JD Tractors porpoising down the highway

[Brute 23]

We briefly touched on reasons the JD tractors hopped so bad going down the highway. I've been playing around with the 6120E we got a few months back and have made a little headway.

We changed out the tires very soon after getting the tractor. I had a front tire blow out on me going down the road so we took that as a sign. The new tires did not stop the "hop" but they were a great improvement in handling over the original tires that came on the tractor.

I tried running with out the bucket and that did not change any thing. I have also tried adding weight and neither have made any changes.

Lastly, I lowered the air pressure. The tires now call for 23 on the front and 39 on the rear. They were at 25 front and 30 rear and it still hopped. When I went to 20 all the way around I noticed quite a bit of difference in the ride, for the better. I went from running 18mph down the highway the 21mph with no issue.

Next time I will try 15 psi on the rear and leave the fronts at 20 psi. 24mph is the max speed.

Hope that helps any one else with the issue. It seems to be really common.

 

[SBMF 2015]

Hmm, the only one we have trouble with is our old jd 8430 4x4 articulate. It will get flat spots from sitting and it can be like riding a frog down the road.

 

[Stocker Steve]

Seems like the E series FEL packages have a lot of lift, but not the wt. or the length or the front tires to handle well.

What kind of tires did you go to?

 

[Brute 23]

When reading online there were complaints across all the series, not just E.

Firestone

 

[Rmc]

13 -18 psi rear . If that doesn't do enough then put fluid in rear tires

 

[cfpinz]

When reading online there were complaints across all the series, not just E.

Firestone

Radials or Bias?

My NH 8260 has radials with fluid in the back and dances a pretty good jig going down the highway. Always figured it was a bent wheel or something just a bit off center, but never had the chance to follow it down the road and watch.

 

[Brute 23]

Radials or Bias?

My NH 8260 has radials with fluid in the back and dances a pretty good jig going down the highway. Always figured it was a bent wheel or something just a bit off center, but never had the chance to follow it down the road and watch.

Radials

 

[cfpinz]

Interesting. I've never had one of the tractors with bias tires do it, 4wd or not.

 

[sim.-ang.king]

I know the side of the tire will say 32ish max psi, and most tire shops will do 25-28, but radials are really meant to be at 15-20. Unless you do nothing but road driving.

 

[Nesikep]

tire pressure still sounds way too high, though that depends on if it's a row crop style tire or a balloony tire. What the tire says on the sidewall is only max pressure, check the tractor manual, I don't have anything here running much over 10 PSI
Filled tires are less hop prone than air-only tires, the water isn't compressible which stiffens the tire at low pressures.

If your tractor's tires look anything like the ones in this pic and don't squat at all it's not surprising it's not behaving well
I read you should have about 3 full lugs in contact with level hard ground, tractor shown hardly has 2 lugs in contact, I'd maybe run a little higher pressure in the front if you have a FEL

 

[chevytaHOE5674]

Fronts on a loader tractor need near max air pressure if lifting heavy stuff. Load capacity is at the specified PSI. Rears i usually start at 15 and go down from there. When the loaders come off for hay making them front tire pressure drops considerably.

 

[Atimm693]

It's not just a JD thing. We have a Case Maxxum 110 that does it terribly.

I haven't found any solution other than slowing down until it straightens out. That Case has a loader and needs at least 30lbs in the front tires. I had wondered if liquid ballast in the front tires may help.

I think it's a matter of wheelbase. Seems like the industry has gone to making tractors as short as possible for better visibility and turning circle. That Case is very stubby, there's only 18 inches or so between the front and rear tires.

39psi in a rear tire sounds like way too much. I think it's more common to run half that.

 

[Ky hills]

I agree with @Atimm693 I thibk it has to do with the short wheelbases, and with a loader on front it just makes that front end heavy.
We have a JD 5055e and the wheelbase is considerably shorter than the older tractors I've had.
I keep maximum pressure in the front tires because of the loader, the back tires have fluid in them for a bit of a ballast.

 

[callmefence]

Both my e series tractor's do it. 5100 and 5085. The 85 is open station and is really bad about it. The wieght of the cab on the 5100 I think makes it not near as bad. But hey you don't drive a tractor down the road, you herd it ...lol

 

[SmokinM]

I believe that all that plays a roll but I also have only ever noticed on MFWD tractors. Makes me think that it may have a lot to do with a very minor difference in the gear ratios, that even changes as tires wear. Wouldn't have to be off much and even when a tractor is in 2wd those front gears are turning and producing resistance. JMO.

 

[Porkies Bovines]

Mercedes-Benz is having a porpoising problem on their W13 car, wonder if its for the same reasons??
Seriously I sometimes have that problem with my older TS90 4WD, not all the time, but If I reduce the speed till it quits, then go back to full throttle that helps, sometimes. The oem tires were worse (6 ply), that the 8 plys on it now.

 

[Lucky]

I thought the new tractors rode rough because they were so short and had 4 cylinders instead of 6.