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.

UPDATE: I finally got the car off the trailer and into the garage, I decided to wait for a set of hubs from Logr and install a replacement so I could drive the car instead of trying to use a floor jack. We had a bit of an issue, the first set of hubs he sent me were actually 280Z versions and I had to use washers to space the rotor correctly. Ok, so the damage is minimal and mostly cosmetic but here is a list: 1. The fender is toast but I'll use part of it to repair rust on a free fender I got. 2. The ball joint will need to be replaced (the bottom of it was ground off when it scraped on the ground). 3. The bottom side of the lower control arm was scraped up, the arm is fine. 4. The bottom right side of the cross member was scraped up, it's also fine. 5. There is a fender support right at the back of the fender well (closest to the door), it was folded back and mangled. I was able to mostly straighten it. 6. The lower radiator support was bent up when the car fell off a jack while putting it on the trailer. The radiator seems to be fine. 7. The center of the rim is bent so it will have to be replaced. The deformity happened when the hub broke, didn't cause the hub to break. 8. Two of the studs were stretched enough by the force during the failure that they were loose, these were located in the wheel where it was bent so were in the last part of the hub to break. Hope that made sense. Things that were not damaged: 1. Spindle and strut are fine 2. Brake rotor was untouched, didn't touch the ground. 3. Main chassis components, they are no more or less straight than they were before the incident. This is a real relief, if the chassis was tweaked more I'd be parting the whole thing out. To answer some of the questions: 1. The aluminum rotor spacer I had installed had nothing to do with the failure, it comes no where close to touching the back of the wheel studs. If anyone doesn't believe me just look at the backside of your own hubs and you'll see what I mean. 2. The center of the wheels I have are not completely flat, they touch the hub at the center opening in the wheel and the outer edge of the hub, so this may have contributed to stressing the hub. I'm not convinced of this though as all the lugs were always torqued to 90 ft/lbs which is really not that much and should have evenly spread the force across the hub face even though the surfaces were not actually touching where the studs pass through the hub and wheel. 3. I tried to put the puzzle that was the hub back together but the parts are too distorted. My conclusion is this hub had developed cracks which I didn't see, then failed when I hit the seam in the pavement with the wheel sliding slightly sideways. The Hoosiers are very sticky and the hub was the original 40 year old one that came on the car when I bought it. Bottom line is it's going to cost me the price of at least 1 new Hoosier A6, a ball joint a new wheel, some sand paper, black and gray primer and the time to put it all back together. I estimate $600.00 to get it back to where it was before the incident. Wheelman (Ken Wheeler)

Ok guys I won't dismiss the wheel flex idea, it just seems that when the wheel is bolted to the hub and it's torqued down (which it was) it creates a stronger assembly which would prevent the center of the wheel from flexing, at least the part that's bolted to the hub. Outside of that center section only the strength of the steel keeps the rest of the wheel rigid. Once I get the car off the trailer I'll take a close look at the center of the wheel and "put the puzzle that was the hub" back together to see if it's possible to tell why it failed. My suspicion at this point is the center of the wheel was bent and putting stress on the hub, why it was bent is the real question. As for the G forces from the video, I'm not sure how accurate they are, we used an iPhone as the measuring device. In prior events we were using an android tablet and saw instantaneous lateral G loads over 1.8, acceleration Gs over .8 and deceleration over 1.0. It's amazing what a good set of sticky tires will do with a well setup suspension. You'll notice there is no aero on the car, it's all mechanical grip. Wheelman (Ken Wheeler)

Thanks Bill, I'll have to look into it, we just hired a new ME where I work who has experience designing car parts and running machining equipment. We might be able to use the company's prototyping CNC to fab up a couple hubs. The part I'm not sure of is dealing with the bearing races that would need to be pressed in once the machining was done.

I won't swear to it but I don't think the rotor spacer ring was touching the studs, if it was there should be marks in the aluminum and there aren't any. I replaced the studs not long ago, that's why they're clean. The more I think about the suggestion that the center of the wheel flexed enough to deform it while was mounted to the hub the less I believe it. I see no way for that metal to flex while it was clamped to the hub unless the mating surfaces were already deformed in some way. I can see how the spokes might flex but think that is highly unlikely unless the wheel slid sideways into a surface at some point, which has never happened I've owned them.

Nope, Diamond Racing. I've had them for about 7 years but they've been strictly used for autocross so not many miles. I got them used from Braap, he might be able to give some history prior to when I bought them. What I find strange is there was never a hint of vibration from them.

Yeah, I went out and looked closer at the wheel and hub, I agree, it really looks like the wheel wasn't bolting flat. This means the left side hub is definitely being replaced as I've swapped the tires left to right several times over the years. It also means that rim and possibly both fronts will be replaced, gets more and more expensive by the minute. I suppose these situations teach lessons that aren't forgotten, really glad nobody was hurt when it failed. All this is making me seriously consider installing a roll-bar. Logr, So, how much do you want for those flares? I'll get back to you about the hubs once I talk to Dan Smith, depending on what he wants for the pair he's got I may take the one you have and possibly 2 if you have that many to sell. Bill, That's not a bad idea, would hubs machined from billet aluminum be strong enough? The ones Techno Toy Tuning sells are machined from 6061 Aluminum, they are sure proud of them, $450.00 a pair for pieces that look to be easy to machine. Wheelman (Ken Wheeler)

I'm going to replace the left side hub when I put eveything back together, I'll take a look at it and post the results. I noticed that shiny ring in the picture as well, maybe thats the root cause of this failure. I never noticed it when ever I had the wheel off the car but that doesn't mean the wheel was mating flat to the hub.

Ok, here are the promised pictures: The hub, or what's left of it anyway: The wheel with the parts of the hub still attached: A couple of shots of the fender damage: 74_5.0L_Z, We are running almost identical parameters, the only difference is my tires are 275/45-16 while your's are 275/35-15. I appologize for the large pictures, I don't know how to shrink them. Wheelman (Ken Wheeler)

Six_Shooter, The jolt at ~59 seconds is a transition from the banked oval part of the track to the "flatter" infield where the timing lights were located. There's also a drain right there that creates a dip I was on the very edge of with my left tire. As for what failed, the hub "ears" the lug studs are pressed into broke away from the center of the hub, I'll post some pictures tonight. The point in the run where the failure occurred was also a transition from one asphalt section to another, there's a seam and the grip level is different between the two plus the car was sliding sideways. Don't worry about offending me, it is humorous to see the tire roll by on the wrong side of the car, at least it didn't hit a cone so my run was clean. One person at the event almost got punched after the incident though, he was being an ass (as usual) saying things like we have to break at least one mod car per season. Logr will know who I'm referring to (his initials are LD). Logr, I'll talk to Ricky to make sure but I remember him mentioning something about finding a co-drive for your upcoming event. If he's going up I'd sure be interested in at least one of those flairs and will take both if that's the only way you'll sell them (are they from MSA?). I'm interested in the Z hub as well but if you don't know it's history it'll only be used to get the car off the trailer and into the garage. Dan Smith has a 2+2 280Z with a good right fender and both hubs that only has 50,000 miles on it. I'm pretty sure the Z31 300ZX hubs were 4-lug for a while, I'm running 300ZX 4 lug brake rotors front and rear right now. I don't want to convert to 5-lug so not interested in the 300ZX hub you have. OH, I have an answer for Brian's seemingly miraculous 42 second run that day, he was following me in grid, got red flagged when my car broke and a course worker ran through the lights on the way to help me but timing didn't delete the time. The timing folks need to fix the official times but I did win my class and was within .026s of Ricky. Wheelman (Ken Wheeler)

Here's a youtube link to a video of an autocross run where the right front wheel hub on my car failed at the end of the run. http://youtu.be/PEOFEHu8H0c The car is a 73 240Z, the hub was the 41 year old original, I was running 10" wide sticky new Hoosier A6s and the car is making somewhere around 400hp at the crank. Not sure there is a moral to the story, I had pulled the front hubs this last winter and they "looked" fine, the lugs were torqued correctly and I'm not running wheel spacers in the front. Does anyone manufacture new hubs that are stronger than the originals? Are the 260 or 280 hubs stronger and are they compatible with the 240Z spindle? I know there's a thread that shows the different shapes (I believe it's one of the brake threads) but I don't remember anything about one hub style being stronger than the others. I have no desire to switch to a 240SX strut arrangement so please don't waste time suggesting that. I have way too much money and time invested in these struts to make a switch. Wheelman (Ken Wheeler)