This past Saturday I did a ride called Bike Around Carroll County Iowa, or B.A.C.C.I., see the post ride report in the General Discussion forum.
Part of this ride was on the Sauk Rail trail. The first and last legs of the ride are on the part of the trail that is paved. Between Carroll, Iowa and Maple River, Iowa.
However the rest of the trail is crushed limestone.
Me and several other riders decided to ride on the part of the trail between Breda, Iowa and Maple River, Iowa because we had gotten tired of riding the hills.
My SWB, OSS Vision R40 did rather well on the crushed limestone part of the trail. Sure there were soft spots I had to power through. The bike did get a little squirrly in certain areas. And where the trail crossed some of the county gravel roads I had to stop, get off and walk because the shoulder portion of the gravel road was to soft and would have pulled me down. But other wise it was not to bad.
I run 26" x 1.25 Primo Racers on my recumbent. A really good road tire for 'bents. But on a crushed limestone trail I would rather have had knobbier tires, especially if I was going to ride for a longer distance. I talked to the guys at my LBS about this and I can get a new set of appropriate tires for riding my Vision on crushed limestone.
In the future, don't know when yet I'm planning on doing a self contained tour on the entire Katy Trail in Missouri all the way across. I know most of it is crushed limestone. For this ride I will get the right set of tires to ride on.
So for recumbent riders everywhere, yes you can ride on a crushed limestone trail with the right tires.