Archives

whats the tallest tire i can run on my 2003 at echo i have 175/70/14 now will a 185/70/14 overall be taller i now the first number is width is their any body running a taller tire want all the mpgs i can get!

The first number is the tire width in millimeters. The second number is the aspect ratio, or sidewall height as a percentage of tire width. The last number is the rim diameter in inches.
Going wider with the same aspect ratio results in a tire that is slighly wider and slightly taller.
Keeping the width and going one step up in aspect ratio results in a tire that is the same width but taller, due to the taller sidewalls.
Keeping the width and aspect and going to a larger rim will keep the same width and sidewall height and the tire outer diameter will be larger by the same increase in rim diameter. This requires replacing the 14" rims with something larger in size.

The 175/70-14 tire is 7" wide and 23.7" tall overall. It rolls about 866 revolutions per mile.
The 185/70-14 tire is 7.4" wide and 24.2" tall overall. It rolls about 850 revolutions per mile.
(General Altimax RT tire at tirerack.com used as an example for these numbers - other brands similar but not exact)

Switching to the oversize tire won't show any effect on FE if you are counting miles on your odometer and gallons used, because the larger tires underclock your odometer. For every 100 miles indicated on the odometer, the car travels an actual 101.9 miles. So in terms of gallons used versus actual distance travelled, your FE would increase 1.9%, reflecting that extra distance you actually cover that the odometer does not measure.
If your car uses 2.5 gallons to travel 100 miles shown on the odometer, you would calcluate your fuel economy as 40mpg. But if the car actually rolls 101.9 miles on the oversize tires, your actual fuel economy is 40.76mpg (101.9/2.5). But without a way to judge actual distance travelled, your math would show the lower number.

Since cars today are designed by computers, there is very little wiggle room in tire size. Going to a tire that is more than about 3/4 inch larger in outer diameter will likely result in rubbing against front suspension components when the wheel is turned to the lock in one direction or the other. This rubbing can damage the tire or the part(s) it contacts. Going beyond one inch larger can result in continuous rubbing against suspension or brake components.
Going more than about 4% oversize on tire outer diameter also puts additional strain on braking components, and so most tire shops will warn you about potential brake problems. This is true for anyone who is rough on the brakes, but for hypermilers who DWB , the risk is largely academic.

Generally speaking, your money is better spent buying tires that are known to have "low rolling resistance" and/or a 51psi max sidewall rather than trying to gain fuel economy with larger tires. If you want to go larger in size, one option is to choose one size narrower while going taller. Depending on the rim offset, the narrower tire is a little less likely to rub when the steering wheel is turned lock to lock. But it is still a risky proposition, as the additional cost of replacing damaged tires will far offset any gas money saved.

It looks like you're already running larger tires. Tirerack.com lists 175/65R14 as the standard size tire for the Echo Coupe and Sedan, with a 23" diameter. The 175/70R14 tires you have on your car have a 23.7" diameter, which is 3% taller than standard, and about the maximum size you should run to ensure your tires won't rub against brake lines, fenders, etc. You don't want to run wider tires alone, because they just add rolling resistance.

There's an optional size tire for the Echo sedan, 185/60R14, with a 23.3 diameter. Again, you're better off going to the thinner and taller 175/70R14 replacements for mileage.

thanks fellows any list of llr tires?

thanks fellows any list of llr tires?

Check in the Files section for the file with the name ending in "Tire Data". It list the numbers for some tires. There is no complete list out there anywhere, but this file is a start.
Usually, I just cheat and find out what OEMs are using. They have the money to do that research for us, and they always go for best FE except in the case of "sport" or "handling" packages.
The stock tire on the Prius (engineered the no-compromise FE) is the Goodyear Integrity, and I tend to believe that if there were a lower-resistance tire out there, Toyota would have used it instead. So the Integrity is likely the best or one of the best for fuel economy.

Like others have said-find lower RR tires. The 185/75 14 will hurt your mpg because they are 10mm-about 4/10" wider. They will hurt two ways-more rubber on the road generally means more rolling resistance. They also will raise drag because they will offer about 1.7" times the height-24" more frontal area-and tire frontal area isn't very clean.

Tall also usually means heavier, and this will decrease you city mpg since you are constantly speeding up slowing down in the city.

Hunt for lower RR tires in the same width-175- you have now.Your 175/70 14 seem just fine size wise.

If you don't mind spending $$, you might hunt up lighter wheels.I would guess most Echo's come with steel wheels. If you decide to blow $500 on new wheels make sure they are actually lighter- at least 2 lbs lighter. If the manufacturer doesn't give a weight, don't buy them. Usually OEM aluminum wheels are lighter than the cheapo OEM steel wheels, but some aftermarket wheel makers go strictly for looks. I would take a chance that Toyota alloy-aluminum- wheels were lighter, but not aftermarket.

Luck,
Charlie

Check in the Files section for the file with the name ending in "Tire Data". It list the numbers for some tires. There is no complete list out there anywhere, but this file is a start.

Usually, I just cheat and find out what OEMs are using. They have the money to do that research for us, and they always go for best FE except in the case of "sport" or "handling" packages.

The stock tire on the Prius (engineered the no-compromise FE) is the Goodyear Integrity, and I tend to believe that if there were a lower-resistance tire out there, Toyota would have used it instead. So the Integrity is likely the best or one of the best for fuel economy.

Maxx,

I couldn't let this post go unchallenged.

Before I start, let me explain the situation with rolling resistance:

Tire engineers have to balance 3 properties - rolling resistance, wear, and traction. To improve one, you have to sacrifice one of the others (or both!) (Side note: There are other properties that interact with these 3 and they also are subject to similar compromises. Needless to say this gets very complex and it takes several iterations to get the compromise right.)

Vehicle manufacturers TEND to specify tires with good rolling resistance - but not always. As you pointed out, sport or handling packages are exceptions, but there is also wear issues that will influence this decision - and the exact nature of this 3 way compromise not only varies from vehicle manufacturer to vehicle manufacturer, but also between models from the same vehicle manufacturer.

For example: Ford Tauruses come with tires that have good wear properties. They could have specified tires with much lower rolling resistance, but deliberately chose not to in order to avoid tire wear issues (like they had in the past.)

The way your post is worded implies that vehicle manufacturers "search" for tires. To the contrary, they "write specifications" for tires - and the tire manufacturers submit tires for qualification that meet those specs. In order to submit a tire for qualification, a tire manufacturer has to be "approved" - which means there is a short list of approved tire manufacturers for each vehicle manufacturer.

For example: Cooper is not approved at any vehicle manufacturer. Further, for Cooper to supply tires to - oh, let's say Ford - they would have to undergo a certification program that would be specific to that vehicle manufacturer. Normally that would include a TS16949 audit. (TS16949 is an international quality standard). But passing a TS16949 audit is usually not enough and this process becomes costly and time consuming - which is one of the reasons Copper hasn't done it!

Further, since every vehicle manufacturer would set the specs for their vehicles - and for every model - and the specs would be different among all the combinations of makes and models, then a given tire line (like a Goodyear Integrity) could have a wide variety of specs - including rolling resistance - and it would be different for each size (since that would be a major parameter specified by the vehicle manufacturer.)

Side note: There have been situations where the same size and name tire have been supplied to different vehicle manufacturers - which had different specifications. In one case, the difference was so great that it was obvious when you looked at the 2 tires side by side. (Hint: One of the tires listed on the GreenSeal report published in March 2003 was supplied to 5 - yes, five! - different vehicle manufacturers and each of them was different. There is no way to tell from the report which of the versions GreenSeal tested. Also, since that time, those particular 5 tires have been replaced by a single, but different still, version (that would be #6).

What you should take out of the above is that the different sizes of the Goodyear Integrity will be designed to different specifications and are, in fact, quite different, size to size.

So:

1) Rolling resistance is not always "maxxed" by vehicle manufacturers - even considering the handling issues.

2) You can't rely on the fact that a tire is supplied to an OEM as a method to determine if the tire has good rolling resistance.

3) Further, if the tire size your car takes is different than the tire size supplied to an OEM, then that is further reason to be skeptical.

4) However, if you have no additional infomation, then your odds are better if you pick a tire line that is supplied OE - and better still if you pick the particular tire size supplied.

I hope this helps clarify things.

Capriracer,

You might be splitting hairs a bit. Maxx did say that OEMs went for max FE except "sport handling" but he didn't literally mean "ALWAYS" he just meant that as a general rule OEMs do select tires that give good FE. There also is little chance that you will be able to reliably select a tire that has lower RR. A few-only one that I can think of CR-consumer type groups- do occasionally post tests of tires, but as you pointed out tires are changed from year to year, and just because a tire had low RR in a 2005 test it doesn't mean that it has low RR now.

My point , Maxx's suggestion to select the oem tire for good FE is a good suggestion, since there really isn't much hard data available to the public on current tire RR. I think Michelin might have some data, but safe bet it is biased in their favor, and their tires are extremely expensive.

You probably literally correct, but it is impossible to act on your suggestion-since there isn't any data available. The OEMs specify good FE-choose them and you will get good FE-maybe not always the best, but pretty close..

Thanks,
Charlie