18” wheels - tyre size options

Daved-and-Confused · Post by **Daved-and-Confused** » Tue Sep 14, 2021 9:08 pm

My van is on 18” Interlagos alloys running 235/40x18 tyres, it’s also quite low and it’s starting to grate on me a bit.
I’m looking at raising it and also fitting taller tyres as the local roads I use are pretty rough and going to the local dump, speed humps etc can be a pain.
Is anyone running 235/45x18 or even 235/50x18 tyres and standard or slightly lowered ?
Any comments, experiences or pictures would be appreciated.
Cheers

Macsfam · Post by **Macsfam** » Tue Sep 14, 2021 9:12 pm

Correct size is 225/40/18 , changing to higher profile will knock speedo out

Daved-and-Confused · Post by **Daved-and-Confused** » Tue Sep 14, 2021 9:36 pm

Correct size for what - a caddy? Don’t think any caddy came with 18” wheels.

Anyway…….

the swan fiend · Post by **the swan fiend** » Wed Sep 15, 2021 5:14 am

I think what macsfam is referring to is the overall circumference of the wheel. 225/40/18 is nearly identical to 195/65/15.

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Guy94 · Post by **Guy94** » Wed Sep 15, 2021 9:20 am

To note, if you aren’t running too low and want larger profile tyres, you can get the speedo adjusted I think to read correct speed.

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makzimum · Post by **makzimum** » Wed Sep 15, 2021 10:47 am

I'm not an expert, but I have been doing a lot of research into this recently as I'm just about to change to a smaller wheel and taller tyre.

Speedo wise, I believe for a lot of people it under reads on the standard wheel diameter (Which is approx 632mm I think) and when putting a wheel with a slightly larger diameter it actually reads more true. That's the case for me with 235/35R19 - it's pretty much dead on now and my wheel diameter is 647mm.

235/45R18 will give you 668mm. Judging by how much room I have left on my current setup I'd say that might just fit, but I wouldn't be sure, I think it'll be very tight. 235/50R18 is 692mm which I'm fairly sure won't fit. I've seen people on here running all terrain tyres at 215/65R16 which is 685mm but that's a narrower tyre and I'm not sure how the speedo reads going up to this size.

Again, not an expert, but hopefully that's helpful.

Lots of calculators available at tiresize.com and https://www.willtheyfit.com/

Poffe · Post by **Poffe** » Sun Nov 26, 2023 5:49 pm

Tinking of buying 235/45r18 used from a Passat, Et 44. Rim width 8”.
Will it fit? Or be too close?

Poffe · Post by **Poffe** » Tue Nov 28, 2023 12:43 pm

Bought the wheels and test fitted them! Super close to the wheel arch with full steering range. Less than 8mm to spare. But it works!!

So, in conclusion, 18 inch in diameter and 8 inch wide rims, together with 235/45/R18 tyres do fit on a Caddy MK3 (-2014) with standard suspension.

pomidor · Post by **pomidor** » Wed Dec 04, 2024 9:55 am

Hi,
I’m digging through different threads to learn as much as I can about possible wheel tire options and I’ve stumbled across this one.

Based on the findings here does it mean that 235/40/19 should work? I know most popular variant is 235/35 but I’m still tempted. According to some calculators 225/40/19 would be smaller in diameter than 235 and should be even smaller than 235/45/18. I’m curious is that true? Does anybody have any experience with those combinations?

Thanks in advance

Poffe · Post by **Poffe** » Fri Dec 06, 2024 8:04 am

I havent tested 235/40/R19, but as above I run on 235/45/R18. Mine are roughly 10mm from rubbing the wheel house at full steering angle.
235/40/R19 have a slightly bigger diameter and circumferance, 3-4mm. In theory, it might work. Will be close though, so the ET of the rim will play a factor here as well.

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