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Old 03-29-2008, 09:52 PM   #11 (permalink)
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There's a Uniroyal that is actually quite a bit lighter and is only 29.9" tall instead of 30.4 or so. The Δ for the radius / axle will be 0.65" for most and 0.4" for this tire. Too bad it is a Uniroyal.

The mass of the tires is gonna hurt. I can't drive across the city at a time where I won't need brakes. Short drives on short sections of roads in cold weather... yahoo. BTW, I got even worse mileage with my Aerostar before this and I drove it very mildly in the winter - no snows, I had to. Few people ever check their mileage except on long trips with summer gas. They end up thinking their overal mileage is way better than it is, especially in the winter. My wife's car and MetroMum's Corolla are proof. I finally realized this winter that axle bearings alone have a big impact on short drives.

The taller tires could help with cold rolling... a bit better gearing too although it puts my 4th 5th shift speed up from 62 KPH to 65 KPH. My speedo error is just less. All cars with analog speedo error on the side of no tickets and shortens the warranty. Honda lost a class action suit for this a couple of years ago. Anyway, same deal here. If I am driving at 100 KPH, the speedometer says 103 KPH plus or minus 1 and is GPS and mile marker verified. Funny how the ODBII port is bang on right from the factory. Anyway, I'd go 3% in their favour to 1.5% in my favour with 30.4" tall tires, and just about neutral for the Uniroyals.

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Old 03-29-2008, 11:31 PM   #12 (permalink)
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I thought the increase was pretty significant.

It could be due to less tire touching the ground (sort of like how a bike with skinny tires is easier to pedal compared to one with fatter tires), but also possibly because of the lowered rear-end reduced the aerodynamic wake of the rear?

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Old 03-30-2008, 08:20 AM   #13 (permalink)
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How much lower would you say it was? Do you remember?
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Old 03-30-2008, 12:46 PM   #14 (permalink)
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I don't believe the rear drop will be significant.
I just put my donut against one of the OEM tires[I keep some around just in case]
They are the same diameter,
however,
If Peakster has 13's they may be smaller.
but not much.
S.
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Old 03-30-2008, 05:06 PM   #15 (permalink)
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Quote:
Originally Posted by MetroMPG View Post
How much lower would you say it was? Do you remember?
I'd say it was about an inch. Here's some photos of how much they lower my front end:


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Old 03-30-2008, 09:07 PM   #16 (permalink)
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If you have low gearing, taller AND skinnier tires are better than smaller skinnier ones. if you run 3k at 60, smaller and skinnier won't help as much. it's bandaid for low gearing. If you lower (or have lowered) your vehicle, it will be good to compensate for the taller-ness, then taller would be the way to go I'm thinking.
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Old 03-30-2008, 09:30 PM   #17 (permalink)
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Ah, OK. That's a good illustration.
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Old 03-31-2008, 12:50 AM   #18 (permalink)
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Quote:
Originally Posted by metroschultz View Post
OEM = taller, wider, more contact patch
Donut = shorter [slightly], narrower, less contact patch, and they present a round face to the wind.
Contact patch doesn't change

The only things that will change contact patch is a change in vehicle weight or a change in tire pressure.

Wider tires will have a wider patch (left-right) but will be thinner (front-back).

Skinnier tires will have a skinnier patch (left-right) but will be thicker (front-back)
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Old 04-06-2008, 02:37 PM   #19 (permalink)
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Hi! this is my first post!

I found an article about how tire type can affect gas mileage (Honda Civic VX '95)
Quote:
...For the first 45,000 miles on the original set of tires (which were lousy handing, but very low rolling resistant Dunlops), I regularly averaged 55 - 57 mpg (and this is a CA emissions car). In the winter, the mileage dropped about 10 - 15%. When I replaced the original tires at 45k miles, the same tires weren't available. The originals were lousy (handling-wise) Dunlop SP4N* or something like that. I bought a set of different Dunlops to replace them and found the mileage dropped to 45 mpg under the identical driving conditions. Luckily, I bought the tires at a place that had a "1000 mile or 30 day satisfaction" guarantee so I was able to return the first set and try another set of tires without paying for the original set. I am a conservation freak, so a 9-12 mpg (up to 20%) drop in fuel economy was not acceptable...
Link to the original article
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Old 04-06-2008, 06:22 PM   #20 (permalink)
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Absolutely.

My Ford Aspire has 165/80/13" wheels and I recently put 195/55/15" on the car and there was a _noticeable_ increase in drag. I have a 1.1 stretch of road that I coast down and I wasn't able to make it all the way with the wider tires.

I took them off, and now I'm back to the 165/83-13", and she coasts as smooth as ever.

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