42mm UD Cava Tires
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Anthony Davila
Mar 14, 2025, 10:54:56 PM3/14/25
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Hello, I've been trying to figure out if my 2011 Homer could fit these 42mm Ultradynamico Cava (race/grey casing) tires but I feel that it's hard to know without just ordering them. The issue is that once I mount them, I can't return them.
From old Rivendell articles, it seems that the max the Homer could fit back then was around 40 mm without fenders. After emailing Ultradynamico, Ron told me that his Roadini (with a rim that has 19 mm inner width - which is the same as my current rims) had 42s and they measured "a hair below 40".
What do you guys think? A part of me wants to be safe and go for the 39mm, but on their site it seems like they run small on narrower rims. I've attached a picture of my Homer!
" The sizing is sorta funny, it is badged a 700c x 39, but on most modern rims it's been measuring a little smaller upon initial mounting, more like a 37-38mm then after some use these stretch out to almost a 39mm width. On more traditional, narrower rims they will measure smaller... closer to 37mm." - From UD's site.
From old Rivendell articles, it seems that the max the Homer could fit back then was around 40 mm without fenders. After emailing Ultradynamico, Ron told me that his Roadini (with a rim that has 19 mm inner width - which is the same as my current rims) had 42s and they measured "a hair below 40".
What do you guys think? A part of me wants to be safe and go for the 39mm, but on their site it seems like they run small on narrower rims. I've attached a picture of my Homer!
" The sizing is sorta funny, it is badged a 700c x 39, but on most modern rims it's been measuring a little smaller upon initial mounting, more like a 37-38mm then after some use these stretch out to almost a 39mm width. On more traditional, narrower rims they will measure smaller... closer to 37mm." - From UD's site.
Jim M.
Mar 14, 2025, 11:28:22 PM3/14/25
to RBW Owners Bunch
Hard to tell from the picture. Do you have calipers? How much width is there at the chainstays and between the forks with your current tires?
Anthony Davila
Mar 14, 2025, 11:43:49 PM3/14/25
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Oh I just included the picture to show the bike off, but it would make more sense to show it up close. This is my Reddit post with better pictures and 40 mm tires (that measured at 39.5).
Also, I used this equation to find the maximum tire width and I got 41.4 mm since I used the actual measurement of the current tire width:
max. tire width = 2 x (tightest clearance – 3 mm) + current tire width
Garth
Mar 15, 2025, 5:21:24 AM3/15/25
to RBW Owners Bunch
Me thinks you're pursuing very marginal gains in trying to rationalize the wider tire. From the photos I myself would stick with 38's as the 40's are even too wide for my sensibilities. Don't let the "wider is better" mythology cloud your judgement !
Will Boericke
Mar 15, 2025, 7:16:52 AM3/15/25
to RBW Owners Bunch
I have the Cavas mentioned mounted on 20 ID (I think) rims, and the Cavas measure exactly 42. Unlike most other tires I have :)
Will
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