Tire Pressure ?

[suzukizone]

Am about to put new set of Bridgestone S11 tires on Roadkill. Read the "10%" method on a previous thread & will try this BUT I have a ?. '81 GS850G with Vetter Windjammer IV & lowers, KG rack & big Vetter trunk, tank bag & set of big Chase/Harper throw-over saddlebags. I usually carry a lot of stuff in trunk & tank bag at all times (tools, gold coins, dead dismembered body parts, the usual :-). On trips I guess I'm running around 850 lbs +/- plus my fat (230 lb butt).

I had found that handling-wise 34.5 F & 37.5 R was best tire pressures. This after thousands of miles & years of testing.

My front tire shows it was underinflated (outer edges worn more) My rear tire shows it was overinflated (center area worn more). I have been compensating recently by setting 35 psi F&R & guessing that actually having the front set to a higher setting than rear would give the most even wear tho I hsven't gone there yet.

Can such a thing be????? Every word on T.P. I've ever read says NOPE! Rear at least a few lbs higher but my tires say it needs be.

Want to get this right with new set so They last longer than I do.

Anybody with a similar rig & bike ever find this?? I don't ride on Interstates much & usual cruising is 55-65, Most riding is around town, shopping, etc. Of course I will run the test as described (10% over cold set after run) & try to find solution that way but don't want to get way down the road & find a similar goofy wear pattern

I submit to the group wisdom.

Thank you in advance.

[7981GS]

Try 38/38

Eric

[Billy Ricks]

Do the 10% thing. It's what get's you the most traction and handling out of your tires. It will be more than enough pressure to support the bike.

[Steve]

I have always found the 10% rule to be pretty good.

Just for reference, I have Shinko 230 Tour Masters on my 850. It is also fully-dressed (see pic in my sig). I run 32f/36r when riding solo and 32f/40r when riding two-up.

Have not had enough miles on the tires to see an appreciable wear pattern or determin how long they are going to last, but they feel good for now.

.

[7981GS]

On trips I guess I'm running around 850 lbs +/- plus my fat (230 lb butt).

I had found that handling-wise 34.5 F & 37.5 R was best tire pressures. This after thousands of miles & years of testing.

My front tire shows it was underinflated (outer edges worn more) My rear tire shows it was overinflated (center area worn more). I have been compensating recently by setting 35 psi F&R & guessing that actually having the front set to a higher setting than rear would give the most even wear tho I hsven't gone there yet.

GVWR is 1084 pounds BTW.

Eric

[sedelen]

Never tried the 10% rule, I just follow the manufactures tires recommendations.

[Billy Ricks]

Never tried the 10% rule, I just follow the manufactures tires recommendations.

If you're using the pressure stamped on the tire that's the maximum pressure for the maximum load range of the tire. Running tires too hard never lets them warm up and leads to less contact patch and less traction.

[Steve]

Never tried the 10% rule, I just follow the manufactures tires recommendations.

That might work if every bike manufacturer knew about all the tires that could possibly be put on their bikes.

The real problem is that tire "A" might be rated to carry 800 pounds at 36 psi, while tire "B" is rated to carry 800 pounds at 40 psi. Now let's say that your load on that tire is going to be 700 pounds. One tire will need to be inflated to about 32 psi, the other to about 36 psi. If the bike manufacturer did not know about tire "B" and only said "inflate to 32 psi", and you installed tire "B", it would be seriously under-inflated at 32 psi.

To make things worse, I think some of the tires that were fitted as original equipment were rated for their maximum capacity at 32 psi, so their recommended pressure might be as low as 28 psi. Newer tires are rated for the same loads, or even a bit higher, but at higher inflation pressures, so you have to do some of your own testing. Start with a modest pressure like 30 psi, then follow the 10% rule.

.

[sedelen]

That might work if every bike manufacturer knew about all the tires that could possibly be put on their bikes.

The real problem is that tire "A" might be rated to carry 800 pounds at 36 psi, while tire "B" is rated to carry 800 pounds at 40 psi. Now let's say that your load on that tire is going to be 700 pounds. One tire will need to be inflated to about 32 psi, the other to about 36 psi. If the bike manufacturer did not know about tire "B" and only said "inflate to 32 psi", and you installed tire "B", it would be seriously under-inflated at 32 psi.

To make things worse, I think some of the tires that were fitted as original equipment were rated for their maximum capacity at 32 psi, so their recommended pressure might be as low as 28 psi. Newer tires are rated for the same loads, or even a bit higher, but at higher inflation pressures, so you have to do some of your own testing. Start with a modest pressure like 30 psi, then follow the 10% rule.

.

Two things affect my decision to what amount of pressure to put into the tires. One is handling and the other is braking. If my pressure is too high, I tend to oversteer, feel every pepple in the road, have a small foot print from the tire and more of a tendancy to skid. I feel I have more control with the recommended tire pressue, my load is light, just me, about 170lbs. I generally use about 27 front, 31/32 rear, Avon Roadriders. These pressures work well for me. Someday I may do some experimenting with this 10% rule.

[sedelen]

If you're using the pressure stamped on the tire that's the maximum pressure for the maximum load range of the tire. Running tires too hard never lets them warm up and leads to less contact patch and less traction.

I guess what I should have said was "I just follow the motorcycle manufacturers recommended tire pressures."

[Billy Ricks]

I guess what I should have said was "I just follow the motorcycle manufacturers recommended tire pressures."

You're probably within a couple of pounds of where you should be. These pressure checks should be done according to what's a normal ride for you. Air and road surface temperatures are going to screw with the pressures too.

[koolaid_kid]

Never tried the 10% rule, I just follow the manufactures tires recommendations.

This works great with 1981 tires. However, tire technology has changed a bit in the last 30+ years. The 10% rule will get you a lot closer to the ideal pressures.

[koolaid_kid]

10%, there is no standard psi, every bike is different based on the bike, rider, gear,tires, mine are at 34/36 with shinko's

Yes, plus weight (it will change if you go on a trip and carry more gear), riding style, ambient temperature (different in winter than in summer). Best to measure than to guess.

[Steve]

Someday I may do some experimenting with this 10% rule.

Very easy to do, you don't even have to change anything.

Check your pressures before you start your ride, record them.

Ride for at least 25 miles to make sure the tires get warm, check the pressures, record them.

Compare the warm pressures to the cold pressures, you might be surprised to find that they are about 10% higher.

Done.

Let us know what you find.

.

[bwringer]

The wear the OP described is perfectly 100% normal, and not any indication of incorrect inflation pressures.

Remember, you are NOT looking at low-tech car tires -- you are looking at MOTORCYCLE tires, so leave car-based thinking behind.

Motorcycle tires wear out quickly and as the OP described. It's just part of the deal, and nothing you can do will safely change this.

Use the 10% rule, and your tires will give the best available balance of traction, and they will last as long as possible.