Tyres for better fuel consumption

[M V]

I own an Auris 2014 Hybrid. I drive on 225/45/R17 and my overall consumption is 4,7 l/100 km. I believe that if I had 195/65/r15 91H tyres, the consumption would be lower for 0,5  litres almost. What is your opinion about that issue ? Is anyone out there had changed the dimensions like above? 

Thank you

[FROSTYBALLS]

Moved to the Auris club

[TonyHSD]

Hi and welcome . You can’t change to 15” wheels because of the front brakes callipers size, smallest possible size that you can fit is 205/55 R16 , but in my opinion don’t change anything, just get quality tyres that are rated for low rolling resistance and quiet , Good Year Efficient Grip Performance are good example or  Kumho Ecsta HS51 if you are on a budget, and most importantly is to keep them to the right pressures, not much above or below max allowed . 

 

[HSDish]

I agree with TonyHSD and think the quallity of the tyres probably are more important than just size.

I swaped my orginal 225/45/17 91W Dunlop Sport Fastresponce ( E rolling resistance B wetgrip 69 sound in EU marking) on my Auris TS HSD 2014 for some used 205/55/16 91W (F rolling resistance C wetgrip 71 sound ) cause I was convinced that it would be better for fuel consumption and (ride) comfort but... there wasnt that big difference in neither fuelconsumption nor comfort.

Now I bought some new 205/55/16 94 XL GoodYear Efficient Grip Performance and hope for some improvement in both fuelconsumpion and comfort.

Have just driven them some 10km yet though

[dieseldane]

I went to Goodyear Efficientgrip Performance tyres (205/55 R16) but didn't really notice any substantial difference in MPG (previous tyres were Goodyears also).

[M V]

But the manual mentions the 15 ‘’ dimensions... what about the difference between 17’’ and 16’’ ?

[FROSTYBALLS]

On both the first and second generation Auris hybrids, 15 inch wheels/tyres were available on certain grades.

Lower profile tyres tend to be wider and have a bigger footprint - which can adversely affect fuel consumption.

As regards changing from 17 inch wheels/tyres to 15 inch wheels/tyres, one would need to be sure that the relatively small reduction in fuel consumption would justify the expense of the change. Also one would need to check with your insurer that they will accept the change, or whether they may charge additionally for the change to the car's spec.

[Gerg]

We have a 17" wheel Auris.  I have put 16" Toyota wheels on it.  These fit fine, but the gap between the rim and the brake caliper is really quite small.  The front brake calipers are definitely a different design, and bigger, than those fitted to a 15" wheeled Auris (which we also have).  The 15" wheels definitely don't fit over the larger brakes, I have tried, just to be certain.

When or if I get time, I will run both these cars around a short test loop to compare their fuel economy.  The cars are the same age and similar mileage, but one has done much more motorway mileage, so another known variable here beyond the less obvious ones.  I would have compared the 17" wheels to their 16" replacements from a fuel economy perspective, but there were so many other weather-related changes that it would not have been that meaningful. Also, the car is/was still freeing up after years spent with its previous driver, who was very, very careful!

The bigger brakes do have more feel than the smaller ones, but for the dreadful, crumbling, under-funded, speed-humped roads around here the 15" wheels are great, if less precise when cornering.

I noticed that back in the 2000s, you *could* buy a  3 series BMW or E-class Mercedes on 195/65 x 15 tyres, if you wanted to.   Has car comfort become less important next to performance, it seems so.  Perhaps that is one part of the appeal of some SUVs - fat tyres and a softer ride.

[HSDish]

On 4/11/2019 at 8:47 AM, Gerg said:

We have a 17" wheel Auris.  I have put 16" Toyota wheels on it.  These fit fine, but the gap between the rim and the brake caliper is really quite small.  The front brake calipers are definitely a different design, and bigger, than those fitted to a 15" wheeled Auris (which we also have).  The 15" wheels definitely don't fit over the larger brakes, I have tried, just to be certain.

When or if I get time, I will run both these cars around a short test loop to compare their fuel economy.  The cars are the same age and similar mileage, but one has done much more motorway mileage, so another known variable here beyond the less obvious ones.  I would have compared the 17" wheels to their 16" replacements from a fuel economy perspective, but there were so many other weather-related changes that it would not have been that meaningful. Also, the car is/was still freeing up after years spent with its previous driver, who was very, very careful!

The bigger brakes do have more feel than the smaller ones, but for the dreadful, crumbling, under-funded, speed-humped roads around here the 15" wheels are great, if less precise when cornering.

I noticed that back in the 2000s, you *could* buy a  3 series BMW or E-class Mercedes on 195/65 x 15 tyres, if you wanted to.   Has car comfort become less important next to performance, it seems so.  Perhaps that is one part of the appeal of some SUVs - fat tyres and a softer ride.

Very intressting! Please keep us informed.

Me myself have just changed to 205/55/16 94 XL GoodYear Efficient Grip Performance, A rolling resistance B wetgrip 68 sound in EU marking, (as said above) but I have to drive some more miles to get any usefull info.

[JGian]

I share TonyHSD's sentiments as well. Go for car tyres that can create less wheel resistance. Also, make sure that you regularly service your car and conduct a wheel alignment check at least once per year. Basic things can help you go far!

[PeteB]

On 4/11/2019 at 8:47 AM, Gerg said:

...Has car comfort become less important next to performance, it seems so.  Perhaps that is one part of the appeal of some SUVs - fat tyres and a softer ride.

On the current and previous Prius, the choice was 15" or 17".

A number of people on this board and others have said they liked the 17" ones because they "looked better".

I currently own the latest (4th) Generation, and previously owned the 3rd, both on 15".  I also on occasion drove versions with 17".

Those on 17" rims were generally noisier, gave a harsher ride (although less pronounced in the 4th Gen with it's improved chassis and suspension), larger turning circle (due to 17" being wider) and cost more to replace, in addition to being worse for CO2 and emissions.  In theory, with a much smaller amount of air/rubber between metal and road, they are more susceptible to damage from severe pot holes but I've not seen a single report of this happening.

I can't recall if this also applied to the Gen 3, but on the 4 it pushed the car into a different bracket for Benefit in Kind tax (making 17" much more expensive for company car drivers) and meaning only cars with 15" got exemption from the London Congestion Charge (although it no longer matters as from this month only zero emission cars and some plug-in Hybrids qualify).

[TonyHSD]

17” wheels are better option for motorway driving especially at higher speeds and much better at cornering, I mean not driving like crazy , just normal. If most of the times the car is used in town 15” are better, but if driven mostly on motorways 17” are best. I can live with both sizes, not problems for me. Most important are the right tyres not the size. Winter time with with tyres and summer time with summer tyres preferably or all season ones. Car with quality 17” tyres can ride better than car with cheap low quality rubbers in any driving conditions. Quality tyres can vary from midd range to high end, also the type of the tyres very important. 17” at 45 profiles many of the tyres are “UH” ultra high performance tyres suitable for sportier driving styles and not good at all for a hybrid cars, many ppl don’t realise that and buying those tyres than get noisy and bumpy ride, plus worse fuel economy. Also the OEM tyres are not always the best option, despite the car came originally equipped with them, doing an extended research prior to buying a new set of tyres pays off afterwards . 

Regards 

[Alan1234]

If your only worry is for fuel economy the pump your tyres up to 50 psi ,everything else will be aweful but it will roll better lol.

[tommy59]

Take a look at the label grading of the tyres. If 17" 16" and 15" standard load tyres all have the same RRc grading they will all be basically the same for economy. Extra load tyres are measured with a different procedure and an "A" graded XL tyre will be worse for economy than an "A" graded standard tyre. 

[FROSTYBALLS]

25 minutes ago, tommy59 said:

Extra load tyres are measured with a different procedure

Disagree. The EU tyre labelling testing process is intended to provide a comparison between tyres to enable the owner to choose the best tyre for their requirements. Using a different process for XL tyres will provide non-comparable data.

The process is described below:

EU tyre label - how the tyres are tested

Since June 2012, tyre manufacturers have been required to provide data in relation to the performance of their tyres through testing.

Due to the sheer vast number of tyre models, it was decided that a centralised EU tyre testing facility would be unmanageable and unproductive. Therefore, tyre label testing is self-certified using specific EU standardised methods that every test must adhere to.

Testing Rolling Resistance

A tyre is mounted to a specially designed two-metre drum. It is then rotated with a defined load and pressure.

The test engineers have the torque required to rotate the drum before the tyre is fitted, so they are able to calculate the torque of the tyre by subtracting the new level required when the tyre is mounted against the level when it is not.

It is through calculating the difference of the drum's torque with or without the tyre that they can record what is known as the 'Rolling Resistance Coefficient'. This is what is used to work out the correct grading for the new tyre label.

Testing Wet Grip

There are two tests that engineers are required to carry out to come up with the wet grip rating.

First of all they need to carry out a wet braking test. This measures the performance of a tyre when a vehicle is braking on a wet surface. The distance that the car travels when slowing from 50mph to 12mph is recorded.

They also carry out what is known as a skid trailer test. This calculates the friction between the tyre and the road surface. For the tests to be valid, it must take place when the vehicle is travelling at 40mph.

Once they have both results, they combine them to create the Wet Grip Index (WGI) - this shows the percentage of improved ability compared with an independent reference tyre.

Testing Noise Emission

This test is done to find out the external noise of a tyre in decibels (dB).

The actual test consists of a microphone being set up on the edge of a track to measure the sound level of a test vehicle - the microphone is required to be 7.5m from the centre of the track at sit at 1.2m above the ground. When passing, the vehicle must be travelling at 50 mph with the engine turned off for the test to be valid.

[tommy59]

17 minutes ago, FROSTYBALLS said:

The process is described below:

Testing Rolling Resistance

A tyre is mounted to a specially designed two-metre drum. It is then rotated with a defined load and pressure.

The test engineers have the torque required to rotate the drum before the tyre is fitted, so they are able to calculate the torque of the tyre by subtracting the new level required when the tyre is mounted against the level when it is not.

It is through calculating the difference of the drum's torque with or without the tyre that they can record what is known as the 'Rolling Resistance Coefficient'. This is what is used to work out the correct grading for the new tyre label.

While this is technically correct, it omits some of the procedure.

The "defined load and pressure" is as follows:

Load - 80% of the tyres maximum loading capacity

Pressure - 210kpa for standard load tyres and 250kpa for extra load tyres

This higher load and pressure actually skews slightly in favour of the XL tyre in terms of lower RRc values. If you tested an XL tyre as if it was a standard load version the RRc performance would be marginally worse and would be labelled as such. 

[FROSTYBALLS]

The defined load and pressure is a setting rather than a different procedure.

[HSDish]

Now I’ve driven about 700km (434 miles) with my new 205/55/16 94 XL GoodYear Efficient Grip Performance, 205/55/16 94 XL GoodYear Efficient Grip Performance, A rolling resistance B wetgrip 68 sound in EU marking on our Auris TS HSD 2014 ,,,

but I dont think there is as big differece in fuel consumption and comfort as I hoped for, compared to the 205/55/16 91 V Continental Conti Premium Contact 205/55/16 94  F rolling resistance B wetgrip 71 sound in EU marking (on front) and 205/55/16 Superia RS 300 91H F rolling resistance E wetgrip 69 sound in EU marking (on rear),

just experience a slight improvement in fuel consumption and comfort.  I even exoperienced (possibly delusion) that the new tyres needed to acclimattize a to perfom at its best (hopefully bee better and better 😊 )

 

I Think finding the best tyres for different needs and performance, is like a djungle. A bit like different strings to an musical instrument

[FROSTYBALLS]

The following tyre fuel efficiency calculator can be interesting: https://www.willis-owen.co.uk/tyre-fuel-efficiency-calculator/

For my Aygo the current Continentals are C for rolling resistance. There don't seem to be any B rated tyres in the Aygo's size, but if there were, and I changed all four tyres, the projected fuel saving would be a total of £8.85 annually (4,000 annual mileage).

[dieseldane]

On 5/3/2019 at 8:09 PM, HSDish said:

Now I’ve driven about 700km (434 miles) with my new 205/55/16 94 XL GoodYear Efficient Grip Performance, 205/55/16 94 XL GoodYear Efficient Grip Performance, A rolling resistance B wetgrip 68 sound in EU marking on our Auris TS HSD 2014 ,,,

but I dont think there is as big differece in fuel consumption and comfort as I hoped for, compared to the 205/55/16 91 V Continental Conti Premium Contact 205/55/16 94  F rolling resistance B wetgrip 71 sound in EU marking (on front) and 205/55/16 Superia RS 300 91H F rolling resistance E wetgrip 69 sound in EU marking (on rear),

just experience a slight improvement in fuel consumption and comfort.  I even exoperienced (possibly delusion) that the new tyres needed to acclimattize a to perfom at its best (hopefully bee better and better 😊 )

The link Frostyballs posted says "There is a 7.5% reduction in fuel consumption between G-rated and A-rated tyres", so with all the other factors in play it'll be a while until you see a systematic difference (if ever?) between a B/C tyre and an A tyre. When I went from my winter tyres to the GoodYears the fuel consumption clearly went down though (from about 5.2l/ 100km to 4.7l/100km).