A long time a go, I owned a Mercury Lynx. It got decent mileage which improved over time. But when I replaced worn tires, the mileage got worse immediately. Here's a website explaining that old tires give better mileage.
I'm considering changing from 265/75-16 to 235/85-16, which are narrower. This meant there will be less tread to deform and use fuel. However, will less tread deform more, ofsetting the FE gain??? In other words, will the narrow tread contibute little to LRR?
Capitalism: The cream rises. Socialism: The scum rises.
If we're not talking about some kind of truck that needs a huge tire to bear the weight, switching to a narrower tire should be an improvement. The most efficient cars in the world use very narrow tires, though they are incredibly light. Just go with a good LRR tire (Michelin Energy MXV4+ are great) and you will be in good shape after a couple thousand miles to let them wear in.
"We haven't been able to translate low rolling resistance into huge fuel savings," Weekes said."
Yup. That's why we still see high strung transmissions, huge engines, etc... The trade offs needed to get what's perceived as huge fuel savings are way too high for the average consumer. Not only that, but for most gasoline vehicles, making them more efficient makes the engine less efficient, so it's a few steps forward, a couple back. Unlike diesels or EVs which exhibit a pretty linear increase in efficiency, or lead acid powered EVs, which exhibit an even greater increase in efficiency due to Puekert's law.
Originally Posted by FormulaTwo
I think if i could get that type of FE i would have no problem driving a dildo shaped car.
This is as good a time as any to comment on tires and rolling resistance. Like many, I always figured a skinny tire at high pressure would automatically roll easier than a fatter one at lower pressure. This is not necessarily true and so unless you have some empirical evidence to back it up it may not be a good blanket statement to make. I think the people most tuned in to tire rolling resistance in the world today are the bicycle/human powered vehicle guys, and the super high mileage and solar competition car guys. So this doesn't get too long, here are a few links:
... so many links, so little time!!!! ...
Hopefully the hours and hours I've spent digging all this up bears fruit for us!
Oh cmon teacher, that's so much homework !!!!! What does it all mean ?!?!?!?! Now what do I do ?
Well where snow and bicycles are concerned, I was shown looong ago that those wide beach/"mountain" tires have a much harder time cutting through a couple inches of snow than a thin 10 speed tire.
But generally speaking, the narrower the tire:
the less wind resistance,
the more stiffer sidewalls help lrr,
the more even the tread wear,
the less snow/mud/water (or baby innards if you are toecutter) they have to displace.
Yeah, I feel your pain. I was all hot to try putting motorcycle tires on my car- skinny, high pressure, yada yada... but would they improve anything? What things would be made worse? Only testing would reveal that I suppose. I'm not aware of any formulas for predicting this sort of thing.
What it means to me is, a heavier wider-than-stock tire is likely not the way to go. But a skinnier than stock tire may or may not help either. More importantly, it means I shouldn't get my hopes up thinking that 60 psi or 70 psi is going to make a material difference in rolling resistance vs. 50 or 40.
I have to read all those posts in detail, but I think this is something that could lead to the overall idea of a general database in GasSavers for drivetrain/mods that work for members.
For example, I would like to be able to see all of the tires on all of the Saturns in order to be able to make an informed judgement. One stop shopping for tires and other mods, so to speak.
This would (obviously) all be voluntary input.
Maybe what I really want is alot of input entries in the Garage that are not required input, but available for the GasSaver to input. This could be akin to 2 modes. The "basic Garage" is the variable data that is already seen in the Garage. The same car could also have an "Advanced Garage" input form that has all sorts of gruesome details regarding tires, their PSI, and their perceived benefit/detraction to FE.
Also it means that special lrr tires do come at a cost and certain other characteristics are compromised. Maybe the best thing is to run on nearly bald worn out old tires.
That sounds like skinny F1 tires.
Maybe a used-tire co-op would be in order. The co-op would start with a same make/model set of 4 tires with unequal tread wear. The co-op would "true" them to be the same. Arghhhhh, too much effort. I don't want to even think about going that route. Orrrr, do used tire shops already exist????
My pre-GasSaver brainpan is trained to want to buy "really good safe tires" that are rated for alot of miles. But in the gas-saving world, that's alot of sunken-cost that you are stuck with until the tires reach, what, maybe 1/2 way into their tread life? If the tires are dogs, then you are stuck with them for 40K+ miles.
My Gas-Saver tire formula currently juggles these variables ranked in order of importance :
1 - PSI : Shoot for 50+ in order to be able to experiment safely.
2 - Rolling Resistance : Low as possible but still safe. In LA a super-grip tire is not needed because of all the sunny dry days we have.
3 - Size : At or above OEM spec. A larger tire should not be a wider tire.
4 - Weight : Lower than OEM.
5 - Tread Life : leaning toward low in order to mitigate "dog tire" syndrome.
6 - Price : Leaning toward < $70 per tire.
But maybe this is stating the obvious ?!?!?
Re: skewbe 10 speed tires cutting through snow: that is a truth in the north country, that skinny snow tires will outperform fat ones. The skinny ones "cut" down through to where there is better traction and the fat ones float and slide around on top- one reason why an old VW with it's super-skinny tires can embarrass a fancy-pants 4x4 with big tires.
There are used tire stores. I have gotten many many tires from the local metal scrap yard where people drop off their cars for crushing. Tires are a disposal problem for those guys so they are generally glad to be rid of them. I just bought new shoes for my pickup but I've been running half worn out old used tires on my cars for years. In fact the last time I bought new tires for a car was 1991!
I've never bought used tires. I used to get a new set from Winston Tires (now bankrupt) for my Dad's Ghia that I drove, and generally have gone from one tire seller to the next over the years.
Hmmmmm, I can't remember where I bought new tires for my CRX. Now I want to know (for no good reason, I just want to).
It would behoove me to look around for some old hoofs.
but the bottom line is that usually the narrower the lower the rolling resistance.
Originally Posted by theclencher
This is as good a time as any to comment on tires and rolling resistance. Like many, I always figured a skinny tire at high pressure would automatically roll easier than a fatter one at lower pressure. This is not necessarily true and so unless you have some empirical evidence to back it up it may not be a good blanket statement to make.
i dont know if that was directed towards me, but to save face, i do not think anybody accepts 'usually' as 'absolutely'.
to clarify, the difference between a 195/60 and a 185/65 can easily be lost between brands and styles. however, the chances of any 265/75 tire having lower resistance than a 235/85 tire are pretty slim at equal pressures.
don't waste your time or time will waste you