Another wheel/tire width question!

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cpac54
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by cpac54

I managed to track down a frame I've wanted for a long time, a Cervelo RCA!

The frameset only has clearance for 25mm tires according to the info I can find.

Looking at wheelset options, I'm wondering what width of wheel I can safely go with, without running into clearance issues?

I've been looking at the Campy Bora WTO 33 and 45 clincher (int. 19.5mm and ext. 26.5mm). Would running a tire like the GP5000 work? Would newer gen. wheelsets like the ENVE 3.4 (int. 21mm and ext. 27.5mm) even be an option?

Or would I be better served trying to find a wheelset with smaller diameters, like 17 or 18mm internal and less than 25mm external?

I'm admittedly fairly clueless, so I'm grateful for any and all help, especially from those who have an RCA or older gen R5 themselves!

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MrCurrieinahurry
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by MrCurrieinahurry

Maybe shoot cervelo and email and ask them directly.

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bilwit
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by bilwit

Better to find someone with the same frame (maybe in the build section) and ask them. Many times the "limit" listed by the manufacturer is around one size down, though it's not always the case, so it's hard to know without trying it. GP5000 clinchers still mount a little bigger than the listing measurement (also widens further with wear), but a 25mm should only add a mil or two beyond a 25mm rim. A 23mm will probably measure closer to 25mm.

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cpac54
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by cpac54

Thanks for the replies.

I did reach out to Cervelo, but they weren't able to advise me further unfortunately.

I was however able to dig up the following from what appears to be an old Cervelo tire size recommendation chart:
Screenshot 2021-10-04 at 19.57.12.png
2.5mm clearance seems tight to me, however it appears that Cervelo sold the 2015-16 R5s (same frame shape as the RCA) with the HED Ardennes + LT wheelset (21mm internal width, 25mm external) paired with 25mm Conti Grand Prix tires, which I'm guessing plumped up to at least 27mm (maybe more) on a rim like that.

I used to ride a 2016 R5 myself and ran 25mm a Conti GP4000s II tire on the rear (18mm int. rim) without issue (I never even thought to check clearance back then). I was able to mount this setup to my old R5 frame (retired due to damage). The tire measured 27.2mm wide and left me about 3mm clearance between tire and chainstay.

Looking at wheel options for the RCA, a 25mm Conti GP5000 on a modern 21mm internal rim (like the enve 3.4 or roval clx 32) could run as wide as 28mm once it's been ridden a while, which would leave 2.5mm clearance to the chainstay. If I believe the old chart above, that should be ok.

What do you all think about running a tighter clearance like that? Or would you look for a wheelset with a smaller internal diameter (18mm or 19mm) like the last gen. Campy Bora WTO 33?

Maddie
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by Maddie

Congrats on that RCA frame! Your 2016 R5 already had bigger tire clearance than earlier Cervelos if I remember correctly. Maybe worth a read:
viewtopic.php?f=3&t=166960

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cpac54
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by cpac54

Maddie wrote:
Thu Oct 07, 2021 8:01 am
Congrats on that RCA frame! Your 2016 R5 already had bigger tire clearance than earlier Cervelos if I remember correctly. Maybe worth a read:
viewtopic.php?f=3&t=166960
Thanks for the link, despite countless searching on WW, I've never come across that thread!

Does seem to me that, even if I can get something like an enve 3.4 (21mm int, 27.5mm ext) w/ a GP5k to work, it's probably not the ideal solution in terms of frame clearance. Probably safer to opt for something with a bit less width.

Something like the WTO 33 (19mm int, 26.5mm ext) would give me an extra .5mm on each side. Matching Campy wheels with a SRAM groupset just seems so wrong somehow! lol.

alcatraz
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by alcatraz

It's best if you just put some arbitrary wheels in the frame and measure the clearance.

Don't forget to take the wheel deflection into consideration or you'll lose some paint. Personally the place we've observed has had the least clearance is between the chainstays. But, every frame is different.

You might even be able to squeeze in the tire you want by just dishing the wheel a smidge to help even out the clearance. For the rear wheel though, remember that the wheel deflects farther to the non drive side so you need a bit more clearance on that side. Same goes with brakepads, which many don't know about. :)

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cpac54
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by cpac54

alcatraz wrote:
Thu Oct 07, 2021 10:47 am
It's best if you just put some arbitrary wheels in the frame and measure the clearance.

Don't forget to take the wheel deflection into consideration or you'll lose some paint. Personally the place we've observed has had the least clearance is between the chainstays. But, every frame is different.

You might even be able to squeeze in the tire you want by just dishing the wheel a smidge to help even out the clearance. For the rear wheel though, remember that the wheel deflects farther to the non drive side so you need a bit more clearance on that side. Same goes with brakepads, which many don't know about. :)
Thanks. Yes, clearance at the chainstays is precisely the issue with the RCA/R5.

I was able to test clearance with an alu wheelset on an R5 frame (same frame as the RCA essentially) yesterday. Wheels were DT Swiss PR 1400 (18mm int, 21.5mm ext) with 25mm GP4k, 25mm GP5k and 28mm GP5k.

Measured widths and clearance for the tires tested was:

25mm GP4k (27.2mm wide, 2.9mm clearance) *I had run this combo (rear wheel only) previously on my R5 without issue
25mm GP5k (26.6mm wide, 3.2mm clearance) *I had run this combo (rear wheel only) previously on my R5 without issue
28mm GP5k (27.8mm wide, 2.6mm clearance)

The 28mm tire measures ca. what a 25mm GP5k on a 21mm int. rim would, if I'm not mistaken and thus gives me an idea of what a 25mm tire would fit like on a wheel like an enve 3.4. That rim is 27.5mm wide externally, so even with a smaller tire, the rim would still be quite wide.

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