wheelman

Are you sure the springs are the correct ones? When I did that kit on my 240Z years ago I didn't have to compress the springs at all to put the top retainer on, unlike taking off the originals. Mine lowered the front of the car more than the rear and didn't leave much travel before coil bind, but the fronts were progressive so that was supposedly normal. I got rid of them.

It's not even fronts but just the right front hub that has broken twice. Rear stubs were mentioned in the context of converting to 5-lug hubs in the front which would prompt a switch to 5 lug stub axles and associated flanges in the rear. I saw those hubs from TTT but am not comfortable running aluminum hubs considering the issues I've run into with the steel ones.

Thanks NewZed but I'm not putting any 240Z hubs back on the car. I'll either go with the 280 hubs I have (they "look" significantly stronger than the 240 units) or I'll switch to 5 lug 300ZX hubs as Logr suggests. The downside I see for me with the 5 lug swap is sourcing a set of rear stub axles that are configured to work with 300ZX-T CV axles. MM used to offer billet sets but with them being defunct I don't know where to go to get a set. The reason this is an issue for me is I had my 240 inner stub axle flanges modified to work with the CV axles by MM instead of switching to 280 stubs as I should have (my cheap nature bites me again). This limits my options for new stub axles to those that I can get with inner flanges configured for use with the CV axles. I hope all that makes sense.

I don't know for sure Mike but they look to be in the same plane just eyeballing it. As I said before, the most perplexing part of this whole thing to me is I ran that first front pair of Diamond wheels for almost 7 years without any problems. The key difference seems to be when I switched to the Hoosier A6s and had Ricky co-drive with me. I'm not saying Ricky had anything to do with the failures but he has helped me to become faster and he is very fast. It might be that the combination of the A6s and both he and I pushing the car that much harder is what ultimately lead to the failures. For now my plan is to have my brake rotor spacers machined down so I can run that set of 280Z hubs I got from you and stop running the steel wheels. I'll then need to find a set of wheels that will clear my brake calipers (Toyota S12+8 for vented rotors) and I can get decently wide Hoosiers for.

Here are the pictures I promised The back of the wheel center, as you can see they aren't flat but there are 2 "rings" that contact the hub, one right at the outer edge and one very close to the center. Based on the worn paint the rims must be moving a bit and it is apparent that there is contact all the way around both the inner and outer rings. Whats left of the wheel hub The parts that broke off Even though there is contact between the wheel center and the hub there are a few spots where it looks like it may not be completely uniform pressure. I think its time to stop running these steel wheels and also see if I can talk the machinist at work to milling down my rotor spacers so I can use them with the 280Z hubs I got from Logr.

Jon, You mean put a wheel spacer between the hub face and the back side of the rotor hat? That could work, then it would be a matter of finding a rotor with the correct stud spacing and backspacing. Any ideas of ones that would be contenders?

That's an interesting idea, I wonder if anyone has figured out a combination that will work on the Z spindle. Whats got me the most perplexed is I ran essentially this same setup for years with no problems. The biggest differences are Hoosier A6s vs. Kumho V710s (on the same rims), and vented front rotors vs solid front rotors (both of which bolt to the hub in exactly the same manner). There is a HUGE difference in the grip levels between the 2 tire brands but I'm having a hard time accepting that we're producing enough force to actually break the hubs. The one aspect of the site where we autocross that might be the key factor is the courses transition on and off a banked oval track and most of the time it's the right front corner that hits the transition first, plus we're usually carrying a fair bit of speed at those points. BTW: Smart phone G sensors we've had in the car all season have showed lateral G forces as high as 1.8 with 1.4 - 1.5 steady state and linear as high as 1.3-1.4 while braking and between .8 and .9 accelerating. I have no idea how accurate these readings are so take them with a grain of salt.

Good point to both!!! Maybe the admins can combine them into one for us. Hint Hint!!!!

Bill, Yes, I got the PM and it's an interesting idea, I wonder if there's any place to get them now that MM is defunct. The 3.54 gears are almost perfect for the car, I have the rev limiter set at 6000 rpm which is ~68 mph in 2nd with the tires and transmission. If I went with 3.70s I get a little better acceleration but would drop the top speed at the limiter unless I bumped it up to the range you mentioned. Those rpms are way beyond the cam I'm currently running, the power tops out at ~5800 rpm. I'd rather not push the rpms up, the current setup is conservative but provides plenty of torque and HP to make for a very exciting ride. It's too bad we couldn't get you in the car for a ride, I'm sure you would've enjoyed it.

I guess I should've looked closer before starting my own thread on this topic, anyway here's a link to the thread I started: http://forums.hybridz.org/topic/119688-wheel-hub-broke-again/ To answer the questions asked so far: 1. NewZed, No, not the same wheels but the same type of wheels. After the last incident I purchased 2 new Diamond racing wheels 16X10" with 4.5" backspacing. Same basic wheel as the ones I was running before with the exception that the old ones were 9.5" wide. Same tires, Hoosier A6s 275/45-16. We never did settle on a favorite theory in the other thread but I completely disagree with the idea this is due to wheel fatigue or flex, I ran that first set of wheels for almost 7 years before the first failure, this latest hub lasted ~48 runs. 2. CockerStar, thanks for the offer, I may take you up on one of the hubs but not really interested in the rims or the Kumhos. Once you run Hoosiers you'll never go back. I'm not sure what I'm going to do now, the racing season is over and I had already planned to take next year off so I have some time. I have a set of 280Z hubs that "look" stronger but would require modifying my brake rotor spacers, I'm also going to look into going 5 lug or possibly just using the car as a street driver. These "failures" are always going to be in the back of my mind now, especially considering I've dodged the bullet twice with these things. Hmmm, maybe it's time to buy a lottery ticket and retire to some Caribbean island. Edit: I want to correct Phantom, the car we out ran to take FTD wasn't a track prepped Z06, it was a stock Corvette C6 ZR1. Still an impressive achievement considering it was running Hoosiers, makes 700HP and has brake rotors that are as big as my rims (well maybe not but almost) and are made of carbon fiber. It was definitely a good day and this was the 3rd time we'd out run that very car, the other times it was running track slicks which weren't getting hot enough so was traction limited.

I don't have an entertaining video this time as the failure didn't happen on track, but the right front wheel hub broke again. The last time this happened was back in May of this year and the wheel hub totally failed at the end of an autocross run allowing the wheel/tire to exit through the fender destroying it. This time I discovered the failure before the hub completely failed but the same one broke. 2 of the "ears" failed on opposing sides of the hub, broke off completely just like on the hub that failed before. I discovered it at the end of the day when I removed the wheel. Both front hubs were replaced in June with a set I got from Jon Mortenson. They were in great shape with no evidence of being abused or cracked. There were no off track excursions with these hubs but the one that broke only lasted 3 autocross events and maybe a 1/4 mile of street driving. I'll post some pictures tonight. Here are specifics of the car for those of you who didn't read the other thread from May. 1973 240Z 1995 LT1, approx. 400hp at the crank GM T5 transmission Clutch type limited slip R200, 3.54:1 gears Custom CV joint axles Techno Toy suspension arms front and rear (fully adjustable) Ground Control coil overs (springs are 350lbs front and 325lbs rear) Biscuit style camber plates Koni yellow single adjustable struts MSA sway bars front and rear Toyota calipers and slotted rotors on the front, Maxima calipers and solid rotors on the rear Diamond racing wheels, 16x10 on all 4 corners Hoosier A6s, 275/45-16 on all 4 corners Total car weight: 2540 lbs with a 52/48 distribution Suspension setup: Front: -2.5* camber, 4* caster, slight toe out Rear: -2* camber, slight toe in My co-driver set FTD in the car that day and I won my class, it was handling great and was VERY fast, we out ran a Corvette ZR1 with it to take top raw time. One thing I find really strange is in both instances we were able to run 3 autocross events with the Hossier A6s before the wheel hub broke. 2 of us were driving the car so that's about 48 runs (we get 8 runs each per event) between failures. BTW: Bill Davis (Phantom) attended the event and witnessed the broken hub. Wheelman

Thanks for the offer Ryan but there are essentially no stock parts left in the suspension.

Going by the picture they are also WAY too big to fit in the strut tower of a Z.

I've never measured them but they don't get all that hot, the rotors don't show any signs of over heating and my understanding is the majority of the heat the hub sees will come from them. The bearings are new with no signs they were getting hot either, the grease in the hub still looks new. I think the failure was due to old age and the abuse I put the hub(s) through over the years I've autocrossed the car. The location where the majority of our events are held is an old round-e-round track with a mostly dirt/grass infield and some pretty tall asphalt edges. I've spun the car off into the dirt more times than I remember which has undoubtedly taken a toll on the hubs. The event prior to when the failure happened I hit one of those edges sliding sideways but the left side of the car contacted it first, I discounted the idea that the right side may have taken a significant hit as well. Anyway, both front hubs are being replaced and I'm gonna start crack checking them several times a season. If the hub had failed while I was at speed during the run the outcome would have been very different. The thought of that happening almost makes me want to run my 240SX vs. the Z, but it's not as much fun. BTW: I'm running vented rotors on the front and the car has not seen a track day since I've owned it (9 years), I doubt it ever saw one before as it was completely stock when I got it and had been sitting for years rusting away in western WA. It's almost completely back together, assuming I receive the wheels I ordered it'll be ready for the next event.

The rotor never touched the ground. I have roll center (bump steer) spacers between the control arm and strut that space the end of the control arm down below the edge of the rotor. That's why the ball joint was destroyed.