original tire bridgestone 13.6x26 (ag style) is dry rotted and split open . tread is very good i’d say 1” or deep . it’s inflated overall height is about 48” tall . local tire shop found me a replacement, it a speedway tire “gripking “ and is a nice replacement, BUT is 51” tall ((mounted and inflated) . first question is is it mechanically safe to run this tire , which is plus 3” tall on my tractor . i was surprised on overall measurement and was considering buying a second tire but not sure it’s ok to run without damage to tractor internals… help !
yanmar 336dtire help
- Thread starter hdwrench1
- Start date
- Views: 3605
rScotty
Super Member
- Joined
- Apr 21, 2001
- Messages
- 9,715
- Location
- Rural mountains - Colorado
- Tractor
- Kubota M59, JD530, JD310SG. Restoring Yanmar YM165D
NOT mechanically safe. It will overwork the differential in 2 and 4wd, and will also create some serious torsional stress i.e. "shaft windup" in the gear and driveshafts when you are in 4WD.
Replace with a pair of matched rear tires and check the tire catalogue specs to make sure the new ones have the same "loaded circumference" as the tires they are replacing.
That requirement is not peculiar to Yanmars, it goes for every sub, compact, and utility 4wd tractor on the market - and most of the full size ag tractors as well.
Our tractors are 4wd Assist; they are Not Full Time 4wd.
good luck...BTW, nice tractor. We had a YM336D and wish it was still here.
rScotty
does anyone know of a replacement ag tread tire that measures overall 48” tall mounted and inflated ? proper replacement for a yanmar 336d ….the existing tire i’m trying to replace calls out -13.6-26 , there is only 2 numbers on original tire and the replacement from speedway tire (mfg)
Last edited:
rScotty
Super Member
- Joined
- Apr 21, 2001
- Messages
- 9,715
- Location
- Rural mountains - Colorado
- Tractor
- Kubota M59, JD530, JD310SG. Restoring Yanmar YM165D
Tall isn't what you want. You need to find a tire catalogue for the original tire and look up the spec called "rolling circumference". You can also measure your existing rolling circumference.
Then go to tire catalogues for existing tires where you can always find that spec listed and choose a tire that is the same or real close.
rScotty
Super Member
- Joined
- Apr 21, 2001
- Messages
- 9,715
- Location
- Rural mountains - Colorado
- Tractor
- Kubota M59, JD530, JD310SG. Restoring Yanmar YM165D
What were your tires originally??
Yanmar originally had a rear tire 12.4/11 x 28 on the YM336d, but they changed the YM336d tire size
about half way through the model run to 13.6 x 26 Firestones. Of course this also meant that they had to change the internal gear ratios front to back...which they did.
I have the notes for our YM336d which was the later model.
The original OEM rears on our YM336 were Firestone (BridgeStone) All Traction Field & Road R1 6 ply.
13.6 x 26 6 ply tire mounted on a 12 x 26 rim*
Front to Back internal gearing was 1.694:1
The unloaded height of that tire is 49.5"
The rolling circumference (RC) Tire spec is 147" supporting 2760 lbs load @ 22 psi
Rolling circumference will vary with the load.
Measured RC on our tractor with a loader and back blade I got 147" to 148.5".
That was done with a series of averages on hard pack and pavement both 2wd & 4wd.
The problem was that Firestone doesn't make that old tire anymore. They make a tire that measures the same diameter and RC, but it is made to measure that on a modern 14.6 x 24 rim. So that would need a different wheel... ugh! Maybe someone else makes a tire to fit your rim that is the right height & RC.
The original OEM fronts on our YM336D were OHTSU 8 x 16 4ply R1 ag. mounted on a 16x6 UA rim*
*note that rim width for tractor tires was originally measured on the INSIDE faces of the rim where the tire contacts the rim.
you should check with each wheel or tire manufacturer to see how they measure width because automotive tires are measured differently for width.
rScotty
Last edited:
my tires are the bridgestone 13.6 x26 . i measured the rc to be just shy of 48” . i have purchased a set of deestone replacements (8 ply ) , which measures about the same before mount and inflate . i also bought a set of deestone 8x16 fronts to match . hopefully it all works out when there mounted …. i will post results . i am looking for to completing this tire saga . kinda why i did all four ….should be a long time before this tractor needs tires again ….
bmaverick
Super Member
- Joined
- Sep 17, 2013
- Messages
- 6,831
- Location
- Beloit-WI
- Tractor
- Yanmar YM2610 ■YANMAR GURU■ EXTRAORDINAIRE
Make sure the front rims are identical size replacements. Your YM336D is 4WD and the tire ratio front and back need the perfect lead and lag range values to perform flawlessly.
Do you have the YM336 manuals? We got them at the YTOG for free.
main groups.io Group
*Yanmar Tractor Owners Group.* **US models, Gray market models, Cub Cadet models, RK models, even our green siblings known as Deere's. ** *A valuable source for owners of Yanmar tractors.* * * *If you would like to join our group, then click on the +Join This Group button below left. *NOTE: A...
yanmar-tractor-owners.groups.io
i have the factory repair/ operation manual , i am looking for the parts manual…fo you know of a source for the front rims …? hoye is on back order . found them at asap/ old tractor but the bad reviews and lack of info concerns me ….
rScotty , do you have the r.c. of the front tire handy ? i’m running an 8”x16”. ?
rScotty
Super Member
- Joined
- Apr 21, 2001
- Messages
- 9,715
- Location
- Rural mountains - Colorado
- Tractor
- Kubota M59, JD530, JD310SG. Restoring Yanmar YM165D
Ahh... a very good question ! Congratulations on thinking it through.
As you are finding, getting the right tires on a part time 4wd tractor can be a lot of skull work.
My stock fronts on the 336 were 8x16 OHTSU 8 x 16 4ply R1 Ag tire mounted on 16x6 rims!!
Rolling Circumference (RC) is listed as 90.4"
Overall loaded diameter is 31.1" and loaded radius is 14.4"
That sounds like the wrong tire on the wrong rim, wrong, but it turns out to be correct. The reason is tires tend to be measured on the outside width at their widest point, where rims are always measured between the inside faces of the rim where the tire contacts the rim. So a 16x8 tire on a 16x6 rim is just fine...even normal.
You may notice that in tire specs, the loaded diameter is NOT twice the loaded radius. The loaded tire is oval rather than round and the axle is nearer to the ground than to the top of the tire. That is why RC is not a simple calculation but needs to be measured.
I've got a stack of notes on tire swaps on the Yanmar 336 and for some reason I kept them.
Back about 1995 and just for fun, I measured the RC of our YM336D front tires and the number i got Was 90.25" in 2WD.
Measured 4wd* the RC is more variable and front tires measure too small & rears to large. I think that is because in 4wd the internal overdriven gear ratio causes the fronts to slip a little as they drag the rears.
So you end up measuring some mixture of F/R RC and traction of the measuring surface (asphalt)
I also measured the internal F/R ratio on our Yanmar 336d (late model) by jacking up one side in 4wd and turning the rear tire by hand. Welding rod ground to a point and clamped to the frame formed pointers.
It took 36 turns of the rear wheel to return both front and rear wheels to their original starting posiitions & turning the rear caused the front to turn 61 revolutions. Hence: 61/36 = a internal ratio of 1.694:1
The shop manual says that the ratio is 1.743:1, but either they are incorrect or else the older YM336d was different. Note that 62/36 would sure be an easier gear set to design with and also to machine - and at 1.722:1 it would almost match Yanmar's own spec. But I measured it several times on both sides and got what i got.
Using my measured numbers for gearing and RC, gives an OEm overdriving ratio of 4.7%. Frankly, I think that part time 4wd tractors should be designed closer to 2.5% overdriven. There is no downside in designeing the ratio even closer to zero as long as tire mfg differences & wear does not cause the overdriving percentage to be negative. If so, steering suffers.
YMMV, rScotty
* I now think that accurate RC measurements should be done in 2wd. Again, measure RC in 2wd.
rScotty
Super Member
- Joined
- Apr 21, 2001
- Messages
- 9,715
- Location
- Rural mountains - Colorado
- Tractor
- Kubota M59, JD530, JD310SG. Restoring Yanmar YM165D
I don't recall that post - hope it was the same number as in the post directly above. That post above is correct.
bmaverick
Super Member
- Joined
- Sep 17, 2013
- Messages
- 6,831
- Location
- Beloit-WI
- Tractor
- Yanmar YM2610 ■YANMAR GURU■ EXTRAORDINAIRE
Go back to my 1st post here. We got the parts manual and its free in PDF download.
The Yanamr Tractor Owners Group is the oldest support group with over 35+ years. It began on GeoCities years ago.
Here are some similar links:
Buying Advice
Looking to buy my first tractor