How to Measure for new tires/wheels
 

What is the best way to measure how wide/tall of a tire wheel combo I can fit in? I'd like to have as beefy as possible on 17" rims. Any suggestions on how to measure, and or suggestions on what size? How to measure for proper backspacing?

Body will come off frame in a couple months, and it will have disk brakes; need at least 15", so might as well bump up to 17". Body color change too, to something a bit more menacing.

Thx, Scott.

http://img235.imageshack.us/img235/4268/img29023sg.jpg

WHY?
 

Its a nice looking car. Other than the brakes why would you want to change anything else?

Here is a link with a diagram showing how very easy it is to measure backspacing:

http://earlywheel.com/products.html

Probably the best way to start is to measure your current wheels, find out the rim width and backspacing on what you have now. Put the car up on blocks, one block under each tire. This gets the car up high enough so that you can crawl under it and measure clearances. You will want the car to have its full weight on the suspension.

Turn the front wheels from lock to lock and measure from the tire/rim to the sway bar, etc. Use a straightedge (yardstick, etc.) and a measuring tape. Measure everywhere inside and outside, measure a lot, double check everything. Remove the wheels (one end of car at a time) and check clearances (lay straightedge across brake drum), keeping weight on the suspension again (wood blocks under brake drum, jack stands under rear axle, etc.). Be careful.:eek:

By measuring your current wheel/tire combo you can easily determine how much room you have to go wider inside and out.

Go here: http://tirerack.com and look up different tire sizes that you are considering. They will have listings for the different tires with measurements of the section width (sidewall to sidewall) on a 'measuring rim' as well as tire diameter.

The section width will change slightly if the tire is mounted on a wider or narrower rim, usually the change in section width is a little less than half the rim width increase or decrease from the 'measuring rim' (9.5" section width tire on a 9" 'measuring rim' will become a 9.9" section if mounted on a 10" rim). Click around the Tire Rack site, there is a lot of info you can mine.

Low-profile tires of the 17" variety will use rim widths very close to the section width, unlike the skinny steel wheels you have now where the tire section width is a lot wider than the rim. Take this into consideration.

All rims are actually 1" wider approximately than the 'advertised' rim width, all rims are measured bead-to-bead by manufacturers. The rim lips past the mounting beads add the extra width.

It's not that hard to figure out, but you'll have to do your homework. Make sketches and diagrams, you'll need to keep track of everything as you go.

Good luck.:cool:

<<Its a nice looking car. Other than the brakes why would you want to change anything else?>>

Thank you for the compliment.

I want to have fun with this project, and not worry too much about sticking to original for original sake. Some people stew about it, but I think I'll be doing it in good taste (mine ;) ).

It has non-original motor & tranny that leaks all over and is under powered (2bbl & burns oil). Those get replaced without question. If they were original, it would be a rebuild of course. Tranny has already been converted to TH400, so I think I can drop in a 200-4R on that tranny brace and have overdrive for a buttery ride on the highway past the gas stations. Rear end leaks so it needs an overhaul, and I'd like to put in posi to help manage the new found power.

I'd like the brakes to be updated to stop along with the rest of the cars on the road. The wheels need to be at least 15, and I like the look of 17, I think it will look nice on this car. Suspension gets tightened up and more robust.

I want to paint it my favorite color for this car and I just don't know what it is yet, it might stay blue, but I doubt it. It will be something to capture the vintage though, as well as give a hint of the powerplant.

The only thing visually that will not be original will be the wheels. The color will probably come from the '61 Pontiac choices. I have new stock springs in that picture, but the I'm going to drop the front end 3/4".

Nothing that any Pontiac person can't reverse if I ever pass it on, then they can have fun with it.

I'm really looking forward to my project.

Scott.

b-man-

thanks for the info! super helpful. tirerack has tons of technical links and i think i'll be able to do this accurately.

it's always a bonus when one of your posts comes bouncing along. good advice too.

Scott.

Summit sells this tool that is a Wheel and Tire simulator. Part #PHP-01201, cost $90.00 though. It simulates bolt patterns, wheel widths, backspaing, and tire profiles before you shell out the cash for the real deal.