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Old 07-30-2013, 09:18 PM   #1
PalePhase OP
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Question Adjusting Tire Pressure By Growth Vs Bike Mfr's Recommended Tire Pressures?

I'm a street-only rider, and up until recently set my tire pressures religiously per the bike mfr's recommended pressure. I weigh 205 lbs, so I had never though that dropping tire pressure was a great idea. Recently, however, when I had my VFR in a local shop for some service, the shop owner and his suspension guy both recommended I back off on the cold pressure I was running in the tires (36 psi front and 42 psi rear). The bike is currently shod with Continental Road Attacks, and the suspension guy said he picked up on some headshake while test riding it. I have not noticed any such issue to date, but then I never take both hands off the bar while in motion. Nevertheless he and the shop owner (who has a some noteworthy racing credentials) both said the bike was twitchy at Honda's recommended pressures and recommended I back off to 34 psi front and rear and maybe go as low as 32 in the rear. It had 35 front and 33 rear when I got it back, and though that intuitively seems too low to me, the bike definitely feels more planted. I checked the rear tire pressure before and after my commute and found both tires had gone up about 12% in pressure after my 12-mile ride.

My question for the Intelligentsia here is what you use to determine tire pressures for your bikes when street riding? Do you adhere strictly to the bike mfr's or tire mfr's inflation recommendations or do you chart your own course? If you don't follow either mfr's recommendations, what criteria do you use to determine appropriate pressure?
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Old 07-31-2013, 05:21 AM   #2
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I'm not exactly sure what to tell you other than I understand the expansion of the mess of gasses we breathe amounts to.
Maybe those guys at the dealer are right on the money. Over and under inflation pressures have their place but you're talking about a different application.
Really I don't push nitrogen because there is already 78% in the air, but in the small casing of a m/c tire for your application you may find the minimal expansion rate to suit your needs.

Just for the record I never try to sell people on nitrogen unless there is an extenuating circumstance that another 22% of the crap may alleviate.
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Old 07-31-2013, 05:27 AM   #3
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Run what feels right to YOU. You are the one riding it...

For me, this is usually within a few pounds of what the sticker in the bike/owner's manual says.

I also have a VFR and I run 36F and 40R. Any less than that it it starts to wallow and feel sloppy. More than that and and can start feeling skittish.
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Old 07-31-2013, 05:30 AM   #4
JimVonBaden
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There are several ways to set air pressure, and for various reasons. Up to the manufacturer's maximum it is generally better for tire life to run the maximum pressure you can while maintaining decent traction charactoristics. On the other hand, racing pressures often run lower for pure traction. Example, on my R1200GS I run pressures of 38 front and 40 rear, 2 pounds more if loaded heavily. However, if I was to take it to the track I would run 30-32 front to rear.

Your ideal pressure would give you good traction and maximum tire life. The higer the better.

I do not bother with nitrogen. The volume of air in the MC tires is too small to make any appreciable difference. On large car and truck tires the valie is a little more understandable, though I still do not bother.

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Old 07-31-2013, 05:32 AM   #5
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That's still pretty hard. Try 32 or 33 front and rear. And of course you've got to have ridden several miles to warm the tires to compare. Too hard won't warm the tire enough , too soft runs too hot. Soft will warm faster. The pressure will rise about one pound per ten degrees of temperature rise.

joexr screwed with this post 07-31-2013 at 05:38 AM
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Old 07-31-2013, 06:03 AM   #6
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I have the same gen VFR and run the factory pressures. Bike handles great and I get very good tire wear. I have zero head shake at any speed. I tried running 36 in the rear and didn't like the wear.
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Old 07-31-2013, 06:08 AM   #7
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I run 40 psi front & 41 psi rear (cold) on my K75. This is the max. pressure listed on the tire itself. Metzler road demons. This is also what the very savvy guys at my mechanical shop recommend. They have three or four tires on display at their shop that have literally come apart because of overheating. They also have a chart that shows how much hotter a tire becomes at 70mph for each one pound per psi it's under-inflated. Keep in mind that I live in Phx, where the ambient temp during the summer is often 110-115 degrees; which means the asphalt is probably 150 degrees or more. (A cop once ordered a felon to get face down on the sidewalk.....the felon said go ahead and shoot, but I'm not lying down on the f'ing pavement) I check my tires once a week on my and my wife's bike. Usually they've lost 2-3 psi, but I'm comfortable with that especially if I'm not riding higher speeds. Bikes handle just fine.
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Old 07-31-2013, 06:11 AM   #8
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Eh?

Pressure on the sidewall is NOT recommended pressure , it's MAX pressure.
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Old 07-31-2013, 08:14 AM   #9
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Quote:
Originally Posted by joexr View Post
Pressure on the sidewall is NOT recommended pressure , it's MAX pressure.
Ya. BUt a good place to start. Also, unless you're running the same OEM tire that the bike came with, you should ignore what's in your bike's owner's manual, and go with what the tire vendor recommends.

BTW, because tires are a safety item the tire vendors do a good job of providing customer support - call their 800 number and ask them for their recommended settings.
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Old 07-31-2013, 08:27 AM   #10
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JEEZ, not this shit again.
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Old 07-31-2013, 08:28 AM   #11
PalePhase OP
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Quote:
Originally Posted by JimVonBaden View Post
There are several ways to set air pressure, and for various reasons. Up to the manufacturer's maximum it is generally better for tire life to run the maximum pressure you can while maintaining decent traction charactoristics. On the other hand, racing pressures often run lower for pure traction. Example, on my R1200GS I run pressures of 38 front and 40 rear, 2 pounds more if loaded heavily. However, if I was to take it to the track I would run 30-32 front to rear.

Your ideal pressure would give you good traction and maximum tire life. The higer the better.

I do not bother with nitrogen. The volume of air in the MC tires is too small to make any appreciable difference. On large car and truck tires the valie is a little more understandable, though I still do not bother.

Quote:
Originally Posted by joexr View Post
That's still pretty hard. Try 32 or 33 front and rear. And of course you've got to have ridden several miles to warm the tires to compare. Too hard won't warm the tire enough , too soft runs too hot. Soft will warm faster. The pressure will rise about one pound per ten degrees of temperature rise.
Quote:
Originally Posted by 390beretta View Post
I run 40 psi front & 41 psi rear (cold) on my K75. This is the max. pressure listed on the tire itself. Metzler road demons. This is also what the very savvy guys at my mechanical shop recommend. They have three or four tires on display at their shop that have literally come apart because of overheating. They also have a chart that shows how much hotter a tire becomes at 70mph for each one pound per psi it's under-inflated. I check my tires once a week on my and my wife's bike. Usually they've lost 2-3 psi, but I'm comfortable with that especially if I'm not riding higher speeds. Bikes handle just fine.

Thanks for the enlightenment, gents. From your comments, it sounds like maybe the shop owner's recommendation is not too terribly out of line but is heavily biased towards very aggressive riding. I think I may split the difference and go up about 3-4 psi in the back, becaus that tire was toasty when I got home from my commute yesterday, and we were only up in the high 80s yesterday.

Quote:
Originally Posted by 390beretta View Post
Keep in mind that I live in Phx, where the ambient temp during the summer is often 110-115 degrees; which means the asphalt is probably 150 degrees or more. (A cop once ordered a felon to get face down on the sidewalk.....the felon said go ahead and shoot, but I'm not lying down on the f'ing pavement)
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Old 07-31-2013, 08:29 AM   #12
High Country Herb
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I'm not a precise person. I just squeeze the tires with both hands as hard as I can. For off road use, I allow a little flex, for street use, I add just enough to where I can't flex them. From that starting point, I go up or down to find the sweet spot where the bike feels planted without being twitchy.

On my cars, I bring them to just below the point where the ride feels harsh, then adjust front to rear ratio to correct oversteer/understeer.

I completely ignore manufacturers recommendations, since I figure I know better than thousands of hours of research.
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Old 07-31-2013, 08:31 AM   #13
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Quote:
Originally Posted by joexr View Post
Pressure on the sidewall is NOT recommended pressure , it's MAX pressure.
common misconception

no, its pressure required to support maximum load,

for example the Karoo Ts on my V-strom sez (Max load 715 lbs @ 33psi) and Metzeler recommends running 41 psi with that tire on a V-strom 1000
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Old 07-31-2013, 09:40 AM   #14
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Hmm. Maybe I'm just simple. But I find a tire pressure that works for me, grip and tire wear wise, monitor it about once or twice a month, and just ride a lot more.

I find riding more and not obsessing about details is much more satisfying. Been working good this way for 42+ years and 250,000+ miles of riding.
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Old 07-31-2013, 09:46 AM   #15
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i run 36/42 in my vmax and similar on my honda fury. if my tire pressure is too low my tires start to peel in the twisties and dont last.
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