Rear suspension wheel toe in/out

Post by **Heuer** » Thu Oct 31, 2013 3:02 pm

Just had INR check the suspension on my FHC. The front was out by 4.3mm which caused some rather wayward behaviour at speed and it is now hugely improved. They did comment about the l/h rear wheel toe:

Not sure there is anything I can do to change it though. Any thoughts or should I just leave it alone?

christopher storey · Post by **christopher storey** » Thu Oct 31, 2013 7:55 pm

David : a few ( rather untutored ) thoughts : -

1.Is the LH wheel running true when you spin it ( I ask this because the alignment man at my local tyre garage refuses to do alignment on wires unless you really press him because he says that the tolerance on wires makes it virtually impossible to know whether it is the suspension or the wheel at fault , and you can get widely differing results with the wheels in different positions of their rotation )

2. Are the trailing arm bushes worn and thus perhaps allowing the shaft and hub to move backwards ?

ditto the main suspension mounting rubbers ?

3. In any event , the degree of fore/aft compliance in the suspension mountings is considerable and I would not mind betting that you would get widely differing toe in/out results on the rear between acceleration and braking . The compliance can be altered ( with difficulty ) by mounting the large front rubbers with the holes at right angles to the normal orientation . Offhand I cannot remember which is the normal orientation

4.Is there any abnormal wear pattern on ( in particular ) the LH tyre

Post by **Heuer** » Thu Oct 31, 2013 9:25 pm

Thanks for your thoughts Christopher.

INR are used to wire wheels - their workshops are an Aladdin's cave of classic race cars and their mechanics are really good. Best I have come across in fact because they only work to race car standards not road car/ trailer queen stuff.

There does not appear to be any wear in the bushes as they have all been renewed. I know I can rotate the trailing arm bushes by 90 degree's and have done so on my OTS but I drive the FHC 'sensibly'. As everything on the car is new I can't tell if there is abnormal tyre wear. INR said to drive the car and see how it feels, which is fantastic actually. They put it on the rolling road and reset the timing/carbs and it is the way they want it - I have to agree because it makes you realise what a fantastic car an original E-Type is/was. I used it for commuting today, something I would reluctantly contemplate with my goosed OTS, and it was docile yet aggressive when required.

Your observations on the IRS suspension mountings are something I had not considered because the whole thing can twist with applied torque so measurements will vary to some extent. I have studied the Optiflex output results but I can't derive anything more from them, hence the question.

PeterCrespin · Post by **PeterCrespin** » Thu Oct 31, 2013 9:45 pm

The rear toe cannot realistically be adjusted but the figures suggest a misaligned cage. Try to measure the wheelbase as accurately as you can from spinner centre to centre and my bet is you'll find it slightly shorter on the left side. There are ways of slackening everything off and 'persuading' the cage to sit straighter, but first see what the wheelbase variance is.

Pete

Post by **Heuer** » Thu Oct 31, 2013 11:18 pm

Thanks Pete - I will do some measurements to morrow.

rfs1957 · Post by **rfs1957** » Thu Dec 05, 2013 8:11 am

David,
Wasn't there an exchange once with someone who had a firm that used the blue-tipped-universal-adjusting-tool to tweak the rear link lengths, and would there be a vein to mine with an eccentric adjustment facility on those front fixing-bolts in the middle of the rubbers ? Please be gentle with me if these are daft questions, never measured (or dared measure) anything on mine yet !

Rory

christopher storey · Post by **christopher storey** » Thu Dec 05, 2013 9:56 am

The front fixing bolts only have a vertical function - to stop the metalastik bush popping off the cone . The actual fore/aft location is done by the cone and the corresponding metal interior of the bush . Thus eccentricity of the bolt, whilst a nice idea, would not work in this case

Post by **Heuer** » Thu Dec 05, 2013 1:09 pm

Rory

Can't recall such a post on an adjusting tool. I don't think many people have ever bothered with a full suspension alignment check on their E-Type because the rear can only be adjusted for camber. When INR did mine they said the rear toe could be changed but it meant messing about with washers and they really did not feel it was worth it unless I was going racing. Their view was "drive it and see what you think" after the front was adjusted. Although the l/h side of mine is greater than the r/h the total toe is within limits and the IRS will compensate. Having now driven the car it seems perfect to me as it was the front alignment that was making it a pain to drive.

rfs1957 · Post by **rfs1957** » Thu Dec 05, 2013 3:01 pm

By "blue-tipped-universal-adjusting-tool" I meant oxy-acetylene ........... they were heating them up in the middle and probably doing something clever with cold-water. Sounded voodoo but he swore you could watch the change and freeze it where you wanted, sounds hard to believe and I don't understand the metallurgy. Maybe it was 1st April after all.

Moeregaard · Post by **Moeregaard** » Thu Dec 05, 2013 4:23 pm

I'm with Peter on this one. It sounds to me like the IRS assembly may not be sitting properly. Any sort of toe problem back there would most likely be attributable to worn lower wishbone links, and you'd hear and feel those. Worn rubber bits won't affect toe, but will allow excessive movement of the entire mess. The correct (factory) orientation of the large trailing-arm bushes has the holes sitting fore and aft. I have heard that mounting them 90-degees off will effectively reduce any rear-end steering tendencies.

"Blue-tipped universal adjusting tool!" I can add that to "Gas Axe" and "Hot Wrench!"

PeterCrespin · Post by **PeterCrespin** » Fri Dec 06, 2013 12:05 am

rfs1957 wrote:By "blue-tipped-universal-adjusting-tool" I meant oxy-acetylene ........... they were heating them up in the middle and probably doing something clever with cold-water. Sounded voodoo but he swore you could watch the change and freeze it where you wanted, sounds hard to believe and I don't understand the metallurgy. Maybe it was 1st April after all.

A truly skilled fabricator can move metal around with heat cycles if the metal is suitable. Don't know about the cage, but I've heard of heat and quench being done on lower wishbones. It could be made to work on the cage but not in-situ because the toe-in would be held rigid by the unchanged diff and inner pivots, as nothing outboard of them has any effect on toe. You'd need to do your cage tinkering (probably between the two pivot holes at the front to increase toe-in) and then re-shim the pivot blocks.

Using a gas axe on the front and rear of the middle part of the major wishbone tube could be expected to adjust things fractionally, and we are discussing only tiny dimensional changes.

Pete

abowie · Post by **abowie** » Fri Dec 06, 2013 9:12 am

PeterCrespin wrote: It could be made to work on the cage but not in-situ because the toe-in would be held rigid by the unchanged diff and inner pivots

Although toe in of one rear wheel cannot be adjusted in respect to the other, the IRS can by virtue of its flexible mounts be rotated relative to the body by changing the length of the trailing arms, which I think is what Rory is referring to.

Looking at the original measurements, one wheel is significantly toed out (or in; it's not clear to me) (3.7)while the other is relatively straight (0.4). If some gas axe action was to shorten the appropriate trailing arm is it not possible that the IRS would rotate slightly, making the toe in equal?

paulsco · Post by **paulsco** » Fri Dec 06, 2013 10:11 am

David,

If your car has been restored, it could be that one floor side is slightly further back than the other and so is the radius arm mount.

Paul

Moeregaard · Post by **Moeregaard** » Fri Dec 06, 2013 4:02 pm

Good point, Paul. A car with this issue would tend to run down the road "crabbed" to compensate for the misalignment.

PeterCrespin · Post by **PeterCrespin** » Sat Dec 07, 2013 2:18 am

abowie wrote:Although toe in of one rear wheel cannot be adjusted in respect to the other, the IRS can by virtue of its flexible mounts be rotated relative to the body.

That's what I said about David's car in October Andrew. However, I don't recall reading his wheelbase measurements, which is the dead easy way to check out this option.

As regards aligning the cage by cutting/shutting the radius arms, I don't think two wrongs make a right. God forbid someone unknowingly swaps them during a future rebuild and ends up with a magnified problem. Before deciding on the various remedial options, I think it's mandatory to identify the nature of the problem.

johnney · Post by **johnney** » Sat Dec 07, 2013 7:06 am

Moeregaard wrote: The correct (factory) orientation of the large trailing-arm bushes has the holes sitting fore and aft. I have heard that mounting them 90-degees off will effectively reduce any rear-end steering tendencies.

Actually this will reduce fore aft compliance and increase rear wheel steering.

If you have toe in or out on both rear wheels then it cannot be caused by the front radius arms mounting points. I would Jack up, remove the rear wheels, fasten a straight edge to each hub face then measure the distance between them front and back at a suitable distance from the hubs and compare. Repeat with the radius arms disconnected from the body. If there is a difference with the radius arms removed then its most likely problem 1 below. In any event the problem is most likely within the rear suspension unit and probably due to one of the following reasons,

1) The lower links inner fulcrums are worn allowing the radius arms to pull them forward relative to the diff/cage.
2) The lower links are bent, you can check this on the car by measuring the centre to centre distance between the inner and out lower link fulcrum shaft centres. They should be the same front and back.
3) When the suspension was rebuilt the lower link inner fulcrum mounting bracket(C.20481) was not shimmed correctly to the diff case.

PeterCrespin · Post by **PeterCrespin** » Sat Dec 07, 2013 2:19 pm

Agree with you on everything but the last point. The fulcrum brackets being badly shimmed would just make the pivot hard or impossible to install. The geometry is set by the cage pivots and fulcrums shimmed to suit, not vice versa.

Pete

johnney · Post by **johnney** » Sat Dec 07, 2013 3:52 pm

I agree also if the factory method of assembly is followed but I helped a friend strip and reassemble his rear suspension unit. If I remember correctly as its more than 30 years ago, one or both of the installed inner fulcrum shafts were found to have had a lead ground on one end presumably to ease installation. As always if its possible to assemble it wrong then someone will manage it.

Moeregaard · Post by **Moeregaard** » Sat Dec 07, 2013 5:37 pm

Quote: Actually this will reduce fore aft compliance and increase rear wheel steering.

After another cup of coffee and subsequent clarity of thought, I have to agree with this

JEP41 · Post by **JEP41** » Sun Dec 08, 2013 10:50 am

Hi All,

With regard to the rear wheel toe-in, I did mention some time ago on the forum I was on a track day at Goodwood and my lightweight copy was behaving very strangely under hard acceleration. the car was trying to go in a different direction to where I was pointing my front wheels. Chris Keith Lucas (ex Lynx) now CKL developments was at the track that day and I asked him to try my car, he did several laps and concluded "rear wheel steering to be the problem and to bring the car to their works near Battle and they would sort the problem. Expecting major mechanical work and a long day with a possible overnight I arrived early. Two hours later I was on the way back to Norfolk. The car was set level on the 4 post ramp and optical alignment gear attached to all 4 wheels The car was raised up and a Technician fired up the Oxy Acetylene and started to heat one of the rear lower wishbones Chris informed me he prefers 2-3 degrees toe-in but has had customers who prefer 5 degree. We settled on 3 deg from memory. As the heat was applied you could see the toe in changing on the gauge. The tech left that side to cool and repeated the process on the opposite side. Again left to cool naturally. As the wishbone cooled the toe-in changed slightly and the process was repeated until perfect. This toe-in adjustment has transformed my cars handling on the track and on the road

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