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<  General Scootering  ~  Are you Over-Inflated?
Mojo Willy
PostPosted: Tue Aug 16, 2005 1:57 pm  Reply with quote
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Sorry about the double-post but this is (non-Sava) tire trivia that concerns me...

The scuttlebutt on many of the MC discussion groups (and they are ALL bona fide engineers) is that good MC tires, like Avon Venoms, Metzeler's or Dunlop Elites should be run at about 5 psi higher than the manufacturer's "recommended" pressure, some go 8-10 psi over. These are tubeless tires though so, even if true, it may not apply to our little do-nuts.

Why the tire companies don't know their own tires remains a mystery. The over-inflation is supposed to give you better traction and handling, better braking, better gas milage, reduced blow-out potential, more tire life and improve your sex life. Naturally, I've been over-inflating with high expectations.

RANT: I've read that if everyone in America kept their car tires inflated to minimum normal, it would save billions of gallons of Iraqi gas and prevent thousands of deaths on the road (not to mention preventing all the Ford Explorers from rolling). I can't remember the exact fuel saving was, but it was SEVERAL TIMES what we will reap when we destroy the "Artic Reserve". I was listening to Click and Clack and found out that 90% of drivers have no clue what their tire pressure should be. For one thing, you can't even FIND IT on the tire without a microscope. Seems like it should be in 2" letters. Secondly, there are a lot of bad air machines and bad tire gauges.

Mojo Willy
working on answers to life's persistant questions...
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Matty
PostPosted: Tue Aug 16, 2005 3:38 pm  Reply with quote
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Mojo Willy wrote:
. For one thing, you can't even FIND IT on the tire without a microscope. Seems like it should be in 2" letters. Secondly, there are a lot of bad air machines and bad tire gauges.


Should be pointed out you DON'T go by what's printed on the tire, that's the tire manufacturers maximium rating. The same tire can be on many different vehicles requiring differnt pressures. You have to go by the vehicles recommended pressure which should be in the manual or stamped somewhere on the body.

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nate
PostPosted: Tue Aug 16, 2005 4:06 pm  Reply with quote
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Doesn't overinflation give you _WORSE_ traction, which would then affect braking?

Part of the explorer deal was that if you inflated them too much, suddently the vehicles got a bit tipply. (Surprise!) So the vehicle manufacturer was saying that you should run them relatively low (not corresponding to the numbers on the tire) and that was where the issue came in- too much load on the sidewalls now.

If you increase pressure, the 'contact spot' on the ground gets smaller. This is going to lead to less friction, which is where the increased mileage gets you- but you also tend to get less friction, which is where the whole "lack of stopping ability" comes from. Handling is kind of a mixed bag, because obviously a very underinflated tire is going to handle like crap, but if you overinflate, you're going to be riding on incredibly hard wheels that will tend to jump and skitter with the least provocation.

If you're in a super performance vehicle, you're going to treat your tire pressure as a variable for the conditions- which is why Humvee's have the centralized tire inflation system- hit concrete and pump up the inflation, hit sand/ice, and decrease it so you have better traction. (But crappier mileage, and sluggish handling.)


And when we talk about "manufacturers reccomendation", keep in mind that they are most likely talking about "VEHICLE manufacturer's reccomendations", which is not the number stamped on the tire. The number stamped on the tire SHOULD be the engineering load that the tire can handle, purely from a pressure standpoint. The number that the manufacturer reccomends is a much lower number that they feel is a good compromise between stability, handling, mileage, etc- so as to limit their liability in incidents. (Obviously Ford ran their number a little too low in this situation.)

So you probably don't want to be running your bikes at 35PSI or anything, or you're going to run into issues if you ever need to make a quick turn or stop.
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Jeff
PostPosted: Wed Aug 17, 2005 4:58 pm  Reply with quote
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I inflate for riding two up. It feels a bit squirrelly when I'm solo, but not too bad. It really makes a difference in smoothness whith two on board. I'm at something like 32psi in the back 25 in the front.
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Mojo Willy
PostPosted: Wed Aug 17, 2005 6:30 pm  Reply with quote
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That's interesting Jeff. I think my P200 feels best with 25 psi front and 32 psi rear. The smaller bikes like good pressure but only about 20 front and 25 rear. I hate that mushy dull ride when you are too low.

I think a guy could win the slow ride (and do better in the other races as well) in the gymkhana by going down to 10-12 psi. I wonder if anyone has done it?

Thanks for the comments

MW
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Moses
PostPosted: Wed Aug 17, 2005 6:40 pm  Reply with quote
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Mojo Willy wrote:
That's interesting Jeff. I think my P200 feels best with 25 psi front and 32 psi rear. The smaller bikes like good pressure but only about 20 front and 25 rear. I hate that mushy dull ride when you are too low.

I think a guy could win the slow ride (and do better in the other races as well) in the gymkhana by going down to 10-12 psi. I wonder if anyone has done it?

Thanks for the comments

MW


I'm sure someone has done it, but he or she may not have known it at the time.

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