Dougie, your observations that the gear ratio change affectively increasing mileage at highway speed is correct. But the more significant factor is the change in aerodynamics caused by the increase in frontal area caused by raising the car by almost 1 inch. By raising the car more frontal area of the front and rear tires are in the direct high speed air flow. And by raising the car more air will travel under the car instead of over the smooth body so air drag will increase. http://www.tfd.chalmers.se/~lelo/rvad/reports/rva2002_gr11_contribution-to-drag.pdfDougie said:I agree that running such big tires is risky. But I don't agree that it will damage the fuel economy. The percentage difference is pretty small--certainly a lot less than the difference between 4th and 5th gear. And it decreases the gear ratio, so on the highway it will probably cause a slight improvement in economy, sort of like shifting into 5.1th gear.
I remember way back when Michelin first "claimed" a higher silica formula in their tires. Toll booth operators _hated_ them. The reformulation allowed a static charge to build-up and they would get a painful zap when driver's paid the toll. The re-re formulation also required a higher % of carbon-black.ghillie said:1. Anyone know anything about the use of silica compounds in tyres - is Michelin just talking a lot of BS?
1. Most if not all quality tires include silica compounds some more then others. I've read marketing material that states it "improves grip on wet roads". But marketing loves to grab a key cool sounding tire ingredient that's not top secret and use it in marketing. The art and science of manufacturing of tires is one of the most highly guarded secrets in the automobile industry. Try to get a tour of tire plant... good luck. I would not take the marketing literature about tires too seriously because they reveal very little info that could be useful for comparing different brands of tires of the same category.ghillie said:1. Anyone know anything about the use of silica compounds in tyres - is Michelin just talking a lot of BS?
2. My preference is for the 175/60 because they are closest circumference to the OEM tyres and do not raise the ride height (keeping in mind Guillermo's comment above) - but would the 185/60's be better handling?
I would suggest to abandon the all season tire and all it's compromises and try this high peformance summer only tire with low rolling resistance and the same aerodynamic size of the OEM tires.ghillie said:I want to use the Michelins to improve handling (especially in wet weather) without sacrificing fuel economy.
The tyre features three prominent main grooves, and lateral grooves open to the side, giving the tyre excellent hydroplaning properties.
I love this part:The ecological nature of the Nokian i3 is particularly evident in two features. Similar to other Nokian tyres, no high aromatic oils are used in the manufacturing process. The tyre is also economical: it rolls easily and consumes little fuel.
A summer tire that brags that is still provides grip at temperatures below 50 F. Imagine how much more grip it has at 80F :lol:The tyre maintains its grip properties in cold spring mornings and in the cool early autumn, even when temperatures drop below 10 degrees centigrade.
In order to prevent this tire post from going off-topic I have started a new topic about tramlining in the modifications sections:ghillie said:I also want to minimize the "tramlining" effect.
Yes but in warmer weather this Nokian summer tire would be significantly better then any all season tire, rain or shine.ghillie said:A tyre that works below 10 degrees C is pretty much all season where I live. Unfortunately I don't think Nokians for cars are available in Australia but I will do some more searching.