The other night, one of the older guys advised us to let the air out of our tyres before going home… Seems like a good thing to do I guess, but why?
Does anyone know of a reason why you should or should not deflate your track tyres between rides?
I know of at least one reason whjy you should deflate high pressure clinchers… but yeah (and LWAB I’m looking your way anyone actually know what the reasons are, or if they are just convention, superstition, etc?
As I understand it, it is due to the high pressure of the tyres.
The side walls are usually quite thin, and therefore it doesn’t take too much to make them go
I usually let mine back down to close to 100.
It comes from the old days with silk and cotton competition tubulars.
110-200 gram tubulars have a very small safety margin at riding pressures (120 to 160+ psi), the material is working very hard to keep everything together. Abrasion has already been mentioned. Together with creep, both in adhesives (between threads and between casing and tread) and in the threads themselves, tubulars tended to go ‘lumpy’ or pop when left inflated for long periods.
With lightweight HPs, some of the same things apply, although modern materials usually handle things a little better and there is more material involved in the tyre/tube combination anyway. Japanese HPs are generally rated at half of the blow-off pressure (on a standard rim, not sure about European tyres), so they aren’t working so hard at normal inflation pressures.
None of this applies to training weight tyres or tubs. There is enough material to resist the (comparatively low 100-120 psi) rated pressure long-term without too many hassles.
There is a theoretical reason not to drop tyre pressures for HPs, the tyre bead retention sections of aluminium rims will fatigue from repeated tyre pressure changes. In reality this isn’t a problem, given that the rims are designed to resist brake pressure.
Being an old dude, I followed lats advice for HPs and dropped my competition tubs to about 50 psi (both road and track) at the end of a meet. If you are running lightweight tubs, use covers for transport. Blowing a $150+ tub in the boot of your car after one race isn’t fun.