Post by tedebayer on Dec 30, 2009 14:12:12 GMT -5
(I wrote this for Clemson Sports Car Club autocrossers ... thought I'd share for new folks that might be interested... didn't go overboard on tech.) - Ted
You ever thought about how much stress there is on your lug nuts in a high speed turn? How about the shock on those threads with you YANKING your steering wheel back and forth at speed? Ever thought about what it feels like when a stud snaps or a few lug nuts pop off...or worse, you see your wheel bounding into the courseworker/spectator area while your A arm digs into asphalt...
Okay... now that you have the sick feeling in your stomach, how do you prevent it from happening to you? TJ and I ran Elvira (our Miata) for two years on the studs it came to us with. The past owner autocrossed it in CSP for three years in Niagara Falls area. After we ran them for two years, changing tires twice an event, we decided to try some lightened lug nuts. We bought a "el cheapo" EBAY brand and could tell a definite difference... after the second event, the threads stripped out of the inside of them like slinkys. We got a nicer set and they lasted three events before we started losing lugnuts the same way. We kept buying extras and replacing them and that got expensive and there was NOT significant gain for the risk.
I sought out some knowledgeable people and did some research. We were torquing to 72 pounds as recommended... with a torque wrench that was WAY off. First - We got a good one and found out we were over torquing. Stretch in threads of nuts and stretch of threads in studs. Secondly - we found out 72 is good on new dry studs. On older or lubricated studs...it's different. If you are not using a torque wrench, borrow one. Tighten the wheels like you ALWAYS do.... then check it with a torque wrench. Most of the time, you will find you are 150% over spec. Third - ALWAYS use thread lubricant. It's gucky and gets on your hands. Wear gloves or swipe a box of latex gloves from your family doc... especially for changing tires before the event where you will carry that stuff to your steering wheel while driving. It will make your lug nuts and your studs last longer. Fourth - once every couple of months of competition, take a good magnifying glass, clean your lugnuts and studs and take a close look. You can see when there is wear. You should see the wear in the nut first but over time, the threads on the studs DO wear. The studs are harder but over time and if you have over torqued, you will stretch them. Autocrossing, you are changing your wheels twice per event. These nuts and studs were designed for street use ... to be used once every two to three years (when there is a flat or new tires to be mounted). I'm keeping it simple here. Talk to one of your stress engineer buddies and they'll tell you WAY more than you ever wanted to know about threads, density and stress loads and <yawn>.. stuff.
So you checked the nuts and they are getting bad. Replace them. I would not recommend super light paperweight nuts.... they ARE light... so when they pop off, they don't travel as far and you can find them and throw them away.
They are NOT worth the risk. Forget rotational mass and think of safety. Skip lunch for two days in a row before the event, eat some raisin bran and that will equal the gain of super light nuts. <S> If you are going to replace the studs and plan to autocross or track day in the future, bite the bullet and get better ones from ARP or H&R... if you are planning on using spacers down the road...might be a good time to get longer studs too. (Don't go overboard... 1 1/2 inches of spacer on each wheel usually creates bump steer and changes your steering geometry so your alignments are crap again. There is a point of diminishing returns ... wider IS usually better but there is a point...). Installing new studs is a pain on some cars... fire and ice and directional threads and... go see Tire Kingdom. On others, it's so easy you can use washers, the nut and a socket wrench to PULL the splines of the stud into place. Read your instructs and follow them...but I use blue Loctite whether they say to or not. Won't hurt. Once you are done, lubricate them and don't over torque.
One last note... when we changed Elvira's studs ... we found out they were the original OEM studs from 1993. Four to five years of heavy AX and 140,000 miles. Magnification showed the threads were 50% gone. Hate to think what could have happened. I have seen wheels come off of cars during an autocross twice... one time, the car A arm dug in and the car almost flipped at 40 mph. THIS is a cheap simple part of maintaining your car for competition... if you break a stud or lose some nuts and a wheel, the possibilities of further damaging your car, you or others goes upwards really fast.
You will find marked on the back of Bandit's front wing staring me in the face on every hillclimb launch...
BF-BF-BS
Be Fast - Be Fun - Be Safe.
Besides, if I have a wreck, my wife will nurse me back to health and then she'll kick my rear!
Ted E. Bayer
You ever thought about how much stress there is on your lug nuts in a high speed turn? How about the shock on those threads with you YANKING your steering wheel back and forth at speed? Ever thought about what it feels like when a stud snaps or a few lug nuts pop off...or worse, you see your wheel bounding into the courseworker/spectator area while your A arm digs into asphalt...
Okay... now that you have the sick feeling in your stomach, how do you prevent it from happening to you? TJ and I ran Elvira (our Miata) for two years on the studs it came to us with. The past owner autocrossed it in CSP for three years in Niagara Falls area. After we ran them for two years, changing tires twice an event, we decided to try some lightened lug nuts. We bought a "el cheapo" EBAY brand and could tell a definite difference... after the second event, the threads stripped out of the inside of them like slinkys. We got a nicer set and they lasted three events before we started losing lugnuts the same way. We kept buying extras and replacing them and that got expensive and there was NOT significant gain for the risk.
I sought out some knowledgeable people and did some research. We were torquing to 72 pounds as recommended... with a torque wrench that was WAY off. First - We got a good one and found out we were over torquing. Stretch in threads of nuts and stretch of threads in studs. Secondly - we found out 72 is good on new dry studs. On older or lubricated studs...it's different. If you are not using a torque wrench, borrow one. Tighten the wheels like you ALWAYS do.... then check it with a torque wrench. Most of the time, you will find you are 150% over spec. Third - ALWAYS use thread lubricant. It's gucky and gets on your hands. Wear gloves or swipe a box of latex gloves from your family doc... especially for changing tires before the event where you will carry that stuff to your steering wheel while driving. It will make your lug nuts and your studs last longer. Fourth - once every couple of months of competition, take a good magnifying glass, clean your lugnuts and studs and take a close look. You can see when there is wear. You should see the wear in the nut first but over time, the threads on the studs DO wear. The studs are harder but over time and if you have over torqued, you will stretch them. Autocrossing, you are changing your wheels twice per event. These nuts and studs were designed for street use ... to be used once every two to three years (when there is a flat or new tires to be mounted). I'm keeping it simple here. Talk to one of your stress engineer buddies and they'll tell you WAY more than you ever wanted to know about threads, density and stress loads and <yawn>.. stuff.
So you checked the nuts and they are getting bad. Replace them. I would not recommend super light paperweight nuts.... they ARE light... so when they pop off, they don't travel as far and you can find them and throw them away.
They are NOT worth the risk. Forget rotational mass and think of safety. Skip lunch for two days in a row before the event, eat some raisin bran and that will equal the gain of super light nuts. <S> If you are going to replace the studs and plan to autocross or track day in the future, bite the bullet and get better ones from ARP or H&R... if you are planning on using spacers down the road...might be a good time to get longer studs too. (Don't go overboard... 1 1/2 inches of spacer on each wheel usually creates bump steer and changes your steering geometry so your alignments are crap again. There is a point of diminishing returns ... wider IS usually better but there is a point...). Installing new studs is a pain on some cars... fire and ice and directional threads and... go see Tire Kingdom. On others, it's so easy you can use washers, the nut and a socket wrench to PULL the splines of the stud into place. Read your instructs and follow them...but I use blue Loctite whether they say to or not. Won't hurt. Once you are done, lubricate them and don't over torque.One last note... when we changed Elvira's studs ... we found out they were the original OEM studs from 1993. Four to five years of heavy AX and 140,000 miles. Magnification showed the threads were 50% gone. Hate to think what could have happened. I have seen wheels come off of cars during an autocross twice... one time, the car A arm dug in and the car almost flipped at 40 mph. THIS is a cheap simple part of maintaining your car for competition... if you break a stud or lose some nuts and a wheel, the possibilities of further damaging your car, you or others goes upwards really fast.
You will find marked on the back of Bandit's front wing staring me in the face on every hillclimb launch...
BF-BF-BS
Be Fast - Be Fun - Be Safe.
Besides, if I have a wreck, my wife will nurse me back to health and then she'll kick my rear!
Ted E. Bayer
