Stripped a lug nut stud

[Paparazzi]

I managed to mis-thread and strip a lug nut stud from my IRS knuckle. Anyone know where to get a replacement stud? I have a bag from some point in my build history but they don't quite fit. (75/128 diameter v 77/128)

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[NAZ]

No magic to it, measure (with a micrometer or dial caliper) and go to your local auto parts store or buy on line through sources like Summit Racing. But don't be surprised if you don't get too far with dimensions like 77/128. The knurl will be listed in decimal inches (or metric) such as .609" -- good luck finding wheel studs with a 77/128" knurl.

[Paparazzi]

No magic to it, measure (with a micrometer or dial caliper) and go to your local auto parts store or buy on line through sources like Summit Racing. But don't be surprised if you don't get too far with dimensions like 77/128. The knurl will be listed in decimal inches (or metric) such as .609" -- good luck finding wheel studs with a 77/128" knurl.

Did some reasearch and found this site which puts my knurled size at 0.601". Looks like it might match this one (Dorman Wheel Stud 610-388.1) at 0.6069" and is for a 1995 Thunderbird which seems about right.

Guess I'll give it a go.

[NAZ]

If you measured the knurl diameter accurately (not with a scale) and got .601 you want to purchase a stud with a .601" knurl, not one with a .607" knurl. That .006" is going to be a tight fit. And the studs you selected show they are metric, are your lug nuts M12-1.5 or the more common 1/2-20? Then have you thought about how you're going to install the new stud? If you simply run a lug nut on it and tighten it to pull it home you may damage the threads of the nut (they are usually softer) or the stud or both. Best to press them in but in a pinch you can pull them in by using a nut, two flat washers, and a lot of oil on the threads, the knurl, and between the two flat washers. But not if you plan to use a stud .006" larger than the one you're replacing. The interference fit for the .601" knurl has likely already been designed for a .003" .004" interference fit and another .006" would make that ~ .010" and that my friend is a big interference fit to pull in with a nut, and if you did manage to install it you're going to have a real tough time removing it when the time comes.

Also, the worst thing is to hammer it into the hole while mounted on the car. Better to buy a tool for doing work like this on the car.

[CraigS]

Every stud I have ever installed was done w/ a lugnut and some hardened washers everything lubed (including the stud threads) w/ bearing grease. I haven't messed up a stud yet but I have messed up some nuts. I use this style nut
https://www.summitracing.com/parts/r...-154/overview/
so I can run it on backwards so the flat side is against the washer stack.

[Paparazzi]

If you measured the knurl diameter accurately (not with a scale) and got .601 you want to purchase a stud with a .601" knurl, not one with a .607" knurl. That .006" is going to be a tight fit. And the studs you selected show they are metric, are your lug nuts M12-1.5 or the more common 1/2-20? Then have you thought about how you're going to install the new stud? If you simply run a lug nut on it and tighten it to pull it home you may damage the threads of the nut (they are usually softer) or the stud or both. Best to press them in but in a pinch you can pull them in by using a nut, two flat washers, and a lot of oil on the threads, the knurl, and between the two flat washers. But not if you plan to use a stud .006" larger than the one you're replacing. The interference fit for the .601" knurl has likely already been designed for a .003" .004" interference fit and another .006" would make that ~ .010" and that my friend is a big interference fit to pull in with a nut, and if you did manage to install it you're going to have a real tough time removing it when the time comes.

Also, the worst thing is to hammer it into the hole while mounted on the car. Better to buy a tool for doing work like this on the car.

Noted on the install tips! I was planning on using a sacrificial nut to pull it on - if I were to go the 'special tool' route, what are the options? I don't really want to have to take the knuckle off to take to a shop to get it pressed in if I can avoid it.

I measured with a micrometer, but it's only a cheapo HF one. Just measured again and depending upon where on the circumference I measure I get readings up to 0.604". When the parts come I'll check with the existing nuts I have to compare the thread sizes before attempting any fit. I also emailed Mark over at Breeze in case he knows what size they are - the IRS knuckles came from him originally as one of his 'Eze-Packs'.

Appreciate the help - between this and my carb thread, I think I owe you a beer or two NAZ!

[NAZ]

I like the press type but they're expensive (>$200) for a one-time repair. Something like this may work for you: https://www.summitracing.com/parts/sum-910112/overview/ but make sure you use plenty of lube and a couple hardened flat washers with lots of lube between them as a thrust bearing (not a hardware store washer -- too soft). By using what is basically a longer nut with more thread engagement there is less chance of damaging the stud. If you use an impact I suggest you use short bursts and not continuously hammer it in place with one pull of the trigger. You'll notice that the nut and stud get hot using the impact.

Remember to use solvent to clean the lube off before torquing your lug nuts or the lube will result in over tightening the nuts.

[Paparazzi]

Looks like you're correct on the thread size - measured against my bolt sizer and it is indeed a 1/2-20. So the one on order's already destined for the 'parts' bin.

I really don't know which to order now - I keep measuring and get values between 0.602 and 0.605 depending where I take the measurement, I'm assuming due to a combination of being worn, hard to ensure a perfect cross-section measurement, and an HF tool.

Thinking perhaps this is the right one. Underhead length is 0.15" longer and knurl is 0.609" but nothing else seems to come close. But then reviews say that the knurl is more like 0.618 - 0.621 which would seem like it's going to be a real problem.

So frustrating ...


Hmm ... looking at it, I stripped about 5 threads. Wonder if I could run a die over it and have sufficient threads left to just reuse this one. Would save a great deal of pain.

[NAZ]

The knurls have been deformed after being pressed into a smaller diameter hole so it's not unusual to get varying dims around the knurl. If you have a way to measure the hole (even a drill set can get you close) that will help you narrow down what you have. And of course the hole will have been changed a bit from the knurls being pressed in. As a reference, most of the knurled studs I've worked with have an interference fit between .002" and .008" with .008" a very tight fit. To make it more difficult to narrow down, there are several sizes close to what you have. Take a look at Summit Racing and search for wheel studs. This will give you a large selection of varying dimensions that may help you determine what may fit.

Of course there is nothing stopping you from opening up the hole size to ensure you have a good press fit. And if you did this to all of them at least then you would know exactly what size stud you need in the future. I've changed knurl sizes to accommodate larger size studs and for repairing loose studs. But you have to be very careful drilling these by hand to ensure you are not drilling at an angle. I use 1-2-3 blocks or precision v-blocks and drill sizes that help me creep up on the final size. And I have lots of practice. Or you could make a drill fixture in your drill press that will clamp onto the hub and help align the drill. A simple block of aluminum that is square will work and if you want to get fancy, buy a drill bushing the size you need and press that into the block. I know, this is more advanced stuff but not out of reach for someone eager to learn something new. And you can practice on scrap material to build confidence.

Working on cars ranges from a major PITA to wow, this is fun. Try to have fun every chance you get.

[Paparazzi]

Well, I'd gauge that about a 4/10 on the NAZ fun scale, perhaps a bonus point for getting my hands dirty on a school night.

Found the 0.609" knurl stud at my local AutoZone. They didn't have the nuts so went to Advanced Auto Parts for those. Also picked up a stud installer - not a cheap tool for a one-off, but given your warnings I figured it an investment to get the stud on cleanly. It took some work - not sure now much is expected but I had a fair amount of my weight pulling down on a 12" socket handle to get it home, figure about 150 ft lb - it's not coming out in a hurry. But it went on very cleanly, seated nicely, no damage to the stud. New nuts and wheel back on.

Couple of beers on me when you're NY way. :-D