Changing from 19" to 18" rims

[92203]

Hello,

I own a 2018 Octavia VRS running on the 19" Extreme Alloys, fitted with 225/35/R19 tyres. I recently moved up to Lincolnshire and road maintenance here and in neighbouring counties leaves much to be desired. I don't think the recent cold spells have helped either, though it is a nuisance having to take longer routes to avoid minor roads which often have imperfections.

I have had to replace the front nearside tyre twice in the last year due to pothole damage (fortunately the wheels themselves are still in good condition). I understand that when ordered from new, it was possible to spec the car with 18" Gemini alloys instead of the 19" Extreme alloys fitted to mine

Would fitting the 18" Geminis and 225/40/R18 tyres significantly reduce the susceptibility to pothole damage, and is there anything I'd need to do to the car to compensate for the smaller wheel size, either mechanically, or to comply with insurance / legal requirements?

Although a higher profile (thicker) tyre would be fitted to the smaller Gemini wheels, the combined circumference would still be smaller than the wheel/tyre combination currently fitted. The speedometer would under-read very slightly as a result. I've fed the details into a tyresize calculator which has yielded the following results.

Any feedback will be greatly appreciated.

Thanks in advance.

Edited by 92203 on Thursday 19th January 20:48

Edited by 92203 on Thursday 19th January 20:49

Edited by 92203 on Thursday 19th January 20:58

[E63eeeeee...]

As long as you're getting wheels that are made for your car and fitting tyres the appropriate size (check the info panel for tyre pressures, that should list them if you're uncertain) you'll be fine as far as the speedo and safety goes.

In theory you should declare the change to your insurer, I suspect a lot of people fitting original-fit standard wheels to their car don't do this.

[RobXjcoupe]

A 225 40 profile won’t give any real improvement over potholes.
225 45 profile is possibly the better choice and with a 7.5j width wheel.
The speedo difference isn’t significant and it’s something I’ve read about so many times. That with insurance. If you have doubts keep everything standard.
Also I’ve no idea what size brakes are fitted to your car. That is an issue if you have big brakes with minimal wheel clearance.
Lastly if you drive the same route, remember where the potholes are and avoid them. Saves money on new wheels and damaging your existing wheels.

[dhutch]

My car came to me with staggered 18s, 225x40 and 255x35 and I changed them for sqaure 17s 225x45 and it made a significant difference. Both are standard sizes on the card on the door jam, I don't know which option the car left the factory with.

[E63eeeeee...]

Of course it will give you an improvement.

You're adding half an inch of sidewall, increasing it by approx 1/8 compared to what it is now.

I've recently gone from /35 R20s to /40 R19s. You notice the difference.

I wouldn't fit tyre sizes that Skoda didn't fit personally.

[Pica-Pica]

I went from 225/40x19” fronts with 255/35x19” rears (Pirelli Pzero), to:
225/45x18” fronts with 255/40x18” rears (Goodyear EfficientGrip)
Definitely a difference in ride comfort and protection against potholes and speed humps.
Both sets of tyres were runflats on aBMW 335d-xdrive.

The rolling circumference are similar enough. Incidentally, they are both acceptable as shown on the door jamb tyre label, but I did inform my insurer as they were not fitted ‘as built’. No change in premium.

See:
http://www.wheelcalc.com/

You will need to ensure the new wheel rims have the same offset (wheel centre to hub-mounting face distance) as before, and which will probably be different between front and rear, if you have a staggered wheel set.
If you have, or want to use run-flat tyres, you will need a particular rim seat profile (profile JJ, I believe).