Twincam Rear Toe

[Fotog]

While I'm thinking about it, I'll say:  information from Tim Engels, who seems to be very knowledgeable, is that at the rear, anyway, toe specified in the shop manual is measured at the outer diameter of the wheel rim, and is for one side, not both.

So, looking at the maximum toe of 1/4 in. specified for a TC, and measuring it on my 185/70-13 tire, about 23.2 in. diameter, with the stock Lotus steel wheel rim of 14.25in.  I would get:
               23.2/14.25 x .25in. x 2 (across both wheels), giving a max toe at the rear of .814 in., measured at the outer diameter of the tires.

One of the Engel references is here: https://groups.io/g/LotusEuropa/message/164808 .  The other, about one vs. both wheels, is elsewhere 

I'm not the expert!  If anyone has other ideas, feel free to chime in.

-V

[Clifton]

I used what Elise guys use as their weight and wheelbase are nearly the same.  S1 Elise is 1550 lbs.
 I just went out and measured and I am 5/32" total toe in on the rear using 24" long toe plates. My car is one hand, stupid steady over 100 mph. I was 120 last Sunday for a second, 80-90 the rest.  Too much toe in will make a car wander too.

https://wiki.seloc.org/a/Geo_Setups

https://trakkrats.com/technical-info There's a alignment pdf download

[Kendo]

Fotog, I would think toe at the rim would be less than toe measured at the tire edge, given the same angle. And .814 is more than .5. If you invert the tire/rim ration, it gives 0.307 total toe between wheels. I might be way off. I'm just trying to understand what you're all doing for when this comes up for me.

[JeffBatt]

1/8” per wheel is 1/4” total - think that would be in spec however it is supposed to be defined. 

So, I’m shooting for just under 1/2” total measured at the tires.

While I'm thinking about it, I'll say:  information from Tim Engels, who seems to be very knowledgeable, is that at the rear, anyway, toe specified in the shop manual is measured at the outer diameter of the wheel rim, and is for one side, not both.

So, looking at the maximum toe of 1/4 in. specified for a TC, and measuring it on my 185/70-13 tire, about 23.2 in. diameter, with the stock Lotus steel wheel rim of 14.25in.  I would get:
               23.2/14.25 x .25in. x 2 (across both wheels), giving a max toe at the rear of .814 in., measured at the outer diameter of the tires.

One of the Engel references is here: https://groups.io/g/LotusEuropa/message/164808 .  The other, about one vs. both wheels, is elsewhere 

I'm not the expert!  If anyone has other ideas, feel free to chime in.

-V

[TurboFource]

All these numbers sound like a lot ….why so much toe?

[JeffBatt]

The spec for a TC is 1/8” to 1/4” inch toe-in when measured at the edge of the wheel, so almost 2x that when measured out near the tire edge.

There is some uncertainty if the spec is per side, or total. It is a lot of toe, but that’s the spec, so…

[Fotog]

Turbo:  I don't know.  I'm not generally knowledgeable about this stuff.  I'm only trying to interpret what I read, either in the shop manual or on forums. 

Kendo:  you say: " I would think toe at the rim would be less than toe measured at the tire edge..."  That's correct.

So, if Lotus says maximum 1/4 in. when measuring the toe across the diameter of the wheel, well, of course it would be greater measured at the outer edges of the tire.  That's where I get 23.2 (tire diameter) / 14.25 (wheel diameter) x specification (1/4 in.)  Make sense? 

They say minimum is half that, so that would be ~.4 in. measured across both tires.  That agrees with Jeff's goal.

And Clifton:  That's interesting!  At this point I can't imagine going over 100, much less 125.  Crikey!  But useful to hear your experience.  Thanks.

I'm trusting what Tim Engel has said, but I think he's generally trustworthy.  I believe he spoke to someone at Lotus to confirm where and how the measurements are made.

-V

[jbcollier]

Tim also runs very little rear toe and actually a small amount of toe out at the front.  He likes the quick turn in.

I stick to the minimum front spec and middle of the spec in the rear.

[Clifton]

And Clifton:  That's interesting!  At this point I can't imagine going over 100, much less 125.  Crikey!  But useful to hear your experience.  Thanks.

I'm trusting what Tim Engel has said, but I think he's generally trustworthy.  I believe he spoke to someone at Lotus to confirm where and how the measurements are made.

-V

The speed was just to say my alignment settings are good and stable at speeds higher than most Europa's can or will ever even go. 100 is reached quick and done often and the car is autocrossed monthly. The 1/2" rear toe in Jeff wants to try may work if it's a neighborhood driven car but it is not safe or optimal and will murder the tires. 1/2" in will not be a fun drive over 60 mph.

3/16" toe in on the front is way too much. 1/16" total in to a light 1/16" out feels much better.

The workshop manual for an S2, yes TC is heavier but it's the same car.
http://lotus-europa.com/manuals/s2work/c/index.htm#4
javascript:ShowWin3('../tech/index.htm#J',800,600,20,20,'S1/S2%20Technical%20Specifications.')

Front Toe - in   3/16 in. (4.76 mm.) to 1/16 in. (1.6 mm.)
Rear  Toe - in   Zero to 3/16 in. (4.76 mmm.)

[JeffBatt]

The 1/2” I’m talking about, measured at the tires, would be equivalent to 1/4” when measured at the wheels, as per the spec. I agree it will wear tires faster than less toe, but not sure why it would be dangerous? It is, after all, the spec for the TC.

[SwiftDB4]

I agree with Clifton's recommendations. 1/2" total toe in is way too much. I also own a Superformance GT40 and have raced various formula cars over many years. All the cars had less than 1/4" total rear toe. I think your assumption that the toe spec is per wheel is wrong. "Too much rear toe in causes the car to feel light and unstable on corner entry" per Carroll Smith in his book 'Tune to Win'. Smith was a lead engineer in Shelby's GT40 team.

[JeffBatt]

A little under 1/2” total at the tire diameter is about the same as 1/4” total measured at the wheel diameter, that’s what I’m saying. By total I mean the sum of toe-in for both the wheels.

The spec is to measure at the wheel diameter. My toe plates are closer to the tire diameter, which is where I’m taking the measurement from.

[SwiftDB4]

My previous toe figures are all at the tire. Despite all our advice you seem to be determined to have 1/2" total toe so try it.