General Tyre / Tire Discussion

[DogMom61]

It’s time for new tires on my 2018 Forester. Right now it has the original 225/55x18s and I’m looking at 255/55x18, something more off road oriented because I actually do go off road with it from time to time, though nothing like I used to when I played with and constantly repaired my Jeep. So I’m looking at 255/55x18s. What I want are Toyo Country A/T IIIs because they meet my needs and I like the way that they look.

So what I’d like to know is if these will fit on the factory rims and without rubbing everywhere. Do I need spacers and if I do how much in terms of width? Would spacers cause suspension wear? Anything else? I don’t want to lift it and I don’t really want to replace the factory rims.

 

[Ratbag]

@DogMom61
Stick with the original size. 225/55 x18 is already too low a profile for these cars. My wife's 2009 SH has 225/55 17, and they just make the car slightly less comfortable than the 215/60 16 on my SG.

Both cars have Bridgestone Serenity Plus tyres. These are good on the road, and perfectly adequate under all other conditions.

In a previous life, I owned a 1968 Landcruiser, with 750 16 full bar lugs on the back and Goodyear Custom Hi-milers on the front. I used it for towing a 2 tonne, tandem axle horse float. It would go anywhere, except for soft, squishy paddocks and soft sand, where Subarus excel.

ALL spacers are illegal in Australia, as they are fundamentally unsafe ...

 

[Kevin]

^ spacers are legal in the USA - even though I would not fit them even if legal here. Wider is not necessarily better for off-roading because the benefit when deflated is track length not width as width does not change significantly.

I cannot comment on fit for a 2018 but for off-road I would go standard or narrower width and taller aspect e.g. from here: Tire Size Calculator | https://tiresize.com/calculator/


or (if it will clear)



You will also find more info re size over at subaruforester.org

 

[Ratbag]

^ spacers are legal in the USA - even though I would not fit them even if legal here. Wider is not necessarily better for off-roading because the benefit when deflated is track length not width as width does not change significantly.

1) Spacers put more stress on the wheel studs and nuts; and

2) Put more radial stress on the axle and wheel bearings.

The above are not within the engineered design parameters of the vehicle.

They might be legal, but they are dangerous ...

I cannot comment on fit for a 2018 but for off-road I would go standard or narrower width and taller aspect e.g. from here: Tire Size Calculator | https://tiresize.com/calculator/

View attachment 5218
or (if it will clear)

View attachment 5219

You will also find more info re size over at subaruforester.org

Totally agree with this, Kevin.

 

[DogMom61]

I’m not a fan of spacers either, so don’t take my comment to mean that I am, I just mentioned them in terms of fit as I saw somewhere in my internet search about tires rubbing. When I played with Jeeps we routinely used wheels with a different offset so that we could run much wider tires, but then we were going several inches wider and no spacers. We just accepted that we had more stress on bearings and replaced them sooner. That’s not something that I want to do with the Subaru, I just mentioned it out of curiosity. Jeep clubs sometimes do strange things, and we didn’t drive what we off roaded on a daily basis either.

 

[scalman]

for spacers sometimes there is no other option with lift to make rear tire not rub spring . if you still wanna use oem rims. front is fine though just rear problems on 2nd and 3rd gen legacys / obk's

 

[FOZTNQ]

Tyre/tire size limits in OZ

Have seen thread after thread about size of tyres/tires.

Here in OZ not all the states over the years have been consistent, however we have overriding rules at a federal level that the insurance mob refer back too (I doubt any of us would want to take the debate up with them if it goes wrong in an accident and are looking for coverage )

The states have effectively given way over recent times to the common consistency based on the ADR Australian Design Rules, there is a document that defines the limits before needing certificates:

https://www.infrastructure.gov.au/r...Tyres_Suspension_Steering_V2_1Jan_2011 v3.pdf

Tyre/tire size limits in OZ

Have seen thread after thread about size of tyres/tires.

Here in OZ not all the states over the years have been consistent, however we have overriding rules at a federal level that the insurance mob refer back too (I doubt any of us would want to take the debate up with them if it goes wrong in an accident and are looking for coverage )

The states have effectively given way over recent times to the common consistency based on the ADR Australian Design Rules, there is a document that defines the limits before needing certificates:

https://www.infrastructure.gov.au/r...Tyres_Suspension_Steering_V2_1Jan_2011 v3.pdf

This puts our modern subies and such, into the softroader category, if we like it or not - now where is that middle finger when you need it ...

In short (take a read for yourselves) is that:
No more than 15mm diameter increase on wheels (see section 4.2.4)
Or you are running illegal ( or at best in dubious territory )

As mentioned before, of course you can choose to debate, but when push comes to shove I doubt any of us would be wanting to take up a debate over interpretation and definitions with insurance companies and teams of lawyers.
The rules are pretty clear (at least in m mind )


As for other countries, best you check carefully, make sure you are not exposing yourself to liabilities. I would very surprised if our mates in the USA, UK do not have equivalent rules.

Not wanting to preach, but do take care in your choices/advice if lawyers get involved there are normally some nasty witch hunts undertaken, and it would not be healthy to have this great forum put under the microscope.

This puts our modern subies and such, into the softroader category, if we like it or not - now where is that middle finger when you need it ...

In short (take a read for yourselves) is that:
No more than 15mm diameter increase on wheels (see section 4.2.4)
Or you are running illegal ( or at best in dubious territory )

As mentioned before, of course you can choose to debate, but when push comes to shove I doubt any of us would be wanting to take up a debate over interpretation and definitions with insurance companies and teams of lawyers.
The rules are pretty clear (at least in m mind )


As for other countries, best you check carefully, make sure you are not exposing yourself to liabilities. I would very surprised if our mates in the USA, UK do not have equivalent rules.

Not wanting to preach, but do take care in your choices/advice if lawyers get involved there are normally some nasty witch hunts undertaken, and it would not be healthy to have this great forum put under the microscope.

The link provided goes nowhere (404).
However, people are quoting “soft off road” and this 15mm value. (page from a tyre supplier - Victoria?)
THERE IS NO DEFINITION of, SOFT OFFROAD, AWD or 4WD, ANYWHERE IN THE ADRs.
The only definition is “OFF ROAD VEHICLE”, which must meet conditions on approach, departure and break-over angles as well as ground clearances, AND DRIVE TO FOUR WHEELS.
Even AWD’s have that.
It doesn’t mean high/low range, transfer case. Only drive to four wheels.
AFTER THAT there are modification restrictions based one of two things
1/- Lift on a vehicle with both a body and an independent chassis. eg, Hilux, Triton, Landcruiser.
2/- Lift of a vehicle with monocoque construction. Body and chassis are one piece. eg, Subaru.

On the latter it is permitted to make a 50mm lift in the suspension, and 25mm with tires, for a total of 75mm. 50mm diameter in tires = 25mm lift (half the diameter).