Help with sizing rear shocks

[kayakersteve]

I have added TB 2 1/2 inch rear leafs, new shock mounts and done some other tweaking to '74 bronc and was wondering how to know what size rear shocks to get now. The length is 20 1/2 inches from center hole to center post. Any thoughts or ideas?

 

[Broncobowsher]

Fully compress the suspension, take a measurement
Full droop the suspension, take a measurement.
Try and find a shock that will fit that won't bottom out or top out.

I got all crossed up on a dirt pile with no shocks and took measurements. Went slightly shorter in the rear as at full droop the CV bound. Not ideal but used the shocks as limiting in the rear. Some people really frown on it, but nearly every factory truck on the road does it that way.

 

[bad 68]

Limiting drop is ok but the shock must not bottom before the bumpstop contacts the frame/axel. Measure the distance between shock mounts then measure the distance between the axel tube and bumpstop. Subtract the second measurement from the first. this would be the compressed length of the shock(for the rear). In front of coarse the bumpstop is on the axel tube.

 

[Broncobowsher]

Limiting drop is ok but the shock must not bottom before the bumpstop contacts the frame/axel. Measure the distance between shock mounts then measure the distance between the axel tube and bumpstop. Subtract the second measurement from the first. this would be the compressed length of the shock(for the rear). In front of coarse the bumpstop is on the axel tube.

Trouble with that is the rear shock is at an angle. For an inch of compression of the spring there is less then an inch of compression of the shock. Not a fixed ratio either as the angle changes as the spring compresses.

Also remember that the bumpstops are not a solid stop. Figure that they will squish around 50%.

When I did mine as mentioned above I was about an inch off the bumpstop when I took the measurement. So I figured I had about 1½" to go. I then measured the shock mounts. I used the angle error factor as a safety factor and subtracted 1½" from that measurement (instead of the 1¼" or so that it really would have come to). That gave me the compressed length with a smidge of safety built in. Started shopping from there.

 

[ctowery]

Like everyone has said flex and measure..use bumpstops to limit travel and straps if needed for droop protection. Example..my EB I used Protofab rear hoops and #9100 17" travel..use almost all of it but it is a costly shock..

We are a Bilstein dealer PM me if I can help.

Cary