Inside Rim Width for Pure Road

[ipenguinking]

What's everyone's ideal inside rim width for a pure road? I'm in the process of buidling a new set of wheels for my cutom titnaium road which have 32mm tire clearance, running 28mm tires normally. I prefer using hooked rim, tubeless setup. I'm currently running a set of DA 9270 C50 which have a 21mm inner width. So far I don't have any problem whatsoever. What would be the advantage/disadvange of having wider inner rim width?

[toxin]

Can put on wider tires without wrecking their aero performance. Only really matters if you feel you need more grip or comfort

[Mocs123]

Personally I think getting the ratio of inner rim with correct to make your tires match up with with the exterior width of your rim is most important. I'd assume for 28mm tires either 21mm or 23mm interal width would be about right, though there are some really wide wheels that have 25mm interal width that may work well.

[pdlpsher1]

If the rim gets too wide the tire’s sidewall gets exposed and are prone to cuts. Personally I’d rather sacrifice aero performance for fewer flats.


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[ipenguinking]

I think my current setup - 28mm tire on 28OD/21ID is a very good setup for comfort, handling and straightline speed. I don't think I'll ever go narrower than 28mm but 30mm is probably the max. I like the way that the tire sticks out a little which offers just enough protection for the rim. (leaning against the wall, cafe stop etc) I'm asking the question mainly because companies like Enve and Zipp started making all their high end models with 23 or 25 ID and wonder if there is benefit when running 28-30mm. I personally think they just want to consolidate the road/gravel models and cut the cost.

[robertbb]

Geek out on this (it's a great article):

https://www.bicyclerollingresistance.co ... #road-bike

"Road Bike Tires Conclusion

Our conclusion for road bike tires is that there is nothing to gain in rolling resistance when moving to rims wider than 72% of the (specified) tire width.

For 25 mm wide road bike tires that would come down to 17-18C rims which is what most road bikes already come with these days. For 28 mm wide tires, moving up to 19-20C rims would hit the sweet spot."

Remember that Jarno doesn't dig into "aero" here - the focus is on rolling resistance so the focus is on internal width.

As for external width you can extrapolate aero based on the 105% rule...

[Nickldn]

I think my current setup - 28mm tire on 28OD/21ID is a very good setup for comfort, handling and straightline speed. I don't think I'll ever go narrower than 28mm but 30mm is probably the max. I like the way that the tire sticks out a little which offers just enough protection for the rim. (leaning against the wall, cafe stop etc) I'm asking the question mainly because companies like Enve and Zipp started making all their high end models with 23 or 25 ID and wonder if there is benefit when running 28-30mm. I personally think they just want to consolidate the road/gravel models and cut the cost.

Enve and Zipp started making all their high end models with 23 or 25 ID for use with hookless tyres that have a maximum pressure of 72psi. The total air volume is higher with a wider ID, so a 25mm tyre starts to feel like a 28mm tyre in terms of air pressure requirements.

Shame for Zipp their top models are no longer compatible with 25mm tyres according to new ETRTO standards.

[Nereth]

I'm 86kg and using tubeless 25s front and rear of my aero road bike (optimised for rides averaging 40kph+, cruising speeds in the area of 45kph). I normally ride it at 85 PSI or so as that is supposedly around optimum for the mix of tyre vs suspension losses for my conditions.

I don't understand the need for 28s for comfort - when I want some comfort to ride home after the cafe stop, I've just dropped air out of the rear 25 and it becomes cushier than most are running their 28s at. Based on BRR testing, it's also not significantly less efficient than a 28mm at the same vertical stiffness. Rather, the minimum pressure of 25s appears to be when it becomes too squishy to handle confidently, which for me is far squishier than anyone is actually running their 28s at, for example - around 50-60PSI on my 25s, which would be like running a 28mm in the mid-high 40s range - how many guys at my weight actually want to run below that pressure on the road, and thus should consider 28mm or wider tyres?

Despite that, I'm looking at trying 28 on the back soon since I think my bike was designed with 28s in mind (came with a 28 on the rear), and my rims are 32mm wide at the widest point, so I doubt there will be much aero disadvantage, and it will satisfy my curiosity and let me ride an even wider range of pressures should the situation arise.

This discussion would be different if I actually saw people around me riding their wide tyres at actual low pressures, actually bouncing off the practical minimum pressure limit of the tyre and thus needing their wider tyres.

[voicycle]

Running tubeless GP5000s I get approx 26.5mm from a 25c on a 21mm internal rim, which is a great aero fit for my Roval Rapide wheelset. I get approx 31.5mm from a 28c on a 25mm internal rim, which is a great fit for my LightBicycle WR wheelset (32mm external). The new Enve and Reserve rims are in the same realm as my LB ones in terms of widths. 28s on my Rovals would fit the aero profile on the front but would balloon slightly wider than the rim on the rear.

I find the Rapides faster on an already fast course with good road surfaces, but most of the time I prefer riding the LB wheels. The speed penalty is barely noticeable, they're more comfortable, and I don't think I've met a paved road yet where the surface is bad enough to make me adjust my speed. I have zero concerns about exposed sidewalls given the tire profile, though I might feel differently if I were going to ride that setup on gravel. It's a perfect setup for training, leisure riding, audax, etc. If there's a road race with even a bit of questionable surface then I'll probably run the wider set there too - I'd rather be marginally slower in the wind and know I don't have to worry about potholes whilst sitting in the draft. It's actually an amazing setup for sitting tight on someone's wheel on roads I don't know - doesn't really matter whether they point out obstacles or not.

If I were spec'ing a wheelset for a new pure road bike with 32mm clearance I'd be looking at 25 internal and 32-34 external to support a 28c tire measuring 31-32. Since the bike is Ti rather than carbon I assume you're not building it for criterium racing, so maxing your width/volume seems like a no-brainer as long as you can preserve the aero function of the wheelset.

[montster]

25mm internal and 32mm external with 28mm gp5000 that balloons up to 30.4mm and 50mm deep. Wider internal gives more volume and ability to use lower pressures along with a tire/rim shape that is more toroidal. Downside of wider is heavier rims. Tire has a good looking shape and transition from tire to rim. Light bicycle WR50 rims. One of the first to emulate Enve's famous 4.5 AR that really kickstarted this wider is better trend. The next one to really be interesting are these next generation that apparently tested very fast and handles well according to Josh @ Silca. Might even be the ideal road wheel for some.

https://us.3t.bike/en/products/wheels/d ... 0-732.html

[Mr.Gib]

The next one to really be interesting are these next generation that apparently tested very fast and handles well according to Josh @ Silca. Might even be the ideal road wheel for some.
https://us.3t.bike/en/products/wheels/d ... 0-732.html

Seems pure gravel to me. For the road, the advantages over narrower wheels would have to be pretty huge to justify lugging around a 1665 gram wheelset, particularely when you can get 25mm internal as low as 1300 grams.

[montster]

The next one to really be interesting are these next generation that apparently tested very fast and handles well according to Josh @ Silca. Might even be the ideal road wheel for some.
https://us.3t.bike/en/products/wheels/d ... 0-732.html

Seems pure gravel to me. For the road, the advantages over narrower wheels would have to be pretty huge to justify lugging around a 1665 gram wheelset, particularely when you can get 25mm internal as low as 1300 grams.

Yes, but Josh mentioned that it is the most aero wheel he tested even when compared to 25mm and 28mm tires. Something may be special about the shape and if this can be repeated, may have huge implications for all future wheel/tire development. Imagine a 32mm TT wheel

https://www.slowtwitch.com/Products/Thi ... _8710.html

[Mr.Gib]

The next one to really be interesting are these next generation that apparently tested very fast and handles well according to Josh @ Silca. Might even be the ideal road wheel for some.
https://us.3t.bike/en/products/wheels/d ... 0-732.html

Seems pure gravel to me. For the road, the advantages over narrower wheels would have to be pretty huge to justify lugging around a 1665 gram wheelset, particularely when you can get 25mm internal as low as 1300 grams.

Yes, but Josh mentioned that it is the most aero wheel he tested even when compared to 25mm and 28mm tires. Something may be special about the shape and if this can be repeated, may have huge implications for all future wheel/tire development. Imagine a 32mm TT wheel

https://www.slowtwitch.com/Products/Thi ... _8710.html

Right, and surely it's possible to scale the same proportions down to a narrower width. And if so, then a narrower version will be more aero (and lighter). Love my fat tires (my 30mm 5000s TR is 33.3 WAM on 25 internal), but not convinced they could ever be as fast as something comparable in shape with smaller frontal area.

[montster]

Sure that would make sense and I'm sure they're all working on modeling it out right now for the next generation of wheels. It makes sense from a purely frontal area perspective, but it's also possible to go deeper, wider and make the whole thing more stable in crosswinds and cornering, especially since we have to consider rolling resistance on poor/normal pavement. I just want to see how wide everything can go and feel like we haven't flown too close to the sun yet so I hope they keep pushing.

Edit: also, the light bicycle wg44 that looks similar in shape and dimension to the 3t wheels can be built to be sub 1500g. Interesting....