36x8 tyres

[John Sgwar]

I have 36x8 tyres on the rear axles of my Leyland Hippo. Can anybody tell me the modern equivalent tyre size please? Thanks 

[john1950]

It is a long time since I have seen any 36x8 tyres, I would think the closest today would be 11R.22-5.

[Adrian Barrell]

36 x 8 is a 20" rim so either 7.50-20 or 8.25-20.

I take it they are twins on the back?

[John Sgwar]

Thanks John 1950 & Adrian.   Yes Adrian twins on the back. The fronts are 11.00-22

[john1950]

As this Forum is aware getting imperial sized marked tyres is getting increasingly difficult. Older sized tube type tyres are either low volume production making them expensive or no new production, relying on old stock for supplies. As time goes by compromise is going to have to be the name of the game as age related use comes into effect. Metric marked tyres are going to be all that will be available, or possibly some imports from countries still using the old format.

[7VHU]

Old size = nominal outside diameter x section height.

eg 32 x 6” is 6.00 by 20” in newer money. Subtract 2 x 6 to give rim size.

30 x 3 1/2” would be 3.5 x 23” (Ford model T)

36 x 8” would be 8.00 x 20” ( probably 7.5 x 20 would be easier)

Worth checking width of rims inside the flanges as that will affect choice too.

Offsett of rims may limit size as tyres should not touch when running and watch for clearance behind inside wheel too.

Looked after ( cool, dark and unloaded) and they’ll last quite a while.

[John Sgwar]

John 1950 & 7VHU Thank you both. The info is invaluable. I will have a look this weekend when I get home from work. Thanks again 

[Adrian Barrell]

7.50-20 and 8.25-20 are still readily available new as a truck tyre but they aren't cheap, especially if you need eight of them! If you wanted a military tread, GMC tyres (7.50-20) might suit and are a bit cheaper.

[john1950]

Of coarse the other things to look at when changing tyre sizes is the load and speed rating. I presume we are talking about a Leyland Hippo 11a. For the time these were considered a heavy truck rated at 10 tons. I am sure that I can remember my father changing 36x8 tyres for 9.00x20 and even 10.00x20. I think the original front tyres 10.50 x22 were difficult to get back in the day. 

[mammoth]

The calculations are correct so far as rim diameter goes however the vintage sizes had a 100% profile (they are as high as they are wide) whereas modern sizes are about 90% and thus require a wider rim and tyre to achieve the same outer diameter. This is why they look wrong on a vintage truck. As said 9,00 20 would be the closest to get you on the road and have the required load rating. The 10,50 x 22 are an American size and were likely specced due to war time availability. They will still be available from USA. but a change of rim to 20" would allow fitting 10.00-20 tyres. Check that the stud pcd is European and not American Budd.

Pre war lighter trucks often used 36 x 6.00  which at a glance looks similar but actually works out as a 24" rim and a modern nearest conversion would require a change of rim to 20" with 7.00 - 20 tyre

[John Sgwar]

Thank you all for the info. 

[7VHU]

and during the war the smaller trucks and trailer pumps used 32 x 6 (6.00 x 20”) presumably to save on rubber.

Good point on load rating and speed (downhill)

[Adrian Barrell]

Unless you are getting the truck plated and tested, you can't carry a load in it so it will not be running at design gross weight. That gives you some leeway in tyre rating.

[John Sgwar]

I have been toying with the idea of putting modern rims & tyres on the front & back.

[John Sgwar]

I have been toying with the idea of putting modern rims & tyres on the front & back.

[john1950]

As with any changes going for better than original usually gets a thumbs up from the insurance company. As they have the casting vote.

[mammoth]

A win win would be to convert to the later version of the mkll Hippo and that is to fit 13.50-20 or 14.00-20. Remains authentic and gives it that hunky look plus a few mph faster because of the larger diameter tyres

[radiomike7]

4 hours ago, John Sgwar said:

I have been toying with the idea of putting modern rims & tyres on the front & back.

Modern rims are hub centric while yours will be centered by conical or spherical wheel nuts.

As Mammoth has mentioned, you may find that Scammell Explorer or AEC militant wheels might work with 14.00x20 tyres, they have a 3" and a 7" split rim to give a 10" wide wheel which can be fitted either way round to give a 2" offset on the rear and 2" inset on the front.