with your deck pulled up full, would expect an 8' ramp length will give you clearance to put tractor in shed.

I would think for sheer comfort, you'd build an earth ramp.

My original question was; how long can a 2X6 be, before it would be break with the weight of the tractor and driver, if it were suspended at the ends, as in a ramp.

sorry - missed your question on 2x6 strength..was thinking about deck hump clearance coming off ramp onto garage floor.

your machine is prolly around 550 lbs - I wouldn't risk any more than a 6' unsupported length using yellow pine or such.

Oak hardwood 2 x 10 or 2 x 12 8' long unsupported might make it, but would test well first before risking damage/injury...

I'd say eight feet long. Anything shorter than that will be too steep. I have a pair of aluminum bleacher seats that are 8 foot long, and I can load and unload a Craftsman lawn tractor, on level ground, to haul it in my Ford Ranger pickup. The ramps have bolts that fit into holes in the tail-gate, and they work well. Not too steep. I also use them when loading from a banked place in the yard. You could use this idea so you could remove the ramps for another use. Or, to close the door-s.
You must understand about the "break-over" area, at the edge of the shed floor. You don't want to get hung up when moving in or out. Thats why i recommend long ramps.

For the wood ramps, i'd suggest making a pair of "A" shaped fillers, to set under the middle of the planks, if you think they might not hold! And, make an inlet/step, where the upper end of the planks can slip in, to hold the upper ends. Or maybe line the edges with angle iron strips, for added strength.

I second the mid-length supports. They don't have to be fancy or perfect length, since the boards will have quite a bit of give/flex anyway. While you're at it, use the mid-length supports to tie the two ramps together a X distance apart, so they are perfect width for your tractor.

However, best method is well-packed earthen ramp.

OP Thanks to all of you earthen ramp people, I am sitting here tonight with every muscle in my body sore after moving about a 100 cuft of dirt from one side of the lawn to the other. ;-)

I decided not to go with the extra long ramps that would have to be strengthened to support me and the tractor, and leave the shed looking like a Carolina beach house.

The revised plans calls for building up the earthen ramp until it is about 10 inches from the level of the shed floor, and using existing ramps that are about 4" long to get the tractor into the shed from the earthen ramp.

My dad made these ramps when he had the tractor before he died. These ramps already consider moving over the bump and the mower deck.

I now have to wait until it compacts a little before doing the final shaping of the ramp. Fortunately it is suppose to rain the next couple of days so that will help.

Just say no!

If you are not going to move within the next year, fix it! Turn the shed 90 degrees, do some earth-moving? Cut a lowered path to the shed? Do something that enables you to drive into your shed!

If you can't figure out how to do it, hire an engineer. If he can't figure it out, hire an accountant!

If you can't find one locally, get back to me. For a small fee and transportation costs I will come and give you a solution.

Don't just wait for the earth to settle and compact all by itself.
Speed up the process by using the tractor.
Carefully run up and down the new slope using the weight of the tractor and operator to help squash down the dirt.
Begin in the center and work outward toward either side.
Drive uphill as far as you can, then back down. Move over just the width of a front tire and repeat.
After you have completely "stitched" that half of the earth, go back to the center and begin stitching the other half.
It helps to go over the entire procedure a few times.
Ideally, the compaction work would have been done during the filling in work.............a layer at a time, because the very thick fill at the upper end will be slower to settle and compact than the thin taper at the skinny end.

I just loaded a 760# tractor into a Chevy van using 2x10's with the aluminum ends from Lowes.I made the ramps 6' felt pretty safe. I don't think that 2x6's would be safe. my ramps cost ~$30.00.

I have decided to use a combination of earthen ramp and wooden ramps, I have the core for the ramp in and will haul in additional earth to shape it when it is warmer.

Question: You say you loaded your tractor into your Chevy Van; What kind of van do you have?

I have an 2005 Chevy Astro passenger van. Based on the published specs my JD LT 155 should fit in. If I can put the tractor in the Van it would save a lot of money if and when it needs to go to the shop for repair. Also I could then take it to my daughter's house and help with their lawn.