I was inspired by this thread and bought some 700x35 Rene Herse Bon Jon Pass tires for my Roubaix. The frame can handle a 33mm tire, so I though a few extra mm wouldn’t hurt…but the tires are just about 38mm. That leaves 2.5mm on each side at the chainstays. There looks to be plenty of room at the seat stays and fork.
My wheels are 51mm deep Bontragers and 23mm internal. I’ll only be on the road (though surfaces around me can be quite rough).
Hard to capture but here are a few. I can just stick a 2.5mm Allen wrench in between the tire and chainstay. I only did the back wheel so far…knew that would be the tricky part if size was a concern.
Be careful. Sometimes rims flex and then you’ll get rub. I’ve seen situations where people have worn down the carbon on their frame in that spot. I’d keep an eye on it.
Just a quick comment here since you mentioned the Firecrest 404 wheelset explicitly: I think many roadies still use tire pressures that are too high. The recommended pressures for modern, wide rims are much lower that what you quote. The tire pressure recommendations by e. g. Zipp and Enve are consistent for rims with the same internal width. For example, Enve’s 4.5 ARs, Zipp’s Firecrest 303S and my 3T Discus C45|32 LTD all have an internal rim width of 25 mm. For a 28 mm tire, Enve recommends 53 psi at my weight (about 73 kg), Zipp’s recommendation in the dry is a little higher with 58 psi/62 psi. Zipp’s wet weather pressure recommendation is closer to Enve’s. I run my 28 mm tires at about 60 psi (I add 2-3 psi extra in the rear). When you look at the recommendation for 25 mm tires, Zipp recommends 67 and 71 psi front and rear, respectively.
Of course, these recommendations are just starting points. You might want to lower pressures if you are riding in the rain or across roads with bad road surface. I’ve lowered my tire pressures in a race on my old road bike with traditional rims to 65 psi, and it felt great. Was I minimizing rolling resistance? Nope. I was maximizing grip in the corners. Felt pretty good on a disc brake bike with 28 mm wide tires, many competitors with narrower tires and fancy carbon rim brake wheels really got spooked.
@AJS914
Not just flex, but also debris like small stones may get stuck and scratch your paint. On the other hand, I don’t have that much more clearance (from the top of the tire) on my 3T Strada. Probably you will be fine, just be ok with occasional scratches and keep your bike clean.
My advice would be to respect the 4mm clearance European spec. I’ve had road debris kick up between tire and chainstay, pretty sketchy when that happens.
I’d love to try them, but it would have to be the extralights, and like you I’m very reluctant to try them in a tubed version: I have visions of multiple punctures every ride. If that wasn’t the case, I could maybe bring myself to stomach the cost…
In response to myself (lol) I didn’t have great luck with Vitoria Corsa 2.0s on local lanes here in the UK. Lovely ride feel and very fast (and looked gorgeous in tan wall) but absolute puncture magnets.
I have the Extralight RH Bon Jon’s on Zipp 404 Firecrests as my road wheels on my Diverge. Great looking set up on your Roubaix. Enjoy the supple life!
But indeed, you’d still have to find and combine them with the right tire, since at speeds up to 20 and at least 25 km/h a rubbish tire will easily erase any advantages of a good combined CdA of tire and rim vs a box rim or an overized tire to a narrower rim with a good rolling tire just because of the big discrepancies you find on tire rolling resistances.
Then yes, the right (not to high) pressure is important and while wider tires not automatically provide less rolling resistance (with equal absolute tire drop) and they also are not automatically more comfortable if you run them at such equivalent pressures - you gain more buffer against impacts and you gain quite some really nice confidence for cornering and such. Again, if German language is no barrier to you, I’d like to refer you to the following article of mine: Der optimale Reifen für Rennrad-Langstrecke, Ultracycling-Events und Bikepacking-Rennen – Torsten Frank . : : . tfrank.de – Das Blog
In the end you still want to find the sweet spot for your personal riding situation as the draw backs do add up… If they weren’t we’d all happily ride fat bikes for every occasion.
Even with a nice rolling tires (I’d wish Conti and Schwalbe would do 36 mm versions of their GP5000 and Pro One, respectively) and a wide enough aerodynamic rim (and therefore a good Cd), the ‘A’ portion of the CdA is rising. As is the weight of the rubber and the weight of the inner tube or the sealant you are running.
And if you aren’t carefully tuning your tire pressure but indulge too much into the “comfort” area where you might or might not need it (depends on the aim of your ride and if it’s a competition or not) you are also increasing your rolling resistance.
That makes it so fascinating. And that is just for road! Now with Gravel and Offroad there is even more to ponder and consider…
Personally I am sure this will happen. Flow says their wider wheel (allsport maybe?) is faster with a wider tire than their rim brake wheel with a narrower tire so it might not be any slower to get to the 35-40mm range with a wide aero rim.
Interestingly, Schwalbe seems to have read this and decided to quickly show a new Pro One in 34 mm at the Eurobike Show. That’s cool. A bit bummed they kept the small 2 mm increments (30, 32 and now 34) and not went a bit more staggered (like you would do on a drive train cassette where the bigger cogs feature bigger tooth jumps because, yeah, physics…). So I’d really liked to have them come out with a 35 mm or even a 36 mm Pro One. And if just because that one would fit like a glove onto my 29 mm internally and 40 mm wide externaly Gravel Aero carbon rims.
But - 34 is a nice addition to their lineup. So better than nothing.
Indeed, I would love to test the Challenge Strada Bianca in 36 mm. The one thing I’m very afraid of is that I won’t be able to mount them. I recently just sent a pair of Challenge GetAway back because already getting just one side of those on my rims proved to be so tight that I realized I don’t want them. And I had my share of difficult to mount tire - rim combos. So I can estimate whether it’s somewhat ok to mount vs a very difficult job needing a lot of elbow grease and every trick in the book (trust me, I know them all) vs a lost cause.
I do wonder how good the Maxxis Velocita AR is (both in regards to mounting and more importantly ride feel and rolling resistance). That one is available in 40 mm width and several different models.
I also already have the Schwalbe G-One Speed in 36 mm width here. I want to test them in regards of CRR but won’t hold my breath as these aren’t reported to be anything good in that regard. But - every Schwalbe tire model I used in the past was reliable and easy / normal to mount on any rim I used.
These are my Nextie Premium 45 AGX rims laced on DT Swiss 240 EXP hubs.
In the above picture you see them with Schwalbe G-One R in 40 mm mounted. Gorgeous riding.