Wide rims versus wide tires?

[mhespenheide]

Forgive me if this has been discussed before -- if so, can you point me towards the appropriate thread(s)?

Has anyone ridden an A/B comparison of similar width comparisons between different sizes of tires and rims that ended up having the same final width? I'm wondering about something like comparing a 25mm tire on a wide rim versus the same tire in 28mm on a standard rim. To put it another way, is there something more to the ride of a wide rim than just the additional width of tire that it provides?

Second question: if there really is a benefit to the wide rim (beyond the extra width of the tire), as is talked about with the "bread-loaf" shape better than the "light-bulb" shape, do those benefits go away if a wide tire is used? Say, a 28mm (nominal) tire on a wide rim -- doesn't that get back to a "light-bulb" shape? If those benefits do go away, should we be looking at even wider rims? Should we be lacing up some 29'er rims for the road to go with 28mm or 30-35mm tires?

Thanks for any thoughts/input -- particularly on that hypothetical A/B comparison.

[Bruce K]

Some manufacturers already make 25mm rims (HED Plus).

Yes a 28 tire on a 23 rim just makes a larger "old" profile

BK

[Ralph]

Not everyone (me included) buys into the lastest fad of wide tires on wide rims. Especially for all uses, all riders, all body weights, all roads, etc. Agree the tire needs to fit the rim properly, and there are plenty of good uses for a wider tire. I even use a 700X25 on my daily rider. But my fastest wheels overall still have 700X23's. I might add I only weigh 155 and I ride on smooth roads.

[tigoat]

I have used ENVE 45 (traditional narrow rims) rims with 28c tires and ENVE 29XC rims (modern wider rims) with 25c tires. They do not feel the same way. The ENVE 29XC wheels feel much more smoother and faster and resemble more of a tubular feel. I have also used HED C2+ rims, which are probably widest road rims available right now. The HED C2+ wheels perform very similarly to the ENVE 29XC wheels. Bottom line is that don't fool yourself into slapping on some traditional narrow rims with wider tires and think they perform the same as modern wider rims do, as they are not the same.

[Mark McM]

I would expect that it to be not unlike comparing different profile automobile tires. On the one hand,a bigger tire (both wider and taller) will give a more compliant ride, at the cost of some lateral stability. On the other hand, lowering the profile (shorter sidewall height) for a given tire width will be less compliant, both vertically and horizontally. If this works the same on bicycle tires, than mounting a fat tire on a narrow rim (lightbulb shape) will provide much more vertical compliance, at the cost of less lateral stability. Widening the rim, but keeping the tire width the same (bread loaf shape), will improve lateral stability at the cost of some of the veritcal compliance - but it will still have more vertical compliance than the narrower tire.

[Charles M]

there's a formula for net tire size... It's a mix and match thing and it's just math... I think wheelfanatyk.com have a little measuring device.

[mhespenheide]

Originally Posted by tigoat

I have used ENVE 45 (traditional narrow rims) rims with 28c tires and ENVE 29XC rims (modern wider rims) with 25c tires. They do not feel the same way. The ENVE 29XC wheels feel much more smoother and faster and resemble more of a tubular feel.

Thanks for that, tigoat. Guess I'll have to at least sip some of the kool-aid and try out some wide rims... My budget may have to wait until more people are selling them used, but I guess they're starting to show up.

[RobJ]

Tigoat and Mark McM nailed it and my testing combos falls in line with Tigoat. The ride quality of the wide/wide combo vs. narrow rim/wider tire is very noticeable. Running latex tubes has also contributed to a nice improvement. One other point not discussed, but important too is the aero properties of the various combinations. Most of the wider rims paired with a 23mm tire are topping the charts for aero and rolling resistance. Obviously mostly a concern if time trialing or triathlon etc.

[professerr]

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[jamesutiopia]

Shifting from 23 to 25mm tires was a big improvement for me (190lbs, 63cm frame size). 28s have been even nicer, even on beautiful California roads. I've ridden 28s on Belgium+ rims, but not on narrow rims. They are nice for sure-footed descending.

I can see why this would be a less tangible benefit for more ideal-size riders.

[eippo1]

So to take this a bit further, I would like to fit a wider tire on my bike, but the limiter is the front brake having only 3mm clearance at the top with Conti 25's (that actually measure closer to a 28). If I went with a wider rim on this bike, would the tire, being less of a lightbulb, come down lower vertically since it is more spread out?

[zachateseveryth]

Originally Posted by Mark McM

I would expect that it to be not unlike comparing different profile automobile tires. On the one hand,a bigger tire (both wider and taller) will give a more compliant ride, at the cost of some lateral stability. On the other hand, lowering the profile (shorter sidewall height) for a given tire width will be less compliant, both vertically and horizontally. If this works the same on bicycle tires, than mounting a fat tire on a narrow rim (lightbulb shape) will provide much more vertical compliance, at the cost of less lateral stability. Widening the rim, but keeping the tire width the same (bread loaf shape), will improve lateral stability at the cost of some of the veritcal compliance - but it will still have more vertical compliance than the narrower tire.

A wider rim will result in a better ride for any tire. You're increasing the air cavity volume so you can run a lower pressure without having to worry about pinch flats.

[druptight]

Originally Posted by eippo1

So to take this a bit further, I would like to fit a wider tire on my bike, but the limiter is the front brake having only 3mm clearance at the top with Conti 25's (that actually measure closer to a 28). If I went with a wider rim on this bike, would the tire, being less of a lightbulb, come down lower vertically since it is more spread out?

That depends. See the first post here: http://forums.mtbr.com/wheels-tires/...th-756818.html

[Mark McM]

Originally Posted by zachateseveryth

A wider rim will result in a better ride for any tire. You're increasing the air cavity volume so you can run a lower pressure without having to worry about pinch flats.

The question wasn't about mounting the same tire on a wider rim, it was about comparing a wide tire on a narrow rim vs. a narrow tire on a wide rim (such that the final width was the same).

Also, air cavity volume by itself isn't what affects ride compliance (since there is virtually no compression of the air as the tire is loaded), but instead it is about the change in cross-sectional shape as the tire is compressed. For the same final tire width, the tire on the wider rim will actually be less compliant, since it takes less vertical compression to flatten the tire under load.

[ergott]

Originally Posted by Ralph

Not everyone (me included) buys into the lastest fad of wide tires on wide rims. Especially for all uses, all riders, all body weights, all roads, etc. Agree the tire needs to fit the rim properly, and there are plenty of good uses for a wider tire. I even use a 700X25 on my daily rider. But my fastest wheels overall still have 700X23's. I might add I only weigh 155 and I ride on smooth roads.

Seeing how you are from Florida I would agree. You won't see the same benefits that I do. Up here where the roads suck I love 23+mm rims and 28mm tires. I notice no loss of speed and my riding mates are jealous of how I glide over everything as they bounce around. I think slowly but surely I'm convincing some of them.