Cyrox = a shit and dangerous tyre

[p.dath]

Sounds a little "back to front" to me? Less pressure should = more heat.

The tyre is designed to run at an ultimate level of pressure to get the right shape. The manufacturer has to estimate how hot the tyre is going to get, subtract off that estimate, and that becomes the recommended cold tyre pressure.

A street tyre on the track is going to get much hotter, and would end up being over inflated. Hence the need to deflate the tyre before you begin, so it runs at the correct inflated hot pressure.

Deflating a street tyre for use on the street indicates you think the manufacturer has miscalculated the running pressure and expected heat. Possible, but in this case we were only talking about 60km/h zones. Not really much possibility to develop a lot of heat.
So sure, the under-inflated tyre may heat more rapidly, but probably wont get to the correct operating pressure as it will never get hot enough.


I'm not a tyre expert, but the manufacturer who designed my tyre is, so personally I'll stick to using the recommended pressure on the street.

[MSTRS:Me]

Rule of thumb is a 10% increase in pressure from cold to hot. If you are getting less than 10% then your cold pressure is too high. And vice versa.
More heat tends to mean more grip, and I believe that is the reason for dropping pressures for track use. The trade-off is your tyre/s wear noticeably on the track.
Manufacturer's recommended pressures are more to do with tyre life than the best grip.

[Robert Taylor]

The other thing to consider is riding on wet roads, the tyre pressure has to be high enough to keep the rain grooves as clear and as functional as possible.

[Owl]

So sure, the under-inflated tyre may heat more rapidly, but probably wont get to the correct operating pressure as it will never get hot enough.

Don't take my word for it and do your own experiment. Run your rear tyre with very little pressure and go for a ride. Then see for yourself which tyre gets hotter!

[Neshi]

not sure you understand what he's saying.. You could let the bike run on nothing but rubber, and that would get hot as hell.. doesn't mean it will get the right amount of pressure in the tire now will it?

there is the combination between the volume of air that goes into the tire + the heat of the rubber (and thus the air inside, which expands) = tire pressure, and grip.

[Robert Taylor]

not sure you understand what he's saying.. You could let the bike run on nothing but rubber, and that would get hot as hell.. doesn't mean it will get the right amount of pressure in the tire now will it?

there is the combination between the volume of air that goes into the tire + the heat of the rubber (and thus the air inside, which expands) = tire pressure, and grip.

In road racing we play with pressure all the time to manipulate tyre temperature and grip. If ( within sensible limits ) the tyre pressure is lower the tyre is more ''busy'' flexing and distorting under acceleartion and bump inputs etc. That raises core temperature. During winter racing we will also very often go to FIRMER springing and valving calibration to work the tyre even harder to get some more temperature into it. Lower temps equal less grip

[t3mp0r4ry nzr]

brings back good memories of sliding the MC22. Fun tyre!

[motorbyclist]

So sure, the under-inflated tyre may heat more rapidly, but probably wont get to the correct operating pressure as it will never get hot enough.

I'm not a tyre expert, but the manufacturer who designed my tyre is, so personally I'll stick to using the recommended pressure on the street.

good call running recommended for street use but can you find a source for this theory you've got about tyre pressure? I'd like to have a read as it's the first i've heard it about despite track days and years riding.... and robert isn't correcting it so I won't rip into it...

It's just that an underinflated tyre will heat until pressure raises enough to reduce the heating enough to reach a steady state. A tyre that is flat or severely under-inflated simply overheats before reaching the desired pressure

my experience/learning/understanding has been that for road tyres, low pressure means more bending, thus heat, which gives a hotter tyre faster to help it better stick to the road sooner. Conversly, low pressure means more rolling resistance and increasingly undesirable handling as the tyre moves under you and the round profile is deformed. Pressure too high or too low can both be detrimental to tyre life, and as the tyre heats, so does the air and thus pressure (thus the pressures quoted are for "cold" tyres to ensure the correct profile and balance of tyre life, traction and fuel efficiency.

Tyres warm, lower pressures to bring heat into them, fairly good weather, going around a smooth well surfaced bend at about 60kmh, not turning fast at all, absolutely nothing special with the lean angle... rear end just starts coming around drifting. A real in helmet 'woah shit!' moment..

did you go back and look for diesel or other friction modifiers you may have missed? hard on the gas? what state is the suspension like?

I'm just saying this because I see/hear a lot of "oh that product is shit" based on an individuals sole experience where there hasn't been any effort on their part to see why the product might be failing or if others have had the same problems. Often the individual was either "doing it wrong" or using the product outside it's operating parameters; you wouldn't run a nylon shinko on a gixxer750 and expect strong performance, but many adventure riders swear by them for their (alledged) combination of wet and dry performance and long life....

but really, if you're using even half of a 750 you need to have decent tyres that are of a known age/condition. When I bought my rvf, the bt95 on the rear was an absolute shocker but should otherwise have been a suitable tyre (and since fitting new tyres things have been good, and correctly setting the rear preload helped further)

[p.dath]

good call running recommended for street use but can you find a source for this theory you've got about tyre pressure? I'd like to have a read as it's the first i've heard it about despite track days and years riding.... and robert isn't correcting it so I won't rip into it...

It would be safe to say your knowledge would exceed mine.

My presumption is that the tyre has an ideal shape when being used. My presumption is that the manufacturer goes to a lot of trouble when designing the tyre, it's curvature, how it deforms under pressure, etc.

And my presumption is that the shape of the tyre is greatly affected by the pressure inside of that tyre.

I could be wrong ...

[racefactory]

Sorry to cause a big stir up fellas!!!

Just had another drift today and had a good think about it, thought hmm that rear tyre is a bit on the skinny side isn't it? Did some reading and result- found out someone has put a 140/70 on instead of the 160/60 like it should be!!!

Interesting read from your posts anyhoo!

Yes I went back to check the road the first time i realized something wasn't right.

Sorry to Mr Bridgestone as well. I still swear by your bt090!

[motorbyclist]

Did some reading and result- found out someone has put a 140/70 on instead of the 160/60 like it should be!!!

this is a gsxr750 right?

160 still seems too skinny... should be a 180 isn't it? is it from this decade or the 80's? an older classic model would make sense at those sizes.... nice.

[motorbyclist]

It would be safe to say your knowledge would exceed mine.

My presumption is that the tyre has an ideal shape when being used. My presumption is that the manufacturer goes to a lot of trouble when designing the tyre, it's curvature, how it deforms under pressure, etc.

And my presumption is that the shape of the tyre is greatly affected by the pressure inside of that tyre.

I could be wrong ...

unfortunately the manufacturer can only spec the available tyre size to best work with their machine for their set of requirements - thus those who have a different performance target (ie racers) changes to pressure and even profile can be made. Provided the user is actually taking a responsible and reasoned approach (ie safe and scientific) I'd say that the good advice from the racing/riding community shouldn't be ignored... of course i've also heard some wild theories in the past that don't seem to based on anything but wild conjecture

can't go far from wrong following what the manufacturer manual says though

[pc220]

good call running recommended for street use but can you find a source for this theory you've got about tyre pressure? I'd like to have a read as it's the first i've heard it about despite track days and years riding.... and robert isn't correcting it so I won't rip into it...

It's just that an underinflated tyre will heat until pressure raises enough to reduce the heating enough to reach a steady state. A tyre that is flat or severely under-inflated simply overheats before reaching the desired pressure

my experience/learning/understanding has been that for road tyres, low pressure means more bending, thus heat, which gives a hotter tyre faster to help it better stick to the road sooner. Conversly, low pressure means more rolling resistance and increasingly undesirable handling as the tyre moves under you and the round profile is deformed. Pressure too high or too low can both be detrimental to tyre life, and as the tyre heats, so does the air and thus pressure (thus the pressures quoted are for "cold" tyres to ensure the correct profile and balance of tyre life, traction and fuel efficiency.




did you go back and look for diesel or other friction modifiers you may have missed? hard on the gas? what state is the suspension like?

I'm just saying this because I see/hear a lot of "oh that product is shit" based on an individuals sole experience where there hasn't been any effort on their part to see why the product might be failing or if others have had the same problems. Often the individual was either "doing it wrong" or using the product outside it's operating parameters; you wouldn't run a nylon shinko on a gixxer750 and expect strong performance, but many adventure riders swear by them for their (alledged) combination of wet and dry performance and long life....

but really, if you're using even half of a 750 you need to have decent tyres that are of a known age/condition. When I bought my rvf, the bt95 on the rear was an absolute shocker but should otherwise have been a suitable tyre (and since fitting new tyres things have been good, and correctly setting the rear preload helped further)

I think this theory was introduced by pirelli. To figure out the best tyre preasure for your tyre, set your preassure when tyre is cold. Then run the tyre for an hour of normal riding/driving then re check the preasure, the warm tyre preassure should be within 5% of cold preasure. Well something like that. Was a few years ago that I was taught this so not sure of the finer details , there is a good chance i am way off the mark.

[MSTRS:Me]

I think this theory was introduced by pirelli. To figure out the best tyre preasure for your tyre, set your preassure when tyre is cold. Then run the tyre for an hour of normal riding/driving then re check the preasure, the warm tyre preassure should be within 5% of cold preasure. Well something like that. Was a few years ago that I was taught this so not sure of the finer details , there is a good chance i am way off the mark.

Correct. Almost.
About 10% increase is right. And about 15-20 minutes should be enough runtime.