I was just reading the HJ road test of the i10, and the following caught my eye:
"It?s a shame the sunroof and alloys pull the Style model over the CO2 limit, but hardly surprising that the proper 4-speed torque converter automatic does."
www.honestjohn.co.uk/road_tests/index.htm?id=313
Do alloy wheels and sunroofs really have a negative effect on CO2/MPG?
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Sunroofs cause drag and reduce MPG/increase emisions. Only very slightly but if 5 million cars had their sunroofs open all the time I am sure it adds up. No idea in the slightest how Alloys add to C02?
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Nothing to do with drag, it's all down to weight. Start adding options, it adds weight and this affects emissions.
Audi brochures actually give you the weight of all the options and warns adding them could change tax bands.
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Great so we are now going to go back to having cars with slide down manual windows and bodies made out of Duraplast to keep the weight down?
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Great so we are now going to go back to having cars with slide down manual windows and bodies made out of Duraplast to keep the weight down?
I used to know a car dealer who specialised in unusual cars. One I remember well was called "swifty", it was an original mini with rather extensive weight reduction mods. Holes drilled everywhere, steel panels replaced with alloy, glass replaced with acrylic. Apparently it went like pink fluffy dice off a shovel.
Maybe this could be the latest boy racer/trendy mod - "hey guys, check out my performance manual window winder" :)
Edited by Dynamic Dave on 01/07/2009 at 01:23
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The drag coefficient on the Calibra was lower on the 2.0 8v version than the 16v because of the width of tyre. More aero-dynamic cars emit less CO 2 .
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The manufacturers fit narrower, higher-profile tyres to their 'green' models.
If you bought one and fitted alloys to it, would you then have to inform the DVLA as well as your insurance company?
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I don't follow the weight argument. Alloys either weigh the same as steel wheels, or are lighter. They certainly aren't heavier.
My sunroof consists of a piece of glass. Is that really significantly heavier than the steel it replaces - enough to send the car into a higher tax band?
Surely the real comparison ought to be between the energy used in manufacturing the glass and the alloys and the steel they substitute for. Doesn't aluminium use a lot of electricity to smelt?
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Alloys either weigh the same as steel wheels, or are lighter. >> My sunroof consists of a piece of glass. Is that really significantly heavier than the steel it replaces >>
Cliff Pope:
Your questions can be answered by a visit to your Hyundai dealer.
1. compare the size and weight of standard 14" steel wheels on the basic model against the 15" alloy wheels on the style model.
2. compare the standard model with steel roof against the Style model which has "Electric internally sliding glass sunroof".
Then see whether HJ and the specification "Kerb weight: 925kg (Classic) to 1,008kg (Style)" are wrong, or you are right.
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>> Then see whether HJ and the specification "Kerb weight: 925kg (Classic) to 1 008kg (Style)" are wrong or you are right.
You are not comparing like with like. Obviously bigger wheels weigh more. So would bigger steel wheels. That's not answering the question.
Also presumably there are other differences between the Classic and the Style versions, not just wheels and sunroof?
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You are not comparing like with like >>
I am not comparing anything. I am pointing you to HJ and Hyundai's spec which says that the Style weighs 1008kg whereas the Classic weighs 925kg. HJ states in his test report that "It?s a shame the sunroof and alloys pull the Style model over the CO2 limit".
You either
1. ask HJ [via letters@HJ] and/or Hyundai to explain where the extra weight comes from or
2. visit your Hyundai dealer to check whether just the alloy wheels and sunroof add enough weight by the margin required to push the Style over the CO2 limit.
Get the facts if you are concerned enough about the claim made by HJ, and then debate can then be over.
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The original question was:
"Do alloy wheels and sunroofs really have a negative effect on CO2/MPG?"
That is a different question from "Does a higher spec car having a sun roof and alloy wheels have a negative effect on CO2/MPG?"
Both are interesting questions - I was addressing the first, as posted.
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If you bought one and fitted alloys to it, would you then have to inform the DVLA as well as your insurance company? >>
The DVLA don't care if you run your car filled with junk or cement bags [within the load specifications].
Your insurance company will most probably care if/when you have to make a claim.
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Alloys -
Wider tyres, more rolling resistance and air drag
Extra weight - up for debate if heavier/lighter than steel
sunroof -
extra weight
extra drag due to imperfect seals on roofline
I have to admit that I would thought the effect of these to be minimal, maybe not the case. Personally, I've never liked sunroofs anyway (too much noise and hot in the summer).
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If we are talking about CO2 emissions from the point of view of the taxation class, then I don't think wind resistance makes any difference. Isn't the car tested on a rolling road? If so, a billboard on the roof would make no difference.
Manufacturers go to great lengths to reduce drag to get real world comsumption down but does it affect the government test?
Edited by nick on 01/07/2009 at 11:20
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>>Isn't the car tested on a rolling road?
Yes, but, the rolling road simulates the aerodynamic drag of the vehicle as measured in a seperate test. So, a billboard on the roof would make a huge difference.
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>> If you bought one and fitted alloys to it would you then have to inform the DVLA as well as your insurance company? >> The DVLA don't care if you run your car filled with junk or cement bags [within the load specifications]. Your insurance company will most probably care if/when you have to make a claim.
Even if the new wheels are putting you into a higher CO2 band?
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I would have thought alloy wheels were lighter than ordinary steel wheels.
But ...
The alloy wheels are wider than equivalent wheels so there is more tyre on the road surface.
Also possibly higher emissions because of the larger diameter alloy wheels ?
Just get spinners on the normal steel wheels so the car looks all 'bling'd up' and still does not push the emissions up into the next bracket.
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>>I would have thought alloy wheels were lighter than ordinary steel wheels.
As often as not, the alloys are heavier than a steel wheel.
Racing spec, expensive, alloys would be lighter, but, these are completely different from most standard fit alloys.
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Im not sure if they are still in business, but Burtons racing on the A12 used have an old F1 wheel in use as a doorstop. It looked heavy, but when picked up was surprisingly light for its size, much lighter than a standard alloy wheel.
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Agreed, alloys will generally be heavier than a steel wheel of the same size although, as you say, proper magnesium alloy wheels will be lighter as well as several times the cost.
Incidently, the worst of all worlds is the wire wheel. Heavy, flexible, expensive and a pain to clean.
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Even if the new wheels are putting you into a higher CO2 band? >>
DVLA would need to set up a system of measuring your CO2 emissions in real time if your concept of VED banding was to be implemented.
As with most Govt schemes, they are only concerned about theoretical " as manufactured and supplied" figures. For example, they stipulate the energy efficiency of windows but there is nothing [apart from the energy cost] to stop you keeping your windows fully open with the heating and/or air-conditioning blasting away at full force.
Similarly, there is nothing to stop you driving around in third or fourth gear on the M-Way when 5th or 6th would be better all round.
CO2 ratings, like may other regs, get fixed and stay fixed. There are thousands of examples in the Finance and Tax regulations, and here is just one:
When money laundering regs were drawn up yonks ago, the limit for cash deals was set at £9,000 [=Euro15,000 at the time]. Now many years later, the same limit still applies despite currency Euro/£ values and inflation taking a toll. Bureaucrats cannot think in real time and adapt with changing times, once they have set a limit, it stays fixed.
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Are you suggesting that bureacrats think?
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