Practicality of tire upgrade
 

I have researched and know that larger skinny tires tend to improve highway fuel economy; however, my curiosity is how practical this is tire upgrade on an automatic transmission vehicle. I currently have the 215/60r16 installed and am looking at either the 225/60r16 or the 205/65r16. The car is a 2000 Ford Taurus that all other aero mods attempted so far have yielded no result. The only things that worked were properly inflated tires and a modified p&g style while leaving the car in drive. Sorry, just wanted to give a quick history to apply to this tire question. I am concerned the increased tire size will yield no result, or a negative one.

Thanks

I entered into this accidentally with my Dodge Caravan.
It came with 225/65R16 tires but my local Michelin dealers did not have winters in this size.
I opted for 215/70R16. Same rolling radius, but narrower.

Kind of an apples and oranges comparison, all-season Yokohama to winter Michelin,
but the narrower tire feels less secure, less stable on the road, and yet has very
slightly less rolling resistance (tested before and after change on a nearby hill).

Steve

That is a concern I have, as I tend to corner at rather high speeds. I would actually be tempted to go a little wider, and taller. I don't see the 225/60's changing things too much. The car seems to average 25 mpg on 87 no matter what I do. The only huge difference has been with premo gas, which doesn't make sense. And is also irrelevant to the current discussion.

Sentraguy, I know where you're coming from on this.
Experimenting with tyre size can get very expensive if you find you've jumped the wrong way and want to change back.

I recently changed tyre size with great success, by buying a cheap set of secondhand tyres on steel wheels. I went from 195/50/15 to 195/60/15.
It took me a while watching ebay, but I found a set for $50 that I've run for the last 6350 km.
This only worked for me because the Mazda gearbox ratios are too short for my particular driving conditions (mostly highway). You would know better than I how happy your Taurus is at speed.

I thought the taller tyre might adversely effect handling, but that hasn't been the case for my Mazda, so much so, that I'm keeping an eye open for a cheap set of 195/65/15's to try next.

Short answer: Tire size is NOT important, but differences between tires (meaning make and model) can be HUGE!! Careful selection could pay dividends!

Long answer: Barry's Tire Tech

another little secret ,well I guess not really, is that new tires get worse mpg than older smoother tires, rock hard 5 year old almost bald tires get great mpg , but of course arent safe.

Also a tire that is "aged" will also be slightly better. When you buy "fresh" straight from the factory the tire is not as cured as a tire that has sat on a shelf for a little while. I felt the difference between a brand new tire and last years stock and the older tire was firmer in the tread and and sidewall. It is also possible the the batch of rubber could be different but talking to my tire guy he said it is very common for an older tire to be firmer.

Capriracer - I look forward to your reply on this information (True or False)

I understand that the ribber compounds all have oil and carbon in them and the rubber eventually evaporates and leaves behind the harder materials, also much less traction on even almost new looking old tires, so i'm sticking with new, buy a lot of gas for what an accident costs,

I agree, I don't think you should let your tires sit around for years. I just question weather allowing the tire to cure a little longer may be beneficial? Paint, lacquer, adhesive are all dry to the touch in hours but have a much longer cure time. Latex paint will ball up if you try sanding it for repaint within a couple months of application. Most autobody shops advise waiting a couple months before waxing a new paint job. I have tested silicone adhesive at work and silicone that is allowed to cure for a year is almost impossible to remove but even silicone allowed to cure for a month or two can be removed very easy.

I appreciate all the input. I especially loved the long answer, thanks. I am thinking about trying the 225/60's as they are not that much bigger. I do hot rod the car a bit at times, and the wider tire should definitely help cornering. And the issue with the back tires is they are going flat due to dry rotting. My dad worked for Goodyear for almost 30 years and informed me that the cheaper tires are more prone to dry rot than the better made tires. It would be interesting to see how big a difference there is between the batches.:rolleyes:

Did you try a search??????

I have addressed this EXACT SAME issue alot more than just once.....:rolleyes:

And that's just me......
Another member with a scion box tested 3 different tires AND rims......

1. It's a taurus.....not a porsche.....why are you corning so hard.......please.
2. If you really want to ricky race....get some 45s or 40s. That's cornering.
3. (As has been discussed at length...) larger diameter tire will produce lower rpms at cruise. period.
4. Going up in rim AND tire size becomes more complicated because of additonal weight.

2002 infinti Q45 Sport...factory 245/45/18 on alloy...upped to 245/50/18 better mpg
2006 Kia Sportage FWD V6 EX .....factory 235/60/16....upped to 235/70/16 better mpg
Also, kia feels MUCH better on the slightly larger tire.

Thank you for getting me back on point, I got a little distracted. I did do a search and the tire size, handling, etc. has just been addressed again. My biggest question, which was unanswered by a search of ecomodder and google, is if it is even worth it to change tire size on a car that has an automatic transmission. Does anyone know if the computer will adjust for the change in tire size and yield no result, or will it be beneficial? And I am well aware she is not a Porsche, but I still enjoy throwing her around the curves. But don't sell the Taurus line too short, let's remember the SHO and what car is it the police are starting to go to again?.....:D

Part of what makes a tire work is the flexibility of rubber. As a tire ages, it loses flexibility - and it therefore is more prone to failure. That's why you shouldn't let tires 'age" - artificially or otherwise.

Plus, it isn't the aging factor that is the most important factor in a tire's rolling resistance over time. It's the loss of tread rubber. That loss of mass decreases the amount of energy consumed as the tire rolls through its revolution.

Besides, I don't think the harder rubber helps RR. If anything, the internal friction of soft, pliable rubber is less than hard, stiff rubber. The additional stiffness of the rubber only adds a small part to the overall stiffness of the inflated tire. Most tire stiffness is caused by inflation pressure.

And batch to batch differences? Not as much as you might think. Rubber batches are mixed with other batches many times. That spreads out any abnormalities over many, many individuals. Besides, there are QA controls after every mixing, so abnormalities are quickly isolated and not allowed to re-enter the process.

I think the data says there is only a little benefit from changing tire size. Plus, there is limited room in the fenderwell and you just don't want anyhting rubbing. Put a different way, unless you are sure there is room for larger tires, the risk of doing it wrong outweighs the potential benefits.

However, there is a HUGE benefit from carefully selecting tires for the properties you want.

Seems to me you'd have to try and see, on paper very hard to figure, if you lose a few hundred rpm at highway cruise and you cruise a lot on highways , then probably go for it since slightly larger throttle opening should help mileage also as well as the rpm change,

(note: the police are drriving dodge chargers)

Am well aware of the sho.
I am also aware of the difference between the two.
Kinda like the difference between a V6 mustang and a shelby.

So you have changed out all the suspension parts, and added all the engine parts......right?
1. Both of the cars I have documented are auto transmissions.
2. You need to check a taurus form to see if the Tranny ECU adjusts.
I know that on the infiniti products the tranny will 'learn' how you drive and adjust accrodingly. (as discussed at length in my posts) But it cant tell if the tires are different sizes. IMHO no car can. But if your corning style is reflective of your driving style, then you have 'trained' the tranny ecu to shift for speed and not for eco. You would need to unhook the battery for an hour and then it would reset and start to learn again.
3. seriously, if you arent running 40 or 45s AND you really are 'cornering hard'....well stay off my streets. you are flexing the sidewalls.
4. you remind me of the guys looking to do 2 inch dual exhuasts. Large exhausts only work at wot. WOT only happens 2% of your life. unless you race an oval track, you are only turning 10% of the time. And how much of that can you race thru the curves???
5. The only draw back to taller tires id the speedo is off. But if you are running a scangauge (which you should) then you can correct the speed on the scangauge.

here are the multiple results from searching 'taller tires'
taller tires - Google Search

2013 Taurus Police Interceptor : Ford Taurus Forum
I saw one of these with the NC Highway Patrol about a month back. I didn't even know it was a cop until I saw the decals on the side.

And thank you MCCrews for coming out of nowhere to blast me for asking a question, and then further blasting my driving style (to which you know nothing about) off one comment that I made. I can see that my welcome on this site is apparently worn out. Thank you all who had helpful input about my questions, and a lesson learned for me.

Don't take it personal Gone2, mcrews is a... scumbag to anyone who has a differing opinion, he's not singling you out, it's just how he is

Thinner tyres occasionally lead to an improvement in throttle response, unless we're talking about a torque-monster. But they also increase braking distances...

Anyway, in a Taurus I wouldn't be afraid to try 185/70R15.

Tire type is more critical than minute differences in tire size, yes, but tire size also plays a role and shouldn't be ignored. Increasing the tire size will affect handling, but not really by much. If you're going to drive so close to the edge that 1/2" of sidewall is going to make the difference, you shouldn't be doing it on public roads (or in your DD).

For hypermiling purposes, especially with an automatic, it's about gearing. Increasing your tire size increases your final drive ratio. It'll also make your automatic downshift sooner, eliminating some of the potential gain and maybe making for worse overall FE. How does your car feel right now, Gone2? Does it shift a lot or do you spend a lot of time with the torque converter locked up? If you're doing a lot of driving close to the edge of downshifting, then taller tires might be exactly the wrong thing for you.

Minor changes in tire size can get you 3% or 4% more distance travelled per wheel revolution by only adding about 1/2" to your tire radius. If changing the gearing on your tires won't send your transmission into lower gears it could be a big help. I went with LRRs that added 0.4" to my radius, so now my car is going 103.4 miles every time it thinks it's gone 100 miles.

Actually, my issue is lazyness....not differing opinions.
Fact: his question (of the automatic tranny) is addressed in multiple tests of larger tires. He just didnt want to look and see deeper than the first post.

Instead of checking the link provided and spending time reading and learning, he wants to be spoon feed. There are atleast 4 very well documented larger tire tests with 3 being automatics.

ps. Ive driven a Taurus. I've driven a SHO. BIGG DIFFERENCE. And the best I got out of the taurus was 28mpg. The problem w/ the tauras is it cant be driven 'egine on, in neutral' the tranny doesnt drop the idle.

Like stated above, you're better off choosing a more fuel efficient tire.

I suggest the Michelin Energy Saver A/S. It is available in your size. Michelin Energy Saver A/S

Most tire centers offer a $70 rebate on 4 Michelin tires every other month. That puts these tires at a competitive price point.

The only connection between the car and the road is the 'contact patch' of the tire (absent a grounding strap, of course). A wider tread helps cornering, a longer patch helps the ride. A softer material helps grip, and thus cornering; a harder material helps lower rolling resistance, and thus helps mpg and hurts stopping distance.

There's a lot to consider. Did I mention hydro-planing?

EDIT: I see there was more than one page. Never mind.