Author Topic: Car Tire on a bike ( video )  (Read 22708 times)

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Offline racer x

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Re: Car Tire on a bike ( video )
« Reply #75 on: July 24, 2009, 06:12:19 AM »
  I run a very small very low powered bike . The 250cc four stroke. I have thought of using a front tire from a motorcycle on the rear to reduce drag . As it is I run the max recommended tire pressure to get the tire on a point . judging from the dirt on the tire I ride on about three inches of rubber. It looks to me like Roy has a lot more rubber on the ground . BUT he is going twice as fast .

Is the concern hear that the bike will loose control or the tire will fail?

Just out of curiosity, what tires are you running?  I would think you would be hard pressed to find a narrower tire than the 125 GP slicks





I use a 130 70 17  on a 3.50 inch rim  I was thinking of going to a 120 70 17 front tire on the rear.
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Offline Warp12

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Re: Car Tire on a bike ( video )
« Reply #76 on: July 24, 2009, 05:32:00 PM »

I use a 130 70 17  on a 3.50 inch rim  I was thinking of going to a 120 70 17 front tire on the rear.

While that tire is numerically smaller, you may find that it has an increased contact patch once installed on the rim. In drag racing, sometimes a smaller than oem width tire is used because it can spread out flatter once mounted.

Just something to consider.

Shane

Offline sockjohn

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Re: Car Tire on a bike ( video )
« Reply #77 on: July 24, 2009, 06:00:00 PM »
Just curious....read a little article recently about tire size changes when vehicle weight doesn't change.  It basically said that at normal pressures, the contact patch for wider tires doesn't get bigger (to any significant amount) because the patch gets shorter as it gets wider.  The explanation said that the vehicle weight (pounds per square inch) actually stays the same if the pressures are similar.

I found it interesting, because in my younger years we learned to run VERY skinny tires (and a little taller) on our 4x4s in the winter snow (grew up in Colorado).  We didn't get stuck near as much, and the cars would run much straighter on slippery surfaces.

Wouldn't the contact patch be more dependant on tire pressure, than tire width (assuming there's some curvature in the tread)?

I'm curious to hear what works best for tire pressures (mc tires, on the salt)....I never gave it a lot of thought, to tell the truth, just ran them pretty hard.

Regards, JimL

Jim,
Do you happen to have a link for the article?

I remember a similar discussion with Sumner about his weight formulas and motorcycles, but in the end I was still scratching my head.  I can't find the thread at the moment.

I do know that contact patch is dependent on tire diameter, taller tire has a bigger contact patch.

Offline JimL

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Re: Car Tire on a bike ( video )
« Reply #78 on: July 24, 2009, 08:31:29 PM »
It wasn't on the net...it was in one of the multitudes of trade papers, magazines, technical junk-mail....that pile up at our regional office.  It might have even been in a tire-flyer ad.  I agree with the concept that the taller tire has a longer contact patch, but on a round section tire I'll believe it gets narrower...meaning maybe the same contact (pretty close) if tire pressure is the same between the two tires (unless maybe way over-inflated?)

I am convinced that the taller tire seems to track straighter...I got a used motorhome that has 19.5" wheels, where my old one had 16.5"; the tires are really tall and very skinny...and it's a LOT less work to drive straight than the smaller, wider aspect tires were.  Of course...it's a big difference between 58mph cruise speed and 158!

This whole concept has me scratching my head, hoping to someday build a lakester and trying to figure out tire sizes.  I think I'll go with whatever I can get free or "inifo" as they say in the streets!  :lol:

Very interesting thread...still learning I hope.
Regards, JimL

Offline wolcottjl

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Re: Car Tire on a bike ( video )
« Reply #79 on: July 24, 2009, 10:49:12 PM »
It wasn't on the net...it was in one of the multitudes of trade papers, magazines, technical junk-mail....that pile up at our regional office. 


It may have been in a racecar engineering magazine - I remember an article on tire size.  I will dig through my stack sometime this weekend and see if it is in there.
Joel Wolcott
Moving to 2 wheels in 2010

Offline racer x

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Re: Car Tire on a bike ( video )
« Reply #80 on: November 05, 2009, 06:42:34 AM »
Roy, I found a photo of a pit bike you could build over the winter
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