset might fit the bill.

Those 260g rims that I mentioned are 20.5mm wide. Do you guys think that loosing 3.5mm of width (Enve tubulars are 24mm wide) would be a big deal? Maybe we can convince Farsports to make a 24mm-wide tubular rim that's a few grams heavier.
Andrew "Jersey" L

HillRPete
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by HillRPete

Lofty goals, but I would be wary of using a big tyre with narrow rim, and run it at low pressure. The Glueing tubulars thread has lots of good info, including CX glueing practices.

In general I'd not worry too much about spoke holes tearing from disc usage, unless you're a beefcake. The (also negative) acceleration offroad seems to be limited by grip anyway. What might be a concern however, is that a single bottom-out on a 260g rim could be the end of your race. For hillclimbs and smooth XC courses such a set would be quite appealing, though.

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LeDuke
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by LeDuke

I'd love to have a set of 26mm tubular rims, like those on the DT Swiss 950Ts.

Are these companies listening?

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the_marsbar
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by the_marsbar

AX Lightness claim the SRT CC 29er rims weigh 255 g each, and measure 28 (height) x 25.5 (width) mm. The ENVEs are not too far off, and probably a bit stiffer because of the incresed weight.

Maybe I missed something, but why not go for tubular rims by either AX Lightness or ENVE?

tonytourist
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by tonytourist

Cost? :P

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LeDuke
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by LeDuke

So, looking at the DT Swiss 950t rims vs. the 23mm wide generic carbon offerings, it looks like they have more or less the same gluing surface, in terms of width available to support a tire. Anyone have experience with either, when it comes to mounting 50mm tubulars?

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mcnbikes
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by mcnbikes

I've built up AX-lightness tubular 29er rims with extralite hubs and CX/rays however these rims which produced 1090gr 29er wheels are totally different in profile to a road rim they're quite wide and feel far stiffer both radially and literally. My suggestion don't risk it use Innolite or AX or even FRM alloy

riding2013
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by riding2013

Hi I am new member here. :D
Would like to discuss with you guys about those cheap china carbon tubulars.
My 29er wheel seems heavy, slow , sloggy ect. I am king of feeding up with it.. :x
Just thinking mtb tubulars would gain some advantages in ways of speed, weight and performance....

I have questions.
29er tubular tire options seems limited??
I can't find much vendor that offer wide 29er tubular rims, do you have recommendation?

:welcome: and idea?

by Weenie


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