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1926 Studebaker Big Six - tire size


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Hello Guys, I am struggling to select the right tire for my 1926 Studebaker Big Six, EP series, Sport Roadster. It uses 20” full disc wheels. It seems to be 6.00/20, but there are many different options and widths in Coker Tire, that it is unclear to me if this is right. I intend to use black wall tires, I believe they are more correct for the period. Thoughts?

thanks, JRA

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I believe the original tire size was 30"x5" for your car, although you may want to put on something a bit wider unless you are going for authenticity. As far a wide whitewalls vs blackwalls, that is a matter of preference.  I think you are right that blackwalls were more correct for 1926 but it's up to you how you want your car to look.  When I was deciding for new tires on my 1923 Light Six, I just did a little Photoshop work and it gave me the answer.

Scott

Blackwalls.thumb.JPG.7a0c6108422fff11873d0ea2d790a4a6.JPG

Whitewalls.thumb.JPG.ba7afbd7cc842a57ce47c88d89603dd2.JPG

Edited by Stude Light (see edit history)
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Thanks, Scott. I am really thinking on black walls. What is the comparison for 30”/5, is it the same as 600/20” ? 

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In the day, tires were measured with the OD (height) and the width.  The rim size was calculated as: Tire OD - (2 x Width).  So the 30x5 would have a 30" height, 5" tire width and a rim of: 30" minus (2 times 5") = 20". The 600/20 would be a 6" wide tire and 20" rim. These are all very nominal dimensions.  Based on tire specifications from Coker and Universal Tire websites, I would estimate that the actual tread width on an original 30 x 5 (which aren't available) is about 4.00 - 4.25" and on a 600/20 is 4.25" - 4.75".  So for authenticity, I think your choice of 600/20  blackwalls would be a good one.  FYI - Blackwalls was my choice too.

Scott

 

 

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I really like this forum, helps me to think and investigate further. Maybe the answer was closer to me. Based on the comment made by starlightcoupe I have researched in more details the books on my shelves. The service bulletin of May 10th 1926 describes tire sizes, see picture attached.

I need to confirm the production date of my car on the engine, to ensure the right tire. The engine number is EP39841, closer to the end of production run in July 1926.

 My car is a sports roadsters, so I believe it is 120" wheelbase, but I also need to check.

The question is around the rim width of 5" of my the disc wheels in my car, what would be the best option? Checking Universal Tire, there are two options from Firestone Champion: 600/20  (suggested rim width 3"-4" ) or 650/20 (suggested rim width 3.5"-4.5" ). 

What do you all think?

Thansk, JRA

 

StudebakerServBulletinMay1926-TireSize.jpg

Edited by JRA (see edit history)
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I answered this in the General section, but just found it here. I had a 27 Big Six President and it took 700 x 20 tires. I think the 600's will be too small for your car. Try a set of Lesters, softest ride of any bias tire...

 

Frank

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I have just checked my car, it is a 120” wheelbase model as I expected, once it is a sports roadster body. The production date stamped in the engine block is May 18th 1926, so after the Bulletin informing the tire size change. Rim width is 5”. 

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