Wheel advice

[brad]

Harlie - you need to know how far wrong your speedo is at the moment before you make changes

[donweather]

If you're looking for some decent tyres at a good price then give Goodyear Croydon (Vic) a call. They have a range of common VAG sizes in their F1A2 performance tyre at competitive prices to tyre rack. Plus your getting warranty and guaranteed fresh rubber. There's quite a few people that have bought tyres from here.

That's exactly who I bought them from today. But I completely forgot to ask if they were 92Y. I hope they are!!!

Edit: just checked they're website. 92Y. Lucky!!

Tyre Search, Goodyear Autocare, Australia

[tigger73]

DUBGTI let me know if you want to test your speedo. I have a GPS speedo in my possession at the moment.

[Dutch77]

Mine was in for an alignment to sort the rear geometry during the week. Local tyre shop recommended I go to 235/40R18 next time - cheaper tyres ect ect - they are 8mm larger in diameter. are they wrong?

Now I'm shopping for wheels - 18x8 et45. during balancing they noticed one of my badly scratched neptunes has what he calls a flat spot, (I call it buckled) on the inner rim - that will be the vibration at 100kmh.

Tyre shop is correct on both counts (but I agree with Brad's advice, check it out before playing is preferable).

8mm larger diameter, which means you will be going a fraction slower than indicated. 235/40/18s are often cheaper than 225s as the 235s are a common Falcodore 18 inch fitment and thus bought in large quantities.

Loads of wheel options, check out the Mk7 thread if you like as plenty of 18x8 ET45 or similar wheels in there.

[harlie]

Harlie - you need to know how far wrong your speedo is at the moment before you make changes

Thanks, my Speedo reads 5% over what the GPS says. Speedo says 100, GPS 95. 60/57 ect ect. So the 1.2% circumference that 235 is over 225 is not an issue, will bring the numbers closer. I as more concerned with clearance.

[Mysticality]

18x8 ET45 235/40R18 will fit FINE if you get the inside of the rear guards cut out. (easy job, 5min with a dremel)

Zei20t's wheels, IMO, will NOT fit (19x8.5 235/35R19) once he's lowered. He's at stock height at the moment which is a massive difference as far as clearance is concerned.

18x8 ET45 245/40R18 *may* fit, I'm yet to test this though.

[Hillbilly]

Hey can I ask how accurate your speedo is? the tyre calculator shows your setup to be almost 5% larger than stock and would result in a roughly 5km/h difference from stock. At an indicated 100km/h on your speedo your actual speed would be roughly 95km/h, but how accurate are they at that speed to start with, most cars would read less than 100km/h at an indicated 100km/h to start with, is this increased with your size tyres?

I am trying to stay as close as possible to the stock rolling diameter to avoid and potential issues be it with the car or the law
I'm just cautious off speeding fines......haha, I'd be thinking I'm going at the speed indicated on the speedo, but actually doing another.

cheers

In fact ALL car speedos must read over the speed you are actually doing and legally cannot read less.
The ADR rule states that they may be up to 10k over at 100kph <> 4 so they could be up to 14k fast but are not allowed to read under.
Putting larger tyres on makes it read slower but in my case in the Polo it is 7k over and to get it right would take tyres 40mm larger which are illegal

See here for accurate alterations Custom rims, wheel tire packages for your ride - RIMSnTIRES.com

[brad]

In fact ALL car speedos must read over the speed you are actually doing and legally cannot read less.
The ADR rule states that they may be up to 10k over at 100kph <> 4 so they could be up to 14k fast but are not allowed to read under.
Putting larger tyres on makes it read slower but in my case in the Polo it is 7k over and to get it right would take tyres 40mm larger which are illegal

See here for accurate alterations Custom rims, wheel tire packages for your ride - RIMSnTIRES.com

Hillbilly, if I can move mine 8kph by going up 20mm in diameter (which is still illegal) then why do you need 40mm to move the same approximate error? What am I missing?

[Hillbilly]

Hillbilly, if I can move mine 8kph by going up 20mm in diameter (which is still illegal) then why do you need 40mm to move the same approximate error? What am I missing?

Well according to the comparator I posted a 195/55/15 has a diameter of 595mm on a 5.5in rim

To get a 6.7% difference I would have to go to a 195/65/15 which has a diameter of 635mm. Diff is 40mm

Remembering the diameter is right across widest point and not the radius which is from the centre to one edge. In QLD 26mm is largest legal diameter difference
Put the figures in the comparator with the larger size on the left and you will see.

[tigger73]

Hillbilly, if I can move mine 8kph by going up 20mm in diameter (which is still illegal) then why do you need 40mm to move the same approximate error? What am I missing?

It'll be down to % change in rolling diameter. If Hillbilly is looking at a Polo it likely runs a smaller size wheel so the same change in mm will be a bigger % change compared to a Golf/Octavia or something bigger like an Amarok/Touareg.