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Old 02-10-2012, 12:47 PM   #81 (permalink)
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Quote:
Originally Posted by racerc2000 View Post
it seems ive rubbed some people the wrong way. it seems I will have to go elsewhere to get an unbiased answer.

as for anything meaningful that was mentioned. thanks for your time.
RacerC2000,

I hope you come back, because you will not be finding the answers to your questions elsewhere.

But you need to be aware that even tires of the same size can have HUGE!!!! differences in rolling resistance - up to 60% different.

Changing tire size has a small affect.

Replacing OE tires (which are generally known for their low RR), and replacing them with tires with improved treadwear and traction properties - well it's going to negatively affect your fuel economy.

And for heavens sake, if you've read anything about tires in these forums, you should already know that you're going to take a hit in FE just by putting on new tires.

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Old 02-10-2012, 09:29 PM   #82 (permalink)
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thanks for the reply. besides testing my own in a series of coast down tests. is there a source with more tire info? say specific rr # as opposed to just low rr tire

I figured new rubber will always be worse then worn rubber when comparing RR. considering the car only has 13k miles ide hope the new/worn ratio wouldnt be as bad.
but. I dont think the SC 18s (225/55-18 goodyear LS-2)or the base model 16s (215/70-16 Wrangler HPs) were focused towards fuel economy.

the wheels have been purchased but tires have not yet. so I can still make a better choice in both width of tire and diameter.

I know in many cases my move to light weight 19s would be a bad move.

I was trying for the lightest pairing of wheels and tires for the original selected size. but maybe I should look at it from a different angle.

wheels. save 12lb each. would 4lb be a negligible gain/loss if said tire has more/less RR (4lb+ heavier tire but lower RR)(4lb+ lighter but higher RR)

is there a specific ratio or scale/graph for when certain characteristics makes a gain in FE negligible.

ie: taking heavy aero type wheels and heavy extreme low RR tires
compared to feather weight non aero wheels and normal RR tires?

if Im going off on a tangent im sorry.I have an engineers mentality and a thirst for knowledge.
Quote:
Originally Posted by ProDarwin View Post

Conversely, swapping to a manual trans that is geared longer overall would allow me to get respectable mileage around town in 4th and have good economy in 5th on the highway.

If I ever do the high mileage build I want to do, it will involve the longest geared SOHC transmission, and 23" tires to drop the car by .5", and springs to go down as far as I can total. My rpm in OD would still be approx 10% lower than now.
my auto will act the exact same. it is a 3 spd auto with 2 overdrives.
Gear Ratios: 1st: 2.786, 2nd: 1.614, 3rd: 1.082, 4th: .773, 5th: .566, Reverse: 2.000, Final Drive: 4.500

luckily I do have the option of a 6spd manual. (oem 5 spd manual uses a 6spd manual case so its an easy mod) that may be an option but costly.

but really. unless I chop off the roof it will never be on any top fe lists.

Last edited by racerc2000; 02-10-2012 at 09:47 PM..
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Old 02-11-2012, 07:27 AM   #83 (permalink)
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First, you can be pretty confident that the OE tires have at least SOME RR consideration. After all, the vehicle manufacturer is require to publish an MPG value - and tires contribute to that. However, some OEM's push the envelope pretty hard.

You can also be pretty confident that any replacement market tire has been given LESS consideration for RR - because those tires carry a treadwear warranty. Even if they don't, then they are designed with grip as a primary consideration - which is also in opposition to RR.

And the term "LRR" is a bit of a misnomer. Tire Rack applies that label based on what the tire manufacturer says - and they generally are referring to the RR compared to comparable tires, meaning similar treadwear and traction ratings. So if you are taking off OE tires, and applying replacement market tires with high treadwear ratings, you can be close to certain that you'll take a FE hit.

Tire weight is not a good indicator of RR - or, IMHO, FE. The only time weight plays into the FE value is on accelleration - and a change in weight of tires and wheels is small compared to the overall weight of the vehicle.
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Old 02-11-2012, 09:34 AM   #84 (permalink)
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wheel and tire weight is more of a performance attribute. for every 1 lb dropped its the same as removing 10lb static weight from the vehicle. so my thought of removing 60lb from the wheels equating removing 600lb from the vehicle. would not only improve performance but also economy. but I suppose the factors effect the performance and economy in different ways.

I may feel quicker and on a track show a diff but in reality effect economy in the opposite way. I guess its a double edged sword like some aero mods (increasing drag and downforce instead of reducing drag)

ive looked into my OEM tires. and noticed 2 tires of exact same size and branding under the goodyear LS-2 in 225/55-18

spec wise they seem to be identical. except for these small diff.

one is slotted as specifically for Honda(assuming my vehicle specifically) origin is US and the weight is 28lb.

the other is origin JPN with a weight of 29lb.

but all other specs are the same

I wonder what isnt listed that is diff between the 2. esp since 1 lb shouldn't be an economy move? am I the only one that finds it odd?



but I do see where your coming from. the stock tires still out perform the aftermarket. and the 10lb diff between aftermarkets was only a 0.4 mpg diff. but the performance was better
.................................................. ..............................avg avg
.................................................. ...................weight spd mpg
BMW 3 Series equipped with Original Equipment (16")42.5lb 38.7 22.8
BMW 3 Series equipped with Plus One (17").............38.5lb 39.0 21.5
BMW 3 Series equipped with Plus One (17").............48.5lb 38.8 21.1

Last edited by racerc2000; 02-11-2012 at 10:04 AM..
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Old 01-19-2013, 10:03 PM   #85 (permalink)
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Quote:
Originally Posted by California98Civic View Post
What a great suggestion Carlos gave. Thanks for adding it that way. It suggests that taller is not better if it means significantly heavier, but that weights being relatively equal taller is quite a bit better than OEM. Given my plan to go taller on the fronts and create a net loss in weight by balancing it with smaller rear tires--all on the stock 15" wheels--this is really encouraging data. Much obliged. Model test. I'll have to consult this again next time I'm testing. You do these well.
In general, I think you are right about taller tires. However, I'd suggest folks consider their top gear ratio before plunking down some money on taller wheels/tires. My truck has a 3.55 rear end, and 5th gear is a 0.67. The engine turns only 1900 rpm at 70mph. With SentraSE-R's engine originally turning 3200 rpm at 60mph, I'm not surprised taller tires helped.

@SentraSE-R, thanks for sharing the test results. Your results match results I found at TireRack: Wheel Tech - Road Wheel Weights Can Affect Your Vehicle's Show...and Go but you were more thorough!

Quote:
Originally Posted by racerc2000 View Post
humm I wonder if I will notice an increase in my FE

dont laugh but I have a 2010 honda element SC not exactly the most gas friendly vehicle with my best mpg being 24.4 :/

but my oem wheels and tires are very heavy. 18x7 with some 225/55-18s.

they weigh in @62lb wheel+tire

ive purchased some larger wheels.

19X9 and 19X10s with 245/45-19 front 275/40-19 rear. (I understand rolling resistance will be worse.)

but the fronts will weigh in @45lb the rears 49lb

do you think this will effect my economy in a good or bad way?
If you didn't get a Scangauge, an Ultragauge, an MPGuino or OBDuino yet, (I think that's the big 4) by all means do so! Use it to not only monitor your daily driving, but to keep a daily fuel log. Log what mileage you get each time you drive. This makes you more aware of what your driving habits are doing...and what those new wheels and tires are doing for you.
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Old 01-23-2013, 01:06 PM   #86 (permalink)
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Econoram, I know several times in these threads I have stated that the results (taller tires lower rpm) tend to apply to cars more than trucks.
******
Also, the results are pretty accurate when ONLY increaseing the tire diameter and staying w/ the stock wheel.
But When going to plus one and plus 2 rims, the problem becomes moving the mass/weight of the tire/rim combo farther out.
********
Not sure bout the 1 lb equaling 10 lbs comment.
All the outside data and reports say 1 lb static (still) weight is equal to 4 lb rolling. Specifically on tire/rim weight.
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Old 01-24-2013, 08:02 AM   #87 (permalink)
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Broad generalizations may get you close, but there can't be a one size fits all equation. Wheels and tires of different masses cause you to build different amounts of angular momentum in the sets. (In addition to the additional RR, gearing, and Aero differences.) Angular momentum equations are all based off the lever arm (distance from the center) to where the mass lies. Two tires of equal diameter and equal weights could have significantly different amounts of angular momentum required to be built to get to the same speed. For example, a heavy tire on a lightweight alloy rim will have its mass on average further from the center, while a lightweight tire on a heavy steel rim will have it’s mass closer to the center. They may weigh the same, but the heavy tire light rim combo will take more force to get rotating.

The real “answer” is that you will have to evaluate your wheel and tire situation on a case by case basis. Light wheel and tire combinations will have a far greater effect in city stop and go driving as compared to highway driving.
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Old 01-31-2013, 08:34 PM   #88 (permalink)
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Quote:
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Econoram, I know several times in these threads I have stated that the results (taller tires lower rpm) tend to apply to cars more than trucks.
******
Sorry brother, you are right. I remember reading that now.
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Old 02-01-2013, 09:25 AM   #89 (permalink)
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I think the issue w/ trucks (imho) is that at some point taller/bigger tires may already be on the truck when the desicion is made to start ecomodding.......
Also, truck motors are desgined to pull not necessarily cruise.
just my opinion
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Old 02-01-2013, 10:35 PM   #90 (permalink)
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Timely resurrection.

I just swapped the tires/wheels on my '11 Forester with another Forester('13) owner. OEM for me was 225/55/17 alloys and I swapped for his 215/65/16 alloys (+$150), my tires had about 16K miles on them, his had about 4K miles.

When we swapped we weighed each wheel/tire combo with the 17s weighing in at 45.8 lbs and the 16's weighing in at 42.2 lbs. Unfortunately, I could not do ABA testing

The diameter is about the same (not quite but within 1% with the 16's being slightly taller). I'm not expecting much if any FE improvement but I got $150 in my pocket already and 16" tire selection is much better and they are somewhat cheaper than 17's. Don't really care much about the looks.

When the current tires wear out I'll replace them with 215/70/16's for about a 4% increase over the OEM tire/wheel height. My Forester has a manual transmission with a 4.11 final drive ratio so that's when I'm expecting to see some FE improvement.

Comments?

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