I have a 1972 Super Rat and in need of a new rear tire, 3.50 x 18. All i can fine is 100 x 100 x 18 and they seem to be to big.
I am all most done with my restore and would like to get a good tire for racing vintage motocross for the Rat.
[quote=" All i can fine is 100 x 100 x 18 and they seem to be to big][/quote]
They are. Lots of places cite the 100/100-18 as a replacement for a 3.50-18 only because that's as close as they can get these days. I have a 100/100-18 mounted on a WM-2 rim, standard size for my 1971 100B and your Rat, and mounted, the tire is 4 3/4 inches wide at the extremes. Others may be around 4 1/2 depending on knob design. I had to move the rear wheel back three inches to squeeze in a 100/100. 3.50's are getting hard to find, but unless you want to do lots of mods, that's what you will need.
Check out the Duro HF335 4.10x18 which is about the same width as a 3.50 cheng shin.
I measured the Duro with a set of calipers. I came up with 3.940" on the widest part.
I use it on my 98 and 99 framed bikes. I got the advice from a Penton owner who uses it on his Berkshire.
Mark in Illinois
#492
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Vee Rubber makes the correct size for both front and back. I would hold out for them. Call Don at All-Moto Tire and see when he expects to have them in stock again.
Dale