Tyresome decisions

[brad]

I had a feeling the 235 size tyres were too big for the RIM width with the PS3s. Thats my last recollection anyway.

in 18" 40 series yes they are outside of the manufacturers limit of 8"-9.5". Gerrycan has 17" 45 series

You are probably right, looking at the placard the 7Jx17 rims are ok for smaller widths but not bigger

Only 7" on yours? I've assumed all the 17" rims on VW/Audis/Skodas are 7.5" (all the ones I've bought / almost bought were) which are fine for a 235/45r17 (7.5"-9"). Proof that you should never assume.

[woofy]

Every mazda I have ever owned had narrow rims as well which meant I was always stuck getting expensive odd sized tyres.

[dArK5HaD0w]

I wanted to put 225/45r18 on mine the other day, but the tyre shop said it would be illegal.
I didn't think it would've been an issue.
The std size is 225/40r18.
I was after some more tyre height for a bit more quietness and comfort.

Ended up getting the ContiMaxContact instead of the usual ContiSportContact.

[Martin]

You would need to reduce the width to increase the profile

Looks like you may have purchased MC5's?
They have a reputation for poor mileage

[brad]

I wanted to put 225/45r18 on mine the other day, but the tyre shop said it would be illegal.
I didn't think it would've been an issue.
The std size is 225/40r18.
I was after some more tyre height for a bit more quietness and comfort.
.

In what way did they say they would be illegal? load rating, make the speedo read really wrong?

A lot of places use made up legalities to cover their own arse.

/looks at sizes... Based on my experience with my car, they probably would have rubbed under hard cornering bumps and your speedo would have been 100 speedo = 102 actual which isn't good.

You'd be better off reverting to 16"x7.5 with 225/55r16 or 17x7.5 with 235/45r17

[dArK5HaD0w]

In what way did they say they would be illegal? load rating, make the speedo read really wrong?

A lot of places use made up legalities to cover their own arse.

/looks at sizes... Based on my experience with my car, they probably would have rubbed under hard cornering bumps and your speedo would have been 100 speedo = 102 actual which isn't good.

You'd be better off reverting to 16"x7.5 with 225/55r16 or 17x7.5 with 235/45r17

I believe they said the rolling circumference would've increased by more than 100mm, making it illegal.
they also said the bigger tyre would likely be hitting/rubbing against the suspension struts.

I was aware of the speedo being out of whack with the bigger size.
load rating was not an issue. they had 91W for 225/45r18.

[The_Hawk]

This is a great place to see what changes with different wheel and tyre combos:
Custom rims, wheel tire packages for your ride - RIMSnTIRES.com

In your case it looks like this:





Personally I've just gone from 225/45R17's to 225/40R18 and was expecting it to be far harsher than it's turned out. My other 18's in the shed had Conti's and feel harder vs this time I went with RE003's which feel very nice to drive on.

[brad]

I believe they said the rolling circumference would've increased by more than 100mm, making it illegal.
they also said the bigger tyre would likely be hitting/rubbing against the suspension struts.

I was aware of the speedo being out of whack with the bigger size.
load rating was not an issue. they had 91W for 225/45r18.

Assuming the ACT uses Vehicles Standards Bulletin 14 you are legally limited to +15mm diameter and your proposed change was +23mm. I've was running +20mm on my last set of tyres and it rubbed on the guard liner if I hit a bump in a corner - but my car is lowered as well.

There are plenty of standard height Superbs that have made the switch from 225/40 to 225/45 without issue and they are basically the same suspension as the Octavia.

BTW, it only ads 71mm to the circumference but that isn't part of the standard, so I guess it doesn't matter that they got that part wrong.

[dArK5HaD0w]

Assuming the ACT uses Vehicles Standards Bulletin 14 you are legally limited to +15mm diameter and your proposed change was +23mm.

I think that's what they were referring to.
mine is also lowered - 30mm upfront and 20mm at the back.

if only someone with a superb had a spare set of 4 wheels, running 225/45r18, that I could trial fit!!! hehehhehehe

[brad]

It will be the lowering that is the issue. The Scout runs a 225/50r17 which is almost the same diameter and doesn't have clearance issues with the strut spring seat or bodywork.

With all the roundabouts in the ACT you wouldn't have been happy.