Lotus Elan

bump gauge

PostPost by: twincamman » Fri Mar 11, 2011 5:41 pm

make one of these and save a buck also good for set up --a piece of aluminium and an angle - degree gauge [or pitch and angle locator ] from a house builders shop does caster camber and bump steer -ed
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dont close your eyes --you will miss the crash
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PostPost by: frearther » Fri Mar 11, 2011 10:09 pm

Got instructions for us technically challenged types?
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PostPost by: twincamman » Fri Mar 11, 2011 10:32 pm

it was made for 13 inch wheels so its about 16 inches overall length --has 2 90 degrees and a 45 degree and a short straight bit and has a couple bolts long enough to clear the tire bulge and contact the rim top and bottom ---not hard --I built it by eye -the next one would be 1/8 or 1/4 aluminum plate -the only critical measurements are the 90 s and the bolt to wheel rim distance -ed
dont close your eyes --you will miss the crash
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PostPost by: ceejay » Sat Mar 12, 2011 12:54 am

Your well made tool might be OK for camber/caster check but when setting the bump steer, the gauge
would need to be held firm in a horizontal position for the two pegs to make contact with the rim at
centre height, bump steer is checked by raising and lowering the front suspension (with a floor jack) with the
shocks or springs removed, various thicknesses of shims are placed under the steering rack
or removed... which ever the case may be in order to achieve the desired result through testing.

As the front of the chassis/suspension is raised and lowered through the normal travel arc, the distance
between the front and rear peg of the gauge is measured, basically, all you are trying to acheive is to
place the rack in the best possible position on the mounting brackets to minimise or eliminate toe in
and toe out which can make your car dart to the right or the left on a sharply undulating road surface,
or during braking. When the shim/rack setting is correct, the measured distance between the front &
rear peg on the gauge will be almost the same... but you may not get it perfect.

It is possible to spend many hours tweeking and getting things right, but once it is done,
a remarkable difference will be noticed in the way your elan handles.
If you really want to get into suspensions and handling, get the book of
"How To Make Your Car Handle" by Fred Puhn, it is well worth the money.
Amazon have it.

The next best thing after the bump steer problem is cured, is to find a suspension tuning
centre who know their stuff, laser alignment is the most accurate system to set up both front
and rear suspension on the elan... providing both front and back have adjustable wishbones.
(I'm sorry if I upset the purists, but I don't subscribe to old Chappers
"Make it adjustable and they'll get it wrong" theory.

The benchmark is always the std setting or specs, but if there are provisions to make
adjustments, you may find a better setting + or - side of the original spec.
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PostPost by: twincamman » Sat Mar 12, 2011 1:56 am

yes a helper can hold it in place or raise and lower the car while you do one or the other and read the plus and minus degrees on the gauge as the suspension travels its arc ----or racer tape [ used to be called tank tape -but they don't race tanks anymore] it works if you wish build an attachment to hold the unit in place via the wheel holes or wheel studs '. this was in the plan but I have friends to help and drink my Fosters -the famous quote was meant for hackers who didn't know sh2t from peanut-butter ---or you can spend your money and take your chance --either way suits me -ed
dont close your eyes --you will miss the crash
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