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420D Tire Change for Winter Conditions

HandLogger

Well-Known Member
Joined
Oct 21, 2007
Messages
108
Location
Berkshires
Occupation
Forest Land Management
Okay, so I've been telling myself for years that we need to do something about our tires. We're still running the Goodyear 340/80 R18 IND (fronts) and the Goodyear 19.5 LR24 IT510 (rears) that came from the factory with our CAT420D and, quite frankly, they leave much to be desired in the winter months.

First thought: Chains. Well, come to find out that we've only got about 2" of clearance between our rear tires and the inner fenders - so I'm being told that chains are out (for the rears).

Next thought: Ice Studs. I've been told that the shortest stud we should use with our machine is 18mm and, according to the stud manufacturer, we must have at least 17mm of lug left on the tires - we don't.

Latest thought: New Tires (all round) and Ice Studs. Finding rear tires hasn't been a problem - the 19.5 L24 is readily available and relatively decent deals can found. The fronts, on the other hand, have been a problem. The (OEM) 340/80 R18s that CAT installed on our 420D are spec'd to run on an 11" wheel. The 12.5/80 x 18s that we're being told to convert to -- due to the exorbitant price of the OEM size -- are spec'd to run on a 9" wide wheel.

Is it possible to install a commonly found 12.5/80 x 18 on an 11" wide wheel or, worst case, is it time to buy 9" wide wheels for the front of our 420D?

Thanks for your time ...
 

Catback

Well-Known Member
Joined
Sep 17, 2013
Messages
110
Location
WI
That tire is designed to mount on a 9" rim. If you can get it to seal, you will be flattening the tread, and causing premature wear. How much so? I do not know.

Then there is the load rating. Clearly, you do not want to maxxing out the load with a rim that is 17% smaller than designed. In fact, you may only want to hit half of the load rating.

There are plenty of shops that will make you rims. Why not install the correct rim? I guess at the end, you have to decide the cost/risk analysis.
 

mitch504

Senior Member
Joined
Feb 27, 2010
Messages
5,776
Location
Andrews SC
The other thing to remember is, You need to stay the same height or you can damage components on a 4x4
 

monster76

Senior Member
Joined
Aug 14, 2013
Messages
526
Location
Miami Fl
Occupation
Contractor
If my math is correct there is a 2" difference in tire size between the 2
 

PDG X

Well-Known Member
Joined
Apr 27, 2009
Messages
175
Location
Florida
Occupation
Owner Operator
There are axle spacers available if you want to add chains to the rears.
 

firebird_ak

Member
Joined
May 27, 2013
Messages
12
Location
alaska
CAT just quoted me 2000 bucks for a set of spacers for a 416D! It looks like the spacers are only a flat piece of 1.3 inch plate with holes drilled through. That price was including bolts and washers (800 bucks worth)
 

HandLogger

Well-Known Member
Joined
Oct 21, 2007
Messages
108
Location
Berkshires
Occupation
Forest Land Management
UPDATE and a couple of new questions

UPDATE:

After leaving messages on a few different phone extensions, I’m now being told that the wheels on our 420D are CAT Part No. 1350786, which is spec’d at a width of 228.6mm (barely under 9 inches). This is a pretty interesting revelation – considering that all of the industrial tire suppliers I’ve spoken to say that the OEM tire (the Goodyear 340/80 R18 IND) is supposed to be mounted on an 11 inch wide wheel.


monster76 said: If my math is correct there is a 2" difference in tire size between the 2

As for the math:

.80(340) = 272 → 272 mm = 10.7 inches → 2(10.7) + 18 = 39.4

Therefore, the expected height of a mounted 340/80 R18 is 39.4 inches

.80(12.5) = 10 → 2(10) + 18 = 38

Therefore, the expected height of a mounted 12.5/80 x 18 is 38 inches

39.4 – 38 = 1.4

Therefore, the height difference between the two tires in question should be 1.4 inches

Considering the fact that most of the 420Ds out there came from Peoria equipped with 12.5/80 x 18 front tires, is it safe I to assume that the 1.4” height difference is within the design capabilities of the machine???

What are your thoughts on this?


firebird_ak said: CAT just quoted me 2000 bucks for a set of spacers for a 416D! It looks like the spacers are only a flat piece of 1.3 inch plate with holes drilled through. That price was including bolts and washers (800 bucks worth)

After speaking to the tire suppliers about a direct replacement for the radials that came from the factory with our 420D – and the extremely high cost of doing so – I wasn’t exactly motivated to research wheel spacers. In short, it doesn’t surprise me that the spacers are being quoted at such a price.

Next Step:

Put my Icetrekkers on my boots, try to get back up our steep ice-covered access road and search the front wheels of our machine for a CAT part number. If the number in the wheels matches what I'm being told, I'm one step closer to converting to the smaller, more common and much cheaper 12.5/80 x 18 tires.

By the way, anyone on the board ever seen a backhoe running on Ice Studs?
 

monster76

Senior Member
Joined
Aug 14, 2013
Messages
526
Location
Miami Fl
Occupation
Contractor
Nice you actually did the math, I used a more technical method SWAG (scientific wild ass guess) but in all honesty id call cat and ask to speak to a service rep or any one who may know that answer and see what they recommend maybe the dealer replaces all the front with 12.5 80 18 and has no ill effects or something to that extent.
 

Deon

Senior Member
Joined
Jul 25, 2010
Messages
768
Location
Nova Scotia, Canada
Handlogger,
1.4" difference in diameter translates to 4.4" in travel distance on every wheel turn. Multiply diameter difference x 3.14.
I would think that would be a big strain on tires and drive train. Also, you won't need to use your brakes because the machine will stop as soon as you hit neutral.
 

Delmer

Senior Member
Joined
Jan 3, 2013
Messages
8,865
Location
WI
You really have to measure the inflated tires to get an accurate comparison, but I'm gonna say a few% isn't going to make a difference. The new tire is probably as tall as the worn old one. Of course new rears will affect the proportion.

My understanding is that 4wd does not match speeds exactly, the front pulls slightly more. Of course that all changes as the tires wear. The strain only develops on paved surfaces, opinions?
 

firebird_ak

Member
Joined
May 27, 2013
Messages
12
Location
alaska
A local machine shop would be awesome if I had the rig here, but it's out in the bush. I tried to get a picture of the spacers, but Cat didn't have one on the computer, just a diagram. If it is just a flat plate, then wouldn't the bolts be taking all the stress instead of the wheel fitting to the axle? I've never had the rims off on the 416D (foam filled tires) but when I change a car tire it seems that the wheel is only held on by the bolts (to the rotor) but supported by the inside radius of the rim fitting onto the axle. Sorry, if I hijacked your thread!
 

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Tinkerer

Senior Member
Joined
May 21, 2009
Messages
9,342
Location
The shore of the illinois river USA
I have had wheel spacers made and they had the raised part the rim rests on. The bolts carried no more stress than when the wheels were on the axles without the spacers. I purchased them on the internet. They were a perfect fit.
 
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