Checking tyre sizes and diff ratios

Fhanks fellas, I'll cunsida meself ejamacated.

Zuffen

If you look at Swishy's diagram you will see the tread goes at the full radius speed while it is round and a solid/hard pumped tyre with no give moves at that speed across the ground.

When a soft tyre flattens out it becomes like a Caterpillar track closer to the axle . Instead of just a radial point on the solid tyre being attached to the axle moving as one' the bottom of the tread now "cuts the corner". As you say the tread does not change length so the only way it can work is if the bottom bit goes slower over the shorter distance and speeds up to get the long way over the top. If it goes slower without slipping on the wheel it must cover more distance at the slow spot.

The flexibility of the tyre allows it to constantly change shape from round to square and places the contact point way out ahead and behind the normal round radius track. What happens when the tread is in the air means nothing, the only thing that matters is the point between the axle and the ground and as that "radius" gets less with a deflating tyre the ground contact gets longer and longer to keep the bottom tread going slower past the axle to match the big radius speed over the top.

Lang

Main aim of the game

Gear Fast
n
Run slow

Provide n U got the cubes to make everything turn

WotSezU?

cya

Paul FH wrote,
"Rolling radius is theoretically correct, but with modern steel belted tyres the full
circumference of the tread belt will be sent around each revolution."

Just to make sure I have the full guts of that, I am assuming (and I do a lot of it!) you mean with the old NON RADIAL or "rag" tyres (nylon), that you would always "lose" a bit of distance travelled with each revolution of the wheel, whereas with as you say, modern steel belted (radials) travel their true AND full distance.
Not disputing, making sure I understand.
Cheers, Dave.
BTW, checked out the diff ratio as per Mrsmackpaul's instructions, came up with an unknown (for me anyway) ratio of 5.42:1,
Nothing in my books with that ratio, but that means zilch! Probably someone like Dana, Rockwell, Eaton, Meritor even the old Spicer use it (CW to Pinion count of 65/12)???. Don't even know just who makes these diffs, reckoning on ENV. Being Pommy.

Tanks Lang, and I guess with all that flexing and changing speed, is why tyres get so hot when under inflated. All this gained knowledge and on a public holiday too.

Yes all tyres will deflect when loaded so this does alter the rolling circumferrance. As discovered earlier a tyre fitted and inflated onto a wheel gave a longer length between chalk marks than one fitted onto a vehicle empty then again loaded, Each time the chalk marks will get closer.
The chalk mark idea is how a cocky can adjust his tyre pressure to the job he is doing by using a stick in the ground at each point the chalk line hits ground. This is to establish the correct amount of slippage he needs to do the job efficiently. Too much and your burning fuel for nothing too little and it not working as designed.
Yes under inflation causes heat which in turn reduces tyre life. This goes for everything that runs on pneumatic tyres. Run the maximum recomended pressures in your car and truck tyres and you will benefit with longer tyre life and better fuel efficiency.

And to add a bit more Cobbadog to the farmer and his tyres

To much pressure causes compaction
To little pressure damages the walls and tubes and causes scuffing internally and cracked walls
Ballast in tyres or by fitting extra weights is generally how a farmer changes slippage
Also attachment to the drawbar and drawbar height
Draft control on the 3pl
The way and angle the the top tink is set have a big effect as well

When it comes to 4x4 tractors, as in smaller front wheels to back wheels the inter axle ratio needs to be adjusted so the front wheels are driving 5-10% faster than the rears, you can feel this when its not right

When you run duels you only ballast the inside tyres

On a equal sized 4wd tractor that becomes a whole different ball game

I guess just like trucks tractors have grown a lot in size and power and there is very few good operator's left today as weight and bucket loads of power have taken the need for skill away from tractor driving

You dont even have to steer the buggers anymore


Paul

Yeah, but wait till I hit 'em with a revised ratio chart!

Forget HP it all about Torque

geoffb wrote: Forget HP it all about Torque

Spot on Mate...