Tyres mpg

Forum for wheels, tyres, suspension, chassis, brakes
F1 Bob
Posts: 546
Joined: Sat Mar 22, 2014 12:26 pm

Post by F1 Bob »

I know that the tyres we use can impact on mpg but had never appreciated just how much difference a change of tyre can make.Last week I removed the 19" wheels with Continental tyres and fitted my 17" winter wheels fitted with Dunlop Winter Sport 4D tyres on our 2014 1.5 dci Tekna. My mpg has now improved by around 6 mpg and on one or two longer runs by almost 8 mpg. I had been expecting the mpg to drop off with the winter tyres not to improve. When the time comes to replace the Contis I will do a lot more research and hopefully there will be a wider tyre choice for the 225/45 R19 by then.
Pulsar 1.5 dCi Tekna in Bronze

supergrover
Posts: 396
Joined: Sun May 04, 2014 5:23 pm

Post by supergrover »

Blimey. That's interesting. I'd like to know if that persists as time goes on. The Contis fitted to the Acenta rims are supposed to be the Eco ones, but when the time comes to replace them, I'll first have to check if I get my choice of brand, (it's on Motability) and then do some research.
1.5dci Acenta Black with Smart Vision and DIY Chrome Pack
MJCQQ
Posts: 136
Joined: Sun Oct 12, 2014 8:54 pm

Post by MJCQQ »

A lot of this will be due to smaller wheel and thus less rolling resistance. Larger wheels have more mass and as a consequence it requires more energy to get them moving. It is offset somewhat , though not entirely by the fact they have larger inertia. 7%-10% difference between 17" and 19" rims would be expected.https://my.news.yahoo.com/does-size-rim ... res-tested
MJCQQ2014-11-15 11:29:40
supergrover
Posts: 396
Joined: Sun May 04, 2014 5:23 pm

Post by supergrover »

Oh. Thanks for the links MJCQQ - but I think my wheels are small enough already
1.5dci Acenta Black with Smart Vision and DIY Chrome Pack
MJCQQ
Posts: 136
Joined: Sun Oct 12, 2014 8:54 pm

Post by MJCQQ »

Yeah, any smaller than 17" and the QQ wheels look very wrong. 17" is about as small as they can get while still looking OK.I had looked into getting some new Wolfrace Scorpio 18" alloys with decent tyres (Hankook or better) and it would cost me ~£850-£1000. IMHO 18" is a good compromise as my experience with the QQ on 19" tyres was OK but not great. I am waiting a few weeks to see if my hankering subsides. My usual cut off where I care how my car looks is about three months from new. I know this is a VW van but the wheels are the ones I am getting an urge to purchase. IMHO it would look better than the stock Nissan 17" rims without trying to emulate the Tekna look.http://www.vwt4forum.co.uk/picture.php? ... eid=144035

MJCQQ2014-11-15 14:28:56
montimar
Posts: 153
Joined: Wed Apr 09, 2014 7:08 pm

Post by montimar »

What an interesting post. Even at my age you learn something new every day. It also explains why my Acenta with bog standard 17" wheels gets better fuel cons than most of the Tekna owners.
April 2014 Acenta 1.6 Xtronic Blade Silver
MJCQQ
Posts: 136
Joined: Sun Oct 12, 2014 8:54 pm

Post by MJCQQ »

A few of the younger guys at work are really into their cars. They were chatting about alloys and both of them pointed out that large 19" or 20" rims were purely for bling. If you are in it for 0-60 performance then lightweight lower size rims are better.
Deleted User 1571

Post by Deleted User 1571 »

Lots of misconceptions here. No matter what the diameter of wheel fitted to the Qashqai, the diameter of the tyre remains constant to within a few millimetre. The larger the wheel, the wider the tyre and the lower the profile so as to keep the speedometer accurate. So it follows that the wheel diameter is not directly responsible for any fuel consumption difference.What does make a difference is the width of a tyre, both in rolling resistance [which should be at least partly compensated for by stiffer sidewalls"]] and wind resistance.
gvmdaddy
Posts: 2245
Joined: Thu Jun 19, 2014 11:28 pm

Post by gvmdaddy »

Tyre wear is also a factor. A brand new tyre on a 19" wheel will give approx 2-2.5% more mpg than a tyre worn to near its legal minimum. The same would also apply to other wheel sizes. It is not an exact science though as there are other factors as mentioned by Quacker above.
MJCQQ
Posts: 136
Joined: Sun Oct 12, 2014 8:54 pm

Post by MJCQQ »

[quote="Quacker"]Lots of misconceptions here. No matter what the diameter of wheel fitted to the Qashqai, the diameter of the tyre remains constant to within a few millimetre. The larger the wheel, the wider the tyre and the lower the profile so as to keep the speedometer accurate. So it follows that the wheel diameter is not directly responsible for any fuel consumption difference.What does make a difference is the width of a tyre, both in rolling resistance [which should be at least partly compensated for by stiffer sidewalls"] and wind resistance.[/QUOTE]The overall wheel and tyre size combined size stays largely the same, so to compensate for the smaller sidewalls the tyres need to be reinforced. Overall as wheel rim size increases, so does the overall weight of both. In the test I linked to above the 17" and 18" tyres were exactly the same width but the wheel/tyre weight was 3lb heavier. That even minor increase in weight does increase the rolling resistance enough to increase fuel consumption by ~5%.Of course it is not the only factor but it as a significant factor as both tests I linked to show.
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