Wheel Alignment issues ?

[EuropaTC]

Wheel alignment, or to be exact, rear wheel alignment.  I'm struggling with this one at the moment and thought I'd start a topic to get a few comments from you guys. I don't mind if you say I'm doing it wrong, I'm being crazy or simply worrying about nothing,  all comments are welcome.

Ok, some background.  I normally adjust my front tracking either from measuring the front & rear of the tyres or by using a device called the "Gunsons Trackmaster", which is basically a movable platform that you roll the car over and it tells you how many degrees you have of toe-in or out. I've used this for front & rear but the problem I'm finding is getting accurate repeatable results so I resorted to the string square and measuring method.  I have the car set up as in the first photo, strings taught and the front & rear white bars are identical length and set to the same height.

I've taken measurements using a digital gauge as shown in the second photo and would guess I'm reasonably consistant. My first measurements are to centralise the string square around the car by getting equal dimensions across the front & rear axles taken from the wheel centres because this is a TC with different front & rear tracks so front & rear measurements are slightly different, but equal across the car.

I then measure front & rear from each wheel rim and in theory that should give the toe-in or out against the centre line of the car.  In practice I never get the steering wheel exactly centered but the total front toe-in has been repeatable, so I'm not bothered by that. (should I be ? )

What's bugging me is the amount of shims I'm having to put in to get the 1.5 to 3.0 mm toe-in on an individual wheel (makes 3mm - 6mm total toe-in). On one side I have 8mm of shims, on the other I've got 12mm, which seems a heck of a lot to me. The chassis is a Lotus replacement one, the rear arms are also replacements and I can't honestly see any damage to either component, so this discrepancy in shimming is bugging me. I honestly expected to find both sides the same to within 1-2 mm and I didn't really expect to use 12mm on one side.

So I guess the question is, has anyone else found the same thing on their car ?

How do you racers go on setting up your alignments and secondly, do you work to the 3-6mm range in the manual ?  As I said at the start, all comments welcome - TIA.

Brian

[BDA]

First, Very nice looking car! The wheels are really nice!

I assume you're using the stock suspension in which case I don't see anything wrong with your method except that toe measured in linear units is the difference between the track taken at the center line of the tires (see here: http://robrobinette.com/ConvertToeDegreesToInches.htm). I would also not be concerned with your steering wheel being exactly straight since there is no ackermann designed in the steering.

As for the side to side difference in the shim stack needed to set the rear toe, I'm not completely surprised given my experience with Lotus' precision in Europas, but I can see where a 4 mm difference in the shim stack is somewhat alarming. Part of it could be the sum of manufacturing tolerances in the frame, differences in the bushing in the frame, and the bushing (or tube) in the radius arm. Four millimeters is about 0.16" or a bit more than 1/8". I don't think that is something to get too concerned about. If your car isn't tracking straight (i.e. crabbing), you should look into it further.

[EuropaTC]

Hi BDA,

Thanks for the reply and that link. I've been scratching my head trying to remember things about triangles to convert degrees to measurements and that link hits the spot.

I've never been sure where the toe is measured from, the wheel rim or the tyre tread so the web site is useful for that as well.  I thought it should be the tread because that's the road contact but equally I've seen references to measuring from the wheel rim.   In my case (and confusion) I've done both just to see what the differences are and so far I've been working on the rims because that's the easiest to get repeatable results, but setting to the bottom end of the spec at 1.5mm/wheel. Tyre tread figures are slightly higher, as you'd expect, but within spec.

It's stock front suspension arms but 250lb springs. Rear is stock trailing arm & driveshaft but adjustable lower link. The camber is set to 0.5deg because I've been told modern rubber (205/50) prefers to lie flat on the road, hence the lower end of the Lotus spec. Rear springs are 140lb and all are on adjustable platforms so the car is sitting slightly lower than normal.

Because of the recent clutch drama I'm only now getting to drive the new suspension and that's why I've been checking the alignments. It's gone from being nervous on bumpy roads to feeling quite stable now, but I guess it's the amount of shims I've used that's bugging me. I pulled out some thick rusty washers but not 1/2" (12mm) worth of them. I'm even wondering if there's a difference between S2 & TC trailing arm geometry and if the car has the wrong ones ?

Brian

[BDA]

If you had a fully adjustable rear suspension, you might have issues with the track being different from one side to the other, but since you still seem to have the stock half shafts, your track will be contained by the camber you set (if you know what I mean) and that would not be an issue. I come back to the fact that 4 mm is a small difference and that I wouldn't worry about it.

You're sprung pretty stiffly. I tried 250 lb front springs and found the ride very twitchy. I don't really remember what springs I have now (I think they are about 10% stiffer but I'm not going to take the front suspension apart just to find out!) but it seems a lot better now. It could have been that I had alignment issues that I wasn't aware of when I had the 250 lb springs. Since your car is stable, I'd say that your alignment is at least close. If you have instability in a straight line at high speeds, it is likely too little toe-in in the rear or maybe even the uneven toe it seems you are concerned about. Somewhere long ago I heard from somebody who I then took to be authoritative that Europas came off the line with excessive toe-in. I don't know if that's actually true but it would explain the horrid rear tire wear and it would also be safer.

I don't think the trailing arm geometry has changed between the S2 and the TC but I only think that because the S1/S2 workshop manual gives dimensions for the radius arms and the TC supplement doesn't. They are different part numbers, however. Your half shafts should basically be at 90 degrees to the center line of the car but then small differences would be difficult to measure. In the end, I think if you can align the car (and you have the same pieces on both sides) you're in good shape. If you are REALLY concerned, you can get the center line of the car by dropping a plumb bob from equivalent parts on either side of the front and rear of the frame to the floor of the garage and then do the same from the front and rear suspension. Then you can see if one side is wider than the other or if there are other 'out of square' issues. It might be an interesting exercise, but also a lot of work.

[HealeyBN7]

Brian,

Sounds like you are headed in the right direction.  As BDA stated, don't worry about the shims.  I have an uneven stack up on my car as well.

I would like to offer a suggestion seeing that you are stringing from jackstands.   I used to do it this way as well, but found that I could not pull the string tight enough and just when I thought it was perfect,  I would round the car and kick the jack.

I now have two pairs of J hooks.  One low on the front wall and another near the garage door.   I slip a 1/2 tube onto the hooks (conduit works great) and string from the secure tubing.  I also found that mason's line has just the right consistency to be pulled tight and easy to measure from.  I was impressed that you were using a caliper. I use a steel ruler, but I might have to upgrade to the caliper method!

Dean

[EuropaTC]

(part quote)
I could not pull the string tight enough and just when I thought it was perfect,  I would round the car and kick the jack

    I can identify with that !  I like the idea of a fixed hook, I can see how that will work and must make the job more reliable. I ended up putting every hammer I had into the axle stand frames to keep them steady once I'd got the string tight. A fixed line is a much better idea.

The digital caliper came about after trying a ruler and struggling with the mm increments. The depth gauge part of these things works a treat, repeatable every time and makes the job easy.

Also, thanks for the comment about also having uneven spacing across the car. I'm slowly coming to terms with it. It's 20/20 hindsight but boy do I wish now that I'd kept the old washers rather than just throwing them away and thinking "I'll set it up from scratch with new ones".

BDA,

I was hesitant at 250lb but because of the operating angle it comes out at around a 1.8 frequency which is the same as I have on the Elan.  The only uncomfortable moment from the front of the car has been going too fast over a railway crossing, which did shake my eyeballs a touch. (slower next time) 

The rear is also around 1.8 and felt ok on smooth road but twitchy on a particularly bumpy road we have here, and that's what set me looking harder at the alignment. Plus of course I've had the gearbox out and engine off it's mounts, so after putting it all back I suppose it should be re-checked anyway.

Brian

[BDA]

I tried 250# springs in the front because someone advised me to. They may well be the ticket and my problems where elsewhere but I'm happy with the springs I have now (whatever they are!). I have 15" wheels and between the two, my ride is firm enough for me.

If you have the original suspension (even with adjustable lower links, you shouldn't NEED to re-align the rear after taking the tranny or engine out, but it's never a bad idea.