Tyre pressure and air intake - Kawasaki Vulcan Forum : Vulcan Forums
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post #1 of 12 (permalink) Old 01-25-2012, 03:15 AM Thread Starter
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Tyre pressure and air intake

Hello all,

Just thought I ask advice there about the "usual" tyre pressure.
The kawa booklet recommends 28F and 32 R (psi) for a rider about 82 kg
I was told to have 40F and 42 R...?
About the air intake, is it better to have warm (hot) air going to the carbies
or cooler air...? (The intake seems to be just between the cylinders)
I believe the bike is going better in the morning when it is still around 20deg
when I go home and it has been 35 c all day the bike does not seem to run the same...
Any advices?
Thanks
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post #2 of 12 (permalink) Old 01-25-2012, 03:23 AM
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Fr, low pressure will eat yor tires in short order. Many of us run ours at 40+psi with no problems and handling is actually improved.
Cold air is denser and has more oxygen per cubic centimeter therefor will provide better combustion.




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post #3 of 12 (permalink) Old 01-25-2012, 09:09 AM
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Running tire pressures recommended by the bike manufacturer is designed, in my opinion, to get you to buy more tires more often. Actually, those low pressures tend to give a cushier ride at the expense of tire life and handling. Check the sidewall of the tire. It will show a recommended cold tire inflation value. I have talked to several tire manufacturers who recommend running the tires at the pressure shown on the sidewall. They all said that it provides for much long tire life and really improved handling. Low tire pressures create very high sidewall temperatures due to the excessive sidewall flexing, increasing the chances for what they call "catastrophic tire failure." We call it a tire blowout. Could make for a very interesting moment on the road. And riding in the temperatures you mention (35 Deg. C) only greatly adds to that.

I also agree, cooler air is denser and brings more oxygen into the engine for better combustion. It will run a bit leaner that way, probably a bit peppier. Hot air is less dense, with less oxygen in it, resulting in a richer engine running condition. Should result in less power and higher fuel consumption.

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post #4 of 12 (permalink) Old 01-25-2012, 10:39 AM
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Ditto to both the posts above. I run 38-40 psi in both tires.

I guess its due to the small size of motorcycle engines. But you notice the change in performance from temperature variance more on a bike than you would in a car. Also, you are both literally and figuratively closer to the machine on a bike. Cars have plush seats, fancy transmissions, radios, sound dampening material, etc. that all separate you from the machine itself. This makes it so that you don't notice minor performance changes so much.

I don't know if you have any high mountains around your area, but elevation can cause the same effect as high air temps due the air becoming less dense. So your bike will be a real beast at sea level on a cold crisp morning. But if you are riding through the mountains on a hot steamy summer day, it may be a bit of a dog. With a programmable fuel computer you can try to compensate somewhat, but unless you can find a way to install a turbo, there is no getting completely around this issue.

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post #5 of 12 (permalink) Old 01-25-2012, 06:56 PM
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I ran into a problem this fall on a road where there was some unevenness going the direction I was traveling down the road. I had 35-36psi in the front tire and for a moment my tire seemed to fallow the raised edge. From that time on I have kept no more than 32psi in the front tire. 35psi in the rear tire. The stock tires don't impress me when it comes to traction or ware.
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post #6 of 12 (permalink) Old 01-25-2012, 06:57 PM
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Check my tires before I head out on a ride, when they are still cool. Run 40 rear and 36 front. Get better wear and handling from my personal experiences.

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post #7 of 12 (permalink) Old 01-25-2012, 07:16 PM
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After running different pressures on different tires, I currently run Pirellies at 40 rear 38 front to get longer wear. I contacted Pirelli on tire pressures and one thing they said was "We always suggest that running higher pressures (up to the max as stated on the sidewall) will increase the life of the tire with no adverse effects." after 7,000 miles on the Pirellies there is still alot of tread left....I ran Bridgstone g702,703-series before and was happy with those as far as handling but wanted more mileage.This is my first experience with Pirelli's but am happy so far
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post #8 of 12 (permalink) Old 01-25-2012, 08:06 PM
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I run 36 front, 40 rear; my Kendas still look very good after 5,000+ miles. With the higher pressure, the front can have a tendency to tramline, meaning more eager to follow road imperfections as described by simon. I have not found the tramlining to be that bad at all; better than with the lower pressures. If you are riding two up a lot like I do, keep the rear above 40 psi; even solo, my carcass weighs in at 275. Handling with the higher pressures is a ton better to me than at Kawa's recommended pressures.

When air is compressed, it heats up (diesel engines run in this manner). Therefore, if the air is cooler to start with, it will be cooler when compressed. Add to that better air flow for even better combustion. A piston on its down stroke with intake valve open is an air pump sucking in the air; the easier the air flows in, the less parasitic power loss experienced by the engine. Add cooler, denser air to the less restricted flow equation means more power. I added the K&N to the stock air box and felt slightly more mid-range and top end with a more eagerness to rev.

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post #9 of 12 (permalink) Old 01-25-2012, 10:07 PM
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I run 40 psi on my Metzlers.

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post #10 of 12 (permalink) Old 01-26-2012, 08:22 AM
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Quote:
Originally Posted by mdsimon80 View Post
Frenchy
I ran into a problem this fall on a road where there was some unevenness going the direction I was traveling down the road. I had 35-36psi in the front tire and for a moment my tire seemed to fallow the raised edge. From that time on I have kept no more than 32psi in the front tire. 35psi in the rear tire. The stock tires don't impress me when it comes to traction or ware.
First, I think every rider should do what they feel is best and safest. After all, its my bike and my ass on the line. So if I'm going to screw up, I want to do it on my own terms. However, I can't see where higher pressures will cause a tire to track on a groove worse than lower pressures. Around here we have what people call "tar snakes". These are places where the DOT has "repaired" cracks in the interstate by pouring tar into the cracks. They look like long black snakes all over the concrete. Bikes are really bad to track along these snakes sometimes. Especially if they are running in the direction of travel. I've had it happen with both low and high pressures in my tires. Its a little disconcerting for the bike to suddenly veer off on its own path. But usually you can just ride it out. I can't say that it is worse or better with lower pressures. Anyway, that's my two cents on this.
Cheers!

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Torque is the source of all good things.
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