What size tyre should I fit?

[leegil]

I just purchased a set of Speedy FIN Lite dark silver (darker than hyper black) in 18"x7.5".

They don't sell them here in Aust. anymore so sadly had to import from the US. Should be ere in a couple of weeks. It seems like the only place that may have them was in the US as the UK no longer has them and not many other countries have them either anymore in the dark silver/hyperblack colour. The silver colour is available, but not my cup of tea.

I am going to get them installed with Kumho KU31s, just not sure of the best size. Either 215/35/18 ($150 installed each) or 215/40/18 (approx $190 installed each).

My Polo GTi is not lowered (no intention to lower it). A larger profile tyre will 'fill' the gap' with the body panel a little better and importantly, has more give if I hit something hard unexpectedly.

Has anyone installed 215/40/18 on their polos? If so, can you send me a pic (or direct me to a pic that appears somewhere on 18" rims).

[Blitzen]

What's the offset of the wheel? I would go the 35 profile rubber. The 40 profile rubber will look out of proportion, and will scrape on the inner guard more easily, as the sidewall is higher than the 35 profile rubber... Also, the 40 profile tyre has a larger outer diameter, so this will throw out your speedo even more.

Also, the 35 profile tyres are cheaper... That would get me there!! Where are you getting the tyres for that price?? It's awesome!!

With these wheels, without the car being lowered, it's going to look out of proportion. Getting bigger wheels doesn't mean the wheel gap is going to get smaller... The risk you are is that car is going to look like fitting a 4WD with 24in chrome wheels.

[leegil]

The offset is ET45. I know they fit as they are the same as the Lavinhard FIN advertised at Ozzy Tires (they also have a pic of the polo GTi with them installed). I had a chat with Brad from Ozzy and he confirmed the fit ...but they don't stock it anymore. Just not the colour I like and for the same price, might as well get something I like to look at everyday.

Yeah, I am leaning towards the 35 profile purely because it is cheaper. Prices are from Tempe Tyres in Syd. Also, searched on google and saw other places having that same price (in VIC and I think in Bris). Syd is close by so it is easy drive up for a weekend away. Saw Tempe list on eBay and called them up and they can install it.

Lowering is something I will need to think about after I have the wheels installed, and after the rear sway bar is installed.

[dylan8]

whats the stock sized rubber on your car? id imagine a 215/40 would be too big as thats almost mkiv bora/golf size..
why the 215 size? maybe look at 205/35s to get that profile down some more as those wheels will probably sit in a fair way with a 7.5et45

[leegil]

Kumho website for KU31 specs for 18" wheels has minimum width of 215.

For stock 205/45/16 (standard 16" size) Overall Diameter (OD) on KU31 16" is 590mm, Circumference (C) 1800mm

For KU31 215/35/18, OD is 607mm, C =1851mm
This comparison means diameter encroachment into the wheel arch (vertical measurement) with the bigger size tyre is 8.5mm (negligible increase). Circumference increase by 2.83%. This means my speedo will be 2.8% faster. Given that standard speedo is slow by say 7km/h , there is still a lot of play.

For say KU31 215/40/18, OD is 629mm, C =1918mm
This means compared to 16", 19.5mm vertically into the wheel arch. Circumference difference of 6.56%. This means that speedo at 100km/h would close to actual wheel speed.

The width of the 35 profile and 40 profile is the same at 218mm, no difference on the 215 width.

This is why mathematically a 40 profile may work, assuming suspension travel doesn't result with the tyre rubbing when 'bumped'. My concern is that a 35 profile may look 'too thin', whereas 40 profile may look just right

I'll have to visit some tyre stores to check some tyres out at those sizes next to my car.

[Blitzen]

I have 35 profile rubber on my 18, so that could be a good yard stick...
This is what 18s with a 10mm ride height drop looks like...

[Buller_Scott]

whatever you do, leegil, dont make the mistake of putting your swaybar on max hardness with otherwise stock suspension, hoping to ''increase cornering performance''...

it will snap oversteer on you like a motherb7tch... i've got a bent wheel in the shed that will agree with me.

[leegil]

Saw the following pics that helped me make the decision between low or high profile.

The Polo GTi looks perfect with low profile. Not keen on black wheels anymore as it tends to get 'lost'. If you are going to have wheels, the you should be able to see them
Matching Wheels & Rims | Car Gallery |- Ozzy Tyres

The Lancer looks a bit strange with a highish profile.
http://clubcj.net/garage.php?mode=vi...&image_id=2578

The Mazda looks better with lower profile.
Imageshack - p8020914.jpg
Imageshack - p8020923.jpg

The 35 profile is the one I will choose. Thanks for your thoughts.

As for swaybar, was thinking about a max hardness but will raise a question on general thoughts in the appropriate topic. I want that go-kart feel but still OK for handling daily driving bumps.

[Buller_Scott]

As for swaybar, was thinking about a max hardness but will raise a question on general thoughts in the appropriate topic. I want that go-kart feel but still OK for handling daily driving bumps.

sway bar + stock suspension, even when set on hard (on the sway bar) didnt affect how the car handled bumps - the car was still undersprung and underdamped. what it DID do, though, is force the rear to become more unpredictable upon sharp direction changes (especially in the wet!).

if you want go-kart feeling, you MIGHT be better off getting H&R lowering springs (which make the polo look really tidy, nice and low but not too low, and it'll compliment your bigger wheels too, helping you to avoid the jacked-up roller skate look that you can get if you keep stock suspension height when adding larger wheels).

do a search, there are plenty of reviews of people with polo gtis who did just h&R lowering springs, who like it.

[leegil]

Just threw my hand behind and above the front wheels and there definitely isn't much room around on the 16"x6.5" standard setup. I don't even know what I was thinking when I considered a 40 profile...unlikely to fit.

The width is the biggest concern when going 215 wide on the tyres. Clearing the suspension struts is most important (and some other bits around there). Even felt a rubber-like hose behind the front wheel forward of the front axle. Everything feels like its going to be close.

There shouldn't be too much 'play' in all the bolted on parts so low tolerance for clearance should hopefully not cause me too much stress. I stress easy.