Installing and setting the XK120 torsion bars is a well worn subject area in the archives. I’ve surfed through several threads and remain befuddled … that in itself is not altogether surprising, and most of my questions are answered, but a few remain.
Exhibit “A”:
The workshop manual specifies the initial ‘distance between the top and bottom shock absorber mountings of 15-5/8” …On the XK 120 model this distance is between the centre of the shock absorber mounting pin and the lower face of the shock absorber top mounting hole.’
The manual helpfully provides a drawing of a “simple” (yeah, right) distance gauge that may be made up to facilitate the adjustment but it specifies two measurements, 15-5/8” and 13-3/8”. Ok, but what’s the latter measurement for?
To add to my confusion, reference is made in the archives to both distances between the shock mounts.
Second question has to do with the rubber bushing that’s covered by the torsion bar muff. It obviously has to be torqued down before the initial setting of the torsion bar, but all the other bushings are torqued down only after final ride height is set to avoid putting undo strain on them that could cause them to fail prematurely … so, what prevents the pre-loaded bushing under the torsion bar muff from being overstrained?
There will be a little bit of crush in that bushing, so if you wanna compensate for that, plus the general tendency to sag a little in as everything kind of beds in, add a half inch.
You put on all the A-frame suspension parts first, with the gauge or a piece of wood. That sets the normal riding height with no strain on the rubbers and no influence from the torsion bars.
Then you put on the torsion bars and adjust them to the riding height with all the weight of the car added. Trial and error, jack up the car when adjusting the torsion bar tensions, then let it down and see how you did. Don’t crank on those long brass nuts with all the weight of the car on them.
The way I’m reading the manual, Rob, the procedure is the same as for the E-type, and that is you fix the torsion bars in place and then you lower the car onto its own weight before you torque down the bushes. The difference here is that one of the bushes is covered over by the torsion bar muff so must be torqued down before the car is lowered.
aay, hooze yooze gonna berleeve, da manyouel er yers trooly.
Anyway, reassembly is the reverse of the disassembly procedure. You can tighten the nuts on the rubber bushes, just don’t move the arms a lot afterwards. Stay within the normal travel, don’t make the arms rotate on the bushes, just twist.
Another hint, you can put soap on the rubber. Then they will move easier and center themselves without damage. It comes off after a few miles. The manual says no lube, but they meant grease.
I agree about tightening that lower rear bush before covering it with the muff. I did my Mk 7 recently. Tighten the bush first in the mid laden position, then force the LCA down to the correct distance for the TB setting. Having said that, I found that the factory setting distance is rubbish (also with my E-type). Had to screw the adjuster all the way in to the limit to almost get an acceptable ride height, after removing the muff & adjusting it by 1 tooth for the 3rd time (will have to do it again to get the adjuster in the middle of the range).
Hi Nick…re the muff bush…my 150 suspension is almost ready to reassemble and i have been thinking about the tension in the bush under the muff…i was thinking about assembling loosish and setting torsion bar and ride height…then once happy with the height and the suspension settled mark up the torsion bar/muff position…then undo and slide back the muff and tighten bushes in their ride height position…then refitt…this is the only way i can see to do the job…but i might be overthinking…is it really necessary. …Steve
Hmmm… muff bush…I did both my Mk7 and 120 by setting the lower wishbone to the service manual distances as shown previously, I used VERY simple 3mm fencing wire double twisted so minor adjustments could be made either way by tightening or loosening the twist (sorry no photo). My theory was that by setting this correct or neutral ride height, this would represent the “loaded” position of the car and suspension. I tightened the bushings to this height. So far so good, but I’m no expert.
Dave.
