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Guzzimundi
Senior Member
257 Posts
[Mentor]
Palmeira, Coruna
Spain
Moto Guzzi
Breva 750
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 Posted - 04/17/2008 : 5:57 PM
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How often should tire pressure be checked?
How often do you check it?
How do you check it? Are there pressure gauges specific for motorcycles? Any recommendations?
My tires state front 220 kpa and rear 240 kpa. How is this measurement interpreted?
Many thanks, as usual.
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scottrnelson
Advanced Member
4748 Posts
[Mentor]
Pleasanton, CA
USA
Ducati
ST2, 888, + XR650L
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Posted - 04/17/2008 : 6:16 PM
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I hope you'll delete the redundant versions of this post before they all start collecting answers
How often should tire pressure be checked?
Right before every ride.
How often do you check it?
Every week or two, if I remember. I've been pretty good lately about doing that.
How do you check it? Are there pressure gauges specific for motorcycles? Any recommendations?
Any tire gauge that works for a car will work for a motorcycle. Some motorcycle valve stems are kind of awkward to get to, especially if you have dual 320mm brake disks like on both of my bikes. I found a digital gauge at Walgreens that was relatively inexpensive and works very well. You push a button to reset/activate it, then stick it on the valve to get a reading. Unlike many other gauges, it doesn't let a significant amount of air out of the tire, and it's accurate to half a pound.
My tires state front 220 kpa and rear 240 kpa. How is this measurement interpreted?
You'll have to get that converted to lbs/sq in, and I don't have the formula offhand.
Normally you want about 34 lbs./sq. in. in front and 36 in the rear. Don't use the "maximum" value that is often printed on the tire sidewalls. |
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twc
 Advanced Member
627 Posts
[Mentor]
Fort Collins, CO
USA
Harley-Davidson
Electra Glide Ultra
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Posted - 04/17/2008 : 6:38 PM
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How often should tire pressure be checked?
Right before every ride.
How often do you check it?
Before every ride -- but when commuting I'll often check the tires on the bike I plan to ride the evening before I plan to ride it. On the way home, I just eyeball the tires before I head out. I think of it more like stopping at a restaurant when out for a ride: I don't check the tires before continuing on in that case, either.
If I'm going out on a weekend ride, I'll check the tires right before I leave. No exceptions.
I've heard that confession is good for the soul: The one time that I can remember not checking my tires before heading to work, I had a flat tire on the way to work -- with a tire that had all of 200 miles on it. Interestingly, I didn't even realize that the tire was all-but-flat until another motorist pointed it out to me as I arrived at the HP parking lot. BTW, that was the rear tire on the Kawasaki. Of course, I didn't know if the tire started out that way or if I picked up the nail (for so it proved to be) on the way to work. That's also the day I learned that motorcycle dealers won't patch motorcycle tires.
How do you check it? Are there pressure gauges specific for motorcycles? Any recommendations?
Just an ordinary stick-pops-out-the-end tire pressure gauge. As Scott noted, it's a PITA checking pressure on the front tire, but I finally arrived at a workable gauge orientation.
My tires state front 220 kpa and rear 240 kpa. How is this measurement interpreted?
220 kpa is 32 psi and 240 kpa is 35 psi. Check this handy web site for a tool that does the conversion for you.
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Jim B
Senior Member
488 Posts
Newark, Delaware
USA
Honda
CMX250 & CB750
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Posted - 04/17/2008 : 7:05 PM
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Ditto what they said above.
The only exception is that 'eyeballing' the tires is not a very good idea, as I have learned. When I picked my bike up from the dealer, I assumed they checked everything before giving it to me. Tires 'looked' fine. After about a month of occassional riding, I decided to check the pressure, and was shocked to see the front tire at 18PSI and the rear at 22PSI. After filling them up to the correct pressures, the bike handled a lot better. |
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twc
Advanced Member
627 Posts
[Mentor]
Fort Collins, CO
USA
Harley-Davidson
Electra Glide Ultra
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Posted - 04/17/2008 : 9:50 PM
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quote:
Originally posted by Jim B
After about a month of occasional riding, I decided to check the pressure...
I admire your honesty, especially in this forum 
I'm waiting to see if somebody actually checks their tire pressures before leaving work for the return trip home, or after a restaurant stop, so I can feel really guilty. |
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Speedmaster07
Senior Member
287 Posts
Los Angeles, CA
USA
Triumph
Speedmaster
Peer Review:
Blocked
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Posted - 04/17/2008 : 10:18 PM
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| I have cast wheels and tubeless tires on my bike. I check the pressure the same as I would in my car--eyeball it before every ride, and check with a gauge about once a month. Over a month's time, they never lose more than a pound or two. |
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radan2
Advanced Member
763 Posts
[Mentor]
Jacksonville, NC
USA
Moto Guzzi
2007 Breva V750 ie
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Posted - 04/17/2008 : 10:19 PM
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I bought some of those screw-on valve stem pressure indicators that show a yellow or red ring if the tire pressure falls. I use those as a pre-ride check. Once a week, I take them off and check the pressure with a regular dial-type pressure gage. So far they have been highly accurate on my bike and on my truck. When I pick up a nail in my back tire on the way to a PGR event, I thought the bike was feeling a little squirrelly, but the second I saw the red ring on the indicator, I knew that the tire had lost air. I drove slowly to the next store with an air pump and pumped up the tire, then examined it. I found the nail embedded in the tire. I went to a tire store and they plugged the tire, which enabled me to get home.
I recommend the tire-stem indicators. You must choose a cap for the specific pressure of your tire. They come in even-numbers, and the maker recommends you buy the next higher one if your recommended pressure is an odd number.
Here is the url:
http://www.accupressurecaps.com/ |
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lostinspace
Junior Member
94 Posts
Vancouver, BC
Canada
BMW
f650gs
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Posted - 04/17/2008 : 11:14 PM
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I know this be a bit crude, but after I fill my tires to the correct pressure I squeeze them between my finger and thumb to check how hard they are. Before I ride I squeeze them again. If they feel really hard, I ride. Regardless of how they feel, I check them with a gauge every 2 weeks or so.
I also check my car tires several times a month. Its surprising how much you can lose without realizing it. Phil |
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shauntwomey
Standard Member
157 Posts
West Lafayette, IN
USA
Yamaha
'07 VStar 650 Custom
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Posted - 04/17/2008 : 11:55 PM
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quote:
Originally posted by radan2
I bought some of those screw-on valve stem pressure indicators that show a yellow or red ring if the tire pressure falls.
I checked out the website and these indicators seem like a really clever idea. Thanks for the link! |
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Tamarack58
Standard Member
116 Posts
Cleveland, OH
USA
Yamaha
V-Star 1100
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Posted - 04/18/2008 : 12:43 PM
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Other then "eyeball" them berfore I ride I don't check the pressure with any regularity. Not because it's unimportant but because I can immediately (well, by the end of my street)feel a difference in handling when my front tire loses 2 lbs. and when my back tire loses 2-3 lbs. I always have my tire guage on the bike so I can get an accurate reading whenever and wherever I need air.
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bridwell52
Senior Member
372 Posts
Pensacola, FL
USA
BMW
KGT
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Posted - 04/19/2008 : 5:47 AM
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I recommend the tire-stem indicators. You must choose a cap for the specific pressure of your tire. They come in even-numbers, and the maker recommends you buy the next higher one if your recommended pressure is an odd number.
Here is the url:
http://www.accupressurecaps.com/
[/quote]
Jim,
Is there a balance problem after installing these? They look like a great idea.
David Bridwell |
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bkikkert
Advanced Member
796 Posts
[Mentor]
Cornwall, Ontario
Canada
Harley-Davidson
Ultra Classic-FLHTCU
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Posted - 04/19/2008 : 6:46 PM
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quote:
Don't use the "maximum" value that is often printed on the tire sidewalls.
Scott...I keep getting confused about this issue but I'm sure that James recommended inflating to the maximum stamped on the tire... |
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BÖCstar
Junior Member
90 Posts
Louisville, KY
USA
Yamaha
V Star 1100 Classic
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Posted - 04/20/2008 : 2:03 AM
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| I had those stem pressure indicators on my bike. I took the bike in for service and upon picking it up my mechanic handed them to me and told me these things are crap. My tires were 10 psi low and the green inicator was still showing. He said he's never trusted them and if they get a little loose you will lose air pressire cause they hold down the check valve. Be careful if you decide to trust them. |
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scottrnelson
Advanced Member
4748 Posts
[Mentor]
Pleasanton, CA
USA
Ducati
ST2, 888, + XR650L
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Posted - 04/20/2008 : 4:32 AM
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quote:
Originally posted by bkikkert
quote:
Don't use the "maximum" value that is often printed on the tire sidewalls.
Scott...I keep getting confused about this issue but I'm sure that James recommended inflating to the maximum stamped on the tire...
You'll have to provide a link to prove that. Use the search function.
For sportbike tires, most list the maximum pressure as 42 psi, but the manufacturers usually recommend somewhere around 33 front and 36 rear.
I tried higher pressures with my first set of Avon tires, at the recommendation of a number of riders who ride the same motorcycle as me. It was "common wisdom" that 38 front and 42 rear was just about as good for traction and helped the tires last longer. I didn't find any improvement at all in how long the tires lasted, but the traction seemed fine. After trying that for one set, I went back to the pressures recommended by the manufacturer.
So bigger, heavier bikes, might recommend higher pressures, but it's definitely not a general rule for all motorcycles to inflate to the maximum listed on the sidewall. Doing so can reduce your traction. |
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bkikkert
Advanced Member
796 Posts
[Mentor]
Cornwall, Ontario
Canada
Harley-Davidson
Ultra Classic-FLHTCU
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scottrnelson
Advanced Member
4748 Posts
[Mentor]
Pleasanton, CA
USA
Ducati
ST2, 888, + XR650L
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Posted - 04/20/2008 : 12:15 PM
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quote:
Originally posted by bkikkert
Here's the link Scott:
http://www.msgroup.org/forums/mtt/t...OPIC_ID=1620
Thanks for looking that up. I'm surprised that I didn't get involved in that argument discussion.
Oh well. The only thing I'm sure of is that if you have sporting tires that get better traction when warmed up than when they're cold, they'll warm up much better at lower tire pressures. People who ride track days often run lower tire pressures than on the street - like 28 to 32 pounds. I understand that the MotoGP racers can go into the low 20's on their air pressure.
I'm still sticking with 33/36 on my bikes. |
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James R. Davis
Administrator
14193 Posts
[Mentor]
Houston, TX
USA
Honda
GoldWing 1500
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Posted - 04/20/2008 : 12:43 PM
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quote:
So bigger, heavier bikes, might recommend higher pressures, but it's definitely not a general rule for all motorcycles to inflate to the maximum listed on the sidewall. Doing so can reduce your traction.
Well, for one thing it is not a 'rule'. It is a rider preference.
For another, I have found, without exception, that running at or near the high psi stamped on the sidewall does result in greater mileage, but on the other hand I do not ride a sport bike and so my mileage tends to be on the center tread more than yours does.
So let's try to see the logic of your last sentence "Doing so can reduce your traction."
The tire pressure is not isolated from the rest of your suspension system - it is part of it. Thus, the higher that pressure is, the more work is performed by the springs in that suspension. At an unreasonably high level your tire would deform trivially and thus all irregularities are 'absorbed' by your shocks while lower pressures result in more of those irregularities being absorbed in the deformation of the tire itself.
When you are riding in a straight line only significant irregularities (bumps) stress your springs/shocks. Just as is the case with large trucks when they run unloaded, your shocks might well be too strong to absorb such irregularities 'smoothly' and the result of that is that your tire (usually the rear) will bounce on the pavement. Of course when it does that part of the time it is in the air and no traction exists. In that case, and only that case, can too high air pressure result in lower traction. But that, I think you will agree, is actually a mis-tuning of your shocks. Still, it is supportive of your assertion.
When you are leaned over on your bike those irregularities are reduced in so far as they impact the springs/shocks at a vectored angle. Thus, bouncing of the tires in response to irregularities is almost non-existent. However, higher pressures result in less slip angle of those tires when you either accelerate or decelerate - that would appear as slightly better traction.
Having high air pressure means that to a very modest extent the tire profile is different than with somewhat lower pressure. With high pressure when your bike is leaned over slightly more of the center tread is part of the contact patch than with lower pressure. If the tire compound is such that you have greater traction when riding on the curved surfaces (are leaned over) then it is also true that you would have trivially less traction with higher pressure.
The different in tire profile (especially the size of the contact patch) from a tire with 42 psi in it as compared to 36 psi is, I believe, almost too slight to measure.
But from a purist point of view, or from a high performance canyon carver's point of view, I suppose you could fairly claim that there would be slightly less traction when using a higher pressure than from a lower pressure.
Again, presuming that there is a noticeable difference in contact patch profile with such a slight difference in tire pressure, and using the same argument about being more dependent upon the center tread area as a result (and further necessitating the argument that the center portion of the tread is harder than the curved sections to the side of the center tread), then it follows that the tire life should be increased using the higher pressure.
Rule? Nope. Rider preference, as I said earlier.
If you are religiously or fanatically rigorous in testing air pressure before every ride, then one of the principal advantages of setting that pressure to near max is eliminated - that tire pressure is lost, normally, over time and so starting at a higher pressure you have more time to be sloppy before it decays to dangerous levels.
And, finally, a higher air pressure adds a slight advantage in hydroplaning avoidance. You might consider that as yet another traction advantage, no?
All in all I am dubious about the claim that higher air pressure can result in less traction. But maybe I have missed something in my thinking. |
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degaboh
 Senior Member
258 Posts
Houston, TX
USA
Kawasaki
Ninja EX250R
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Posted - 04/20/2008 : 1:43 PM
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After all this talk about checking tire pressure, I thought it was probably a good idea to do that with the Ninjette. (Don't yell at me, I know I should have done it sooner). We have a gauge (which turned out to be very crappy), so we used that - pressure was a little low (about 2 psi off for both front [should be 28 psi] and back [should be 32 psi]) but how do we know if that's even within the standard error for that gauge??
Anyways I started getting paranoid and insisted we go fill up the tires to the proper level. The SO first tries to fill it up with his bike pump (having heard from one of our friends with a Ducati that this works for him). No go. Stupid valve stems are retardedly short and won't seal well.
So this morning I take the bike (followed by the SO in the car) to a gas station. Stupid valve stems are STILL too short. More air is let out just trying to fill it up. Checking the pressure with the gauge makes me more paranoid because the pressure has dropped even more.
I see a Firestone shop right across the street, so we go there and I plead (real well) to see if they can help me fill my tires to the right pressure. This AMAZING lady comes out and tries a couple of times with their air pump to fill the front tire, then gets a good seal and fills it to the right level. She got a "pops out" gauge from her car and checked the psi with that. When I asked her where she got that kind of gauge from, she said I could have it! She was awesome.
So the tires are filled now, I have a gauge that actually works, BUT my question is - does anyone else have this problem??? Do I need to go find a tire shop every time I want to fill the tires with air?
Should I just have the valve stems changed out to longer ones?
Also, am I being too paranoid?? If the tire pressure is off by 2 psi, is that a big deal or do I need to calm down and take a valium?
Thanks!
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James R. Davis
Administrator
14193 Posts
[Mentor]
Houston, TX
USA
Honda
GoldWing 1500
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Posted - 04/20/2008 : 1:57 PM
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Typical valve stems are made of rubber. Over time they crack and/or get brittle. If for no other reason, that is why you insist that new valve stems be added when you change tires. Cash has experienced the frustration of being a thousand miles away from home, driving into a gas station at the beginning of the day (before riding more than a mile, or so) and finding that when she applied the air chuck the valve stem cracked where it joins the tire rim and losing integrity entirely. That is the end of riding until the stem is replaced and the tire properly aired up.
She has also, like you, experienced difficulty getting a good fit on standard valve stems because they typically are simply straight and point to the center of the wheel where there is little room to get the chuck in place properly. That resulted in buying metal valve stems with a 90 degree angle built in so that chucks can gain access from the side of the tire.
2 psi is insignificant in terms of safety so long as the air pressure that exists remains within the range listed on the sidewall. Most people cannot tell from their riding experience that a tire is 2 psi under inflated.
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Cash Anthony
Administrator
1056 Posts
[Mentor]
Houston, Texas
USA
Honda
Magna 750
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Posted - 04/20/2008 : 2:47 PM
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I found this discussion about tire valve stems that could be of interest. You'll want to go ahead and pay for some good ones - it's not a high-cost item so you might as well. Here's a link to a page with a picture of the 90-degree valve stem, and several choices of stem caps. You'll need to scroll way down the page to see them after the tire prices.
I did have the metal ones put on when I got the 90-degree variety. So far they have worked great for me.
It's not just the issue of the clearance to get the chuck onto the stem because of the "spokes" and brakes, it's also the fact that Jim and I both have bags mounted on the bikes which are not movable, so you can't just push them out of the way. We always end up having to roll both bikes around a little bit to get to a good position on front and back tire (never the same, of course, it's a part of the design).  
Anything (safe) that makes getting to them easier is a real help.
Cash
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twc
Advanced Member
627 Posts
[Mentor]
Fort Collins, CO
USA
Harley-Davidson
Electra Glide Ultra
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Posted - 04/20/2008 : 3:24 PM
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quote:
Originally posted by degaboh
- ...how do we know if that's even within the standard error for that gauge??
- ...does anyone else have this problem???
- Do I need to go find a tire shop every time I want to fill the tires with air?
- Should I just have the valve stems changed out to longer ones?
- Also, am I being too paranoid??
- ...do I need to calm down and take a valium?
In order: You don't. Yes. No. No. No. Yes.
You do need to make sure your gauge is reading correctly. I have enough of them floating around that I just calibrate them against each other, so either they're all right or they're all wrong. I suspect the former. You can check your gauge against others at gas stations and/or tire shops. Keep in mind that some gauges are particular about how they're used so you should use a consistent technique. Dial gauges are great, but in my experience they have a short lifetime.
Yes, I probably have exactly the problem you do with my Kawasaki and the Harley's not much better.
No, you don't need to go to the tire shop, nor do you need to change your valve stems. You just need to develop the right technique. I find that trying to reach in under the brake disc is hopeless. Get your whole hand inside the wheel in between the discs and come at the valve stem along the plane of the wheel, or as close as you can get to that. Works much better. Somebody else mentioned 90-degree fittings and that may help; mine are at a slight angle and they work OK. You did remember to rotate the wheel so the stem isn't hidden behind the caliper, right?
The bicycle pump is hopeless even if you could get it attached. Bicycle pumps are meant to deliver a little bit of air at high pressure. You need a greater volume of air at lower pressure. Technically, the bicycle pump will eventually work but there are better solutions. For about $50 or so, you can get a pressure tank, an air hose and the necessary fittings to let you pump up your tires yourself. You can fill the pressure tank at your local gas station and (if you keep the valve shut off) it will last for several months of topping off tires. Much cheaper than buying your own air compressor.
No, you are not being too paranoid. Tire pressure is important, you only have two of them and you're betting your life on them. But from our informal survey I'd say I'm about 3-sigma cautious about tire pressure so you can judge my response from that. FWIW, I follow the manufacturer's recommendations on tire pressure.
Enjoy your Valium!
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