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air pressure for smoother ride

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mower
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2002-03-14          36335

I just purchased a new JD 4100. I made the move up from a JD 455 lawn & garden tractor. One thing I quickly noticed was the rougher ride of the 4100. Will reducing air pressure help smooth the ride some? The tractor has the industial tread tires.

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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2002-03-15          36356

Industrials do have advantages over other types, but they also are known for their rougher rides.

Lower air pressures give smoother rides. However, it's best to run air pressures specified in a load chart for the particular tires. Many tractor tires take surprisingly low pressures--especially to people used to beefy truck tires. However, the pressures should be appropriate for loads actually on the axles, and load charts should be available for the tires. Grossly wrong pressures become safety issues. Wrong pressures also can change the front/rear axle drive ratio and cause extra wear and tear on the front drive train. However, it is easy to overstate these issues. They may be real, but that doesn’t turn tire pressures into rocket science, and I imagine that few people adjust pressures every time they change an implement.
....

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Mrwurm
Join Date: Feb 2002
Posts: 184 South East Michigan
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2002-03-15          36360

When I use to drive pick-up trucks you could get two different kinds of tires. 'P' rated tires such as P23575R15. These were passenger rated tires with a lower load range than 'LT' tires. The other tires (as mentioned) were the 'LT' tires such as LT26575R16. I was told that these tires had a thicker side wall and as such had a higher load rating. I am thinking that maybe it's the same for R4 industrial tires. Maybe they have a thicker sidewall than the turf tires that you are used to and a stiffer ride is unavoidable.
Jerry ....

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BillMullens
Join Date: Jun 2000
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2002-03-15          36362

Lower pressures will smooth the ride noticeably. I had my tractor for several months before I bothered to check the pressure, they were much too high. Lower pressure helped the ride and helped traction, too.
Bill ....

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DRankin
Join Date: Jan 2000
Posts: 5116 Northern Nevada
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2002-03-15          36363

If you have a stiff sidewall then let it do it job. The "right" tire pressure for a tractor is evident when there is a generous bulge in the sidewall just above the ground. If that means you carry ten pounds of pressure in the tires then that is right as far as I am concerned. I think I am currently running about 12 or 14 pounds in the rear tires on my 4100. The ride is softer and the traction is markedly improved over the same tire with 30 pounds of pressure. A couple things to remember: Under inflating a tire on a car is dangerous because of the weight of the vehicle coupled with high speed operation will cause the tire to overflex, overheat and fail. That is what happened to the Ford-Firestone combination. Our 4100’s, even when carrying the biggest implements, are nowhere near the weight of even a small pick-up and with a top speed of 11 miles per hour we will never have to worry about tire failure. By the way, I keep my front tires inflated so the good bulge is present when the loader is full of dirt. Hope this helps. Mark ....

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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2002-03-16          36389

I sort of compromise on front tire pressures. The load chart for my turfs gives 12 lbs. as the greatest load rating. I run 16-lbs. summer and 10-lbs. winter for extra traction. Sixteen pounds is nowhere near the max pressure rating for the tire, but I just let the side-walls bulge under buckets of gravel. My reasoning is that I'm not going very far with that weight. I go much further with light loads, and I'd rather run pressures that keep the axle drive ratios within spec.

High pressures increase a tire's rolling circumference, which increases the front axle lead. Axle lags and excessive leads contribute to front drive wear and tear when in 4wd. Anyway, anybody who runs high front tire pressures for their loaders and also have difficulty disengaging their 4wd might try reducing the front pressures a bit. In addition, most specs call for mild front axle lead, and for that reason it's good to stay in 2wd when on paved surfaces, but especially if high front pressures are used.
....

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DRankin
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2002-03-16          36396

Excellent advise. It is something I do without even thinking and didn't think to pass along. Thanks Tom. ....

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jyoutz
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2002-03-16          36412

Mark do you have industrial tires on your 4100? What is the pressure you run in your front tires? ....

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DRankin
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2002-03-16          36413

Well, here is the story. I shot my wad buying the tractor and never thought to question the usability of R1 ags for my needs. I wish I had known about this board a year ago. I certainly could not afford to buy a set of replacement tires from JD when I found I was operating a 4wd rotor tiller. So I carefully measured and did some scientifical (hey that's a real word) calculations to establish the circumference ratio between front and rear tires and went down to the tire store. I found a good size match with a Mud and Snow 245/75-R16 on the rear and a 145R12 all season tires on the front. I get all the traction I need on the steep sand dune I live on and spent about a thousand bucks less than replacing tire and wheels through Deere. The fronts are made for tiny cars like a Subaru justy and I keep them at around 30 pounds these days and run about 10 or 12 in the rears. I have modified the backside on my FEL to act as 5th wheel hitch so I can park my travel trailer where my pick-up fears to tread and the tongue weight is about 700 lbs. If not for that I might run them a little lower. More info than you wanted I am sure, but since I am not running traditional tractor tires the answer is not so simple. ....

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DRankin
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2002-03-16          36414

MrWurm: I don't think you can be a full fledged member of the tractor board if you don't drive a pick-up any more. We are gonna pretend you never said that. Now don't say it again. Mark ....

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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2002-03-17          36418

Gee, I've got a 1/2-ton and still running the Firestone tires in question. Of course, I do pay attention to load ratings and pressures, and I don't think I'd put 1200 lbs. of implements in the bed and drive the highway on hot days. Maybe the 1/2-ton qualifies me for membership but the tires disqualify me.

Another membership question might be whether anybody who has a tractor capable of power-hops is qualified. That's another tire pressure question, but I don't remember the answer because I don't think my 1710 is capable of hopping much.

OK, everybody and especially me can take their tongues out of their cheeks now. As is obvious, it's a pretty good group of participants here and the more the better.
....

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Bob H.
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2002-03-17          36446

I set the tire pressure on my 4700 with FEL and box scraper as follows. First I fill the front loader with dirt then drive the tractor on a hard smooth surface (like a cement driveway, garage floor, etc.). Raise the rear gannon or any other implement on the 3 point hitch off the ground as well as the loader bucket. The only thing touching the flat surface should be the four tires. Make sure there is a lug on the tire of the wheel you are checking at the downward most postion. Now slowly let air out of the tire until the outside edge of the lug is just touching the flat surface (easily checked by seeing if a piece of paper will slip between the ground and the outside of the lug). Do this on all four tires. You will be surprised how little air it takes to reach this setting. Of course the most air will be in the front tires because of the weight in the bucket. This is the method we used to set up the tire pressure on off road race trucks and I find it works pretty well with the tractor as well. ....

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TomG
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2002-03-18          36459

Bob: I've head of people looking at their tread prints for the same reason. Your method sounds more precise though and there may be some complications worth thinking about.

For example, I'm not sure if the technique works for both radial and bias ply or loaded and unloaded tires. I'd also verify the results with a load chart the first time I used the technique. I suppose it's possible that with some tires the full width of lugs aren't intended to meet the ground with static loads. Trying to get the full width on the ground may result in under inflation for a given load. I think that under inflation causes the centre of a tire to distort and become concave, which reduces rather than increases traction. However, I do think that the tread print idea is useful, and that there also are some interesting issues here.
....

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Bob H.
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2002-03-18          36470

Tom, I have found that the problem of under-inflation and a concave in the center of the tire can be avoided by making sure the outside of the tread just begins to touch the ground. If you go just by your tire print, you will find that it looks relatively the same for a variety of tire pressures, including under-inflation. It takes pretty severe under-inflation before you will notice it in the tread pattern left by the tire.
The theory behind this method is that when the tread just begins to touch on the outside edge, the tire is slightly overinflated and the amount of weight on the center of the tread is greater than on the outside edge. When you are in motion, the uneveness of the terrain causes the weight to vary up and down and the weight on the outside goes from less than static to more than static. This causes the tread to flex when in contact with the ground offering more bite. It also helps to keep the tread clean when in other than dry conditions. With a tractor there is no suspension so everything is absorbed by the tires and this causes a lot of flex, however, the speeds are slow so this helps to minimize the impact.
....

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mower
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2002-03-18          36473

I use my 4100 for mowing exclusively. Will this same principle of deflation apply?----That being lettting air pressure out until the outside of the tread just touches. I use a 3pt 60" mower deck. Only occasionally will I use a 5' rear blade. ....

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TomG
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Posts: 5406 Upper Ottawa Valley
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2002-03-19          36486

Yes I think these approaches should be good for a mowing 4100. I believe the main idea is that tire pressure supports weight but also affects traction and axle drive rations. There is an ideal pressure for a given load and ground conditions and it is possible to overload or under-inflate tires. Bob's approach seems to be a pretty good way to find decent pressures to run.

Myself, I'm more load chart oriented. I figure the weight distribution on my tractor is around 60/40. I know about how much additional load I'm carrying front and back. So, the total weight on an axle divided by two is a tire's load, and a load chart indicates the right pressure. That way if I'm technically overloaded, which actually is fairly common, then at least I know about it.

Of course, precision isn't needed here. A person may actually measure things a few times to get the sense of what's best for different conditions, but later adjusting pressures just comes automatically.
....

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Bob H.
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2002-03-19          36501

Mower, although I haven't used my tractor for lawn mowing I would think that you would want the tires slightly overinflated to prevent any tread squirm to minimize any damage to the lawn. The very thing the method I use is supposed to achieve, I think you want to minimize. I think you would want them overinflated but not to the point of losing traction. ....

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TomG
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Posts: 5406 Upper Ottawa Valley
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2002-03-20          36522

I don't use my tractor for mowing, but I do know that I don't have to turn too sharply before the front turf tires on my 1710 start tearing turf--even in 2wd. I don't know if increasing tire pressures would help, but I might try it if I have to maneuver on lawns a bit. However, if I was operating on fairly steep slopes, I'd probably got for traction and let the lawn worry about itself.

....

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