Upgrading wheels and tyres mk6 golf118

[fully]

Hi there,

General questions and thoughts,
I'm planning on upgrading my mk6 118tsi golf from 16 inch to 18 inch wheels and tyres.
My car is stock height and I'm guessing the gap will look more noticeable with 18s so I was thinking of fitting 225-45-18 tyres for a tad more height and comfort. My speedo is already 6km off speed wise(actually speed is 94 when it shows 100), would that reduce it or make it worse? Thoughts??

Thanks.

[brad]

If you go to 225/40x18 then the gap will be a couple of mm less anyway (by measurement)

[fully]

I don't that is correct, 225/45/18 would reduce the space a tad more than 40s. Just wondering if there would be any problem with doing that??? Surely someone must know?

[The_Hawk]

There is this little tool that makes it easy to see what the differences are going to be with a particular tyre:

Tire size calculator

[Cookie28]

From what I understand (and this could be wrong) but when you go to a lower profile tire even though the actual diameter could be lower but the tires have less flex in them which will raise the height more

[brad]

I don't that is correct, 225/45/18 would reduce the space a tad more than 40s. Just wondering if there would be any problem with doing that??? Surely someone must know?

try this one too
Tire Size Calculator - tire & wheel plus sizing

Your stock tyre is 205/55x16 isn't it? Therefore it has a nominal diameter of 632mm

225/40x18 is ~5mm bigger in diameter

225/45x18 is 28mm bigger in diameter than the 16". From my experience, that will pop your speedo needle to the wrong side of 100. ie: at the moment when you are doing 100kph indicated you are probably doing about 92kmh. Around 655mm diameter will make 100=100; 659mm will make your actual speed faster than the indicated speed.

You realise that 18s will add between 5-10kg per corner & slow your acceleration, make it use more fuel & make the dampers work a bit harder?

[fully]

Thanks, yeah i guess 225/40/18 is the best fit...

As for using more fuel and stuff, yeah you're probably right, but i find the stock look (16s) pretty boring.

[dylan8]

fake and cheap 18s MAY add weight, stock wheels weigh stupid amounts as is.
Brad is right with the size though, 225/40/18 would be the best bet.
While the gap may be a touch smaller, it may visually appear bigger. and the car overall may/will most likely lift a little like cookie said due to less tyre sag compared to the 205/55/16s.

But yes, if you ran bigger tyres (225/45/18s) it will most likely make your speedo read correct. It also effects your gearing though, I found when running undersized tyres (smaller then stock) my car was quicker too 100km/h, but was so much slower accelerating past 100km, also found the car revs sat a lot higher at 100km/h, almost to the point i was uncomfortable with the amount for long distances at 110km/h.
your car will do the opposite id imagine, slower to 100km/h, revs will be lower then before (this could be good for fuel, but im sure VW wanted the car to rev at Xrpm when doing Xkm/h for a reason...)

[fully]

Thanks, yeah I'll stick to 225/40/18 when I do it, how much more fuel will it use and how much slower would it be? Now I'm having second thoughts.

[brad]

OEM 16x6.5 with 205/55x16 are about 17kg each. When I went to OEM 16x7.5 with wider tyres I gained 3kg per corner & economy was 0.5L/100km worse & acceleration/throttle response was dulled (& I have ~135kw/320Nm).

Lightweight 18s will be around 7.5kg but cheapies might be up around 12.5kg. The tyre will be around 9.5-11kg. So with careful selection, you might not gain any weight at all but if you go cheap & nasty then you might gain 5kg & lose up to 1L/100km

I don't think it's a show stopper, just something to keep in mind when you are choosing. If you don't do a lot of km then the fuel thing isn't a big deal but i do ~25,000km/yr so I have to be careful.

[dylan8]

Thanks, yeah I'll stick to 225/40/18 when I do it, how much more fuel will it use and how much slower would it be? Now I'm having second thoughts.

You may or may not even feel the difference, not like its a race car or something