The way you describe the ramps "to get in my shop" Im guessing you need a short "bridge" to get over a slab of concrete and in the door rather than a set of ramps to change oil and the like.

IF that is the case, I doubt youll be happy using pipe for the ramp. Rolling your steer tires up will not be an issue but the drive tires will not work well climbing up something round. Look at car trailer ramps, nobody uses round. If that pipe gets the slightest bit damp all you will do is spin. Make it an angle instead, or even expanded metal. Give the tires something to grab a hold of.