Help Decoding Rim Sizing Details

[Baldchap]

I'm looking for some winter wheels and tyres for the wife's 2021 Up GTI. The standard size doesn't give many/any options, so the winters will need to be smaller.

I fancy some nice Oz wheels or similar, but having never really played with wheels beyond direct like-for-like swaps, I'm not 100% sure what the best size to go for is and how to decode the wheel information.

Obviously the stud pattern has to match, but I'm struggling to get my head around the rim sizing details.

Example:

Standard wheel takes a 195/40/17 tyre, and the rim is 6.5Jx17 ET43

6.5J is presumably 6.5 inches wide, but 195mm is 7.6 inches, so this doesn't make sense to me. There isn't an inch difference between the tyre and the rim widths, so I don't quite get this. No idea what the J is or the ET. 43 I believe is the offset, although with a different wheel, should this remain the same or not?

To my eye the stud pattern isn't mentioned at all here either (unless that's the J).

Anyone aware of an idiot's guide? Last thing I want to do is balls up the geometry of the car.

Thanks.

[sixor8]

Yes 6.5 is the wheel width but it is the internal distance between the rims across where the tyre sits, not the external. Unless you want the stretched look, the tyre width needs to exceed this, which it does.

There's a guide on Halfords website to tyres:

https://www.halfords.com/tyres/how-to-guides/tyre-...

The J is the wheel lip / tyre profile:

https://www.tyreleader.co.uk/tyres-advices/wheel-m...

ET is indeed the offset, a couple of mm either way won't matter too much, unless you're putting on wider tyres. More here:

https://en.wikipedia.org/wiki/Wheel_sizing

The Pitch circle Diameter (PCD) is the stud pattern and some after-market wheels have 8 bolts holes to allow for 2 different sizes (usually 4 x 100 and another).

This is a guide I've used but may not be 100% accurate, you can check by car make or required PCD:

https://www.wheelfitment.eu/car.html

Unless you know what you're doing, be careful if changing tyre widths and sizes because you may foul the inner components or the wheel arch.

[Alex@POD]

Rim width is measured where the tyre bead sits, so your 1" difference sounds OK to me. Your best bet is to have a look at a website like willtheyfit.com, that allows you to play with different sizes and gives you a visual representation of how the changes will look.

The ET is the distance from the mounting face of the wheel to the centreline, the smaller the number the more the wheel will poke out.

The PCD needs to match as you said, but also the centre bore (though you can get adapters), and the wheel bolts/nuts need to have the correct profile for the wheel.

It's all very straight forward once you have your head around it, but if you're going to buy new alloy wheels it's likely a decent supplier will be able to telly ou what fits and what doesn't.

[Mr Pointy]

This is a very useful site which tells you a lot about the wheels & tyres specified by the manufacturers:
https://www.wheel-size.com/size/volkswagen/up/2021...

For your Up! GTI



This site will show you the effect of changing tyre & rim sizes
https://www.willtheyfit.com/index.php?

Finally you might want to consider if you need to tell your insurance company if you are fitting non-OEM sizes.

[Baldchap]

Thanks so much all, I'll take a look later.