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Author Topic:   Rim width / tire width and tire wall height?
Machinah
Member
posted February 05, 2002 04:26 AM
I need to find opinions on tire sizes. Mainly I'm not sure what wall size to use. My limitations/choices are... RIM- 15x7 or 15x8... TIRE- no better than DOT 70. My track is 1/4mi. w/decent banks, clay/dirt, a little rough. Many classes race this track so conditions can changea good bit throughout the evening. I personally think that a P225/70 may be what I need. I already know that I must get the tread width as close to rim width as possible, but don't know if I should use a 235 instead. I want to make sure that my wall flex is minimal.


autoshop
Member
posted February 05, 2002 09:26 AM
I would run the wideist wheel and tire that your rules will allow.....As far as the height,the 225 is not bad,the question is,what do you want in relation to what you have?? If you want a lower gear ratio(higher numerically)(equals higher rpm) use a shorter tire.....If you want a higher gear ratio (smaller numerically and lower rpm) use a taller tire. One inch of tire circumfrence is equal to about .072 gear ratio and about 1.1 MPH.........In general,I would say that the shorter sidewall tires perform better and more consistantly


racer17j
Member
posted February 05, 2002 11:36 AM
if you have the gear to run a shorter tire like snowman says go ahead and do that we are requireed to run 205 70 or 75 tires i run bolth sizes work good for me i don't like realy tall tires if you think about it yes you have more sidewall to flex more rotating weight and shorter tires are usually cheaper and ez to come by and less likely to get cut if you get in a little fender bender


Machinah
Member
posted February 05, 2002 03:55 PM
Thanks... I think I will probably use either the 205 or, more likely, the 215. I like the better contact patch for accelleration, but on a short 1/4mi. track I'm after better control in the corners and flex is my major concern.

[This message has been edited by Machinah (edited February 05, 2002).]

ryan
Member
posted February 06, 2002 12:34 AM
We have about the same size track and the same tire rule as you and most of us use either 255/70/15 or 235's. I have never lost a tire due to it rolling off the bead. Our track is very unpredictable some nights smooth and other nights its extremely rough. Most of the time it starts out very muddy and ends up shiny enough you can almost see the reflection of the car. We set our pressure at about 18 psi at the lowest(w/tubes)


Machinah
Member
posted February 06, 2002 05:09 AM
Ryan, have you had any experience with the lower tread/wall ratios? What width rims have you used with different sizes? How do they compare? I don't want to loose too much accelleration off the turn, but if handling in the turns is better with a shorter tire I can make the turn faster and already have momentum out of the corner, even though I don't have as much accelleration. I'm leaning toward a shorter tire, but my drag racing mentality is looking for someone to convince me otherwise. Thanks for all the help everyone.


Machinah
Member
posted February 06, 2002 05:28 AM
Thought I would elaborate on why I'm having trouble with this decision... I feel that handling and traction are going to make the difference between my being in the front of the pack or somewhere in the middle. This aside from safety is my top concern because it isn't going to do me any good to have a fast motor if the car dosn't turn as best as it can be. I know that a shorter wall means less flex and more control. I also know that a taller height and wider width means more traction. I am not sure how much of a snowshoe effect I will get from wider tires on loose dirt (major slide). When I look at the sprints, what you have is a much lighter car with fairly narrow tires on the front and contrasting wide tires on the rear. These sprint cars are obviously not too worried about flex for their wall heights are fairly tall. The lighter sprint car has to cause less flex in the sidewall. The wide rears of the sprints must have some kind of snowshoe effect. The narrow fronts must be for getting through the loose dirt to get a bite on the hard-packed clay/dirt below. I have to run the same size all the way around so I know that there will be a trade-off. I believe if I start off with the right tire trade-off, I will have a much easier time tweaking the other factors in handling.


racer17j
Member
posted February 06, 2002 11:08 AM
mach don't make this more complicated than it needs to be you will only confuse yourself more. go with an 8 in wheel with a 70 series tire. it's just like bobby and tony say (wider is better ) lol as for what roll you have go with what ever will fit your gear best. as i said before i don't like the taller tires but would not be afraid to run them if i had to i just don't like to have to cut my wheel wells all the way to the top of the fenders to make room for the tires. back when we had just a dot tire rule no size we ran 215 70 firehawk ss those where the best thing on the dirt but we never ran anything bigger than that. if you want to see what effect different tire have get a copy of stock car mag i'm not sure what month it was but they had a deal a few months ago about tire(footprints) and how to set a deal up that you can do to test your tires and see what they do under load i will look tonite and see if i can find it to get the month for you. like i said don't look to far into stuff and don't try to compare your 3000# stocker to a 1200# sprinter there are different animals


ryan
Member
posted February 06, 2002 12:09 PM
As far as I am concerened the more tread that hits the dirt the better off you'll be. Go for wide tire 8" rim 60 or 70 series, depending on if you need more gear or not


Flatlander
Member
posted February 06, 2002 04:06 PM
Thanks alot, I really apreciate all the help.


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