Truck Tyres 34 x 7 as 12 ply Olympics

[Hanno Spoelstra]

Originally Posted by Lionelgee

As per the photographs the numbers 34 x 7 and the ply rating is 12. The tyres were made by Olympic.

Has the unit of measurement changed as I cannot find any reference to a 34 x 7 tyre? If it has changed what would the measurement now be referred to as?

The next obvious question is .... are they still made and who sells them?

Hello Lionel,

34 x 7 is an old designation for the tyre sizes 7.00-20 and 7.50-20 (depending on the source). This size was commonly used on trucks in the 1930-40-50's. See the quote from a Commercial Motors article "Simplification of Giant Tyre Markings" from 1951.

7.00-20 is not a common size, but they are still being made new for the historical vehicle market and can be found.

Military NDCC (bar grip) tyres 7.50-20 may be an option too, these are far more common (at least in Europe) as most US military trucks like the GMC CCKW used that size of tyre.

HTH,
Hanno

Originally printed on the 9th march 1951

Simplification of Giant Tyre Markings

%URING the past few years the tyre industry, recognizing • the need for the simplification of giant-tyre size mark

3s, has taken certain sleps to achieve this end. Further nplification has been announced by the Society of Motor anufacturers and Traders, which says that by January I, 52, the new markings will be completed for tyres for iginal equipment and replacement purposes.

For many years the tyre industry has had high-pressure d low-pressure giant tyres, the former being marked, say, x 6, and the latter 7.00-20. To simplify the range of :h tyres, high-pressure equipment was made in moulds the same dimensions as those used for low-pressure tyres, Ilist the difference in construction, as related to the numrs of plies of fabric,was maintained.

Dual marking in some sizes was temporarily adopted. A it-marked cover is a high-pressure tyre made to low:ssure dimensions. As an example, a 7,50-20/34 x 7 tyre, a 34 x 7 tyre, so far as price, construction, load capacity I inflation pressure are concerned, but it is made to 0-20 dimensions.

ks a further means for identification, "ply rating" is led. The term is used to identify a given tyre with its ximum recommended load when employed in a specific

e of service. It is an index of tyre strength and does not :essarily represent the number of cord plies in the tyre. kt one time it was possible to determine the maximum d and inflation pressure for a tyre by reference to the nber of plies it contained. A modern tyre, however, may itain more ot fewer plies than is indicated by the ply [hg,' but, for a given size of tyre, the higher the ply rating greater the strength. The simplification of markings has now been completed by the elimination of high-pressure or dual marking. Thus, the 34 x 7 (high-pressure) and the 7.50-20/34 x 7 10-ply rating (dual marked) become identified as 7.50-20 10-ply rating. Thus, tyres will have a particular size marking but different ply and load ratings, such as 7.50-20 8-ply rating for a maximum load of 21 cwt. and an inflation pressure of 60 lb. per sq. in., and 7.50-20 10-ply rating for a maximum load of 27i cwt. at 85 lb. per sq. in.

The following table gives examples of the original, interim (dual marking) and simplified markings for tyres fitting 20-in. rims: Where vehicle clearance limits preclude the fitting of tyres having the simplified marking, tyre manufacturers will continue to supply for a limited period the old high-pressure tyres, such as 32 x 6, 36 x 8, and 40 x 8. The marking of tyres for low-loaders remains unchanged.

Source: http://archive.commercialmotor.com/a...-tyre-markings, accessed 30-jan-2019

[Lionelgee]

Hello Hanno,

Thank you very much for your very rapid and extremely thorough reply, Hanno. I greatly appreciate it.

Your response greatly assists in my quest to track down around 14 of them. Enough for two trucks with dual rear tyres and a spare for each of the trucks. Well, that is unless they required different rims for the front axle and the inside dual? One truck rim is almost a solid face with two rectangles cut into them. It is very ugly. It was probably made as a dedicated inside dual wheel as it was not readily seen because it was covered up by the outside dual wheel.

Kind regards
Lionel

[Barry Churcher]

https://www.universaltire.com/700-20...wall-tire.html

Here is an example available in the US. I bought a pair of these for a trailer and they work well. I am sure you could find a supplier closer to home.
Cheers,
Barry

[Lionelgee]

Hello Barry,

Thank you for posting the link. They had approximately 6 different varieties of 700 x 20 tyres. I think I will do without the white wall version.

Would these tyres need tubes and rust-band; aka tube protector sets as well?

Kind regards
Lionel

[Tony Smith]

Originally Posted by Lionelgee

Would these tyres need tubes and rust-band; aka tube protector sets as well?

Kind regards
Lionel

Irrespective of what type of tyre you find, ANY tyre will require tubes and rust bands to fit on your split rims and still hold air. The problem is not the tyre design, it's the rim.

[Lionelgee]

Hello All,

Just to keep this thread updated - I moved my trucks forward about 1.5 metres yesterday. I had a look at the tyres fitted to each of the two trucks. One truck had three different approximate tyre lablels. 34 x 7; a 7.00 x 20 and a 7.50 x 20.

Due to the totally ruined nature of the tyres - very flat and square bottoms; I had to use a combination of 3 ton trolley jack and a mobile crane. The jack under the rear differential and the mobile crane via chains connected to the front leaf spring hangers, gave me ground clearance. Add in some locomotive force provided by a Yanmar diesel four wheel drive tractor. The battery went flat on the tractor so I called in the back-up. My late model Series 2A short-wheel base Land Rover. All the fun of the fair!

I moved the trucks forward so I could install three sets of pallet racking to store goodies on - like engines and gearboxes. Hopefully my lack of suitable, accessible storage has been resolved - finally after a decade!

I have gained a LOT of floor-space now and soon after I sort all the shelves and pallet racking out - I can find something when I go looking for it! Yes hope springs eternal.

Kind regards
Lionel

[Matthew P]

So is 7x34 referring to the rim width by overall diameter of the tire? I've not measured my 7.5-20 tires for my Ben Hur but to my eye they've looked about a yard across, or around about that 34 number.

Matt