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Author Topic:   roll out question
petordragon
Dirt Maniac

Total posts: 167
posted March 09, 2005 05:11 PM  
I'm thinking the roll out of a tire off the ground does not mean much if you run low pressures. Tires squat shortening the distance from the wheel shortening the rollout. Would it not be better to get the rollout from the radius of the wheel from center to the ground multiply it by two then by pie (3.14) to get the acctual roll out?

Eljojo
Dirt Forum Champ
Total posts: 968
posted March 09, 2005 06:58 PM  
Take off your belt and hold your pants up with one hand and let the belt hang straight down to the floor. Is it any longer or shorter than when it was around your waist? Why do you think that the tire tread would be any shorter whether it's round or oblong or cut off the tire and put in the driveway?
Put your belt back on.

Bulwinkl
Dirt Full Roller

Total posts: 37
posted March 10, 2005 03:06 PM  
maybe check out a drag car they run low air presser watch what happens to there tires under aceleration in slow motion )))maybe we should run even a smaller tire

akadirtracer7
Dirt Freak

Total posts: 217
posted March 15, 2005 05:36 PM  
Measuring the roll out gives you something to go by . If your tires are the same and act the same when their spinnnig I'm sure theres some amount of exspansion going on. The tires will build heat and pressure and change anyway .So do it the easy way measure the roll out.Don't need a calculater for that.

Blackgold
Dirt Full Roller

Total posts: 71
posted March 15, 2005 08:28 PM  
Petrodragon, I think you are probably right that the roll is less when the tire squats because of lowered pressures. If you want to go to the trouble to find out how much it changes, you can mark a spot on the ground and mark a tire and then roll the car until the tire rolls 10 turns and measure how far it moved from the 1st mark on the ground and then change your tire pressure and do the measured roll again and see if there is a difference in distance. Some say that radial dot tires don't change due to the radial construction. I don't know for sure what you will find here. I have a sprayer that takes a mph and distance reading with a magnetic sensor on a wheel and it changes if I get a lkow tire on that wheel, but this is a bias ply tire. I also know that we played around with air pressures when we raced, and I always thought that we were mostly changing scale wts. but we may have been changing stagger some also. Never thought of that, just knew that changing rear tire pressures would adjust car to different track conditions. Ed

petordragon
Dirt Maniac

Total posts: 167
posted March 16, 2005 10:46 AM  
tnx for the possotive thought black gold. I do know air pressure greatly effect the wear of a tire and I am thinking that alot of the tire wear is from the belt on the tire not turning at the rollout it was designed to turn at.

sidebiteu259
Dirt Full Roller

Total posts: 56
posted March 16, 2005 08:21 PM  
Guys dont over think the concept. Call a Goodyear or Hoosier tech and ask them what they think about the theory. There the ones that have the honest info.

petordragon
Dirt Maniac

Total posts: 167
posted March 17, 2005 11:02 AM  
I just figured you guys to be a little brighter than the guys at goodyear or hoosier.

sidebiteu259
Dirt Full Roller

Total posts: 56
posted March 17, 2005 11:15 AM  
Brighter then the guy who designed the tire and knows it inside and out.

petordragon
Dirt Maniac

Total posts: 167
posted March 18, 2005 11:35 AM  
LOL

petordragon
Dirt Maniac

Total posts: 167
posted March 21, 2005 09:15 AM  
it was a joke side bite.

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