Does changing to non- run flat tyres increase fuel economy
- Thread starter matt07
- Start date
centurion
Well-Known Member
Re: Does changing to non- run flat tyres increase fuel economy
In terms of fuel economy, reducing Rolling resistance is much more effective than reducing weight. Rolling resistance is really increased if you don't fill up your tyres properly, which is most people, and run flats have stiff sidewalls which prop up the tyre even if it is partially deflated or not enough air.
Initially RFTs had more rolling resistance than normal tyres, but recently because of OEM demands most notably from BMW, tyre manufacturers have improved the situation so much that RFTs now have LESS rolling resistance than normal tyres. Therefore, this RFT thing is one of the things which BMW uses to give themselves great EPA fuel economy ratings which is impossible to obtain without using RFT. If you replace a 335's stock RFT with, say, Michelin PS2, user anecdotes are that the fuel economy is poorer with the PS2 though that may be a consequences of inspired driving with the PS2 ..
Run flats are typically 20% heavier than normal tyres. This increase in unsprung weight makes a RFT car typically more uncomfortable than normal tyres as it makes the suspension lag. However, BMW has tuned their suspension to account for this lag for RFTs so on normal tyres typically new BMWs may not be as good as they could be. And obviously RFTs are not great for racing, though the new Nissan GTR on RFT has outperformed the Porsche Turbo and the GT3.
In case of a blowout, it's easier to control a RFT vehicle compared to one with a normal tyre. So this is a plus for safety.
And it is more expensive to replace a RFT compared to a normal tyre.
Bottom line is - if you want fuel economy, you can't go wrong with tyres optimized for rolling resistance reduction, like the Michelin Energy Michelin Energy
In terms of fuel economy, reducing Rolling resistance is much more effective than reducing weight. Rolling resistance is really increased if you don't fill up your tyres properly, which is most people, and run flats have stiff sidewalls which prop up the tyre even if it is partially deflated or not enough air.
Initially RFTs had more rolling resistance than normal tyres, but recently because of OEM demands most notably from BMW, tyre manufacturers have improved the situation so much that RFTs now have LESS rolling resistance than normal tyres. Therefore, this RFT thing is one of the things which BMW uses to give themselves great EPA fuel economy ratings which is impossible to obtain without using RFT. If you replace a 335's stock RFT with, say, Michelin PS2, user anecdotes are that the fuel economy is poorer with the PS2 though that may be a consequences of inspired driving with the PS2 ..
Run flats are typically 20% heavier than normal tyres. This increase in unsprung weight makes a RFT car typically more uncomfortable than normal tyres as it makes the suspension lag. However, BMW has tuned their suspension to account for this lag for RFTs so on normal tyres typically new BMWs may not be as good as they could be. And obviously RFTs are not great for racing, though the new Nissan GTR on RFT has outperformed the Porsche Turbo and the GT3.
In case of a blowout, it's easier to control a RFT vehicle compared to one with a normal tyre. So this is a plus for safety.
And it is more expensive to replace a RFT compared to a normal tyre.
Bottom line is - if you want fuel economy, you can't go wrong with tyres optimized for rolling resistance reduction, like the Michelin Energy Michelin Energy
acupunch
Well-Known Member
Re: Does changing to non- run flat tyres increase fuel economy
my question is how much Rolling resistance you need to reduce t o improve 1KM/L? for precise motor sport like F1, it make all sense..
for layman, FC = drivers + driving style. nothing got to do with size and weight of tires and rim.
why?
say your driving style between mild - aggressive type. e.g. my 320i consume 9KM/L average.I'm on 19" staggered. stock 16" I read its 12-11KM average on brochure. so that 2-3KM/L isn't significant to me. cos whenever I pump full tank, my OBC shows 690-710KM/L which our tank is a 60L tank of fuel. that works out similar 11.5KM/L on a full tank calculation.
so conclusion, the only excuse to change tires or rim. is for aesthetics and performance. FC jus way beyond to justify for the cost.
my question is how much Rolling resistance you need to reduce t o improve 1KM/L? for precise motor sport like F1, it make all sense..
for layman, FC = drivers + driving style. nothing got to do with size and weight of tires and rim.
why?
say your driving style between mild - aggressive type. e.g. my 320i consume 9KM/L average.I'm on 19" staggered. stock 16" I read its 12-11KM average on brochure. so that 2-3KM/L isn't significant to me. cos whenever I pump full tank, my OBC shows 690-710KM/L which our tank is a 60L tank of fuel. that works out similar 11.5KM/L on a full tank calculation.
so conclusion, the only excuse to change tires or rim. is for aesthetics and performance. FC jus way beyond to justify for the cost.
