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Lars S
Samba Member
Joined: October 04, 2007
Posts: 783
Location: Sweden
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 Posted: Sat May 14, 2016 3:37 am Post subject: Control arm and toe in |
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I have measured the front toe in to 3.0mm (half tank), the spec says 0.6 to 4.2mm.
Since my 412 has some small wandering on plain highway how much toe in could I go up to? (I will center the control arm bushing in its holder not until next winter). Im running 185/65 on 5 1/2" Sprintstars.
I know toe in should be checked with full tank, in what direction would that affect it?
Lars S
_________________
Porsche 914 -72, Bahia Red daily driver 
VW411 2-d -70, White, sold 
VW412 4-d, -73, Gold Metallic, daily driver
Suzuki T500, -69, Candy Gold, sold
Suzuki K50, -77, Black, daily driver
BMW R69S -69, White, sold
Husqvarna 118cc, -47, Black, Sold |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21513
Location: Oklahoma City
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| Posted: Sat May 14, 2016 7:44 am Post subject: Re: Control arm and toe in |
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| Lars S wrote: |
I have measured the front toe in to 3.0mm (half tank), the spec says 0.6 to 4.2mm.
Since my 412 has some small wandering on plain highway how much toe in could I go up to? (I will center the control arm bushing in its holder not until next winter). Im running 185/65 on 5 1/2" Sprintstars.
I know toe in should be checked with full tank, in what direction would that affect it?
Lars S |
I will have to dig in my book....but from memory.....additional trunk load increases compression on struts.....which increases camber slightly ........and I believe it increases TOE OUT.....or decreases toe in.....because of the way the pivot points are angled on the control arms.
Also......4.6mm is not that huge toe-in. 3mm is just a little under 1/8"....4.6 being a little over and probably the upper limit.
The "shiftiness" you are finding......can also happen if your toe-in is excessive. ....and can definatley be caused if the rubber in the control arm bushings is worn and stretchy enough that the control arm is shift forward or backward while driving..
A good home experiment to find out .....this is how I found out......is to install temporary shims to center the control arms in the yoke.
You can do this by taking steel wire like you use for safety wire and widing it around the exposed end of the center bushing tube in the gap on each side of the control and bushing to fill the gap. Grease the wire.
It works well but may not last more that 5k miles. Drive that and see if it improves. If it does not actually improve handling....it will for sure change it as it centers the control arm and slightly changes toe in.
Then with a marker.....mark the outer tie rod end position.....make sure they are level and not twisted in their socket....and then lengthen both ends very slightly....adding more toe in. You dont want to add more than about 1/16" total. Maybe 1/4 turn each. Drive that again and see. If it improves....you needed more toe in. If it gets worse.....you needed less.
Also check carefully to see if your tires are wearing in a particular manner. Ray |
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Lars S
Samba Member
Joined: October 04, 2007
Posts: 783
Location: Sweden
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| Posted: Sun May 15, 2016 9:37 am Post subject: Re: Control arm and toe in |
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Just for curiosity I wanted to know how full tank affects the toe in so i drove and filled it up from 1/4 (which it was at my first toe in check) to full volume.
The new measutement gave the same result, maybe 1mm more toe in (4mm instead of 3mm).
The rims seemed to be about 2-3mm more apart then at 1/4-tank but they were more apart both at the rear and at the front so it did not affect the toe in....strange since if the rims goes apart the toe-in should be affected as this would pull in the steering arms...
/Lars s
_________________
Porsche 914 -72, Bahia Red daily driver
VW411 2-d -70, White, sold
VW412 4-d, -73, Gold Metallic, daily driver
Suzuki T500, -69, Candy Gold, sold
Suzuki K50, -77, Black, daily driver
BMW R69S -69, White, sold
Husqvarna 118cc, -47, Black, Sold |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21513
Location: Oklahoma City
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| Posted: Sun May 15, 2016 9:59 am Post subject: Re: Control arm and toe in |
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| Lars S wrote: |
Just for curiosity I wanted to know how full tank affects the toe in so i drove and filled it up from 1/4 (which it was at my first toe in check) to full volume.
The new measutement gave the same result, maybe 1mm more toe in (4mm instead of 3mm).
The rims seemed to be about 2-3mm more apart then at 1/4-tank but they were more apart both at the rear and at the front so it did not affect the toe in....strange since if the rims goes apart the toe-in should be affected as this would pull in the steering arms...
/Lars s |
What you are seeing I am quite sure...is actually more camber from the weight and pivot angle of the control arms. Camber and toe-in are connected at the hip....because of control arm pivot angle. Its some of....a slight amount....of the same effect you get on the rear of a swing axle vehicle.
As the weight in the tank and trunk increases and the chassis crouches down lower....it pivots about the control arm bushing axis. The outer ends at the ball joint pivot to try and keep the axle level...but there is some change.
This affects toe in....while stationary on an alignment rack only a small amount.
But....this small amount is multiplied once the car is in motion and forward friction is forcing the tires outward/rearward.
Also check the condition of your radius arm donuts. If there is slack or if they are falling out of plane because of worn centering rings in between them...this affects everything. Ray |
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