Sonic Rear Toe Adjusters

[stevew]

As the rear toe adjusters cannot be moved once the upright is connected, how are they set to the correct length? Is it a matter of trial and error, installing the upright, checking the toe (upright parallel to the chassis?), disassemble the upright, adjust toe and repeat?

Or is there a better way? The build manual does not cover this as I assume they are a relatively new feature.

Steve

[kiwicanfly]

I guess you haven't got the "infinitely variable" adjusters, a stainless tube which slips into the arm which the connector then screws into.

Without them I guess its as you described.

[stevew]

No infinitely variable adjusters, one leg of the lower wishbone is threaded and the 'eye' screws into it. Adjustment is in half turn increments. It would be good to know of a way of getting it close to start with to save too many assemble-check-disassemble-adjust iterations.

Steve

[daydreamer]

the "non-infinite" adjusters do require disconnecting ( two bolts ) the lower wishbone from the upright to make an adjustment. You may also have to adjust the compression ring on the coil overs to make removing and re-fitting the wishbone to the upright easier and safer.

RE Toe adjustment on rear. I have between 1 degree and 2 degrees at the rear and this works best for me ( the most grip ).
I have tried 0 degrees and that was terrible. I think what happens is that under acceleration the suspension bushes and or wishbones move and the toe-in is reduced by about 1 degree to close to zero. When I started with zero toe in the back end became very tail happy.

[stevew]

Thanks for the response. Makes sense that the suspension will deform under acceleration. Did you have your suspension set up or did you manage to do it yourself?

[daydreamer]

I had the toe in for the front set by the local tyre shop, they measured the rear toe in for me and I took it from there.



When I first went to the tyre shop there was no manager just the lads, apart from checking clearances getting onto the ramps they were not phased. When I went back a couple of weeks later on a weekday the manager was all " we can't do that we have no settings in our charts, it won't fit , go away you look like a liability.... and more to that effect combined with arms waving in a style better suited to scaring pigeons.  A brief conversation about how it had fitted on his ramps two weeks earlier and that I had the required settings and he begrudgingly agreed to let the lads proceed.

Interestingly on the first visit I had no idea about what settings to use.  It turns out that we had about 17 degrees toe in at the front ( it had just been IVA'd and I think RTR did that to help the self centering ) ,  the lads suggested that in the absence of any recommendations perhaps 6 degrees would be a good starting point and they adjusted to it that.  I since settled on about 3 degrees toe in on the front ( from memory ).  This setup is good for every day driving.  If you have a pure track car than you might drop front toe in.

[Stiggy]

are we mixing degrees with mm here? Or maybe minutes?

I seem to remember we used to go for around 0.15 degrees (1-1.5 mm or about 9 minutes) toe in at the rear and zero on the front as braking induced toe out.

[Stiggy]

A car that maybe considered comparable is a Lotus Elise as that is mid rear engined. Presumably the balance is similar to Rocket/Sonic.
The Lotus recommended settings below concur with my above recommendation of front ZERO TOE and slight rear TOE IN.
For Atom there seems to be mass confusion depending who is asked the question. Obviously track or road tyres will play a part in personal pref's but as starting point the below is good.
One thing worth considering is the flexing of suspension under load.
EXAMPLE 1. When braking the wheels pull the suspension back causing toe out.
EXAMPLE 2. When torque is applied to the drive shafts it will cause the suspension to push in causing toe in.
POINT WORTH NOTING. The figures below show the rear ride height slightly higher than the front. This effects inertia and changes the roll axis by changing the roll centres, playing with these settings is very interesting, it may need very high changes to be noticed from the driving seat but imagine the effect on lift off over steer if the rear mass is raised significantly, worth playing around to find personal pref's but be careful, you may inadvertently dramatically change the handling.

   Front                                            Rear
Ride height 125 +/- 3mm           130 +/- 3mm
Camber -2.2°                           -2.4° to -2.7°
Toe (total) 0                             3mm total toe in

[daydreamer]

It would not be the first time I have been confused or mistaken.

The values I have given relate to a scale on the equipment used that was similar to that shown in lower part of the pic below.




I had taken that to be degrees but on reflection , prompted by your welcome intervention, it seems that the scale is something like 1/10th of a degree.   I had a look at manufacturer settings for typical cars and they concur with your sense of "scale".

That's the beauty of a forum,  we can all challenge confusion.

[daydreamer]

looking at stiggy's post just above mine it seems that I am running roughly 3mm toe in at the rear if I read the scale in the pic and that concurs with the details from Stiggy.

At the front, Stiggy suggests 0 degrees or mm and I have about 3 on that lower scale which looks like about 7mm on the upper scale.  This is less than half of what I started with and seems good to me.  I did consider going closer to zero or even zero but thought that for regular road use some toe in would be desirable.  

What this whole conversation is prompting me to do , is experiment a bit more.  I might try it at 0 and see how it feels.