Tyre Size

slurryboy

Well-Known Member
Rather than starting a new thread,, tractor currently on 18.4 38 and 14.9 28 what fronts would be needed if changing the rears to a 520/70/38? @gone
 

gone

Well-Known Member
Rather than starting a new thread,, tractor currently on 18.4 38 and 14.9 28 what fronts would be needed if changing the rears to a 520/70/38? @gone
420/70/28's will not change the gearing and should fit most rims.
You could stick with 14.9 R28's if your rims are very narrow.
 

TimN

Active Member
Hi.
Have a John Deere 6920s running on 520/85/38 rear and 480/70/28 fronts. Just about to order a new set but worried that fronts don’t match the back for rolling radius as when on the road and brake it seems to snatch out of 4wd. Only had the tractor 8 months and just assumed it was right as it came off a dealer. Any help would be appreciated.
Thanks Tim
 

gone

Well-Known Member
Hi.
Have a John Deere 6920s running on 520/85/38 rear and 480/70/28 fronts. Just about to order a new set but worried that fronts don’t match the back for rolling radius as when on the road and brake it seems to snatch out of 4wd. Only had the tractor 8 months and just assumed it was right as it came off a dealer. Any help would be appreciated.
Thanks Tim
480/70/28's are the same height as 420/85/28's.
That would be a fairly standard on a a JD 6920, but JD had a lot of tyre options. If you are worried about the tyre combo on your tractor you may find out the inter axle ratio, some of the JD experts might be able to tell you how or a good JD garage.
 

TimN

Active Member
480/70/28's are the same height as 420/85/28's.
That would be a fairly standard on a a JD 6920, but JD had a lot of tyre options. If you are worried about the tyre combo on your tractor you may find out the inter axle ratio, some of the JD experts might be able to tell you how or a good JD garage.
Ok. Thank you very much
 

eire23

Well-Known Member
Just a quick question on tyres sizes... Currently looking at a tractor, rears are 16.9 34's. What tyre for the front would be the best match to them? Thanks:Thumbp2:
 

MF30

Well-Known Member
Just a quick question on tyres sizes... Currently looking at a tractor, rears are 16.9 34's. What tyre for the front would be the best match to them? Thanks:Thumbp2:
13.6 x 24 would be a typical match, but an awful lot depends on tractor type and ratios.
 

eire23

Well-Known Member
13.6 x 24 would be a typical match, but an awful lot depends on tractor type and ratios.

Its a 4355 12/12 if that makes any difference. 13.6 x 24 would be 340/85/24. I'd be safe going to a 380/85/24?
 

MF30

Well-Known Member
I couldn't be really sure, a tyre dealership or MF dealer might be the best place. What I suggested is what's fitted to mine but it's not a MF
 

gone

Well-Known Member
20190911_123755.jpg 20190911_123730.jpg 20190911_123803.jpg Standing behind your MF there are a couple of plates on the right hand side of the cab under the back window, as per the pictures.
In the small silver square in the bottom left corner of the bigger one is a number, the gearbox ratio, it is 1,23 on mine, check that number on yours and get back to me.
 

Ptk44

Well-Known Member
View attachment 69773 View attachment 69774 View attachment 69775 Standing behind your MF there are a couple of plates on the right hand side of the cab under the back window, as per the pictures.
In the small silver square in the bottom left corner of the bigger one is a number, the gearbox ratio, it is 1,23 on mine, check that number on yours and get back to me.
I always wondered how to check ratios... never knew they were on a plate on MFs.
 

gone

Well-Known Member
I always wondered how to check ratios... never knew they were on a plate on MFs.
I use to remember how to calculate it for JDs, you have to work it out from 3 different figures, JD offers a massive range of tyre options.
Most other manufacturers have the info in their operators manual.
 

Damo810

Member
Hi lads, have a valtra 6550HT currently on 420/70/28 at 25%and 18.4/38 which are wore off her. I have the option of putting either 520/70/38 (35%left) or a 600/65/38 (50%)on her as it was part of the deal. Tractor is doing a good bit of loader and road work but we are also on some wet ground(All grassland). Which would be the better option?

I’m aware I’ll have to change the outer band on the rim at the rear and have got a price for it, would I have to change the front bands if I went to a 480/65/28 down the line? I might try and source a set of rims altogether and keeps current 18.4s on the rims as spares and or duels,would I need different type of rims for duels?
 

gone

Well-Known Member
Hi lads, have a valtra 6550HT currently on 420/70/28 at 25%and 18.4/38 which are wore off her. I have the option of putting either 520/70/38 (35%left) or a 600/65/38 (50%)on her as it was part of the deal. Tractor is doing a good bit of loader and road work but we are also on some wet ground(All grassland). Which would be the better option?

I’m aware I’ll have to change the outer band on the rim at the rear and have got a price for it, would I have to change the front bands if I went to a 480/65/28 down the line? I might try and source a set of rims altogether and keeps current 18.4s on the rims as spares and or duels,would I need different type of rims for duels?
The 6550 has a 50/50 weight distribution, in my opinion, great for traction but less good when you have a loader on.
What brand are the tyres?
 

Damo810

Member
The 6550 has a 50/50 weight distribution, in my opinion, great for traction but less good when you have a loader on.
What brand are the tyres?
Yes, she’s actually too light in the backend for the loader tbh. The 600’s are vredesteins im unsure as to the make of the 520’s, they are coming off a relatively new JD however.
 

gone

Well-Known Member
Yes, she’s actually too light in the backend for the loader tbh. The 600’s are vredesteins im unsure as to the make of the 520’s, they are coming off a relatively new JD however.
In general I would prefer 520's to 600's for grass and road work, and they should fit the same rim as your 18.4's.
 

gone

Well-Known Member
Why if you don’t mind me asking?
I find the 520's a better match for the weight of tractor, offering a very good balance between flotation and traction.
I find a tractor of the weight and power of a 6550 doesn't have the weight or power translate it's power into traction on grass while on 600's.
 

Ptk44

Well-Known Member
Is there
View attachment 69773 View attachment 69774 View attachment 69775 Standing behind your MF there are a couple of plates on the right hand side of the cab under the back window, as per the pictures.
In the small silver square in the bottom left corner of the bigger one is a number, the gearbox ratio, it is 1,23 on mine, check that number on yours and get back to me.
Is there a similar plate for new holland or how would a fella go about finding the inter axle ratio? Thanks.
 

gone

Well-Known Member
Is there

Is there a similar plate for new holland or how would a fella go about finding the inter axle ratio? Thanks.
I'm sure the info is either stamped on the tractor and or in the user manual, but sorry I don't know where CNH tractors has the info.
 
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Damo810

Member
I find the 520's a better match for the weight of tractor, offering a very good balance between flotation and traction.
I find a tractor of the weight and power of a 6550 doesn't have the weight or power translate it's power into traction on grass while on 600's.
Would the soft ground in mayo make much odds Gone? We don’t have many hills and I probably will add wheel weights. I’d normally just go with the 520’s but I have about 6 acres of big reclaimed and another six to go which will be used for early cut silage so floatation is key there, not drawing any big weights atm other than the cattle trailer and that’s only on the road and possibly a low loader of bales. Would there be much of a difference at all really between a 600 and a 520 on the boggier ground or any disadvantage while drawing loads on the road in terms of ride or stability. Thanks for the input gone, my tyre knowledge is weak to say the least.
 

gone

Well-Known Member
Would the soft ground in mayo make much odds Gone? We don’t have many hills and I probably will add wheel weights. I’d normally just go with the 520’s but I have about 6 acres of big reclaimed and another six to go which will be used for early cut silage so floatation is key there, not drawing any big weights atm other than the cattle trailer and that’s only on the road and possibly a low loader of bales. Would there be much of a difference at all really between a 600 and a 520 on the boggier ground or any disadvantage while drawing loads on the road in terms of ride or stability. Thanks for the input gone, my tyre knowledge is weak to say the least.
In very soft wet ground with the loader off and a large weight on the back the 600's would have an advantage, but in my opinion not enough to justify the new/altered rims needed. Most of the time it is the front wheels that will let down a 6550 with a loader.
The fact that the 600's have more thread might be a factor.
 
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