Some basic questions about tyre/Wheel sizes please

[Nigel L]

Having had the van for just a week now, am gradually getting part way up the learning curve
These might seem like basic questions on here, but have a limited knowledge of all things mechanical, but trying to get my head around it.
So, it’s a new T6.1 Startline with business pack added. I presumme that it would have left the factory with 16 inch wheels with 205/65/R16 tyres on?
The converters put on 20 inch wheels with 275/40/ZR20 106WXL tyres fitted.
my questions are.
1. looking at one of the tyre size sites, it says that the circumference is now 8-19% different to original size, and at 70, equates to 78.19.
is this acceptable, and
2. by putting different size wheels and different size profile tyres on, does the geometry need checking/adjusting
3. I am thinking about getting a 2nd set of wheels (16’s as original figment,) and getting a set of winter tyres to use through the sh&t weather, will it cause any issues by changing to different size wheels/tyres each year.
Any advice would be much appreciated, but please keep it in laymans term
Many thanks.

 

[Jlo]

Have you had a look here?

https://www.willtheyfit.com/index.php?width=205&aspect=65&diameter=16&wheelwidth=6.5&offset=56&width2=275&aspect2=40&wheel_size=20&wheel_width=9&offset2=20

 

[DaveD]

I'm no expert but there are a couple of previous posts with some members experiences and opinions:

275/40/20 V 275/35/20

Hi all, Yet another tyre question i know.........sorry. I have pretty much most of the threads post on here concerning all tyre and wheel sizes. Very informative and its educated me a lot, but would like some real world feed back from people who have actually fitted and run the above tyres and...

www.t6forum.com

275/40 or 245/45 on 20's

Tyre dilemma for 20-inch alloys Currently running OEM suspension on a T30 Kombi 275/40/20 seems to be the go to tyre for 20-inch alloys on the Transporter If I drop the suspension 40 or 50mm I may (or may not) get some tyre rubbing with the 275/40 If I go for 245/45 I'll probably avoid any...

www.t6forum.com

Although the search button is useful sometimes you are better to google T6 Forum 275/40/20.

Without wishing to appear rude, your first point makes no sense at all!

 

[Nigel L]

Have you had a look here?

https://www.willtheyfit.com/index.php?width=205&aspect=65&diameter=16&wheelwidth=6.5&offset=56&width2=275&aspect2=40&wheel_size=20&wheel_width=9&offset2=20

Yes, looked at a similar site, which is where I got the figures from.
My main issue is as to whether the Geo needs checking/adjusting etc and what possible disadvantages are there in running on bigger wheels.

 

[DaveD]

There is no way that 275/40/20 is anything like 19% bigger that the original equipment tyres!

 

[Markgf]

Mine left the factory with 16s. I now have 275/35 20s and at 60mph, my speed is the same as the speedo. Loads of people run the 40 profile, with no mention of them being 10 mph out. The Speedo is factory set, a couple of mph below actual speed. To check mine, I used Waze navigation, through your phone, to the apple car play. Set the cruise control, to 60mph, then on a nice flat road, see what speed you are actually doing. Waze has a speed reading in the top left of the screen.

 

[Nigel L]

There is no way that 275/40/20 is anything like 19% bigger that the original equipment tyres!

Sorry, that should be 8.19% (Dam decimal points)

 

[Mysticboer]

@Nigel L Definitely have a read of the various threads on here as there is a lot of really good information available on wheel sizes, impact on speedo readings and much more. To give you a quick indication however, I am running 20’ wheels with 275/40r20 tyres and my speedo reading is 1-2mph lower on the van than on the satnav at 70mph (less at lower speeds, which you will understand why)

 

[t0mb0]

Your speedo should be reading about 5% under at that size I think - comparing to my factory size of 235/55/17.

 

[Mysticboer]

Your speedo should be reading about 5% under at that size I think - comparing to my factory size of 235/55/17.

True, the only slight variance being the fact that speedo tend to over read as standard, which is why the difference ends up being smaller

 

[Mysticboer]

@Nigel L conscious that you asked three questions...I certainly am not an expert, so stand to be corrected, but I don’t think that switching between smaller and larger wheels, seasonally or otherwise, will cause any issues that you need to be concerned about. The biggest difference will be in ride quality, the look and Speed/mpg/mileage shown on the clock (all minor as discussed already). Perhaps one thing to keep in mind (and now I am really out of my depth) is that suspension changes/upgrades are often matched to wheel sizes (i.e. ‘stiffer’ dampeners for bigger and heavier wheels) which essentially translates as an impact on ride quality when changing wheels

PS I won’t be offended if corrected or keel hauled by the wheel and suspension Gurus for any poor advice dispensed...

 

[Markgf]

If you have a summer and winter set, your tyres will last twice as long

 

[BronzeBomber]

@Nigel L Definitely have a read of the various threads on here as there is a lot of really good information available on wheel sizes, impact on speedo readings and much more. To give you a quick indication however, I am running 20’ wheels with 275/40r20 tyres and my speedo reading is 1-2mph lower on the van than on the satnav at 70mph (less at lower speeds, which you will understand why)

Hi there new user here and new transporter 6.1 owner to….
I’ve got the factory wheels on still….17”
If I were to change to 20” does that affect anything like mpg ,wear and tear of enigine,gear box, steering etc thanks in advance