I have 18” Gemini wheels atm but want to get 18” xtremes as far as I can see the 18” xtremes are 8” wide the Gemini’s are 7.5” wide my question is will my tyres be ok just to swap over to the xtremes? Tyre size in Gemini’s are 225/40/18 please any advice before I rethink I don’t really want to have to go for 19’s

1 hour ago, TQVRS said:

Tyre size in Gemini’s are 225/40/18

Gives rim width with extremes at a shade under 83% of tyre width; you're fine.

1 hour ago, TQVRS said:

I have 18” Gemini wheels atm but want to get 18” xtremes as far as I can see the 18” xtremes are 8” wide the Gemini’s are 7.5” wide my question is will my tyres be ok just to swap over to the xtremes? Tyre size in Gemini’s are 225/40/18 please any advice before I rethink I don’t really want to have to go for 19’s

 

I haven't seen any 18" xtremes, only 19" xtremes (and 20" xtremes on the Kodiaq).

 

18" is hardly extreme.

 

Have you got a link or further information such as an OEM part number?

 

Here's a link to a Skoda online parts catalogue

https://skoda.7zap.com/en/cz/octavia/oct/2016-753/6/601-601080/

 

There's no 8Jx18 alloy rims shown there (only 7.5Jx18).

 

7.5Jx19 ET51 X-TREM alloy rims

https://eshop.skoda-auto.cz/cs_CZ/kolo-z-lehke-slitiny-x-trem-19-pro-octavia-iii-rs/p/5E0071499++HA7

 

Edited 29 December, 20214 yr by Carlston

>>>>> This is what I work off. From a tyre site. <<<<<<

 

Image removed so people don't use it. See below for issues with it. 

 

The correct Tyre/Rim combos is in the link is below.

 

 

 

Edited 17 February, 20224 yr by Legion
Image removed so people don't use it.

10 hours ago, Legion said:

This is what I work off. From a tyre site.

 

 

That table is completely wrong.

 

Rim width doesn't just depend on tyre width, but also on the aspect ratio.

 

Approved Rim Widths for 205 Tyre Sizes

205/70

5.0-6-7.0

https://www.toyo.co.uk/tirefinder/index/width/205/aspect/70/rim/15

 

205/65

5.5-6-7.5

https://www.toyo.co.uk/tirefinder/index/width/205/aspect/65/rim/15

 

205/60

5.5-6-7.5

https://www.toyo.co.uk/tirefinder/index/width/205/aspect/60/rim/16

 

205/55

5.5-6.5-7.5

https://www.toyo.co.uk/tirefinder/index/width/205/aspect/55/rim/17

 

205/50

5.5-6.5-7.5

https://www.toyo.co.uk/tirefinder/index/width/205/aspect/50/rim/17

 

205/45

6.5-7-7.5

https://www.toyo.co.uk/tirefinder/index/width/205/aspect/45/rim/17

 

205/40

7.0-7.5-8.0

https://www.toyo.co.uk/tirefinder/index/width/205/aspect/40/rim/17

 

As you can see in the chart above, 205/50 to 205/65 tyres have the same minimum rim width, and the maximum rim width for 205/70 tyres is the minimum rim width for 205/40 tyres.

 

The Skoda Karoq has 215/60 and 225/60 tyres fitted to 6J rims. Your chart incorrectly says that you can't fit anything wider than a 205 tyre to a 6J rim.

 

The Skoda Kodiaq has 235/55 tyres fitted to 7J rims. Your chart incorrectly says that you can't fit anything wider than a 225 tyre to a 7J rim.

 

Edited 17 February, 20224 yr by Carlston

I have 185 tyres fitted to 4.5" wide rims on three trailers, I fitted them myself manually and was expecting a struggle but they slid on like a slippery stick up a dogs jacksie.

 

Why does rim width also depend on aspect ratio? I'm not disputing it but would like to understand why.

1 hour ago, J.R. said:

Why does rim width also depend on aspect ratio? I'm not disputing it but would like to understand why.

 

The tread width gets wider as the aspect ratio gets lower for any given tyre width.

 

For example, 205/40 has a much wider tread width than 205/70.

 

So to support this wider tread, the range of rim width needs to be wider.

 

Tread width is not the same as tyre width.

 

Edited 17 February, 20224 yr by Carlston

1 hour ago, J.R. said:

I have 185 tyres fitted to 4.5" wide rims on three trailers.

 

185/70 has an approved minimum rim width of 4.5J.

 

185/50 to 185/65 have an approved minimum rim width of 5J.

On one of my cars I swapped the tyres from a 155 80 13 tyre to a 175 70 13 tyre on the same 5J wide rim.

 

The tread width on the 155 tyre was about 105 mm.

The tread width on the 175 tyre was about 135 mm.

So a 20 mm wider tyre but with an increase of 30 mm in tread width.

 

Thanks, AG Falco

 

OK, did a bit of hunting. I couldn't find a current Australian Tire and Rim Assoc Manual but below is a 2016 ETRTO extract for passenger vehicles.

 

ETRTO-2016-Approved-Rims.pdf 

 

Have fun. 👍

Edited 17 February, 20224 yr by Legion

Have you considered Golus alloys? They are the same spec as Geminis?