lifespeed
02-21-2013, 03:23 PM
I have been fighting with rear suspension air spring and shock tuning for a couple weeks now. It is pretty close, but not perfect. Sharp bumps will bounce the rear of the car upwards, even with maximum rebound damping applied.
I am posting this to advise people about to replace their air springs that the Arnott Towncar/limo parts do not appear to be the same spring rate as the OEM Marauder parts. They are shorter, resulting in higher air pressure for a given ride height. Further, they appear to hit the internal bump stops with the fender lip about 3/4" below the tire tread. This will upset the rear of the car greatly, you want to make sure this doesn't happen under normal conditions.
Because I completely rebuilt the front and rear of the car (http://www.mercurymarauder.net/forums/showthread.php?t=84895)all at once it is a bit tricky to nail down who is responsible for what effects (Penske shocks vs Arnott air springs), but at this point I think I have seen enough to at least advise fellow Marauder owners to think carefully about the air springs they install in the car.
I am 90% sure I can re-valve the shocks with more rebound to control the Arnott springs properly for a good, albeit stiff, ride. The shocks were designed to be close to OEM Tokicos, so even with external adjustments can't quite accomodate the Arnott's without internal changes. Stiff is OK, IMHO, but insufficient damping (bouncy) is really irritating. As anybody who has messed with springs and shocks will tell you, they have to match. One cannot accomplish optimal results without a matched set. In general, with coil springs, stiffer springs require stiffer shocks to control them. I am starting to suspect the non-linear rate of air springs require more rebound damping than compression, which may be different than coil springs.
Given the dearth of shocks, let alone matched-rate air spring and shock combinations, Marauder owners should be very careful when selecting replacement parts. An error in spring rate and/or shock valving will easily degrade that firm, well-damped ride that every Marauder deserves.
My plan is to re-install the OEM air springs and re-evaluate the shock valving, spring rate and ride height-vs.-bump-stop issues. I will post results, hopefully with the perfect recipe Marauder owners can easily duplicate.
But for now, Caveat Emptor.
I am posting this to advise people about to replace their air springs that the Arnott Towncar/limo parts do not appear to be the same spring rate as the OEM Marauder parts. They are shorter, resulting in higher air pressure for a given ride height. Further, they appear to hit the internal bump stops with the fender lip about 3/4" below the tire tread. This will upset the rear of the car greatly, you want to make sure this doesn't happen under normal conditions.
Because I completely rebuilt the front and rear of the car (http://www.mercurymarauder.net/forums/showthread.php?t=84895)all at once it is a bit tricky to nail down who is responsible for what effects (Penske shocks vs Arnott air springs), but at this point I think I have seen enough to at least advise fellow Marauder owners to think carefully about the air springs they install in the car.
I am 90% sure I can re-valve the shocks with more rebound to control the Arnott springs properly for a good, albeit stiff, ride. The shocks were designed to be close to OEM Tokicos, so even with external adjustments can't quite accomodate the Arnott's without internal changes. Stiff is OK, IMHO, but insufficient damping (bouncy) is really irritating. As anybody who has messed with springs and shocks will tell you, they have to match. One cannot accomplish optimal results without a matched set. In general, with coil springs, stiffer springs require stiffer shocks to control them. I am starting to suspect the non-linear rate of air springs require more rebound damping than compression, which may be different than coil springs.
Given the dearth of shocks, let alone matched-rate air spring and shock combinations, Marauder owners should be very careful when selecting replacement parts. An error in spring rate and/or shock valving will easily degrade that firm, well-damped ride that every Marauder deserves.
My plan is to re-install the OEM air springs and re-evaluate the shock valving, spring rate and ride height-vs.-bump-stop issues. I will post results, hopefully with the perfect recipe Marauder owners can easily duplicate.
But for now, Caveat Emptor.