Thread: Narrow tyres V Wide tyres

Originally Posted by mcrover

It is not just myself that gets sick of people hyjacking threads in the tech section for nothing other than to start an opinion bashing from one to another member.

THat is why I put in a guideline of just responding with your own tyres and thoughts of them and not to sway from that so it didnt end up like this.

If you see that as being Nazi like then I suppose my Jewish family and freinds as well as my employers would be very disapointed in me.

If you want the nature of conversation then the general chat section is for you but if you want to follow the nature of a thread in the tech section the your more than welcome to.

There has been a few very colourful rants about hyjacking threads especially in the tech section of late and I suppose this has become mine.

It was posted clearly at the start of the thread, repeated a various times throughout the thread and then I have bumped the original post so that everyone could see it again why I wanted to keep this thread on track but now I wish I hadnt started it.

If a question is asked then if you post in that thread then post an answer to the question as one day you will be searching for some information and having to wade through 500 pages of irrelevant drivel that has no relevence to the question or the subject that the thread was originally intended and you will hopefully then think back to your post in here and realise what I was going on about.

I am glad you started this thread because some of the opions have got me and I am sure others thinking. For the record I run or am about to get 245/75/16 AT's for my D2.

At the risk of being flamed by someone I am posting the following for people's thoughts and comments. As one of the less techicnal ones on AULRO, I got thinking the majority of road going race cars run fat tyres. Just about every light 4wd military application around the world runs skinny tyres except for the US with the hummer however a H1 was designed to be wide enough to follow in the tracks of the Abraham tank ( think that's how you spell it ). Which is alot bigger than the average 4wd. That's a pretty good arguement for fats being better for the tar and skinny's being better off-road.

Just my 2 cents worth.

Originally Posted by mrapocalypse

Oh come on blokes, a skinny vs Fats thread is gunna do exactlly what a Jap V Rover debate is going to do!

4 fifths of FA!

If you want a definitive answer, borrow a set of Skinny tyres, and GO FOR A DRIVE, then bolt a set of fatties on, and GO FOR A DRIVE.... and then post your OPINION up here - cos a forum is a place of opinion, like it or not.... especially with issues like this.

Peace!

Been there, done that- or close to.
I had a brand new 1976 Nissan Patrol with bog 7.50 x 16 tyres and a mate had an exact same model with "widies" dont ask what brand or size, but he did have spoked wider wheels.
We did a number of tests and the one worth mentioning is we ran up to 100 klm/hr ( I beat him evertime) side by side on a deserted road and both then cut our engines and rolled to a stop. I usually went 20 or 30 metres further, indicating the roll resistance was a liability with the wider tyres. Steering was understandably heavier too - no P.S.
Remember, this was two vehicles under 1000k on the speedo and we both were interested in comparing.

I posted earlier that I use skinny 7.5x16's on George. One of the reasons I use them is the absence of power steering, but also because of the potential for increased stresses on wheel bearings, diffs, prop shafts and universals, and TC/gearbox that could result in breakages and excessive wear. The other thing, tyres are half the price of widees (I just use cross plys - Firestone TTs). Choosing the right tyre pressures for the conditions means I haven't needed to be towed, much

I like this thread, anyway my thoughts are this;

If for instance your in soft sand or mud, to get good traction you need a long footprint not a wide one, especially when you let your pressures down, a wide tyre will balloon more than a skinny tyre thus creating more resistance, would this be correct.

I look at rally cars, i know not a 4WD as such but still a 4wd, if the conditions get soft (ie) mud soft gravel sandy, snow and ice, they go to a skinny tyre with a more open tread, shouldn't the same princpal apply for us.

Baz.

Originally Posted by Redback

.........

If for instance your in soft sand or mud, to get good traction you need a long footprint not a wide one, especially when you let your pressures down, a wide tyre will balloon more than a skinny tyre thus creating more resistance, would this be correct.

.........

Baz.

Unless someone has repealed the laws of physics, the area touching the ground will be given by the weight on the wheel divided by the tyre pressure - for any normal tyre, the sidewalls provide little support. This means that the narrower the tyre the longer the contact area and the wider the tyre the shorter the contact area, for the same pressure. This also implies that the narrow tyre will have more sidewall bulge than the wide one, since the belt has to distort more for the longer contact area (provided overall diameter is the same).

The only question is whether the long narrow contact area is better or worse compared to the short wide one, and the answer probably depends on the surface (do you want to ride in or on top of the ruts or the crossways irregularities?). In any case, the difference in realistic sizes of the same overall diameter is probably not as significant as other factors that changed at the same, such as tread type, rubber composition, effective track, and belt stiffness. One thing that is quite clear is that in almost every respect, even slight increases in overall diameter are an advantage, particularly offroad (ignoring effects on gearing and driveline and brake loading) due to a greater tendency to ride over holes and increased ground clearance. Similarly, it is clear that the smaller the tyre height (actual rim to tread distance - not %) the better the on road handling, the rougher the ride, and the greater probability of tyre and rim damage on rough roads or offroad.

There is no one tyre solution that is "best" - it all depends on how you use the car and what factors you rate more highly.

John
John

Originally Posted by JDNSW

Unless someone has repealed the laws of physics, the area touching the ground will be given by the weight on the wheel divided by the tyre pressure - for any normal tyre, the sidewalls provide little support. This means that the narrower the tyre the longer the contact area and the wider the tyre the shorter the contact area, for the same pressure. This also implies that the narrow tyre will have more sidewall bulge than the wide one, since the belt has to distort more for the longer contact area (provided overall diameter is the same).

The only question is whether the long narrow contact area is better or worse compared to the short wide one, and the answer probably depends on the surface (do you want to ride in or on top of the ruts or the crossways irregularities?). In any case, the difference in realistic sizes of the same overall diameter is probably not as significant as other factors that changed at the same, such as tread type, rubber composition, effective track, and belt stiffness. One thing that is quite clear is that in almost every respect, even slight increases in overall diameter are an advantage, particularly offroad (ignoring effects on gearing and driveline and brake loading) due to a greater tendency to ride over holes and increased ground clearance. Similarly, it is clear that the smaller the tyre height (actual rim to tread distance - not %) the better the on road handling, the rougher the ride, and the greater probability of tyre and rim damage on rough roads or offroad.

There is no one tyre solution that is "best" - it all depends on how you use the car and what factors you rate more highly.

John
John

Gosh, John, that is so rational You sure you don't want o just slip a little opinionated [fill here] in there

I guess it all comes down to personal choice and what you feel confident with.

Compound and tread pattern combined with how aggressive the pattern is are major factors, but like anything a compromise has to be sort at because of the varied surfaces we drive on, not counting onroad, just offroad, with onroad you adjust your driving style depending how aggressive the tyre is

Baz.

Scuse me JDNSW, but why would a skinny tyre have a longer footprint and a fat tyre have a necessarily shorter footprint when the have the same outside diameter?

If you have a tyre with a 32 inch diameter, length ways they will have the same footprint, cross ways a fat will have more surface area covered, or is there some piece of tyre science I am missing here?

Now one big issue with FATS is unsprung weight, which i am sure is something the rally cars mentioned earlier would be taking seriously!

And when it comes to "Cutting down through the loose surface material", that's a little random isn't it? I would think that a big, fat mud pattern tyre that grabs a huge handful of the surface, gets grip and stays above the sludge, dust, loose gravel is better than a half submerged skinny tyre! Or is there some piece of tyre technology I am missing here too?