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i just went from a spec. crossroads ex 1.95 semi-slick to a maxxis hookworm 2.5 (with a 480g tube) and i'm not noticing much difference at all, on the road and on doubletrack. haven't taken it on any 'trails' yet, though. so, how do you measure rolling resistance?
 

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Rolling resistance is a slippery....

critter. Tires that you think would roll like you were riding through mud can actaully roll better than tires you'd think would roll very well. I've discovered over the years that rolling resistance is not as dependant on weight or width, but more on tread design than anything else. So consider the crossroads and the hookworm. The crossroads has a heavier tread pattern than the hookworm. The hookworm has almost no tread at all. So even though they are considerably wider and probably heavier, rolling resistance is likely to be comparable on pavement. Where you'll notice it a bit more is in dirt, and on longer rides where the heavier weight of the hookworm will tell. Also people tend to confuse rolling resistance with pedaling effort, although they are related, they are not the same. Rolling resistance has to do with how well the tire rolls. The easiest way to compare them is to find a hill that transitions to flat at the bottom. Then roll down that hill on one set of tires without pedaling and let the bike just roll until it stops. Mark that spot and switch tires then roll it again. Mark the second stop point and compare. The tire you went furthest on has less rolling resistance. There are other factors that affect this little test so it's not exact or definitive. A heavier tire will have more momentum and therefore likely roll a bit further, tire pressure, tread design, etc. And a little fact that is counterintuative is that often a wider tire will roll better than a narrower tire. The wider tire tends to flow over small obsticals rather than bumping over them. So they actually roll better over things like expansion joints in pavement, cracks, small rocks etc.

Pedaling resistance has more to do with weight and has to do with which tire is easier to accelerate and keep moving. Things that affect pedaling resistance are weight, tread design, etc. Notice that they are the same factors that have an affect on rolling resistance. And rolling resistance has a direct affect on pedaling resistance. A tire that rolls slower or harder than a nice fast rolling tire will take more pedaling effort to keep it rolling on the part of the rider.

So pedaling resistance and rolling resistance while closely related refer to different aspects of the dynamics of a tire. The bottom line is, I've had 1000g tires that roll like crazy in the first test, but when it comes to pedaling are ALOT tougher to keep going than a 550g tire with a more agressive tread that didn't roll as well as the 1000g tire in the first test.

What you've got is a tire that rolls at least as well as your previous tire. But likely will take more effort to keep going over distances and will be a bit slower to accelerate. This of course is all highly simplified, but is likely the reason that you don't feel that much different in most conditions so far.

Good Dirt
 

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All things being equal except width, the wider tire will have less rolling resistance. The area of the contact patch is based on the tire PSI. A wider tire will have a wider contact patch. Because the area is the same, that means the wirer tire also has a shorter contact patch length at the same PSI. The shorter contact patch length means the tire bends less as it rolls around, and that reduces rolling resistance.
 
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