Truck Tyres 34 x 7 as 12 ply Olympics

[Lionelgee]

Originally Posted by Tony Smith

Be careful of the ply rating of the 8.25s. Most 7.50-20 were 8 or 10 ply tyres, while the 8.25s are usually 10, 12, or 14 ply. A rough ride will be the result, shaking you to bits.

Are you running duals on the rear axle? Unless your rims have the correct offset for 8.25s, when loaded the tyres will foul each other.

And check clearance around the front end, turning circle can be reduced if the tyres foul the springs or chassis.

I've no experience specifically with Chevs, but early Ford trucks were 6.00-20 and fitting 7.00 or 7.50 tyres led to all sorts of problems with gearing, braking, steering geometry and turning circle. But they were cheaper, carried a heavier load and more readily available than 6.00-20's. Sound familiar?

Hello Tony,

Yes, both trucks run dual rear axles. The Chev had its front mudguards lifted in service. So hopefully this will solve the clearance issues.

Some further searching found that there are some Isuzu trucks that run the 8.25/R20 as standard. As the quality of my rims can only be stated as "dubious" I may be exploring the path of having a set of Isuzu rims getting their centres modified to fit the Chev bolt pattern. Not sure if this is an engineering option that would comply to the Department of Transport and Main Roads here in Queensland?

As far as the rim & tyre count goes I started off in the minus. Both trucks did not come with a full set of rims. Each truck only had singles on the dual rear axle and there were no spares for either truck. Plus I have some ring-ins. There are two almost solid steel faced rims. There are only the stud holes and then two squares cut out of the rim face. One is for access to the valve stem. The other square is directly opposite the valve. Perhaps these were dedicated internal dual rims for the REO Speed Wagon? They sure look like they should not normally be seen.

The interesting thing is that the 1940 Chevrolet rims are interchangeable with the REO stud pattern!

Kind regards
Lionel