Deflating tyres?

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 :wink: anyone actually know what the reasons are, or if they are just convention, superstition, etc?

I reckon it’s a load of tripe.
But I’m willing to be convinced otherwise. :slight_smile:

My thinking is that each inflation/deflation cycle will put additional pressure on the tyre/rim, compared to leaving it as-is.

Makes sense for high pressure tubulars, If you are running them at 150+psi for very light tyres the risk of exploding them is increased if they rub against anything.

Not relevant at this time of year but highly inflated tyres and hot cars are also an explosive mix!

Crock of shit

I can only see this being good for really cheap tyres so the sidewalls aren’t under immense pressure, or for not riding for long periods of time.

My thinking is that each inflation/deflation cycle will put additional pressure on the tyre/rim, compared to leaving it as-is.

Hmm. Not too sure about this.

If you put a glass on a bench, then pick up and put down the glass 10,000 times, will it break the glass?*

Surely the only thing it would be doing is work-hardening the rim alloy. I’ve seen a lot of old dudes do it, so it must be right.

*the only simile i could think of

could it be to do with the glues that they used to use, which might not have been very flexible, or couldn’t be left under stress for long periods of time or something?

I heard something along these lines a few years ago from a LBS owner, he said it has something to do with the valve. Leaving it inflated at track pressure constantly may do damage or something…?

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.

Thanks LittleWheelsandBig for the insightful information :slight_smile:
I think you have explained the theory well.

riight… good infos, thanks!

On a related note: I found a splinter of wood in the sidewall of my rear tyre tonight. It had punctured the tube :confused: I’m 98% sure it happened on the bike’s way in or out of the car boot.

Whateva - I’ll be slightly deflating from now on, tubs or clinchers.