YATQ (Yet another tyre question): What's my sidewall height?

Here's a quick one. I have these tyres on my 1987 110 with standard steel wheels:

Tyres Avon Rangemaster tyre size 7.50 R16 C - www.iTyre.com

They're marked as 108/106N 7.5R16. So, width is 7.5 inches and inner diameter is 16 inches, but what's the sidewall height?

Any idea what that "108/106N" bit means?

I'm looking for a new set of wheels & tyres and ideally the speedo will still be accurate when it's all said and done.

Cheers!

Imperial tyres usually had a aspect ratio of 100% so a 7.50 is 7.5 inches wide and 7.5 inches tall. Meaning the tyre should have a rolling diameter (With a 16" wheel) of 31".

I say should because it don't always work like that with remoulds!

Thanks! That seems right since they look *really* tall