True or just a Story ?

[Stueeee]

My Renault 4 was so badly made there was about 100mm difference between the left and right hand wheelbases.

ISTR that they were made that way; the rear torsion bars were across the 'chassis' one behind the other. One job ( I always got the good ones) I did involved welding the rear corner of a R4 chassis where it had snapped when the car mounted a kerb at walking pace

 

[Smallfry]

ISTR that they were made that way; the rear torsion bars were across the 'chassis' one behind the other. One job ( I always got the good ones) I did involved welding the rear corner of a R4 chassis where it had snapped when the car mounted a kerb at walking pace

That is correct. Beat me to it. There are a couple of other cars built this way too, but I cannot remember what they are.

 

[Dilkris]

do you mean transaxle is Renault 16 not 6 is same as reno 4 but bigger body

Sorry my typo - Renault 16

 

[Dilkris]

All of this needs to be done with the vehicle sat at ride height, normally means swapping out the coil overs for spacer bars to mimic ride height. Also quite hard to measure toe at hub centre height,might be better to make some drop plates so you can pass a tape under the car or buy a cheap set of steering gauges.

Bob

I know...... but - as I said in one of my earlier posts quote: "I am at this stage with my rebuild and I want to get the alignment approximately dialed in - (For those that understand these cars, there is some geometry regarding the rear radius arms that I am concerned about.)

 

[Dilkris]

Cheap easy straight edge would be an aluminium extrusion, plasterers straight edge, something like that. Not truly straight but "good enough" for a lot of projects and a lot more robust than a glass tube I suspect.

String method for wheel alignment, if done carefully, can be very accurate if somewhat of a faff.

I am beginning to agree with you

 

[optima21]

I think he's seen the light now and found that light can bend round corners

 

[Keithmac]

I've always String Aligned my cars but appreciate there is more than one way to skin a cat.

My lad does alignments at work now so might take a car down and see how close it is.

 

[Dilkris]

I'd just strip the tyres off of the rims and fit them, toe-in angle is measured at/on the wheel rims, having a 3 or 6 foot long bar or straight edge will throw things out, provided the rims are serviceable (and not bent) use what the normal toe-in measuring system uses as data points.... I take it you have a set of wheels?

Yes - I have the rims - with new tires fitted. Toe in can be equated to an angle "yes"? (As well as a dimension generated from the wheel rims).
Assuming this to be correct I can work from angles generated from the front discs and rear drums no? Front and rear wheel bearings plus drums and discs are new - so I would prefer to not include the wheel rims, which look good but are 51 years old..... and I'm sure will have been up some kerbs and/or down some potholes in their lifetime.

 

[voipio]

Spinning the vehicle-mounted wheel will allow you see how much runout there is. 0.1 degree, or 6 minutes, (roughly 1/6th turn of the trackrod) equates to around 1mm difference at 18 inches diameter.

 

[Dilkris]

Spinning the vehicle-mounted wheel will allow you see how much runout there is. 0.1 degree, or 6 minutes, (roughly 1/6th turn of the trackrod) equates to around 1mm difference at 18 inches diameter.

I am amused that you use both metric and imperial units in the above - but its all good - its just trigonometry once converted to a common unit of measure.
So.... your 1/6th of a turn of the track rod results in 1mm movement on a 18" rim which as an angle equates to 0.25 degrees. I obviously could not hope to accurately measure 1mm with string - BUT - if I attached 5' tubes (say) to the front discs (say) it means that a 0.25 degree movement on toe in or tow out is created by 3.33mm of movement at the end of my 5' tube/stick/or whatever - now that I can measure. Are you with me?

 

[zzr1200]

With a pivot point ie: "The King Pin" if you have a toe-in spec of 1/16th of an inch on a 12" diameter wheel (OEM Spec?), if you then use a straight edge with a length of 5ft (from hub centre) and you again use the OEM toe-in spec. You will have altered the toe-in spec for the vehicle, being as you have moved the manufacturers measured data point by 4ft 6ins from normal data point from the king pin.

This why you should use the standard size wheel for the vehicle....imo.

 

[Dilkris]

No - think similar triangles.....
if your wheel is 12" diameter - that's 6" from the kingpin - and you are wanting a toe in spec of 1/16" or 0.063"
To achieve this, I'm going to use a 5 foot something mounted mid point on the disc/drum so my "extension" and the end or measuring point would be 30" from the center line of the king pin.
To achieve your 1/16" toe in - the end of my 30" something would have to move 0.31"
As a formulae, describing the triangles it would look like this: 0.063/6 = x/30. Therefore x = 0.31. (All units in inches)

 

[voipio]

I am amused that you use both metric and imperial units in the above - but its all good - its just trigonometry once converted to a common unit of measure.
So.... your 1/6th of a turn of the track rod results in 1mm movement on a 18" rim which as an angle equates to 0.25 degrees. I obviously could not hope to accurately measure 1mm with string - BUT - if I attached 5' tubes (say) to the front discs (say) it means that a 0.25 degree movement on toe in or tow out is created by 3.33mm of movement at the end of my 5' tube/stick/or whatever - now that I can measure. Are you with me?

Mixing units was simply because we still largely refer to vehicle wheel sizes in inches ;-)

The 1mm movement given, as an example, refers to the lateral position movement between an 18" rim's leading and trailing edges, equating to a change of around 0.125 degrees of toe.

 

[zzr1200]

Being as the toe-in can be between 1/16th and 3/16th, why do you feel the need to stretch the distance the toe-in is measured over the oem spec ie:- the standard wheels radius?

The best you can do at the moment really is centralize the steering and get the wheels parallel-ish.
Unless you can add weight to the chassis to simulate the complete cars weight (including body shell/fuel/oils/driver/passenger) with the wheels in contact the ground, and to compress the suspension you will never get the correct toe-in measurement anywhere near.

Then the rebuilt chassis will need to be bedded in, suspension bushes settled, coil overs/shockers and then fully loaded again to adjust for best handling...

http://www.lotus-europa.com/manuals/lotuswest/54WS094.html

 

[Dilkris]

Being as the toe-in can be between 1/16th and 3/16th, why do you feel the need to stretch the distance the toe-in is measured over the oem spec ie:- the standard wheels radius?

The best you can do at the moment really is centralize the steering and get the wheels parallel-ish.

Because by "stretching the distance" as you call it I am in effect magnifying the measurements I need to attain - measuring 1mm with string is pretty much impossible - but measuring 3mm or 4 mm not so.
Please also read Bob's thread above and my reply to him.

 

[MetalMonkey]

You should be able to accurately measure to less than 1mm with string. You can get fine elasticated thread if you want to get really accurate.

Geometry is very much a dynamic thing, you could spend a lot of time getting everything to three decimal places, drive it around the block and find it will have changed by half a degree. Certainly it will the first speedbump you go over. That is just a function of the movement and play in the system.

Laser alignment is convenient and accurate, if done properly (which is seldom IME), but a string alignment done carefully by somebody who knows what they are doing can be just as good in practice. Racecars are often still set up this way, as I'm sure you are aware.

If you want to dial it in perfectly you will need to cornerweight it, with the drivers weight and account for the appropriate fuel load, anything else is only ever going to be "approximate" anyway.

From personal experience, shoot for the best you can do but don't obsess over it.
When trying to be that precise, you are well past the point of diminishing returns and its very easy to get into placebo territory.

 

[zzr1200]

Because by "stretching the distance" as you call it I am in effect magnifying the measurements I need to attain - measuring 1mm with string is pretty much impossible - but measuring 3mm or 4 mm not so.
Please also read Bob's thread above and my reply to him.

Yes i agree but unless you compress the suspension and get all the angles (caster/camber) set there's very little point in setting toe-in to a minute setting, as the caster/camber angles will change once the chassis/body/fuel/oils weight causes the suspension to compress.

Try jacking up one corner of a car with a trolley jack while watching the tyre/wheel as the vehicle is lifted the Camber angle changes as the suspension drops. Which also changes/effects the toe-in angle while the wheel is off the ground, once lowered the wheel is at at odd angle until the vehicle moves and the suspension settles bring the all angles back into spec...

And depending if the steering rack is in front or behind the axle this controls if toe-in or toe-out is added while the suspension has no weight on it until the vehicle back on the ground and moved to settle the steering/suspension.

PS.

The reason the toe-in spec is between 1/16" > 3/16" is because of tyre case construction/design some tyres are much stiffer than other which also effect's the toe-in spec because basically toe-in controls tyre scrub. So technically you should inspect the tyres running surface for scrub/wear and adjust to control tyre surface damage.

 

[MetalMonkey]

Just to echo the above, if you can't do it with the vehicle on the wheels, you will need to make or buy some alignment stands which bolt onto the hub so you can load the suspension with the weight of the vehicle. Doing it unloaded is pointless for the reasons given.

 

[minimutly]

Good thread. String and camber gauges, in my experience have proved to be good enough. And if you hop up and down on the ends and the toe in changes appreciably you have bump steer - fix it, or you may find it also gives roll turn in, which will kill you.

 

[Morrisman]

That is correct. Beat me to it. There are a couple of other cars built this way too, but I cannot remember what they are.

My old Morris 8 had the rear side windows half an inch taller on one side than the other. Hard to believe they would manufacture the huge stamps required to forge the body panels and make such a mistake.