AG Tires on 4X4

[catbird7]

I have a 1996 B7100HST 4X4 with turf tires. I bought a set of AG wheels and tires size:
Front: 6.00-12
Rear: 8.00-16
This is exactly the size listed on "Tractor Data" website.
When I got the new tires / wheels home, the rear tires look identical in height to the existing rear turf tires but the new front AG tires are much taller, probably 2" or 3" taller. Will this work?

 

[gktilton]

what is the overall height of your new rear and front tires. I'll measure the ones on my B7100 when I get home to compare. I have AG's on all 4 and have no issues so I am assuming they are correct.

I will say that when 4x4 is engaged the fronts do pull a little, but I think that is by design.

 

[rjwa749]

You should be good to go. Your tire sizes look correct.

I have AG with the 4X4 and no issues.

 

[catbird7]

I raised the tractor off the floor (all four tires) and replaced the turf tires on one side with the new AG tires. Then I used a piece of small diameter string and wrapped it around the circumference to measure it. The following are the dimensions I got:

Turf Front: 63.75"
Turf Rear: 92.75"

AG Front: 70.5"
AG Rear: 97"

Seems like a lot of difference! Will this work?

 

[Kytim]

There shouldn't be a problem. only the relationship between the front and rear are an issue, not between turf/ag. those seem to be proportional to one another.

kytim

 

[300zx]

Catbird, what I have read is that you have to keep the ratio of the back to front the same because of the gearing. Your turf ratio is 1.46 and the ag ratio is 1.36. If it doesn't seem like you are pushing or over pulling with the front tires when you are in 4x4, I would think you are OK. It would be interesting to know what the actual gear ratio back to front is. For curiosity, you could jack one side up and rotate the back wheel (while in FWD, first gear and with the clutch in) 2 or 3 rotations and see how many rotation you get on the front. The ratio of the rotations would tell you the ratio of the gearing, thus the ratio of the circumferences you need. Sorry, I am an engineer and usually am interested in the technical side!

 

[eserv]

The gear ratio is 1.4664 on The B7100 The tire ratio should be very close to the same with preference to a little front lead.

 

[catbird7]

KYTIM: I listed a comparison between AG & Turf because I know the Turf ratio works as that's what the tractor came from the factory with. So the comparison is actually between what I know works and the AG tire dimensions that produce a ratio that I'm un-aware of how or if it works! The goal is to gain a better understanding of tire ratio tolerance of a B7100 HST!

ESERV: The gear ratio you listed (1.4664) is very close to what I measured (1.4549) on my factory suppied turf tires.

The question becomes what happens to a tractor with a gear ratio of 1.4664 when you install a set of tires with a ratio of 1.3758? OR what is the acceptable ratio tolerance?

 

[catbird7]

I tried to attach a copy of an email from Kubota regard proper AG tire size for a B7100 HST. Apparently the attachment didn't work. Here is what they said.
6-12 AG Front
8-16 AG Rear

 

[rjwa749]

I tried to attach a copy of an email from Kubota regard proper AG tire size for a B7100 HST. Apparently the attachment didn't work. Here is what they said.
6-12 AG Front
8-16 AG Rear

Your attachment worked.

It confirms you have the correct set up.

 

[tiredguy]

Hold your horses before you do some very expensive damage!!!

Just because the "book" says it has a certain size tire between tur,ag, or industrial does not mean they don't use a different gear ratio front to rear.

What you need to know is what your current "ratio" is by finding the " rolling circumference " of tires now, then get the specs for the turfs to do the same thing. Do an internet search for the manufacturer and look them up if possible.

Here's the formula for determining what the ratio is: divide the rolling circumference of the front tire by the rolling circumference of the back tire.The
result is the actual "ratio". If the two different tires are within 2% you're ok and won't cause damage. Otherwise you'll be pushing or lagging and can "wind it up enough" to break the transfer case of front gears. Both of which are very expensive repairs!!!
I'm to worn out to do it tonight, but if you shoot me an email telling me which sizes of both types of tires along with the brand I'll figure it out and reply tomorrow. cwtireal@gmail.com
Al

 

[asbug]

My grey market B7001 has the Agressive AG tires on it and I love them!!
I work alot in the soft, leafy woods so it is great about not getting stuck!
Good luck,
KC

 

[tiger9297]

This first picture is not my tractor, but is a B7100 with Ags all the way around. The second picture (the one with the loader) is my B7100. I'd love to put Ags on it, but I can't find any Ags or Industrials that will fit the front rims. I guess I could change rims, but first I would have to find the rims and then make sure they are the right size to accommodate gearing. I have found that the dealers are very little help with answering questions about this. If anyone finds a solution or source where rims and Ags can be found, please post a link. Thanks.

 

[hodge]

All good questions. I don't have many answers for you, but I will say that your frustration is shared by other 7100 owners, and the answers are much more elusive than one would expect.
In searching for ags for mine, the local dealer could'nt give me a straight answer, either. The only answer was to buy new rims and tires, to the tune of about $1200. I have kept my eyes open for used sets for sale, but haven't seen anything yet. My current solution was to buy a set of more agressive turf tires, which was not an easy task, either. I put a set of 21x8x10 agressive turfs on, and aired them down (they look fine, but I don't have a loader) until they didn't bind in 4WD. Carrying about 9 or 10 pounds of pressure keeps them about right. I would love to have a set of ags, but haven't been able to skin that cat, yet. Keep us posted on what you find out in the future.
Mark

 

[Gingerheadman]

Hello,
New to the forum and just got my first Kubota B7100-HST 4wd.
The talk of tires has me in a bit of confusion, my rear tires are 29-12.5x15. My question is, I have found used ag tires of the same size (29-12.5x15) if I put the wider ag tire on the tractor although the height and width are the same should I have any issues out of the 4wd issue?
I'm lucky enough to have a used otr warehouse in our town and they all all sizes of used turf and ag tires for almost any tractor, most are in terrific shape.

I was hoping to find out so I can get them on before the main winter storms hit our area.
Thanks.

 

[85Hokie]

Hello,
New to the forum and just got my first Kubota B7100-HST 4wd.
The talk of tires has me in a bit of confusion, my rear tires are 29-12.5x15. My question is, I have found used ag tires of the same size (29-12.5x15) if I put the wider ag tire on the tractor although the height and width are the same should I have any issues out of the 4wd issue?
I'm lucky enough to have a used otr warehouse in our town and they all all sizes of used turf and ag tires for almost any tractor, most are in terrific shape.

I was hoping to find out so I can get them on before the main winter storms hit our area.
Thanks.

Not sure what you mean about a wider tire.....the turfs are typically wider and a R1 is typically a little narrower - however, whatever the case, the bottom line is rolling circumference.......

this can get deep too - no pun intended, the outside diameter of a tire is what really counts, so what i would do is make a mark on your rear tire at 6 o'clock on pavement-mark pavement too, rotate forward in a straight line until tire rotates exactly 360 degrees and repeat marks on pavement. Measure between the two points on the pavement, this will be the rolling circumference of the tire. Now if you go down to your tire place you can do the same thing....only problem is that a tire that is not mounted on the tractor and loaded by the weight of the tractor will give a number slightly off.

But all that being said - if you are going to use 4WD in a location that will allow the tire(s) to slip, the problem will not be that bad. What kills the drivetrain is when the ratio is a little out of whack and the tires are on something that will not allow the leading tire to spin a bit.....people forget and leave the tractor in 4wd on pavement, and this is what kills the drivetrain.

 

[L4740]

Gingerheadman, what you found was more than likely used industrial or R4 tires. Not ag tires. Or what they call R1 tires. Ag tires would be a lot narrower and would not fit on the same rims. R4 tires are an option when you buy a BX.

 

[Gingerheadman]

Yeah Iam aware of that, I just called and ordered a new set of 29-12.5-15 in a ag tire it's $195 per tire installed. The used warehouse only had 1 available so new ones it is. I'll post a reply whether they work or not. Fingers crossed!

Yeah they are r-1's but it's the closest thing I could get to an ag tire without having to buy 4 new rims and 4 new tires