Hot Tyres and Pressures

Motorcycling
1

This is an extract from a few emails from my mates…2 questions

  1. Are tyres meant to be hot to the touch?

  2. Are tyre pressures and guages affected by altitude, and how do you adjust if they are?

Any answers?

The extract…

I just got back from a quick trip to Thonon on the bike and decided it was time to lube the chain. So I stuck the bike on the centre stand and started spraying, only to find the back tyre was crazy hot - maybe not enough to scald your hand but still bloody hot enough to require putting my gloves on to continue to turn the wheel/chain. I guess the tyre pressure might be low - even though they sort of look OK - its at least a couple of weeks since I last checked the tyre pressures so just in case I will make sure I check the pressures first thing tommorrow when they should be stone cold.

Anyway is this normal? - I have never noticed my tyres ever get more than slightly warm before now?

Reply

Yes - wait until you figure out how to use brakes then check out the discs ¬!

Hot tyres are caused by

  1. low pressures

  2. Enthusiastic driving

If you have hot tyres (as in hot to the touch) & brakes that will burn you I would say that’s normal.

Tyre pressures are really important & should be checked cold, however be aware that you can ‘tune’ your tyre pressures to your style of riding. In Winter, (ie cold) if your tyres are normal pressure it will take a certain amount of time to get them warm & so work effectively.

By dropping your pressures (max 5 psi as you just don’t ride hard enough to drop lower than that) it will create more friction & so get the rubber up to temp faster.

A good tip is that after a run your tyres should be the same temp & feel the same. But you have too check this immediately you get off the bike.

Reply

Thanks I’ll check what the tyre feel like after my next longish run.

Pressures were bang on this morning indeed the rear was 2lbs high so I let some out. I also checked them both thoroughly and there is no sign of any damage or abnormal wear. Looks like the scrub marks seem to extend slightly further up the sidewall on one side of the rear tyre than the other but again its only marginal.

Its weird if hot tyres are normal I am surprised I have never spotted it before. I must admit I normally find time for a cup of tea before attempting to lube the chain after a longish run so maybe it always had time to cool a bit.

One question I had was how do pressure gauges in a footpump work? and are they affected by altitude? I know things like eggs take loads longer to warm up when cooked here because of the altitude and wonder if I need to adjust my target tyre pressures because I am so high up? If so, which way would I need to adjust the pressures?

Anyway for now things seem Ok with the bike so I guess I’ll just keep riding whilst the weather is OK - although it was cold enough yesterday to need my winter gloves.

2

If a tyre is too hot to touch then don’t ride the bike, get the tyre and bike checked as that’s not right. Even on a track day in Spain when the tyre is getting a pounding it won’t get too hot to touch.

Don’t rely on the foot pump gauge, they are useless, get a proper tyre pressure gauge, even from Halfords they’re less than £20 for a reasonable one. Try to get a digital gauge, easier to read.

Ambient temperature and altitude will affect the tyre pressure and temperature so on a touring holiday be prepared to adjust the pressure as necessary.

3

How do you adjust the pressures to take the altitude into consideration?

4

There is probably a set of equations you could memorise and take a scientific calculator with you but if your maths is anything like mine, I’d take a tyre pressure gauge with you and adjust them as you ride :slight_smile:

Having said that, unless you plan riding up the side of K2 I can’t imagine the difference in air pressure will make that much of a difference. I didn’t adjust the pressures when I rode up to Andorra from France, just checked them each morning and set as per the manual.

If it was flat enough to get too hot to touch then the rider ought to have noticed and the tyre is probably damaged too by now. I wouldn’t want to ride on it.

5

Can’t be ar*ed to answer the altitude/pressure/gauges question, it’s just too complicated, but temperatures…

Loads of variables here but assuming the tyre is in good condition, correctly inflate, the right tyres for the bike, brakes aren’t binding and so on, 80 degrees C is not uncommon though about 60-70C is more likely.

GP car tyres don’t start to work properly under 60C, hit best performance at 70-80C but can often get to 90C.

If it’s damned hot to touch and it’s a sports tyre on a sports/sports touring bike and just done a decent run, it’s working just fine and doing what it was designed to do. Grip.

Of course you don’t get nothing for free. The wear rate is going to be interesting.

6

tyre warmers work to 80degC to have the tyres to go out on track. its unlikely he’d have achieved track temps on the road but they tyres should get hot. if you use wets on track you’ll actually see steam coming off them.

i’ve burnt myself on the front brake discs before putting warmers on after a track sesh, so yep, they get hot. Rims will get warm but not excessively so.

its just not that normal to get off the bike and stick you hand on your tyre

in terms of alt, I’d say tyre pressures yes, a good guage no. unless the tyres are filled with nitrogen only :wink:

7

Just for my own soul, I did a bit of poking around on the tyre pressures/altitude/guages thing…

…and found it lots of contradictions.

The best bit of info. gleaned was roughly “if your on the top of Everest, do the sums, if your not, don’t bother”. I do say roughly.

Apparently there are gauges with built in altimeters that do the sums for you but I’m damned if I can find them, and does it matter that much?

The bike/tyre manufacturers figures are guidance. The proof is in the riding and a couple of pounds/0.2 bar either way is pretty negligable.

8

Thank you everyone