17 inch wheels
 

I was using 3% oversize tyres on 15" rims before and was getting good MPG but Auckland has a really wet winter. I actually put in 17" work wheels with Federal Supersport tyres and of course the MPG dropped. Is there a way to ecomod with the use of 17 inch wheels?

I know Bridgestone Ecopias have 215/45R17 tyres but do they really aid in MPG gains? I'm not really sure if I should give these Ecopias a go.

What are the circumferences of each wheel? These numbers could be used to correct odometer readings, thus geting more accurate FE readings.

1. Depending on how many miles you drive hwy speeds and how many are in town, you may have crossed the line in the trade off
2. Each extra unit of measure (pounds etc) over the factory weight of the tire/wheel is multipled by 4. So now you need more energy to start (gas consumption) and more energy to stop (brake and suspension wear and tear.)
3. if each 17 inch setup weighs just 5lbs more, then the effect of that 5lbs spinning around is 20lb per tire.
4. withuot knowing the size of the 15 inch tires it is impossible to determine anything. Maybe your 17s are actually wider but not as tall as the 15s.. who know????

Here are the specs of the stock 14s 195/70R14

Section Width: 7.67 in 195 mm
Rim Diameter: 14 in 355.6 mm
Rim Width Range: 5.5 - 7 in
Overall Diameter: 24.74 in 628.39 mm
Sidewall Height: 5.37 in 136.39 mm
Radius: 12.37 in 314.19 mm
Circumference: 77.72 in 1974.0 mm
Revs per Mile: 840.7
Actual Speed: 60 mph 100 km/h

These are the specs of my 15 inch wheels 205/65R15

Section Width: 8.07 in 205 mm
Rim Diameter: 15 in 381 mm
Rim Width Range: 5.5 - 7.5 in
Overall Diameter: 25.49 in 647.44 mm
Sidewall Height: 5.24 in 133.09 mm
Radius: 12.74 in 323.59 mm
Circumference: 80.07 in 2033.7 mm
Revs per Mile: 816.0
Speedometer1: 58.2 mph 97.0 km/h
Speedometer Difference: 3.026% too slow
Diameter Difference: 2.95%

And the 17s: 215/45R17

Section Width: 8.46 in 215 mm
Rim Diameter: 17 in 431.8 mm
Rim Width Range: 7 - 8 in
Overall Diameter: 24.61 in 625.09 mm
Sidewall Height: 3.80 in 96.52 mm
Radius: 12.30 in 312.42 mm
Circumference: 77.31 in 1963.6 mm
Revs per Mile: 845.1
Speedometer1: 60.3 mph 100. km/h
Speedometer Difference: 0.523% too fast
Diameter Difference: 0.53%

These are all from 1010tires.com
I'm actually doing the speedo correction on my fuel log.
The 14s are the steelies and they are the lightest ~ 16 kg
the 15s are 17 kg
the 17s have very heavy tires on them.

My hypermiling is pure city by the way.

Ive been running a 5 door 97 diesel Suzuki vitara here in the UK for some 4 months.
The previous owner had 215/45/16 tyres on it. The first thing I did apart from repair the crash damage(another story) was to fit 185/75/16in 8ply commercial tyres, these are for Ford Transit vans and can be run up bto 60 psi.
However I run mine at 40. They have a much lower rolling resistance that the original ones and its always been the case that skinny tyres are more efficient than low profile wide section ones.
If your driving for economy, then you dont need lots of grip so skinny tyres will do just fine.
Im getting for a kerb weight of 1.5 ton 40 mpg running around, 46 on 70/30 motorway/urban stop start driving, and expect to get 50mpg on a steady 55mpg on motorway use.
thats using BP ultimate50/50 with bio diesel.
The next step isto fit a temp controlled electric fan .
Have the fan but havnt found the electronics to vary the speed dependent on temperature.
At the moment its all or nothing!!.
Keep us posted here for your thoughts.
Dont buy the low profile wide tyres. They eat energy.
Ted
In Dorset
UK.

The 15" are likely your best compromise between handling and fuel economy.
If you're going all-out for FE, chose the narrowest tyre you can fit.

Do you get any snow down there in winter ?
If you do, I'd go for the 14" wheels in winter.
If you don't , chose a low rolling resistance tyre that you can drive all year long.

They didn't in the ADAC.de testing - in 185/65 R 15 H , tyre performance can change a lot with different sizes though.

I do wonder though why you went for wider tyres in winter.
Narrow tyres perform better in snow and rain, whereas the bigger ones just add drag and tend to float.

(I've been suffering up to double the normal dry fuel consumption while driving in a downpour last week. Rain kills your FE.)

I chose the wider track tyres because our winter here in Auckland is very, very wet. My car understeers a lot with the 15s.

If it's behaving better with the 17" tyres, it's down to the tyre quality, not the size.

If you're looking into low rolling resistance tyres, the Michelin Energy Saver doesn't handle or brake all too well in the wet - but in the end it all boils down to what you're used to, I'm comparing them to rather sporty tyres.


BTW : That Toyota Scepter looks a lot like a Camry over here ;)

Hmmm. I may have to consider what you have said about the Energy Saver (LRRs). Traction is very important here in NZ as we have a lot of bends and corners especially in the countryside.

I might just have to adjust my (city) hypermiling with these sticky tyres during winter.

>>>Yes the Toyota Scepter is very similar to a Camry. It's the JDM version of the camry with heaps of extras and electronics installed. It also has a slightly more powerful engine than the Euro and US models.

With the Energy Savers, I won't do any spirited driving in the wet.

Power application while cornering is below par in the wet.
To my liking, the front tyres often skid a bit too wide on my usual on-ramp of the motorway (which I take at around 60 kph in the wet) when going on the throttle past the half-way point of the corner.
The rear tyres follow without a problem though.