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Does tire pressure make that much of a difference?

georgej

Member
I rode my RS down to Color in the Catskills Saturday.Before we left I put some air in the front tire,Metzler Lazertec.I usually run28-30 psi andthe crappy gauge at the station red around 33 or so.We were anxious to get going and off we went.On uneven pavement or those roadsnakes or almost any i perfection in the road the bike felt very unstable.I'm not a fast rider cruising along at 55-60 indicated.So can an overinflated tire,even by a few pounds make that much of a difference?
 
33 front is not overinflated.

on an airhead, I would wager that 34F/38R would be pretty close to ideal.

what was your rear tire inflation?
 
How sure are you of the "crappy" reading of 33? Maybe it was closer to 36 or higher??
 
I don't trust gas station guages. I learned this early. As a kid, I would ride my bike into town, fill the tires up at a local gas station and go to a local store. Twice in about a month, both tires would be flat when I came out of the store. When I took out the tubes, they were blown--huge big holes that could not be patched. Since then, I carry my own tire pressure guage. My experiences have been that the station guages typically under estimate the pressure, which appears to be due to sliding guage portion getting bent by being dropped alot.
 
My experience is that under inflation causes these handling problems. Under inflation causes a feeling of wandering, pushing wide on corners, sluggish response to steering inputs, etc. I have never knowingly ran my tires over inflated by more than 3 - 4 PSI. The only difference I could tell was it the bike road a little rougher.
 
I'll have to check the pressure with my gauge.It seemed ok before I added air to the tire.The rear tire is at 30 psi.My friend suggested less stiff fork springs after he rode the bike for a half hour or so.
 
Rear tire pressure should be much higher than that. Probably around 36 psi...higher if carrying a another passenger or significant load. No higher than the sidewall cold inflation pressure, though.
 
Pressures in the vicinity of 30 are great... if you're running the bike on the track. Too low for street usage, unless you really like getting about 60% of possible tire life.
 
... I usually run 28-30 psi ...

I believe you have been running both tires with too low pressure. Don't know the specifics of your bike and your brand of tires, but usually m/c street tire pressures are in the neighborhood of 35-38 front and 40-44 rear. You have likely gotten used to riding around on low pressure tires and when you pumped them up a bit it felt strange and unstable to you. Buy yourself a gauge (most studies say any gauge is OK if you take care of it), then look at the max psi on the sidewall of your tires. Then check your bike's owner's manual--or Google it--for the recommended pressure. Start with the recommended psi, and you can go up a bit but not beyond the max psi shown on the tire.
 
I believe you have been running both tires with too low pressure. Don't know the specifics of your bike and your brand of tires, but usually m/c street tire pressures are in the neighborhood of 35-38 front and 40-44 rear. You have likely gotten used to riding around on low pressure tires and when you pumped them up a bit it felt strange and unstable to you. Buy yourself a gauge (most studies say any gauge is OK if you take care of it), then look at the max psi on the sidewall of your tires. Then check your bike's owner's manual--or Google it--for the recommended pressure. Start with the recommended psi, and you can go up a bit but not beyond the max psi shown on the tire.

I changed both tires about 3 month's ago, and was really surprised because the new ride felt like something was wrong. When I "rolled" into a turn, I felt like I was going to fall over - it was too easy. I just found out that both my old tires must have had enough "flat" spot in the middle making it harder to roll the bike into a turn. With the new tires - WOW, they didn't have that flat spot in the middle. I agree, that below 30 psi is probably too low. I like mine up in the mid to high 30's. I never ride 2-up, but if I did, I would increase rear pressure to up around 40-ish.

Best is to get a gage that you use constantly. Just maybe have your gage "gaged" with another to see where it stands in relation to another gage. Then when you find a pressure that works for you (within the limits described by other above), then use YOUR gage and no other to keep track of your own pressures, not the gages on the gas station air pumps.
 
38-40 PSI on almost all my Vintage and Classic bikes, 33-35 on the track bikes and 40 front and rear on the modern sport tourers.
 
Why not just run what the manufacturer recommends?

With the older bikes, there have been substantial changes in tire construction since the bikes were produced. While the tire manufacturer information might be appropriate, and probably is, the bike manufacturer information is not. The best process is to stay under the rated (sidewall printed) maximum and find the correct pressure for the load by looking for a 2 psi increase from cold to hot. Some say a 10% increase, but I think that is better track guidance than street guidance. A rise of 5%, or more simply, 2 psi gives better tire life but still some warming of the tire.
 
Why not just run what the manufacturer recommends?

Nothing specifically wrong with that, but you can find a "better" sweet spot by moving your tire pressure around a bit in increments. Different tires and different weights/loads and different riding techniques--all on the very same motorcycle--can respond differently and you might discover you prefer a different psi.
 
Nothing specifically wrong with that, but you can find a "better" sweet spot by moving your tire pressure around a bit in increments. Different tires and different weights/loads and different riding techniques--all on the very same motorcycle--can respond differently and you might discover you prefer a different psi.

It is good to have a "benchmark" to start. Then, by keeping careful records and testing in exactly the same way each time, one can then formulate what are the best pressures to use.
 
tar snakes to blame?

a bit of an aside
http://www.wristtwisters.com/forums/f162/my-enjoyment-vs-tar-snakes-33652.html
makes an interesting read.
I have noticed that it seems the compounds used for tar snakes vary from area to area and have universally become slipperier over the past few years. Hwy 14 out of Cedar City, UT, was incredibly slippery when I took it in May 13, and that was with relatively new Pirelli Scorpion Trails at proper inflation. It became better over the crest on 14, but my psyche was wounded by then and all sphincters were shut and I had a death grip on the grips. This road was taken probably at about low to mid 70s (degrees, not mph).
I guessed that the compounds used had changed, but the above article documents it and the wasteful and dangerous practice of using too much for the financial gain of the contractor.
John
 
I've been underinflated.

I guess I'll add a few lbs too and get better Obama fuel economy.....Good information from everyone, really!
 
Thanks for all the replies.After reading,I wondered how i could be so far off.Under the seat on both my bikes the sticker states max 30 psi.The tire which is a Lazertec states a max of 42 psi.So I guess I will go with what it says on the tire.
 
There's still some discussion that people like to have, but that 42psi is max cold inflation pressure. As a general rule, you probably don't want to ride at that pressure all the time. The ride will be rougher and you'll wear out the very center of the tire faster. Generally back off from that pressure. I know pressures are all over the map, but it seems that nominal pressures from what I've seen posted here and elsewhere would be 32 front and 36 rear. You can adjust from there due to feeling, handling, as well as with passengers or extra load when touring...maybe 1 psi higher in frong and 2-3 psi in the back.
 
Last weekend my RDC/TPS threw a warning at me. It said my front tire pressure was too low. I measured it and it was 36 psi. The ambient temp was in the upper 70's and I was hitting the twisties pretty hard so my guess is the actual tire temp was in the 80's. So NOW tell me what is the right tire pressure!?!? The RDC corrects the pressure to 20 degrees C or 68 degrees F. How many of you ride at a constant 68 degrees from start to return? Sunup to sundown. If you are riding in the 90's and pushing the turns, do you want the pressure pushing your sidewalls to be something corrected to normalized readings or what your digital pressure gauge says? I know what I do and have done for about 50 years. What do you do???
 
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