Tire pressure

[Norm T R100T R1150RT]

No problem gettin mileage on my Airhead - K bike n Oilhead - on the rear I wear out the center first - way ahead of the outside - runnin 36 fr - 42 rr on the K, 38fr - 42 rr on the Oil - higher pressures wear out the center sooner ? Mostly concerned with the rear as both eat off the left side of the front - but a change in pressure may be beneficial there too. Your thoughts ? Thanks, Norm ( this post belongs elsewhere I'm sure, but this place seems to get the most attention and response - again, I thank you all )

[Kurt in S.A.]

What does an owner's manual say? What about the tire sticker on the bike...maybe under the seat? Regardless, yes higher pressures means the tire doesn't deflect and a smaller portion of the tread is touching the ground at any time. Less tread touching the ground also reduces traction and braking surface. I run 36 in the rear of my /7...I'm sure a K and Oilhead are heavier so the pressures need to be higher. I'd say that 38/40 in the rear for you would be more appropriate.

Kurt in S.A.

[PAS]

Most tire mfg'rs have the specs for your bike on their website.

[barryh]

It's inevitable that pressures are a compromise between sharpness of handling and the size of the contact patch which will equate to wear particularly on the rear.

The way I decide on the compromise is to consider that tire temperature is more important than either sharpness or wear pattern. It's all very well having sharp handling but unless there is some deflection in the tire it won't heat up enough to provide optimum grip. I use the 10/20 rule after a spirited ride. If the front hasn't gone up 10% from the cold set pressure then the pressure was too high to start with and if it's gone up more than 10% then it was too low. Same for the rear using 20 % although some say the rule is not 10/20 but 10/10. I still find the rear gets hotter than the font so I'm generally happy if it's gone up at least 15%.

Following those guidelines I end up with no more than 33 in the front and 36 in the rear but the type 248's are lighter than some airheads and so am I.

The rear still wears in the centre of but not excessively.

Alternatively don't ride on straight roads.

[Kurt in S.A.]

I've heard about the 10% rule, but I'm wondering if that was established "back in the day" when tires flexed a lot more. I had a Dunlop on the rear of my /7 and experimented with a stretch of road and tried to control the variables as best as I could. According to my data, for any reasonable rear tire pressure (say high 30s), the increase was only in the 7% range. For me to get nearer the 10% value, I had to lower my cold pressures to the low 30s in psi. I wasn't going to do that. So, I used tire manufacturer and local tire shop information and went with 36 in the rear.

Kurt in S.A.

[Duane Ausherman]

Back in the day, the recommended pressure for approved tires was so low that they had a far greater tendency to wobble at low speeds.

I wouldn't be surprised to learn that everything that I once knew, or thought that I knew, is no longer valid. That applies to far more than just tires.

[barryh]

Every motorcycle forum on the net talks about the 10/10 or 10/20 rule but I guess that doesn't necessarily make it a valid and current method. Confirmation by a more accountable source like a tire company would be better.