Look on the Dorman wheel nut chart. Dorman Products - Wheel Hardware Look under "Wheel Lug/Bolt Sizing" there are charts.
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For all the new MT125 owners out there
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rider7767
Platinum Member
I hate to get this technical, but the measurements you provided are out of tolerance for a 7/16-20 bolt. According to the Machinist's Ready Reference 10th edition, The max diameter for a 7/16-20 bolt is .4050 inch. Min is .4014 inch. I am about 99% sure it is a 12mm bolt with a 1.25mm thread pitch. The Max pitch diameter for M12-1.25 is 0.43937008 inch. The Min pitch diameter is 0.434173228 inch. The 7/16-20 is very close to the eye. It is for each of us to make our minds up if it is close enough.
Here is the info on the metric bolts External Metric Thread Table Chart and Fastener Sizes M1.6 - M18 | Engineers Edge
mslisaj
Gold Member
- Joined
- Nov 3, 2017
- Messages
- 323
- Location
- Klamath Falls, Oregon
- Tractor
- LS MT125 Loader/Backhoe John Deere Sabre Lawn tractor w/Snow Blade
My technical qualifications as a machinist are nonexistent. My father taught me to read a micrometer too many years ago to remember and he was a journeyman machinist. I give that up and in my post above I mentioned I am up to being corrected on my information but here are my references pictured below. I am in the ballpark as they say for the dimensions for a 7/16 bolt. Pitch size and angle degree I don't have that information and I can only say that a US made SAE tap settles into the threads like it was cut for it. I also have a metric thread pitch gauge and the 1.25 gauge was close on my bolt but the SAE 20 settled into the threads perfectly. At least to my old 63 year old eyes and fingers. If I could find the 7/16-20 tapered lug bolts I would put them into my tractor torque them to specs and not give it another thought. But I can not find that these bolts exist. Now, if that metric bolt is that close too and it was threaded to the shoulder I would used it if it threaded in there nicely and torqued up.
The simple fact is none of us like the wrong part for the application and a regular bolt and lock washer against a tapered wheel hole on a rim is the wrong part for that application. We will agree on that and it's that fact that has us all scratching our heads why LS did this. I may offer up that the wheels are stardard off the shelf items. Their engineers, when designing these axles did the calculations and a bolt in "the size range" of a SAE 7/16 fine threaded bolt had the clamping force range to do the job. Then it was discovered that there is no off the shelf bolt in that size range with a tapered shoulder with threads cut to that shoulder. So a standard bold was used as the clamping force is what is truly doing the job. Again I am no expert and again I am easily corrected, but these are just my observations after being in this kind of business all my life as a mechanic. Now I'm an retired old lady. But I love my tractor and I love these discussions and thank you gentlemen for entertaining my thoughts here.
Respectfully,
Lisa
The simple fact is none of us like the wrong part for the application and a regular bolt and lock washer against a tapered wheel hole on a rim is the wrong part for that application. We will agree on that and it's that fact that has us all scratching our heads why LS did this. I may offer up that the wheels are stardard off the shelf items. Their engineers, when designing these axles did the calculations and a bolt in "the size range" of a SAE 7/16 fine threaded bolt had the clamping force range to do the job. Then it was discovered that there is no off the shelf bolt in that size range with a tapered shoulder with threads cut to that shoulder. So a standard bold was used as the clamping force is what is truly doing the job. Again I am no expert and again I am easily corrected, but these are just my observations after being in this kind of business all my life as a mechanic. Now I'm an retired old lady. But I love my tractor and I love these discussions and thank you gentlemen for entertaining my thoughts here.
Respectfully,
Lisa
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rider7767
Platinum Member
These diameters listed are prior to cutting threads. Is the standard max/mins before cutting. The outer diameter of the threads will be smaller after they are cut. I may cut one on my lathe if I get time. I worked in the shop all day. Dang knee is killing me. Concrete!
mslisaj
Gold Member
- Joined
- Nov 3, 2017
- Messages
- 323
- Location
- Klamath Falls, Oregon
- Tractor
- LS MT125 Loader/Backhoe John Deere Sabre Lawn tractor w/Snow Blade
Well rider I'm in the same boat. Knees on concrete working on a Shriner's Tin Lizzy for a local parade. We're not that old and we well recover. Take care my friend.
Lisa
Lisa
Smoreau
New member
The correct size for all 20 bolts is 7/16-20, and yes it has metric markings on it. My dealer told me that it is a standard in the US for wheels to use SAE. Bolts. Only reason I know this is i removed one rear wheel to remove the lower 3 point pin to straiten out a bent sway link. About 4 hours of run time I started to hear a clunking sound in the transaxle when turning. Could not find were it was coming from tell about 1 hour later of run time. It egged out the rim to the point it almost would fall off the tractor. Ordered a new rim for $111.00 and my dealer gave me all new studs with the trapper head for free. I new it was my fault as they were not tight enough after seeing the rim and I had it off last. My dealer sent the studs in the mail about 1 week later, but I already installed ones that I had as I am a Wheel Horse collector and I have acuemulated many of them over the years.
Smoreau
New member
Another problem I have noticed and seen a few on here is the play in the pedals after 50+ hours of use. The rollpin was not pwt in all the way and can get to the point it shears off. I found the problem doing my 50 hour service and removed the floor pan and replaced it from my local hardware for the big price of. 50 cents!! This took me about 10 min to repair and not worth the trip a hour away to take it to my dealer. Another issue was on my loader and backhoe control levers like to come loose. Tighned them up 2 times now and they are loose again going to try locktight next.
rider7767
Platinum Member
I will respectfully disagree. SAE bolts do not come with Metric markings. The 7/16-20 are very very close to a M12-1.25, but the 7/16-20 are not the right thread. I finally got around to putting a thread gauge on a lug bolt of my MT125, and it measures M12-1.25. 7/16-20 and M12-1.25 are hard to tell apart with the eye, but they will be out of tolerance. It will most likely come loose over time. I have cut threads on lathes many times, and a thread gauge does not lie. A 15mm wrench will fit a 5/8" nut, but it is still not a 15mm nut. M12-1.25 are really unusual and it really confused me why LS went with this bolt with out a tapered heads. I stopped by a dealer the other day and checked the new LS MT125s. They all still have straight bolts. LS does a few quirky things, but still makes a solid tractor.
rider7767
Platinum Member
I had the same issue with the roll pin as did a few other people. I put a video on YouTube about it. I have not had the control lever issue, but I will keep a look out. Thank you for the heads up.
Someone recommended using safety wire thru the roll pins so they couldn't back out. I would imagine a greased piece of mechanics wire would last for years.