Lotus Elan and Lotus Elan Plus 2 Forums

My car was jacked up using the steering rack support. Some damaged
occured that has been repaired. However i'm worried about the shims
may need to be re-adjusted for correct settings. I cannot find any
references on how to do this test and adjust. Can anyone give me the
procedure to test.
Thanks
Jim

Jim,

The alignment condition or reference you are looking for is called "bump steer". It is an inherent condition on cars with rack and pinion steering.

Bump steer cannot be eliminated, only minimized by shimming the rack in the chassis so the steering links are leveled with the rack body. The intent is to minimize the self steering effect when the wheel or wheels hit a bump. The car wants to dart to one side of the road or the other.

A very good and simple procedure for checking and correcting for bump steer is in "prepare to win" by Carroll Smith. There may be some good explanations and procedures available with a google search.

Best regards,
Dan Wise

Message: 2
Date: Fri, 13 Jan 2006 06:42:00 -0000
From: "holywood3645"
Subject: Steering rack shims (re-shim)

My car was jacked up using the steering rack support. Some damaged
occured that has been repaired. However i'm worried about the shims
may need to be re-adjusted for correct settings. I cannot find any
references on how to do this test and adjust. Can anyone give me the
procedure to test.
Thanks
Jim




---------------------------------
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Photo Books. You design it and we?ll bind it!

If you check the archives of this list for "bump Steer" you will find a
number of threads on who to determine what shims to put in. Of course you
then need to determine how much bump steer you want for your driving style
which may be harder to do.

For a quick check, one of the books I have lists the distance from the lower
control arm inner pivot point to the base of the rack. From memory I think
this dimension is 2.5 inches, but I could be wrong.

Rob LaMoreaux

A & D Technology Inc.
4622 Runway Blvd.
Ann Arbor, MI 48108
734-822-9696
Fax 734-973-1103
Main Desk 734-973-1111
www.mtspt.com
Work email: ***@***.***
Home email: ***@***.***

Hi Rob,

I too would be interested in that dimension, since my rack will need fitting shortly. I will probably bump steer it, but it would be interesting to see how the default measurement compares with the individualized bump steer measurement.

Thanks!

Stan
If you check the archives of this list for "bump Steer" you will find a
number of threads on who to determine what shims to put in. Of course you
then need to determine how much bump steer you want for your driving style
which may be harder to do.

For a quick check, one of the books I have lists the distance from the lower
control arm inner pivot point to the base of the rack. From memory I think
this dimension is 2.5 inches, but I could be wrong.

Rob LaMoreaux

--- In ***@***.***, "Stan Aarhus" <saarhus@a...> wrote:

interesting to see how the default measurement compares with the
individualized bump steer measurement.






2.19 inches plus or minus .005"
This is from lower wishbone pivots to upper face of rack platform.
Regards
Dave-M

Dave,

Is the 2.19" measured from the wishbone pivot centre line, or the upper surface ? Also, as the pivots are tilted at the caster angle, at what position axially on the pivot pin is the measurement taken ?

Sean Murray

>
The correct dimension for the rack height for the elan and plus2 is
2.19 inches plus or minus .005"
This is from lower wishbone pivots to upper face of rack platform.
Regards
Dave-M

--- In ***@***.***, "Sean Murray" <snmurray@i...> wrote:

angle, at what position axially on the pivot pin is the measurement
taken ?


The information I gave was copied almost verbatim from the1984
issue 2 club lotus news. I admit it does beg your questions. However
it just so happens that I have the front suspension off my car and a
quick check answers the first of your questions. The 2.19 dimension
can only be from the top surface of the wishbone pivot shaft.
Regarding the fore and aft position for the measurement. No mention
is made of the actual position, but it cannot be at the shoulder of
the pivot as this falls behind the rack mounts so it must be done
centrally between the rack 'u' bolt holes. This is the only other
position that makes sense.
Bearing in mind the original check would have been done on a bare
chassis all the above would appear to make sense. Using a flat plate
suitably cut it would have been a quick and easy process and
providing the jig was not too bulky it can also be checked with the
body on the car. For the effort involved I think I will make one just
to check the shims on my cars.
Let me know what you think
Regards
Dave

Relationships are important 8^). The central issue is the front shock tower which carries the suspension mounting pivots and steering rack bracket. The positions of the steering rack mount and suspension pickups are perpendicular to the face of the shock tower and parallel to each other. The shock tower is rotated to the rear either 3 or 6, (some sources say 7) degrees to develop the caster, but since both the suspension pivots and surface of the rack are (or should be) parallel to each other, it doesn't matter where on the top surface of the pivot you measure from.

Stan
> >
Sean,

The information I gave was copied almost verbatim from the1984
issue 2 club lotus news. I admit it does beg your questions. However
it just so happens that I have the front suspension off my car and a
quick check answers the first of your questions. The 2.19 dimension
can only be from the top surface of the wishbone pivot shaft.
Regarding the fore and aft position for the measurement. No mention
is made of the actual position, but it cannot be at the shoulder of
the pivot as this falls behind the rack mounts so it must be done
centrally between the rack 'u' bolt holes. This is the only other
position that makes sense.
Bearing in mind the original check would have been done on a bare
chassis all the above would appear to make sense. Using a flat plate
suitably cut it would have been a quick and easy process and
providing the jig was not too bulky it can also be checked with the
body on the car. For the effort involved I think I will make one just
to check the shims on my cars.
Let me know what you think
Regards
Dave











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--- In ***@***.***, "Stan Aarhus" <saarhus@a...> wrote:

rack bracket. The positions of the steering rack mount and
suspension pickups are perpendicular to the face of the shock tower
and parallel to each other. The shock tower is rotated to the rear
either 3 or 6, (some sources say 7) degrees to develop the caster,
but since both the suspension pivots and surface of the rack are (or
should be) parallel to each other, it doesn't matter where on the top
surface of the pivot you measure from.

I Totally agree with you, relationships are important but maybe not
the one you describe.
If you check you will find the rack mount and bottom arm pivot shaft
are not parallel, at least they are not on my car.
It is not necessary for them to be parallel. It's the relationship
between top & bottom arm pivots and the tie rod ball joint which
control bump steer. The rack body can be mounted at any angle and is
on many cars. Typical examples amongst the cars I own are Mini &
Rochdale Olympic (a british fibreglass sportscar designed by Mr
Richard Parker who left Rochdale to work for Lotus in the sixties)
So I will stick to my original suggestion regarding measurement
between the rack "u" bolt holes, ie. on the rack ball joint centre
line
Regards
Dave

Dave,

Was Sherlock Holmes a family ancestor ? ("When you have eliminated the impossible, what remains, however improbable, is the answer ! )

I believe you have hit this on the head. It seem obvious now that the measurement would taken from the centre line of the platform between the u-bolts, to the contact point on the pivots immediately below that line.

Stan has also come up with another facet, the angle between the platform and the towers, which I (negligently) presumed to be horizontal. However, if the measurement is taken as you suggest, the actual angle of the platform would not significantly effect the rack centre line distance to the pivots.

I will now be fabricating a jig on the basis of your deductions, I have 3 chassis to check ! I will also be checking out the platform angles.

Sean

----- Original Message -----
From: dv_milner
To: ***@***.***
Sent: Saturday, January 14, 2006 2:52 PM
Subject: Re: [LotusElan.net] Steering rack shims (re-shim)


--- In ***@***.***, "Sean Murray" <snmurray@i...> wrote:
>
> Dave,
>
> Is the 2.19" measured from the wishbone pivot centre line, or the
upper surface ? Also, as the pivots are tilted at the caster
angle, at what position axially on the pivot pin is the measurement
taken ?
>
> Sean Murray
>
> >
Sean,

The information I gave was copied almost verbatim from the1984
issue 2 club lotus news. I admit it does beg your questions. However
it just so happens that I have the front suspension off my car and a
quick check answers the first of your questions. The 2.19 dimension
can only be from the top surface of the wishbone pivot shaft.
Regarding the fore and aft position for the measurement. No mention
is made of the actual position, but it cannot be at the shoulder of
the pivot as this falls behind the rack mounts so it must be done
centrally between the rack 'u' bolt holes. This is the only other
position that makes sense.
Bearing in mind the original check would have been done on a bare
chassis all the above would appear to make sense. Using a flat plate
suitably cut it would have been a quick and easy process and
providing the jig was not too bulky it can also be checked with the
body on the car. For the effort involved I think I will make one just
to check the shims on my cars.
Let me know what you think
Regards
Dave

--- In ***@***.***, "Sean Murray" <snmurray@i...> wrote:


between the u-bolts, to the contact point on the pivots immediately
below that line.

horizontal. However, if the measurement is taken as you suggest,
the actual angle of the platform would not significantly effect the
rack centre line distance to the pivots.

angles.

More Clueseau than Holmes I think.
One last point. If it is accepted that the correct measuring datum is
centrally between the "u" bolt holes. I think it is totally
irrelevant what the angle of the pivot pin or rack mount is. All that
is needed is the correct shim thickness on the rack centre line to
give the required dimension of 2.19" + or - .005" RELATIVE to the
lower pivot shaft.
Regards
Dave

Bung it together and drive it. If it feels bad, then try something
else but why bother with 005" when there is rubber in all the joints?
There is so much 'compliance' with an Elan ( flimsy chassis, different
body manufacturers, day of the week, state of company finance and
rubber everywhere and WHY!)
Have fun
Roy
'65S2

Roy

That's how I do it, and it works - just like out of the factory. I read all this stuff on steering over the week - took the S1 out for its weekly vigorous run yesterday and got a physiological twitch in my head that my steering "bumped" on me several times on some areas of my country road route.

After 43 years I think the b-tch can bump me as much as she wants, so long as she allows me to not P my pants as I drive and keeps me out of the verges.

I spent today watching our community sink a 737 Boeing airplane for a diving reef in the gulf islands, watch the Discovery channel extreem whatevers in the future.

keep your stick down

Bill 26/0538
I
Bill

12/0538
----- Original Message -----
From: Roy
To: ***@***.***
Sent: Saturday, January 14, 2006 6:18 PM
Subject: Re: [LotusElan.net] Steering rack shims (re-shim)


Bung it together and drive it. If it feels bad, then try something
else but why bother with 005" when there is rubber in all the joints?
There is so much 'compliance' with an Elan ( flimsy chassis, different
body manufacturers, day of the week, state of company finance and
rubber everywhere and WHY!)
Have fun
Roy
'65S2











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I agree with Roy. I ignored the rack shimming issue altogether and haven't
had any perceived ill effects since I got my Elan back on the road a year
ago. Skinny tires and the aforementioned compliance features probably help.
Tom Moore '68 S3

Lads,

Can we add a few more things to the list of "things to be ignored"

For instance, toe-in/toe out, fuel pressure, carburettor float level, cam timing, distributor timing, wheel bearing free play, brake disc run-out, tyre pressures, brake pedal free travel, headlamp alignment , spark plug gap, track rod end free play, door sag, ride height, contacts gap, exhaust clearance etc etc.

Why do we have to make life so difficult ?

Sean Murray
----- Original Message -----
From: tom moore
To: ***@***.***
Sent: Sunday, January 15, 2006 5:35 PM
Subject: Re: [LotusElan.net] Steering rack shims (re-shim)


I agree with Roy. I ignored the rack shimming issue altogether and haven't
had any perceived ill effects since I got my Elan back on the road a year
ago. Skinny tires and the aforementioned compliance features probably help.
Tom Moore '68 S3