In reply to a message from DQ81 sent Wed 25 Nov 2009:
Please be very careful when not using shocks recommended by the
automobile manufacture. It could be dangerous. They spent a great
deal of time and effort working with a specific shock manufacture
to get it right.
The goal of the other shock manufactures is to take your money –
anything close will do.
The proper valving for the bounce and joust spec of shocks is a
The weight of the car.
The spring rate
The weight of all the upsprung components: like Wheels, Tires,
Brake Rotors, Brake Calipers, the weight of the Springs, 1/2 the
weight of the ‘‘A’’ arms,
1/2 the weight of the shocks, 1/2 the weight of the anti roll bar
If you know all those things, I’ll get you a copy of the algorithm
to calculate the valving required for bounce and jounce…
Other wise, call Bilstein near SanDiego Ca US
Their phone number is on their web page.
They know all that stuff for every car they provided the original
shocks. In addition they can custom valve a set of shocks to your
liking. They will even match them. They can also rebuild and re-
valve your old Bilstein Shocks for $60 each. Check their web page
for international distributors.
Bilstein shocks are the only single tube shock manufacture. Their
shocks do not have the mechanism that wares out in all the other
brands. As some one mentioned, as other shocks get older they
become less effective, nice and slow so that you don�t notice.
The only failure mode associated with Bilsteins is they leak. When
the fluid leaks out they stop working and you get them rebuilt.
Don’t try and out guess the designers - they know all of the facts
required to calculate the proper valving. Every one else is
guessing or making decisions based on hear-say or rumor.
If you want your car to ride softer, put smaller diameter wheels on
it and pick touring tires that are equal in diameter to the
original tires. But it will not handle as well as originally
intended. Primarily because the side walls will not be as stiff.
And the contact patch may be smaller.
But, be very careful! Pay strict attention to the load rating. As
you and your car have not shed any weight and you do not want to
over work tires made for a much lighter car…
As usual, I have no affiliation with Bilstein. Simply a satisfied
The original message included these comments:
I need to replace the front shocks as it seems they bottom out.
Any recomendations on brands and vendors in the UK or
SpeedyPAL 1995 XJR
Milford / OH, United States
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