Plus 2 chassis tolerances

[m1dge]

It's time to address the chassis but before it goes off for blasting I thought I would take some measurements.

The back end appears to be ok, apart from the plate under the diff being a bit bowed, however the front end I'm a bit unsure of.

The distance between the two lower pickup pins is correct at 551 mm but the the upper ones measure 693 mm when the manual says it should be 701.6 mm. The towers still seem strong, both point outwards at the same angle (2° 05') and the diagonals across the tops of the front towers match. The manual also shows the angle the towers should lean back toward the rear. I'm assuming, as there are two values, that this is a range of between 2 1/2 and 3 1/2 degrees. My measurements are 2° 26' on the offside (UK) and 3° 08' on the nearside. This translates to a difference of 5mm when measuring the diagonals from front to rear.

Anyone have any thoughts on these values and if they're within tolerance or can give me a measurement between the tops of the front towers.

I've also attached a couple of pictures as there are two 'creases' where the towers are welded to the frame. I don't see this on pictures of other chassis and wondered if this was something to do with early models. They just seem too uniform not to be by design. Opinions please !

Thanks Andy

[berni29]

Hi

I have seen those creases before on standard chassis. Dimensionally it sounds OK to me. In my experience of both standard and Spyder chassis there can be a lot of variability.

If it is not a replacement chassis I would look very carefully for any cracks that you might not have noticed. They do crack. You do not want to be doing this job twice.

All the best

Berni

[m1dge]

Thanks Berni, good to know about the creases.

Couldn't see any cracks but I will be checking again between blasting and spraying. You're quite right I don't want to go through this pain again.

I was considering a new chassis and if the measurements were too far off then that's probably what I would do.

Andy

[berni29]

Hi

Blasting will reveal any cracks quite nicely. I have been there!

Best of luck

Berni

[alanr]

Yes I too can confirm the creases as shown in your photos are normal. My '71 +2S130 on its original chassis has exactly the same symetrical creases on both sides of the chassis the top flanges.

Alan.

[Lotus 50]

Assuming that the chassis tolerances are a bit loosey goosey, how does the wheel alignment get set correctly?

[snowyelan]

The pitch difference across the upper pins equates to approx 2.4degrees of added wheel camber total(inclusive of both sides). I'd check the diagonal distance between the lower left/upper right pins and vice versa to see if the 2.4 degrees is evenly split. Below is what I believe it should be. Please check the dimensions, specifically the 208.3, I used against your manual. I pulled them from the internet as I don't have a plus2 manual.

[m1dge]

Snowy, thanks for going to the effort of a diagram.

I have checked the diagonals as you suggested and the 208.3 measurement.

The good news is the diagonals match at 656mm so either the towers have both moved by the same amount (probably unlikely) or that's how it came. Also the 208.3 measurement is 212 which I think gives a little less negative camber then the 2.4 total added.

As it's all stripped down I think I'll just have to take the risk that the final camber at the wheels (with the appropriate weighting in the car and ride height etc.) is close enough.

Cheers, Andy

[snowyelan]

Hi Andy,

Glad the diagram helped. I'm curious, does the +2 manual show 212mm? If so, the additional height adds slightly more camber.

[m1dge]

The manual says it should be 208.3 but I'm getting a measurement of 212.

I assumed the 2.4 degrees you mentioned would be adding negative camber and by adding more height this would result in slightly less negative camber although I'm not sure I've got my head around it all.

Andy

[snowyelan]

Hi Andy,

Below are the dims, zoomed in on one side. Blue underline is based off the +2 manual dims you provided and red underline are your measurements. The one in the red box is out by a mm, which is pretty good as I assume you're using a tape measure for the 4 dimensions you provided.
1.36 degrees per side is pretty good in my opinion.

[m1dge]

That's great to hear.

Off to the blasters !! Thanks Snowy

Andy