Triumphrat

RSRAT

This is a well worn subject on this site and elsewhere. However, upon request I received from Pirelli a one page document via email entitled " Pirelli Racing and Trackday Guidelines" in which they list their four tire models including the Diablo Corsa III which many sport and sport touring riders are using these days, myself included. There they mention a "suggested" 34psi in both front and rear tire and also specify that the pressure should be set once the tire is up to its operating temperature rather than being set when cold. The document also references use of a tire warmer, suggesting these be applied for 45 mins. to an hour and, I infer, reach a temperature of 165 degrees F before setting the pressures and then running on track.

I further infer from this that the entire carcass would/should be at that temperature by that point which might be different than the temperature one might get by running the tires on the track and then measuring temperature at the tread surface until seeing that same temperature.

In any case, for purposes of translating all this to real world use for those who want to ride canyons and occasional track days, I'd presume that with a temperature measuring device, one could establish when one's tires reached the 165 degree thresh hold and then establish the 34 psi setting, thereafter riding with the assurance that you've gotten your tire reasonably close to the optimum inflation pressure for best traction/handling performance, generally speaking. From there of course you'd be on your own to vary the setting based on feel, suspension set up, rider weight, ambient and track temperature, and any number of other variables.

I'm not aware whether any other manufacturers publish this kind of information for their tires but perhaps at the performance end of the spectrum, this approach would also apply to others.

So, I'm curious to know what others here think about this approach to setting pressures and whether they've used it themselves and, if so, what results they have to report?

I'm also curious to know what type of temperature sensor might be best to use, especially if you have no tire warmers and just want to "fudge" it by warming them up on track first and then setting them. I've seen an infrared, penlight style thermometer that might be a good tool for this, but again, have no idea personally, if you'd be getting the same result when measuring that way vs. using tire warmers, etc.

Curious to know what others have found in their experience?

andyw

I cant really comment on other peoples tire setups, but what pirelli say is pretty much how I was taught incl how to do a lot of the manual calculations.

DaveM

RSRAT,
I am not a track day bunny and that is totally different to road riding as you would agree for obvious reasons.

I do not agree with set tyre pressures for "everybody".

What Pirelli will have written will be a base line only or a starting point if you will.

Everybody has a different riding style and is a different weight, like suspension set up the reason tyre pressures become a debated subject is magazines and the like keep making ridiculous articles like;

Suspension and Track day set up for '08 R1, and half the readers go all stoopid and gaga and think ooooh Bike magazine says this is the magic setup for my track day..... two clicks here a click back there etc and I am done.

Absolute BOLLUCKS!

Tyre pressures have to have an element of the personal because I am 230lbs and you might be 65lbs, I might ride like a novice and you might be a motogp rider.

One of my riding mates has been racing motorcycles for years and still does, (road racing not MX) and he would be the first person to tell you that two riders with the same bike and even the same weight will have different suspension set ups and tyre pressures may also differ slightly.

Not being much of a tech head but also being a very experienced road rider I use "the seat of the pants method". That is not to say there is anything at all wrong about doing things the tech route.

I ride hard at a pressure then see what the tyre look like, I reduce the pressure until the tyre is visibly working, if I am melting it to shreds (unless it is a race tyre) I adjust the pressure up a bit.

Most vehilce manuals state a too high pressure because of legal claims against them if people under inflate.

For my Sprint solo with Pilot Powers on I use 33 front &nd 36 rear
If two up on these tyres I use 34 front and 36 - 38 rear with luggage and my wife I will use 36 fnt and 40 rear.

On my Daytona 955 with Michelin Pilot race mediums I use 30 - 32 frnt and 34 - 36 rear.

Some brands do work better with higher pressures than others and Continentals are a point in case, they seem to prefer 2 - 3 psi more than either Michelin, Metzeler, Pirelli or Avon or Dunlop.

My 2 cents worth.

I am not a novice rider and I weigh 104kilos at present thats around 230lbs for you 'muricans and that is without gear.

Plenty of pics of tyres in both my albums so you can see I do work 'em.

DaveM

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RSRAT

I ride hard at a pressure then see what the tyre look like, I reduce the pressure until the tyre is visibly working, if I am melting it to shreds (unless it is a race tyre) I adjust the pressure up a bit.

thanks Dave.
so let me ask this, since it's actually something Ive often wondered about...

how does a tire look when its "visibly working"-- do you mean from the rider's perspective while riding, or looking at it whenever you're off the bike?

and... "melting"... how much or how little melting would be "right" for a road or even track tire, especially a more aggressive one like the Corsa? e.g. I find when ridden "hard" by my definition(higher corner speeds and lean angles), I see the outer portions of my rear tires and sometimes my front ones as well, showing a melted surface. sometimes that covers bands on the rears at least, up to an inch or two in width. does that mean my pressure's too low, high, just right, or what. ie, is it normal?

on my Corsa III's the rear tire wear is usually right out to the very edge of the tread where the little arrow markers are located, while the fronts are usually not that worn at the edges, but usually about 3/16" in from the edge. does that mean I still have some safe and usuable lean angle left or am I limited by the rear tire?

finally, if some melting is good or "right", then does that mean that you only have a certain number of heat-up, cool-down cycles in a tire before its worn out, even if sufficient tread seems to remain?

while I don't really think or worry about any of this much, especially when riding, I have generally wondered what these visual cues might mean and how I should use them, if at all, make adjustments, etc.

3banger

I run my Pilot Powers at the manufacturer recommended 36 & 42. I agree the grip levels would likely be higher if I used a lower pressure. I used 32 & 32 back when I was doing track days on my RS. I wear my rear just about edge to edge on the Powers, (I can't quite ride my self of the little Michelin Men) and I don't have any issues with grip. So I stick with 36 & 42 for tire longevity. What would be the gain of running lower pressure? Does it really effect wear rates? Is there a handling benefit to a slightly more compliant tire carcuss?

DaveM

3banger,

tyre pressure drastically alters tyre wear.

It also makes a huge difference to grip.

For a Sprint 36 & 42 is too high for solo riding unless you are a very large person or two up with full luggage.

What would you do to your tyre pressures when you carry a pillion and luggage if your tyres are already inflated to there max rated pressure?

You don't do that on a car or a trailer or a semi?

You increase the pressure with increased load but not beyond the max rated pressure which in this case is 36 fnt & 42 rear.

If you read the side walls of almost all sports and sports touring tyres what is listed as the MAX pressure is 36 & 42psi.

I have said this so many times I sound like broken record MAX pressure is for MAX load.

If you are not carrying a pillion and loaded luggage then you should not run the max pressures.

You can quote the manual all day long but it is commonly accepted in the vehicle industry that manufacturers always state pressures on the high side for obvious reasons.


36 & 42 is too high for a Sprint with Solo rider for Pilot Powers unless you are a very heavy person.

I am a big guy at 230 lbs and at 33 & 36 my tyres are getting to working temp when I work the bike hard in the mountains.
Ask steventhechef, welshrob or iceman even my fronts do not have chicken strips.


DaveM

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DaveM

To me riding is a very hands on, feel everything experience, so I think the short answer is yes, but you probably need someone that knows a lot more than I do about all of this like a racer or track day instructor.

I would hate to say something and someone said "DaveM says you can do this" and then they crash.

If you ride fast then the state of your tyres, the pressure, road temp, suspension setup all have a very big effect on what you can and cannot do on your bike.

How much tyre you have left is up to you and how far you want to go but you have to be very aware that grip and lean angles are not unlimited even though I think most bikes and tyres these days can out handle the rider.

I hope that is not more confusion.

Cheers,
DaveM

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Low Rider

O.K., if you are riding solo on your ST; let's say a 2006 model (with Pilot Powers)and are carrying a rain suit some water etc. in the Pannier's, and, your 230lbs; what would be the best psi for performance and handling...

dolson

Low Rider, Being a newbie if you were to read the entire thread you would find out that tire pressures are individual and dependent entirely on ones own specific conditions. The only constant is that the the ressures listed on the tires are MAXIMUM PRESSURES AT MAXIMUM LOAD. Look in your owner's manual and under specifications you should find the maximum bike weight. Find a scale, (they are everywhere) and weight your bike at it's normal load and go from there. TP is also dependent on ones own particular suspension setup.
The best way to adjust TP is to find the manufacturer's listing for that tire's operating temperture, get an IR tempureture guage,(They are cheep) and adjust TP acording to the temps you are getting in your normal riding.

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dolson

42 would be the MAXIMUM pressure at MAXIMUM all up weight as DaveM has said. Running the max when not necessary leads to several undesirable things.
1. The tire won't come up to temp properly
2. There is less grip both front and back and the front will have a higher tendency to push and the rear to skip out especially with uneven and dirty road conditions.
3. The above is true especially in wet conditions.
4. One will not get longer tire life at unnecessarily high tire pressures. The rear especially because it will be running at a very narrow patch = less friction and higher wear rate because the wear patch is localized to a smaller area. This wears out the center and squares off the tire wearing it out sooner.
5. ride will be unnecessarily harsh.

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