I need a bit of help finding the correct part numbers for replacement tires on my 44' M20.

Both the front and rear rims are a hair over 20''.
The height of the front rim (edge to edge) is 2 5/8'' the inside dimension is about 1 7/8''
The height of the rear rim (edge to edge) is 3''. The inside height dimension is a little less than 1 1/4''.

It seems like most M20s have 19'' rims. Anyone know why mine would measure at 20"?

Are you measuring the rim at where the bead of the tyre sits, or at its outer edge?
The correct tyre size for a 44M20 should be 3.25x19" on the front and 3.50x19" on the rear, but it seems that most people prefer to fit the 3.5x19" on both rims as it tends to look chunkier and it fills the mudguard a little bit better

email (option): davmax@ntlworld.com

Hi Dave,

Here are a few pics to illustrate. I've measured both the outside of the rim and the inside (which you can see in the pics too).

On the first picture where was the other end of the tape? Was it on the edge of the rim, or was it held at approximately where the bead of the tyre would sit?

email (option): davmax@ntlworld.com

It was at the edge of the other side of the rim. The other zoomed out photo shows it.

They are 19" rims, they are measured from the bottom of the well where the tyre sits, not the outside edge.

email (option): davmax@ntlworld.com

According to the contract details, as part of the efforts to standardise (and probably save rubber) machines from WM20 96818 onwards were to be fitted with 3.25x19 front and rear. This should have been roughly from December 1943 onwards

Gotcha. I understand the diameter now.

I think I'm still a bit confused on the width of the rims. One seems to be about 2.75" and the other is 3". Are those numbers correct? Dave listed above that: 3.25x19" on the front and 3.50x19 on the rear.

If those are correct, can someone help me find the correct Dunlop K70s I need to order? I just don't want to order the wrong ones.

For reference:

Here's the rear rim


Here's the front rim

The critical dimension is between the flanges (where the tyre bead sits). A WM2 should be 1.85" and a WM3 is 2.15".

Either of these would take a 3.25 or 3.50x19 K70 within the acceptable range.

https://www.hagon-shocks.co.uk/common/pdf/wheels2011.pdf

Thanks for all the help, gents.

On an M20 I'd definitely fit 350x19 at both ends...With its wide front and rear mudguards the 325s look a bit too 'skinny' I think...

I use Dunlop K70s and find them a good tyre in all conditions but there are others to choose from...Ian

email (option): ian@wright52.plus.com

Hey Brian,

Hope all is well. I've got an Avon Speedmaster II (and I know a lot of the forum will boo and hiss and call it a 'slipmaster') on the front, and a Dunlop copy on the back. It works fine. You won't be going that fast to make much of a difference.

Anytime you want to take me up on that offer of the ride on my M20, let me know.

Kevin