Originally Posted by
joel0407
consumption. Then maybe by changing out diff or tranfer box ratios we would maintain fuel consumption.
As above, it may improve it may not. Depends on a lot of factors.
In theory the larger wheels would have a lesser flex angle on the road so less flexing of the tread would mean less heat, longer tyre life, less resistance and better fuel consumption.
Dodgy logic. Heat vers traction on road tyres is a small factor, Block distortion and air pressure are by far greater factors. If you run a heavy loaded vehicle with tyre monitors you soon learn that heat is a big issue in normal rd tyres. A larger tyre will require less pressure for the same weight and dissipate heat better. Rubber will literally fly off a normal road tyre if it over heats. I've also seen normal road tyres get sticky with surface of the rubber looking just like hot racing slicks.
1 over dia will load up the motor, increase fuel consumption. As I said before I think the change in ratio from tyres is marginal.
2 Under dia, over revving the motor moves it out of its best rev range
3 Wheel weight, or unsprung weight, has similar effects as bad shocks, worse consumption.
4 Wider tyres, may or may not increase decrees traction, depends on pounds per square inch and actual optimum compound.
5 Wider tyres, increasing the foot print will increase fuel consumption I totally disagree. The foot print will become wider but shorter at the same time meaning it will remain the same. It's a fallacy that wider tyres give more grip or a larger contact patch.
6 Low tyre pressures will increase foot print, increase fuel consumption, see No5 The foot print will increase in length far more than width. The increase in length increases the angle the tread meets the road, increases tread flex and therefore increases heat. All which increase drag.
7 Lower tyre pressures, reduce rolling dia, may or may not affect fuel consumption, but is a mute point since No6 will out weight it in effect.
Best fuel consumption tyres are skinny as hell bald and pumped up to like 200000000 psi Skinny for less wind drag, high pressure and large diameter for minimal angle the surface of the tyre meets the road.
Worse fuel consumption is soft compound, 8ft wide and running 0.00003 psi
The ideal is some where in the middle
Race cars use wider tyres but they gain the advantage of longer life and more durability which means they car run a softer compound and acheive the same tyre life.
Nope sort off. Race cars work on a forulur. Distance, grip weight. = compound with weight. And heat of the day loading etc Yep and then they will run the widest tyre the rule will allow (on road) for the best durability. The formula is to calculate the compound.
In normal road vehicles by fitting wider tyres we actually get less grip because the tyres will heat up less which means the rubber will stay harder and provide less grip but they will last longer. Not mentioning aquaplaning as I think most will be aware of this.
Nope
Forget about heat in road rubber, it’s a small issue. Manufactures spend a lot on R&D to get rid of heat. Wider tyres = less grip only if the foot print is over the ideal pounds per square inch for the compound. So bigger is not always worse. Way to big is just as bad as two small Yes they spend a lot on R&D and while different size tyres of the same model will have a different construction they rarely vary in compound because general public don't worry about stuff like this like we do.
Maybe it's the wind resistance of the larger tyres that causes the extra fuel consumption.
Yes if you have exposed wheels. Like a F1 car. See the elfin? cars of the 70s
You also need to look at the relationship between body and wheels. Big topic minor effect See my previous post and follow the link. A care like the Honda CRX has very little wheel exposure but a 20mm wider tyre changed the CD of the entire vehicle by near 10%.
All this thought has come about because I just like the look of bigger tyres. Not too big, nothing like 37" or anything but about 32" is a good look on a 4x4 just my personal preference and as I said about the bigger size will last longer. But I don't want the extra fuel consumption so if I change my transfer box ratio to maintain the original gearing will my fuel consumption stay the same.
You have a d2 TD5, and you want to run 32” rubber. You are in the NT so mud can be an issue.
Ok assuming you are going to run with a mud. The difference between 29” mud and 32” is minimal. If you were changing to 32 from 29 mud, probably 20-30 klm a tank. If you are changing from 29 road rubber maybe 60 klms a tank If you read any of my posts in previous threads you will find I hate statements of km per tank. It's the most irrelevant measurement of fuel consumption ever quoted.
29 X 3.145 = 91
32 X 3.145 = 100
9% so I would say given the same with, wind drag on the body is the biggest consumer of your fuel Yes, I agree this is likely the case with the 4x4 bricks we drive but wind drag is greater than we might think.
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Tyres do make a difference.
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