Deker 3,478 Posted January 14, 2016 Report Share Posted January 14, 2016 Car brochure printed figures ENGINE OUTPUT (PS)TORQUE (NM)CO2* (G/KM)FUEL CONSUMPTION* (MPG)dci 130 diesel 2WD MT 130 320 129 (133 with 19") 57.6 (55.4 with 19") dCi 130 diesel 2WD Xtronic 130 320 135 (139 with 19") 55.4 (53.3 with 19") dCi 130 diesel 4 WD MT 130 320 139 (143 with 19") 53.3 (52.3 with 19") DIG-T 163 2WD MT 163 240 145 (149 with 19") 45.6 (44.1 with 19") I have not seen published figures like these before, if you can fathom your way through them, it says emissions and fuel consumption are worse simply by fitting larger wheels (19") as opposed to the normal 17". Yet engine output and torque remain the same. What have I missed here, the overall size remains very similar if I'm not mistaken as the rubber is less on the bigger rim?! Can someone explain please? Many thanks. Quote Link to post Share on other sites
Born Hunter 17,779 Posted January 14, 2016 Report Share Posted January 14, 2016 (edited) Is it to do with unsuspended weight? Heavier wheels being less energy efficient I think, even if the rolling circumference is the same I believe.... Just a theory, might be a mile off. Be interesting to find out the truth. Edited January 14, 2016 by Born Hunter Quote Link to post Share on other sites
neil82 1,080 Posted January 14, 2016 Report Share Posted January 14, 2016 could be as simple as the point that alloy wheels are bloody heavy, plus if they are fitted with wider tyres there is more rolling resistance, the differences are only small so my money is on rolling resistance Quote Link to post Share on other sites
walshie 2,804 Posted January 14, 2016 Report Share Posted January 14, 2016 I've thought this in the past. My take on it is when changing wheels and tyres, although the larger wheel has a lower profile tyre to keep the overall diameter similar, they aren't the same. I think the maximum permissible difference is 15mm or so. As the sidewalls are always a percentage of the tread width, and the percentages are always round figures ;like 55, 60,. 65 and so on it's hard to get an exact match. That and the fact bigger wheels are heavier. Quote Link to post Share on other sites
Deker 3,478 Posted January 16, 2016 Author Report Share Posted January 16, 2016 Thanks all, still not sure I've got my head round this one though. Quote Link to post Share on other sites
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