Caster Angle

[Bern]

Can somebody let me know what the Caster angle should be?

I see in the manuals it has:

+1°; +0.5°, -0

But I don't understand, does it mean that it should be between 1° and 1.5°?

Cheers,

Bern.

[dapinky]

But I don't understand, does it mean that it should be between 1° and 1.5°?

Basically, yes - but as close to 1 deg as possible

[Bern]

Great, thanks for clearing that up Dave.

[Simon_P]

The way it is written is as a value with a tolerance.

The value is +1o. It The tolerance from 1o is +0.5o but - 0o

Ie 1o is good, up to 1.5o is equally acceptable, but less than 1o is not acceptable.

With a tolerance all values within the tolerance are considered equally acceptable. With 1/2o shims this indicates that 1" 29' is preferable to 59'

Personally I'd go for the middle of such a tolerance, but in practice it is down to whatever shim puts it in the range and you are unlikely to have a choice.

[Bern]

I'd have expected it to be 1.25° +0.25° -0.25°, but I guess the way it's written adds more weight to the 1°, as in it has to be at least 1 and then anything up to 1.5 is fine.

I currently have 1°10' on the left and 0°50' on the right. The people that did the alignment decided (or the machine decided) that this was in tolerance.

I'm going to move one of the shims over which I believe should make it 1°20.

I'm also going to try checking the caster angle myself, I've got one of those camber angle measuring tools. I was going to do it 30° in either direction, but I think I saw on here somewhere that it should be 20°, anybody know for certain? Though I'm not sure that the tool is sensitive enough to show such small angles. But no harm in trying it.

At the moment all all the shims at the front of the joint on the left and all bar one on the right, does this sound correct? I guess if it gives those measurements it must be! I'll take them out and count how many I have in case some are missing.

[Giniw]

I'd have expected it to be 1.25° +0.25° -0.25°, but I guess the way it's written adds more weight to the 1°, as in it has to be at least 1 and then anything up to 1.5 is fine.

I would say it's not equivalent, as the target is 1°, not 1.25°

anybody know for certain?

I would stick to the data written in the workshop manual if I were you.

[Bern]

I would say it's not equivalent, as the target is 1°, not 1.25°

You're right not an equivalent at all, but whenever I've seen tolerances before they have always been either side of a central value. But I'm a software engineer rather than a mechanical engineer!!

I would stick to the data written in the workshop manual if I were you.

Unfortunately it doesn't say in the manuals, or not that I can see. Looking around on the web it looks like 20° is the standard. Not sure where I got the idea of 30° from!

Also the manual says a shim is about .25° rather than .5°, so I should get +1°05' if I move it.

[Simon_P]

My reason for suggesting the middle of the tolerance is that it requires less accuracy of measument and equipment ie more likely to always be correct, allows for play, wear etc.

The manual says that moving 1 shim is equivalent to 1/2o

There should be 8 1mm shims.

You need the instructions for the tool to confirm the test method.

For one sided tolerances consider a peg fitting in a hole a tight fit being best but if the peg is to big it won't fit in the hole

[lotusflasherman]

Had mine checked by Hanger 111 who do a lot of setting up for the Elise/Exige trackday and racer brigade. Their computer has Elan dimensions shown in degrees and minutes and has 1°15' (1.25°) as the target for Castor Angle.
Picture below as other target settings might be useful.

geo ls.jpg

I asked for just a check, as I was going to remove any shims if needed rather than pay them for a time consuming process, but front track was a bit out so I got them to adjust that so got 'Before' and 'After' readings. Nothing was changed on rear but 2 measurements changed by 1' (1°/60) and 1 by 2' (1°/30) so a bit of 'measurement accuracy' with their lasers maybe, or a minor movement in rear wheel bearing - but I run mine tighter than Simon likes going from previous 'technical debates' ... Hate to think what changes occur on cars with MOT "Slack Rear Bearings" Advisory Notes.

Oh.. by the way ... I see Bern knows that to type ° you hold down Alt key and hit 0176 on the numeric keypad and release and there is a ° (numbers along top of qwerty keypad don't work as they have different ASCII codes so no idea how you do it on a tablet or phone) but you can also type ± with Alt 241 using same process...

[dapinky]

There are many different ascii codes (most of which are just allocated a key sequence in MS Word etc, but work with many/most typing interfaces - TBH, although 0176 gives a superscript "O", I prefer the sizing by using 167 (but I'm a sad git who learned them before Word Processor programs got advanced!!!)

0176 = °C
167 = ºC

A useful table here

[Giniw]

(Oh, you don't have the° on the qwerty keyboard?! For us it's just over the ')', so shift+')'='°' ^^)

[Simon_P]

Never one to miss an opportunity Phil

Let's have an old gits ASCII athon.

Having thought getting a ° would be impossible on a phone I looked it up. I don't have an alt key but there is one with symbols in its place and it's there!

iOS. From the iOS keyboard on your iPhone or iPad:
Android. Switch to the numbers and symbols keyboard and press the ALT key. The degrees symbol is on the second row.
°°°°°°°°°°°°<>°°°°°°©®¬

[Bern]

I used the ASCII code the first time I used it, then copied it. Once it was in the clipboard I just did a ctrl-v every time I needed it, so no need to remember the code. I even copied it from my first post for the subsequent posts, largely because I'm forgetful and lazy!

The last time I had my alignment done it was at my local tyre place, and they are probably just guys that know how to operate the machine rather than enthusiasts that care about what they are doing. I ought to take it back to the guy in Bristol who did my MX5, he inspired confidence. But I'm going to check the number of shims I have on each side, move the one on the left where the reading was low, and see if can measure the caster angle with what I have. The latter is just to see if I can!

[Bern]

There are 6 shims on the RHS, 5 infront and 1 behind the balljoint.

And 5 on the LHS, all infront of the balljoint!

I've just ordered 5 from SJs.

I've recently replaced the the bushes on the top wishbones, they were really quite soft and worn. Perhaps this was to blame, or at least not helping?!