Weight Weenies

Other than a wheel build for use with cycle cross tubulars, is there any benefit gained from using a wider tubular rim (i.e. Plus 21mm wide )?

I have my eye on a pair of Corima 32mm carbon tubular rims shod with 25mm or 27mm tyres (Veloflex Roubaix or Vlaanderen). Their shallow rim is available in either 22.6mm width:

http://store.corima.com/corima-32mm-car ... bular.html

or 26mm width:

http://store.corima.com/corima-32-mm-w- ... -wide.html


Are the wider rims for use with cyclocross tyres or would they work with road tubulars?

Wide is all the rage now for road. Campagnolos are 24mm for a couple years now, Enve 27 and so on...

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For tubulars, it’s really about the radius of the rim bed that is most important. The closer it matches the radius of your tubular the better. Of course, there’s a fair bit of leeway there, but so long as you’re able to get a good glue bond across the entire base of the tire then you should be fine.

So on the Enve site their SES 4.5 tubular rim is listed with a 27mm outer diameter and 18.5mm inner (and there is mention of use with a 23mm tubular).

Am I correct in thinking then, a 26mm wide Corima rim, linked to further above, will work with a 25mm tub?

I read a post over on Velopicide Saloon where someone had mentioned the edge of a rim not gluing properly to the tubular tyre.

I enjoy riding the wider clinchers a lot of us now are using (HED C2's Spring to mind) but does this apply to tubular rims in the same way as clinchers in terms of aerodynamics, etc?

After Enve introduced the Twenty9 XC tubular, I had a couple 28 hole wheelsets built on DT 240s 6-bolt disc hubs for cross racing. I seem to recall that The rims were ~24mm wide and while they made for a very light race wheel, the shape of the tubular channel was a bit more acute than other tubulars which meant it took a bit more attention to detail to ensure proper gluing so as to prevent the tire from rolling off on tight switchbacks cross course designers love to put at the bottom of a high speed descent.

Eleven21 wrote:So on the Enve site their SES 4.5 tubular rim is listed with a 27mm outer diameter and 18.5mm inner (and there is mention of use with a 23mm tubular).

Am I correct in thinking then, a 26mm wide Corima rim, linked to further above, will work with a 25mm tub?

I read a post over on Velopicide Saloon where someone had mentioned the edge of a rim not gluing properly to the tubular tyre.

I enjoy riding the wider clinchers a lot of us now are using (HED C2's Spring to mind) but does this apply to tubular rims in the same way as clinchers in terms of aerodynamics, etc?

I've got Zipp 303 tubulars, so 26.2mm wide at the brake track, I run 25mm Vittoria Corsa Elites at present with no issues.

In terms of gluing, I can't imagine any problems if the tire is narrower than rim (provided they match well as Calnago pointed). It might actually be more aerodynamic than same size, let alone narrower rim. However there is a risk of rim damage in certain situations. Imagine being forced into a curb by a vehicle. You will scrape the rim instead of the rubber. Same can happen with longitudinal road cracks, loose rocks etc...

Consider that a rim has no more than 90 degrees of solid radius, and usually much less. So given the full 360 degrees of a tubular, and the 180 degrees of the inside half of the tubular circle, the tire must by definition be wider than the rim in order to sit evenly on the rim.

I have R9100 tubulars wheels and 25mm Vittoria Corsa’s. Rims are 28mm wide.

TurboKoo wrote:I have R9100 tubulars wheels and 25mm Vittoria Corsa’s. Rims are 28mm wide.

28mm at the very edge of the tire bed? Or do they bulge out at the sides for toroidal aerodynamics, and that's where the 28mm is measured?

From my experience, it comes down to the radius of the rim bed as Calnago mentioned. Hed3 is the most extreme example as the rim bed was designed to go flush to a 19mm tire so the sidewalls were high. Mavic CCU is next in line.

22.6 should probably be fine unless they did something goofy like make the rim channel high and specific to a 23 tire. I had Mavic Ksyrium Pro Carbons that were the same width and they paired well with a 25 tire. Enve 3.4 seems to be on the other end of the spectrum and the radius of the rim bed seems pretty oblique. Even the rear at an external 24mm still pairs well with 27mm tires.

UpFromOne wrote:Consider that a rim has no more than 90 degrees of solid radius, and usually much less. So given the full 360 degrees of a tubular, and the 180 degrees of the inside half of the tubular circle, the tire must by definition be wider than the rim in order to sit evenly on the rim.

So to clarify, if I chose the 26mm wide corima tubulars I would need to use the 27mm wide veloflex tubular tyres? Would the 25mm veloflex roubaix be too narrow?

You will be fine with 25, just be careful about where you stick them (kerbs, deep holes, stone pavement with big gaps, tram tracks etc) I just glued 23 Vittorias to my 24mm Boras and it falls in perfectly with no edge gap or other problems. One thing is that outside width is one thing, inner width is another. On Bora the edges are rounded so the actual gluing width is less. I don't know how Corima looks but I find it had to believe they have knife like edges.
Use 27 if you have really bad roads, want to go on gravel/dirt or comfort is your main priority. Your frame or brakes might not allow them though, check clearance first. 25 should be more of a sweet spot for comfort/weight/fast feel.

The fillet brazed MAX frame I've had built has room for 30mm tyres. 27mm Veloflex Vlandereen will fit no problem.


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UpFromOne wrote:

TurboKoo wrote:I have R9100 tubulars wheels and 25mm Vittoria Corsa’s. Rims are 28mm wide.

28mm at the very edge of the tire bed? Or do they bulge out at the sides for toroidal aerodynamics, and that's where the 28mm is measured?

Late reply

I measured 28mm from the brake tracks.
My rim is the one on the left

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