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11 February 2001 |
(See end
of article for useful/relevant part numbers)
Time to
arrange all those agonised over, carefully selected and applied suspension
components to give of their best.
This is one
of those subjects viewed as a ‘black art’, largely because of lack of
understanding and confusion. The confusion part is because folk encompass the
whole suspension set-up deal with suspension arrangement and design, lack of
understanding instilling terror at the thought of ‘fiddling’ with the
suspension components. The latter also fuelled by the knowledge that expensive
specialist measuring equipment is needed. Well, there is no black art – you can
work the magic. More a case of a long day’s labour made easier by having an
assistant. Only simple equipment is needed, and the relevant measuring
equipment is available at real DIY money.
Ground level
The first
– and essential - requirement is a level surface on which to work your magic. A
surface with any gradient will cause the suspension to tilt in that direction,
subtly affecting geometry readings in the case of mild gradient. Wildly
altering it in the case of an ‘Everest’ one. I’m sure you’ve all observed the
way your Mini’s suspension seems to have sunk on one side or the other (front
and rear too) when parked on a gradient. That ‘sinking’ alters the significant
suspension geometry angles. Whilst an absolutely flat floor is the pinnacle of
surfaces to work on, the average concrete garage floor will be – through the
nature of its construction – pretty much there.
Check the
selected area with a builder’s spirit level and long, straight piece of wood,
metal tube, angle iron, etc. If the surface is far less flat or more graded
than it appeared to the naked eye – no problem. All that’s needed are four
square pads made in wood to sit under each wheel/tyre, linked by two long
boards to hold them in position – one for the front and one for the rear. Set
the car where desired, then draw squares around the wheel/tyre to floor contact
patches with chalk Ideally, and if feasible/allowable – check with your parents
first kids – paint them on for future use. Shift the car out the way, and set
the pads down on the marked squares, then lay boards across these. Using a builder’s
spirit level, shim the pads with thin material (‘lino’ squares are ideal for
this) until the pads/boards are level side to side, front to rear, and
diagonally. Take your time and get this right. Once happy, use some
self-tapping wood screws to hold everything in place. Mark the boards with
their corresponding ‘ends’, and the floor positions if allowed. The pads don’t
need to be hi-rise affairs, so keep this set-up as low as possible – 2” thick
pads are a pain to push the car up on to! Sorted – you now have a sound base to
work on.
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Click image to enlarge. |
(Pic 1)
Simple
way of creating a level surface. Keep pads as low as is practical, otherwise
ramps will be needed to get your Mini on ‘em!
Hi-Tec tooling
One of
the factors frightening most folk off dealing with their suspension – specific
measuring equipment. Heightened by visions of laser/optical geometry setting
systems seen in use at your local wheel/tyre fitters and a supposed degree in
rocket science to operate it, or complex free-standing equipment used by
various race teams observed at circuit paddocks. They use these because they
can or have the budget to do so. This is over-kill for you and me. Fortunately
there are some very basic alternatives that will allow surprisingly accurate measurement
for minuscule investment that are as easy to use as a ruler.
The list
of essential tools – except the necessary spanners/sockets to make any
adjustments - goes like this:
A piece
of string long enough to go completely around the car. Builder’s nylon
string/plumb line string is spot-on for this.
Tracking
gauge. In descriptive terms, nothing more than a large ‘G’-clamp with a
scaled/measured adjustment is needed for width comparison. Easily made if
suitable materials are available, or far easier bought. The cheapest, most
basic example is made by Min Tec, available through Mini Spares/Mania costing
around a measly £35.00. Cheap or what?
Caster/camber
gauge. An instrument capable of measuring vertical angles in degrees/parts
there-of. Not so easy to make – the scale being VERY difficult to compile and
draw. Again there’s no need – Min Tec to the rescue once more via Mini
Spares/Mania costing around £37.50.
Lastly, a
pad and pen to record everything you do on. Keeping detailed records are
essential when further alterations are made to fine-tune the suspension to your
tastes.
Both
Tool10 and Tool11 are, whilst being extremely cheap and basic are supremely
easy to use, very accurate, and come with easy instructions. And that’s it. For
the price of having some ham-fisted mechanic rearrange your suspension to what
you ask (hopefully) you can do it a thousand times at home! Unabashed plug?
Maybe, but it’s for YOUR benefit.
Line a-stern
Initially,
centralise the steering rack as detailed in the jolly old workshop manual
(wordage and space is at a precious premium here!), and set the front tracking
to ‘straight ahead’. Set tyre pressures correctly and accurately, then get your
pride and joy up on the pads ensuring the wheels are as straight ahead as
possible. Push it on. Don’t jack it up then place the pads underneath. You’ll
need to avoid jacking the car up where at all possible as it seriously affects
the settings by disturbing your carefully set ride heights. When jacking is unavoidable,
once the car’s been set down, roll it backwards and forwards several times
whilst joggling up and down on the sills (doors open of course!) then leave to
‘rest’ for a couple of minutes. This will help settle the suspension down
again. Having some wooden 'wedges' made to use as ramps to push the car up on
to the blocks will help immensely - the longer the better.
Now to
establish that all your efforts in ensuring the shell is straight and square
and subframes in the right positions as detailed in previous ramblings have
been successful. To do this, tie one end of your string to a suitable point
level with, or near to, the wheel centre height. Go round the car, passing
through the centres of each wheel, and back to the front (or rear – where-ever
you decide the best anchor point is). The string needs to be touching the
tyres, so if arch extensions are fitted and will prevent this, they need to be
removed. If arches are permanently attached this obviously isn’t on.
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Click image to enlarge. |
(Pic 2)
String must
pass all way round car, through wheel/tyre centre-line, and be touching the
tyre sidewalls. A double-check for front to rear subframe/suspension alignment.
With front tracking set at straight-ahead, there should be a gap between the
string and leading edge of rear tyres. No gap suggests massive toe-out – VERY
dodgy. The gap should be even. Get it sorted before going further.
What will
be needed here are four blocks of wood, or some other item that will do a
similar job. These blocks need to be attached to the tyres/wheels, one on each
tyre/wheel arranged at wheel centre height, to the rear of the tyre/wheel at
the back, and the opposite at the front. Tank/duct tape can be use to stick
them on. By necessity they need to be thick enough to get the string away from
the arches, and must be of near-exact size in this respect.
Check the
front wheels are straight-ahead, and the string is touching both edges (front
and rear) of both tyres or blocks. Now inspect/measure the leading edge of the
rear tyres where the string passes. There should be a gap between the leading
edge and the string. If you got the subframes/shell square the gap each side
will be more or less equal. If wildly out – more than say 1/16”, you need to
sort out why, and correct it – be this a bent radius arm or mis-aligned
subframe. If it’s a 1/16” or less – this can be sorted when doing the tracking.
Make a note of which side has what gaps, and remove the string. Having done
that – it’s on with the show!
Geometry
juggling
The first
detail to set is the rear tracking. The reason for this is simple – adjustment
in rear tracking affects rear ride height, but DOES NOT affect camber. Rear
track is altered by moving the radius arm pivot shaft ends backwards or forwards.
Marginally affecting ride height when using outer end track/camber adjustable
brackets or fitting shims between the bracket and subframe, more seriously when
camber (fixed or adjustable) only outer brackets are used. The latter because the inner end has to be
moved backwards by elongating the mounting hole where toe-out exists before
correction. It shouldn’t, but has been known – especially where pattern
subframes and some negative camber rear brackets are used. This moves the
suspension knuckle socket backwards, which raises the rear suspension height.
Set the
rear tracking by either using the facility built in to the brackets you may be
using, adding shims between the outer bracket and subframe to add toe-out
(reduce toe-in or give toe-out) or elongating the inner pivot shaft hole in the
required direction. Backwards to reduce toe-in, forwards to add toe-out where
an extreme amount of toe-in is present, and not sort-able with outer shims. If
elongating the hole, a filler-key will need to be produced to stop the arm
moving back to its original position. Don’t forget to do the
rolly-bouncy-settley thing after any jacking up. As a starting point, set them
at 1/16” toe-in.
Rear
camber should now be set whilst you’re at that end, and if you have adjustable
brackets. Personally I can’t see the point in using static camber brackets, as
these maintain any side to side differences your car started out with, and too
much negative camber isn’t good. Initial setting here is ‘straight up’ – zero
degrees camber.
Now set
the ride height to where you want it. In the absence of any consistent and
deadly accurate measurement points – use wheel centre to arch peak distance, or
(what I do) is use sill edge to floor (pad level). Both providing there aren’t
any obvious deviations from the standard line. Assess which will give you the
most accurate readings. Folk have their own opinions on which is the best way
to achieve this – personally I remove the bump stops, lower the car as far as
it will go, then winch it up from there. Mainly because having tried it the
other way, I found a certain amount of ‘settling/sagging’ occurred. Adjust both
fronts and rears the same amount, do it in small amounts, and never keep
adjusting one corner. It will seriously affect the corner weights/stability
(more in another article). Raising one corner will usually also lift the
diagonally opposite corner a little. Again – do it a little at a time and
measure ALL FOUR corners each time. Ride height suggestions are a bone of
contention. I’m going to outline the effects in another article some time; for
now just don’t go too low. Lowest I would say is just off the front bump stops,
and ¾” higher at the rear. Once happy with the ride height, press on.
Take a
set of readings off the front for caster and camber to be your initial
guidelines. Caster angles are next, adjusted by altering tie-rod length. These
need to be as even as possible. If you are using fixed-camber bottom arms, as
long as the readings are within half a degree with exact caster angles each
side, it’ll be OK. Three quarters of a degree can be tolerated, but starts
having a negative influence on the handling. When using adjustable bottom arms,
once an adjustment is made you will have to go back to check/re-set caster.
Initially use 3½ to 4 degrees caster, and 1-degree negative camber (1/2-degree
negative camber for 13” wheel/tyre combinations).
Finally,
set the front tracking as any adjustments to caster or camber will alter the
tracking. Very straightforward operation. Don’t be tempted to adjust one side
only if there’s a lot of adjustment to be made (more than 1/32”). Do a bit on
each side to keep the rack central. Initial setting here is 1/16” toe-out.
Round-up
I wish to
repeat – this is a very basic set of set-up guidelines. There are other ways –
but this is the most straightforward for the ‘amateur’. Take your time, and be
consistent with measuring points, measurements and adjustments. Persevere to
get it spot-on, not ‘that’ll do’. Once set up; drive the car around for a few
days, then double check it all as some settling will undoubtedly occur.
Bump-steer and stability/corner-weights will be dealt with in a separate
article.
Useful
part numbers:
|
TOOL10 |
Caster/camber gauge |
|
TOOL11 |
Tracking gauge |
|
|
Pair adjustable |
|
HILO-01 |
Pair
rear struts and plastic plugs to use |
|
|
Front |
|
HILO-04 |
Rear |