Y 6486 - Rear Shock Absorber conversion
By Gilles Bachand
Before reading this, you
must first read what Richard Prior has written on the subject. The
following information is complementary.
The shock absorbers I
used are KYB Gas-a-just #552-018: available from minispares.com They seem to have been recently discontinued as they do not appear in
KYB's current catalog. However, many Classic Mini parts suppliers still have
them in stock.
● Extended: 12 ¾ inches between eyelet centers
● Compressed: 8 ½ inches between
● Total travel: 4 ¼ inches.
I asked a talented machinist to laser cut the upper mounting bracket from
Richard's drawing and in 3/8 inch steel. They do not need to have an opening in
them when designed for a YA. The emergency brake (hand brake) cable follows a different
route from a YB.
designed new lower mounting brackets which would replace the stock Lower Spring
This is the
rough sketch I sent to the machinist.
dimensions are in inches. These pieces were laser cut. To ensure that the 3/8
bolts I would use could comfortably fit in the holes, they had the latter be
cut 0.010 inches bigger. This is not necessary if your parts are prepared in a
more traditional fashion.
assembled with the shock absorbers, the parts looked like this:
I used Grade
8 bolts, 3/8 inches in diameter and with fine thread (24 per inch).
They are 4
inches long to attach the upper bracket to the frame and 3 inches long to
attach the shock absorbers to the brackets.
cases, the threaded section is a bit too long for our needs. The reason I chose
those lengths is that the non-threaded section is present where the shock meets
a bracket or when the upper bracket meets the chassis. This provides maximum
washers were used to avoid the shock absorber body being too close to the
can be torqued to 30 ft/lb. (Remember, these are Grade 8 bolts)
thing to think about is that you must redesining the rear axle rubber bump stops.
Maximum shock absorber travel is 4 ¼ inch. When mounted on the car, the shock
absorber must not be allowed to hit its limit or else it might self-destruct.
Therefore, I reduced its travel by ¼ inch in either direction by having the
rear axle reach the rubber bump stops that much earlier. The lower rubber pad
is now ½ inch thick. As for the new upper rubber bump stop, look at the
difference with the original one:
the new bump stops from a bow rubber stop used on a boat trailer:
I glued the
new rubber parts on the existing steel straps with an extraordinary glue named
E6000. You can read
more about it here: http://www.eclecticproducts.com/e6000_retail.htm I bought a
3.7 oz tube on Ebay for $6.
that this measurement is such when the rear axle is resting on the lower bump
recommended that you change the U-bolts whenever you work on the leaf springs,
particularly if they are old, because they will have stretched and
submitted to much stress already. I have ordered a new set from