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Unread 12-17-2009, 09:45 AM   #1
axehead
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tire size vs axle size debate

i've read the debates about 37" tires being ok or too big for D44's & chromod D30's.

my question is- is it more important the weight of the tire & rim rather than the height of the tire?

radials weigh more than bias

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Unread 12-17-2009, 10:34 AM   #2
mdm
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Weight and diameter both are factors but overall I'd say diameter is usually the killer. It's mostly about leverage and the bigger the diameter the more force is applied to the axle shafts.
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Unread 12-17-2009, 10:42 AM   #3
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Whatever the number designation on the axle is the size tire it is rated for. Dana 30=30" Dana 35=35" Dana 44=44" an so on up to tractor tires and a Dana 70! Also for every $100 you dump into an axle for strength it gains you another inch. So dump a grand into your front 30 and slap some 40's on it! Haha.

This is a can of worms you will never get a consistent answer on. Everybody has their own theory and experience.
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Unread 12-17-2009, 10:57 AM   #4
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Originally Posted by TJunk View Post
Whatever the number designation on the axle is the size tire it is rated for. Dana 30=30" Dana 35=35" Dana 44=44" an so on up to tractor tires and a Dana 70! ...
Have you got a reference for this? Or do we need to take a look at my signature?
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Unread 12-17-2009, 01:09 PM   #5
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I think the weight of the tire would be important. everyone says this axle is good for this size tire but what about tire tread? I would think that a swamper bogger would break an axle quicker than an AT tire.
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Unread 12-17-2009, 01:31 PM   #6
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How do you drive? Do you finesse your way over obstacles on the trail or are you more of give it a little more gas and Ill be over it? I have a friend with a 3/4T 10 bolt front (very similar to a D44) on 36" and he has stock axles shafts and he has no problems but he has a lot of finesse. On my CJ7 I have a 3/4T D44 front with a full floating 14 bolt rear and I will be running 37" tires and I will be a little harder then my friend is but Im not worried about breaking anything because if I do Ill either fix it by going chromoly or Ill start looking for a D60.
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Unread 12-17-2009, 05:17 PM   #7
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Quote:
Originally Posted by axehead View Post
i've read the debates about 37" tires being ok or too big for D44's & chromod D30's.

my question is- is it more important the weight of the tire & rim rather than the height of the tire?

radials weigh more than bias
Its alot of factors. Its motor HP, its tire weight and leverage to move the tires. Its driver skill and Tire pressure. So really when peaple say what is a safe limit with 37's i say what are you running.

I ran 37" red lable with a bone stock 60 and broke a stub in another jeep. I now run another bone stock 60 with 39" iroks in the jeep i have now and its been there for over 5 years now and not even a broken hub.
Bolth jeeps had a 6cyl and auto's.

So applacation is a huge factor. A built 350 jeep with a stick and a very light foot you could make a stock 60 last. A lighter jeep with a 6cyl and a auto with a very heavy foot and i bet you break. So the point is how you drive it and applacation.

A dana 44 with a beadlocked 37" trie is very heavy. You will be putting the balljoints under alot of stress and the small 297 U-joints. But a lighter tire with no beadlocks under the same rig will fair better, but will still be under abnormall loads with 37's.

Jason.
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Unread 12-17-2009, 06:40 PM   #8
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The "haha" was there for a reason.

Diameter and weight both are both a factor. In my opinoin diameter plays the biggest role. It is the leverage of the tire from a stop (like trying to climb something) that is most likely to break a shaft or u-joint. Think of it as trying to tighten a 1/4" bolt with a 4"handle ratchet or with a breaker bar with a 2 foot handle. With the small ratchet you should be able to get it good and tight. If you give it a quick jerk of the ratchet you may break the bolt. Mow try the same pressure with the long breaker bar. Odds are you will have pieces to put in the garbage can. A grade 8 bolt is just like stepping up to chromoly shafts. Yes, it is stronger but it is still only a 1/4" bolt. As long as you know the breaking point you can run whatever you want.

The weight of the tire comes more into play with speed. If one tire gets brought to a quick halt by some sort of resistance the other tire will become a sort of flywheel on the other end of the axle. The shafts now have to have the strength to absorb this force.
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Last edited by TJunk; 12-17-2009 at 06:45 PM.. Reason: spelling
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Unread 12-17-2009, 06:50 PM   #9
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Quote:
Originally Posted by TJunk View Post
A grade 8 bolt is just like stepping up to chromoly shafts. Yes, it is stronger but it is still only a 1/4" bolt. As long as you know the breaking point you can run whatever you want.
Yes but a chrome shafts and a 44 still have the balljoints as the weak point and with no further way of upgrading the axle of OEM balljoint. Plus i would not compare a chrome shaft dana 44 axle anyware the same strength as a stock 60 shaft, there miles apart in strength.
I'm not implying that your refering to that, ( the comparision of a dana 44 chrome shaft to a 60 ) I'm just tossing it out there that some peaple think when you upgrade the shafts on a 44 there in the 60 ballpark, far from it.

Weight has alot to do with the factor even with low speeds. If you have a lighter jeep its less leverage over a heavyer one, plus it take less to spin a lighter tire. Less effort to turn ( IE weight ) the less strain on the shaft to turn it.

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Unread 12-17-2009, 08:12 PM   #10
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Quote:
Originally Posted by TJunk View Post
Whatever the number designation on the axle is the size tire it is rated for. Dana 30=30" Dana 35=35" Dana 44=44" an so on up to tractor tires and a Dana 70! Also for every $100 you dump into an axle for strength it gains you another inch. So dump a grand into your front 30 and slap some 40's on it! Haha.

This is a can of worms you will never get a consistent answer on. Everybody has their own theory and experience.
You should just stop giving advice.
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Unread 12-18-2009, 02:30 AM   #11
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Originally Posted by DBLJ View Post
You should just stop giving advice.
Notice the "haha" on the end. Nobody should take that seriously.
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[QUOTE=mrblaine;8400660]I'm a huge fan of body lifts. In fact were I in your shoes, I would have gone for the 4" body lift and some 2" spacers on stock springs.[/QUOTE]
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Unread 12-18-2009, 02:43 AM   #12
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Originally Posted by jason m View Post
Yes but a chrome shafts and a 44 still have the balljoints as the weak point and with no further way of upgrading the axle of OEM balljoint. Plus i would not compare a chrome shaft dana 44 axle anyware the same strength as a stock 60 shaft, there miles apart in strength.
I'm not implying that your refering to that, ( the comparision of a dana 44 chrome shaft to a 60 ) I'm just tossing it out there that some peaple think when you upgrade the shafts on a 44 there in the 60 ballpark, far from it.

Weight has alot to do with the factor even with low speeds. If you have a lighter jeep its less leverage over a heavyer one, plus it take less to spin a lighter tire. Less effort to turn ( IE weight ) the less strain on the shaft to turn it.

Jason.
I agree completely. A Dana 30 will always be a Dana 30 and technically a TJ Dana 44 is still a Dana 30. Which is why I stated "It is still a 1/4" bolt" in my comparison. (now the nut might strip instead of the bolt break) They still share the common weak link. You just have to decide what "you" feel is the weak link. Everybody will have their own opinion as to what will fail first..u-joint, ball joint, knuckles, tubes. Some people know their limits and keep from breaking them.

Several people have had luck with their front 30's. Look at the TJ of the year contestants. Several Dana 30's with 35's and 37's. There is also a few threads on here about what was the last thing you broke in your Dana 30. Comes with great pictures and a couple video's.
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Unread 12-18-2009, 09:08 AM   #13
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In answer to the original question;
Tire tire weight is insignificant compared to the forces generated by running in low range (especially if the axle is correctly geared, or over geared for the tire size). Stopping distance can be reduced by using a lighter tire.

The best system (to help compensate for cases of heavy foot);
D30 is OK for tires for 33".
D44 is OK for tires to 35" or 36" (the small bolt pattern D44s are weaker than the old large bolt pattern D44s, with the possible exception of the front 2008+ Rubicon D44).
This has proven reliable for the most part but can be fudged a bit by driving carefully or with stronger parts.

Enjoy.
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Unread 12-18-2009, 12:49 PM   #14
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Brand new Dana 30, stock tires:







So much for theory . . .
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Unread 12-18-2009, 08:30 PM   #15
Happy Joe
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My D30 is quite old (81, if I recall, it has out lived a couple of Jeeps) but I have also used 87 high pinion and 85 wide track D30s). No issues with any of them with 12.50 x 33 and 35s (mud tires) used in; mud, snow, slick rock and large rocks (and pretty much any other terrain that can be found). I am not easy on Jeeps, I prefer difficult trails.
I say no issues with the axles (beause they perform well within their design limits and pretty well outside of the design limits) but if I drive stupidly, I can break the Ujoints at will, (the issue is clearly a matter of too much fun, inattention or poor driving). Never had a ring, pinion or spider gears fail. BTW, I have run crawl ratios on as low as 103:1 with very healthy engines and never managed to twist the axle splines as badly as shown in the pic (drive shafts are a different story).

In reference to the above pics;
Open Diff + large rocks ... If one tire is spinning in the air and dropped suddenly on a high traction rock/surface expect something to give (Not the axles fault).

Nothing is indestructable...

Enjoy!
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Last edited by Happy Joe; 12-18-2009 at 09:00 PM..
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