The advantage of bigger tyres?

[Crawford]

Hey, i am wondering what the advantage of wider and bigger tyres are..

wouldnt they just decrease the ammount of power you have? therefore offset any real benefit of them?

Bigger tyres ... require more power to spin

Let me know

cheers

[lay80n]

Put a bmx wheel and a skateboard wheel against a gutter, which one will roll up easier. Simple explenation right there. Also can increase approach and departure angle. Increase under diff clearence (only way to do this without portal setups. Lots more reasons too.
Layto....

[87suzi]

What he said



I thought it was self explanatory. Also if your talking about bigger as in wider, well then you know the advantages of going wider. Funny enough, larger diameter will also increase surface contact with the ground, ever so slightly but nevertheless.

[Crawford]

how many power does it really use for bigger tyres?

would it be extremely under powered if i put as big tyres as i could on it with no lift?

[christover1]

how many power does it really use for bigger tyres?

would it be extremely under powered if i put as big tyres as i could on it with no lift?

I ran 30" tires with no lift for over 5 years, with only a 1.0 litre engine, in a heavier LWB Sierra, and it was fine. There is a bit of loss, but with a lighter SWB and 1.3 you would be fine. Just my opinion of course.

christover

[derelict_frog]

In high ranges you loose a lot of power with bigger wheels on a sierra, but in low range you can go up to 31"s with no worries as long as they don't rub on anything. There is plenty of power in low range just cruising around.

[zookjedi]

depends if you have your diffs locked as well as that saps alot of power , and it also depends on the terrain you drive , if you run 31" tyres with standard gearing on rocks with at least one locker you'll go thru clutches real quick , zooks have a pretty tall low range as is and putting bigger tyres on with no gear mods makes it obviously worse . put bigger tyres on with no gear mods will make it more capable in the right terrain, but in the wrong terrain will make it worse that wearing 29" tyres

cheers Jai

[droopypete]

The advantage's of a taller tyre are as lay80n says
the larger the wheel the smaller the obsticle,

another one is that because your tyre diameter is larger the tyre lasts longer.

you also asked about width, and that is another can of worms
the wider the tyre the less pressure it puts on the ground, this is both bad and good,
let me explain,
a carton of milk holds a litre of milk and weighs about 1 kilo, if you wanted to hold a door open with one, you would stand it vertical, as its footprint when vertical is 3 times smaller than it would be laying down, it still wieghs 1 kilo no matter how you place it,
but when vertical it applys 3 times more PSI of downforce and is less likely of slipping,
this is an example of maximising downforce.

lets take that same milk carton and place it verticlly on some shag pile carpet (like the stuff Guy has in his bedroom )
and place another one laying down beside it, after 10 mins if we remove both, we will find that the vetically positioned one has left a deep impression in the pile of the carpet and the one laying down has hardly left a mark,
this is an example of maximising floatation.

to put it in an automotive perspective (I know some of you petrolheads have brains the size of peanuts )
if a car weighs 1000 Kilo's and is perfectly balanced (front to back/left to right)
each axle is supporting 500Kg and each wheel is supporting 250Kg, the front axle has 6" wide tyres and the rear has 12" wide tyres both are the same height, (anyone see were I am heading with this )

lets go for a drive in our full time 4x4,
first we go up a hill that is covered in shail and loose small rock, the front axle, with twice as much PSI of downforce applys twice the pressure and grips the surface where as the rear is spinning all over the shop!

wow that was fun! lets go for a drive down the beach, we find the front wheels sink in the soft sand because of that heigher PSI and the rear axle just floats over the top

lets go for a drive in the snow (this is a tricky one)
we find that the wide tyres use more power to push through the snow than the 6" ones, but the wider tyre has the benifit of not sinking in the snow as deep and indeed on occasion floating over the top

now I know StevieG will pipe in with a comment about the angle of the hill will place more weight on the rear axle or that the car in the sand had a Hyclone or something but you get what I am trying to say here.
Peter.

[cj]

Then of course you have the extra weight of a wider tyre to turn and the increased windage which will have an effect on the road and in the wet and reduced braking but good on rock. You also need to remember that depending on the terrain the wider tyre may have more mud, sand, snow etc. building up in front of it to push out the way. The taller but narrower tyre can actually have a bigger contact patch when aired down compared with a smaller wider tyre. As Pete said you need to look at the terrain you will drive and the size options you can fit. For example you may be able to fit a 31x10.5 or a 32x9.5 but not a 32x10.5. Which one is better? Depends on what you're driving.

[droopypete]

As Pete said you need to look at the terrain you will drive and the size options you can fit.

Tut, tut tut,
don't put words into my mouth
I never said that
I was only commenting on diferent widths of the same diameter.
don't want to sound picky mate, but tyre selection is a mine field and I am staying neutral.
as CJ says "you cant beat dunlop road track majors in any terain"
Peter.

[cj]

..... but you get what I am trying to say here.
Peter.

Obviously not

[cj]

as CJ says "you cant beat dunlop road track majors in any terain"
Peter.

[Beastmavster]

The actual power reduction is minimal - the increased frictional losses (at brakes, wheel bearings etc) due to the extra weight to turn.

Ther real "power loss" issue here is not the power loss per se, it's the consequences to gearing.

If you run 20% bigger tyres (eg 31" on a sierra/vitara), then the car will be running at 20% less RPM for the same gear and the same speed (oh your speedo will be out too by the way).

Example:
So if you used to do 2500rpm at 100kph you'll now be doing 2000rpm.

that probably means you will struggle to get up the same hill in 5th gear, or at least you'll press the accelerator much harder to get up it, using more fuel.

Effectively the power difference is like the difference in overtaking power between 4th gear and 5th gear (normally about 15 to 20% difference in most cars). Except it's more like an additional overdrive - 4th becomes 5th, but 5th becomes 6th.

With maybe 50hp to push it 6th gear = useless so you will probably drive on the highway more in 4th, using more fuel. You'll also use 3rd around town more and 4th less too.

If on the other hand you owned and old 4 speed troopy or MQ you'd probably love this effect....


Luckily if you own a sierra there's heaps of options to fix this relatively easily AND reduce your low range gearing as well, thus saving you the consequences of too high speed in low range (damage to car due to travelling too fast over obstacles, burnt clutches etc).

If you're a vitara owner this becomes a very expensive exercise, which is why I no longer own a vitara.