265/65/16 and fuel economy

[Troutnut]

Hi all,

I just changed the tyres on my 2010 d40 Thai auto from the standard 255/70/16 to a set of 265/75/16 Hankook Dynapro M/ts. The fuel economy prior seemed good, was getting 600+ kms to a tank. I have only just brought the vehicle so didn't do lots of testing before changing the tyres. I notice when I changed them that there was a bigger loss of power than I expected. I seemed to loose about 100kms per tank (500kms a tank). I then fitted a ARB bullbar and winch and on this latest tank I think I will be lucky to get 450kms. I drive as economical as possible ( revs below 2500) and this is combination driving of in the city and out on the highway.

I love the tyres by the way and the extra clearance they give, but I must admit I am thinking about trading them back in on some 265/70/16 AT tyres to see if I can improve my economy. I do a lot kilometers each week and chase the fish on the weekends so can do up to 600kms a week.

Others things I thought of trying first were:

blocking the EGR port.

Resetting the ECU

Cleaning the Airflow sensor

Can anyone offer any advice here on ways to improve the economy, I really need to get it back up around 550-600 or at the very least 500kms to a tank. I am worried that if I swap tyres that I may not get that much improvement and I love the tyres. Has anyone been through a similar experience? I don't know if changing the exhaust may help or removing the Catalytic converter may also help or even fitting a snorkel may make some small improvement.

Cheers

Troutnut

 

[ShortyNavros]

Your standard tyres were probs 8 ply and less. The Hankook MTS are Lt tyres (10ply) I believe and you also went larger in diametre. On my car the weight difference between the kuhmo kl78 passenger rated 265/70/16 tyre and my new 265/75/16 yoko geolandars was about 4.5kg per wheel, wheel mass is not like normal weight it is called unsprung mass. Ie more energy is require to spin not only a larger but also heavier tyre. This is the price you pay for getting chunky tires which are resistant to chipping and punctures. Also you went from what I assume was a road or h/t tyre to a mud tyre. The compound is softer, tread is deeper and hence causes more friction on the road in the end translating to worse economy.

You are likely making your economy worse by not accounting for your larger tyres as well. Like the circumference difference between my old 265/70 and my new 265/75 is about 3% so when you get your final kms on a tank you really need to multiply that figure by 1+ the extra percentage of how much bigger the tyre is, in my case I multiply by kms by 1.03

 

[Troutnut]

Thanks Shorty,

I had an idea that the bigger tyres would travel further every revolution but didn't know how to work it out exactly. Followed your help, with the bigger tyres being about 5% bigger and at 500kms it adds 25kms to distance travelled.

Can I ask if going from your 265/70/16 to 265/75/16 has made much difference to your economy? Which size do you prefer on your Navara?


Cheers

Lincoln

 

[happy john]

There is plenty of comparisons between those two tyre sizes on the below link, though it's mainly D22 chat it should give you an idea of peoples thoughts of the difference on road and scrub between the two.
http://www.navara.asia/showthread.php?t=5575

 

[Gbt]

Do an ECU reset, that should sort out a bit of the issue.

 

[308bever]

what`s an ecu reset?

 

[jonney]

what`s an ecu reset?

Just disconnect the battery for 10 minutes then re connect, thats it.

 

[308bever]

wow, that`s easy, what does that do for anything though?

 

[Gbt]

It puts the engine back into a learning mode. Follow this http://www.blue-print.com/techtip/navara/ and go for a 20min drive.

 

[steel d40]

After 8 years and 3 different tyre sizes have found 265/70/16 to be the best compromise yet for fuel economy/clearance. I do a lot of road K's and these give me better than 9l/100km economy and still capable off road. If I was rock crawling more often I'd still want the 265/75/16 MTZ's but for what I do these are perfect. They are L/T construction too, haven't had a puncture yet. Also seem to suit my utes gearing better than 255/70/16, not as prone to rev it's ringer out for no speed.
Another note is the rolling resistance of mud tyres, an A/T tyre just rolls better due to the less aggressive tread. Better roll = better fuel economy.

 

[Chris C]

After 8 years and 3 different tyre sizes have found 265/70/16 to be the best compromise yet for fuel economy/clearance. I do a lot of road K's and these give me better than 9l/100km economy and still capable off road. If I was rock crawling more often I'd still want the 265/75/16 MTZ's but for what I do these are perfect. They are L/T construction too, haven't had a puncture yet. Also seem to suit my utes gearing better than 255/70/16, not as prone to rev it's ringer out for no speed.
Another note is the rolling resistance of mud tyres, an A/T tyre just rolls better due to the less aggressive tread. Better roll = better fuel economy.

Agree 100%.

I had stock tyres last 30,000km and average 7.8 lts 100 (stock car)
I put on Maxxis bighorns, 265-70-17, fuel use went up by 1lt per 100, even with the extra dia taken into account.

Fuel use went up a further 1 lt per 100 with the addition of the bullbar.

Now have Hankook 265-65-17 AT, the new design ones, with ARB bar, winch, lights etc still sitting on 8.1 lts per 100 inc speedo correction etc for different dia, drive is better, still good off road, still good clearance (I have a 60 mm lift all round)

My car now has 176,000 and has averaged 8.1 lts per 100 for the past 44,000 km, I don't drive it like a nanna either, its on or just over the limit, lots of 115 kph time to and from work on expressway.

Tyre pressure is also a big factor as the speed increases, not such a huge difference around town, but get on the highway and you can make .5-.8lt per 100 difference with a few psi.

My fuel light comes on at 865 km every time, runs out at 965 km without fail, I carry 10 lts with me at all times.