badly worn tyres

[mig]

do they drag more?

a change at weekend from an old continental 'cyclocross' tyre at the rear of my winter commuter to a new example of the same feels so much less effort and far quicker in the real world. it's a fixed bike so i'm always comparing in the same setup otherwise.

psychological? or is the flattened profile of the cover on the worn unit actually dragging more?

[Nearholmer]

Greater drag on the worn tyre seems a bit unlikely to me, in that my personal experience of riding CX tyres on tarmac is that they are truly horrible, lots of resistance, until the knobbles are worn away in the middle, and even then still horrible because fast cornering involves the leftover knobbles at the side.

[Brucey]

because there is less 'tread squirm', worn tyres usually roll easier than new ones. The commonest reason for this not to be the case is if the carcass has sustained some damage. Maybe it is the sap rising?

[plancashire]

Sometimes old worn tyres also have old crumbly rubber instead of the harder stuff when they were new. I suspect hysteresis losses in this old rubber would be higher.

[Cyclothesist]

They certainly puncture way more readily which really is a drag.
I'll get my coat

[mig]

because there is less 'tread squirm', worn tyres usually roll easier than new ones. The commonest reason for this not to be the case is if the carcass has sustained some damage. Maybe it is the sap rising?

yes, it's odd, i thought i'd find that the new tyres would be noticeably 'odd' feeling with the new tread. as mentioned up thread they aren't the best idea for the road but were the correct size for the rim and frame and given free so i thought i'd use them for short, winter distances. there isn't any real damage to the old carcass so all i can attribute it to is psychology or possibly the worn one has a much wider contact patch as the profile is so 'square.' any sort of mild cornering would tip it over from the worn area to a noticeable shoulder so that wouldn't help.

hopefully the weather will pick up properly soon and the bike can be serviced then returned to the shed in favour of lighter kit. sap rising? hmmm...the sap was freezing this morning squire!