Taller Tire Test (5.7% MPG increase observed on Honda CR-Z @ 55-65 MPH)

[royanddoreen]

That raises a thought. Earlier in this thread i spoke of gearing to low in cars nowadays but if your not eco minded those higher gears will hurt eco more when driving in stop n go traffic.. city driving.I live in a rural area so higher gears suit me better. I am sure I would have a hybird or electric if I lived in the city.

[ctgottapee]

This result still baffles me as it seems to go against what the car manufacturers are doing, especially those who use adaptive systems to lower ride height at highway cruising speeds.

I was planning on going on a tad smaller tires, due to having already large tires as standard but now I'm wondering...

[ps2fixer]

Originally Posted by ctgottapee

This result still baffles me as it seems to go against what the car manufacturers are doing, especially those who use adaptive systems to lower ride height at highway cruising speeds.

I was planning on going on a tad smaller tires, due to having already large tires as standard but now I'm wondering...

I was in the same boat when I needed to change my tires, was going to target ~5% larger tires, but went with factory sized... kind of wish I would have bought 2 larger to test, worst case put them in the back (FWD).

[mcrews]

Originally Posted by ctgottapee

This result still baffles me as it seems to go against what the car manufacturers are doing, especially those who use adaptive systems to lower ride height at highway cruising speeds.

I was planning on going on a tad smaller tires, due to having already large tires as standard but now I'm wondering...

You are probably baffled because there are two different concepts.
1. Lowering a car to achieve aero is NOT done by reducing the tire size. (Because they know reducing the tire size hurts the gearing) Cars are lowered by lowering the suspension.
2. reducing tire size INCREASES the rpms of the engine. That increases gas consumption.
3. THe SLIGHT increase in height is more than offset by the deceased rmps of the engine at highway speeds.

There are numerous threads on this topic where you can get a fuller understanding.

[mcrews]

Originally Posted by ps2fixer

I was in the same boat when I needed to change my tires, was going to target ~5% larger tires, but went with factory sized... kind of wish I would have bought 2 larger to test, worst case put them in the back (FWD).

As a thought, I just pick up 2 Kuhmos (same as I run) used on ebay. They still had about 70% tread and were 1/2 of the price of new.

[D.O.G.]

Originally Posted by ps2fixer

I was in the same boat when I needed to change my tires, was going to target ~5% larger tires, but went with factory sized... kind of wish I would have bought 2 larger to test, worst case put them in the back (FWD).

I bought my Mazda with 195/50/15 tyres fitted by the previous owner.
Original size was 195/55/15, so it was hurting my fuel economy a bit.

I recently bought a set of secondhand 195/60/15 tyres on steel rims as a cheap way of testing what sort of gains the taller tyres could give me.

Compared with my GPS, my odometer is now 5.7% slow, so I'm multiplying that reading by 1.057 to get accurate tank averages and while I want to get a couple more fills with these before I start crowing, it's looking good.

[D.O.G.]

Originally Posted by D.O.G.

I bought my Mazda with 195/50/15 tyres fitted by the previous owner.
Original size was 195/55/15, so it was hurting my fuel economy a bit.

I recently bought a set of secondhand 195/60/15 tyres on steel rims as a cheap way of testing what sort of gains the taller tyres could give me.

Compared with my GPS, my odometer is now 5.7% slow, so I'm multiplying that reading by 1.057 to get accurate tank averages and while I want to get a couple more fills with these before I start crowing, it's looking good.

Well, I've run these tyres for 2700 kilometers now and am seeing a 3.9% decrease in fuel consumption, from 5.75 to 5.53 L/100 km

I can't attribute all of that decrease to the tyre size however, there are other factors that are probably at work here, the warmer spring weather and the change in model/brand of tyre at least.

[evilgeniustodd]

Originally Posted by SecondWind

Some work I just completed...

Edit by admin: see attached spreadsheet for raw data and full text; some of the spreadsheet text is quoted below...
Michelin 205/65R16 Energy Saver A/S

Trying to get the guy at Discount tire to actually order these was like pulling teeth. Ridiculous amount of resistance.

[mcrews]

Since I last posted on this thread, I sold the Q45 and am driving a 2006 Kia Sportage.
I am linking the page where I upsized the tires.

Again, as with the Q45, this has resulted in lower rpm and higher mpgs!!!!
http://ecomodder.com/forum/showthrea...s-24006-3.html

[aardvarcus]

I also mounted Michelin 205/65R16 Energy Saver A/S tires on my Celica to help with the gearing, removing some non LRR 205/50R16s. Went from 24" to 26.5", noticably higher gearing on takeoffs. I did not do ABA testing, but on my commute I immediately noticed a over 10% increase in MPG with no other changes made. Tanks went from 29min-32max to 34min-36max. Look between January and Febuary on my fuel log. Only downside is light rubbing at 100% steering lock (95% is fine, just not 100%). Also my car was so low to begin with raising it 1" helps with scraping.