Hello Abcgirl,
apologies for the late reply and welcome onboard.
There is no straight answer to your question because in origin Skootamota's were fitted with 16x2 3/8" beaded edge tyres which are no longer in production. I've been searching everywhere for them but it seems like the last pair was sold more than 10 years ago.
The only option I did find was to get them made in Malaysia but you would have to buy an entire container and I did not consider it a viable option due to the low number of vehicles using these tyres.
I was lucky enough to find on ebay a pair of NOS Dunlop Carrier tyres 14 x 2 x 1 3/4 but that took a couple of years. This size fits on the original beaded edge rims and seem to have a good grip.
For the past 40+ years, several people have been trying to find ways to increase the contact surface between the original beaded edge rims and these wired tyres because of concerns these might slip when used on the road. There were experiments adding rope in the gap left empty by the missing bead but I have never been able to find a clear answer on how to best do this.
In my case, the tyre seems to fit just fine without any addition although I must admit I have not used it extensively or at high speeds ( :woohoo: )
Most people tend to change rims because they cannot find tyres. In this case you can just have some fun trying to understand tyre sizes and maybe pick something like 16x2.125 Raleigh scooter tyres/rims or, 2 1/4 - 12 wired tyres/rims.
I'm sure there are other sizes which come close to the original and you will have just to decide if you want a bicycle or scooter tyre.
My notes are all summarised here:
https://www.abcroadmotors.co.uk/forum/abc-discussion/11-latest-find.html?start=18
What rims do you have? Can you send us a picture?
Good luck but let us know what you chose.
