Tires John Deere 770 R4 tires?

[Indiana Deere]

I have 1996 John Deere 770 with the Ag type tires on it and would like to put new R4 tires on my old Deere. The front ag tires are very whimpy when doing loader work with heavy loads. I would like to hear from anyone who has made the switch from Ag tires to R4s. I've looked at a lot of posts and I think I can use my rear rims, but will need to get new front rims for the loader tires. I believe I read where someone used front rims from a 790. Please give me the rim sizes and tire sizes you used. I really don't use the tractor for any farming, just for discing up a small food plot. Mainly dirveway maintenance, clearing trails in woods and some bush hogging.

 

[dieselram]

Find Whitey, he has a 770 with R4s. I think they were take offs from a 790.

 

[gkhammond]

ok this is the first time I've posted something so please bear with me. However I just got done converting my 770 with turf tires to R4. It is a not easy. I'll try and keep it short. first and most important you need to keep the MFWD ratio correct! or you could damige your tractor. 770 and 790 have the same MFWD gear ratio. I got this info from john deere. So it is posible as I have done to put R4's same size as 790 on a 770. these sizes are. Back 15-19.5 front 25x8.50-14 In my case I had to buy new back rims. and there size is 12.25-19.5 My cost about $375 each. My front rims worked fine becouse tire size was the same R4- turf. It is not the same rim for ag tires. looks like ag front is a 6-12 rim Jd part # Am876649 rear ag is 11-16 jd part# AM877014 so you will need all 4 rims. Like I said not easy. I found tires fronts for $114.00 and rears for $371.00 seems pretty close to going price for my area. If you find a set of turf tire rims for a 770 there is anther tire size you can use but they are smaller and will gear your tractor down. 12.4-16 rear and 23-8.50-14 front. I can give more info if needed. however this is not the way I went do to gear down. good Luck.

 

[irwin]

Like gkhammond said you can buy all four rims for the 790 or you can reuse the rear rims and just buy front rims. I had a 770 with turfs and did the homework to swap to R4 tires. 12.4-16 trac loader tires in rear (they'll go right on your rear rims, and 23x8.50-14 trac loader tires in front. The front rims are the same as with turf tires. Deere part number for front rim #7JA - 14WDC .

See this site. John Deere - Parts Catalog

The MFWD ratio for the 770 and 790 is 1.571 (I got the ratio from Deere) and with the above match the front lead is within specs.

Here's my thread on the subject. http://www.tractorbynet.com/forums/john-deere-owning-operating/99396-790-770-mfwd-ratio-r4.html


Here's what it looked like with R4's.

 

[Whitey]

Yes it can be done............but you do have to be concerned about the rolling circumference size of the tires. I will have to dig up my files to see what size my rear rims were.....I did have to buy new rims for the front. In the mean time post your rim sizes while I look for mine. Irwin has the right tires and rims listed.........I can give you the exact Titan Tire model number once I find it.

 

[Whitey]

OK Indiana Deere.........you are in luck......I found them. Once again you wil have to check your rim size.......but the rear rims on mine were 12.4-16 and the Titan R4s went right on with the right loaded circumference. I had to buy new rims for the front which as you will see the tires as 25x8.50x14 Titan. These were done in July of 07 so the numbers should be good.

Good Luck

 

[lhobson]

OK Indiana Deere.........you are in luck......I found them. Once again you wil have to check your rim size.......but the rear rims on mine were 12.4-16 and the Titan R4s went right on with the right loaded circumference. I had to buy new rims for the front which as you will see the tires as 25x8.50x14 Titan. These were done in July of 07 so the numbers should be good.

Good Luck

These tire sizes are starting to blur. You put 25x8.50-14 R4s on the front and 12.4-16 R4s on the rear. Correct ? Right now I've got the same size R4s as you do on the front but I have my original 13.6-16 turf tires on the back. (Judging from the attached Adobe file, I have the exact same front tire as you do.) The original front turf tires wouldn't bear up under the weight of a full bucket of dirt. Now that I have this hybrid on my 790, I'm concerned about the rolling ratio. Should I be ? Note that I doubt if I can go R4 on the rear because of the belly mower. There's very little clearance.

 

[Whitey]

These tire sizes are starting to blur. You put 25x8.50-14 R4s on the front and 12.4-16 R4s on the rear. Correct ? Right now I've got the same size R4s as you do on the front but I have my original 13.6-16 turf tires on the back. (Judging from the attached Adobe file, I have the exact same front tire as you do.) The original front turf tires wouldn't bear up under the weight of a full bucket of dirt. Now that I have this hybrid on my 790, I'm concerned about the rolling ratio. Should I be ? Note that I doubt if I can go R4 on the rear because of the belly mower. There's very little clearance.

I cannot speak to the clearance problem........but yes the documents I have posted are what I have on my tractor. The rear tires are 12.4-16 that originally had ag tires. The R4s from Titan have the correct rolling / weighted circumferece that was called out for from JD. The front rims that I bought are suited for turf or R4s and speced out the same.......I have not had any problems with them under any type of weight. If you search this subject you will find the equation / ratio posted in a previous discussion.

 

[lhobson]

I cannot speak to the clearance problem........but yes the documents I have posted are what I have on my tractor. The rear tires are 12.4-16 that originally had ag tires. The R4s from Titan have the correct rolling / weighted circumferece that was called out for from JD. The front rims that I bought are suited for turf or R4s and speced out the same.......I have not had any problems with them under any type of weight. If you search this subject you will find the equation / ratio posted in a previous discussion.

Your ratio equation was on the pdf file you attached. It yielded a 7.11% lead. What's an acceptable range ?

 

[irwin]

These tire sizes are starting to blur. You put 25x8.50-14 R4s on the front and 12.4-16 R4s on the rear. Correct ? Right now I've got the same size R4s as you do on the front but I have my original 13.6-16 turf tires on the back. (Judging from the attached Adobe file, I have the exact same front tire as you do.) The original front turf tires wouldn't bear up under the weight of a full bucket of dirt. Now that I have this hybrid on my 790, I'm concerned about the rolling ratio. Should I be ? Note that I doubt if I can go R4 on the rear because of the belly mower. There's very little clearance.

Your ratio equation was on the pdf file you attached. It yielded a 7.11% lead. What's an acceptable range ?

If you want to have the same match for the front R4's that Deere uses on the 790 you'll have to do as Deere does and use 15-19.5 R4 tires on the rear..Of course you'll need new rear rims..or you can do what Whitey did and just realize your frt tires are a little bigger than spec.. Here's a link to the proper titan R4 rear tire. Titanï½® Tire catalog
With the 25x8.50-14 R4s on front you're a little closer to spec with the turf tires on the rear than if you bought 12.4-16 R4's..With your 13.6-16 turfs use these sizes for the ratio formula. Rears = 113" / Front = 79" .. That's the sizes that you have now.

With 15-19.5 on the rear use these sizes Rear = 117" Front = 79" this is the official Deere recommendation.

With 12.4-16 on the rear use these sizes, Rear = 110" Front = 79"

With 12.4-16 R4's and 23x8.50-14 the numbers are Rear = 110" Front = 71" ... ratio is 1.549 this equals 1.4% lead on frts..

Front wheel lead is used to aid in traction..everything I've read from experts leads me to believe that using Front assist is for needed traction, not for use all the time..unless you live in a traction limited area ie: mud, loose dirt. snow..etc. use 2WD until 4WD is needed. Less wear on the front differencial that way. Bottom line as long as it's fairly close and you use 4WD only in limited traction situations you'll be fine...leave it in 4WD all the time and you will put excessive wear on the front differencial.