Folding Bikes - School me on Twenty tires.

The tires on my Twenty are the originals and are falling apart.
They are (451) 20x1 3/8 Raleigh Record tires made in Holland.
I went shopping for a pair today but could find nothing but 20 x 1.75 or 20 x 2.0.
After reading Sheldons site I found that decimal sizes do not interchange with fractional sizes.
Does this matter if I change both tires? Will they fit the rims?
Or can I buy new equivalents of what I have now?

There are two sizes on 20" tyres, 406, which is fitted to almost all bikes, BMX or otherwise, and 451, which are fitted to 20's, some Bike Fridays, and pretty much nothing else. There are obviously good quality 451s available in the USA, otherwise BF wouldn't use them. Search for 451, rather than 20". Lots are available in the UK, but I'm not finding Google helping me to search in the states right now!

I'm happy with the Primo Comet 20X1-3/8 tires on my R20. 85psi and good grip. They are available on various web sites.

There are some at Harris Cyclery (eternal home of Sheldon Brown):

http://www.sheldonbrown.com/harris/tires/451.html

451 tyres can be found online in lots of places but try the Bike Friday Site and Gaerlan first as they're specialists for small-wheel bikes and both stock this size (or did last time I looked). As a rule these days, the 451 size is used mainly on higher end 'roadie' style small wheel bikes and recumbents, meaning most 451s are skinny little slicks (Schwalbe Stelvio, Pr1mo Comet). It's harder (but not impossible) to find wider, more utilitarian tyres like the original Twenty's boots - search for widths of 1 3/4" and you should find something akin to your original tyres.

Gaerlan's 451 Page:
http://www.gaerlan.com/bikeparts/parts/451wheel/wheel.html

Bike Friday: 451 product search yields thus results:
http://store.bikefriday.com/advanced_search_result.php?keywords=451&x=0&y=0

Thanks for the tips!

Can anyone advise me on 20" tyres for my Dahon D7. I've misplaced my handbook and the Dahon website isn't showing specifications - or maybe I'm looking in the wrong place. I don't need any at the moment I'm just researching what's available.

Any D7 riders got any tips?

I have these tires on my bike and like them, conti (http://biketiresdirect.com/productdetail.asp?p=COGFM#)

There's a pretty good discussion on tires in the archives here, http://www.bikeforums.net/showthread.php?t=335014&highlight=tires

Thanks, I'll check the discussion in the archives too.