The rear springs on my Delica have sagged (as they all do) to the point where they were sitting on the overload leaves, which makes the ride quite harsh.
I've tried adding a leaf which made the ride smooth again when loaded, but it also raised the rear too far when the van was empty. ("Too far" meaning it wouldn't fit through the garage door without letting all the air out of the tyres).
So I've removed the add-a-leafs and gone for an old-school solution- air adjustable shock absorbers.
Monroe MA708.
US$70 from Amazon.
Allegedly the same compressed and extended length as my Pro-Comp 919520's but I think they're measuring from different points, because these clearly have a *lot* more droop than the Pro-Comps. They're also slightly longer when compressed, presumably because they have internal bump stops, but by my measurements they shouldn't bottom out (and the internal bump stops should prevent any damage if they do).
They require a touch of modification. Remove the upper pin mount:
...and install the top bush from your old shocks (if it's removable. OEM shocks might have bonded-in top bushes, so you'll have to source something to suit):
Then you get excited and install them without taking any further photos. Sorry.
----IMPORTANT UPDATE----
I've had a couple of reports of the lower pin shearing off, like so:
It seems to be due to overtightening the lower pin and/or using old, hardened, crushed bushes:
The pin needs to be able to tilt in the bracket. You should use the nice new bushes that came with the shocks, and tighten the nut until there are 2-3 threads showing past the nut. The nut isn't a self-locking type, which is a bit cheap, so I used Loctite to ensure the nut won't come off:
Note that the top bush looks more compressed than the lower one- that's because there's 40psi of pressure in the shock pushing it down. Before I pumped the shocks up the bushes were evenly compressed.
Caution #2: The top mount might need a washer to space the shock body away from the chassis rail. The shock absorber body should not touch the chassis rail. A couple of millimetres clearance is fine.
And now, back to your regularly scheduled enthusiasm:
They work brilliantly so far. Just 30psi brings the rear end back up to standard height, lifting the tired springs off the overload leaves, and restores the smooth ride. With the caravan hitched up and a bunch of junk in the van it required 70psi to come back to standard ride height, and it tows without any wallow or pitching.
Monroe recommend 20-90psi continuously (so I'm well within the specs), or up to 150psi for short periods. Air shocks have a reputation for overloading the shock mount points when used on regular cars, but I figure our beefed-up 4WD mounts can handle it. (Or watch this space for a thread titled "Shock absorber mount point repair and strengthening".)
ANOTHER UPDATE: I've verified that these shocks are long enough with the standard bump stops.
Here's my van's measurements with the Monroe air shocks entirely deflated:
I estimated that the axle can move upwards by 30mm by measuring from the chassis rail to the clean, worn line on the bump stops, which is created when they deform from hitting the chassis rail. The actual measurement was closer to 25mm but I added 5mm for luck.
I measured the length of the shock at rest between the lower edge of the dust shield, and the weld on the lower part. At rest this measurement was 95mm. I undid the lower mounting nut and, using a crowbar for leverage, pushed the shock closed as far as it would go (not pictured). The measurement reduced to 60mm. 95mm - 60mm = 35mm of upwards movement possible.
So, from rest the axle can move upwards 30mm before the bump stop limits the movement. My shock absorber can move 35mm, which suggests that the shocks have 5mm more travel than I need. Not much margin for error, but good enough.
But wait, it gets better because the shocks are at an angle. 30mm of upwards movement at the axle doesn't mean they get 30mm shorter. Pythagoras to the rescue:
Math.JPG (234.99 KiB) Viewed 2469 times
When the axle moves 30mm upwards, the shocks only need to get 26mm shorter. The shocks have 35mm travel between rest and their bump limit, which means I have not 5 but 9mm more travel than I need. Awesome.
9mm would normally still be a bit close for comfort- the bump stops could probably deform 9mm further than usual under an extreme load. Fortunately the Monroe shocks have an internal bump stop, so even if they reach the limit of their travel they shouldn't be damaged.
I've tried adding a leaf which made the ride smooth again when loaded, but it also raised the rear too far when the van was empty. ("Too far" meaning it wouldn't fit through the garage door without letting all the air out of the tyres).
So I've removed the add-a-leafs and gone for an old-school solution- air adjustable shock absorbers.
Monroe MA708.
US$70 from Amazon.
Allegedly the same compressed and extended length as my Pro-Comp 919520's but I think they're measuring from different points, because these clearly have a *lot* more droop than the Pro-Comps. They're also slightly longer when compressed, presumably because they have internal bump stops, but by my measurements they shouldn't bottom out (and the internal bump stops should prevent any damage if they do).
They require a touch of modification. Remove the upper pin mount:
...and install the top bush from your old shocks (if it's removable. OEM shocks might have bonded-in top bushes, so you'll have to source something to suit):
Then you get excited and install them without taking any further photos. Sorry.
----IMPORTANT UPDATE----
I've had a couple of reports of the lower pin shearing off, like so:
It seems to be due to overtightening the lower pin and/or using old, hardened, crushed bushes:
The pin needs to be able to tilt in the bracket. You should use the nice new bushes that came with the shocks, and tighten the nut until there are 2-3 threads showing past the nut. The nut isn't a self-locking type, which is a bit cheap, so I used Loctite to ensure the nut won't come off:
Note that the top bush looks more compressed than the lower one- that's because there's 40psi of pressure in the shock pushing it down. Before I pumped the shocks up the bushes were evenly compressed.
Caution #2: The top mount might need a washer to space the shock body away from the chassis rail. The shock absorber body should not touch the chassis rail. A couple of millimetres clearance is fine.
And now, back to your regularly scheduled enthusiasm:
They work brilliantly so far. Just 30psi brings the rear end back up to standard height, lifting the tired springs off the overload leaves, and restores the smooth ride. With the caravan hitched up and a bunch of junk in the van it required 70psi to come back to standard ride height, and it tows without any wallow or pitching.
Monroe recommend 20-90psi continuously (so I'm well within the specs), or up to 150psi for short periods. Air shocks have a reputation for overloading the shock mount points when used on regular cars, but I figure our beefed-up 4WD mounts can handle it. (Or watch this space for a thread titled "Shock absorber mount point repair and strengthening".)
ANOTHER UPDATE: I've verified that these shocks are long enough with the standard bump stops.
Here's my van's measurements with the Monroe air shocks entirely deflated:
I estimated that the axle can move upwards by 30mm by measuring from the chassis rail to the clean, worn line on the bump stops, which is created when they deform from hitting the chassis rail. The actual measurement was closer to 25mm but I added 5mm for luck.
I measured the length of the shock at rest between the lower edge of the dust shield, and the weld on the lower part. At rest this measurement was 95mm. I undid the lower mounting nut and, using a crowbar for leverage, pushed the shock closed as far as it would go (not pictured). The measurement reduced to 60mm. 95mm - 60mm = 35mm of upwards movement possible.
So, from rest the axle can move upwards 30mm before the bump stop limits the movement. My shock absorber can move 35mm, which suggests that the shocks have 5mm more travel than I need. Not much margin for error, but good enough.
But wait, it gets better because the shocks are at an angle. 30mm of upwards movement at the axle doesn't mean they get 30mm shorter. Pythagoras to the rescue:
When the axle moves 30mm upwards, the shocks only need to get 26mm shorter. The shocks have 35mm travel between rest and their bump limit, which means I have not 5 but 9mm more travel than I need. Awesome.
9mm would normally still be a bit close for comfort- the bump stops could probably deform 9mm further than usual under an extreme load. Fortunately the Monroe shocks have an internal bump stop, so even if they reach the limit of their travel they shouldn't be damaged.
Last edited:
