I have not watched "The Blues Brothers", for quite some time but, "Yes I
have seen the light"! I've been thinking about this all week so here goes.
Brainwave number 1.
Terry mentioned last week about having the steering wheel positioned to a
mark stamped on the column. I now understand why. It is because the steering
arm on the bottom of the steering box and the idler arm swing through an
arc. So if the wheel and column are not aligned, it would mean the
steering/idler arm are pointed to one side of the car or the other. Doesn't
sound to bad except that they swing through an arc. This means that it is
possible to get more bump steer on one side than the other. This is because
the arm can swing up more on one side than the other which causes greater
suspension geometery changes on one side than the other. At Phillip Island I
noticed that I had difficulty turning left (bump steer) but not to bad when
turning right. I know that my steering column is not centered.
Brainwave number 2.
Lowering the car causes bumpsteer due to changes of the control arm angle.
Ok already new that but, thought I'd put it in anyway. But if harder springs
increase the feedback to the steering wheel then so to wouldn't bumpsteer
feel worse? Please correct me if I'm wrong on this one.
Brainwave number 3.
Ok we all know that the 1600 steering boxes can be a bit vague. We also know
that to reduce bump steer we need equal length contol arms and steering arms
(tie rod ends) and that the inside pivot points for both need to be at the
same height. This must be the reasons behind the different std 1600 setups
from early to late models for the strut and steering setups etc. So leeding
to the next brainwave, go to rack and pinion steering (on a race car anyway,
street car need engineering cert of course).
But how?
Option 1. Go for a rack the same length as the 1600 steering ie with the
same positioning as the pivot points on the crossmember for the lower
control arms. OK find but in the past I looked at this and couldn't find
anything at the wreaker of the right dimensions.
Option 2. Find a rack of roughly the right dimensions (possibly bluebird?)
and then change the pivot points on the crossmember to match the racks pivot
points. Make the pivot heights the same on the rack and crossmember to keep
the radius of the arc of the lower control arm and tie rod the same. Looks
like tommorrow I will be off to the wreckers again to have a look at rack
and pinion setups.
Finally regarding rod ends has anyone on the list performed this mod to
their lower control arm, and where do you buy them for reasonable prices?
Also what size do you buy?
Thanks
Trev
I can verify that the crossmembers of 68 510s do indeed have a higher
mounting point. I recently did the change over and while both crossmembers
were out I calculated that the '68 was 1cm higher, and that is enough to
make a small difference. I do still have bumpsteer but considerably less
than with the 71 crossmember!
zac
Only way to go on a race car!
It allows the lower arm to pivot on the control arm pivot shaft with no
side loading on the shaft due to increased caster.
Cheers
Feral Errol
----------
From: Craig Harris <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Subject: Re: Front suspension for racing
Date: Wednesday, August 23, 2000 8:30
Are
"rod ends where the lower control arm joins the crossmember"
like threaded rose joints? I would be interested to see who has done these
on a 510 and what they think about them. a mate has just done them on a
toyo
and they look pretty trick
any thoughts/experiences??
-----Original Message-----
From: Errol Smith [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, 23 August 2000 22:02
To: [EMAIL PROTECTED]
Subject: Re: Front suspension for racing
Pete,
If it means the pivot point of the arm and the tie rod are moving about a
common axis, Yes.
If the tie rods remain in the same position and the arm pivots are moved
upwards, this could make things worse depending on the rate of spring used
and as a result the degrees of arc the arm moves through under bump or
droop.
If you really want to see if you have bump steer. make up some straight
lengths of timber and connect to a heavy object to hold the timber in
position against the wheel, horizontally below the wheel centre line. Run a
string line along the line of the timber to establish the direction the
timber is pointing.
Jack the cross member up 50mm and let it return to rest. Check the pieces
of wood for movement from their original position. If the pieces of wood
have moved from their original line, you have bump steer.
Then get 2 or 3 persons to press down or sit on the guards and bonnet of
the vehicle sufficient to cause the suspension to become lower at rest.
Check the boards again for movement from the original line.
Cheers
Feral Errol
----------
From: Pete & Kath Liebig <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Subject: RE: Front suspension for racing
Date: Wednesday, August 23, 2000 8:41
Errol,
But just moving it upwards should do the trick to fix bumpsteer - yes?
Gotta be the cheap and easy way to go for a guy with a die grinder and a
MIG...
'later
PL
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]] On Behalf Of Errol Smith
Sent: Wednesday, 23 August 2000 19:18
To: [EMAIL PROTECTED]
Subject: Re: Front suspension for racing
Chris,
The problem with moving the lower control arm pivot point out is that the
lower control arm and tie rod then end up describing different arcs in bump
or droop conditions. This causes bump steer!
If you check out the current Nismo catalogue, they offer strut spacers for
the following vehicles and have had them on sale for some 15 years.
3/4" Aluminium spacers for 240, 260, 280 & 280ZX Z cars Part No
99996-34SPGR.
For 510, 610, 710, 200SX (S10 & S110) a 1" spacer is sold Part No
99996-10SPGR.
To quote the current Nissan Motorsport catalogue:-
" 1inch Aluminium spacer, Corrects lower control arm angle when ride height
is reduced. Also reduces camber change and bump steer. Fits between lower
control arm and strut."
Cheers
Feral Errol
----------
From: Chris Halpin <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Subject: Re: Front suspension for racing
Date: Thursday, August 24, 2000 9:15
Trevor,
Are you driving this car on the road? If not....Have you seen Peter's? He
lives in Melbourne. I just got some springs off him the other night, and
he's a really generous guy - seems willing to share his knowledge too. He
has actually changed the pivot point on the X-Member, thus changing the
control arm angle drematically, and also giving more camber and a wider
track width at the front end. I personally think It's a great idea to
eliminate the need for bump steer spacers, and also the need for longer
control arms. He says it works well.
Chris
>From: "Pooley, Trevor" <[EMAIL PROTECTED]>
>Reply-To: [EMAIL PROTECTED]
>To: "'[EMAIL PROTECTED]'" <[EMAIL PROTECTED]>
>Subject: Front suspension for racing
>Date: Wed, 23 Aug 2000 16:18:40 +0930
>
>Unless you fork out $1600 for a set of 55DCO/SP Webers from DatRats (
>drooooool ). I agree!
>
>Talking about datrats. I've just recieved a set of 30mm bump steer spacers
>from Datrats (one tenth the cost of the 55's). They look real good (nice
>shinny alloy) and will restore some angle to my lower control arms after
>the
>lowering job I did last week before phillip Island. I had some minor bump
>steer there.
>
>This leads to my next question. There was some talk a little while back
>about the location of the pivot point on the engine crossmember.
Apparently
>the early model had these higher up than the latter models. Can anyone
>confirm this? Also after looking at the pics of the busted cross member,
is
>it worth modifying mine or just looking for a good early 1600 crossmember?
>Does the distance between the two pivot points change as well or just the
>height?
>
>Other thing I want to do is make new adjustable lower control arms to
>replace the datrally ones I am currently using. I would like to either go
>for a monoball arrangement (ie How to hotrod your datsun book) or rod ends
>where the lower control arm joins the crossmember. This would allow for
>lots
>of positive castor without stressing the pivot point. Does anyone know of
a
>cheap source for these parts.
>
>I am also looking into making a rear sway bay (ie How to hotrod your
datsun
>book) but that might be asking a little to much too soon.
>
>Thanks
>Trev
>
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