Cal Club Autocross Forums

Some photos of mine....

http://picasaweb.google.com/moriuntensh ... directlink" onclick="window.open(this.href);return false;

Also loaded them up as a movie on Youtube...

http://www.youtube.com/watch?v=_pgQrMlXnW4" onclick="window.open(this.href);return false;

Will load more slomo vids to the Picasa site soon too...

Did any Street Tire dominate?

Here are my photos from Nationals - as usual, mainly people.

http://www.flickr.com/photos/yeohbaby/c ... 404346703/

Here are my runs:

East: http://www.youtube.com/watch?v=ToCnwKEzsYY" onclick="window.open(this.href);return false;

West: http://www.youtube.com/watch?v=l4SknTV6Mzo" onclick="window.open(this.href);return false;

Mako Koiwai wrote:Did any Street Tire dominate?

ST Winner + top 4-Toyo Tires
STL Winner + top 6-Toyo Tires
STS Winner + 2nd -Toyo Tires
STX Winner + 3rd (and fastest day 2 time ;) )-Toyo Tires
STXl Winner + 2nd -Toyo Tires
STR Winner-Toyo Tires

I'd pretty much call that domination... ;)

STU looks like the only class not overwhelmed by Toyo's. And that fits with the big car unfriendly or overheat the tires concerns with Toyo's. If it had been warmer you would have seen a lot more Hankook front/Toyo rear on the Civics and CRXen.

Great to see a bunch of the SoCal folks at Nats!

Whenever I had time I took photos but unfortunately due to some "incidents" and friends new to Nats were there so I only took a little over 1000 photos (how did that happen?!?). It is amazing how busy that Nationals week can be!

Anyhow there are some photos of SoCal people there so I thought you might be interested. I haven't edited them etc. (too much time.....I dont' know how Mako and others do it! )

Enjoy!

http://2010sccasolonationals.shutterfly.com/" onclick="window.open(this.href);return false;

Reijo

Sleep is highly over rated.

(finally catching up on my sleep in BC Canada! Seeing Reijo next week!)

Reijo Silvennoinen wrote:Great to see a bunch of the SoCal folks at Nats!

Reijo

Great to see you too Reijo. Thanks for the pics.

What is the story on that bent ASP Lotus rim?

Steve Ekstrand wrote:What is the story on that bent ASP Lotus rim?

Wheel departed the car on the practice course

whose car?

Robert Puertas wrote:whose car?

The Lotus Reijo was driving. Hit a Civic (cosmic justice, if you ask me )

Apparently, did some healthy damage on the civic. They came by and asked me what I might have in spare suspension pieces.

Is that the same wheel, off the same car, that went hunting elk in Packwood a year or so ago??

Don

The other year at Packwood, Jay had a Keiser wheel break - yep, all four spokes broke and the remainder of the wheel/tire went hunting elk in the bush as you say Don.....same corner of the car.

I wonder if that had anything to do with this failure? Maybe??? Dunno.

Anyway, a couple of years later, arrive at Nats.....Jay runs Exige in Pro....no probs......TNT course, I get 3/4 of the way around and the engine revs up....thot the grinding noise was 2nd gear flying into little pieces...or clutch let go.....touch throttle, revs up again.....get off gas and ease the car down in speed.....all of a sudden the right rear quarter slams to the ground.....lost a wheel......thot the lug nuts were loose or something. Turns out the ARP STUDS all broke suddenly and without warning (bolts were not loose) ... maybe 40ish mph? I did not see the wheel go but the Civic driver apparently tried to avoid it, missed the front of the car (he was entering the 2nd slalom and I had just started the last straight before the corner into the finish on the TNT course) but the tire/wheel hit the passenger rear fender and wheel.....bending the suspension pieces.....and our wheel.

We hunted all over for studs and a couple of gracious folks came forward with studs (Fred Zust, Bob Tunnell), a little gorilla tape for the broken fibreglas on the fender and picked up/borrowed various easy-outs and drill bits to remove the broken studs and the car was mobile again by 8:30 pm that evening......very grateful for all the help from the autox community! The bent wheel was an extra with practice tires on them so we had good wheels with new Nats rubber on them with us so that did not turn out to be a show stopper.

Looking at the bolts later, it appeared that some stress fractures had begun before and being very hard (thus more brittle) steel, the eventual failure was quite sudden with no warning (at least nothing I noticed).

Jay is going to replace all the studs.....will do so regularly in the future.....might go to a softer/milder steel. All people we spoke to (many with extensive experience) said they had never heard of the ARP studs breaking however it was interesting in that ONE person said he broke one last year....and replaced it before anything worse happened. Moral of the story: Replace the wheel studs every couple of years or so.....or if you hit anything with a corner of the car.....just in case. Lesson learned. Cheap insurance.

In the end why the studs broke is somewhat unclear and we can only make some guesses but it could be any of a number of reasons. Just a freak occurrence it seems.

my guess is the wheels are not hub centering. We broke some studs because we weren't using hub centering rings in our aftermarket wheels, thus adding substantial bending load to the studs which will eventually fatigue them.

Not sure why you would want to go with a softer milder steel. I know there are people who think a softer bolt might bend under a load where a hard bolt will snap. I don't think there's a lot of proof for that, but in any case your studs are prettymuch loaded in tension...maybe a little shear depending on the friction clamp. No significant bending. I'd stay with ARP.

I would speculate the culprit is we apply loads and stresses higher than the engineers had in mind. And have lost most of our safety factors in highly stressed components. But if you over-tightened, ran with nuts loose, had someone go wild with an impact wrench etc, that may have doomed them to failure. Who knows? My mustang has only four studs. Some upgrade to five, but I chose to upsize them with 5/8 circle track studs. Maybe something like that if the problem repeats.

I believe the wheels/spacers were hub-centered. The spacers were bent up and we were offered regular spacers but eventually got replacement ones from Mark Snell matching the original hub-centered one.

Also no air impacts that we know of were used on this car and the nuts were not loose. However the clutch was replaced last year and it might be possible that an air impact might have been used then by the mechanic - we don't know for sure. There was no indication of scuffing on the bolt holes on the wheels either indicating loose nuts.....in fact when we got the broken studs from the concrete the nuts were in the general vicinity of where they should have been.

Milder steel will give more before breaking than harder steel ... harder the steel the more brittle the break - metallurgy 101. That's why all rebar and steel beams etc. in buildings are mild steel....so that there is warning of imminent failure and people have time to get out (yeah, that's what I do for a living - structural engineer).

The one curious item is the fact that the same corner is where the wheel broke....and the car would have been riding on broken spokes/hub at Packwood a couple of years earlier.....maybe that started a crack in a stud or two that slowly propagated.

Mind you we also heard of one other person having broken one of these ARP studs who came and talked to us after the fact.

There were also quite a few people (surprised me - I've never had a problem with any wheel studs to date) who mentioned that they regularly yearly or every couple of years change their wheel studs....simply because of the additional stresses of R-compounds/suspensions/etc. and the fact that we remove the wheels so often (compared to a street car). This might be a good thing to do. These studs were 3 years old.

R

Reijo Silvennoinen wrote: Milder steel will give more before breaking than harder steel ... harder the steel the more brittle the break - metallurgy 101. That's why all rebar and steel beams etc. in buildings are mild steel....so that there is warning of imminent failure and people have time to get out (yeah, that's what I do for a living - structural engineer)...R

Yes it will more gently yield before breaking, but will do so at a much lower stress level than the high alloy. (yeah, that's what I do for a living - aerospace/mechanical engineer, PE ;) ) You do buildings and I do missiles & spacecraft. Seems racecar tech is arguably closer to my end of the spectrum. Interestingly we use neither mild steel fasteners, nor grade-8 stuff in our systems. AN hardware is kinda like grade-5 through 8, but very high quality with a lot of process controls, x-rays, paperwork etc. Our biggest hardware issues have been with counterfeit high-strength fasteners. I've never heard of ARP stuff being counterfeited, but anything is possible. I probably wouldn't buy bargain bolts on EBAY.

A maintenance plan of periodically replacing studs is a good idea. But wheels too, especially lightweights. I've lost a half-dozen wheels over the years, no studs.

BTW, I can't prove it's a good idea, and many will disagree. But because, as you said, we go thru an enormous number of wheel changes compared to the typical road car, I have for several years under-torqued the lug nuts. Torque involves stretching the studs each time and that makes me nervous. Have never had a wheel loosen. But could I be providing insufficient friction clamping? Dunno.

I'm with Bill on this one, Mild steel is the wrong way to go.

I actually increased the torque we put on our lug nuts because i saw wear on the wheel spacers indicating there was rotational slippage which i attributed to in adequate clamping load. I'd think that insufficient torquing would lead to faster fatigue failure vs over torquing because the studs would see way more load cycles if they were "loose" on a rotating wheel then they would by number of over torqued installations.

either way, I was planning on replacing the studs this winter (their 3rd year on the car). 100bucks in studs is way cheaper than new wheels and fenders.

Marshall Grice wrote:I actually increased the torque we put on our lug nuts because i saw wear on the wheel spacers indicating there was rotational slippage which i attributed to in adequate clamping load. I'd think that insufficient torquing would lead to faster fatigue failure vs over torquing because the studs would see way more load cycles if they were "loose" on a rotating wheel then they would by number of over torqued installations.

This man knows what he's talking about when it comes to damaging things. He breaks planes for a living.

Besides the higher loads and frequent wheel changes, we also introduce fairly extreme heat cycling to the hubs and components. Constant thermal expansion cycles are playing havoc with our clamping forces. I'm convinced that the worst damage occurs with inadequate clamping. But also growing up building motors, I'm always conscious of over-torquing. The solution I believe is balanced torque specs and frequent checking. Also be particular aware of new components. New wheels, new spacers, and such will compress (or studs stretch) slightly under their first experiences with a heat cycles and dynamic loads until they "settle in". I blame that particular harsh reality for my only failure.

I'm an economist, educator, consultant, loudmouth, and attorney, not an engineer. But I was in the pits of a race track at two weeks old. ;)

Bill Martin wrote:
BTW, I can't prove it's a good idea, and many will disagree. But because, as you said, we go thru an enormous number of wheel changes compared to the typical road car, I have for several years under-torqued the lug nuts. Torque involves stretching the studs each time and that makes me nervous. Have never had a wheel loosen. But could I be providing insufficient friction clamping? Dunno.

I do the same thing. And one main reason is the belief that most torque specs have to be made with some assumptions including that the car owner will not check his lug nuts for another year. We check our nuts at least every month. <--- not a bad idea

But as you said, many will not agree with this. I have never had a stud or nut fail.

Me.... I used to do nuclear vessel and space shuttle stuff... now... not so much.

Randy Chase wrote:

Bill Martin wrote:
BTW, I can't prove it's a good idea, and many will disagree. But because, as you said, we go thru an enormous number of wheel changes compared to the typical road car, I have for several years under-torqued the lug nuts. Torque involves stretching the studs each time and that makes me nervous. Have never had a wheel loosen. But could I be providing insufficient friction clamping? Dunno.

I do the same thing. And one main reason is the belief that most torque specs have to be made with some assumptions including that the car owner will not check his lug nuts for another year. We check our nuts at least every month. <--- not a bad idea

But as you said, many will not agree with this. I have never had a stud or nut fail.

Me.... I used to do nuclear vessel and space shuttle stuff... now... not so much.

Interesting - great info/comments ... particularly about checking your nuts every year ... particularly important when you get older .

Anyhow, that's what Jay does......under-torque by a little bit......I believe we were using 80 ft-lbs and stock recommendation was a bit more (not sure if I recall, but 85 ft-lbs torque comes to mind....think that is the same as the S2k but maybe that is what I am remembering).

The reason I was thinking "softer" metal was that there would be more warning.....metal would stretch more and give more warning of failure rather than the very sudden failure of all four studs. I wonder if Jay still has them, I could maybe take a photo so you could see - it appeared that there was some initial failure along the outer edges that might have been there for a while (slightly darker indicating some time/expose to the atmosphere?) and then the interior of the bolts all appeared virtually the same except for one where there was a bit of a difference in the pattern of the metal (more relief).

I like Marshall's idea of over-torquing the nuts which gets me thinking about what exactly would be the ideal torque for autox. The factory torque settings would be set, I would think, with the general public in mind. However I think we can all agree that we are not driving like the general public and are stressing the OEM lug nuts/studs/bolts differently. With stronger studs, we should be able to torque them more. As someone mentioned the bolts/studs stretch a little bit with every installation (that's how they work to provide friction etc.). Anyone have a handle on the torque specs and how they are arrived at?

Maybe we autoxers should be torquing our nuts to a different torque than the factory specs as a matter of habit? And perhaps a different one yet for higher strength bolts?

R