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Old 11-30-09, 09:35 AM   #1
bobframe
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Critical Thinking on Tire Size

I have a new 60 cm Americano Co-Pilot that came equipped with Vittoria Randonneurr Pro 700x35 tires mounted on Velocity Dyad rims. Since I am new to loaded touring, I have no real frame of reference to judge these tires and to know whether they are overkill for what my needs are or not. I've taken a couple of short local tours and had zero tire issues so far.

So, I would like some help in assessing whether I really need a 35mm tire. I'm 230ish, bike weighs 31# and my load, including panniers and water bottles is about 40#, about 300# all in. My first "real tour" will probably be a month or so around the southeast US (Georgia/Florida Gulf Coast & Panhandle) and the anticipated riding surfaces include very limited gravel and the best two lane roads I can find...so nothing extreme at all. Load is distributed between front and rear Ortlieb panniers, I'd guess 35% front, 65% rear.

First, what options do I have regarding tire size?

Second, how much easier would a narrower tire (let's say a 28mm) would be to pedal (i.e., is there a meaningful lowering of rolling resistance??).

Third, given my specific configuration and planned riding surfaces, do I need the added durability that I presume I'd get with a wider tire?

And last, are there reasons other than those above that I should consider leaving well enough alone?

Thanks.

Last edited by bobframe; 11-30-09 at 10:31 AM.
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Old 11-30-09, 09:55 AM   #2
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For your size and weight carried, I personally wouldn't likely go less than a 700x32, and a 35 is certainly not overkill in my opinion. It will give you a smoother ride than a more narrow tire and likely be more forgiving as well. I'm not saying you can't make 28 work, but you will gain little in speed advantage and probably increase your likelyhood of pinch flats and other wheel related problems.
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Old 11-30-09, 10:48 AM   #3
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Options regarding tire size: Schwalbe makes 700C (622mm rim diameter) touring tires as wide as 50 mm, and some 29er tires as wide as 62 mm. Anything wider than 40-45 mm would quite likely be overkill for your stated use, though. For an idea of how wide a tire you can install on your bike, look where the current rear tire passes between the chainstays and see how much clearance there is. Remember that it's nice to have a little extra space there in case your rim goes out of true and starts wobbling side to side. You could also contact Co-Motion and ask them how wide a tire the bike will take. You could also fit tires as narrow as 18 mm on your rims, but I wouldn't advise trying to tour on them.

How much easier would a narrower tire be to pedal? Not much, if any, and it might be harder to pedal. In order to avoid pinch flats you would have to pump the tires to a higher pressure (and re-inflate them more frequently). On a glass-smooth, freshly paved road the advantage goes to a high pressure, narrow tire, especially with a light load. As the road surface gets rougher, the advantage shifts to the wider, lower pressure tire, especially as the load increases. Basically, the bike with the higher pressure tire ends up being lifted up and over every little (and big) irregularity in the road surface, while the low pressure tires flex more and absorb the irregularities.

Do you need the added durability of a wider tire? That depends. How do you feel about sitting at the side of the road fixing a flat tire in a drenching rainstorm? How much of your touring time and budget do you want to spend fixing and replacing tires?

I would suggest doing your first "real tour" on the tires that came on your bike, or a pair of high quality replacements in the same size if the originals are getting worn. If you've had zero tire issues so far, I would be reluctant to change anything. If you do decide to change to a narrower tire, I would try the tires out on some shorter rides before committing to a long tour with them. I suspect that the folks at Co-Motion thought things over pretty carefully before they spec'ed the tires for your bike, and I would be careful about trying to second guess them.
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Old 11-30-09, 11:59 AM   #4
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Those tires are fast and sturdy enough. Compared to other tires out there you could spend more for marginal differences. If you put 28mm tire on 24mm wide rim you're going to run out of a lot of cushion for no improvement in rolling resistance. You're more likely to scrape the sidewall or rim in rough conditions with that combo. I've got those tires and think they're very nice handling. The amount of gear you have will be a greater inhibition to higher average speed in hills than the size of tire. The only reason I could think of getting a different set of tires is if you wanted a wider contact patch in 35mm for dirt roads or wider tire for bumpy dirt roads. For 300lbs of rider, bike and gear you're not going to get any practical benefits going to 32mm. I could see 32mm being attractive for unladen riding for the same conditions, road and occasional gravel.
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Old 11-30-09, 12:09 PM   #5
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As a fellow Clydesdale of similar size I have found tire air volume to be the critical factor for comfort and for avoiding wheel problems. My BG RNR fits 700x47 Schwalbe Marathon XR tires a size I have been using for years without wheel problems including the Divide Ride.

This size also gives me the choice of bike route on and off pavement at the time I encounter them on tour. I like having such options instead of those dictated by smaller narrower tires on the bike. The tires roll fast enough on pavement for my touring needs and off pavement as well.
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Old 11-30-09, 01:16 PM   #6
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I travel with a similar load (less gear and more me...) on my Jamis Aurora with stock 700x32 Vittoria Rando's without problems.

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Old 11-30-09, 06:41 PM   #7
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I like this chart:

http://www.rivbike.com/assets/full/0...ick_a_tire.pdf
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Old 12-01-09, 12:33 AM   #8
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Quote:
Originally Posted by arctos View Post
. My BG RNR fits 700x47 Schwalbe Marathon XR tires a size I have been using for years without wheel problems including the Divide Ride.
You sure those aren't 37s?

Quote:
Originally Posted by markf View Post
Options regarding tire size: Schwalbe makes 700C (622mm rim diameter) touring tires as wide as 50 mm.
which model is that?
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Old 12-01-09, 12:49 AM   #9
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Quote:
Originally Posted by cyclotoine View Post
You sure those aren't 37s?
The Schwalbe Marathon XR I use IS a 47mm. It was unfortunately recently eliminated from the Schwalbe line with only a 42mm and a 50mm offered. That creates a problem for me as I cannot fit the 50 mm and I consider the 42 mm too narrow for my purposes. Fortunately I have a few spares.
The Schwalbe tire lines have recently been renamed in part so I do not know which is which at this point.
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Old 12-01-09, 01:09 AM   #10
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Quote:
Originally Posted by arctos View Post
The Schwalbe Marathon XR I use IS a 47mm. It was unfortunately recently eliminated from the Schwalbe line with only a 42mm and a 50mm offered. That creates a problem for me as I cannot fit the 50 mm and I consider the 42 mm too narrow for my purposes. Fortunately I have a few spares.
The Schwalbe tire lines have recently been renamed in part so I do not know which is which at this point.
i had no idea there was anything larger than the 42 available. I cannot find the 50 anywhere.
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Old 12-01-09, 06:24 AM   #11
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Great chart, thanks for posting it!
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Old 12-01-09, 06:40 AM   #12
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Originally Posted by markf View Post
I suspect that the folks at Co-Motion thought things over pretty carefully before they spec'ed the tires for your bike, and I would be careful about trying to second guess them.
GREAT discussion...very helpful. Looks like markf is right about Co-Motion thinking things over. The 35's stay.
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Old 12-01-09, 09:33 AM   #13
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Several versions of the Marathon touring tire come in 622-50:
http://www.schwalbetires.com/node/37
http://www.schwalbetires.com/node/2666
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Old 12-02-09, 01:31 PM   #14
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I agree that a 35mm (or wider) rear tire is appropriate. I'd suggest going down to a 28mm or 32mm tire on the front. With your unequal weight distribution, your front tire is quite lightly loaded and you could have nearly as cushy a ride with less rolling resistance and better handling by running a narrower tire up front. I tour on the road with an all up weight of 230lbs with a similar weight distribution to yours. I use a 32mm Panaracer Ribmo on the rear and a 28mm Panaracer Tserv up front, both running at 80-90psi. Though they are of different sizes, the tires handle similarly because of the different loadings.
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