# 1989 JD 950 4 wheel drive w/loader



## Charles In Maine (Apr 6, 2021)

My tractor that I just acquired has front 16” wheels and 7x16 ag tires
rear 12.4 x28 rear at tires on 28” rims

the manual calls for 5 x 15 ‘’. front
and 11.2 x 24

were the larger wheels an option, They have been on tractor for over 20 years

i also wonder about ratio of larger wheels/tires

newbie in Maine
help much appreciated

charles


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## SidecarFlip (Mar 25, 2021)

The ratio between the front and rear wheels (outer diameter) is called lead-lag and it must be within the correct parameters or excessive wear to the tires will result, but more importantly, incorrect lead-lag will impose a constant stain on front axle components.

Don't know what the correct lead-lag ratio for your JD is, but I bet any JD dealer can tell you, they know.

The problem is, when you engage the FWA and lock the drivelines, if the L-L ratio isn't correct, the front axle components are constantly putting a strain on the gearbox. With my Kubota M9's. Kubota has wisely put a splined coupler between the input stub that drives the front end pinion and the driveshaft that that goes into the gearcase. That splined coupler is not hardened but the driveshafts are so if the L-L ratio is incorrect, the coupler fails and can be replaced, which is much cheaper and easier to do than replacing driveshafts or ring and pinion assemblies. Because I road mine quite a bit, I keep a couple splined couplers on hand, just in case. Not sure how JD addresses that, only Kubota.

You need to measure the outer diameters of the tires when determining the L-L ratio.


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## SidecarFlip (Mar 25, 2021)

A good telltale sign of incorrect L-L is how the tread is wearing on the front tires. On R1's like you (and I) have. If the L-L ratio is incorrect, the tread bars will cup toward the rotation of the tire. Looks to me like you don't have an issue so I'd say when the PO went to the larger diameter, he also adhered to the correct L-L ratio.


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