Tire pressure

[dziadzu42]

What do you run for tire pressure?

[montmil]

What do you run for tire pressure?

Usually just plain ol' compressed air.
Not into the nitrogen race tire thing.  

32/33F - 35/36R
Bridstone S11 Spitfires
R65s & R100S

[Bob_Roller]

Why don't you do a bit of experimenting and find what pressures work for you .

I've run as high as 40 psi .

But I don't recommend it, the steering is a bit ' quicker ' but that probably means there is less tire in contact with the pavement .

I  measured tire pressures and temperatures before and after running them 20 miles or so .

Different pressures will cause the tire to run at different temps .

Got a non contact infared thermometer at Harbor Freight for about $20 a few years ago, used it a lot more that I thought I would .

[nhmaf]

Indeed, a few PSI one way or the other can make a noticeable difference depending on tire brand/model, road surface and loading of the motorcycle.

I run 35-37 PSI in both front&rear tires on my R65LS with BT45 tires.   I run just a couple PSI less than that on my R100/7 with Trailwing D/P tires, and my Concours runs 38-40 PSI - the geometry and weight bias of the Connie tends to really scallop the front tires if you run the fronts less than 38 PSI.   Tire profile (110/70 vs 120/70) also makes a difference on that bike.

[Tony Smith]

There area   number of variables involved in tyre pressure that result in different tyre pressures working for different tyres on different bikes.
 
To explain, I am lucky enough to have a first class tyre testing road called the Gillies highway right in my back yard.

http://en.wikipedia.org/wiki/Gillies_Range
https://thebilgebucket.wordpress.com/2012/03/02/the-gillies-highway/

Depending on what you actually count as a "corner" there are between 263 and 385 "corners" in 19km or 11.9miles, Oh and it climbs (or falls depending on which way you are going) a bit over 800m (3,000ft) in that distance.

To say that the road is a blast from heaven is an understatement, riding "briskly" on the gillies is both a way of separation the men from the boys and  tuning a motorcycle's handling.
 
My R65 wears Pirelli City Demon tyres, 4.00*18 on the rear and 3.00*18 front. I would have preferred a 3.50 on the front but that was not available on the day I was buying tyres.

After a bit of fiddling I have come up with 29~30psi front and 32~34psi rear. These pressures give me good change of direction, acceptable absorption of road shock and adhesion limits that I have never fully explored as I chicken out when the crash bars touch down.

My wife's bike which has a 3.50 Dunlop on the front and 100/120 on the rear needs completely different pressures to feel anywhere near as good - 35 in the front and 28 in the rear. Mind you I hate the tyres on her bike, they were an emergency purchase and the rear is way too big, only just clears the swingarm and needs brute force to get it past the final drive even after being deflated. But she is gettign superb mileage from them.

[Barry]

I'm similar to Tony being in the middle ground between the old under seat pressures but some way off the modern view of close to 40 PSI. I also view the tires as part of the suspension as they will impact on ride quality if over inflated.

I run 32 Front and a maximum of 33-36 rear even two up without luggage but both of us are relatively light weight.  I confirmed those pressures using the 10/20 rule. after a good hard run the front pressure should increase by 10% and the rear by 20%. I'm happy when the pressures I measure are close enough to those guidelines.

The biggest concern anyone should have is running a pressure that's too low when really heavily loaded at high speed. That's when it can get dangerous from the tire overheating. It's rare that I don't touch a bare hand to the tires to check the temperature after a ride just as a confirmation that the pressures are about right.    

[thrang]

I'm very anal about checking my tires, and I usually run my LS at 30/32 front and 34/35 rear.

[Barry]

This is probably getting anal in the extreme but to expand a bit on the idea of tires being part of the suspension.
The tire can be thought of as a stiff spring in series with a soft spring (the main fork spring).  When you put two springs in series the resulting effective spring rate is always lower than either of the two springs.  For the electrical guys this is analogous to two resistors in parallel and in fact you can use the exact same formula to calculate the resulting spring rate.

 Overall spring rate =  (Spring 1 X Spring 2) / (Spring 1 + Spring 2)

To put in some typical numbers our standard fork springs are 27 lb/in and the spring rate of the tire might be something like 20 times stiffer at 540 lb/in. Together they lower the overall spring rate to  25.7 lb/in

So tire pressures don’t just change the way a bike feels in handling terms, they also directly impact on overall suspension rates.

[Semper Gumby]

What do you run for tire pressure?

Depends on the tires.

The manufacturer should be able to tell you.  All you will need to tell him/her is the weight of you and the bike.  The Maximum rating for weight and pressure is listed on the side of the tire.  Add the weight for the front and back tires will give you the maximum weight of you and the bike and the pressure (cold) you should be running.  On my R65 with the Michelin Pilot Activs that max weight is somewheres about 1000 lbs and the rated tire pressure is about 42 psi.  

My bike weighs in about 700 lbs with me and the fairing and the Givi bags.  I'm running about 38 in the rear and 34 in the front.  If you have a naked bike then you will not need so much pressure.

Good luck.

[Barry]

I think the maximum load capacity of the tire at its stated pressure is a good way to extrapolate minimum running pressures. I did a quick check of the load ratings of my M45's and together they came to 1150 lbs.

I'll have to calculate what that means for pressures at normal load. I suspect they will be quite low and certainly way below 40 PSI.

[Barry]

I've had a look at this idea of using the maximum tyre pressure and maximum load rating to extrapolate a tire pressure for the actual load that the tire sees on my bike. It might seem logical to simply draw a straight line between zero pressure/zero load and maximum pressure/maximum load but it just doesn't seem to work as it gave me a pressure of 23 PSI on the front tire which is obviously much too low.  I'm sure it can be done and it must be how the tire manufacturers arrive at their recommendations of 32 Front 33.5 Rear for mine. So I'll stick to those figures and push the rear up to 36 PSI for two up.