john deere

music110

I have a john deere 4 wheel drive tractor with 24rims on front . Does it make a difference to the tractor if I put 28 rims on instead. Any advice have heard you cant just looking for advice. Thanks.

Zr105

music110 wrote: »

I have a john deere 4 wheel drive tractor with 24rims on front . Does it make a difference to the tractor if I put 28 rims on instead. Any advice have heard you cant just looking for advice. Thanks.

You cant do it unless you change the rears to match ratio wise. It'll bugger up the gearing in the front axle. Even changing the tire size(say putting a 420 tire on instead of a 380 tire) will bugger it up.

Nekarsulm

there was a very good chart posted up in the tractor & 4x4 forum, showing radius of tyre sizes. If I find it I will post a link. Some combinations of larger rim and modern low profile tyre can work.

music110

many thanks for your help and advice lads.

coolshannagh28

The radius must remain the same ,this is indicated by the second number on the tyre ie 520 85r 38 in order not to damage the gearing.

Zr105

coolshannagh28 wrote: »

The radius must remain the same ,this is indicated by the second number on the tyre ie 520 85r 38 in order not to damage the gearing.

Not true I'm afraid, the second number, in your example 85 is a percentage of the width of the tire, ie in this case the side wall would be 85%of the tread width of 520.

Nekarsulm

Zr105 wrote: »

Not true I'm afraid, the second number, in your example 85 is a percentage of the width of the tire, ie in this case the side wall would be 85%of the tread width of 520.

Correct, Zr.
Still cannot find that tyre size chart, but I remember for example, a Fiat on 16.9 by 34 tyres could have the back fitted with 650mm tyres (30 inches wide) on a 30 inch rim. and the radius of the much wider tyre was only about 8mm larger than the 34 inch originals.

Zr105

Nekarsulm wrote: »

Correct, Zr.
Still cannot find that tyre size chart, but I remember for example, a Fiat on 16.9 by 34 tyres could have the back fitted with 650mm tyres (30 inches wide) on a 30 inch rim. and the radius of the much wider tyre was only about 8mm larger than the 34 inch originals.

I know the chart you mean alright, both Michelin and good year used to have a very good chart that broke it down by rolling circumfrence, you could just scroll down till you found your current tire size then you could look at the ones close to it to see what would suit etc....

I know 18.4r34 are the same height as 16.9r38, and 600/65r34(although they'd be a rare tire) also fairly close on 28.1r26 that would be used on combines etc!

Nekarsulm

Hi Music110, and Zr105, here a few links. None are the exact one I was looking for, however.
http://www.firestoneag.com/webres/File/Tire-Info/TireInfo-RCI.pdf

This Firestone chart shows that you can swop a 520/65/24 with a 420/85/26 or a 380/85/28

Here is a BKT chart, which is very good, but takes a bit of work to collate all the info you need, regarding the circumference of each tyre, and the ratio between front and back which you would have to correlate onto a larger size set.
http://www.bkt-tires.com/bkt_tyre_replacement.html

onyerbikepat

What if your tyres are worn well on the front but newish on the back? Wouldn't this throw out the gear ratio too?

Zr105

onyerbikepat wrote: »

What if your tyres are worn well on the front but newish on the back? Wouldn't this throw out the gear ratio too?

It does but generally not to the extent of swapping around tire sizes, you can get away with a small difference in sizes.

4wd tractors are generally designed with a small amount of "lead" in the front tires, basically they turn a little faster than the rear tires, this helps to "pull" the front of the tractor around, to much lead will lead to excessive wear on the front if on hard ground(this includes braking as the majority of tractors break through the 4wd system)
The other side of that is that if the front tires are a little small it will lead to the front tires scuffing as the rears will be pushing them on faster than they are turning

Zr105

Nekarsulm wrote: »

Hi Music110, and Zr105, here a few links. None are the exact one I was looking for, however.
http://www.firestoneag.com/webres/File/Tire-Info/TireInfo-RCI.pdf

This Firestone chart shows that you can swop a 520/65/24 with a 420/85/26 or a 380/85/28

Here is a BKT chart, which is very good, but takes a bit of work to collate all the info you need, regarding the circumference of each tyre, and the ratio between front and back which you would have to correlate onto a larger size set.
http://www.bkt-tires.com/bkt_tyre_replacement.html

Those tire sizes didnt sound right to me, but i guess they are going by the chart...

onyerbikepat

Zr105 wrote: »

It does but generally not to the extent of swapping around tire sizes, you can get away with a small difference in sizes.

4wd tractors are generally designed with a small amount of "lead" in the front tires, basically they turn a little faster than the rear tires, this helps to "pull" the front of the tractor around, to much lead will lead to excessive wear on the front if on hard ground(this includes braking as the majority of tractors break through the 4wd system)
The other side of that is that if the front tires are a little small it will lead to the front tires scuffing as the rears will be pushing them on faster than they are turning

I have a Landcruiser and there's permanent 4WD. There's a central differential on the drive shaft right under the center of the vehicle. Would the newer 4WD tractors have this, I wonder?

Zr105

onyerbikepat wrote: »

I have a Landcruiser and there's permanent 4WD. There's a central differential on the drive shaft right under the center of the vehicle. Would the newer 4WD tractors have this, I wonder?

No the 4wd on tractors is more an on/off job, permanent 4wd through a diff wouldn't work. The land cruiser might be set differently but landys have always been permanent 4wd with a locking diff in the centre, this meant the power could be thrown to any corner, the problem with this(and I've got caught with it before) is that when trying to pull off with a heavy load up hill on gravel/any slippy surface, in a landy(was a disco with me) all the power can get thrown to the front axle and it'll just spin,