The subject of tube shock conversions was mentioned in the MGB Driver a
couple of months back. If you look at any of these kits they all have
the same basic design (Unless your talking coil over spring or Ron
Hopkins kit). There is a braket that fits over the exising shock (which
is retained minus the damping valve). This bracket is held in place by 2
long bolts. which pass through 2 long tubes and hold the new tube shock
braket in place.
Crude ASCII ART:
Bolt Bolt
____|----|_________|----|____
| || || |__________
| || || __________| Shock mounting point
| || || |
|___ || ________ || ___| |
| || | | || | | Force
| || | | || | |
|
..... \/
| || | | || |
|__||__| |__||__|
|| ||
The problem is the force from the shock is not passed straight down the
bolts but instead causes a bending moment which sometimes causes the
bolts to shear. This causes a loss of damping as the shock is no longer
fixed and can also cause a break in the brake line causing a
loss of braking (especially in some version which have the brake line
attached to the bracket). (I'm not a mechanical engineer but I had to
take a course on strength of materials when I got my engineering degree.
Maybe one of the mechanicals on the net can do a better job explaining
why).
Sufice it to say if you have one of these kits (And I do) keep a close
watch on the bolts holding it on and recheck them regularly. If you
don't have one of these kits I would think twice about getting one.
Classic and Sportcar June 1991 compares a number of these kits and says
that the original lever arms in good condition is one of the best
choices, and the Moss coil over spring which tubes in the rear is a good
upgrade. They give failing grades to all other upgrades.
Sorry for rambling on so much.
Gary
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Electronic Signature: Gary R. Burrell P.Eng. (burrelgr@tuns.ca)
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