Rotor/hub issue

ISAslot

Platinum Member
Jan 22, 2001
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The 68 Ford front disc is suppose to be a pain due its uniqueness for that year. However, it's supposed to be a separate hub and rotor. However looking at my rotor/hub... I don't know if the wrong ones were on it, or if these are pressed together somehow. If pressed, I don't know how to get them apart... any ideas?

http://imgur.com/a/sJExX
 

DrDoug

Diamond Member
Jan 16, 2014
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You need to press out the studs to separate the hub from the rotor hat. If you don't have a press you can do the job with a BFH (big 'freakin' hammer). First, buy some new studs and nuts. Then thread the old nuts most of the way back on to the studs and use the BFH to hammer on the nut and drive each stud out. Then clean your hub (install new races if you are replacing the bearings), maybe toss a spray of high temp paint on it to inhibit rust and make it look nice. Get some green Loctite, position the new rotor and your clean hub, insert the new studs with a bit of Loctite on the knurling of each one, then use a drift and the BFH to drive each stud (from the rear) a bit through the rotor hat and into the hub to get everything centered. Once it looks good (positioning-wise), drive each stud home.

Use a BFH, five pounder minimum, to get the job done right. No wimpy hitting either when driving the studs home, nail it like you are Thor. Some guys use a deep socket and large C clamp but that takes too long for me.

Or take it to a machine shop and they will whip it out for you in no time for a minimum charge. :biggrin:
 

JCH13

Diamond Member
Sep 14, 2010
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Why are you recommending OP hammer in the studs and use loctite?

I would suggest using lug nuts and a pair of plain washers (with a little oil) to draw the stud into place. Hammering the stud seems like a good way to deform or crack it. At the very least OP could easily wind up hammering it in off-normal and make a royal mess of things. Using a lug nut to draw the stud in has none of these issues.

Loctite in a brake component or hub will tend to simply melt away from brake heat, making it utterly pointless to install in the first place.

I do agree with using a hammer to knock the old studs out, but I wouldn't use a lug nut to do so (risk of damaging the lug nut, specifically its threads). Just hammer the stud out.
 

boomerang

Lifer
Jun 19, 2000
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I don't think I'd hammer out studs on a 46 year old brake rotor/hub assembly unless I knew for certain I could purchase the hub separately. I'd soak it repeatedly for days with PB Blaster or an equivalent product and then press them out while supporting the underside of the rotor hat surrounding the stud I was pressing out. Breaking the hub when no replacement is available could result in a huge disappointment.

I've hammered out lugs many times before. It's the age and potential unavailability of the parts that makes me leery in this case. I'm going to add that the hub is probably a light press fit in the rotor so removing the lugs may not complete the job.

An additional thought is that it would probably be a good idea to turn that rotor after assembling the rotor, hub and studs. Having clean mating surfaces and having all parts fully seated would be important before the machining operation.
 
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slag

Lifer
Dec 14, 2000
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Doesn't everyone in this forum have at least a harbor freight 20 ton press?

GAH, newbies!!!! :)
 

JCH13

Diamond Member
Sep 14, 2010
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I don't think I'd hammer out studs on a 46 year old brake rotor/hub assembly unless I knew for certain I could purchase the hub separately. I'd soak it repeatedly for days with PB Blaster or an equivalent product and then press them out while supporting the underside of the rotor hat surrounding the stud I was pressing out. Breaking the hub when no replacement is available could result in a huge disappointment.

I've hammered out lugs many times before. It's the age and potential unavailability of the parts that makes me leery in this case. I'm going to add that the hub is probably a light press fit in the rotor so removing the lugs may not complete the job.

An additional thought is that it would probably be a good idea to turn that rotor after assembling the rotor, hub and studs. Having clean mating surfaces and having all parts fully seated would be important before the machining operation.

Good point.

PB Blaster is garbage (IMO). I'd go for a superior product, like Kroil (expensive) or ATF+Acetone (cheap). Both are WAY better than PB blaster.
 

boomerang

Lifer
Jun 19, 2000
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Good point.

PB Blaster is garbage (IMO). I'd go for a superior product, like Kroil (expensive) or ATF+Acetone (cheap). Both are WAY better than PB blaster.
Yeah, I pretty much quit doing mechanical work a decade or so back and am not up on the bestest products anymore. :)
 

DrDoug

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Jan 16, 2014
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Hammering studs in place is a breeze if you have a proper sized brass drift and a BFH, I've seen experienced mechanics (old mechanic here) do it for years and never have a problem. Knock out the old studs, clean up the parts, dab a tiny bit of Loctite on the knurling of the new studs and properly drive them home (two-three solid blows with the BFH at most, anything less and you could damage them). If you damage the studs with this installation method then you didn't do it right. Hell, all four of my hubs on my Mustang had them installed this way over twenty years ago and you wouldn't know I didn't use a press. Good suggesting the PB (or Kroil) though, that will help with really badly rusted parts. A torch and wax will do the trick too.

Regarding putting the old nut on the stud, you do that to give a nice flat surface to hammer against when knocking the studs out. One or two blows, take the nut off and pull the stud out. Done. Spend some time with some old mechanics and learn the alternatives for getting a job done right. Old style out of the box thinking was needed by a lot of these guys and they've been there and done that.

My last sentence was the best recommendation (thus the big grin), take it to a machine shop and let them do it for you.

ETA: Regarding Loctite, you are aware that there are high temp versions of Loctite, right? If your studs are getting to be over 450 degrees F you've got bigger problems than that Loctite.
 
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JCH13

Diamond Member
Sep 14, 2010
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Hammering studs in place is a breeze if you have a proper sized brass drift and a BFH, I've seen experienced mechanics (old mechanic here) do it for years and never have a problem. Knock out the old studs, clean up the parts, dab a tiny bit of Loctite on the knurling of the new studs and properly drive them home (two-three solid blows with the BFH at most, anything less and you could damage them). If you damage the studs with this installation method then you didn't do it right. Hell, all four of my hubs on my Mustang had them installed this way over twenty years ago and you wouldn't know I didn't use a press. Good suggesting the PB (or Kroil) though, that will help with really badly rusted parts. A torch and wax will do the trick too.

Regarding putting the old nut on the stud, you do that to give a nice flat surface to hammer against when knocking the studs out. One or two blows, take the nut off and pull the stud out. Done. Spend some time with some old mechanics and learn the alternatives for getting a job done right. Old style out of the box thinking was needed by a lot of these guys and they've been there and done that.

My last sentence was the best recommendation (thus the big grin), take it to a machine shop and let them do it for you.

It's funny how you talked about the same things that I did without actually addressing any of the concerns I raised. :p

I have a brass drift, and a copper one too, and a large hammer (several, in fact), and a press. But I see no need to use any of these tools when installing a new stud. Drawing the stud in with a lug nut completes the same action as the above tools, with minimal risk that the stud will go in at an angle or otherwise become damaged. It can also be done on the car.

I've seen plenty of studs removed without hammering on the lug nut (see youtube if you don't believe me). It just seems totally unnecessary to risk damaging a lug nut in that situation, so why should I use one?

Same with loctite: it is unnecessary. It is just going to melt out the first time someone gets on the brakes down a modest hill. Why should I use it in the first place?

Edit: I see your edit. I am completely aware of high-temperature loctites. If you can prove that rotors will never get above 450F, or that studs never reach that temperature, I'm all ears. Why would I be in trouble if the base of a brake rotor got to 450F?
 
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DrDoug

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It's funny how you talked about the same things that I did without actually addressing any of the concerns I raised. :p

I have a brass drift, and a copper one too, and a large hammer (several, in fact), and a press. But I see no need to use any of these tools when installing a new stud. Drawing the stud in with a lug nut completes the same action as the above tools, with minimal risk that the stud will go in at an angle or otherwise become damaged. It can also be done on the car.

I've seen plenty of studs removed without hammering on the lug nut (see youtube if you don't believe me). It just seems totally unnecessary to risk damaging a lug nut in that situation, so why should I use one?

Same with loctite: it is unnecessary. It is just going to melt out the first time someone gets on the brakes down a modest hill. Why should I use it in the first place?

Edit: I see your edit. I am completely aware of high-temperature loctites. If you can prove that rotors will never get above 450F, or that studs never reach that temperature, I'm all ears. Why would I be in trouble if the base of a brake rotor got to 450F?

Drawing the stud in is doing so by pulling it through, which can apply more tension (stretch) than it experiences while holding a wheel in place. Sure, people do install them that way and if you want to start your new studs out that way then please, be my guest. I'll use compression to install them. Regarding installing a stud at an angle, you haven't done many studs have you? Regarding damaging a stud when installing it, really? With a brass drift? Please. I've installed too many studs to count and I've never damaged one. Never. I worked as a mechanic in a Porsche/Audi dealership and if the press was tied up, guess how we installed studs? Yeah.

Every time I change out the studs I change out the lug nuts too, thus I use the old lug nuts to uninstall the old studs and then throw them both away afterward. Do you reuse old lug nuts on a new stud? Well good for you! I don't and nor do good shops.

You do know that that same Loctite is used as the sole way to hold some bearings in place, right? Same with sleeving a cylinder in a block, it's used right where the heat of combustion passes through it to the remaining cylinder wall. That's more thermal abuse than a lug nut is going to endure.

And finally, if that Loctite did fail and if your studs fell off or worked loose, you used the wrong studs or you left the lug nuts loose...lol
 

JCH13

Diamond Member
Sep 14, 2010
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Drawing the stud in is doing so by pulling it through, which can apply more tension (stretch) than it experiences while holding a wheel in place. Sure, people do install them that way and if you want to start your new studs out that way then please, be my guest. I'll use compression to install them. Regarding installing a stud at an angle, you haven't done many studs have you? Regarding damaging a stud when installing it, really? With a brass drift? Please. I've installed too many studs to count and I've never damaged one. Never. I worked as a mechanic in a Porsche/Audi dealership and if the press was tied up, guess how we installed studs? Yeah.

Every time I change out the studs I change out the lug nuts too, thus I use the old lug nuts to uninstall the old studs and then throw them both away afterward. Do you reuse old lug nuts on a new stud? Well good for you! I don't and nor do good shops.

You do know that that same Loctite is used as the sole way to hold some bearings in place, right? Same with sleeving a cylinder in a block, it's used right where the heat of combustion passes through it to the remaining cylinder wall. That's more thermal abuse than a lug nut is going to endure.

And finally, if that Loctite did fail and if your studs fell off or worked loose, you used the wrong studs or you left the lug nuts loose...lol

*sigh* I don't know why I expected calm and reasonable answers. I was trying to learn the reasoning behind your practices by explaining how I saw things and asking why you choose to do what you do. This is why us young guys don't like seeking advice from you old mechanics: we're met with sarcasm and personal insults when we ask 'why' instead of just blindly accepting what someone on the internet says.
 

DrDoug

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Jan 16, 2014
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What wasn't calm and reasonable about that? I gave you a point by point answer as to why I do things they way I do and why not to do them the way you stated. OK, I loled at the end, sorry but I couldn't help that one. Really. Blue Loctite is recommended and has been used for years on lug nut threads for extra security. Green Loctite (620) is recommended for wheel studs and not only secures the studs but also acts as a lubricant during assembly.

I would not recommend using washers to draw a new stud into place unless you are stuck on the road and have no choice. If so, I would change that stud out asap. Have you ever noticed where a wheel lug snaps? Usually at it's weakest point, right at the base of the threads. The amount of force necessary to seat a stud (even with a lubricant) by pulling it through would more than likely push a stud past its elastic point and permanently deform/weaken it. If you also think about it, using the threads on the stud/nut interface in a way that they weren't designed to be used would not be a very good idea.

I usually don't give advice on general forums, unlike my membership at a motorcycle and car forum where I am well known and freely give advice. Too many times people rush in with criticism about this or that detail and I just don't have the time to deal with it. Sometimes I feel bad for not speaking up when I read that things didn't turn out well for the person that followed the advice given. So sometimes I toss out some help when I can but usually it ends up the same way as I described above. I have been turning wrenches for over thirty years and have seen and done just about everything you can do in a vehicle. I also am a electrician (marine) and used to design electrical systems for a boat manufacturer. I have worked on everything; exotic cars, big & little trucks, big & little boats, yachts, schooners, RVs, motorcycles, ATVs and just about anything else that is electrical/powertrain based. I have rebuilt starters, alternators, distributors, engines, transmissions (auto & manual), transfer cases, differentials, outdrives, V-drives and so on. I was ASE certified in multiple fields and a certified Volvo-Penta, MerCruiser and OMC mechanic. I am now in computers because of RA but still turn wrenches on my cars. I finished rebuilding the C4 trans in my Mustang about two weeks ago and am now enjoying driving that car again. I beefed it up with Alto Red clutches, Kolene steels, kevlar bands, TCI "H" code servo, TransGo -2 shift kit and a mildly higher stall converter for service behind a mild 400 HP 351W, so I'm not dead yet. :biggrin:

Lets just say I have done lots of stuff...lol! Now I was nice and left out the fact that the studs and rotor/hub are connected to a huge heatsink (a wheel) and if those studs were hitting 450 degrees, guess how hot the wheel would be? ;)

Peace. :)
 

JCH13

Diamond Member
Sep 14, 2010
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What wasn't reasonable was how condescending and smarmy you were throughout your post. You talk as if anyone without your level of experience, or who disagrees with you, is an idiot. It makes taking any advice you supply difficult. There's no reason to be so negative towards someone who is actively seeking your opinion as part of a discussion.
 

ISAslot

Platinum Member
Jan 22, 2001
2,879
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Just ordered some new studs/nuts and threw in some new bearings and races too.
Will post back this weekend when I attempt to remove the old ones. Thanks for all the info.
 

BUTCH1

Lifer
Jul 15, 2000
20,433
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Is that a chunk of hub missing or is it designed like that? IDK as I haven't worked on a 60's car since the '70's. If in fact that is a chunk that broke off I would doubt the integrity of that hub and replace it, if I'm wrong I apologize in advance.
 

DrDoug

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Just ordered some new studs/nuts and threw in some new bearings and races too.
Will post back this weekend when I attempt to remove the old ones. Thanks for all the info.

Good deal! In the meantime get that hub cleaned up (inside and out) and remove as much rust as you can while you are at it. Leave the races in for now though to protect the mating surfaces from surface rusting while waiting for the new bearings/races. To start, use a large screwdriver to pry out the old seal. When you do go to drive the old races out, if you look into the hub and at the back side of the race furthest from you, you should see a couple of notches where you can use a steel drift (I also use a big old flat-bladed screwdriver missing its handle for the tight spaces) to catch the edge on the back side of the race to drive it out. Drive the race out by going from one side to the other in a rocking fashion so as to not cock the race in the bore. Once the race is partially out you can work the steel drift/old screwdriver around the backside until the race drops. As the race is driven out, be careful not to mar the mating surface of the hub where the race goes! One trick is to use a bench grinder to cut a notch into the end of the steel drift (or old screwdriver) so that it catches the inside lip of the race and stays there.

Usually there is enough room that you can drive the rear race out without having to space the rotor/hub off of your work surface but the outer face of the rotor/hub needs to be supported so that there is room to drive the outer race out. I have a big ol' piece of pipe at home that I set the rotor/hub on to give it enough room. You can use anything you can come up with to give that space but be sure that your work place is solid and does not flex (no bouncing parts!) so your hammer blows impart all of their force into removing the race.

Once the races are out, clean the hub center out well enough that you could eat dinner out of it. Really, cleanliness is next to Godliness when it comes to this kind of work. The smallest particle can hang a race during installation and make your life miserable. Lightly oil the hub bore that you are going to install the first race to, same with the outside of the race. Use a brass hammer (2 Lb. minimum) to start the new race into the bore. Work from side to side (the race will want to cock into the bore initially) until the race is in about half way in place. At this point I switch to the BFH and a small 1/2 inch thick piece of aluminum plate and work around the race until it is flush with the face of the hub bore. While I use the BFH here you don't need to be Thor to drive it in. At this point I then use the cleaned up old race (flipped over so the wider part of the taper is facing outward to drive against) to drive the new race in the rest of the way. As you are driving the race in the hammer blows will sound 'dull' but once the race is seated the sound will change to more of a ringing sound. Once you reach that point take a look at the inner hub shoulder (small shop mirror or wife's old cosmetic mirrors are great for this) to verify that the race is solidly seated against the shoulder of the hub bore.

Once the first race is in, clean the inside of the hub again and repeat the process for the second race. When you are using the old race to seat the race into the bore there may be enough room that the edge of the old race gets stuck in the bore a bit. Just drive (hammer) it from the side and it should drop right out. If you have a bench grinder you can remove a bit of the outside of the old race to keep this from happening.

Once the races are installed, paint the hub with a high temp paint to seal up the bare metal and inhibit rusting. I like to hit it first with Duplicolor Rust Fix to encapsulate the rust (let dry 24 hours!) and then paint it with the high temp paint. Protect your new races and studs from overspray, keep them clean! Once the hub is painted and dry, then wipe out the seating area for the new seal and install it, taking care not to distort it. Get it started into the bore and then work your way around it to drive it in. I have a hard plastic headed hammer for this but a regular hammer will work fine as long as you take care to not distort/dent the seal (you still have to exercise care even with a plastic hammer head).

I'll keep an eye out for your return if you have questions but if I miss it please feel free to PM me to get my attention.
 

DrDoug

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Jan 16, 2014
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Is that a chunk of hub missing or is it designed like that? IDK as I haven't worked on a 60's car since the '70's. If in fact that is a chunk that broke off I would doubt the integrity of that hub and replace it, if I'm wrong I apologize in advance.

Nope, no problem there. That's the way the casting is.

What wasn't reasonable was how condescending and smarmy you were throughout your post. You talk as if anyone without your level of experience, or who disagrees with you, is an idiot. It makes taking any advice you supply difficult. There's no reason to be so negative towards someone who is actively seeking your opinion as part of a discussion.


I apologize and am sorry for coming across as condescending or rude.
 

ndmrpwr

Member
Feb 14, 2010
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Very much pertinent information here from DrDoug! I am from the same era. Worked on all the same stuff. Old school works well too!
 

phucheneh

Diamond Member
Jun 30, 2012
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Every single shop out there seats studs by running a nut down on a regular basis. There are specialty tools on every tool truck for that purpose. But most just use a spare nut and some washers. Hell, I usually just use a larger nut.

There is no danger of snapping the stud. There is little danger of stretching the threads. I use my fairly weak (weak because I've been using it for like nine years without a rebuild) 1/2" impact with the same extension and flip socket I use to tighten lugs on wheels. If it had the balls to damage a stud during replacement, it would damaging studs all the damned time.

It irks me when someone insists that because you CAN fuck something up by doing it a certain way (or more specifically, they have fucked it up before), that way must be wrong.

You can damage plenty of shit with a hammer, too. If you can't competently pull a stud through with an impact, I don't think I'd trust you to swing a hammer, either.
 

DrDoug

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Jan 16, 2014
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The great thing about this country is that everyone is free to do things the way that they see fit. Regarding installing studs the way you describe, go right ahead and keep doing it your way. Hardened bolts have a finite number of times that they can be stretched/released (why do you think they break?). If you want to start your bolts out that way then that's your decision. Second, the while you can pull a stud on that way, the threads are not designed for that purpose. I'll continue to install them my way and if asked I will recommend the same. You are free to do the same thing and the OP can decide what way he wants to do it.

Everyone is happy then, right?

ETA: One thing I just thought about is that while this method can work with a used hub/rotor, I bet it won't with a new rotor hat or hub. In fact, I would bet that in most cases the stud would break due to the forces involved. The splines from the old studs have already cut the knurl pattern into the old part(s), placing less pulling forces on the new stud/threads than when installing new studs into a new rotor/hub. In this case, the stud splines have to cut a new path into the new part(s), which are made out of hardened steel. The OP is in this position with the new rotor hat and I would not recommend your preferred method. Even then, sometimes a BFH and drift are not enough for the job and that's when it's time to hit up the local machinist if you don't have a press. In this case, the rotor hat cross-section is thin enough that the BFH method should work fine.

Regarding there being a tool for drawing a stud into place, as a mechanic over the years I have seen many brainstorms implemented in tool form from mechanics. Many of them are unnecessary or detrimental to performing a good job while some of them are good ideas. At one time or another every good mechanic has made a specialized tool to work on an application where a regular tool won't work. Some are good ideas, some are not. This tool might be great for a shop that wants a job done quick so they can get on the next one but I'm the kind of guy who wants the job done right because it's my car.

The lives of my family depend on good repairs in a job like this, I'll take the time to do it right.
 
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JCH13

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Sep 14, 2010
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The great thing about this country is that everyone is free to do things the way that they see fit. Regarding installing studs the way you describe, go right ahead and keep doing it your way. Hardened bolts have a finite number of times that they can be stretched/released (why do you think they break?). If you want to start your bolts out that way then that's your decision. Second, the while you can pull a stud on that way, the threads are not designed for that purpose. I'll continue to install them my way and if asked I will recommend the same. You are free to do the same thing and the OP can decide what way he wants to do it.

Everyone is happy then, right?

ETA: One thing I just thought about is that while this method can work with a used hub/rotor, I bet it won't with a new rotor hat or hub. In fact, I would bet that in most cases the stud would break due to the forces involved. The splines from the old studs have already cut the knurl pattern into the old part(s), placing less pulling forces on the new stud/threads than when installing new studs into a new rotor/hub. In this case, the stud splines have to cut a new path into the new part(s), which are made out of hardened steel. The OP is in this position with the new rotor hat and I would not recommend your preferred method. Even then, sometimes a BFH and drift are not enough for the job and that's when it's time to hit up the local machinist if you don't have a press. In this case, the rotor hat cross-section is thin enough that the BFH method should work fine.

Regarding there being a tool for drawing a stud into place, as a mechanic over the years I have seen many brainstorms implemented in tool form from mechanics. Many of them are unnecessary or detrimental to performing a good job while some of them are good ideas. At one time or another every good mechanic has made a specialized tool to work on an application where a regular tool won't work. Some are good ideas, some are not. This tool might be great for a shop that wants a job done quick so they can get on the next one but I'm the kind of guy who wants the job done right because it's my car.

The lives of my family depend on good repairs in a job like this, I'll take the time to do it right.

This is one of the instances where your intuition is misleading you. The phenomena you're referring to is fatigue, and for a given high-grade steel one can stress the bolt to very near its yielding point (i.e. stressed to it's 'proof load') tens of thousands of times before failure is induced. The proof load for a 12mm stud is around 18,000-20,000lbf (equivalent to a 9-10ton press) which should be plenty to draw in any stud. For a 14mm stud the proof load is around 25,000-27,000lbf.

You are perceiving that your method is the 'right way' to do things because you've never seen a failure. I would wager that there are people out there that have never had a stud break by drawing it in with a nut, but have seen issues when hammering in studs. Neither cases provide any justifiable, tangible, proof of being the 'right' way of doing things.

Here is my reasoning behind my opinion, back by some real technical understanding. I may not have wrenched on boats and cars for the last 30 years, but I am a mechanical engineer who has designed and built cars from scratch, raced auto-x and endurance, and have spent the last 8 years or so wrenching on cars.

About the studs... Wheel studs are hardened steel, and hardened steel gains strength at the sacrifice of ductility (ability to deform without cracking). So I would choose to draw [12mm] studs in with a nut because the threads and shank are certified to carry 9-10tons of force through their threads, shank, and cap without any significant detriment to longevity. The torque required to generate this force on a 12mm stud is around 170ft-lbs, which is quite a lot of torque for a small stud all things considered. The reason I would choose not to use a hammer is that the hardened steel stud is less ductile (more brittle) than your average steel and thus more prone to cracking. A brass drift does help avoid cracking because it will deform before the steel stud, but it just doesn't play to the (literal) strengths of a hardened steel stud. Both are probably fine methods of installing a stud, but I prefer to use a nut because IMO the likelihood of over-torquing a wheel stud is very low.

Stud failures are (I believe) most commonly found at the root of the threads because of bending stresses being concentrated by the threads near the bottom of a stud. Bending stresses are usually a result of poor torquing procedures. Though I will certainly acknowledge that gross over-torquing of studs can most certainly lead to straight-up tensile failures.

About melting loctite... I'll address the faulty example of the cylinder sleeve that you gave first. "Thermal abuse" isn't really a thing... there will be a lot of heat (as in joules) passed through the areas around a cylinder sleeve, but the temperatures seen by the outer surface of a cylinder sleeve are relatively low due to the engine's coolant. The outside surface of the cylinder wall should never go above 230-260F (pressure cap rating dependent). If these temperatures were surpassed there would be spot-boiling in the cooling system, a rare occurrence usually only present in serious track cars. Thus loctite used on cylinder sleeves would stay well within its operating range.

Regarding loctite melting around wheel studs. The heat generated in a brake rotor is dissipated in two ways: convection to the air flowing around the rotor, and through conduction into the wheel and hub. Now, yes, the wheel does make a really good heat sink. This is a reason why many race cars and performance cars use aluminum wheels - aluminum has great thermal conductivity. But a brake rotor is much more thermally-coupled to the hub than to the wheel because they share a much larger mating surface area. Thus the hub face will be at nearly the same temperature as the rotor hat. Also note that the studs themselves don't have to be at 450F, just the hub itself, the outer perimeter of the loctite melting is enough. The studs themselves are actually somewhat thermally isolated from the hub and wheel because of the splines and lug nut, those don't provide a lot of real mating surface area, and loctite is a lousy conductor of heat compared to metals.

Here is a really interesting article wherein an S2000 was driven up to 60-70mph and then braked down to 0. After 4-5 runs of this the brake rotor top-hat is around 560F, and after 10 cycles one can clearly see the top hats reaching nearly 770F. To me, this is VERY strong evidence that the hub could easily reach 450F. Of course this is quite an extreme amount of brake heat, most of us aren't running out there and going 0-60-0 ten times in a row. But, coming down a long steep hill or mountain, spirited driving, etc. could lead to a similar situation IMO. More to the point I have seen "dark-blue" to "blue" discoloration on street car brake rotors which indicate rotor temperatures north of 550F. This isn't a common thing to notice since regular use of the brakes will simply grind this coloration off (the layer is very thin) but it is anecdotal evidence of temperatures similar to the MotoIQ article on street cars' rotors.

Also note that in these MotoIQ tests that the wheel is considerably cooler than the brake rotor, the rotor surface itself is considerably cooler than the brake top hat, and the outer tip of the stud is still quite cool despite the brakes and wheels being considerably warmer. This firmly disproves the assertion you made that the wheel, studs, hub, etc. are all at the same temperature. They can very clearly be different temperatures, by hundreds of degrees.
 

DrDoug

Diamond Member
Jan 16, 2014
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1,629
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This is exactly why I prefer to keep mechanical discussions on a forum where mechanics hang out, internet experts abound (and I know here I am just that too, another internet expert) and I just don't have time to argue with all of the internet experts. I know about bolt stretch as I have measured it many times in my former line of work, I know how hardened metal behaves because I have worked with tons of it in a variety of ways.

I'll quote the one thing you said that kills your last statement for me:

Stud failures are (I believe) ...
You "believe"? What is this, some religious faith exercise? Well praise Jeebus and believe what you want, I know what I know from first hand experience as do many others who have made a living repairing vehicles. For example, Loctite is recommended by LOCTITE for the purpose of retaining all kinds of studs and more specifically, wheel studs. There is a reason for that, despite your beliefs to the contrary. Do yourself a favor and get an IR gun (you do own one, right? I do) and do some measurements yourself, there's a chance you might learn something very valuable about heat dissipation.

I'll leave you to your way of doing things, just like I'll leave it to the OP to decide what he wants to do. Neither affects me in any way and therefore it just really don't matter to me. Now if this really matters to you and you think you are right, go find a good mechanics forum and get to convincing them!

I'll be polite and bow out of this "discussion" with you, the floor is all yours.

ETA: Your last paragraph says exactly what I've been saying, contrary to your interpretation. Of course the damned wheel doesn't reach the temperature the rotor does, that's EXACTLY MY POINT.
 
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ISAslot

Platinum Member
Jan 22, 2001
2,879
97
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Managed to remove the studs. I didn't even need a BFH. A normal one did the trick. I got both all apart. Didn't get to reassembly yet. Maybe next weekend.

Updated album:
http://imgur.com/a/sJExX