Tires 16.9 x 38 vs 15.5 x 38

deererod · May 17, 2013

I am new here so I apologize if this in the wrong forum. I have a John Deere 2640 that needs new rear tires. The tractor currently has 15.5 x 38 on it and a few years ago I bought some nice used 16.9 x 38. I was about to put the 16.9's on this weekend when a friend said it wouldn't pull nearly as good. Now after some research I realize the 16.9 is a good bit taller than the 15.5's (never bothered to measure either before). The tractor is kind of slow on the road. Would the 16.9's be a good fit on the rear of a 2640 or should I find some 15.5's? This might be a silly question for someone who already owns a set of tires to ask but this will probably be the last set of rubber this tractor will ever need and I don't want to be disappointed. Thanks in advance.

Creamer · May 17, 2013

i'm not real familiar with that tractor but do you mean 16.9 x28. 38's are a very tall tire for utility tractor. I assume the 15.5 are 28 s as well.

Since you already have the tires I would put them on and see what you think. A lot of it depends on if you are out of engine or out of tire. If you are out of engine then you may not want to go bigger but if you are out of tire as I suspect you are with that much hp on those tires the 16.9s should work fine.

RaydaKub · May 17, 2013

I don't know the tractor at all, but do you have 4x4? You could run into problems with the rear pushing the front end around, and eventually gearbox failure on the front end.

MHarryE · May 18, 2013

Checked some sites and found that 16.9 x 28 is the standard tire for your tractor and was the tire used in the Nebraska tractor test. Unless someone swapped rims out or the 15.5 was an available option, the 16.9 should be right. I checked the Titan Tire site and found the 16.9 x 28 takes a 15 inch wide rim. They don't list a 15.5 x 28 but a 15.5 x 38 takes a 14 inch wide rim. If your rims are 14 inch I'm not sure how they will fit but in the past we have up sized tires keeping the narrower rim width without problem, but those were tube type. Not sure if you are using yours tube type or tubeless.

jenkinsph · May 18, 2013

I had a 3020 with the 15.5 38 tires that were worn badly and replaced them with 16.9 38 tires. I vaguely remember that the only problem was one implement didn't have enough clearance to hitch up because the tires stuck out farther to the rear. You may need to drop one gear to get the approximate travel speeds similar but overall it worked well enough. A 3020 and 2640 should be very similar in power (70 pto hp) so since tires are so expensive I would give it a shot after comparing the length of the lower hitch arms.

RickB · May 18, 2013

Your friend's opinion does not match up with my experience. swapping to 16.9x38 tires from 15.5x38 will make a big difference in traction in most conditions. They are an acceptable fit on 14" rims. You already own them, put them on. The same swap made a huge improvement on a 4010 I once owned.

Ignore the guys who think you can't read numbers on a tire sidewall. 38" tires were optional on most Deere utility tractors and certainly were available on a 2640.

jenkinsph · May 18, 2013

RickB said:
Your friend's opinion does not match up with my experience. swapping to 16.9x38 tires from 15.5x38 will make a big difference in traction in most conditions. They are an acceptable fit on 14" rims. You already own them, put them on. The same swap made a huge improvement on a 4010 I once owned.

Ignore the guys who think you can't read numbers on a tire sidewall. 38" tires were optional on most Deere utility tractors and certainly were available on a 2640.

I would agree and add that 38" rims were very popular for 2640 tractors and other older models. Now I see alot more tractors with smaller diameter with wider rims and tires in the newer tractors.

art · May 18, 2013

When that tractor was made many of them were set-up for cultivating which required ground clearance and a narrow tire. To change out to the 16. RichB is right on! better ground speed as well as a big gain in traction. I wouldn't worry about filling them if you really want to enhance the performance unless you have a loader.

MHarryE · May 18, 2013

Just curious. John Deere doesn't list 38" tires as an option. Standard rims are 15" width by 28" diameter. Operator says tractor is slow. If someone put 38" tires on it would be very fast. Unlisted option by Deere or is my info obsolete?

RaydaKub · May 18, 2013

Yeah, a 28 inch rim to a 38 inch rim would make that thing really go!

RickB · May 18, 2013

MHarryE said:
Just curious. John Deere doesn't list 38" tires as an option. Standard rims are 15" width by 28" diameter. Operator says tractor is slow. If someone put 38" tires on it would be very fast. Unlisted option by Deere or is my info obsolete?

PC 1539 page 80-22 clearly shows double bevel rim part # R31491 with the note (15.5x38 tire).

Edit: the following page shows two additional part numbers for 38" rims.

Creamer · May 18, 2013

Now my curiousity is rolling. How can a tractor be set up for both 28 and 38 inch rims? Did Deere put in a different rear end? If not then like MharryE says this thing should fly. Do the fenders not go over the rear tire? How do they not hit or are there different fenders? What about drawbar height - you are talking about 5" in drawbar height difference?

RickB · May 19, 2013

You can study the parts catalog (like I did to confirm what I already knew about tire sizes) and see if there were ring & pinion choices.
There were at least two fender styles, and flat top fenders are height adjustable (again, the parts catalog can answer your question).
Drawbar height? Check tire manufacturer's websites end compare the loaded radius numbers for the sizes in question. Will they vary by 5"? Maybe, maybe not.
It isn't as simple as subtracting 28 from 38 and dividing the answer by 2.
Drawbars are offset and could be flipped so the offset can be up or down. Yes, PTO shaft / hitch geometry needds to be considered.

If you are really curious, you can answer many of your own questions and learn how to answer similar future questions.
Additionally, verifying info like that avoids all the TBN-type banter and drama about who knows what and why that is seen in countless other threads.

Verticaltrx · May 19, 2013

Deere used to offer most of the utility tractors in multiple configurations. Basically there was a low-utility, utility, and row-crop versions and multiple variations of each(sometimes also a mudder and high-crop version as well.) There are three tractors of the same size/vintage around here setup three different ways:

Our 2550 Row-crop:
-8/4 TSS transmission with independent PTO
-rack and pinion rear axle with cast wheels, 15.5-38" rubber
-wide adjustable front axle, 7.50-16 tires
-large row crop style flat top fenders
-deluxe lever release SCV valves and extendable lower draft links

Neighbor 1's 2550 in the low utility config (MFWD with loader)
-standard 8/4 transmission with left hand reverser, continuous running PTO
-flange rear axles, steel wheels, 28" rear rubber (I think they are 16.9-28's but not sure)
-mfwd, so obviously a different front axle
-small shell type rear fenders, deluxe lever release scv valves and non-extendable draft links

Neighbor 2's 2350 in the standard configuration: (2wd with loader)
-standard 8/4 transmission with left hand reverser, continuous running PTO
-flange rear axles, steel wheels, 16.9-30 rear rubber
-slightly narrower but still adjustable front axle, I think it has either 11L-15 or 10-16 front tires
-row crop fenders, standard style scv valves and non-extendable draft links

Obviously the row crop version is sold more for field work, the low utility more as a loader tractor and the standard utility as just an all purpose tractor. There is a big difference in ground clearance and overall height between ours and neighbor 1's 2550. Neighbor 2's is closer in height to ours vs the low utility. The drawbars can be turned up or down to accommodate this, not sure about differences in the 3pt. In the early years (10/20 series) they really sold them based on those configurations, when you get to the 30/40 series the definitions weren't quite as clear, and by the 50/55 series they were more 'option packages' as opposed to different models. I don't know if they used a different gear ratio for the different tires, but my guess is they did not. I do know that for the 2550 there is a 16mph tach/speedo and a 20mph tach/speedo, which I guess would correlate to tire size (ours uses the 20mph).

As to the OP, I'd be inclined to try mounting them up since you already have them. If you were buying new I would have stuck to the 15.5's for reasons mentioned (change in speed/gearing, 3pt geometry, etc). If you do want to go back to 15.5-38's I'm sure you could sell those 16.9's for a fair price.

Attached is a pic of ours in the row-crop config with 15.5-38's

Creamer · May 19, 2013

Thanks Verticaltrx. I never knew that Deere did that but it makes a lot of sense. Appreciate your spelling it out!

TheEquineFencer · Jun 27, 2013

If you do not like the 16.9-38 tires, let me know I need a set. My tractor and shop burned and I need a set. If you know where I can get another used set that would be great!