MX-5 Wheel Alignment Specs..

[Administrator]

Thanks to Charlie Brown.

Here we go again; these specifications have been gleaned from people far wiser and more knowledgeable than myself. I am just a poor lowly scribe trying to understand.

Mazda Specifications are:

Front
Caster: 4.83 deg min. to 6.83 deg max
Camber: -1.10 deg to +1.10 deg
Toe: -0.05 deg to +0.35 deg

Rear
Camber: -1.78 deg to +0.22 deg
Toe: -0.05 deg to +0.35 deg

There is a huge range of possible set ups within the Mazda tolerances and there are combinations within these tolerances that would make your MX5 handle like a real dog. The MX5 is very sensitive to minor alignment changes and you can get great handling rewards by getting the setup just right.
You need to decide on a combination that meets your driving requirements, be it casual, spirited, aggressive or track and then have a reputable aligner carry out the work.

My alignment requirements are based on the following:
*I drive the car daily to work (70k round trip) and do the odd track day.
*The car is completely standard.
*I wanted an alignment that would work with occasional spirited driving and would not wear the insides of my tyres.

I headed off to Spinning Wheel, a known race alignment specialist that has done work on many MX5 Club cars and told them my requirements.
Shown below against “Spirited Driving” are their alignment numbers. These work extremely well for day to day driving and are very similar to CT’s shown further down the page. You get great feel, good turn in and neutral or balance handling characteristics with these settings.

After a couple of runs at Wakefield and a new set of tyres I decided I would like something a little more aggressive. I also wanted to try and reduce roll oversteer, after an “off” at 120kph at Turn 3. This is not something that I would have come across during normal road driving activities, only on the track at the limits of adhesion. So back to Spinning Wheel and the new spec’s are shown against “with track days”. The increase in rear toe in seems to have controlled the roll oversteer I had in Turn 3.

Front
Caster: 5 deg plus
Camber: Spirited driving: -1.00 deg, With track days: -1.10 deg to -1.50 deg
Toe: Spirited driving: 0.28 deg (2mm in), With track days: 0.13 deg (1mm in)

Rear
Camber: Spirited driving: -1.00 deg, With track days: -1.50 deg
Toe: Spirited driving: 0.13 deg (1mm in), With track days: 0.34 deg (2.4mm in)

Note: The larger the bias between front and rear camber the more understeer the car will have.
Toe out on the front gives better turn in but car will dart around (tramline).
Toe out on the rear is very bad in a MX5. It causes roll oversteer. Remember if you set it at 0 degrees, when you sit in the car your weight makes it go toe out. Always have some toe in to allow for this.

CTZooms alignment is:

Front
Caster: 4 deg + (Maximum positive castor, sacrifice a little neg camber to get it if you have to.)
Camber: -1.00 deg
Toe: 0.0 deg (CT’s comment: “a little toe out with a stock front sway bar can give more turn in but not my preference”)

Rear
Camber: -1.00 deg
Toe: 0.15 deg in (total)

CT’s comment: “The car will be neutral, tyre wear will be fine, it won't dart around and won't give you any nasty surprises”.

And for a bit of comparison as it always pops up -

Lanny’s alignment (from Miatanet) http://www.hummingbirds.net/alignment.html is:

Front
Caster: 5 deg
Camber: -1.20 deg
Toe: 0.075 deg in

Rear
Camber: -1.75 deg
Toe: 0.075 deg in

[CJ5]

so, has anyone used these? results?

[JBT]

CT Zoom's figures with 2mm toe in front and rear. Works fantabulously on the road and for track days.

[Alex]

I just had my alignment done to Carlie Browns specifications, noticeable difference to how it was before, feels a lot less skittish in corners and it should help get even tyre wear. I'll have to reserve a proper judgement until later because I think they reduced my pressures while they were at it.
From the printout

Before
Front Toe: 2.9mm
Front Camber: -0.5 deg
Front Castor: 6 deg
Rear Toe: 4.3mm
Rear Camber: -1.15 deg

After
Front Toe: 1.5mm
Front Camber: -1 deg
Front Castor: 5 deg
Rear Toe: 0.7mm
Rear Camber: -1 deg

It didn't turn out exactly as I specified but it's better than what it was.
I would recommend everyone to specify the alignment settings when getting one done, I didn't last time and look at what I got.

[sliq]

dumb question.

do u need a camber kit to change wheel camber?

[Alex]

nope, but it is limited with the stock setup.
From the original post it looks like -1.1 deg is max camber on a stock setup.

Also after a bit more testing, more neutral in medium-high speed corners, where there was once understeer there is none. More oversteer at low speed corners though but it seems more perdictable than before and comes back cleanly.

[Charlie Brown]

A quick note: The specs I posted in this thread is for an NB (will work on a NA).
I think that in hind sight I'd put a little more rear toe-in for Spirited driving at 1.0 - 1.25mm per side or 2 - 2.5mm total to assist in high speed stability.

This alignment should not be used on an NC. I have given a guide in another thread for the NC as the NC runs a completely different suspension to earlier models.

[BadBong]

Getting new 16*7 wheels this weekend and i'm wondering whether CB's alignment specs will work with these wheels? (given my NB8A comes with 15" originally).

The new 16*7 wheels are identical to NB8B's stock wheels by specs though.

Can someone give me the alignment specs i should hand to the fitter in plain English please? (sorry, i have NO idea what the campers and toe means atm... )

[SPy vs. SPy]

Getting new 16*7 wheels this weekend and i'm wondering whether CB's alignment specs will work with these wheels? (given my NB8A comes with 15" originally).

The new 16*7 wheels are identical to NB8B's stock wheels by specs though.

Can someone give me the alignment specs i should hand to the fitter in plain English please? (sorry, i have NO idea what the campers and toe means atm... )

Wheels (should) make very little difference

Front
Castor: 5 or more degrees positive
Camber: 1.00 degree Negative
Toe: Spirited driving: 0.28 degrees total toe IN which equates to 2mm total toe IN

Rear
Camber: 1.00 degree negative
Toe: Spirited driving: 0.13 degrees total toe IN which equates to 1mm total toe IN

GET A PRINTOUT OF BEFORE AND AFTER, I cannot stress this enough. The left numbers will be slightly higher than the right if the guys do the right job, this will be so the car drives straight along the road, as roads are higher in the middle so that they drain, if the alignment was dead even the car would always run to the left down the gradient of the road.

Hopefully to help you understand whats what, here's an analogy.
Imagine you were holding two cricket bats just in front of you with the bottom of each bat on the ground with both faces toward each other and parallel. The bats are both 100% vertical.

This is zero everything

Now keep the bottom of the bats in the same spot and do the following.

Lean both bats back toward you at 5 degrees, you have just adjusted the castor positive 5 degrees, if you moved them away from you it would be negative castor.

now move your wrists together so the bats now lean in 1 degree each side, you have set the camber, this time negative 1 degree. If you moved your wrists out, that would be positive camber.

now twist both wrists inward a little i.e. the edge closest to you is now further away from the other bat, and vice versa on the edge facing away or the front edge of the bats are now closer to each other, you have now set the toe a poofteenth IN. Again if you went the other way this would be toe out i.e. the front edge of the bats are now further from each other.

Your tyres with the above spec should wear evenly and the car will corner and go everywhere so nicely you won't know yourself.

Hope this helps.

SPy

[BadBong]

Thanks Spy, ad great analogy as well.

The only bit that i'm unsure about is camber :

"now move your wrists together so the bats now lean in 1 degree each side, you have set the camber, this time negative 1 degree. If you moved your wrists out, that would be positive camber."

[SPy vs. SPy]

Thanks SPy, and great analogy as well.

The only bit that I'm unsure about is camber :

"now move your wrists together so the bats now lean in 1 degree each side, you have set the camber, this time negative 1 degree. If you moved your wrists out, that would be positive camber."

Open this in another tab/screen/window depends on your browser.
http://upload.wikimedia.org/wikipedia/commons/5/5e/Isoscelestriangle2.svg
Ignore the lines running through point E they're meaningless for this explanation.


If your hands are at B&C and the bottom of the bats are A&D this illustrates Neg camber. i.e. the tops off the wheels are closer to each other.

If you turned the diagram upside down and the bottom of the bats became B&C and your hands A&D that would illustrate positive camber. i.e. the tops off the wheels are further from each other.

Hope that makes it clearer.

SPy

[BadBong]

that makes perfect sense... but that was what i thought the castor meant...

so my next question is... what is the Castor then?

[SPy vs. SPy]

that makes perfect sense... but that was what i thought the castor meant...

so my next question is... what is the Castor then?

picture
http://upload.wikimedia.org/wikipedia/commons/1/11/Trapezoid.svg

This time we're viewing the car from the side

Left side of the diagram is the rear of the car, right side is the front of the car.

Ignore the line A-D and imagine the line h is the castor of the rear wheels i.e. neither neg or pos as we cannot alter this setting.

The line CB is the castor of the front wheel as set by the steering geometry imagine the mid point of the axle is half way along that line, therefore the theoretical contact patch of the tyre is in front of the axle line, giving you positive castor.

The other way to explain it, a razor scooter has approx 0 degrees castor whereas a bike or motorbike has positive castor, a Chopper has even more stupid castor and as a side effect a stupidly huge turning circle, whereas the razor scooter can turn on a dime (but only at a slow enough speed)

here's some pictures
http://en.wikipedia.org/wiki/Castor_angle

More explanations here
http://www.ozebiz.com.au/racetech/theory/align.html

[BadBong]

Thanks Spy, the diagrams on your 2nd link is exactly what i need.

[broady]

Here's what I just got done down at Spinning Wheel in Waterloo. The car feels fantastic!

max caster

front camber -.5 deg
rear camber -1.4 deg

.2 deg toe in front .3 deg toe in rear