Broken / cracked lugbolts after last Track Day!! pics

[DriveHard]

I though it might be important to share this discovery.... I was quiet suprised myself..and ive been in the business a long time..

This past week end was my last event of the year.. had 8, 25 minute sessions at summit point.. thats approx 100 laps / 200 miles.. This was my 6th event of the year + add about 10 auto crosses...

I drove to and from the track from NY on my Hankook RS3's.. i had to heat cycle 2 tires, as i damaged 1 the week prior to leaving..

Preface.
I always torque my LugBolts to 95/100 Ft lbs

the bolt in the pics are stock oem from day of delivery.

the car is 15 months old and the lug bolts probably have 12 track days on
them and over 20 auto x's

i also have winter wheels that i take on and off .

Upon checking my car out at the shop / doing brakes etc.. after last track day. 3 lug bolts snapped on the way OFF.. 2 on the left rear and one on the right rear ... all fronts seemed ok.

The bolts were not cross threaded or corroded into the hub at all in any way shape or form. in fact when we got the wheel off, we were able to spin the 3 broken parts out by hand. Look at pic where i pointed to a similar "corrosion line" where i think another fracture is starting

disclosure: i did have a bad "off" on saturday >>> 100 mph spin into the gravel and onto the race track... BUT when i went to the pits, i checked everything and they were not broken at that point.

My thought is that they streatched from repeated on / off / torquing ???


I guess these bolts have a life cycle???

Thoughts ???

[IGoFast1589]

That's pretty stupid... Good thing they weren't stuck in the hub. Guess it's time for some ARP lug bolts.

Never understood why BMW has lug bolts versus lug nuts that fasten to bolts in the hub. Just makes taking wheels on and off more annoying.

[Dackelone]

WoW! You are one lucky SOB. I think I would replace all those lug bolts ASAP. Maybe ee if BMW could warranty them. I wonder if it was just a bad batch of steel or something more serious. I have heard of headbolts stretching but never lug bolts.

[Dackelone]

Originally Posted by IGoFast1589

Never understood why BMW has lug bolts versus lug nuts that fasten to bolts in the hub. Just makes taking wheels on and off more annoying.

BMW swicthed over (as all other German markes did) to wheel bolts because it makes for faster vehicle assembly on the assembly line. Porsche was the last hold out - to go to lug bolts instead of "studs and nuts". It is purely a cost cutting decision.

[DriveHard]

Originally Posted by IGoFast1589

That's pretty stupid... Good thing they weren't stuck in the hub. Guess it's time for some ARP lug bolts.

Never understood why BMW has lug bolts versus lug nuts that fasten to bolts in the hub. Just makes taking wheels on and off more annoying.

Maybe just that time for ARP.. do they make short ones enough that will make the car "look" stock.. I dont run spacers or anything ???

Originally Posted by Dackelone

WoW! You are one lucky SOB. I think I would replace all those lug bolts ASAP. Maybe ee if BMW could warranty them. I wonder if it was just a bad batch of steel or something more serious. I have heard of headbolts stretching but never lug bolts.

I guess i was lucky , considering i drove home 330+ miles at 80 mph on those same bolts !! Mind you they broke coming off when i was taking the tires off the next morning, but i guess they were already cracking / streatching..

and yes..i did replace them all on the spot.... My parts dept looked very strange at me when i said i need 20 lug bolts LOL

[IGoFast1589]

You'll have to speak to ARP about that one. I have no idea what they have for our applications.

[pixelblue]

Alex,
You are correct about their life cycle. I'm not surprised at all they broke off with all the on-offs and track days. Part of a good annual prep is to replace bolts or studs. It's a common practice among hardcore trackers such as yourself

[Groundpilot]

The same thing happened to me at WGI this summer. I usually dont check the torque after every session, but that time after the first session i decided to do it and i am glad i did. One of the left front lug bolts snapped. I was able to remove it easily. My friend gave me the brand new lug bolt right before the next session to save my day. When i came back, i let the wheels to cool down and rechecked the torque again.
Guess what, one of the front left lug bolts snapped. Again. The same wheel. Different bolt.
One of the instructors told me that if one lug bolt breaks you must change all of them at once. Luckily i was able to buy 10 new bolts from someone and replaced all front lug bolts before the next session.
At WGI front left tire takes a lot of beating especially with r-comp. tires that generate tremendous grip.
OP, isnt 100 Ft lbs too much? My torque values were 90, but now i switched to 88.
My car only has 15000 miles and 13 track days, with original lug bolts.
After that incident i decided to change lug bolts for the track every year, have track and street bolts seperatly and rotate track ones after every track day. Of course check the torque after every session

[Focusedintntions]

DH,
I'm pretty sure i read somewhere with the stock lug bolts we should only be tqing to about 85ftlbs. Thats what I run. But like any metal that get heated and cool and stressed a lot with track days, eventually they will fatigue and break. Even using arp studs or anything like that will cause eventual breakage. I'm currently waiting on back ordered studs from Vac Motorsports for next year. Just get some of the shorter 75 mm studs and they won't stick out much at all

[DriveHard]

Originally Posted by pixelblue

Alex,
You are correct about their life cycle. I'm not surprised at all they broke off with all the on-offs and track days. Part of a good annual prep is to replace bolts or studs. It's a common practice among hardcore trackers such as yourself

You know... i was gonna wait till after the last event and then replace them...like i just did... i like the street / track lugbolt idea... ill just get another set, although the ARP studs are an idea...

I guess as Dakel said... i was lucky in more ways than one...

and i have to double check that Torque spec i thought it was 95 ish ... ill get back to the thread once i look up official numbers..


Thanks for all the input guys...

[Groundpilot]

Using studs instead of lug bolts is a good idea only if you can afford to replace them often. Like every year, thats how race teams operate.
Replacing lug bols is a lot cheaper imo.

[HondaGoneRogue]

I have the Vorschlag studs but haven't tracked on them yet. Glad I caught this thread. I've never snapped a lug so bringing this to light definitely has given me some extra awareness.

Happy to hear it occurred without incident.

[BrokenVert]

Arent you supposed to change lugs after 5 or 10 trackdays?

[DriveHard]

Originally Posted by BrokenVert

Arent you supposed to change lugs after 5 or 10 trackdays?

So I hear..... I Never knew... at least others will see this and know what may happen.. too credit myself i was gonna due it at the end of the season... I was just 1 event off ..LOL

Its already in my race log... LugBolts changed 11-15-2011 check !!!!!

[IGoFast1589]

I meant that I don't know why BMW doesn't have lug studs from the factory. Makes it a lot easier to guide the wheel on.

[BrokenVert]

Originally Posted by DriveHard

So I hear..... I Never knew... at least others will see this and know what may happen.. too credit myself i was gonna due it at the end of the season... I was just 1 event off ..LOL

Its already in my race log... LugBolts changed 11-15-2011 check !!!!!

So what youre saying is....


They were only 1 day away from retirement?

[SkinnyVT]

Originally Posted by BrokenVert

Arent you supposed to change lugs after 5 or 10 trackdays?

That is overkill unless you are running some serious meat on a 4 lug hub, most people are on a two year cycle depending on number of days on track. It also depends on the quality of the studs used. Personally I am running the mid level bulletnose studs from Bimmerworld on my e30 after switching from the cheap Voshlag ones that are no longer sold due to failures.

[pixelblue]

^ I have vorshlags! Never heard bad reviews. They weren't cheap either. Not that should mean anything these days but I would love to hear what you've heard or experienced. Guess need to change to something else

[Focusedintntions]

do a google search there kori

[HondaGoneRogue]

Oh nozezzzz!!

[HondaGoneRogue]

Skinny is (correctly) referring to these. This was on their site:

We've been selling these wheel studs since 2007 and have sold tens of thousands of them to BMW customers with street cars, track racers, autocrossers, and even professional race teams in GRAND AM and World Challenge. These are not the cheapest wheel stud you can find, nor the most expensive (the ones that cost more are also Made in the USA, and a fine product, just with more middle-men in between the manufacturer and customer). Since we buy these right from the factory and they are made to our specs, we pass along the best product for the money to our customers, and you get our decades of engineering and racing experience + the quality of a 100 year old US manufacturer behind these products.

We have seen and used many other screw-in wheel studs out there, and we can assure you - if you find a wheel stud that costs less than ours, its made in China. No question. Years ago we sold a cheap Chinese 65mm wheel stud and the quality was dramatically worse - the threads were cut not rolled, the material finish was different on every batch, and they were so soft that you could over-install them in the hubs and make new threads in the middle shoulder area. Nothing good to say about them and we dropped them from our catelog. We see several venders selling that same stud for around $1.50, and like always, you are getting what you pay for here. There are also some 75mm studs that look remarkably identical to the Vorshlag 75mm stud that are a dollar cheaper, but these are a Chinese version. They haven't bothered to copy our 90mm studs yet. We've seen these knock-off studs in person and they have very questionable threads and materials. You never know what you're going to get from over there, so if saving a few bucks is worth a wheel possibly falling off, at least now you are forewarned.

[DriveHard]

Originally Posted by BrokenVert

So what youre saying is....


They were only 1 day away from retirement?

Well.... YES..



BTW i did check the official BMW Repair instructions and the correct Torque for the standard M12x1.5 Lug Bolt is 120 Nm

1 newton meter = 0.737562149 foot pounds

120 x .7 = 84 Ft/Lbs
120 x .73 = 87.6 Ft/Lbs
120 x .737 = 88.4 Ft/Lbs

so i guess its safe to say 85 to 90 Ft/Lbs ( or as accurate as you can see the line on the torque wrench