Geometry Alignment

[sorepaws]

If this has been covered before I apologise

I have a 1991 Auto and was wondering if the changes to the Geometry that were applied to the later cars can be done to a '91 - The reason for asking is the usual issue of high rear tyre wear.

Thank you in advance for the help

Regards

Mike

[NSXGB]

Yes they can.

[sorepaws]

Thank you -
the car is now almost 19 years old and time for Kaz to spend some time on it I just hope my bank balance is upto the job. Looks like I have lots of work for Kaz !

[NSXGB]

If you are going to Kaz, use his alignment place JPS. Very reasonably priced, the guy knows what he is doing with regard to the NSX (trained by the master!) and the guy is a perfectionist. When my car emerged from their workshop my settings were either perfect from side to side or within 1'.
I did try using Wheels in Motion who come very highly recommended across many car forums but in my experience JPS knocks them for six as far as the NSX goes.

[Senninha]

Hi Simon,

How long does the alignment take on average? I haven't done mine for a couple of years and whilst I've not hit anything (potholes incuded), something is not quite right.

Maybe this could be a group event?

regards, Paul

[dan the man]

Paul- Lack of sideways action means Geometry often goes out

;P

[NSXGB]

Hi Simon,

How long does the alignment take on average? I haven't done mine for a couple of years and whilst I've not hit anything (potholes incuded), something is not quite right.

Maybe this could be a group event?

regards, Paul

I can't remember exactly how long it took, maybe 1.5 hours for me but we had some problems.

[Lotus Roy]

Hi,

I am about to get new rear tyres for my '91 manual. Having alignment done on their Hunter system. Problem is toe in setting is in degrees not mm. Does anyone know what 3mm equates to in degrees and minutes? Or how to convert one to the other

[goldnsx]

y (in deg) = invtan (x (in mm) / 1000)
3mm = 0.17 deg
if you have minutes instead of degrees: 0.17 * 60 = 10.3 minutes

[Lotus Roy]

Brilliant, thanks.
Roy

[Kaz-kzukNA1]

No longer posting on the forum like I used to and mainly focusing on the blog but this one caught my eye so hope I can share my experience.

You really want using the unit in deg and not in length (mm/inch) to remove the tyre size effect.

Not sure it's still the same with the latest software version but when using Hunter machine at the alignment platform I use, if you set the display unit in length (mm/inch) rather than the default setting of degree, the software is going to use virtual external tyre diameter of about 726mm unless you set it up to use OEM tyre size spec.
Not ideal for much smaller tyre diameter on our NSX and thus, should use deg.


Toe [deg] = ArcSin (toe[mm] / tyre external diameter [mm])
1deg = 60min

Although the equation includes the external tyre diameter, it has very minor effect so you can use pretty much the following for all OEM rear tyre spec or similar.

225/50/16, 245/40/17, 255/40/17 or similar; Toe 3mm = 0.27deg = 0* 16' (0deg 16min)


By the way, this 3mm toe, are you referring to one side or total toe?
Please double check the rear toe data stored on the machine.

By default, for 91 model, it would be using the original setting of 3mm toe per side that is 6mm total toe.
While you can still use this (and I was using it when I used to drive my NSX in Japan), for UK road surface and weather condition, I normally set all NSX including mine with Rear toe per side at +0* 11' +/- 03' (equivalent of toe-in of 2.0mm) that will result in total toe of +0* 22' +/- 06' (equivalent of toe-in of 4.0mm). Then, you need to customise this to one's taste depending on the chassis setup but good starting point.
This is the same as the modified spec released by Honda/Acura.

Kaz