thewalrus

I was browsing around the photos at Ondrej Sosenka's site, and I noticed there's many shots of riders on full road bikes riding on european velodromes... Bikes with brakes, gears, etc. Doesn't this introduce debris and dirt onto the track?

https://www.sosenka.cz/fotogalerie.html

11.4

They are often ridden on trainers/rollers or in the warm-up circle in the track infield. A winning rider who has not just finished an event may grab his/her road frame for a celebratory lap and photo opportunities. That's why you do see them on the track from time to time. And they don't get that much on the track. Even an indoor wooden track gets bird droppings from the rafters, various kinds of litter, oil from track chains, perspiration, etc., so bike tires aren't going to add all that much. A rider won't come right off a wet or muddy road directly onto the track anyway.