big chainring

I was in the 28mm road tire camp for a while. Recently switched to a 21mm tire and my performance is up. On my regular 7 mile loop I clocked a 1mph increase just by changing the tires. Everything else was unchanged. Acceleration is improved coming out if corners and up steep climbs. Saying so long to wider tires.

redfooj

much scientific. very convincing. wow.

gregf83 

Lots of variability in the rolling resistance of 28mm tires. You could save 10-20W just from one tire manuf to another while staying at the same width. Going from underinflated, crappy 28mm tires to decent, high pressure 21mm tires could result in a 1mph improvement but your ride will be harsh unless you're riding on smooth roads.

f4rrest

21 sounds really narrow.

What pressures do you run 21s and 27s?

Sy Reene

not sure I see the point even considering tire width, all for a 7 mile loop.

big chainring

I'm thinking also it could be that the narrow tire is the perfect choice for my English TT bike. Works with the geometry as it was intended. No harsh ride even in the cobbled section of my proving ground.

The 7 mile loop is my proving grounds. I test my fit, any alteratiins to the bike, etc.

I dont know what the tire inflation is. I go by thumb pressure and ping the tires with a flick of my finger. A nice high pitch ping and just a bit if tire deflection with my thumb and its good to go.

wphamilton

Which 28 and which 21 tires? @gregf83 says that the construction of the tire can make more difference than the size, so it's a good thing to take into account.

WhyFi

Oh, so you *did* take pains to isolate all other variables besides tire width. Very well, carry on.

FeltF2Tarmac

TimothyH

Weight changed, not just width.


-Tim-

mcours2006

All else can't be equal. Too many variables. The 21's may very well be faster than the 28's. But maybe you just felt better and pushed that much harder.

Lazyass

After going for the bigger tire fad I have gone back to favoring narrower ones. I'm not really faster but I just like how the bike feels with them. I don't know if I could make any kind of real avg speed comparison on a 7 mile route. That's barely a warm up, hardly worth getting dressed for. What, do you start hammering as soon as you roll?

wphamilton

Eh, if that's what you ride - the short TT loop - the speed of that ride is what matters. I'd want to see it repeated at least half a dozen times before drawing a conclusion, but one time feeling good and going faster is also good. Something about new tires, especially if they're lighter and better quality, always feels like a new ride to me and I get OP's enthusiasm.

Wheever

Sy Reene

It is funny how many people seem to get enthusiastic about performance gains that are solely attributed to an equipment choice. Then again, perhaps those that are the most enthusiastic are actually racers where time = money.

f4rrest

Money doesn't motivate us on a bike.

Very few are paid to ride... or race for that matter.

big chainring

Well just back from a ride. I timed myself for a flying kilo. Did a 1:10 with the 21s. They are Continental triathalon 250's. Best I did previously on the 28s, Schwalbe One's, was a 1:14.

Similar wheels. The Schwalbes are mounted on Mavic SSC rims and Campy small flange hubs. The Continentals on Mavic Monthlery rims Campy high flange hubs.

gettingold

My thoughts exactly.

ThermionicScott 

Wish I had roads nice enough for 21s!

Kontact

I don't know if it would affect your results either way, but you should have very different pressures in a 28 and a 21 as the ideal is based on tire volume and rider weight. It sounds like you have them filled to similar pressures.

This chart is by weight per wheel, so you take rider and bike weight then split it 45/55 front and rear.




As you'll note, the difference in optimal pressures for a 21 and 28 are something like 45 psi. You almost certainly have one or both of your tire pressures way off of optimal if they 'ping' the same. It wouldn't surprise me if the 28s are slow for you because you have them much over-inflated.

DrIsotope

Twenty ones, you say? I wouldn't make it to the end of my street, much less out of my neighborhood. The cracks would just swallow me up. 700x25 is the minimum to survive out here. And when I ride my CX bike on tubeless 700x35s, my whole upper body is a lot less sore at the end of the day. Hysteresis is an everyday reality here, and if going to a 700x21 tire meant I would be 1mph faster over 80 miles, I still wouldn't do it. Over seven miles? Anybody can be comfortable on any tire for 20 minutes. Do a century on those things and let us know how that turns out.

shoota 

Which power meter are you using?

Kontact

Is that necessary to make sure he didn't have a tail wind on the entire loop?

shoota 

No but it is necessary to make sure he wasn't putting down more power on one ride vs. another.

noodle soup

+1

The wind conditions could also change direction during the ride.