Rain's affect on tt speed?

whoawhoa said:

Hey, you guys think that fairly heavy rain (and standing water on the road) could have an affect on speed? (in addition to turning, etc, of course) I'm looking for justification after a strange performance this weekend, so you better say yes!😄

High humidity has the effect of lowering air density which means less aero drag. Don't know if it's negated by other effects.

Interesting question. All the studies I have seen on rolling resistance have been on dry pavement. Actually, if anybody knows of any studies of rolling resistance of different tires in the wet I'd appreciate a link. I'm compiling all the data I can get my hands on re. wheels and tires. BTW, what tires were you running?

beerco said:

High humidity has the effect of lowering air density which means less aero drag. Don't know if it's negated by other effects.

I was comparing myself to other riders on the same day who raced just after the rain, so I assume they also had the benefits of high humidity.

BTW, I was assuming that the scientific term for "smashing through raindrops with your body" would be what caused a loss in speed, all else being equal. The temps rose throughout the day as well so I know that had an impact.

RapDaddyo said:

BTW, what tires were you running?

Maxxis courchevels

whoawhoa said:

Maxxis courchevels

Can't recall seeing any data on those tires. Here's some (recent) data on rolling resistance of some other tires.
rouesartisanales.comarticle 1503651.htmlOpen ↗
Sort of interesting that tires can more than offset the gains of aerodynamic wheels. Also haven't seen any data on rolling resistance in the wet.

Hell, yes, water on the road will slow you up, to say nothing of actual puddles. It creates rolling resistance and adds weight to the tires. And think of the water that's being thrown off the tires - that energy's coming from somewhere, and you're the only energy source in the vicinity.

The rain itself won't really have much effect (unless there are puddles) but the fact that the humidity is 100% will make it more difficult to produce power. I have a detailed log kept of my training and my average speed takes a nosedive when it is drizzling or raining lightly or high humidity. Basically, your sweat can't evaporate and you overheat.

-Bikeguy

Pendejo said:

Hell, yes, water on the road will slow you up, to say nothing of actual puddles. It creates rolling resistance and adds weight to the tires. And think of the water that's being thrown off the tires - that energy's coming from somewhere, and you're the only energy source in the vicinity.

It is well accepted that gas mileage is poorer in the rain due at least in part to increased rolling resistance...which is caused by the tires being forced to displace the water on the road... bike tires are quite a bit narrower with a much smaller contact patch, but I imagine the effect is still there to some extent. Never thought about the water flinging energy effect, but I guess that would be true as well. For me it is more about having my size 48 shoes soaked with what feels like 5 lbs of water that makes me feel slower.