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3/6/11 1:24 A

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I have some Mavic MA3's that are 622x15. Adding 3mm would make them about as wide as my Model 58's. If course what one company calls a 23mm tire will often be different from what another company labels that size. I didn't like the tire profile when I mounted a 25mm Continental tire on my Model 58's.
I decided to go right to the horse's mount and see what the late great Sheldon Brown thought on this subject.

www.sheldonbrown.com/tire-sizing.htm
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His chart lists inside rim widths of 17 and 19 but inconveniently skips 18. For 17mm inside width he lists 25mm to 37mm wide tires as fitting and for 19mm inside width he lists 28mm to 44mm tires as a fit. Going by his chart anyway, 20-23mm would be too narrow for a 622x18 rim.

WONGERCHI's Photo WONGERCHI Posts: 3,889
3/5/11 12:56 P

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GIANT_STEPS:
I wouldn't call 622x18 wide, but rather standard. I've run everything from 20-32s on rims that wide. Narrow tires mate with the rims VERY well aerodynamically and yes, I've field tested this! I am measurably slower when I run a 23mm tire on a 18mm rim as opposed to a 20 (same tires, tubes and rims).

However, wider tires mate better with wider rims. Right now I'm running 22-24mm wide rims (22 on the roadbike, and a 24mm wide 29er rim for my commuting wheelset). 23mm tires mate wonderfully with the 22 rim. The 32mm tires that I use for CX and commuting match up very nice with the 24mm wide rim.

Definitely agree with you about "horses for courses" though. I ran a 20mm tire up front in a crit once. Never again.

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GIANT-STEPS SparkPoints: (65,379)
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3/3/11 4:06 P

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All else equal a wider tire has less rolling resistance than a narrower one. Tire rolling resistance comes mainly from hysteresis losses. The size of your contact patch is dictated by the load and the pressure of the tire. If you have 100lb of load on a 100PSI tire you would expect a contact patch of 1 square inch in size. A wider tire doesn't flex as much to make the same size of contact patch and has less hysteresis losses. Engineers have long known this but for some reason it took the bicycling world by surprise. When the first objective rolling resistance tests were published showing wider tires of the same model roll better nobody really seemed to believe it.
Of course all else usually isn't equal. The same model of tire is not usually available in all sizes from 18-40mm. Narrower tires are high performance tires while the wider ones are designed to be rugged. Since high performance tires have thin casings and treads this reduces hysteresis losses as well. If you could get the same carcass and tread on a 38mm tire that you get on a 23mm high performance tire I'd expect it to ride great. When choosing tires I opt for the widest tire in high performance models assuming it will fit my frame. My Cinelli can fit 28mm tires but in rear it is so tight that I have to let air of the back tire to mount or unmount the rear wheel so I generally settle for 25mm. My old Gitaine can fit almost anything.
When you ride faster than 25 MPH rolling resistance is a small fraction of aerodynamic drag so for the racing cyclist the optimum size balancing the needs of rolling resistance, weight, and aerodynamic drag is 23mm. For slower or non-competitive riders wider is basically better.

Edited by: GIANT-STEPS at: 3/3/2011 (16:09)
GIANT-STEPS SparkPoints: (65,379)
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3/3/11 3:43 P

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Few people know the ERTO size of their rims. I wish that all wheel and tire manufacturers would use unambiguous sizing like ERTO. What we have now is a terrible situation where we have multiple bead sizes in each of 20" 24" 26" and 28" Rims that are fractionally sized (26x1-3/4) are a different size from their decimal equivalent (26x1.75). The same sidewall numbers can indicate different sizes in different countries.
622x18 is a rather wide 700c rim. Too narrow a tire will not have a good profile on such a rim. My widest rim now are some old Wolber Super Champion Model 58's. Frankly I don't know their ERTO (wasn't commonly used back then) size but they are nice wide touring rims with an outside width of 23mm. I've ridden 700x25m tires but didn't like the way they looked so I went back to 700x28.

DANIELBS80's Photo DANIELBS80 SparkPoints: (316)
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3/3/11 8:29 A

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my bike came with 700x38 tires which i think is rather big. I dont go on harsh trails.

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PERRYR's Photo PERRYR Posts: 668
3/3/11 8:14 A

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Daniel,
I'll skip opinion on the 700X28 vs 700X23 tire on 18mm wide wheel.
Suspect that you are focused on road riding and think that the 23mm tire will be faster.
I doubt it. The contact patch of tire touching the road will be the same. A tad bit wider but at a given tire pressure, say 100 PSI, the area will be the same.
So, get a good road tire in that width and be happy for a slightly smoother ride.
If you want something more narrow, why not try a 25mm wide tire?

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3/3/11 7:40 A

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I'd like to get to the bottom of this once and for all. I have 622x18 wheels and I went to the LBS close by and they said I can't put on anything less than 700X28 tires on it but at another LBS further away but the same company says I can fit nicely down to 700x23 if I want. When I look online I see charts and other people say that 23+ tires will fit fine on 18mm wheels. What do I believe cause the people at the close by bike shop feel real strongly against smaller tires not being able to fit my wheel.

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