[bizkit075]

Does anyone know what is the biggest size tire i can fit under a stock wheel-well for a 72 chevelle. Im using BFGoodrich radial t/a's and I think 275-60-R15 are what im going to use, but if i can go bigger i will. Im using a 15 inch wheel, and i dont have a good understanding for backspaceing, please help!!

[65galaxie500]

well the tire size you are considering are going to be 10.83 inches wide, the total tire height will be about 28 inches. so if you have about 12 inches WITHOUT rubbing under the wheel well ( lets say you do just to give you an idea and that you are using a 15x8 inch wheel but you need to figure back spacing) you want to get the tire centered in that 12 inches so lets say from the front of the hub to as far as you can go WITHOUT rubbing on any thing to the back is about 6.5 inches, so a 5.5 inch backspace would be safe for that. your tire would bulge away from the wheel approximately a little less than 1.5 inches on both sides so the inside of the tire would be meeting the maximum you could go. which would mean from the front of the hub to the the outside edge of the tire would be 4.33 inches, 6.5 inches + 4.33 inches gives you 10.83 the width of your tire. the backspacing is measured from where the wheel meets the hub to the out side edge of the wheel. tire size can be determined like this...275/60 r15,
275 is millimeters, to convert to inches just divide this number by 25.4 (# of millimeters in an inch) = 10.83inches, the 60 basically means that the height of the tire from edge of rim is 60 percent of the width of tire so 10.83 X 60%(.60)= 6.5 inches so from edge of rim to top of tire is 6.5 inches so from bottom of tire to top of tire =6.5 + 6.5 + 15= 28 inches
i hope i typed this so you can understand it (not to incenuate that you are slow, just reading back over it i barely understood it.) i just cant think of a better way to explain it.

[bizkit075]

Thanx alot for the advise, so im going to need 15 by 8s, with 5.5 inch backspacing correct?( for the 275/60/15's)

[65galaxie500]

not necessarily, you need to measure from the front of the hub to the inside of the wheel well to see how much clearance you have, with that, it should give you an idea of what backspacing you can use, for instance if you have about 7 or 8 inches from the hub to the back then 5.5 backspacing will probably work the best but if you have less than that you are going to run into problems. if you have enough room for that tire to fit then an 8 inch rim will fit. if you have less than 6 inches from the hub to the back then you can put a deeper rim on because the backspacing is shallower. the 5.5 inch backspacing means that from the front of the hub to the back edge of the wheel is 5.5 inches, the tire will protrude from that another 1+ inches so you have to take that into consideration. on my car i have 255/70 r 15 on 15 x 8 with 5.5, i have the room to accomodate but its very close, when i turn a corner they sometimes rub on the exhaust pipes, so you need to take careful measurements, you dont want the tire rubbing on either side. there are sites out there that explain things better than i

[65galaxie500]

http://www.afswheels.com/v2/content/Default.asp?Page=96


this site might help