Handling woes

[GuzziMoto]

It works fine for me. And many others still use it too. It is a very simple concept. As the tyre(and the air inside) heats up the air tries to expand. That causes an increase in pressure that you can measure with a pressure gauge. The larger the increase, the more heat. If you have a pyrometer, that works better, more accurate. But few people have that and most have a pressure gauge. It is only a ball park test, but it works well enough for racing where tyre temp is more critical them it is street riding. Tyres have an optimum operating temp range and the pressure you run in them plays a large part in the temp the tyres run at in use. 10% increase is fine if you want your tyres to run a bit cooler. We always use 15% for street and 15-20% for racing, depending on the track and other factors.

[dlaing]

A good way of checking your tyre pressure to see if you are properly inflating your tyres is to check them cold then go for a typical ride. Then check them hot. The pressure should go up approx 15% from cold to hot. Not enough increase means your pressure was too high to start with and too much increase means the pressure was too low.

The bit about higher pressure in the rain comes from the days of bias-ply tyres. Increasing the air pressure would expand the tyre and open up the grooves in the tyre to help water escape from the contact patch. The one flaw that you had to consider was that running higher pressure would make the tyre run cooler. You had to decide what was more important, water evacuation or heat in the rubber. Todays radial tyres have a more stabile contact patch that is less effected by inflation pressure. The grooves in the tyre do not close down like the grooves in a bias-ply tyre did.

 

Thanks Guys! I had talked to a Pirelli rep and he recommended that method. But I could not recall what percentage he said to use. I thought he said ten percent, which considering we were strictly discussing tire mileage, was probably what he said.

In SoCal heat is a big factor for tire life which might explain why Ratchet would recommend ten percent.

I'll have to give that method a try again.

I suppose one draw back of the method is that the flexing factor must change with the life of the tire. Towards the end of its life it should need more pressure to keep cool. And there are probably other variables. Still it is a good test.

[dlaing]

I just took a look at the PDF brochure at Metzler and noticed they have recommended maximum AND Minimum tire pressures.

For example with the M3 M1 Z6 and maybe all their tires that fit our bike, they list 32/42 for the front and 36/42 for the rear.

And somewhat surprisingly, they say:

Finally, running air pressures near the maximum as listed on the sidewall

of the tires will reward the consumer with higher mileage and increased

overall satisfaction with our product.

To get the maximum upgrade benefits of using Mtetzeler tires, always

run the recommeded air pressures that can be found on pages 7, 22 and

as suggested in the Fitment Chart for your specific motorcycle on pages

28-47.

[guzzipete]

Their numbers are in the ball park.

This ain't the space shuttle.

 

Actually, manufacturers put a fair amount of engineering nous into determining tyre specifications. The manufacturers recommended pressures are designed to make the tyre contact patch as large and evenly weighted as possible, whilst also providing steering/handling, wear, and fuel economy characteristics that will please the greatest number of customers. Over inflating the tyres will feel like the handling and grip is sharper because at low cornering forces there is less steering weight. However, ultimate grip, which depends on maximising the contact patch in strong braking or lateral G situations will be reduced. i.e. ultimate braking and cornering grip will suffer, even if it doesn't feel that way. As an extreme example, look at how sensitive F1 cars are to tyre pressure (where a variation of just 0.2 kg/cm2 can “ruin” the performance of the car) to understand the effect on grip.