MOPAR lock nuts are much heavier than stock nuts?! - Jeep Garage - Jeep Forum

Go Back   Jeep Garage - Jeep Forum > Jeep Platform Discussion > Grand Cherokee - WK2 - > Export Grand Cherokee 2011+

Reply
 
Thread Tools Display Modes
 
  #1  
Old 02-20-2015, 03:58 AM
WK2GC's Avatar
Member
My Jeep: 2014 3.0L WK2
 
Join Date: Jan 2014
Location: Australia
Posts: 18
Thanks: 1
Thanked 1 Time in 1 Post
Rep Power: 1260
WK2GC is on a distinguished road
MOPAR lock nuts are much heavier than stock nuts?!

Hi all, I posted this in wheels section but then I realised I was probably after more local Aussie advice. When I bought the genuine MOPAR lock nuts (part # 82212564) from the dealer they said I wouldn't need to balance the wheel afterwards.

When I weighed the nuts on the digital kitchen scales they were 77g vs stock nuts at 106g. I have the 20" standard Limited 5-spoke wheels - "polished aluminium with mineral grey pockets".

Surely this is a huge weight difference at high rotations and would cause vibrations. The dealer says they haven't had any issues, and in any case, there is no other lock nut. Then again, apparently very few people buy them (they had to order it in). I just can't understand from a physics point of view how it's a good idea to have such unbalanced weights at high rotational velocities. Surely it contributes to metal fatigue and vibration on the hub assembly/axle.

Has anyone had any experience? Thanks.
Attached Images
File Type: jpg 20 wheel.jpg (24.7 KB, 11 views)
File Type: jpg 82212564-b.jpg (83.3 KB, 13 views)
File Type: jpg IMG_9160.jpg (502.5 KB, 15 views)
File Type: jpg IMG_9161.jpg (469.3 KB, 15 views)

__________________
2014 Jeep Grand Cherokee Limited 3.0 CRD
Maximum Steel Metallic
Mods: Towbar, paint and interior protection.
Reply With Quote
Sponsored Links
Advertisement
 
  #2  
Old 02-20-2015, 04:53 AM
allypally's Avatar
Premium Member
My Jeep: 2012 3.0L WK2
 
Join Date: Aug 2011
Location: Wollongong, NSW
Posts: 2,418
Thanks: 51
Thanked 195 Times in 163 Posts
Rep Power: 71547
allypally has a reputation beyond reputeallypally has a reputation beyond reputeallypally has a reputation beyond reputeallypally has a reputation beyond reputeallypally has a reputation beyond reputeallypally has a reputation beyond reputeallypally has a reputation beyond reputeallypally has a reputation beyond reputeallypally has a reputation beyond reputeallypally has a reputation beyond reputeallypally has a reputation beyond repute
Re: MOPAR lock nuts are much heavier than stock nuts?!

Going back many years I had a Holden with a single locknut on each wheel. It really threw out the wheel out of balance. Only way to correct was to use one of those ancient wheel balancers where you lay the wheel flat and lifted it so it floated on a shaft. It had an 'eye bubble' in the centre. Had to the place the wheelnuts in place, then add the weights in order to get a balance.
__________________
MY12 Overland CRD
Cherry Red
Saddle Interior.
Front Recovery Hook.
Reply With Quote
  #3  
Old 02-20-2015, 12:05 PM
piratius's Avatar
Member
My Jeep: 2006 4.0L TJ
 
Join Date: Feb 2015
Location: Northern Virginia
Posts: 16
Thanks: 1
Thanked 2 Times in 2 Posts
Rep Power: 875
piratius is on a distinguished road
Re: MOPAR lock nuts are much heavier than stock nuts?!

This got a lot longer than I originally anticipated. Please bear with me!

The only problem with balancing the wheel specifically for a lugnut is that if you take the wheel & tire off, you have to reinstall them exactly the same way, or you'll be further compounding the problem.

Now, from a physics standpoint.

30g is just about 1oz (.0626lb), and I'm used to working in SAE/English. I'll try to convert wherever possible. Standard wheel weights (stick on) are about .25oz (7.5g)

If your jeep has 20" wheels, then normally the wheel weights are about 9" from the center of the hub (it's the radius, not the diameter). I'm assuming you've got a new(er) jeep with the 5x5" wheel bolt pattern, which means the lug nuts will only be 2.5" from the center of the hub (again, radius).

Now, I know I'm simplifying this, but putting 1oz of weight at 9" would have WAY more effect than putting 1oz (30g) at 2.5" - the weight moves faster at the edge of the tire, and has a much larger amount of force exerted on the wheel bearings and hubs. Conversely, 1oz (30g) at 2.5" will have less effect than 1oz at 9".

HOWEVER, like I said...with speed comes force, which is what throws off the balance. If we get into a little math (to be more precise), we find the following:

Circumference = 2*pi*r

For a standard wheel weight mounted 9" from the hub, the weight will travel 56.5"(4.7') every rotation. (2*3.14*9" = 56.5")

For the lug nut, it only moves 15.7" (1.3') every rotation (2*3.14*2.5" = 15.7")

In addition, I happen to know that a standard 33" truck tire rotates approximately 620 times per mile. At 60mph, that's 620RPM.

At a 9" diameter, a traditional wheel weight travels 56.5"/rev. At 620rev/min (rpm) that's 35,030in/min (2,919ft/min). KE = .5 * .0625lb * 2,919ft/min^2. KE=266,267lbft/min.

At a 2.5" diameter, the same weight travels 15.7"/rev. At 620rev/min (rpm) that's 9,734in/min (811ft/min). KE = .5 * .0625lb * 811ft/min^2.
KE=20,553lbft/min.

266,267ftlb/min divided by 20,553ftlb/min (266,267 / 20,553 = 12.96)

What you can draw from this is that a wheel weight imbalance in the traditional spot has almost 13x more effect on balance than a wheel weight imbalance at the lug nut. That 1oz (30g) difference in the lug nut is really going to feel like .08oz (2.3g) of traditional imbalance.

The first thing you should do is to install the new lug nuts on the front two tires, and see if there's an appreciable difference while driving at speed. I doubt you'll be able to feel it! If you can feel it, then you've got a couple of options:

1) Buy a strip of the sticky wheel weights, and put two or three (.5oz/15g or .75/22.5g) as close to the new lug nut as possible, directly in radial-line with it. However, every time you get your wheels re-balanced, the shop will pull these off, and you'll have to re-do it. Three weights would probably suffice, assuming you can get them really close to the lugnut. If you have to go halfway between the hub and the rim, do one or two. In addition, if you have someone else rotate the tires, they won't remember what's going on, and you'll feel out of balance because you've just compounded the problem.

2) Call a shop and explain your predicament to them. They'll try to help in whatever way possible (hopefully). They may tell you the same thing the dealership does!

I hope I helped, and wasn't too confusing!
-Brad
Reply With Quote
The Following User Says Thank You to piratius For This Useful Post:
Sponsored Links
Advertisement
 
  #4  
Old 02-20-2015, 04:44 PM
SNUKE's Avatar
Premium Member
My Jeep: 2014 3.0L WK2
 
Join Date: Jan 2013
Location: Sydney, Aus
Posts: 3,966
Thanks: 147
Thanked 584 Times in 453 Posts
Rep Power: 7658
SNUKE has a reputation beyond reputeSNUKE has a reputation beyond reputeSNUKE has a reputation beyond reputeSNUKE has a reputation beyond reputeSNUKE has a reputation beyond reputeSNUKE has a reputation beyond reputeSNUKE has a reputation beyond reputeSNUKE has a reputation beyond reputeSNUKE has a reputation beyond reputeSNUKE has a reputation beyond reputeSNUKE has a reputation beyond repute
Garage
Re: MOPAR lock nuts are much heavier than stock nuts?!

Alan your practical experience overrides any theoretical one, but I thinking exactly the same as Piratius.
I was thinking that having a 29g difference in mass close to the origin of the rotation would be really no different than switching from the plastic valve caps that come standard, to some metal Jeep logo ones that so many people do.

The other thing to check if you want to go stir crazy, is each other lug nut of equal weight. We all know the difference will not be 29g, but I would be surprised if they were all exactly the same.
__________________
I'm just want it for the "shorter headlamps".

MY14 GC Limited, 3.0 CRD, Lux II, Granite Crystal, 18" Wheels, Tubular Side Steps.
Could I get my avatar much larger?
Ordered: July 7 2013 Delivered Nov 25th
Reply With Quote
  #5  
Old 02-21-2015, 12:29 AM
WK2GC's Avatar
Member
My Jeep: 2014 3.0L WK2
 
Join Date: Jan 2014
Location: Australia
Posts: 18
Thanks: 1
Thanked 1 Time in 1 Post
Rep Power: 1260
WK2GC is on a distinguished road
Re: MOPAR lock nuts are much heavier than stock nuts?!

Hi Brad, that's an extremely detailed post. I really appreciate you going through the calculations. I'll take your advice and get the wheel weights.
__________________
2014 Jeep Grand Cherokee Limited 3.0 CRD
Maximum Steel Metallic
Mods: Towbar, paint and interior protection.
Reply With Quote
  #6  
Old 02-21-2015, 12:33 AM
piratius's Avatar
Member
My Jeep: 2006 4.0L TJ
 
Join Date: Feb 2015
Location: Northern Virginia
Posts: 16
Thanks: 1
Thanked 2 Times in 2 Posts
Rep Power: 875
piratius is on a distinguished road
Re: MOPAR lock nuts are much heavier than stock nuts?!

I think you missed the point. You probably won't be able to feel the imbalance caused by the wheel locks. If it's a MOPAR part you've bought at the dealership, specifically for your vehicle, they can't void the warranty for it either. Put them on the front, and see if you can even tell a difference. My 2 cents is that you won't be able to feel a difference.
__________________
2006 TJ Rubicon - 33's, Lifted, Softopper, Mile Marker Winch on a Ground Pounder Fab Bumper.

2007 XK Commander 5.7 Hemi - Stock, for now.
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
MOPAR lock nuts different weight to stock nuts WK2GC Suspension/Driveline/Brakes/Wheels/Tires 5 02-20-2015 06:53 PM
Much happier with the reliability and build of my 2014 than I was my 2011 SW03ES Grand Cherokee - WK2 - 11 11-03-2014 01:49 PM
How much lower and stiffer are SRT springs than Limited? notalk Grand Cherokee SRT - WK2 0 03-06-2013 07:18 PM
4 wheel low lock-out (or lock-in)??? kinerin Trouble Shooting/Problems/Service 3 02-07-2013 12:13 PM
Lock unlock settings? Auto lock after exit? cyanideg Grand Cherokee - WK2 - 1 09-20-2011 11:51 AM

» Premium Vendor Showcase
Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 03:44 AM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Copyright 2012 - JeepGarage.Org
The Jeep Grand Cherokee Owners Community

JeepGarage.org is in no way associated with or endorsed by FCA US LLC. Chrysler, Dodge, Jeep, Ram, Mopar and SRT are registered trademarks of FCA US LLC.