Would you use thread insert on rear hub stud?

[Berkeley Choate]

My son is running a 15YO TonyKart, and while changing wheels a stud pulled out. Would you guys trust a threaded insert for this application? Better yet would be to find a stud that’s 10mm where it threads into the hub but still 8mm where the nut goes on. Does anyone make such a thing?

[Bernie Baldus]

I think a lot of people might be ok with the thread insert.

Some would say it would be stronger than the original threads if done properly.

[Steen Carstensen]

Thread inset or Helicoil would work very well. Install the stud with remove able Loctite  thread locker.

[Berkeley Choate]

Thanks guys. I also just spoke with a pro race motorcycle mechanic and he’s confident that a properly installed Helicoil will be as strong or stronger than the original.

[Walt Gifford]

Allot of the hubs I’ve seen don’t have enough metal around the stud to make a repair like that viable. Also do you have the ability to get the stud repair perfectly square and on center or are you going to free hand it? Helicoils are not the best imho and I’ve seen allot of them done badly. I use solid inserts when there is enough metal to put them in. I’ve custom made double diameter studs in some cases but, you have to be careful, hubs get highly stressed. I moved away from magnesium parts early on when I saw many cracked components and striped out bolt holes on different karts. I would suggest buying 2 new aluminum hubs.

Gif

FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience

[John Matthews]

Hubs are a tuning tool, I would take the opportunity to buy a couple of different lengths for different track conditions.

Yes, a well installed threaded insert will work fine but you have to ask yourself why did the old one strip out. Hubs are one of the most highly stressed components on a race kart, do you really want to be wondering about it when your kid hits the apex at the end of the straight while pulling off a dive-bomb pass????

JMHO,

John

[Gary Smith]

Hi Berkeley,

This has happened to me before, I’ll bet the stud that pulled out has short threads on one end and longer threads on the other end, with the short length of thread in the hub. These studs should measure aprox. 34mm long with 10mm thread length on the short end and 20mm length on the long end. I have found a 40mm long stud with 10mm thread x 8mm thread , drilled and re-tapped the hub, and every thing is good. I have a mill in my garage and able to keep every thing straight.

After this has happened twice, I now pull the studs out any hubs that I acquire, and replace them with  38mm long studs with 17mm thread length on each end. If the threaded hole is not deep enough in the hub I drill and tap them to accept the stud, of course using blue Loctite to finish the job once and for all.

Gary

#55 Honda CR80

[Berkeley Choate]

Fortunately I know an ace motorcycle mechanic, and together we carefully jigged up the hub in his drill press and proceeded to carefully helicoil the piece. I feel pretty good about the repair, especially considering that my son is far from a high-g driver yet.

On another note, my mechanic friend was surprised to see that all the fasteners involved with the hub were installed dry. Now I’d typically coat the axle with anti-seize, but he was saying that the tightening bolt, and pretty well any time I thread into an aluminum piece I should use anti-sieze. My concern is whether the antisieze treated threads would be more likely to vibrate loose. – Which opens up a larger question – when to safety wire, when to thread lock, and when to  anti-sieze? As I walk around the cart, in many cases, that question has already been answered in the form of safety wires and nylock nuts. But what about the other conditions? What and when?

 

Thanks for educating someone who understands that a little knowledge can be dangerous!

 

[John Matthews]

Hi Berkeley,

Glad you got the hub fixed to your satisfaction. There are many items that can be fixed on karts but some that you are better off replacing. Experience and help from others at your track will teach you which is which but there is a “bible” as it were for race car fastener application. Get this book and read it, then you will know for yourself.

 

http://www.carrollsmith.com/books/nutsbolts.html

As for your other questions you should make an appointment with the tech steward at your local track on a practice night and go over your son’s kart with them. Rules vary from club to club so a few minutes spent with the person responsible for tech will save you headaches and heartaches come race day.

I am assuming you’re new to the sport, if not then I apologize but hopefully the info will be useful for someone else.

John

 

 

[Walt Gifford]

My experience is that if a bolt wants to seize, anti-seize doesn’t help much but most things these days are made well enough not to worry. If you think it’s going to lock up just put it in real slow so it doesn’t build up heat. I use anti-seize on engine studs to cut down on corrosion. Most aren’t in karting long enough to worry about that lol.

Something that makes wheel nuts and hub pinch bolts easier for me is a torque wrench.

Gif

FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience

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