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Old 06-25-2018, 09:43 PM   #41 (permalink)
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I was doing a little research today on the effects of tire wear vs tire weight and found that the tread from new to scrap is approx. 20% of a radial passenger tires weight. So if you have a new 25lb tire, then the scrap tire would weigh 20ish lbs. Based on the article I read I'm not sure if they consider scrap to be 2/32" or 0/32", but either way the weight savings is not insignificant.

To make the math easy, if you have a 25lb tire and it has 10*/32" of tread depth, then multiple 25lbs x .80 = 20lbs scrap, subtract the difference which is 5lbs, and divide that by the starting tread depth (10*), you get .5lbs per 1/32" of tread.

I realize this is not overly significant on a newer tire, but using the numbers above with say 3/32" left on your tires you'd be saving 3.5lbs per corner or 14lbs total of rotational mass.

I've read quite a few different threads on why people who get new tires lose mpg's, even sometimes being LRR, but I didn't see too much discussed on the weight differences of new vs old tires.

I have two set's of wheels and tires at home and a third set of just tires and was able to calculate all of the tire's 1/32" weights and came up with between .4lbs-.5lbs per 1/32" for the three tires respectively.

I realize there are a number of factors that go into losing mpg's with new tires, but this is just one more thing to consider. I personally noticed a difference in the driving dynamics of the car while hypermiling when I did weight reductions that varied from 120lbs to 165lbs depending on if I had the spare tire, jack,etc.. The 10lbs per corner in wheel and tire weight reduction was specifically noticeable. It's not that I think my car had just gained 100hp, but while feathering the pedal ever so slightly I was able to maintain higher mpg's with less effort. If this has been discussed and I missed it, apologies.

http://infohouse.p2ric.org/ref/11/10...intro/tire.htm


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Old 06-27-2018, 10:44 PM   #42 (permalink)
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I can say 1st hand shedding 9# per wheel gained me 1+ mpg from the swap... throttle response improved noticeably overall went from low 19's to upper 20's, easily... 21's if I apply myself..

mpg data in post #1
https://www.cumminsforum.com/forum/3...-makeover.html
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Old 06-28-2018, 08:41 AM   #43 (permalink)
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It's hard for me personally to quantify mpg gains without a-b testing. Driving in a vacuum I would be able to say definitively I gained x miles per gallon with this mod. Driving in the real world and not doing a-b testing makes all the mods I do drivers aids. If I can feel a difference or see higher real time mpg's (displayed) are easier to obtain, then I consider the mod a success. Unless your commute is a super simple loop and relatively traffic free, there are too many variables that go into getting an accurate reading of mpg's gained imo. I didn't turn my car off at a stale red light because I thought it was about to turn green but it didn't, I've got ten cars up my six so it felt polite to go 55-60 instead of 50, I had to actually stop at that 4 way because a cop was sitting there this time, the guy ahead of me slowed to a crawl and ruined one of my big coast hills. After a mix and match of a million variables working in your favor or against it, then at that point lifetime average is about all we can go by.
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Old 06-28-2018, 12:06 PM   #44 (permalink)
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I would say do it... around here (seattle area) there are so many hills and the effect of the lighter wheels was noticeable on the hills. I am doing a driveshaft as well, supposedly 20# lighter than OEM. DS in hand, waiting for an install.
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Old 06-28-2018, 06:20 PM   #45 (permalink)
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https://www.caranddriver.com/feature...d-tires-tested

The article shows a 2.2mpg difference between 15"-40lb wheel and tire setup and 19"-54lb wheel and tire setup. I'm not sure how much the size effects the mpg's vs the weight difference of 14lbs per corner. I would guess the latter has a bigger effect.
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Old 06-28-2018, 07:01 PM   #46 (permalink)
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To be honest here you are chasing something that will never pay off. Then you have to worry about messinng up your nice new wheels whereas you really dont have to worry about it stock. A lot of people dont realize that weight and inertia play a huge role in acceleration, but not much in FE or maintaining speed. I mean I would 100% agree if we were talking about performance, but if we are talking about spend 1200$ on wheeels and tires to save almost nothing I'd have to say spend it somewhere else.
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Old 06-28-2018, 07:36 PM   #47 (permalink)
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Quote:
Originally Posted by hayden55 View Post
To be honest here you are chasing something that will never pay off. Then you have to worry about messinng up your nice new wheels whereas you really dont have to worry about it stock. A lot of people dont realize that weight and inertia play a huge role in acceleration, but not much in FE or maintaining speed. I mean I would 100% agree if we were talking about performance, but if we are talking about spend 1200$ on wheeels and tires to save almost nothing I'd have to say spend it somewhere else.
I agree completely. I paid $250 for 4 Advanti B1 Lupo wheels (16x7) with 4 Goodyear Winter ultra grip tires 12/32" out of 13/32" tread. The rims were purchased new with the tires and came off a wrecked Mazda 3. I needed a set of winter tires to go on my steel wheels. The tire value was $320 new before tax or shipping, so the wheels were as close to free as it gets. I saved 8lbs per wheel with the alloys. I would never advocate spending any kind of serious coin for wheels in search of mpg's, but if you can get a used set for dirt cheap then I say go for it. If the article in my previous post has any truth to it, you should be able to save approx. 1+mpg with 10lbs shaved off each corner of rotational mass. Does that mean it will happen..no.. but in the article they saved 2.2mpg with 14lbs shaved off each corner.

The real question is should I cover the nice new wheels with coroplast?
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Old 06-29-2018, 09:36 AM   #48 (permalink)
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Here's my fuel data over the last 6 months, covers the wheel change. Pulled old wheels off & sold them which went towards the new wheels (lightest OEMs available). Rotating mass drop helped throttle response... every start (rolling, throttle up) event, hill climb, rush hour traffic drive etc has benefited from it. I agree that steady state mpg does not change much and have observed my steady state mpg stay pretty much the same while the commute mpg with every day driving, cold starts etc has gone up. Heck I get equal or better mpg commuting to work than I do on the hiway for long stretches. (manual trans truck so I can coast a lot in traffic & down hills)

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Old 06-29-2018, 02:42 PM   #49 (permalink)
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My experience with these taller wheels/tires is that I am getting quite a bit better FE than with my smaller ones during steady freeway cruising. At least 5 mpg at speed. My fuel log won't express it because I am using the gain to allow more steady cruising instead of P&G. I just now drove 25 miles freeway and got 61.x mpg without P&G. But there are multiple factors involved. The tires are not the same brand, the aero characteristics are different in a few ways. The wheel is not the same weight to size ratio (is that a thing?). My BMW MINI seven hole 15" wheels are 12lbs while my VX CIVIC 13" wheels were 9.7lbs.

I think without controlling for confounding factors, including weather season and driving habits, we all could relate individual experiences all we want, and still not identify a general rule.

That's what was remarkable about the "Tall Tire Test" thread... th e OP tried to control for or account for the wide variety of variables.
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Old 06-30-2018, 07:38 PM   #50 (permalink)
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Tire design and tread, no question (to OP). Trade-offs have to be worthwhile, though. Same for wheels, load limit can’t be downgraded.

If i am averaging over 100k on a set of tires (and I do, easily) then the FE gain doesn’t mean as much (especially if tire life, tire/wheel loads or safety is downgraded).

Take-offs from later models of same truck are certainly of interest.

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