1920's Tire Size Confusion

[MikeC5]

I'm looking to buy a spare tire for my '25 Dodge Brothers which is equipped with 20" diameter disk wheels (a popular option back in the day). The tires on it are size 6.00 - 20 and the outer diameter measures about 32". The tires are Firestone Deluxe Champions. I cannot seem to find this tire size listed on the Coker, Lucas or Universal web sites. This is the closest I can find http://www.lucasclassictires.com/525-550-20-Lester-BW-75400L.htm but what does the 525/550 mean? Is that 5 & 1/4 to 5 & 1/2 ? I would have preferred to have a matching tire but no luck in that size. You guys with similar era cars using a 20" wheel, what tire size are you using?

[dictator27]

The short answer is yes, that is what the 525/550 means. This is nothing new. I have owned my 27 Dictator since 1966. I still have the tires that were on it when I bought it. I know for a fact that they have been with the car since about 1940. The tire size shown on them is 525/550 21 (in my case)so tires have been sized that way for a long time. (The reason I have kept the tires is because of the brand name on them - Gutta Percha.)

Terry

[Rusty_OToole]

Gutta Percha was an old name for rubber. I remember the Gutta Percha plant in Oshawa, mainly because of the name. It was on Simcoe Street if I recall correctly. The name was on a sign on top of the building in big letters, probably gold when they were new but badly tarnished by the sixties. The letters were fastened to a kind of wire mesh backing. I suppose from a distance they would appear to be floating in the air, when they were new and shiny. I recall a large 2 story brick factory building with the sign on top, it was there up to the early seventies at least, but was torn down and a mini mall built in its place.

Apparently they were quite a big concern at one time. A quick web search reveals that they were a Canadian company founded in 1883 with 14 branches in Canada plus one in London England and agencies around the world, particularly in Commonwealth countries.

Edited May 2, 2015 by Rusty_OToole (see edit history)

[Carsnz123]

I don't know what button you didn't push, but here is Lucas' list of 6.00 20" tires.

http://www.lucasclassictires.com/600-20_c161.htm

This is a dealer here in New Zealand and he lists the Firestone Deluxe Champions that you have already (the prices are in NZD)

http://classic-tyres.co.nz/wp/?page_id=145

As far as I'm aware tire makers don"t stick to strict sizing dimensions so one makers 6.00-20 might be bigger than another's. this is the case with a couple of 5.50-20 I have at home. One is a Firestone the other a Pirelli. The Firestone is a noticeably larger tire.

[MikeC5]

Thanks guys. I don't know why I was having a hard time finding it. The only thing I can think of is the 600 is missing the decimal point (it says 6.00 on my current tires) so I missed it in the search. I went to the Rhinebeck, NY car show/flea market this weekend and the Universal tire guy had the BF Goodrich in stock. I got the car registered on Saturday too (with YOM plates). It was all very straightforward at the Norwich, CT, DMV.

[Sigmund]

Does anyone know how many miles could be expected from the 1920s tires? I know they didn't last very long.

[Layden B]

It is my understanding that so many Dodges and other cars with 20" rims used 6.00 tires because they were so cheap. A high quality 6.00 6 ply tire could be purchased for less than a 5.50 4 ply because so many trucks used that size. The high volume made for low price and they lasted much longer due to thicker tread.

On the Dodge, since the 20" disc wheels bolted right on to the same hubs as the earlier 21" wheels, many cars got a wheel change for the same reason. 20" truck tires were cheaper and lasted longer than the 21". Years ago one old wrecking yard veteran told me that any Dodge with 20" wheels coming into the yard quickly lost its wheels.

[Bud Tierney]

Even assuming the 192os tire technology was more primitive, so were most of the roads...you're naturally going to get more miles if you're on relatively smooth pavement than if you're regularly on gravel, etc...

And tire technology is almost always a compromise between traction and mileage, altho the last NHTSA? report I saw, several tears ago, did list some high end tires with excellent traction AND mileage... so a particular m'f'r's model X might be high on traction, but their model Y better on mileage...

Then (sigh) there're drivers like my brother, who generally had either the gas pedal or the brake pedal jammed to the floor, but little in between...he did consume a lot of tires...