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Old 23rd October 2009, 08:12   #1
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Default Alloy wheels and stud threads

A vexing problem arose a few days back. After an afternoon of off roading through Aravalli hills full of thorn scrub parked the car for night.

Woke up to find rear right flat. So the car was jacked up and there arose a problem:


Can you spot it? A closer look at the problem


The problem was two wheel nuts that refused to come off. After initial unscrewing they became tight. Although I guessed the cause, and effect which was result of this. I still needed to take these out. So continued rotating the wheel spanner anti-clockwise. This also involved putting pressure by foot - like truckers do. Ultimately the nuts came off. And I also took out the studs.

The effect:




What do you think is the cause?
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Old 23rd October 2009, 08:46   #2
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It is definitely due the nuts were not fitted properly .They were fitted cross threaded.
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Old 23rd October 2009, 12:37   #3
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Nope that is not the reason. If it was one can expect one and not two out of five to be done in a dumb fashion.

Quote:
Originally Posted by tsk1979
Thread failure can happen if during tightning, the bolt is put on slightly sideways, and then force is applied. Many tire shops use pneumatic wrenches, so even if the bolt is put wrong, it will go in, devastating the thread
Again same logic...one yes but two? And see picture of the bolt that has not yet gone bad.

Last edited by Dippy : 24th October 2009 at 09:40. Reason: Back to back posts
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Old 23rd October 2009, 12:46   #4
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Quote:
Originally Posted by sudev View Post
And see picture of the bolt that has not yet gone bad.
Its already in the process of going bad

is it the affect of extreme pressure on wheel hub, may be you passed on stone pretty fast or affect or Off Roading, just guessing

I think it will be wise to open the other tires and see the condition.
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Old 23rd October 2009, 13:03   #5
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Could also be due to overtightning, the bolt has a head, its not the normal hollow bolt but one end is closed.
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Old 23rd October 2009, 13:07   #6
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@rkabharat: Yes pressure on thread due to wear is showing but the reason is not off roading.

Any more guess?
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Old 23rd October 2009, 13:20   #7
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its definitely a case of cross thread there is no way that the pressure is only on two bolts. If that was the case all the bolts would be in same condition. Also overheating will also been on all the 5 bolts. Its definitely a case of wrong bolt fitting. Another case may be that your rims may not be hub centric in case of aftermarket rims.
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Old 23rd October 2009, 13:41   #8
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Okay - Here is the theory.

Alloy rims have very high compressive strength. Much more than steel rims. And they do not have any springiness which steel rims do.

When you tighten the nuts beyond the recommended torque settings the nut is not able to travel down wards since alloy rim surface does not "bend". The resultant force simply gets transferred to the threads of the nuts and bolts. Till beyond the critical limit the threads fail. More so when you try to finish off tightening with the last pull or "jhatka"

In case of steel rims there is bit of springiness in the steel that actually helps is preventing such damage to some extent. Similar to alloy rims are cast rims used in heavy vehicles. However there the thread is of bigger pitch which can take more force.

Unfortunately last time around I had sent my driver to get the puncture fixed and wheel put back. This resulted in the tyre shop guy using his "might" and long levered wheel spanner to tighten the nuts. The end result is for us to see.

So CAUTION for all users of alloy wheels. Do not over tighten wheel nuts. Use torque wrench if possible. And it is recommended to use spring washers to prevent nuts from opening up with vibrations (or use "nylock" nuts).
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Old 23rd October 2009, 13:59   #9
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Defintely a good informaton to know, and to keep it in mind whilst dealing with
alloy wheels.
Thanks
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Old 23rd October 2009, 23:02   #10
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Torque wrenches are a must when dealing with alloys. The problem is that most dealerships/shops like to use pneumatic guns to loosen and tighten nuts and hence the overtightning. Worst is the truck culture where the guys stand on the spanner to ensure that the nut is adequately tightened.
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Old 28th October 2009, 15:46   #11
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I dont think the nuts that you are using are original nuts .

Most of the marutis dont sport nuts with dust caps on them .
Another thing i noticed was the nuts are conical on the tghtening end and the alloy has a flat surface where the nut should have been screwed in place . My reasoning is that the nuts were actually not tightened properly and the wheel was having a play btwn the bolts
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Old 28th October 2009, 19:27   #12
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The nuts are OE supply with GV. The tightening was adequate and no play was there this was confirmed by the initial force I had to apply when opening the nuts.
If you see the conical portion half of it is shining showing good contact.
SX4 and Swift VXI have similar nuts.
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Old 28th October 2009, 21:02   #13
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Quote:
Originally Posted by sudev View Post
The nuts are OE supply with GV. The tightening was adequate and no play was there this was confirmed by the initial force I had to apply when opening the nuts.
If you see the conical portion half of it is shining showing good contact.
SX4 and Swift VXI have similar nuts.

yes , but the wheel seems to have a flat profile for fastening the nut and not a conical profile . I may be wrong on that count as well
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Old 28th October 2009, 21:06   #14
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looks like nuts were note placed properly and forced into position.
let it be alloys or rims the above can do a lot of damage.
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Old 28th October 2009, 23:31   #15
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Interesting theory about the nuts, but, knowing the compressive strength of steel, it would really require a LOT of force to cause the studs that much damage. Let us not forget that the studs themselves are made of good quality iron which has a good compressive strength. Maybe cross threading could be a more probable reason seeing the way some threads have worn out.

Last edited by neel385 : 28th October 2009 at 23:33.
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