rx7m5guy

I autocross my daily driver C6 ZO6. When I change to the R tires at the event, I also change the camber, (and toe), by removing shims behind the upper A-arm attachment points. To facilitate that and to avoid wearing out the threads in the the frame, I changed out the factory bolts to stainless steel studs. The stainless steel is nice for corrosion resistance, but I am having problems with it galling with the stainless steel nyloc nuts that came with the kit which I have replaced with standard SS nuts which still seem subject to galling.

Maybe I am unaware of a technique that doesn't damage the SS, or maybe this is inherent with repeated use of SS threaded fasteners. Does anybody have any experience or expert suggestions on how to deal with this?

I am looking for a plain steel option and have searched the web for off the shelf studs in the required size, so far unsuccessfully. Does anybody have a source?

Or will plain steel nuts used with the SS studs solve the problem? The SS threads almost seem soft and easily deflected and/or torn from the stud. I did use a light duty impact driver on them only for the initial tightening, but refrain from using it now with no noticeable change in the galling.

If a materials engineer can comment, there is also reactivity to consider between the dissimilar metals at the stud contact point with the frame. I have Locktite in those threads. I think I saw a chart that SS to AL is ok. The factory bolts look to be galvanized steel.

TIA

Cheers, Philip

Solofast

Stainless isn't that strong, and it is known for having galling problems, with stainless on stainless, so it's no surprise that this is happening. Just be thankful you aren't using titanium on stainless, it's even worse.

In addition, the threads are being pushed on by the control arms when you are in the "street" mode and then, when you take the shims out you are winding the nuts down past the distorted threads and this is part of the problem.

I wouldn't be using stainless for these studs at all, get a good high strength steel stud, or get a long enough bolt and cut it off and thread the end to make your own studs.

There shouldn't be any threads where the ears of the control arm bushing are in contact with your studs. This means that you should take the shims out of one side of the stack and put them back in on the other. There shouldn't be any time that your stack is without shims. This will allow you to have an unthreaded section of the stud between the chassis and the nut that won't get beat up in moving the control arm back and forth.

travisnd

I got the stud kit from Gary at Hardbar. My car is track only so I don't take the upper A-arm loose very often, but the times that I have I haven't had any galling issues. His kit comes with Nordlocks to keep the nut secure. I'm not sure what material the stud is vs. the nut.




EDIT: The website says the following:

However the nuts with mine are not Nylocs and I have Nordlocks to keep everything tight. One some of the studs I did have to use a stack of washers so the nut wouldn't reach the end of the threaded pert of the stud when tightening.

rx7m5guy

Thanks Solofast, your advice confirms my experience and the direction I was headed to plain steel.

The SS studs I use have a 3/4" unthreaded center, but I never thought of ensuring the nut seats in the same place by putting the shims on the other side of the bushing ear. Generally, I may do that hit or miss only for the convenience of having a place to store the shims and to ensure the nut doesn't get run down onto the unthreaded portion of the stud. I will make a point of doing that in the future.

Philip

rx7m5guy

Thanks travisnd, I have the same kit front and rear acquired from Hardbar about three years ago. I want to be careful to not disparage Hardbar's part as it is very nicely done as your picture shows. I think I may have been too hard on them, particularly with the impact possibly distorting the threads.

Cheers, Philip

AzMotorhead

I agree with Solofast.
Stainless to Aluminum is one of the worst combinations for galvanic corrosion. Granted if it doesn't get wet there will be very little conductivity between the 2.
I'd be looking for a grade 5 bolt or stud to use in that application.

I say use a grade 5 because of what I was told years ago by a Mfg of hi performance A arms. Say you hit a wall, you'd want the fastener to give out before destroying a more expensive part.
Just a quick search yielded Fastener info
And
Stainless steel can unpredictably sustain galling (cold welding). Stainless steel self-generates an oxide surface film for corrosion protection. During fastener tightening, as pressure builds between the contacting and sliding, thread surfaces, protective oxides are broken, possibly wiped off, and interface metal high points shear or lock together. This cumulative clogging-shearing-locking action causes increasing adhesion. In the extreme, galling leads to seizing - the actual freezing together of the threads. If tightening is continued, the fastener can be twisted off or its threads ripped out.


If galling is occurring than because of high friction the torque will not be converted into bolt preload. This may be the cause of the problems that you are experiencing. The change may be due to the surface roughness changing on the threads or other similar minor change. To overcome the problem - suggestions are:


1. Slowing down the installation RPM speed may possibly solve or reduce the frequency of the problem. As the installation RPM increases, the heat generated during tightening increases. As the heat increases, so does the tendency for the occurrence of thread galling.


2. Lubricating the internal and/or external threads frequently can eliminate thread galling. The lubricants usually contain substantial amounts of molybdenum disulfide (moly). Some extreme pressure waxes can also be effective. Be careful however, if you use the stainless steel fasteners in food related applications some lubricants may be unacceptable. Lubricants can be applied at the point of assembly or pre-applied as a batch process similar to plating. Several chemical companies, such as Moly-Kote, offer anti-galling lubricants.

Solofast

You didn't say those were 17-4 stainless studs. That's a whole other thing. I was thinking you had 304 studs.

Gary's 17-4 studs are plenty strong and are very good stuff. 17-4 is a very good material, not at all soft like 304.

I'd look at the nuts you are using and make sure that they are a good quality nut. I wouldn't use stainless nylocks here just to not have stainless on stainless, but a steel nut should be more than fine on those studs.

You could go with a dab of molykote to keep them from galling too.

I wouldn't change the studs unless you have damaged them. Better to do the shim bit and keep the nuts in the same spot, and you should be fine with a good nut.

rx7m5guy

Thanks AzMotorhead for more great info. The galling description exactly describes what my studs look like. I had never run across an explanation before nor looked for it on web so thanks again for the enlightenment. I had only searched for plain steel stud suppliers and hoped somebody else had already figured out where to get them.

The factory bolt is metric and has 10.9 embossed on it.

Cheers, Philip

travisnd

I never run mine on with an impact... I thread them on by hand then use a regular socket/extension. I torque them to 30 ft/lbs with the nordlocks.

rx7m5guy

Replying to Solofast, that is "17-4" not "7-18" or did you edit it? I have it both ways on here.
Regardless 17-4 PH has greater tensile strength spec's than the 10.9 factory bolt. I wouldn't have expected any less from Hardbar as Gary seems to be a very competent engineer. I don't remember from 3 years ago that Hardbar specified then that their studs were 17-4 PH, but that may be my memory.

The nylocks I used were furnished with his kit. I speculate that the drag they induced thread against thread as they were spun on fast by my impact driver may have produced heat that broke down the iron oxide layer and contributed to the cold welding/galling.

I am not opposed to continuing using the SS studs now knowing that a lubricant, plain steel nuts and slow rotation will oliviate the galling.

I appreciate your aviation manufacturing backgorund. I have an AAE education from the U of IL but never got to work in the industry.

Cheers, Philip

ErnieN85

When I got mine from Gary he sent along a second set of nuts along with instructions not to use the original stainless nuts as they would gall. I don't remember exactly so its best to call him although I do believe that the replacements were regular steel aircraft nuts

rx7m5guy

Thanks Ernie, that's interesting. I think I ordered it soon after Gary presented it on this forum, so I may have got my kit before the issue was recognized, because my kit didn't have the extra nuts or a note. I did email him at the time describing the problem with surprisingly no response, but then you never know if an email gets through. I never followed up and went onto having an aggressive street setting that I used for autocross also, but now I want to go back to making the change to an autocross alignment at every event.

I will try to contact them again if I don't find a plain steel alternative. Hardbar's studs look to be specially engineered and custom machined for proper length and unthreaded area for the Corvette suspension application.

Cheers, Philip

trackboss

I have the hardbar studs as well. Years ago, when I installed them, I had a problem and thought they were galling, but discovered otherwise. The problem was that the unthreaded shank portion was longer than the pfadt a arm shafts were thick. The nut was bottomming out on the shank before everything was tight enough. When using less than 3 washers (can't remember the exact amount) between the shaft and the frame the shank was exposed.
I now always put a stack of washers under the nut to make sure it doesn't come into contact with the shank. I also use plated steel nuts instead of what came with the kit in addition to anti-seize and safety wire.
Lastly, I have the long studs in my car and they are too long. The ones located at the forward most and rearward most position ended up destroying my front street tires (never turned the wheel that much on track). I have since cut them down.

rx7m5guy

Thanks Trackboss, you jogged my memory that the same thing happened to me when I went to tighten the first stud, particularly having removed washers from behind the ear to get more camber. I used washers under the nut after that. Any damage caused to the stud or nut from that wasn't as evident as the galling. It may have deformed the threads enough to cause additional drag between the threads when spinning the nut on that generated heat which according to AzMotorhead's info contributes to galling.

Thanks to all you guys for the info and comments, it has helped me out. If I find any plain steel studs, I will post the info.

Cheers, Philip

fatbillybob

First I'm not an engineer. Oem bolts are 10.9 that is a fact. 17-4 stainless and oem 10.9 bolts are very close in ultimate strength so why not just use easy to find 10.9 studs and mate them with 10.9 nuts you can source anywhere? When the studs and nuts are of the same material galling is reduced. Stainless, even 17-4, galls. Galling is a problem with SS everyone knows this. You can reduce galling by using some antiseize but then you need to deal with the change in torque spec and if that is appropriote. Second you can reduce galling by making sure the threads are clean. moving shims/washers on and off studs that have been clampped down cause small shards of metal to be trapped between thread surfaces causing galling. Third do not use an impact wrench. Heat into stainless increases galling and the heat spikes when shards of metal are embedded in the threads. I really see no advantage to using studs. I would use the oem 10.9 bolts and shims to change between street and track before I used studs and washers. There does not seem to be a stud advantage and the studs and washers I bet are heavier too.
The one poster who cut down his tire on the stud would never have happened with OEM bolts.

travisnd

I much prefer my studs to threading the bolts into the frame. You booger up the frame hole and you have to break out the tap/die kit. If you screw it up enough you're going to have to drill it out bigger and start over etc.

I'm not sure how a poster cut a tire on his... must have been running really large tires as mine never come close.

fatbillybob

I get what you are saying. You need to be careful when you pull the bolts all the way out which is never if you shim vs washer. Shims for alignment have been used in very similar circumstances for decades. No reason shim will not work here. Back off bolts 2 turns and slide in/out a shim no chance of damaging chassis thread unless one is very ham-fisted. More likely you will spend hours taking your suspension apart to get a die grinder in there to cut the SS stud and nut when it galls up solid and cold welds itself. In the meantime before ultimate failure you will have torque problems because of the galling process. Loosing that A-arm or wobbling A-arm in the braking zone at 150mph next to the wall on T3 at ACS does not sound fun.

travisnd

I've been using Gary's studs for nearly 2 years now. Never any issues with galling. Mine doesn't have nyloc nuts. It uses a regular steel nut and a nordlock to keep it from ever backing off.

Taking the upper A-arm loose makes messing with the shock or spring much easier. I think OP's first mistake was running these on with an impact. Who knows how tight he was making them?

Solofast

fatbillybob is right. I hadn't thought of it either way, but if you are just going to back out whatever is doing the clamping and swap the shims from one side or the other it doesn't make much difference if you are using longer bolts or studs, so fatbillybob has a good point. You can probably use longer bolts just as effectively as studs.

I do still like the idea of studs since you won't wear out the threads in the the frame (which I agree is pretty unlikely), and if you booger a thread you can replace the stud and be done with it. The thing that terrifies me every time I change shocks is that I will cross thread one of those frame nuts. I'm really really careful to make sure I don't, but if you do you are really hosed.

Pluses and minuses with either way. I thing the biggest thing is to make sure that you just flip the shims from one side of the dogbone to the other no matter which way you do it so you don't have much risk of messing up the threads.

froggy47

I agree, never gun those on. Probably had damage from the start. I use the studs (Pfadt) with nylocs & no issues.

If I were flipping the adj a lot, I'd put a dab of anti seize on the save the threads. Like I do my rims.

I only touch those when I do an alignment a couple times a year so I don't need it on those threads, but lugs & nuts I do.

Let's not go off on a tangent about the torque spec here as that is beat to death on other threads.