Tire size with Columbia rear end
 

I have a Columbia rear end to install in my 1947 Ford convertible & want to put radial tires on the car when I do the install. It has a 3.78 main gear. The car currently has the stock 6.00 x 16 inch bias ply tires. Is there an advantage to changing the rims to 15 inch as came on the Mercury's in 46 - 48 with the Columbia. I would like to run a little wider tire than stock. What rim/tire size are you using & what are your recommendation's. Thanks for your input

Re: Tire size with Columbia rear end
 

The advantage to changing to 15" inch rims is tire selection.. There are way more options for radial tires in the 15" inch range.. I stayed with my 16" inch rims strictly because I only had money for tires, and no money for new rims.. the stock rim is about 4" inches wide.. I use the Bridgeston Ecopia radial in 195/80R/16.. it is equivalent to the 6.00 x 16.. I actually like the look of the stock skinny tires.. :p

Good Luck WALT

Re: Tire size with Columbia rear end
 

The 15" wheels/tires would be a nice addition to your car. Radial tires would also be a plus.

I would suggest that you use '57-66 Ford F100 wheels, they will be in the five inch wide range. They are a direct fit to your car and your stock hub caps will fit perfectly, you will have to purchase 15" beauty rings.
Be careful buying the 15" wheels, the early 15" wheels are narrow, in the 4.5 range and will not have the DOT spec's stamped into the rim. The later model '57-64 F100's will generally have the spec numbers stamped into he rim.
The '67-91 F100-150 wheels will also work except they have external hub cap knobs like the '49 and later Fords/Merc.s.

Re: Tire size with Columbia rear end
 

Vintage & Blucar , thanks for the input , how wide of a tire do you think would fit on the 15" F100 rim & still be easy to get in/out of the front & rear wheel openings

Re: Tire size with Columbia rear end
 

I'm running 235/75/15 American classic wide white wall on the back of my 40 coupe. The columbia rear is 411 gears and the rims are 5" wide merc rims all the way around and 205/75/15 on the front so I can use the 40 caps and the speedometer is dead nuts on by my gps. If this helps.

Re: Tire size with Columbia rear end
 

Don't go too wide.. steering sucks on wide front tires without power steering!

I am using the stock 4.5 wide rims with tubeless radials... no issues holding air or keeping the tread side on the pavement! I had one wheel that had a a tiny 1/4" crack alongside the wide part of the wheel.. (71 years old).. but my pro-welder friend welded it up.. I use that as my spare.. It is still holding air after 6 months..:D

Re: Tire size with Columbia rear end
 

On my 39 convertible I am running a Columbia 378 with 15 inch wheels and it does fine with the radials . I am using a 70 series tire.

Re: Tire size with Columbia rear end
 

In the later Ford pickup wheels you will find them in 5" and 5 1/2" widths. If you run a tire as big as a 235X75 on the rear use the 5 1/2" rim. Do not go wider than the 5" on the front.

Re: Tire size with Columbia rear end
 

Some people like the big & little look, I have never liked that look. I like the same size tires front and rear so they can be rotated to improve tread wear. On a car I think P235/75R15 is to large, that is unless you want the "Rod Look" in lieu of a traditional factory look.
The recommended wheel size for a P235/75R15 is 6-8.5, where-as a P205/75R15 is 5.5-7.5.. The diameter of the 235 tire is 28..91", which is very close to the average 600x16.. The diameter of the 205 tire is 27.11". All of the tire sizes are per Coker's catalog.
From my point of view the Columbia with 3.78 ratio would work well with the P205 tires. One thing you should keep in mind when considering over-size tires is the brakes on your car. The braking power of the '47 brakes are marginal at their best in today's traffic, adding over-size tires (P235), could "INCREASE" the stopping distance. Think of the tires as being large flywheels rotating down the road.
Lots to think about when you start messing with "Henry's original design.

Re: Tire size with Columbia rear end
 

When I take the last three sentences in their complete context, I think you mean "increase" rather than "reduce" the stopping distance. I hate to be pedantic, but I just want to make sure I understand what you are saying.

Re: Tire size with Columbia rear end
 

Thanks for all the comments above , what I can summarize is: 15" rims , maximum rear tire with is 235/75 & front 205/75. Rim withs to use is 5 to 5.5" wide.
Tj - what years do you consider " late ford rims " ?
Blucar - I agree about the brakes , they have already been upgraded , want to keep car as stock looking as possible but enjoy driving the cars long distance , so upgraded brakes , tires does not take away from the car but give that added safety when travelling at the higher speed.

Re: Tire size with Columbia rear end
 

Thank you for pointing out my use of the wrong wording, I have corrected my comment.


As I pointed out in my comment (s) about tire/wheel size, the recommended wheel for a P235 tire is 6-8.5", the use of a 5-5.5" wheel will pinch the bead in, thereby making the tread crown and reducing the tread contact to the road.
Many people are not aware how important wheel size and tire inflation is. A tire that has poor contact to the road, from either wheel size or tire inflation will show up in tread wear... Wear on the center of the tread will indicate over-inflation, and/or wheel to narrow. Wear on the outer shoulder of a tire will be a sign of under-inflation and//or to wide of a wheel.


I recently encountered a motorist that had a huge problem with a Class C RV on a Ford F550 chassis.

He had the original steel wheels replaced with alloy wheels, for the look. While traveling down the road the right rear lug bolts sheared off, causing the two wheel to come off of the differential hub.. Severe damage to the body occurred.
The damage was repaired and new lug bolts/alloy wheels were installed on the effected side. A few months later the right outside wheel came off, lug nuts came loose.
The problems were two fold; The alloy wheels were not weight rated for the axle weight. The lug bolts were designed for the original Ford drop center/coined wheels.. (Coined wheels nest together, where-as alloys don't) The coach was overloaded on the back axle by 3,500 lbs, a result of the owner carrying to much stuff.

Re: Tire size with Columbia rear end
 

I am presently looking into 15” tires.
Here is a good HAMB thread about wheels.

https://www.jalopyjournal.com/forum/...l-tech.115542/

John

Re: Tire size with Columbia rear end
 

Great thread John , thanks