I'm posting this in the track section for a reason. Well i've had a few of my rear studs come loose (wobble in the hub). Today i tracked my car with a brand new hub, bearing and fresh studs, well when i swapped my wheels i noticed one stud is loose. I run 50mm studs, 10 MM spacers (hubcentric) and hub rings, with extended lugs to make sure I get a real good bite on the thread.

Does anyone have this problem, doesn anyone know the cause , and the fix??

Thanks in advance.

 

To fix it, put one little spot weld on the backside of the stud/hub.

 

But what is causing just the rear studs to come loose?? Not to mention , just one stud per side is loose at this time. I had 2 loose on my old hub that was bend from going off track.

 

Its possible that when the wheel studs were installed that they didn't seat all the way into the hub. We torque ours when we install them using a spacer or washers to get them totally seated. Its not a bad idea to torqlue them after a lap just to make sure.

 

It's also not a bad idea to check the torque of each after each session. It's not uncommon for one to loosen after high stress and a run through a full heat cycle.

What are you torquing them down to lb/ft wise?

 

80 pounds, to keep them from snapping from the heat expansion of the wheel. I know the torque thing got into a little bit of a heated debate on here.

 

Impact guns tend to hammer the knurle on the studs. I used to have similar problems back when I used an electric impact gun at autocrosses and race tracks to remove and install track wheels. I went back to a breaker bar to loosen the lug nuts and only used the impact gun to spin the nuts on the studs. I never hammered with the impact gun. Never had a loose stud problem again.

 

Just TQ them to 90 lbs to be safe. I had the same problem and that fixed it. 10 more is not going to hurt.

 

Actually, with stock studs, it can.

 

ohh didn't know they were stock. I guess reading FTW.

Well In my experience Tqing them a little bit more isn't really going to hurt. The studs dont expand that much. in the rear is much less. The front is a different story.

 

I agree with Howard........90#'s is too much. Also when you torque the wheels after every session you will be adding to the origional torque setting, ie one more click might be 85, then another click is 90 and another is 95. Its better to take a breaker bar and loosen them slightly and then retorque to 80which is where we torque our wheels.

When we raced a Camaro we had a new crew guy who liked to torque the wheels after each session and we starting having stud breakage.

 

A torque wrench with a digital gauge is very enlightening. Using the "click it twice" technique can easily add 25% to the actual torque at the wheel nut. At WSIR I let a customer use my digital torque wrench after I told him to stop clicking his torque wrench twice on each wheel nut. He was shooting for 80 ft. lbs. and was actually tightening the nuts to over 100 ft. lbs.

+1 also on not torquing to 90 ft. lbs. 80 is plenty.

 

My studs never see an Impact, always done by hand , by me. Guess i'll check them after they cool down every session, the heat thing on the front is know , but i don't have problem with the front at all.

 

Are you using studs with the right size knurl?

Maybe consider going to a stud with a slightly larger knurl so it seats in better. I use the ARP Subaru 3" long stud, machined down shorter since we don't use spacers. The knurl is a few thou over stock (I can't remember the exact size now)

But when I pressed them in there was no doubt they were not going to come loose or slip. Sometimes re-using a stud of the same size isn't as tight and as betamotorsports said just throw a tack on there once you seat the studs.

 

Also, TQ-ing the lugs when they are super hot right of the track is dangerous, and will potentially "stretch" the studs..thus leading to breakage at a future point.

I have seen several HPDE guys TQ the lugs immediately after a session, and then just snap the lug and stud right off.....they just keep turning and turning then BLAMO! (even with a "clicker" TQ wrench)

 

C'mon! You don't understand steel. How hot can the studs be? 250 degrees?

Looking my copy of Machinery's Handbook 26 on page 478 they have a table that lists the "Influence of Temperature on the Strength of Materials" as a percentage of the strength of the material at 70F. Structural steel is 3% stronger at 210F, 32% stronger at 400F, and 22% stronger at 570F.

Whatever you saw at your HPDEs had nothing to do with the temperature of the steel wheel studs.

EDIT: overstated the numbers by 100%

 

Agreed,

I'm not an Engineer...and don't know much about steel's properties...and really don't know what material stock wheel studs are made from...so my comments are "anecdotal"...and not based on science..

However, I've seen it happen a couple or times..but the root cause me be something else completely as you suggested...Thnx for the input/correction!

Question: Don't wheels studs, head, and main studs/bolts "stretch" due to heat and torque?

Laze1

 

Heat is not an issue for steel fasteners until you get beyond 675F. Bolts and nuts that attach rotors and hats use special steel alloys when run in endurance events (Daytona 24, Le Mans, Sebring).

Bolts and studs stretch due to torque and that's why they stay fastened. Without that stretch and resulting tension, no fastener will remain tight. A properly torqued fastener doesn't need any kind of locking device (locknut, cut washer, etc.), but you have to measure how much the bolt stretches to determine proper torque. Easy to do (and a required step) with engine rod bolts but tough to do with head bolts.

Many critical aircraft fastener applications since the 1940s do not specify torque, they specify bolt stretch.

 

May I interject my problem, the overall quality of the metal that Nissan (subsidiary) used for their 350z OE wheel studs.

My dealer broke two, I broke one after I took the car home, drove it for a week and retorqued, actually was loosening one when the stud broke. Needless to say, I replaced all the rears with brand new after-market studs (your going to laugh, but from Auto Zone). Seems that they have not broken yet.

I think I will step it up to the NISMO extended studs, just for more thread/torque as I have extended lug nuts, on stock studs. I doubt this to be a real "issue", but this stud breaking is getting on my nerves once and for all. I have never had any car break studs period until I got the 350.

I talked to my friend Doug at Crawford Z car service in Nashville and he even noted always breaking OE studs on the 350z's as its quite common.

I torque to the factory 85-95 ft/lb (in my owners manual) when the car is "cold" (no heat expansion issues).

-Jonathan

 

Looks like i'm going to try the Nismo studs next, Probably in 60mm instead of the 50's i'm running now.Or the ARP's for the Subaru.