Wheels again - What difference does width make?

[BigSouthernJesse]

Hi all,

Hoping for some assistance, and I believe I'm asking a new question... at least, my google searches haven't helped me yet.

I hace recently become the very happy owner of a 2016 T28 Highline Bluemotion Kombi. I knew the alloys on it were pretty dinged, and so expected to replace them at some point. I've also found the 20" size pretty harsh - looks nice cruising on the new roads, but feels pretty brutal in the Cornish lanes.

I'm looking for new wheels, and generally expecting those to be 18"s. And I'm currently going in circles trying to work out wheel width vs tyre size combos and availability!

Current set up:

Front- 20x8.5 ET40 with 245/40s
Rear - 20x10 ET42 with 275/35s

Using the Will They Fit website, I get circumferences of 2205 & 2197, or diameters 702 & 699. Basically the are a good pairing at the moment, and my speedo is pretty close - reading 72 against a GPS 70mph.

I see that standard recommendations for an 18" wheel are 235/50 or 255/45, or maybe 235/55 if you want something chunkier.
235/50 - circumference 2168
235/55 - circ 2246
255/45 - circ 2139
245/50 come out as 2201 - great match sizewise, but hard to find!

These are all on 8.5widths. I guess the 235/55 would be good as they will match the speedo pretty spot on. I wouldn't mind the slight improvement in the cruising gear either, though guess the tyre depth offsets the benefit of the overall larger diameter? Or just negligible...

But I also see that you can get 18" wheels in all sorts of widths, down to 6 or 7, up to 11... if they fit. So surely that changes the profile of the sidewall, either bulging out, fairly square or tapering in... And I guess this changes the diameter and rolling circumference too. (Plus handling, grip, shock absorption etc...)

So any guidance here re rim and tyre widths? Is there a suitable range?

Primarily I'm after comfort, safety and drivability I guess. (Not sure of the current suspension set up - I think standard, but will follow up with that if necessary. I need new rims, so making the size change first, and will improve/replace suspension if/when needed. I'm aware they are connected, but I'm not so set on 20's as to revamp all the suspension to try to manage the minimal sidewall)

Current shortlist of wheels is "anything bronzish / matt black in an 18" (She's that metallic deep brown with matt black side and roof bars, so think I can go either way on the wheel colour.)

Perhaps there's no question here, just need a bit of reassurance around importance of tyre and rim width matching, and a sense check on my thought process. Thanks to anyone if you can add or help to the waffle above! Cheers all

 

[ginkster]

18 x 8.5j with 255/45 is the standard VW fit. Good place to start.

 

[BigSouthernJesse]

18 x 8.5j with 255/45 is the standard VW fit. Good place to start.

Yeah, I can see that's one of the standards. But it's the fact it's 2.5% smaller than my current setup that makes me second guess it all. Do I go with the standard, or a match of the diameters I have now?

 

[ginkster]

Yeah, I can see that's one of the standards. But it's the fact it's 2.5% smaller than my current setup that makes me second guess it all. Do I go with the standard, or a match of the diameters I have now?

I’m on 255/45 18 and the speedo is spot on vs GPS if that’s what you are considering. Only vehicle I’ve ever had that is absolutely spot on.

 

[VWDAZ71]

My Caravelle has 8.5 x18 ET45 wheels with 235/55/18 Michelin CC’s and Speedo is spot on. Ride seems fine to me.

 

[BigSouthernJesse]

Thanks both, that's good to hear. I'm leaning toward the 235/55 I think.

Interesting that you both have a spot on speedo - the website shows 4.4% difference, or nearly 3mph difference at 60mph. Guess tyre pressure, wear, and speedometer variation makes up the difference?

 

[Kind of Blue]

Speedometers are usually set to over read by a small percentage and I think that by law cannot be more than 10% out however the can not under read. The French are in a process not sure how they have got on or weather they are trying to influence the rest of the EU and us to make dead accurate speed reading not a legal fitment an to force manufacturers to fit speedometers that over read so as said not sure what happened with that.

Wheel widths and tyre sizes. Each tyre has a recommended rim width and a range of widths that each tyre might have to be legally acceptable. So some rims might accept a few different widths of tyres but that their is an ideal width, a middle spot on, so to speak. If searching it is best not to use the word size but use a tyre and look for recommended rim width. Some tyre comparison sites might have information but information is out their.