WARNING...you do NOT adjust height on the Ohlins or JIC by cranking the spring perches up against the spring tension and doing so can DAMAGE YOUR COILOVERS!!! Instead, you undo the lock perches and spin/twist the entire shock BODY into and out of the base coupler of the shock and then follow by spinning the perches up to put just light tension on the springs...just enough to keep them from banging around when the suspension unloads. In the front this is easy...in the rear this gets more complicated because you need to be careful to keep the travel centered.
My question concerns keeping the travel centered with the install of the rear Ohlins coilovers on my 2007 MX5. The units were assembled according to the instruction sheet supplied by Ohlins, with the required items transfered from the oem units. The preloaded spring length is 198 mm as specified in instructions - just light tension - but this required the spring perches to be 5 mm lower than Ohlins specified. The distance between the bottom of the lock nut for the spring perch and the top of the lock nut for the height adjustment is now 14 mm instead of the specified 19 mm. Unfortunately, I forgot to record my measurement of the length of the exposed shock shaft to the bottom of the bump stop. Installed on the car, I measured from a point on the underside of the top mount to a reference point near the bottom of the shock. This measurement differs by 56 mm between the car sitting with tires on the ground and with tires in the air. So, it appears that I have a little over 2 inches of droop or full extension travel. I do not know how much bump or compression travel I have. What is the total travel measure for the rear Ohlins shock? Is my travel "centered"? If I need to increase bump travel and decrease droop significantly, how do I do it without cranking the spring perch up against spring tension to the point that it may damage my coilovers? With 200 miles of driving, I am very impressed with the comfort and handling transformation that these coilovers provide.