I recently bought a late 90's Lightning Stealth recumbent bike, and I think the tires are original. The front tire is a Pr1mo 16" x 1-3/8", and the rear is a Specialized Fatboy 26" x 1.25". Both tires have round surfaces. The Specialized Fatboy is a slick, while the Pr1mo has a very slight tread.
The tires are looking a bit aged. I found a small cut in the surface of the Fatboy. I can probably get by with them for a little while, but I will probably need to replace them. Are fat tires the norm for recumbents? How about skinnier tires for less rolling resistance? How about kevlar belted tires?
Any recommendations as to what to look for in new tires?
Small cuts in the tread are normal byproducts of riding. It the carcass under the
tread is not cut, you can just ignore it, or fill the cut with Goop if worried. Carcass
cuts under 4-5mm can be patched from the inside of the tire with a tube patch
or a piece of tyvek type plastic contact cemented to the inside of the tire. If the
cut bulges replace the tire. There are very few choices of 16" tires, the one on
the bike is a good one. 1.25" tires are not really all that fat and rolling resistance
has not been shown to be closely related, if at all to tire diameter. Tire and tread
construction and materials, not diameter are determining factors. Kevlar belts are
always a good idea, if available. www.gaerlan.com and Google for Poweron cycling
are two sites that have a variety of bent tires. www.hostelshoppe.com is another.
Tires in the 28-32mm range are more commonly used in bents, but there are a few in
the 25mm range from Continental and Schwalbe in the sub 24" diameter size range.
Primo's tires are always a good choice, seem to be well made, not over priced.
The Stelvios from Schwalbe are felt to be sexy for a tire, but longevity has been a problem
for some users, including myself.
In the 16" size, your choices seem to be Comets or Stelvios. More about Stelvios below. Comets are good tires. They are reasonable fast, reasonable light, reasonably long-wearing tires, and they are inexpensive compared to their competition.
For the 26" size, you have more options. I don't know if Fat Boys are still made, but I used them in the past and liked them. Primo makes a Racer in 1" and a 1.25" width. Conti GP and Stelvio come in 25mm. Finding a 25mm (1") is a challenge, but OTOH 26x1.25 or wider is relatively easy.
I don't recommend Continental GPs or Schwalbe Stelvios unless you're going to race with them. The GPs suffer from the famous Continental fragile sidewalls, where running over any junk, such as rubble in corners, will pop cords in the sidewalls. It's not immediately catastrophic but pretty soon your tires look like the cat has been using them to sharpen its claws and you don't dare take them on your next long ride. I've also had problems with them not being round. I expect better from tires when they're that expensive. As for Stelvios, I've never yet worn one out - so far 6 out of 6 that I've tried have suffered carcass failure of some sort first - something that I've never had happen with any other brand. So I'm sticking with 'Any Other Brand' in the future.
I don't have a recommendation for your front tire. but I like that way a Specialized Armadillo 26X1.5 rolls on the back of my Stratus. I've tried the Continental Gran Prix on the back and front, and it doesn't seem to make a difference in the speed of my bike.