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GT350 Front Caliper Stuck on Studs

Hey Everybody,

I've 2017 GT350 that I semi-regularly track. I installed the Caliperfexion Steel Caliper Studs about three years ago. Over time as I have changed pads for the events and then back to the street use, I have noticed that the caliper does not slide off the studs and onto the stud sleeve extensions nearly as easy as it once did. It's gotten progressively worse over time. In fact, when I last changed the pads back in November of 2021 I had to use a small mallet to lightly tap the calipers off and eventually back over the caliper stud collar (largest diameter portion of the stud).

Yesterday I started working on changing the pads back over to street pads. The driver side front caliper was a giant PITA but after some elbow grease and the small mallet again, I got it off. Re-reading the Caliperfexion stud instructions, I noticed at the bottom of the instructions there was a recommendation to put a light layer of anti-seize on the collar. I did it for the driver side last night but I should mention I hadn't done it previously before that (whoops, that one is one me).

Today I'm working on the passenger side and I have been at it for an hour now and it has only moved an inch and it's stubbornly not going any further off the stud. I decided to try and put some anti-seize on the collar and slide the caliper back against the knuckle to try and get some lubrication between the stud and the caliper hole the stud runs through, but it's not moving in that direction either.

I'm a relatively novice shade tree mechanic, and I'm currently out of ideas. Would anybody be able to provide suggestions on how to:

1) Get the caliper off?
2) Prevent this from happening again in the future?

Thanks

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TMSBOSS

Spending my pension on car parts and track fees.
6,973
4,293
Exp. Type
HPDE
Exp. Level
5-10 Years
Illinois
WD-40, a mallet or soft pad for a hammer and work it back and forth, it will come off. Be sure to clean the studs and the hole in the caliper before replacing.
I went with the stainless version of these studs anticipating this problem.
 
WD-40, a mallet or soft pad for a hammer and work it back and forth, it will come off. Be sure to clean the studs and the hole in the caliper before replacing.
I went with the stainless version of these studs anticipating this problem.

Why would the Stainless version not have this issue?

I eventually enlisted the help of a neighbor who races vintage Corvettes. He managed to get it off with some BIG plastic mallets and a block of wood.

His observation is that the caliper appeared to be binding up on the sleeve. This seems to be reinforced by that the fact that the studs were clean (no gouges or marring) after we got the caliper off. Also, the top stud's sleeve can NOT be pulled off through the caliper.

Corvette neighbor has for run home after getting the caliper off but before he did, he recommended getting some measurements to see if the studs were aligned to each other. I took two measurements along the length of the stud (one close to the knuckle and one further away from the knuckle) to the rotor with some calipers. Both sets of measurements were within 0.3mm of each other (with respect to top stud vs bottom stud). I then took two measurements of the distance between the top stud and the bottom stud (again, one close to the knuckle and one further along the length of the stud) with a tape measure. Both measurements appeared to be the same, but using a tape measure isn't exactly a precise thing.

I cleaned the studs of debris and did the best I could to clean the caliper holes. However, I couldn't get the caliper back on myself. Going to see if the Corvette guy is home today and still has his big plastic mallets.

Anybody else have any ideas? I would like to get the car back on the ground as the passenger side is still up in the air.
 
4,996
5,812
Corvettes are notorious for crappy calipers and internal caliper leaks, I worked on them for years, replacing them with stainless versions, so absolutely great pick on a guy to get advice from. Nest time try a product called PB Blaster, it's the best stuff there is for loosening parts. With regards to the studs, they have to fit tight so there is no "rock", something like crud is causing your problems. If the studs are clean, then check to see if there is something going on in the caliper, they are disparate materials, so they will corrode, sooner or later.
Sounds like you owe your Corvette buddy a 6 pack.
 
1,128
1,101
In the V6L
Aluminum in contact with iron parts, including stainless, can corrode and the corrosion products will jam up the works. Run a round wire brush (brass if you can get one) through the caliper holes and see what comes out. If the studs are clean, get the little bit of rust off and give them a coating of WD40 or an anti-seize paste - just enough to protect the finish of the stud and the caliper innards. I have the black steel studs myself, and I wipe them down every year with WD40. They've been on the car for five years now and they still look new.
 
Hey all,

I've been wanting to give an update for a couple of days now but work this week has been particularly demanding.

Around the same time I posted my dilemma on this forum I also sent a message to the fine folks over at Caliperfexion. Eventually got in contact with Job Tob (pronounced "Jobe" "Tobe"). He explained that he has seen this issue once before (caliper binding up on the studs/sleeves). The resolution was to actually clean the caliper bore holes that the studs slide into with a barrel brush and some DB Blaster. The thought process is that, overtime brake dust and most likely minor corrosion can build up in the bore hole (just like several of you mentioned). Sure enough, once we cleaned that bore hole on Monday night the caliper went back onto the studs smooth as butter.

I have to say that the customer service that Job provided throughout this whole process is literally second to none. He took the time and explained the scenario and fix in such great detail that even a knucklehead like me could comprehend and tackle it. He wanted me to spread the word that anybody who any questions or concerns with the studs reach out to him via their website.
He also recommended the following:

  • Applying ARP Thread Lubricant on the collar of the stud rather anti-seize as anti-seize attracts brake dust which can lead to the issue I was experiencing
  • Applying ARP Thread Lubricant on the 12-point nut that secures the caliper to the stud but be sure to use the "wet" torque value (90 ft-lbs)
  • Cleaning the studs when servicing the the brake system
  • Occasionally cleaning the caliper bore hole out with a barrel brush

I hope this helps out somebody in the future. Caliperfexion's Stud Kit is a phenomenal product and the Caliperfexion team goes to great lengths to ensure the product quality remains consistent and cost-effective (even in this crazy economic situation).

Thank you everybody for your help. I really do appreciate it!

EDIT: Correcting Tob's name.
 
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1,128
1,101
In the V6L
Hey all,

I've been wanting to give an update for a couple of days now but work this week has been particularly demanding.

Around the same time I posted my dilemma on this forum I also sent a message to the fine folks over at Caliperfexion. Eventually got in contact with Job (pronounced "Jobe"). He explained that he has seen this issue once before (caliper binding up on the studs/sleeves). The resolution was to actually clean the caliper bore holes that the studs slide into with a barrel brush and some DB Blaster. The thought process is that, overtime brake dust and most likely minor corrosion can build up in the bore hole (just like several of you mentioned). Sure enough, once we cleaned that bore hole on Monday night the caliper went back onto the studs smooth as butter.

I have to say that the customer service that Job provided throughout this whole process is literally second to none. He took the time and explained the scenario and fix in such great detail that even a knucklehead like me could comprehend and tackle it. He wanted me to spread the word that anybody who any questions or concerns with the studs reach out to him via their website.
He also recommended the following:

  • Applying ARP Thread Lubricant on the collar of the stud rather anti-seize as anti-seize attracts brake dust which can lead to the issue I was experiencing
  • Applying ARP Thread Lubricant on the 12-point nut that secures the caliper to the stud but be sure to use the "wet" torque value (90 ft-lbs)
  • Cleaning the studs when servicing the the brake system
  • Occasionally cleaning the caliper bore hole out with a barrel brush

I hope this helps out somebody in the future. Caliperfexion's Stud Kit is a phenomenal product and the Caliperfexion team goes to great lengths to ensure the product quality remains consistent and cost-effective (even in this crazy economic situation).

Thank you everybody for your help. I really do appreciate it!
@Tob?
 
Sorry, I haven't been here for some time. There's some sharp minds here that have nailed every relevant talking point. Keep your gear clean and you minimize the potential for issues to arise and you stay acutely aware of how various parts are working.

OP is a great guy and I'm glad he shared the issue he was having.
 
47
65
Exp. Type
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Under 3 Years
Erlanger, KY
I am about to replace my original and finally worn-out pads with some G-Loc pads for NCM next weekend and FINALLY get around to installing my stainless Caliperfexion studs while the caliper is free. I have read the instructions several times for "fear" of screwing this up and honed in on the "lubricate the collar" part to resist corrosion. This was a helpful reminder. I also just realized I had been misreading the name as "Caliper FLEXION" and wondering why one would want to incorporate "flex" into a product related to calipers. Now I see it is Cali PERFEXION...and "perfect calipers" makes FAR more sense.:ohdamn::biggrin:
 
47
65
Exp. Type
HPDE
Exp. Level
Under 3 Years
Erlanger, KY
Sorry, I haven't been here for some time. There's some sharp minds here that have nailed every relevant talking point. Keep your gear clean and you minimize the potential for issues to arise and you stay acutely aware of how various parts are working.

OP is a great guy and I'm glad he shared the issue he was having.
So, how does one proceed if the stud never reaches the bottom of the knuckle, making a 5 lb-ft torque impossible? Neither top nor bottom holes prevent the stud from bottoming to the shoulder without force. At 1/8" spacing, the stud turns freely.
 
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So, how does one proceed if the stud never reaches the bottom of the knuckle, making a 5 lb-ft torque impossible? Neither top nor bottom holes prevent the stud from bottoming to the shoulder without force. At 1/8" spacing, the stud turns freely.
Sounds like there's some junk from the oem install still taking up space down the hole. Run the stud down right to the bottom of the hole a few times using the two nuts on the top of the stud. You'll know when you're there because hard to turn becomes impossible to turn. There'll be about 1/8th inch of exposed thread above the face of the mounting base. That'll free up the threads in the hole and once that's done, you'll be able to follow the instructions and finish the install.
 
So, how does one proceed if the stud never reaches the bottom of the knuckle, making a 5 lb-ft torque impossible? Neither top nor bottom holes prevent the stud from bottoming to the shoulder without force. At 1/8" spacing, the stud turns freely.

Sounds like there's some junk from the oem install still taking up space down the hole. Run the stud down right to the bottom of the hole a few times using the two nuts on the top of the stud. You'll know when you're there because hard to turn becomes impossible to turn. There'll be about 1/8th inch of exposed thread above the face of the mounting base. That'll free up the threads in the hole and once that's done, you'll be able to follow the instructions and finish the install.
Sounds like the hole is too deep rather than clogged up.

You can put a steel BB or similar spacer in before you install the stud. A little measuring will get you to the right size.
 
1,128
1,101
In the V6L
Sounds like the hole is too deep rather than clogged up.

You can put a steel BB or similar spacer in before you install the stud. A little measuring will get you to the right size.
Hmmm... seems I misread @CRisolvato's post. Sounds like the '20 R knuckles, the ones FP borrowed from the GT500, have deeper holes than the originals. Caliperfexion would know if the GT500 caliper has the same body depth as the GT500 caliper. If so, then it's possible that their GT500 studs would work for the 2020 R's. Or, as you suggest, measure the depth of the hole and the length of the stud, and put an appropriately sized ball bearing in first.
 
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47
65
Exp. Type
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Exp. Level
Under 3 Years
Erlanger, KY
Sounds like there's some junk from the oem install still taking up space down the hole. Run the stud down right to the bottom of the hole a few times using the two nuts on the top of the stud. You'll know when you're there because hard to turn becomes impossible to turn. There'll be about 1/8th inch of exposed thread above the face of the mounting base. That'll free up the threads in the hole and once that's done, you'll be able to follow the instructions and finish the install.
Perhaps I was not clear in my explanation of what I am experiencing. My issue is not that the stud is too far out and the threads are dirty. My issue is the ball never touches the bottom of the threaded hole in the knuckle.

The install instructions say the ball of the stud should touch the bottom of the knuckle hole then, after being tightened to 5 lb*ft, the shoulder of the newly inserted stud is supposed to be ~ 1/8” from the machined surface of the knuckle.

For my part:
First I cut a channel in and cleaned the old bolt to use as a thread sweeper. After cleaning the internal threads and I am able to finger thread the new stud into the the knuckle all the way down until the shoulder of the stud reaches the machined face of the knuckle. This is the source of my question. My understanding from above instructions is the ball end of the stud should bottom inside the knuckle (which it does not) and permit the stud to be tightened to 5 lb*ft, leaving the stud shoulder and machined face of the knuckle 1/8” apart and roughly 3 7/16” of total stud exposed.

i set the gap at 1/8” and exposed length at 3 7/16”, but did so without any resistance.

I believe once I torque the ARP nut it will keep the caliper in place. It just seems that, since the stud is not at the bottom of the knuckle and the shoulder of the stud is also not on the machined surface of the knuckle, the stud will simply turn in the knuckle until full contact is made in on the shoulder or bottom of the knuckle threads, thereby breaking free the thread locker.

@bauern may have it correct. I ordered 350 studs because the listing indicates for 2015-2020 GT350 and 2015-2019 GT350R. The GT500 part only lists fitting the 2020+ GT500 with no reference to the 2020 GT350R. My mistaken assumption, in retrospect, is not ordering the GT500 studs because the listing did not call out the 2020 GT350R, even though the R shares the GT500 knuckle.

The listing says “*Fits 2020 GT500 and up front calipers only. Does not fit other Mustang models (including the GT350/GT350R).” So I did not buy these

Things are a little tricky now because I am supposed to be at NCM Saturday and Sunday and I either need the correct studs, new OEM bolts, or word that these studs will work even though they are not touching the bottom of the knuckle hole.
 
47
65
Exp. Type
HPDE
Exp. Level
Under 3 Years
Erlanger, KY
Sounds like the hole is too deep rather than clogged up.

You can put a steel BB or similar spacer in before you install the stud. A little measuring will get you to the right size.
Interesting idea. The BB/spacer inside idea might work, but I am not keen on the idea. I would rather not “rig” this setup on a virtually new and otherwise stock car.
 
So, how does one proceed if the stud never reaches the bottom of the knuckle, making a 5 lb-ft torque impossible? Neither top nor bottom holes prevent the stud from bottoming to the shoulder without force. At 1/8" spacing, the stud turns freely.
Had a great conversation with CRisolvato last night with respect to this.

To be clear, stud kits are not offered for the '20 GT350R (they are offered for the '20 non-R though) and for good reason. The hole depths in the '20 R knuckle have been inconsistent and the demand simply isn't there to warrant a one-off.

I took a very close look every knuckle offered for the S550 GT350/GT350R/GT500. The "earlier" GT350 knuckles have been very consistent in terms of manufacture and final machining. This is important as the design of these studs is such that they bottom out in order to achieve the necessary projection above the milled knuckle surface that the caliper mates with. In a nutshell, when correctly installed, you'll see approximately one thread above the nut when properly torqued. This ensures adequate clearance between the fastener and the inner barrel of the wheel.

Ford decided to update the knuckle for use on the '20+ GT500 along with a one year stint on the GT350R but not for the "regular" GT350. I've shown this elsewhere but basically Ford manufactures the raw part and then machines it two different ways so that it will accommodate two different rotor diameters/caliper sizes. I've noted that the final machined part for the GT500 is once again, very consistent. I've also noted that the '20 GT350R knuckle has been somewhat inconsistent with respect to the holes drilled for the caliper fasteners. Mind you, this makes no difference when using the factory bolts as they are not designed to bottom out. So minor inconsistencies at the bottom of the blind hole don't matter to Ford. That said, the use of a stud is not normally precluded as a result of a threaded hole being either blind or a through hole. Studs are normally installed finger tight and do not have to bottom out. When properly torqued, a well designed stud (for example) will stretch just the right amount to impart a given clamp load and won't back out on its own. That said, the studs for these applications were designed to bottom out (again, to achieve a given projection) and thread locker is supplied in case the user does something to relieve the stretch. If the nuts are cross threaded, you may find that you can remove the stud when backing the nut out.

Keep your gear clean and well lubricated. Never remove or try to torque fasteners that are too hot to handle with your hands. Race teams get away with this as it is expected that they replace fasteners that may have yielded, stretched, and become plastic.
 

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