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PostPosted: Tue Aug 29, 2017 2:23 am 
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I'm contemplating if I want to get the new Mavic Cosmic Ultimates or keep the current CCU and just run 25mm Veloflex on them. I'll probably end up ripping off the Carbons and putting Roubaix on to see for myself, but does anyone have input of 25mm tires on 21mm rims vs 25mm on ~25mm rims?

I've seen discussions in the past that the general feedback was it didn't matter with tubulars BUT, I do recall there being a distinct improvement in handling going from Reynolds FortySix (old, 21mm version) with Roubaix to Bora 35s with Roubaix. At the time, it was shocking how much better the Boras were. I've been trying to find that type of disparity in my other wheelsets but I can't. Most of the wider wheels I've been on over the past couple months have handled similarly with Roubaix, nothing night and day like I previously experienced.

Anyone with similar experiences?

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Current Stable. The Snob Machine | The Crumpton
The Ex's. LS Siena: 6.21kg | Parlee Z5 SLi: 5.9kg | LS Xicon: 5.76kg | C59: 5.7kg | Cervelo R5ca: 5.09kg | Fuji Altamira SE - 6.2kg | Scott Foil - 6.2kg | Evo - 5.18kg | LS Classic - 6.7kg


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PostPosted: Tue Aug 29, 2017 3:44 am 
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RyanH wrote:
I'm contemplating if I want to get the new Mavic Cosmic Ultimates or keep the current CCU and just run 25mm Veloflex on them. I'll probably end up ripping off the Carbons and putting Roubaix on to see for myself, but does anyone have input of 25mm tires on 21mm rims vs 25mm on ~25mm rims?

Anyone with similar experiences?


I own the "old" Mavic CCU and ride 24mm Schwalbe one tubular tires on them - and the combination is great. I rode them in the Alps this summer for 2.5 wks and fast cornering was perfect. Also the comfort on the 24mm is great - better than the 22mm Conti front tubular on my Bora wheels ( Rear also a 24mm Schwalbe One ). 24 mm for me is a good choice between volume and speed/aerodynamics on a smaller rim.

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Posted: Tue Aug 29, 2017 3:44 am 


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PostPosted: Tue Aug 29, 2017 8:17 am 
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Location: Athens, Greece
I use the narrow LW ventoux rims with 23mm front and 25mm rear continentals. Everything is fine.
I cannot see how the width of a tubular rim affects the performance of the tire since the tire is glued. I guess the much better overall quality of Boras over the Reynolds is what you immediately felt and not the width of the rim.

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PostPosted: Tue Aug 29, 2017 11:05 am 
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if the tub is really too wide, it won't be a good match for the rim bed and adhesion will be reduced, but 25mm is ok

fwiw i've often used 23/25 (criterium/roubaix) from/rear on my obies, these are 20mm wide rims, but i'm finding i actually prefer narrower, currently got sprinter front and criterium rear, in windy conditions they seem less snatchy at the front than with the wider tyre


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PostPosted: Tue Aug 29, 2017 1:17 pm 
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Going from the old enve 65 mm front tubular to a 50 mm bontrager with modern/wider shape was a huge improvement in handling and I am not talking about in windy conditions. I still have the 65 mm enve on the rear, wondering what it would be like to have two new modern rims rolling.


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PostPosted: Wed Aug 30, 2017 12:56 am 
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My thought was that with the wider rim there's more support for the tire, so it won't deform in the same manner that a narrow rim would. I was going to make a drawing but this is as far as I got:

Image

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Current Stable. The Snob Machine | The Crumpton
The Ex's. LS Siena: 6.21kg | Parlee Z5 SLi: 5.9kg | LS Xicon: 5.76kg | C59: 5.7kg | Cervelo R5ca: 5.09kg | Fuji Altamira SE - 6.2kg | Scott Foil - 6.2kg | Evo - 5.18kg | LS Classic - 6.7kg


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PostPosted: Wed Aug 30, 2017 1:28 am 
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yup, my thinking as well.


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PostPosted: Wed Aug 30, 2017 8:36 am 
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In practice both tires deform the same way, it's not like clinchers.

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PostPosted: Wed Aug 30, 2017 4:59 pm 
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I've run Veloflex tubulars on both the older 20.5mm Bora and the newer 24.2mm wide Boras. Sizes run on the older boras... 22mm Veloflex Carbon, 23mm Veloflex Carbon, 24mm Velolflex Roubaix, 25mm Velolflex Roubaix. On the newer Boras I've run 25mm Veloflex Roubaix/Arrenbergs and 27mm Veloflex Vlanderens.

I think for me the sweet spot on the older Boras is the 24mm tire. With tubulars the rim bed radius is what's important with different tire sizes. With the older Boras a 25mm tire is not a perfect fit and will tend to get "pushed up" a bit with most of the pressure on the edges of the rim versus a more even distribution across the entire rim bed. In fact, the 25mm tire on the older Boras meant that the clearance on my C59 was really tight, doable, but tight. The exact same tire on the newer Boras sits just a bit lower due to the relaxed rim bed radius providing the extra 1-1.5 height clearance that I needed to run these tires with totally adequate clearance. So I like them.

The wider rim also provides a more stable platform for the tire simply because there's more of it and I find them to be more laterally stable as well. I found the 27mm tires a bit too voluminous and mushy feeling for nice roads, so that experiment is over. What I haven't tried is a 24mm tire on the wider Boras, but might just do that next time, even though the overall width of the tire will be slightly less than the outside width of the brake track, which I don't really like so much just from a rim protection point of view. I don't care about any aero properties lost or gained at the rim tire interface. The feel of tubulars vastly outweighs that aspect for me. I can feel the handling differences of a tubular tire. I cannot perceive the slightest difference in anything if my tire has a perfect or imperfect interface with the rim. Although if that's what you're after, then I've not seen a better tubular rim/tire interface than the older Boras with a 23/24mm tire.

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PostPosted: Wed Aug 30, 2017 11:43 pm 
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:thumbup: good info, Calnago.
24mm Veloflex it will be then for my older Bora. :beerchug:

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PostPosted: Wed Aug 30, 2017 11:54 pm 
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Trouble is, veloflex doesn't make a 24mm Roubaix anymore. It is now 25mm. I think I'd be inclined to try the 24mm Specialized Turbo Cottons however. I've heard good things about them.
When they stopped making the 24mm Roubaixs I stocked up with a few pairs, most for my Ambrosio Nemesis rims. But then tried them on my old Boras and loved them so much that I'm inclined to try them on the new Boras as well when the next opportunity arises.

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Colnago C60 - PR99
C59 Five Years Later
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PostPosted: Thu Aug 31, 2017 12:13 am 
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23/25 then. Bugger, life is full of compromises. :wink:

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PostPosted: Tue Sep 12, 2017 7:36 am 
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I am Running the DT Swiss RCC 32 Tubular wheels. Great wheels (1090g) by the way!

They have 20,5mm wide rims, DT Swiss recommend a max tire width of 22mm it is even printed on the rim - but I would like to go for the Vittoria Corsa 25. Do you think they are to wide? Could they maybe jump of the rim...?!
Maybe I should just go for a 23 Corsa...

And what about the ax lightness ultra 25t - they also only got 20,5mm width rims but allow until 28mm tires!

What are your thoughts? Try and error could be painful ;)


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PostPosted: Tue Sep 12, 2017 9:33 am 
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Location: Great Southern Land
I can tell you that I am running 25mm Vittorias on my Ultra 25's with no issues...... So why not dry mount on your DT's? I personally can't see why it should be a issue.

BB

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Posted: Tue Sep 12, 2017 9:33 am 


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PostPosted: Tue Sep 12, 2017 3:57 pm 
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Location: Canada
I had a set of FFWD F6R tubular with 20.5 mm width.
The best fit for the "channel" they provided was the older 22m veloflex Carbons (110-115 PSI).
With the bigger 23mm's from Vittoria, the cornering and sprinting/punching wasn't as good, you could feel tub deformation.
My 25mm wide wheels feel so much better cornering with 25mm tubs (100-105 PSI).
My take is the larger (and proportionnaly) deeper) the "channel", the larger glued surface, less deformation applied to the tubular. For road purposes, I would put it in the "pro" column.
For wet or soft surfaces, CX and MTB, less traction...

Louis :)


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