Ger
I found the BWC rails to be plenty smooth enough, and a big improvement over the Shopbot
PR's old wheels on the edge of the unistrut method. Particulary on the Y axis, where I have wheels/rails on opposing sides, this method should be very adequate. Shopbot's newer models use BWC rails and wheels, FWIW.
But the wheels as I have them configured on my X axis do allow some racking. Normally when the motors are under power the hold function of the steppers is more than enough to hold the gantry from racking. But if there is a problem, a loss of steps or the like, the gantry is easily racked, and the BWC rails/wheels don't do much to prevent that.
I think that 25mm guides from say HiWin would prevent most of that ability of the gantry to rack. My thinking is that if the gantry can't move out of square with motors OFF, its less likely to move out of square when something causes this with the motors on.
I'm not gonna upgrade until I find that this is really a problem. I can re-square the gantry easily enough with my stops. Also, I'm saving my lunch money for a spindle, so new rails are well off.
I'll try to find the original pics- hopefully they are still on my hard drive. If so I'll post larger ones or post a link to them. Thanks for your interest.
Wayne