Twincam Rear Toe

[jbcollier]

On the first production S1s, the bushings were bolted with the flange on the outside and bulk of the bushing facing inwards.  This led to a situation where the rear wheels were toed out with no adjustment left.  The factory did a production change and issued a bulletin to fit the bushing flange on the inside of the chassis to provide enough adjustment (still with bulk of bushing to the inside).  I believe this is true for the TC/S as well.

[Fotog]

Jeff-  how much toe (in or out) do you have now?... and can you recommend a specific supplier for the Esprit shims?  I may buy them, but I'm reluctant to buy a bunch of them without having some idea what I really need.

-Vince

[JeffBatt]

This is how I have the bushings attached right now.

Vince - looks like sjsportscars has them, found them cheaper but in 5mm thickness here, looks like they also have 2mm:

https://www.pnmparts.co.uk/lotus-shim-4052

My plan is to use 10mm of Esprit spacers on each side and then fine tune with a few washers. I could be more simple if I reversed the bushings but that might make them stick too far out.

[Fotog]

Thanks;... but what did you measure for toe before you start shimming?

-V

[GavinT]

Is the body removed, Jeff?

If so, check to make sure you can get the long bolt out with the body in place.
On the S2, the bolt head needs to be on the inside of the chassis - don't know if this applies to the TCS so hopefully, someone will chime in on that.

[BDA]

 

I'm almost positive it also pertains to the TC. In any case, it's better to put the bolt in from inside the frame if you don't know.

[JeffBatt]

Yep, the body is off but I will flip the bolts around, there will be no way to easily get them out like this with the body in place.

It isn’t actually shimmed yet, but I aligned it with toe plates and a string referenced to the center of the backbone to figure out about how many shims I’d need. It’s just sitting loose.

[JeffBatt]

With no shims, there is a ton of toe in, think it was around 1” total measured at the tires but didn’t have my string in place yet to know more exact.

Was shocked it was that much.

Thanks;... but what did you measure for toe before you start shimming?

-V

[GavinT]

It isn’t actually shimmed yet, but I aligned it with toe plates and a string referenced to the center of the backbone to figure out about how many shims I’d need. It’s just sitting loose.

What's a "toe plate" ? . . a plate attached to the hub face to measure toe, presumably?

JB mentioned checking the thrust angle and this is probably an ideal time to do it while you can see the chassis centreline and are playing around with shims & string etc.
I've often wondered how precise this was when they came out of the factory.

[Fotog]

Toe measurement plate:
I'm new with this, but it seems quite good.  I believe that most of them just lean against the tire.  I like that these rest against the wheel, using standoffs; seems like better precision to the measurements.
-Vince

[jbcollier]

I would wait until the body is on.  That will lower the suspension and alter things considerably.

[EuropaTC]

Toe measurement plate:
I'm new with this, but it seems quite good.  I believe that most of them just lean against the tire.  I like that these rest against the wheel, using standoffs; seems like better precision to the measurements.
-Vince

The problem with that sort of device is that it's hard to get a true centreline and as JB posted, it's easy to get the thrust angle wrong because you're only measuring overall toe relative to the wheels, not centreline. Having said that, I often use a similar device for front toe because it's easy to set up & very quick to do.

For DIY alignment my personal preference is for the basic string box method. Time consuming to set up but very low tech and you can even do the maths to allow for some error in aligning the "box" with the centreline. That gives a good indication of toe per wheel which is what you need at the rear otherwise the car's never going to feel right.

Shims - I also use the Esprit style shims and also needed far more than I expected to get within spec, I can't recall off hand but something like 8mm comes to mind and that was why I moved from washers to the Esprit style. If you need more than the odd one or two (like I did) then you can easily make them up from Aluminium plate with thinner ones to get the final setting if you can't get the right plate thickness.

Brian

[JeffBatt]

Aligning the string to the center of the chassis is (obviously) much easier with the body off.

I’ve got Avo coilovers, so I will do this alignment with them lowered all the way down and then raise them slightly before putting the body back on. I imagine it will end up pretty close.

Anyway, my goal with the Esprit spacers is to just keep the washers to a reasonable number of about 5 or less per side.

[JeffBatt]

Nice toe plate!

I truly think you can get as good, or better, an alignment than you would at most shops that use lasers just by taking your time and being diligent with your measurements.

Toe measurement plate:
I'm new with this, but it seems quite good.  I believe that most of them just lean against the tire.  I like that these rest against the wheel, using standoffs; seems like better precision to the measurements.
-Vince

[Fotog]

The problem with that sort of device is that it's hard to get a true centreline and as JB posted, it's easy to get the thrust angle wrong because you're only measuring overall toe relative to the wheels, not centreline. Having said that, I often use a similar device for front toe because it's easy to set up & very quick to do.
Brian

Understood, Brian.
I got the toe plates most specifically because I was doing front suspension work and wanted to check alignment there after replacing the tie rod ends.  I know that using them I won't get a full reading on the condition of the rear, but figured it would be a good idea to get a baseline reading on the rear toe anyway, with thrust angle to be determined later.

I want to update the brakes (no boosters present) with a Spitfire master cylinder, and while I'm at it figured I should replace the 40 or 50 year old rear brake hoses.  So that leads to also replacing the trailing arm bushes (maybe original) while I'm working there... Which leads to dealing with rear alignment.  So as you see, the plot thickens!

I appreciate the info from Brian and Jeff to give me an idea about what I might need for shims.  I'll try to get a rough measure of how far the trailing arms are set from the frame presently and work from there I think.  I'd rather not bite off all this at once (It's a lot to chew), but maybe it's the right way.

It was interesting and revealing, doing the measuring / adjusting / driving / re-adjusting on the front.  Initially I had way too much toe.  I was surprised to find that it made handling very squirrely, but it was about about 1/2 in., so a lot!

-Vince