as a point of note, NOWHERE does it state in the WA regs that a 1" or 2" increase in wheel width/diamter is allowed - it deals with rims/tyres in the table as set out above;
 
Tyres can be up to 1.3 times the original OEM tyre width, and profile reduced to maintain rolling diameter, e.g:
 
OEM Rear tyres/rim set up on 1990 SW20
225/50/R15
225 x 1.3 = 292.5
therefore max allowable tyre size is 285;
 
suitable rim width for this tyre size is given as:
10.0 for aspect rations 65 to 85; And
11.0 for aspect rations 60 and below.
 
Now this is curious, as a rim would need to be manufactured 12.5" diameter (321mm) to be VSB14-acceptable shod with the maxim dimension 285/50 tyre, to meet the the rolling diameter of athe OEM set up of 606mm;
 
For reference the 606mm rolling diameter figure is made up of:
50% aspect ratio x tyre width = 112.5mm ("upper" tyre wall height) 
15" rim diameter x 25.4 to convert to mm (1 inch = 25.4mm)
50% aspect ratio x tyre width = 112.5mm ("lower" tyre wall height)
 
Again, these ridiculously shaped wheels would not meet the track width increase limitation... 
 
No doubt I will find out the if, how and how to of the scenario as it becomes clear...

Well, it may not neccesarily be meant to be "made to be hard" - these are just ground rules which can be negotiated through practical design and engineers certificates.  Hopefully the piuts inspection is going to be far less technical than the details I've gone into already, BUT if they do defect me for something, it's best to have a good idea of A) the ground rules (so you can if the inspector is being unreasonable - unfortunately there are a lot of stories to this tune) and B) so you know where to "start" looking for your answers.  Start being in inverted commas as the process would generally be
- call an engineer
- discuss the mods you wish to undertake and their feasibility
- submit an application  
- hopefully obtain fully road legal (and fully insurable!) status
 
I think Matt234 is doing it at present for his engine/brake set up - I will be doing it in stages for my 3.0l V6 turbo project if, and hopefully when, I get the car on the road as is (in 2 litre turbo format) come Saturday...
 
The picture I'm getting is that it's all about safety and ensuring the mechanical, electrical, hazard warning and practrical aspects of the car are in good road worthy order.  The remainder re: rim sizes etc is all about what the inspector spots on the day, and whether or not it's a glaring fault. My potential fears of failure for tubbing/flaring the arches, use of fibreglass panels have been partially allayed by the published  VSB14 docs, so I know where I stand. 

 "OEM Rear tyres/rim set up on 1990 SW20
225/50/R15
225 x 1.3 = 292.5
therefore max allowable tyre size is 285; "

1990 cars had 14" wheels OEM (45mm offset, rim width, 6" and 7").
 
My 1990 doorpost placard says, tyre size front 195/60R14 - 85V, rear 205/60R14 - 88V
 
15's came in after '92 
 


Apologies for delayed response on this one - I DID say I'd post up the outcome of my pits inspection:  which PASSED in 20 minutes!  Seems a false celebration here as it happened so long ago now(!) but to round off the discussion at least in terms of WA, pits inspectors PASSED front 215/40/17R +35 and rear 235/40/17R rims +45, WITH flared arches, so rims were stucked ~50mm "in" from flush.  It looked shocking, but it passed...

I have heard in the past that you can increase your rim width by 1 inch and still be legal though I haven't verified this to be true.

bass6153

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