Different offsets and front and rear

[ebola]

You will find that to pass engineering you can only increase the rim width 1.5 inches on an MX5 and the track by 20mm. This means that to pass engineering a max of 7 inches. Take into account that the increased width will increase your track (assuming the same offset) so you will not be able to lower your offset much at all and expect to pass.

If the wheel has the same offset then the track width will be exactly the same for the wider rim as for the narrow rim.
The track width is the distance between the centrepoints of the rims.

Oh.. My mistake. Well the overall width of the parts of the car touching the road must not be more than 20mm greater than standard.


And yes. You prolly shouldn't tell the police to fark off, even tho it may seem like a good idea at the time. They are not going to do you any favors if you are rude to them.

[rascal]

Oh.. My mistake. Well the overall width of the parts of the car touching the road must not be more than 20mm greater than standard.

Actually, thats also not correct. If you put wider tyres on the std rims then the tyres touching the road will be wider but the track will be the same so not an issue.

[ebola]

Oh.. My mistake. Well the overall width of the parts of the car touching the road must not be more than 20mm greater than standard.

Actually, thats also not correct. If you put wider tyres on the std rims then the tyres touching the road will be wider but the track will be the same so not an issue.

Why would you engineer standard rims? Anyway, if you did have them engineered then the wider tires would not be able to add more than 20mm to the total.


When my wheels were engineered (in NSW about 2 months ago):

- The back of the rims were looked at for the listed size and width. A photo of this went into the report along with a photo of them on the car.

- Then the engineer measured the total width of the car between the outers of each of the tyres.

- He also noted the tire sizes and checked a chart for if they are supposed to be on those rims.

- He also checked the Speed/Load Rating of the tires and compared the rating to the minimum listed on my drivers door.

- Then he checked there was no scraping anywhere from the new rims.

[StanTheMan]

Oh.. My mistake. Well the overall width of the parts of the car touching the road must not be more than 20mm greater than standard.

Without being toooooo anal about it. Its actually maximum increase of 25mm.

http://www.rta.nsw.gov.au/registration/ ... 9_rev4.pdf

also My interpritation which may or may not be correct is.

it goes on about maximum wheel sizes for different weight of vehicle.
a note

Note: 25mm increase in wheel track limit also applies

to me, that means,a wheel with offset difference of more 12.5mm can't be engineered. (right?)

which means that even if the person gets the wheels with +25 enineered......they will be defectable?

which leads to .....why bother with enineering......if you are going to do it anyway.

on the other hand. a reasonable copper will most likely look past that, if everything else has been engineered correctly.

[ebola]

a reasonable copper will most likely look past that, if everything else has been engineered correctly.

Yeah prolly. (if you dont give them a reason not to anyway )

and yes 25mm not 20mm..... I must be getting old. My memory is fading.

[rascal]

Why would you engineer standard rims? Anyway, if you did have them engineered then the wider tires would not be able to add more than 20mm to the total.

- Then the engineer measured the total width of the car between the outers of each of the tyres.

The std rim reference was just an example to highlight that tyre width was unimportant with respect to track.

The reason the engineer would measure to the outers of the tyres, is its easier to determine the track,ie by also measuring the width of the tyre itself and subtract one tyre width (1/2 width from each side) from the total width to get the track.