Volkswagen Golf 2.0TDI 2011 - Are my wheels sticking out too much? | Technical matters | Back Room Forum

Thu 18 Feb 2021 19:00

Volkswagen Golf 2.0TDI 2011 - Are my wheels sticking out too much? - Diesel Lamp

So I hit a kerb some time ago, the wheel alloys are buckled so the garage said I have to change them.

They said there's a 8Jx18 option available for the car, and apparently it's for the Golf GTD so I thought it must be better..

Previously it's on 17 inch wheels, I also changed my tyres of course.

Now, I'm having about 20% worse MPG...!!!

I have checked the wheel alignment in a professional shop with lasers and stuff, and checked all the brakes, they are not dragging. The MPG drop happened precisely after the wheel change, and I calculate using the pump figures and odometer, not the trip computer. Also I compared the odometer to a GPS route tracker, it's spot on, so it's not the increased wheel size messing with the mileage.

How would a wheel size change affect MPG this much?? The only reason I can think of is they are sticking out of the car fender too much, causing wind drag, but that won't be 20% right?? Here's a video, are they sticking out too much?

youtu.be/iUpiEXaj5-8

Before I have 4.8L/100km, now it's about 5.9L/100km, that's just too much.

How can I fix this?? Other than changing the alloys again, don't have the money.

Please help!!!! Thanks.

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Thu 18 Feb 2021 20:30

Volkswagen Golf 2.0TDI 2011 - Are my wheels sticking out too much? - medview

Are you sure that the degraded MPG is not simply due to the cold weather or shorter journeys?

Sunday looks like a good day for a test run, it will nearly be warm!

Even if the rolling resistance of the new tyres increased it would not account for -20% MPG

Generally new tyres start with less rolling resistance until the wear-in.

One more thought: If the kerb damage increased the toe-in this would increase the rolling resistance but again it probably wouldn't account for 20% change.

Joe

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Thu 18 Feb 2021 20:36

Volkswagen Golf 2.0TDI 2011 - Are my wheels sticking out too much? - Diesel Lamp

No I did identical motorway runs, fueled up, and calculated using the pump numbers.

I know the tyres will not account for the 20% increase! That's why I'm asking!!

As I said, I changed the wheel alloys, and I suspect they are the reason, larger wheels are heavier, and apparently they are wider so they stick out more, increasing wind resistance.

Even that I don't think it would be 20%, so something must be wrong.

The alignment is fine, I checked it in shop, they did laser guided check.

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Thu 18 Feb 2021 20:37

Volkswagen Golf 2.0TDI 2011 - Are my wheels sticking out too much? - mcb100

You’ve increased the weight of the vehicle by adding bigger wheels and tyres, and increased the rolling resistance by enlarging the contact patch between tyre and road, making the car more ‘draggy’.
The tyres also don’t have to stick out to add air resistance as airflow doesn’t just go down the sides of the car, it also goes underneath. In addition, the new wheel/tyre combo have increased the frontal area of the car.
I’ve no idea whether that will add up to anywhere near 20%, but you’ve added a few incremental factors in decreased fuel consumption.

Edited by mcb100 on 18/02/2021 at 20:38

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Thu 18 Feb 2021 20:43

Volkswagen Golf 2.0TDI 2011 - Are my wheels sticking out too much? - Diesel Lamp

The only other thing that's changed is I did a engine oil flush, if that's the reason... I guess I'm doomed anyway, so I don't want to face that harsh reality.

The increase in consumption happened after the wheel alloy change, the tyre change, the brake rotor and caliper change. The brakes are checked twice by professionals, and they confirmed that it's not dragging, so must be the tyres or wheels.

Is there any way I can fix this...

Edited by Diesel Lamp on 18/02/2021 at 21:59

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Thu 18 Feb 2021 22:46

Volkswagen Golf 2.0TDI 2011 - Are my wheels sticking out too much? - bathtub tom

What size were your original tyres and what size are you on now?

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Fri 19 Feb 2021 00:32

Volkswagen Golf 2.0TDI 2011 - Are my wheels sticking out too much? - Diesel Lamp

Bought the car second hand, so don't know about the original, searched online says it's supposed to have a 15 inch wheel.

For me, it had a 7.5Jx17 wheel before, now I think it's a 8Jx18, 225 40 R18 tyre.

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Thu 18 Feb 2021 23:18

Volkswagen Golf 2.0TDI 2011 - Are my wheels sticking out too much? - Andrew-T

You are checking the quantity of fuel. Have you checked that the odometer is recording the same distances as before ? The figures basically count the wheel revolutions - but I wouldn't imagine you could make your wheels 20% bigger within the clearances of the car ....

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Fri 19 Feb 2021 00:34

Volkswagen Golf 2.0TDI 2011 - Are my wheels sticking out too much? - Diesel Lamp

Don't know about before but the odometer is spot on, checked using GPS tracking.

The actual diameter of the tyre is the same I think, because the speedometer behaves the same as before, compared to a GPS speedo.

Yeah, so the 20% increase in consumption is even more confusing.

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