I have a FWD Sofrider V1, which I am enjoying very much. On rougher roads, though, I seem to lose the "confident feel" of the bike, even more so when descending 25-35 mph. I feel no confidence in taking much of a curve at those speeds. I already have 500 miles experience on the bike, so I am not sure how much more mileage will change those sensations.

In an effort to change the confident feel of the bike, I plan to replace the original single wall wheels with new, lighter, stronger wheels soon, and will probably get a "stickier" slick tire than the Kenda Kwests, to see if that changes my perceptions.

But, what about this idea:

Though I will not go back to DF biking, I've been reading about the rise of the 650B tire size as a comfortable and confident-handling tire that doesn't compromise on speed. With the rising popularity of that size, and with lots of Europeans having used them for decades, there are several brands that offer even 30mm+ widths with excellent handling, traction, and low-rolling-resistance speed.

Would a change to 650B make any difference on a recumbent? What would those differences (benefits & drawbacks) be? Any thoughts or experiences?

What size tires does the Sofrider use, and what width are you currently limited to? You don't have to go to a weird size to get a wider tire. 650B may be used more in Europe than in the U.S., but that's not hard to say since it's almost non-existent here.

650B is a medium width rim size that can accept wider tires. On a DF, the ride can be described as opulent. I have no idea how that would feel on a recumbent. The best advice is to experiment and see if you care for it.

To answer BlazingPedals question:

The Sofrider comes with 26 inch wheels. So this would be an increase in diameter.

Because of the popularity of 650B tires with brevet and randonneur riders, there is a good selection of high performance tires for that size. Also, I am wondering if the slightly larger tire size might change the handling "problem" in a good way.

That's why I am considering them, and why I wonder what other people's experiences are.

I would be interested in this as well. Have the plans for a homebuilt LWB bent and the donor frame I am using for the front end is tight with fat 26" tires (originally a 27" wheeled 10 speed). I'm going to get a cheap skinny 26" tire and see if it works better but the 650b may be a better choice.

I have a cheap DH snow bike with 700C that takes a 2.0 tire. If you have the room for a wider tire, I don't see why you can't get it in a 700C or a 26 - you just may need to look around. Like I had to to find the skinniest 26" and 20" tires I could get with a high psi capability.

My high racer came with 23mm 650C Kwests. I've since switched to Conti GP4000s for better puncture resistance and tire life, at the expense of weight. However, any road tire on road should give you sufficient grip, unless you're over-inflating. Definitely go with dual-wall rims though, they're MUCH stronger.

Absolutely. However, make sure the rim + tire will clear your fork and the body. I built up a set of 26" (a few mm smaller in diameter than 650C) just so I could put wider than 23mm tires on it safely. I'm running a 28mm tire (Conti Gatorskin) in front and rear now, and even with that slight size difference the ride is night & day different. I could probably even fit a 32mm in the rear, where it matters most. I'm still happy with the 23mm tries on the 650C rims for asphalt and paved trails, but for gravel, crushed limestone, or chipseal, wider is not only much more comfortable, especially on a recumbent, but probably more efficient from a rolling standpoint.

Edit: Aside from making sure the tire diameter will fit, also make sure the rim will fit between your brake pads if rim-braked. Luckily moving the pads up and down is all I need, as they clear the walls on both the 17c (which are the 26") rims and the 15c (which are the 650C).

My 650 B wheeled bikes tend to woble at higher speeds. The 655B tires are heavy and more easily prone to being out of balance than 700's.

What 650B tires are you using? If I ever build up the one 650B Velocity Aerohead OC rim I have, I want to avoid mounting those tire models.

As to the original poster's question, I really think you should get those better 26" rims which are hopefully wide enough to mount some wider 559/26" tires. This size is so much more popular that you have numerous choices of wider tires (staying within the ETRTO size limits for your rim's inner width). How wide a 26" tire will fit and how large a diameter (larger tire on given rim = larger diameter wheel)? Could you go all the way up to a 2" (50 mm) Schwalbe Big Apple or perhaps something a bit smaller? Bit smaller include Schwalbe Kojaks, Continental Sport Contacts (1.3" or 1.6"), etc.

If you ride at night, both the Sport Contacts and the Big Apples are available with reflective sidewalls that make you instantly recognizable as a BICYCLE at quite some distance in a motor vehicle's headlights.

You also might check you are using reasonable tire pressure front and rear for your all-up weight and tire size. For some guidelines on tire inflation pressure for given loads on tires, see HERE, HERE and HERE.