Leaky Dampers = No Chance of an MoT
Posted: Thu Mar 24, 2016 9:37 pm
Guess what? After 20 years of standing around, and 5 years of hard use, my rear dampers were leaking. Both of them. So, an easy replacement job, right? Wrong.
My coilover dampers were supplied by SPAX, who in the intervening 25 years have gone bust, and been resurrected again, but unfortunately with a much reduced product inventory. And there's more good news – pin-mount dampers such as mine are no longer available.
Anyway, this is what the old units looked like in situ...
...And the detail of how the pin-mount interfaces with the chassis...
Whatever I replaced the SPAX units with would need to use a standard 1/2” bolt fitting at both ends, so I bought a couple of chassis brackets from Demon Tweeks and then took advice from my friend Graham, who has been through this whole business with his Kudos hillclimb racer. Graham advised using AVO dampers, double adjustable (i.e. bump as well as rebound), with spherical joints at each end instead of rubber bushes.
I did a LOT of measuring before ordering the replacements. This was because the position of the top eyelet would shorten the effective length of the coil/damper unit by about 20mm, and I didn't want to run out of ride height adjustment. Eventually I settled on the 17” open/9” closed option, for 1.9” ID springs. Then I waited...
3 weeks passed, and a heavy parcel arrived, also containing a pack of 4 high angle spherical joint spacers for the lower wishbone mountings (originally designed to take bushed fixings). The dampers look fantastic, black painted with red anodised aluminium spring collars, the bottom one complete with a locking screw (nice touch that). The bump and rebound adjusters have blue and red anodised knurled knobs to make adjustment even easier. I arbitrarily selected rebound to face outboard, as I think I will probably need to access this one more often than bump.
Following a well-established ritual, the old damper was removed from the nearside. This is what it looks like off the car...
I replaced the old rubber top mounts with Poly bushes a few years back, but other than that you can see they are pretty tatty. My rear dampers have 4 clicks of rebound adjustment dialled-in and in spite of the oil leak were still working OK (in fact I had to reset the rebound to zero before I could extend the damper by hand).
I swapped over the main spring and helper spring onto the new damper and doesn't it look smart?
An abrasive wheel attachment on the angle grinder cleaned up the flat surface of the chassis around the original pin mount hole, and I used an old coach bolt to locate the new bracket ready for welding.
Of course, welding upside down is never much fun, and I had the added complication of freshly painted calipers and gearbox that needed protection from welding sputter (you've seen my welding, right?). So I covered all of the vulnerable areas with rags and dampened them with water just in case. It's amazing how fast an oily rag goes up when a particularly fat blob of molten metal drops on it, ask me how I know. Still, my welding gauntlets came in handy for beating out the flames, and the car was absolutely fine!
After tacking the sides of the bracket into place I removed the coach bolt, zipped up the sides and outside edge and plug-welded through the pin mount hole for good measure. Most of the force through the bracket will be in compression anyway, with only a small proportion in shear.
With a bit of etch primer and some chassis black the end result looks quite presentable...
With the nearside done I repeated the exercise for the offside damper, and before long the car was back on its wheels again, this time with brand-new, leak-free dampers! Using the longer of my two 325 lb springs (11.5” open length) the spring collar is at its maximum adjustment, so I cannot reduce the ride height, but I do have a spare pair of 10.5” springs of the same rating, for when I get those really fat, tall profile rear tyres for my Compos...
I will almost certainly replace the front dampers as well at some point, but right now they are not leaking so should be OK for an MoT. So fingers crossed, that is all the chassis work done.
Lauren
My coilover dampers were supplied by SPAX, who in the intervening 25 years have gone bust, and been resurrected again, but unfortunately with a much reduced product inventory. And there's more good news – pin-mount dampers such as mine are no longer available.
Anyway, this is what the old units looked like in situ...
...And the detail of how the pin-mount interfaces with the chassis...
Whatever I replaced the SPAX units with would need to use a standard 1/2” bolt fitting at both ends, so I bought a couple of chassis brackets from Demon Tweeks and then took advice from my friend Graham, who has been through this whole business with his Kudos hillclimb racer. Graham advised using AVO dampers, double adjustable (i.e. bump as well as rebound), with spherical joints at each end instead of rubber bushes.
I did a LOT of measuring before ordering the replacements. This was because the position of the top eyelet would shorten the effective length of the coil/damper unit by about 20mm, and I didn't want to run out of ride height adjustment. Eventually I settled on the 17” open/9” closed option, for 1.9” ID springs. Then I waited...
3 weeks passed, and a heavy parcel arrived, also containing a pack of 4 high angle spherical joint spacers for the lower wishbone mountings (originally designed to take bushed fixings). The dampers look fantastic, black painted with red anodised aluminium spring collars, the bottom one complete with a locking screw (nice touch that). The bump and rebound adjusters have blue and red anodised knurled knobs to make adjustment even easier. I arbitrarily selected rebound to face outboard, as I think I will probably need to access this one more often than bump.
Following a well-established ritual, the old damper was removed from the nearside. This is what it looks like off the car...
I replaced the old rubber top mounts with Poly bushes a few years back, but other than that you can see they are pretty tatty. My rear dampers have 4 clicks of rebound adjustment dialled-in and in spite of the oil leak were still working OK (in fact I had to reset the rebound to zero before I could extend the damper by hand).
I swapped over the main spring and helper spring onto the new damper and doesn't it look smart?
An abrasive wheel attachment on the angle grinder cleaned up the flat surface of the chassis around the original pin mount hole, and I used an old coach bolt to locate the new bracket ready for welding.
Of course, welding upside down is never much fun, and I had the added complication of freshly painted calipers and gearbox that needed protection from welding sputter (you've seen my welding, right?). So I covered all of the vulnerable areas with rags and dampened them with water just in case. It's amazing how fast an oily rag goes up when a particularly fat blob of molten metal drops on it, ask me how I know. Still, my welding gauntlets came in handy for beating out the flames, and the car was absolutely fine!
After tacking the sides of the bracket into place I removed the coach bolt, zipped up the sides and outside edge and plug-welded through the pin mount hole for good measure. Most of the force through the bracket will be in compression anyway, with only a small proportion in shear.
With a bit of etch primer and some chassis black the end result looks quite presentable...
With the nearside done I repeated the exercise for the offside damper, and before long the car was back on its wheels again, this time with brand-new, leak-free dampers! Using the longer of my two 325 lb springs (11.5” open length) the spring collar is at its maximum adjustment, so I cannot reduce the ride height, but I do have a spare pair of 10.5” springs of the same rating, for when I get those really fat, tall profile rear tyres for my Compos...
I will almost certainly replace the front dampers as well at some point, but right now they are not leaking so should be OK for an MoT. So fingers crossed, that is all the chassis work done.
Lauren
