Have a broken wheel stud? Here is what I would do...

 Read a post about someone discovering a broken wheel stud on their RV. The wheel had been changed after there was a tire problem and the reported labor done at the tire shop is suspect.

In my experience studs bet broken from car crashes or over tightening of the lug nuts.

Here is a picture of the wheel with the broken stud at the 

8 Oclock position

    

From my 40 years Endurance Sports Car racing

 

and mounting hundreds of tires while doing evaluations as a tire design engineer, I STRONGLY recommend that all studs on that tire position be replaced and a HAND torque wrench be used to fully seat the studs unless a stud hydraulic press was used to install a full set of studs.

Also you should check all the studs at 50, 100 and EACH 50 miles thereafter till ALL the new studs have been confirmed to NOT need any additional turning of the torque wrench for two torque checks.

 I believe so strongly in the importance of lug nut torque I required our lug-nuts be torqued whenever we changed tires. In thousands of miles racing, including winning six consecutive 24 hour endurance races my cars NEVER lost a wheel due to broken stud or loose lug nut.

Lug nut Torque? Why is it important and why measure the force? Part 1

Here are some YouTube videos on the topic of Torque". What it is and how do we measure the force. As an engineer, I sometimes just assume that everyone understands some basic Engineering terms but I am wrong to make that assumption. You don't have to remember all the details. I am just hoping that when we are done with this topic you will accept our recommendations on how to set and how to check the torque of your lug nuts.

Important info. It is impossible for me to know the size lug nut or specification for every vehicle but you, the owner should know this important spec and it should be in your owner's manual. If you can't find it, find a dealer of your brand RV or check the on-line forums for other owners of your exact make and model and ask what the specs are. These numbers are critical for the safe operation of your vehicle. I can only talk in generalities in this blog.

One thing to remember is that for Class-C and Class-B RV motorhomes and for RV trailers as with your car or pick-up with 14" to 16" steel wheels, the torque spec is probably between 75 Ft-Lb and 85 Ft-Lb, while 19.5 tires run about 135-145  and 22.5 tires run 450-500 Ft-Lbs. So you folks with large wheels will have to depend on the service truck to tighten your lug nuts. It is possible to get a hand torque wrench with 1/2" drive sockets that will get you to the 150# to 200# range, but it is probably safer for you to leave the larger wheels and lug nuts for the service tech that has the proper tools. I will address the tools you need next week.

Here is a video that explains what torque is?
https://www.youtube.com/watch?v=kTwpA2yJ81o

Friction is the next topic.
https://www.youtube.com/watch?v=fN9b3ByRh7A

For proper torque of our lug nuts, the stud and nut need to be clean, rust-free, no damaged threads, and no oil lubrication unless specifically specified in your owner's manual. If you have had problems with a stud or nut, such as a nut coming off, or broken stud, or the wheel being partially loose or the threads have been cross threaded or the nut was significantly over-tightened, both the stud and nut should be replaced. Over-tightening can get the stud into the "yield" load range which can lead to incorrect tightening and even to stud failure.

This video shows why nuts come apart
https://youtu.be/Jq38Oe6lMEg
"Transverse vibration" is what happens with a wheel is fastened to a hub. This is why we need to check torque to be sure the assembly is retaining it's clamping load after we start driving.

Tensile strength is covered in THIS video.
https://www.youtube.com/watch?v=g_CdH3RJc04

HERE we learn about SHEAR
https://www.youtube.com/watch?v=i9SJbCCoACg

Ok, enough "Engineer speak". This stuff is what we engineers learn and use when designing joint and developing specifications for studs and lug nuts. There is no test in my blog on this topic, but if you are going to argue with an engineer, then you will need a solid understanding of these forces.

Now the next step is for you to do a little research
A. Find your owner's manual and look up the specifications for each of your vehicles.
B. Make a note of the torque spec and lug nut size where it is easy to find. A permanent marker on your door jam might be a convenient location.

Ok here is a short video on using s "Clicker" type torque wrench. 
 https://www.youtube.com/watch?v=DA4ug4gHccM
We will cover this tool and some others next week.

Stay Safe


You can check out this "entertaining" YouTube from a guy in Australia on How to Tighten "Nuts" - The Right Wayhttps://www.youtube.com/watch?v=VbN9Y_fUvjo

Truing tires. Is the tire properly mounted? Is the tire even to cause of vibration?

Had a question from "Fred" on "Truing Tires"
On a different subject, on the Escapee's forum, there was a conversation about tires, and someone mentioned truing new tires. IMO, truing of new tires today only covers up poor mounting procedure, vs 40-60 years ago when tire construction was not as advanced. What are your thoughts on this?

 First, let's be sure everyone knows what we are talking about.
The process of "Truing " a tire involves shaving part of the tread rubber off to make the mounted tire more round. HERE is a YouTube video showing the process.
I tend to agree with "Fred" that most out-of-round problems can be traced to a tire not being properly mounted and seated on the rim. It is also possible that the wheel itself may not have been properly mounted on the hub or it is even possible for the wheel itself to not be round.
 If you have a vibration problem you first need to ask "What has changed?" Did you just get new tires? Are the tires the same but the wheels were off the vehicle for something like a brake job? Have you been driving on especially rough roads with many large potholes? This is a "new to you" vehicle and you have no history with the tires and wheels on this vehicle. On some vehicles "Heat Set Flat-Spot" may be the cause. This happens when tires have been run, getting hot and you just stop and park the vehicle. Sometimes leaving the vehicle parked for weeks or months can also allow the tire to get a flat spot which could take a couple of hours running to work the flat spot out. High-Performance Passenger tires are more susceptible to this problem than large 22.5" size radials but even 22.5 tires can develop a flat spot.

The problem of vibration can usually be traced to either out of balance or the tire/wheel assembly being "Out-Of-round".
If you have vibration on a new tire, I would first confirm it was balanced. Next, I would measure the assembly on the vehicle and confirm it is in-tolerance. This usually means less than 0.030" radial runout goal with 0.125" the upper limit.
If you are exceeding the above, the next step would be to try and confirm which component is not "round". Ideally, you would confirm the wheel, with no tire mounted, was below the limit. If the wheel is "round" when measured on a mounting machine then we would need to confirm it is round when bolted to the hub. Some wheels are "Hub-Centric" and others are "Lug-Centric". Hub centric means the wheel centers on the ledge of the hub on the brake drum. Lug centric means it centers on the bolts holding the wheel to the hub. A lug-centric wheel can easily get "off-center" if one lug nut is fully tightened before the other lug nuts are snugged up. There are patterns for the sequence and steps of tightening lug nuts depending on the number of lug nuts. Here is the sequence as published by Chilton, a publisher of numerous automotive repair manuals.

 
 In addition to the above sequence, it is advisable to tighten the nuts in three steps of 1/3rd of the torque level. Example: if your torque spec was 90 Ft-Lbs you would first do all the nuts to 30 ft-lbs then again following the sequence tighten to 60 Ft-Lbs. The finally to the 90 Ft lb spec, again following the pattern
If the pattern and amount of torque are not followed it is easy to end up with a round tire & wheel assembly to be mounted off-center to the hub which results in an out of the round situation and unacceptable vibration.

Before I resorted to shaving a new tire I would measure the out of round. If you have confirmed all the above yet still have vibration on new tires, I would work with the tire dealer to confirm there is nothing in the individual tire that might contribute to some vibration by simply switching tires around or trying a different set of tires.
In all probability, by now you would have found and fixed the cause of the vibration.

Lug nut torque. A critical SAFETY item.

Those that have read their owner's manual, may recall seeing a mention of the need to check the lug nut torque. In this case, we are talking about how "tight" the nuts should be to ensure the wheels stay on our vehicles. Others may have a warning label on the inside of their RV. This is from my Class-C Coachmen.

Note: Class-A and RV with 10 bolt wheels probably require a service truck and torque in the 450 Ft Lb range, so this info may not apply to you as you will need significantly different tools.





Here is a video showing what can happen if lug nuts are over-tightened or are lose.

First the simple answer:
- Look up the specification in the Owner's Manual.

Here is a sample page from Heartland RV. Note they tell you how often to check and how tight to make the lug ut and even the pattern for the sequence of tightening the lug-nuts as seen here:



- With your torque wrench follow the instructions for both frequencies and how tight the lug nut should be.

- What to do if you don't know what a torque wrench is? Watch this video

- What to do if you don't own a torque wrench?
There are a bunch of videos that compare wrenches HERE   But you can get an OK wrench like THIS for $20  or a better quality one like this for $100.   You do not need to buy the most expensive wrench as hopefully you will be only using the wrench a couple times after a tire or wheel was changed on your RV. Or maybe a couple times a year per your Owner's Manual instruction  For infrequent use I have found Harbor Freight non-digital adequate. Just be sure to get a 1/2" as your lug nut torque spec is probably in the 75 to 130 Ft-Lb range. Don't get a wrench that is right at your spec as it will probably have a short life and may not be accurate at 100% of its rating.


Now some background:
Do not lubricate the stud or lug nut with oil. This can affect the torque reading and could lead to stripped threads in lug nuts ($) or broken wheel studs ($$$).

This web site gives a technical background on why not to lubricate lug nuts.


Some Technical Info for those that want to know more:

Torquing a bolt is to get a certain amount of stretch out of the bolt. If torquing a bolt to 80 Ft-Lib, it is technically more accurate to say "When you torque this bolt to 80 ft-lbs, it will cause it to stretch by .0030 inches". In critical applications such as race engines, many engine builders use certified bolts and actually measure the stretch of the bolts rather than using a torque wrench.

Think of the bolt like a spring. When you torque it, you're stretching it so that it exerts force on what you're holding together. This video goes deep into bolt stretch vs torque.

When I was driving my race car, confirming the torque of the lug nuts was MANDATORY before each track session. With this as a standard practice, I never had a wheel come lose in 30 years of racing.

##RVT906