I bought tires for my Studebaker champion, may be a $1600 mistake 😅

[Matt129]

Hello everyone, I bought some 7.00-15 tires for my Studebaker Champion thinking they would be smaller than 7.10-15 tires since I didn’t understand Bias Ply tire sizes at the time and frankly I still don’t lol. These cars came with 6.40-15 and 7.10-15 tires, and I’m worried that the 7.00-15 tires won’t fit. Am I screwed? Thanks for any info you can give me.

[avgwarhawk]

I believe that is two tire sizes larger than what you have on the car. Going to fill the wheel wells and hopefully not rub the frame when turning. 

Edited August 10, 2023 by avgwarhawk (see edit history)

[60FlatTop]

Here is a '51 Champion with a fresh set of the correct size. See how it matches up.

 

I don't remember the size. It is a car I have been helping with.

 

My recollection is that a 7.00 X 15 was more of a commercial tire. 6, 8, and 10 plies come to mind. And they had stiff sidewalls. Could make for a noisy ride in a car that doesn't have much sound absorbent to begin with.

 

My Dad used to come home from work with Kodak jokes. My friend's car reminded me of the two skeletons on a tin roof Dad told about.

[Matt129]

33 minutes ago, 60FlatTop said:

Here is a '51 Champion with a fresh set of the correct size. See how it matches up.

 

I don't remember the size. It is a car I have been helping with.

 

My recollection is that a 7.00 X 15 was more of a commercial tire. 6, 8, and 10 plies come to mind. And they had stiff sidewalls. Could make for a noisy ride in a car that doesn't have much sound absorbent to begin with.

 

My Dad used to come home from work with Kodak jokes. My friend's car reminded me of the two skeletons on a tin roof Dad told about.

The tires I bought are 4 ply I think.

[alsancle]

The actual sizes that are listed don’t necessarily mean anything. Brand to brand there can be quite a difference in both width and total tire height. You won’t really know until you get one of the tires in your hands.

[Bloo]

4 hours ago, Matt129 said:

I bought some 7.00-15 tires for my Studebaker Champion thinking they would be smaller than 7.10-15 tires since I didn’t understand Bias Ply tire sizes at the time and frankly I still don’t lol.

Me neither, but I know enough to be dangerous. Tires never perfectly followed the specifications. I suspect it might be worse today due to a limited number of surviving molds.

 

700-15 is probably a size dating from the prewar era. I believe the 37 Buick Century had them. In that time, the aspect ratio was probably 100%. Maybe techniaclly 90%? In practice, it was 100%, and when the tire was new with a lot of rubber on it, more like 110%. The tire *should* have been 7 inches wide at it's widest point, when mounted on whatever rim width it was designed for.

 

(7" x 100% x 2) +15" = 29" tall

(7" x 110% x 2) +15" = 29.2" tall 

 

Let's see what some current Coker 700-15 offerings are like:

 

FIrestone: 29.29" tall

B.F.Goodrich: 29.1" tall

Lester: Not Specified

 

Something changed in 1948, and I am not sure exactly what. Maybe the aspect ratio changed for newly introduced sizes? Maybe 100%(110%) to 90%(100%)?

 

There was a change in 1965, and sizes introduced after that time are 80% or 82%. I've seen actual documentation of the 1965 change. With very few exceptions, the sizes introduced in 1965 or later end in a "5" (7.75-15, etc.).

 

If I go out on a limb here and assume (lol) that 6.40-15 and 7.10-15 were introduced between 1948-1965, and also assume they have a 90% aspect ratio, but maybe actually 100% with thick new tread, then we get:

 

(6.4" x 90% x 2) + 15" = 26.52" tall

(6.4" x 100% x 2) + 15" = 27.8" tall

 

(7.1" x 90% x 2) + 15 = 27.78" tall

(7.1" x 100% x 2) + 15 = 29.2" tall

 

What does Coker say about current offerings?

 

Firestone 6.40-15: 27.30" tall

B.F.Goodrich 6.40-15: 26.88" tall

Excelsior 6.40-15: 26.8" tall

 

Firestone 7.10-15: 28.88" tall

B.F.Goodrich 7.10-15: 27.98" tall

Goodyear 7.10-15: 29.08" tall

 

So yeah, if we are talking about 7.10-15 to 700-15, basically no difference. Considerable difference from 6.40-15 to 700-15.

 

Edited August 11, 2023 by Bloo (see edit history)

[Matt129]

7 hours ago, Bloo said:

Me neither, but I know enough to be dangerous. Tires never perfectly followed the specifications. I suspect it might be worse today due to a limited number of surviving molds.

 

700-15 is probably a size dating from the prewar era. I believe the 37 Buick Century had them. In that time, the aspect ratio was probably 100%. Maybe techniaclly 90%? In practice, it was 100%, and when the tire was new with a lot of rubber on it, more like 110%. The tire *should* have been 7 inches wide at it's widest point, when mounted on whatever rim width it was designed for.

 

(7" x 100% x 2) +15" = 29" tall

(7" x 110% x 2) +15" = 29.2" tall 

 

Let's see what some current Coker 700-15 offerings are like:

 

FIrestone: 29.29" tall

B.F.Goodrich: 29.1" tall

Lester: Not Specified

 

Something changed in 1948, and I am not sure exactly what. Maybe the aspect ratio changed for newly introduced sizes? Maybe 100%(110%) to 90%(100%)?

 

There was a change in 1965, and sizes introduced after that time are 80% or 82%. I've seen actual documentation of the 1965 change. With very few exceptions, the sizes introduced in 1965 or later end in a "5" (7.75-15, etc.).

 

If I go out on a limb here and assume (lol) that 6.40-15 and 7.10-15 were introduced between 1948-1965, and also assume they have a 90% aspect ratio, but maybe actually 100% with thick new tread, then we get:

 

(6.4" x 90% x 2) + 15" = 26.52" tall

(6.4" x 100% x 2) + 15" = 27.8" tall

 

(7.1" x 90% x 2) + 15 = 27.78" tall

(7.1" x 100% x 2) + 15 = 29.2" tall

 

What does Coker say about current offerings?

 

Firestone 6.40-15: 27.30" tall

B.F.Goodrich 6.40-15: 26.88" tall

Excelsior 6.40-15: 26.8" tall

 

Firestone 7.10-15: 28.88" tall

B.F.Goodrich 7.10-15: 27.98" tall

Goodyear 7.10-15: 29.08" tall

 

So yeah, if we are talking about 7.10-15 to 700-15, basically no difference. Considerable difference from 6.40-15 to 700-15.

 

I guess I’m just going to have to drive the car around with the tires and see what happens lol. 

[61polara]

The correct tire size for the Champion is 6.40x15.  The larger Commander and Land Cruiser used the 7.10x15 tire.  Mount one and see if it fits.  Check that the tire fits both the front and rear as well as the spare tire well in the trunk.  As the Champion is the smaller body built by Studebaker you may find that you don't have clearance to mount the rear tires because of narrow rear wheel wells for the smaller tires.  The same for the spare tire well.

[Matt129]

On 8/16/2023 at 11:14 AM, 61polara said:

The correct tire size for the Champion is 6.40x15.  The larger Commander and Land Cruiser used the 7.10x15 tire.  Mount one and see if it fits.  Check that the tire fits both the front and rear as well as the spare tire well in the trunk.  As the Champion is the smaller body built by Studebaker you may find that you don't have clearance to mount the rear tires because of narrow rear wheel wells for the smaller tires.  The same for the spare tire well.

I’m pretty sure the commanders and champions shared the same body but had different drivetrains, I may be wrong though.

Edited August 17, 2023 by Matt129 (see edit history)