TYRE WIDTH/TYPE VS FUEL CONSUMPTION

[Tony]

Ok guys, here's an interesting one regarding all the hype about tyre width and HT / AT / MT's and their related fuel consumption.
So ..... Wider uses more fuel - correct?? AND MT's use more than AT's, which in turn use more than HT's - this is a fact .... right??
Ok, here's what I have found out on my last two runs down to the W/Cape. You guys all know my GU - it came with BFG 305 65 17 KM2 muddies. I drove down in December on these tyres and had a blowout on my return trip and promptly replaced all 5 tyres with Cooper STMaxx's these are classified as AT's and I went a little narrower i.e. 285 70 17. Last month I drove down again on the new ones, both trips were towing a trailer. In December we were 4 up inside with a number of light items on the roofrack as well as a bicycle lying on top of the trailer. Last months trip we were 2 up inside and nothing on top.
Here are my findings:

Jhb to Hanover (BFG MT 305's) ODO = 669.10 GPS = 712.10 Litres = 134.72

Jhb to Hanover (Cooper AT 285's) ODO = 672.10 GPS = 715.15 Litres = 133.24

Is this a "busted myth" or what!!

[Rodney]

I am no expert but lots of small things make a difference.

I have a 2000 Citroen C3 diesel that comfortably does 20km on 1 litre at 130/140km/h. But hit the southwester or southeaster near Cape Town and that easily drops to 16/17 km litre.

I have noticed on my Y61 3.0l that a side or front wind whilst the roofrack is on( but empty ) noticeably negatively affects my consumption travelling for about 125 km on the same route on a regular basis. When I turn around and travel mostly with the wind consumption back to normal. So I remove the roofrack for daily travelling (absolute schlepp).

[Alex Roux]

I moved from 33" (Muddies) to 31" (ATs) on Shortie.
They are narrower too.
Highway consumption improved from 6 km/l to 7 km/l.

[Peter Connan]

I went from 33x12.5 AT's to 32x11.5 Muddies to 265/70R16 HT's to 255/85R16 muddies.

No repeatable difference in fuel consumption, except in soft sand, where the narrow tyres have a noticeable advantage.

[Tinus lotz]

Check asb net eers julle odo teen julle speedo met verskillende bande julle sal skrik ..my bakkie meet 9% onder met 285 75 16 teen die speedo ...maw die odo wys 100km en gps wys 109

[SJC]

Ok guys, here's an interesting one regarding all the hype about tyre width and HT / AT / MT's and their related fuel consumption.
So ..... Wider uses more fuel - correct?? AND MT's use more than AT's, which in turn use more than HT's - this is a fact .... right??
Ok, here's what I have found out on my last two runs down to the W/Cape. You guys all know my GU - it came with BFG 305 65 17 KM2 muddies. I drove down in December on these tyres and had a blowout on my return trip and promptly replaced all 5 tyres with Cooper STMaxx's these are classified as AT's and I went a little narrower i.e. 285 70 17. Last month I drove down again on the new ones, both trips were towing a trailer. In December we were 4 up inside with a number of light items on the roofrack as well as a bicycle lying on top of the trailer. Last months trip we were 2 up inside and nothing on top.
Here are my findings:

Jhb to Hanover (BFG MT 305's) ODO = 669.10 GPS = 712.10 Litres = 134.72

Jhb to Hanover (Cooper AT 285's) ODO = 672.10 GPS = 715.15 Litres = 133.24

Is this a "busted myth" or what!!

I had 255/85r16 on both my patrols previously (st maxx & dunlop mt2's), currently got a second hand set of 285/75r16 BFG km2's on.
My consumption is slightly more with the current set, maybe 0.3km/l more. not 100% sure.

Got better fuel consumption with the dunlop mt2's, than with the st maxx's. (there goes the at give better fuel consumption than mt theory.. ) The MT2's got quite an aggressive mt threat/pattern compared to the st maxx's.. But they are slightly narrower than the st maxx's although it is theoretically the same size tyre.

IMG_3098.JPG (424.39 KiB) Viewed 7135 times

But as Tinus said, double check the odo compare with gps distance traveled. These two sizes are not the same diameter tyre.

[mvcoller]

The OP compared 285/70 x 17 with 305/65 x 17

when comparing the two, the OD size for each size is:
305/65 - 828.30mm or 32.61"
285/70 - 830.80mm or 32.71"

So the size is very similar, the 285/70 is 2,5mm (or 1/10th on an inch) taller than the 305/65. I bet you if you fit new tyres, after just 5000km, that will be the OD difference between your front and rear tyres. It is really insignificant.....

[Jules]

Please explain this

Jhb to Hanover (BFG MT 305's) ODO = 669.10 GPS = 712.10 Litres = 134.72

Jhb to Hanover (Cooper AT 285's) ODO = 672.10 GPS = 715.15 Litres = 133.24

Is the 669.10 GPS the kilometres travelled and 712.10 Litres used to travel that ???? what then is the 134.72 ??

Shalom

[Picasso]

Please explain this

Jhb to Hanover (BFG MT 305's) ODO = 669.10 GPS = 712.10 Litres = 134.72

Jhb to Hanover (Cooper AT 285's) ODO = 672.10 GPS = 715.15 Litres = 133.24

Is the 669.10 GPS the kilometres travelled and 712.10 Litres used to travel that ???? what then is the 134.72 ??

Shalom

Well.. I understood it in the following way

BFG
The distance traveled indicating on the trip meter (ODO) was 669.1 km
The actual distance traveled according to the GPS = 712.1 km
The difference between ODO and GPS is most likely due to the bigger Tyre diameter ~ 6 %
The fuel consumed over this distance was 134.72 liters or between 19 and 20 Liters / 100 km depending on km reading.

same principle for the Cooper tyres

[iandvl]

Please explain this

Jhb to Hanover (BFG MT 305's)

ODO km = 669.10
GPS km = 712.10
Litres = 134.72

Jhb to Hanover (Cooper AT 285's)

ODO km = 672.10
GPS km = 715.15
Litres = 133.24

Is the 669.10 GPS the kilometres travelled and 712.10 Litres used to travel that ???? what then is the 134.72 ??

Shalom

I understood it as I highlighted it above.