Doing some work on a '40 Buick coupe and want to go with a wide rear tire. Is 1/2" enough room between the rear tires and the frame or will they rub? The car has radial tires on 10" wheels and parallel bars with coil overs. I know they'll "bulge" a little where they meet the pavement, but what about at the top?
Sounds too close. Put the back frame up on stands; then jack up one wheel into the well, and let the other side hang. That should be a good test just to start with.
If i had a half inch of room on any of my cars i'd put bigger tires in there. I usually like .050" but to be safe, 1/4". You have a panhard bar to stop the rear end from shifting sideways, right?
Ditto on this it will simulate going up a curb approach/cornering, etc. and will show you how much you can get away with.
A panhard bar locates the rear side to side ,but it pulls the rear closer on one side than the other as the wheels travel up and down.
I built a 39 Pontiac that we have 1/2" between the tire and frame. I prefer to have an inch but the owner wanted as big a tire as possible. It does rub slightly if your turning up a drive or something that loaded one side and unloads the other, in normal driving it's fine. Big issue for your car I feel is the 4 bar, our Pontiac had leaf springs. I ***ume you are running a panhard bar. If it is short like a lot of kit bars that mount to the pumpkin I think you'll rub, those short bars can move the rear side to side quite a bit. A sway bar will help keeping the loaded/ unloaded "tilt" of the axle and you could adjust the panhard bar with slightly more clearance on the side opposite the frame mount of the bar while the bar is parallel to the ground. A panhard bar gets effectively "shorter" as it moves up and down from parallel.
Bill Orourke[deceased] from the original Roadster Shop in Elgin Il taught me a trick that works. If you can get your fingers in between the fender, or inner fender, and the tire, your good to go. It works out to 3/4 inch more or less.
I also use the finger method......I have fat fingers so it works out to 13/16".... I have run them closer. We have a 40 Buick here at the shop and set it up with an 1" to the inside and a 1/4" to the outside but this car has an IRS so it can only move in. How did you get a 10" wheel in there?
I thought i was the only one to use the finger method. I can get a finger between the frame and tire on my '46 chevy; same on the fender lip. I had to make a longer support rod for the bottom of the fender to get a finger in there. i have never rubbed either side.
Which is exactly why I use a Watts linkage. Panhard bars are at best a poor compromise for preventing lateral movement in a rear end as they travel through an arc and do not maintain a constant axle location. A further factor that has not been mentioned is end play in the rear end. 8 3/4" Mopar rear ends are notorious for this and 1/2" clearance is absolutely not enough. When the cords show through on your inner rear tire sidewalls you'll figure it out....
Big gloves? Yep, it swings in an arc, but in most hot rod application with 4 1/2" of travel and a properly designed panhard bar that is level at ride height and as long as it can be we are talking about an 1/8" of side to side movement. Still waiting for someone to prove that watts link is a far superior lateral locating device on a car with street tires to make it worth the extra moving parts and packaging problems. I still want to know how the OP got a 10" wheel under a 40 Buick. We have a 245 on an 8" wheel, it would a take a 255 at most which is 10" wide but a 10" wheel is 11" wide. The stock sheetmetal is further inboard than the frame on these cars so that will be the first point of interference.
The question was, Is 1/2" enough room between the rear tires and the frame? With the body mounted, most cars have inner fender panels hanging to the outside of the frame rails ane even below the frame rails. With that in mind that 1/2" has become almost 0 clearance. Just a thought.
The Jalopy Journal
