4 Wheel Alignment

[MetBlue]

First, a question.
When the manual states front Toe in as 3.2mm Total, is that measured from centre of wheel (spindle) to the outer edge of the alloy, or the outer edge of the tyre?
Also, can anyone confirm it is measured as a "Radius" from centre, and not diameter ( from back of wheel to front).

[Zag]

Wheel diameter is my understanding.

[Marten]

First, a question.
When the manual states front Toe in as 3.2mm Total, is that measured from centre of wheel (spindle) to the outer edge of the alloy, or the outer edge of the tyre?
Also, can anyone confirm it is measured as a "Radius" from centre, and not diameter ( from back of wheel to front).

rim edges (rear) to rim edges,(front) at axle height, so actually something you can measure

[AndrewWebber]

Yes and with the car at the 'correct' ride height measured with tyres at the correct pressure and outer diameter.

Andy

[bash]

I do my own with a simple diy laser leveler and have done for years. Never had any abnormal wear when measured at the outer edges of the wheelrim.

Bash

[MetBlue]

I've been struggling to find anywhere in Northampton with 4 wheel alignment equipment who want to be bothered with a check on my car. There is 1 place I've been recommended who have the Hunters equipment that I know is capable of doing the job, but getting past the receptionist is worse than a doctors surgery. So if they can't be bothered, neither can I.
After speaking with Alan at the recent Hinckley gathering, I thought about the TraceAce unit, which looks very convenient for Toe in. Whilst on YouTube though I came across many video's promoting the virtues of "boxing around the car with Parallel string lines. Summary is to place 2 bars front and rear with identically pitched notches (or in my case nails), string between them, then set the strings equi-distant down each side of the car to the wheel centres. - Being lazy, I initially used just 1 string down the side, setting the same distance from each wheel but this doesn't take account of minor track differences between front and rear, plus it doesn't actually save any time because you need to set each side up separately, where as with the 2 string method, once one side is set, the other side is automatically done.

Measuring with a Vernier, I found it very easy to get accurate measurements easily within 0.5mm repeatability (open calliper wide, place the pointer to the alloy, then slide the calliper in to just touch the string).


The results ( below was after adjustment):

*Rear wheel track is about 4mm wider than front wheel track.
*I found I actually had a small degree of Toe Out at the front (not too surprising when the rack was rebuilt with a new outer last year), now corrected and as a result, a small degree of inconsistent steering wheel shake around 60 - 70 mph is pretty much gone. - Based on the above measurements, I could add a bit more Toe In.
*Rear Toe in would be about 5.1mm per side when I centre it. - That's measures on the alloy, so will be more at the tyre periphery.

Which brings me back to my first question posed in this thread about whether measurements are Wheel radius based or Wheel Diameter. Book spec for the rear is 3mm per side, but I've got over 6 if measured on Diameter. Before I started this thread I did a search in the forum on alignment and came across many references where people had similar rear wheel alignment to me ( 6mm on Diameter). Seeing as there is only factory standard adjustment to equalise what's there and not increase or decrease it, I'd like to to think the spec is written based on Radius - But I won't be loosing sleep over it.

Now for the more challenging measurement of Castor

[Pete Boole]

Good one Tony! Caster is not as hard as it looks - the main problem is getting a caster/camber gauge to sit on the wheel in the first place. I made a contraption that fitted to the wheel rims and provided a steel bit to stick a magnetic gauge to. I think they may be in the loft??

Pete

[bash]

I'm beginning to think that Pete's loft is a bit like Mary Poppins bag. When I do mine I set the toe in at 1.6 mm per side at the very front of the rim from the wheel centre, a posh version of your string really which works just as well.

Bash

[AndrewWebber]

Tony, Northampton Motorsport can do it (and corner weights, trust angles etc) They have previously done so on my 'Europa', but yes I use the equivalent of your string box regularly (I put the car on my trailer aligned down the centre and measure in from the trailer bed side edges (that are parallel to my measuring accuracy limits). I've always measured to the wheel rims (you need to rotate the wheels and take an average unless they run exceptionally true). Northampton Motorsport do it as 'angles' so the measuring point is irrelevant. So thinking about that, if you have a set of target figures that quote both angles and mm in/out can you not calculate to check if it is wheel rim or tyre?

As much as static toe in / out, the change under bump and rebound is (in my opinion) even more important, and that is influenced by chassis / rack alignment / position, hence the use of shims etc.

Andy