The new VSB14 & Tyre Size

[Ratbag]

For future reference, these rules are all available online:
https://infrastructure.gov.au/roads/vehicle_regulation/bulletin/vsb_ncop.aspx

For raising/lowering vehicles, Section 4.11 of
https://infrastructure.gov.au/roads..._LS_Tyres_Suspension_Steering_Nov_2015_v4.pdf

Gidday Duncan

As I read the new VSB14, it now means that I can put 225/60 or 225/65 x 17" tyres on our SH legally.

225/60 17 would probably improve the car's comfort considerably, without dramatically worsening its handling. As SWMBO doesn't exactly drive like Jack Brabham, the handling should not be problematic. Tyres with better handling than the current Geolandar G95 (almost everything ... ), such as the Bridgestone Ecopia/Dueler tyres should compensate for the increase in profile ratio.

Fitting 225/65 17 would completely correct the appalling speedo error (nearly 10% over at 100 Kmh!), but might make the handling a bit more soggy. However, it appears to me that the not so good handling of our SH is mainly caused by a combination of body roll and higher centre of gravity (than our SG). The body roll comes from the body height and softening the suspension to compensate for the ridiculously low profile tyres for this kind of vehicle, and the discomfort those tyres cause.

I am not prepared to pour a grand or two into rectifying the compromises made in the spring rates and suspension for reasons no better than fashion ... . However, I am happy to fit slightly larger tyres to the existing rims to help with some of these things.

It also appears to me that there is easily sufficient space in the SH spare wheel well for the 225/60 17, and possibly even for a 225/65 17. Anyone know?

Overall/specific thoughts, anyone?

 

[duncanm]

Looks like 4.2.4 answers your question.

"Overall diameter .. must not be more than 15mm larger .."

 

[Ratbag]

^ That appears to be contradicted by clause 4.11 LOWERING OR RAISING VEHICLES??

 

[duncanm]

not really.

4.11 is giving examples of how you could achieve 50mm lift. 'may be achieved as a single modification, or by a combination of smaller lifts as described below'

This can be done with tyres alone on 4wd (max 50mm diameter), but not AWD/Subaru, as per 4.2.4