Sun Seeker EZ-Sport AX Widest Tires
 

https://cimg8.ibsrv.net/gimg/bikefor...05753ffb28.jpg
The stock tires are:

Front 20×1.50

Rear 26×1.50

I'd like to get a softer/smoother ride, is there anyway you can put slightly wider tires on the rims? All of my bikes I've owned there was never a problem but I thought I read a while back that this particular bike model does not allow mounting of wider tires?

Is there much clearance between current tires and stays at the rear and fork up front?
What pressures do you run?

I run the tires at 100 PSI (that's what the tires say). Would you happen to have a photo of the stays at the rear and front? I don't think I know what you mean when you say that.

The chain stays and seat stays are the frame members that the rear wheel/tire runs between. The fork is the piece the the front wheel is attached to and pivots when you turn the bars. Is there much room between the front tire and the fork and/or between the rear tire and the frame? Next larger size tire you might be able to try would be 1.75". Depending on how much clearance there is between current tires and the frame/fork.
Higher pressures result in harsher rides. Guessing that your current tires say Maximum 100 psi. Not required to run Max unless your size/weight require it. I run a 1.25" rear tire at about 75 psi. It says Max 100 psi. I run my front tire (1.25) at about 65 psi.
Tire pressure calculator's don't all give same results but are usually in the same ballpark. Here's a calculator that seems ok: https://cycleschinook.com/tire-pressure-calculator/

The Kenda Kwest comes in more than one 20" IS0 406 version. I had a set that came with my first trike rated 100 psi on the sidewall. The first set of replacement Kenda Kwests were labeled 60 psi. The Kenda website shows the following about the 406 high pressure version, "The Kwest High Pressure Road Recumbent tire is constructed of a steel bead and rates at a max of 100 PSI". You can lower the pressure for more comfort but is limited by the increased possibility of getting pinch flats or degrading the sidewall on the tire if you lower it too much. Utah Trikes has a 20" Kenda Kwest with a 60 psi maximum (on sale now for $10). You will lose some speed with a lower pressure but gain comfort.

You don't need wider tires yet. Experiment wih lower tire pressures to soften up that ride. 100 PSI is way too high comfort. If you do end up getting new tires, think about going to folding bead tires. With these, and a lower pressure than the max called for, you can get a much smoother ride.The thinner sidewalls will soak up a lot of road vibration. BK

I have Kenda 100 psi tires on my recumbent. When they've worn I will replace with Big Apples. They're fine tires but more air = more comfort.

I don't know what the max size tire is that your bike will take, but you can get an idea by looking at where the tire comes closes to the frame. Not only at the sidewalls, but also the 'top' of the tire, at the brake bridge or crown of the fork. Kendas are cheap for OEM purposes, but if you're thinking about changing tires, consider changing brands too, to something that might ride softer. Also, you don't need to run at the max rated pressure, you only need enough pressure to avoid getting pinch flats.

My EZ Sport AX is quite comfortable with these tire/pressure combinations.

Rear; 26" x 1.35" Panaracer Ribmo foldilng tire. The pressure range is 60-95PSI. I run it at 75 PSI

Front; 20" x 1.25" Schwalbe Kojak folding tire. Pressure range; 55-95 PSI. I run it with 64 PSI.

My biggest problem with comfort on this bike was vibraton from the front wheel and coming up through the bars. On asphalt pavement where the smoth top layer had worn off, the vibration really aggravated the nerves in my hands. Folding tires with lower pressures fixed that. Putting two foam hand grips on each side helped too. Lower tire pressures does mean slower speeds. However, there is a happy medium in there if you experiment with what you already have. BK

Where I live Kenda Kwests flat on every ride. Every ride. Once I had 3 flats in the same day. Needed both spare tubes and a self-stick patch to get home. Got Schwalbe Marathons in a hurry. They flat every couple of months or so. Bontrager Hardcase H2 tires don't flat at all! I don't take tubes or patches when riding the two bikes with the Bonties. They are that good. So, of course they don't make them in 20" size ... I also haven't seen them in 26" or 700C since the Supply Chain went tits up. Good thing they also seem to last forever ...

Edit: to stay on topic, the number one cause of pinch flats is riding off curbs (kerbs). The distant second cause is hitting a pothole or road debris at speed. The first should never happen, the second can be avoided by mature riding (joking). I could not find a stated maximum size for that bike. I tried. Looking at the bike though I'm hard put to see where you could get much bigger than at present. It's probably not worth the headache. I have the same size tires on my bent and I run them at 80psi. If you want greater comfort, reducing tire pressure isn't the best way because of the poor effect it will have on your speed and endurance. Pad the points of hard contact between you and the bike.

Experimenting with tire pressures is free and an EZ Sport AX is unlikely to ever be a really fast bike. It's heavy and has a 26" rear wheel, not the stuff of speed bikes. OTOH, it is relatively comfortable if you keep that in mind as you make changes. It also has a good sweaty workout built right into it. Enjoy. BK

LOL Heavy, sure! But my Baron has a 26" rear wheel, and it's not exactly slow. Of course, having half the frontal area of the EZ-Sport might make a difference, too...

Well, I will partially retract my comment about the AX not being a fast bike. They are real movers when you have a good tailwind. BK

My highracer seen here has 26" x 1.5" clinchers OEM. Just got some 1.0" Tom Slick clinchers from Modern Bike. Look out world ...

LOL, you're not wrong. The AX is not fast. I'm sure the tire size has something to do with it; but more it's the seating position and the fact that everything about it is very heavy. A friend rode one for a year, then got a TourEasy. He remarked how it surprised him how much faster the TE was.