tire pressure

[mike wilson]

I'm more'n open to learn a few things here about tire pressure, as I'm certainly no expert, and I reckon many 'round here might well know lots more about tires than I do!! 

 

It seems to me that tire mfgr's make recommendations on pressures based on assumptions that take into consideration a wide range of the most common riding factors under which a tire will most likely be used.  Then they come up with something that they believe will be a COMPROMISE NUMBER (or a small range) for pressure that's most likely to be the safest pressure for the largest number of riders under the widest ranges of likely conditions and uses.

 

Make eminent sense to me. A tyre company can only test a tyre on so many machines, in so many situations. After that, it's guesstimation.

 

Although there are already some sensible laws about tyre use (no scramble [sorry, motocross] tyres on the road) what bothers me is the thought of heading down the "you own X motorcycle, so you will use Y brand tyres of Z size at Q pressure" road. Seems to be on the horizon in the EU.

 

m

[Guest ratchethack]

Here it is again, why are we second guessing the manufacturers at all. What do we think they are conspiring to do that will affect the end user in a negative fashion??

Many riders here seem to favor Sport tires. Others will favor Sport/Touring tires, which are designed to include 2-up and cargo-carrying capability. I'm just suggesting that in this case, it makes sense to adjust tire pressure advisedly and accordingly if y'er NOT doing either.

 

The old method of looking for a 10% rise from cold to hot pressue is just that; the old method.....That applied to bias ply tires but not new radials.

Aha! This would explain why my numbers haven't seemed to line up on really hot days ever since my first set of radials...good thing I was only using it as a guideline, not a strict rule...

 

Thanks for the tip, Trispeed.

 

I don't think anyone would advocate adjusting tire pressures or using suspension setup as compensation for lack of riding talent. I do think it's common sense, and possibly "uncommon" wisdom at the same time, not to ignore getting the best from all your gear by having it properly matched-up and dialed-in - regardless of your skill level. It can make a HUGE difference in handling capability. Trouble is, those with the least experience and skill seem to be the ones most likely to ignore proper setup...

 

The meat wagons roll all summer long hereabouts on the best ridin' roads, shoveling up the results of irresponsibility and neglect of all kinds...it's truly a sad thing.

[Guest ratchethack]

guys... for any of you running Michelin Pilot Sports (or power)...

can anyone remind me of the tire pressure?...

I think is 34 front, 32 back for the street? (or is it the other way?)

 

just checking...i can't freak'n remember

FWIW, found a PDF on the Michelin track testing at Ladoux on the Pilot Power. Couldn't find a similar PDF on the Sport.

 

Test tire specifics:

 

120/70ZR17 on 3.5" rim @ 2.5 bar (36 lb.)

180/55ZR17 on 5.5" rim @ 2.9 bar (42 lb.)

[Baldini]

...just run it at the spec the manufacturer advises....

 

That's right. MG owners manual, P90: F 2.2/2.3 bar (32/33.5 lb), R 2.4/2.5 bar (35/36lb).

 

KB

[Baldini]

...The Dunlop  tire expert said run 36/38-40 on the road and 31ft, 29-30 rear for a track day. ...

....

 

Surely how you set up your bike depends how you ride it rather than where you ride it...????

 

KB

[staedtler]

[Guest trispeed]

yes, it matters quite a bit WHERE you ride. At the track, you ride for short bursts on smooth surfaces; the street you ride for extended periods with lots of challenging road surface, potholes, sharp edged bumps, etc.

Low track pressures allow more contact patch for a given tire and a resultant higher level of traction. Low pressure also risks overheating, lacks stability and risks rim damage from sharp edged potholes, etc. Ever notice the racer weaving down the front straight? It's not because his bike is defective, low pressures contribute to this to a significant degree.

If you run for 200 miles at a steady 100MPH on a hot day with 29 psi rear cold pressure, you risk catastrophic tire failure due to overheating.

Best to start with 42psi and have a pleasant ride, instead. If you ride slow all the time, street or track, use the standard pressure and stop worrying about it.

29psi rear is perfectly fine for a 20 minute track session, however, where you also heat the tire evenly, not just down the center like you would on the motorway.

If you are enjoying your first track day, use of the standard street pressures is recommended by all the experts. As you increase past your street thresholds, you can use a lower pressure for increased traction.

You can't ride fast enough in the turns on the street to warrant low pressure anyway. I've seen lots of guys blaze on the track with sport touring tires, too.

Those are so much better than what we raced on 15 years ago, this all seems so silly. Use the suggested presure ranges that come from the tire and bike companies.; that's it.

[Baldini]

...Use the suggested presure ranges that come from the tire and bike companies.; that's it...

 

As I said.....

 

That's right. MG owners manual, P90: F 2.2/2.3 bar (32/33.5 lb), R 2.4/2.5 bar (35/36lb)....

 

KB

[Guest trispeed]

right on, let's ride!

[Baldini]

right on, let's ride!

81554[/snapback]

 

...errr......but it's raining..... ?

[Guest trispeed]

We actually have some rain this weekend in LA, too. Snow is quite close and all the mountain roads will be covered in muck for sometime. There is a track day on Monday though.....hmmmmm.

[dlaing]

...errr......but it's raining..... ?

81701[/snapback]

That is when you want a lower tire pressure

[helicopterjim R.I.P.]

FWIW, found a PDF on the Michelin track testing at Ladoux on the Pilot Power.  Couldn't find a similar PDF on the Sport.

 

Test tire specifics:

 

120/70ZR17 on 3.5" rim @ 2.5 bar (36 lb.)

180/55ZR17 on 5.5" rim @ 2.9 bar (42 lb.)

81494[/snapback]

 

 

What kind of bike were they using for the testing?

[Guest ratchethack]

What kind of bike were they using for the testing?

Jim, I looked for this but the PDF didn't say.

[dlaing]

The old method of looking for a 10% rise from cold to hot pressue is just that; the old method. Ask a tire rep at the track next time you're there.

81424[/snapback]

I asked a Pirelli rep years ago, and I understood him to indicate that we should be pursuing a minimal rise in pressure at the lowest possible pressure rather than a 10 percent rise.

So the process might go something like this:

set to 42psi cold, ride then check.

set to 40psi cold, ride then check.

set to 38psi cold, ride then check.

set to 36psi cold, ride then check.

etc.

With each check you are looking for a significantly greater rise in pressure.

You could graph it and get a nice curve helping you figure out where to set it,

or you could just set it to 32-42PSI and ride.

Heck, I have three gauges and they are about 4PSI apart from each other.

Using the most expensive and lowest reading gauge, I find the tires feel too soft at 32 PSI and too hard at 38PSI, so I run around 34 to 36...works well enough, but tire mileage could be better.

I just got 4000 miles out of a Dunlop D208 Sportmax that I was keeping at 36psi.

It was replaced when center treads hit the wear indicators...which is when we are supposed to, right?

This sport is too expensive