Military Lightweight Forum

Then you are in luck,, as one marked 940 is a KMH speedometer for 7.50" tyres IIRC. (And my maths is right.). The other numbers I mentioned are for MPH speedometers.

940 refers to the number of turns of the wheel per kilometre. Roughly equivalent to 1408 turns of the same wheel per mile.

Regards,

Thanks for all the great feedback.
How confusing did the tyre manufacturers have to make it? I thought the 75R16 would be 7.50 and the 85R16 would be very different, like 8.50
Okay, so when I get tyres I'll probably go with a locally available:

Westlake SL369 245/75R16 AT terrain
I'll mainly be on roads and tracks - not deep mud or rock climbing!

https://www.amazon.com/Westlake-SL369-O ... B00VLYTU96

AR4412 wrote: ↑

Thu Jun 15, 2023 8:09 am

The 235/85 R16 is about the closest to a 7.50" tyre in overall size comparision, but they do vary slightly between manufacturers.

Hi Alex.

The modern tyre sizing is weird because it's a mixture of imperial and meric. In your example of 235/75R16, 235 is the width of the tyre in mm; 75 is the profile (aspect ratio) as a % of the width i.e. The depth of the tyre is 75% of 225mm; and the 16 is the wheel diameter in inches.

Thus the smaller the aspect ratio the lower it sits and the smaller the circumference for a given width e.g. A sports car might have 40 profile tyres which look more like rubber bands round the rim.

There are also other bits on the tyre code which are beyond me but indicate things like max speed and weight ratings.

The older designations like 750x16 come from the crossply days AFAIK when a tyre was just a tyre and didn't come in varying aspect ratios - someone will correct me I'm sure but I think they were more of less standard at around 85%.......

Hope that helps.

Steve

Steve, that helps a lot. Thanks.
The aspect ratio bit was the confusing part but now I've got it.
I'll take a look at 235 and 245 to see what works and is available here. The 85 might be a good plan if you say the original 75R16 ply were about 85% aspect ratio.

I'm after something that looks in keeping with the original size but with a touch more aspect ratio and width.

AR4412 wrote: ↑

Thu Jun 15, 2023 8:37 pm

Then you are in luck,, as one marked 940 is a KMH speedometer for 7.50" tyres IIRC.

940 refers to the number of turns of the wheel per kilometre.

Regards,

Any idea what 920 would mean Neil?

I have a 1983 lwt currently with 205/80 R16 fitted. I want to replace these with 6.50's or 7.50's.

Thanks
Jamie

Hi Jamie,

A 920 KMH speedo would if I got my math right, be equivalent to a 1472 MPH speedo, which wasn't I believe a Land Rover option. (If I'm wrong, I'm happy to be corrected.)

Can you see the Serial Number on the Speedo face? Might be able to track it's original fitment from that. The tyre size would be equivalent to around a 7.0"x16.

Regards,

Hi Neil, thanks. I'll have a look tomorrow and get back to you.

Regards
Jamie

Hi Neil

Here is the front on my speedo if you can make sense of that.
Thanks
Jamie

Hi Jamie,

I tried finding that Speedo last night, but even the Smiths/Jaeger lists I found don't list an SNT 6209-45 speedometer. I did find some other applications that had a KMH '920' Speedo, but no Land Rover speedo's on the lists.

I looked into the optional parts catalogue as I was sure I had previously seen a 7.00x16 tyre in there, and I had.
So I looked a speedo options to see what was there.
We just need to find images of, or info on, the KMH ones to see if one matches yours.

Regards,

Thanks Neil, I appreciate you looking. It is possible the speedo has been changed out by a previous owner but from what I can see of its history the mileage looks genuine.

These things are never straight forward. I posted a question on the Facebook lightweight group asking what the original tyre size would be for a 1983 lwt and I thing the general opinion was 7.50's... but who knows for sure. I actually prefer the larger tyre. I'm currently looking at some Deestone 7.50 x16's.

Again, thanks for your help, any info will be appreciated.

Thanks
Jamie