Thread: Tyres

Hello from Brisbane.

It depends on what tyre size was on the vehicle when the speedo was installed in the truck.

That is, several different speedos were fitted depending on whether or not the truck was built to run on 6.00 X 16", 7.00 X 16" or 7.50 X 16" tyres - or bigger for the heavy duty model with even larger tyres.

There is a serial number on the speedo face - often near the odometer or trip meter that identifies which one it is.

There are quite few threads on the site that go into the identification and speed conversion details.

Cheers,

Neil

The comparison would be that at 100km/h indicated for 7.50 x 16 you will actually be doing 102.2km/h with 235/85/16 fitted... Pretty much negligible in relation to Series speedo accuracy and the "error" will reduce the slower you go.

Obviously as Neil said, depending on the speedo, but a Series 3 88" most probably ran 7.50 on those wheels you quoted.

ETyreStore Home - Welcome To The Revolution

Cheers,

Lou

Originally Posted by Loubrey

but a Series 3 88" most probably ran 7.50 on those wheels you quoted.

Cheers,

Lou

Hello again.

This may well be true, but not necessarily so. Most of the later S3 88" trucks were delivered new with 7.50 X 16" tyres and appropriate rims and speedo, but many of the early deliveries had the smaller tyres, narrower rims and relevant speedo. Given time and the ease of inter-swapping of parts the rim number on a given truck just says that what is fitted now rather than a foolproof indication how it was built - or what speedo is in it.

My 1975 S3 88" truck came to me with the larger tyres but also had a speedo suited to the smaller wheel which I have since replaced. I understand that the present rims originally came off a S2A 109" along with its motor, brakes etc.

Cheers,

Neil

Have a look here regarding speedo/tyre size.

The Series Speedo and Tyre Sizes

Ran a GPS/speedo app on my iPhone and the young bloke confirmed that my Isuzu C240 powered Series III was reading low......it actually does over 100Kph !!

Colin