I'm about to tackle replacing the front rotors on my 84 and I'm still perplexed...you mean to tell me that a cotter pin, (and a finger tight castle nut) is all that holds the front wheels on?? I can't believe what I'm seeing in the instructions.

I think I understand the part about repacking the bearings but in the end I torque the bolt to 12 ft-lbs to seat the bearings then I back it off finger tight and put in a cotter pin...and that's it? How is it that wheels are not falling off all the time from such a crappy design? I'm completely confused.

Yes it is, but the cotter pin is only keeping the nut from backing off. The nut is actually holding the wheel on.

No different than the design on pretty much every other american car built up through and including the time of the Fiero.


Rich

Nothing wrong with the instructions or the installation. Too much pressure wears out the bearings. The system is designed to snug the assembly up into the proper position. The castle nut is designed to hold it in the proper place and the cotter pin keeps the nut from backing off. In addition to the nut, the shaft in some applications will have a very slight taper to it as well.

Never re-use the same cotter pin (although some do you shouldn't). Use a new pin and make sure you bend the longer tab back over the castle nut. Done.. Cars have been using this system since the 50's. Work's just fine.

------------------
I'm not driving too fast, . . . I'm flying too low.

[This message has been edited by 3084me (edited 02-16-2008).]

quote Originally posted by 3084me: Cars have been using this system since the 50's. Work's just fine.

If you insist then I'll have to believe you. I'm still amazed that front wheels aren't falling off left and right. That design never would have been approved by NASA. We require two fault tolerance to a catastrophic failure. A nut with no pre-load, no safety wire, just a cotter pin. That cotter pin breaks and it's bye bye wheel. I can see why you shouldn't re-use it.

[This message has been edited by jscott1 (edited 02-16-2008).]

quote Originally posted by jscott1: If you insist then I'll have to believe you. I'm still amazed that front wheels aren't falling off left and right. That design never would have been approved by NASA. We require two fault tolerance to a catastrophic failure. That cotter pin breaks and it's bye bye wheel. I can see why you shouldn't re-use it.

Double redundancy is a wonderful thing .... it's all the rage in Nuclear power, as well as rocket science ....... but you won't find it a lot out in the commercial world.... costs too much $$

Rich

As meantioned, the nut holds it together, the cotter pin just keeps the nut from backing off. Just make sure you install the washer.

One thing not clearly meantioned - as you are tightening the nut, rotate the hub at the same time as helps seat the bearing evenly. Pack the bearings with a good wheel bearing grease and ALWAYS use a new cotter pin.

Not sure what the book says about packing the bearings, but the easiest way is to put a gob to grease on your hand and press the bearing 'face' into the grease, turn the bearing assembly and repeat. The main thing is to make sure you are forcing the grease up inside the assembly and around the rollers.

Since you have it apart, consider installing new bearings - they are fairly cheap since you have it apart already...

[This message has been edited by Mickey_Moose (edited 02-16-2008).]

quote Originally posted by Mickey_Moose: Since you have it apart, consider installing new bearings - they are fairly cheap since you have it apart already...

These bearing have less than 500 miles on them. I'm replacing my new drilled and slotted rotors with new stock ones. The drilled and slotted rotors make a huge noise under braking which I thought would subside, but it hasn't

Thanks everyone for your response, I didn't want to kill myself by not torquing the wheels on if that was really required. I suppose all newer cars, (including the 88 Fieros) use sealed bearings? Another reason the 88s are better. Changing rotors is much simpler.

[This message has been edited by jscott1 (edited 02-16-2008).]

quote Originally posted by jscott1: If you insist then I'll have to believe you. I'm still amazed that front wheels aren't falling off left and right. That design never would have been approved by NASA. We require two fault tolerance to a catastrophic failure. A nut with no pre-load, no safety wire, just a cotter pin. That cotter pin breaks and it's bye bye wheel. I can see why you shouldn't re-use it.

They got rid of that primitive, dangerous design on the 88 Fiero.

That old design is also how old knock off wheels could work. Remember those? I believe I'd have to safety wire the center nut on one of those.

[This message has been edited by Formula88 (edited 02-16-2008).]

Jscott1 this configuratuion of front wheel nut w/cotter pin is not rocket science, and has been around almost forever. How many cars in the world? How many of these have had the front wheels fall off? I would hazzard to guess almost none that had not been tampered with in some sort of fashion. Almost every car you and I have ever driven has been this way. Front wheel drives are excluded. Sealed front bearing are a rare item in the American auto industry. I ,myself, have never seen a sealed front bearing with a castled nut and cotter pin.
Joe Crawford
Pointblank

[This message has been edited by josef644 (edited 02-16-2008).]

Really, the only way your wheel could fall off is if your wheel bearing seizes up and shears the pin by rotating the castle nut. Keep your bearings well greased and you'll never have to worry about it.

Hello JScott, I couldnt resist. This is why NASA developed a Million dollar pen for no gravity while the Russians used a pencil LOL thanks Norm

quote Originally posted by jscott1: If you insist then I'll have to believe you. I'm still amazed that front wheels aren't falling off left and right. That design never would have been approved by NASA. We require two fault tolerance to a catastrophic failure. A nut with no pre-load, no safety wire, just a cotter pin. That cotter pin breaks and it's bye bye wheel. I can see why you shouldn't re-use it.

You work for NASA and you don't understand how a double tapered roller bearing works? I hope they don't let you near flight hardware...

[This message has been edited by Will (edited 02-16-2008).]

quote Originally posted by Will: You work for NASA and you don't understand how a double tapered roller bearing works? I hope they don't let you near flight hardware...

Why don't you explain it to me since you know so much...

quote Originally posted by ryan.hess: Really, the only way your wheel could fall off is if your wheel bearing seizes up and shears the pin by rotating the castle nut. Keep your bearings well greased and you'll never have to worry about it.

When I was in the Philippines I saw a jeepney that had had this happen to it. The spindle was sheared right off the steering knuckle.

A couple hours later, the thing was still there, minus the knuckle--no tow trucks, so they fixed it where it broke.

Ed

EDIT: BTW, I'm just as happy that NASA isn't in the business of approving automobile designs. If it were, every trip to the supermarket would cost $500,000 and the car would need a complete overhaul afterwards.

[This message has been edited by edhering (edited 02-16-2008).]

actually the wheel still wouldn't be able to come off even if the nut came off.
the caliper would hold the rotor/hub in place.

No worse than a go-kart. They're usually held on by just a washer then a cotter pin. Some just have a nut. The Fiero has both and it's just an oversized Go-Kart isn't it?

Double fault... I think it is Double faulted. Cotter pin breaks, then the bearing race would have to GRAB the nut to turn it then it might come off if it could push the cap out of place. Then the caliper would have to break as well.
I didn't know you worked for NASA! Tell them you need an assistant. Who needs relocation paid and a Sign on Bonus.

[This message has been edited by DIY_Stu (edited 02-16-2008).]

quote Originally posted by DIY_Stu: No worse than a go-kart. They're usually held on by just a washer then a cotter pin. Some just have a nut. The Fiero has both and it's just an oversized Go-Kart isn't it? Double fault... I think it is Double faulted. Cotter pin breaks, then the bearing race would have to GRAB the nut to turn it then it might come off if it could push the cap out of place. Then the caliper would have to break as well. I didn't know you worked for NASA! Tell them you need an assistant. Who needs relocation paid and a Sign on Bonus.

I wish I could get a signing bonus! The NASA car would cost more like $50 million because we would spend 10 years developing it and only build 3 or 4 of them.

I always knew cars had a lot of single point failures, but I figured the method for holding on the wheels would be a bit more robust.

True if the cotter pin breaks the nut has to spin off somehow. But since there is no pre-load on it, we would assume that it eventually will come off. True the dust cap might keep it from coming off and also the caliper might hold the rotor as well. But to take credit for that we would have to either prove it by analysis with a factor of safety of 2.0 or by test with a factor of 1.4. Now if the dust cap alone can retain the nut and the caliper alone can retain the wheel, then I can tolerate two failures and the wheel doesn't come off.

If the caliper and dust cap cannot retain the rotor by themselves then that would be a zero fault tolerant design, i.e. one failure, (cotter pin) to catastrophic event. I'm still waiting for Will to explain to me what a double tapered roller bearing has to do with anything. As I understand bearings it doesn't do anything to keep the wheel attached.

quote Originally posted by jscott1: If you insist then I'll have to believe you. I'm still amazed that front wheels aren't falling off left and right.

I hear ya. Just that little piece of metal keeping the nut from backing off, kind of scary. Knowing it has been around for almost a half century and we don't see wheels coming off all the time, I can live with it

quote I don't see why you feel the need for personal insults... Yes I work for NASA... and if that design was presented to me I would ask to see how it works, what are it's failure modes and make sure it was a robust design. I don't work in the automotive industry, I don't work with double tapered roller bearings, and I never claimed to know everything. If you want to be helpful then you would explain how it works, if not then shut the **** up and stay out of my thread. have a nice day.

When you don't know something, www.google.com is your friend.

http://www.timken.com/en-us...leRow/Pages/TDO.aspx
http://science.howstuffworks.com/bearing3.htm

Before you blurt out that it just can't be that way, and that it's sooo stoopid for it to be that way and that you're too cool to ever design anything that absurd...

Why don't you sit back and think about *why* leaving torque on the nut would destroy the bearings. Once you figure that out, it should be obvious why there's absolutely nothing wrong with using a cotter pin in that application.

You might come to realize that maybe... just *maybe*... whoever came up with that setup knew what he was doing...

quote Originally posted by jscott1: I always knew cars had a lot of single point failures, but I figured the method for holding on the wheels would be a bit more robust.

Think about the Fiero rear hubs (all years). A single prevailing-torque nut retains the outer axle stub, which is all that holds the rear hub assembly together. There are hundreds of single-point failure items like this in most auto designs ... and in most aircraft designs, for that matter. Cotter pins, safety wire, and prevailing-torque fasteners, when properly applied, fail so seldom that the risk of catastrophic failure approaches zero.

I don't work for NASA but I have machined a lot of parts for Neptec. They are the ones who developed the new camera system for inspecting the shuttles tiles before re-entry. You know the one. It mounts to that big hockey stick we up here call the "Canada Arm". I think it made mostly of hockey tape and old Labatts Blue cans, so I wouldn't worry about your wheel. LOL

Also note that up til the 80's many American cars still had drum brakes on the fronts, and only the nut and cotter pin holding them on. if it let go then, there was no caliper to retain the wheel. in all honesty, in my not so scientific oobservations of cars minus wheels on the side of the road, more balljoints seem to cause relocations of the wheels than I have ever seen bearing failures.
about 4 balljoints to 1 axle bearing I'd say in my observations of cars that lost a front wheel.

I still don;t see Will's point tho, as the tapered bearing has no retaining force due to the placement with the taper facing in, pushing out of the hub in both directions. still leaves only the nut and pin.

Irregarless, I would much rather have that setup than the hubs on my 88. first, they are cheaper, and much easier to maintain. Occasional repacks of a standard axle will go well over the life of the rest of the car in normal use. the hub cannot be lubricated, and all sealed bearings have the problem of the grease moving out of the contact areas, and hardening with age. and while possilbly more secure, I am not sure that a pressed on slug to retain the axle in the bearing is less of a failure point than a threaded nut and pin.

Just be sure you rtoate the hub while torqueing to spec, then back off and snug and pin it. it will snug up when it heats up, which is the reason for that little tiny bit of looseness you have on cold assembly.

quote Originally posted by jscott1: The NASA car would cost more like $50 million because we would spend 10 years developing it and only build 3 or 4 of them.

Oh, I wasn't talking about what the car would cost. Just what it would cost to make the trip.

But yeah, $50,000,000 sounds about right

Ed

quote Originally posted by Will: You might come to realize that maybe... just *maybe*... whoever came up with that setup knew what he was doing...

You obviously have trouble reading the English language...

First I asked you to stay out of my thread
Second, this thread has nothing to do with bearings... I was asking about wheel retention, the bearings have no effect on that.
Third, just because it was done that way for 50 years doesn't make it a good design. There are a lot of crappy designs in the world that have yet to be replaced.

Lastly please don't bother to add insults to my thread... Sheesh, I wish Cliff had given the thread starter "delete" privileges.

oops!

[This message has been edited by AutoTech (edited 02-17-2008).]

The only danger with the design is if sonmeone does "tighten" the bearings. If you do, when they heat up then you will have preload, which will over time cause bearing failure. I have replaced many failed bearings and have yet to see an axle nut that has fell off. Even in days of old, I can remember failed bearings on a 1967 Oldsmobile (it had drum brakes, so no caliper to retain the rotor). They were so bad that I lifted the wheel and hub off after jacking up the car. It came right off. The guy drove the car in, there was nothing left usable from the spindle out.

If this design bothers you (it is an increadable durable design) then take a look at the small "C" clip that is all that holds in the rear axle on most rear wheel drive cars. It seems scary, but works great. Even worse, if they do not use a "C" clip the axles are held in place by a press on retainer.

I want to redesign a car using all NASA and AF explosive bolts. wired to the air bag system. upon impact all parts come loose and separate from the assembly. Leave the passenger cabin intact but make parts fly everywhere!

quote Originally posted by timgray: I want to redesign a car using all NASA and AF explosive bolts. wired to the air bag system. upon impact all parts come loose and separate from the assembly. Leave the passenger cabin intact but make parts fly everywhere!

That would be cool!

Another fun fact is that in the absence of the cotter pin, one side would loosen while the other side would tighten up... they use the same thread on both sides.

My 1930 Pontiac used the same setup on the front wheels (wooden spoke wkeels).

[This message has been edited by fieroguru (edited 02-17-2008).]

quote Originally posted by fieroguru: Another fun fact is that in the absence of the cotter pin, one side would loosen while the other side would tighten up... they use the same thread on both sides. My 1930 Pontiac used the same setup on the front wheels (wooden spoke wkeels).

I was wondering if they used reversed threads on the driver side. Guess someone in the design department fell asleep that day.

I will jump in here for a bit...
The point that everyone seems to be missing is there is no rotational tourque on the nut or the cotterpin..
There is a washer with a tab that locks in to the key of the spindle...
So even if the bearing were to lock up on the hub the nut would just sit there...
So the nut will not fly... :-)
Chuck

quote Originally posted by MotorTV: ... there is no rotational tourque on the nut or the cotterpin. There is a washer with a tab that locks in to the key of the spindle...

I was thinking the same thing, but since my Fiero is an '88 I don't know whether or not the earlier years have a keyed washer and spindle nose. If so, you are 100% correct.

yes, there is a soft steel washer. there is usually no rotational force on the nut. A bearing, or more precisely a lubrication failure will cause the bearing race to wear that washer down on about 10 miles of hiway driving. then the force is applied to the nut, about the same time the pads on a disk brake assembly will start to drag heavily. by the time that the frozen bearing will start to stress the nut, you are at the melting point of steel, and will actually weld the bearing seat to the axle, and destroy the nut. the only retention then is the pad and caliper.
the formerly floating outer bearing seat will weld to the axle shaft, the rollers will disintegrate. the wheel will start to wobble and will be very noticeable to anyone who is not brain dead. with care the care can be driven without what I would call catastrophic failure (wheel passing you on the road) for quite a few miles. been there done that. this is not speculation, but actual observation of the failure of a wheel bearing in real daily driving scenario. any speculation of how ti will fail ususally pales in the light of actual failures.

[This message has been edited by tjm4fun (edited 02-17-2008).]

quote Originally posted by JumpStart: I was wondering if they used reversed threads on the driver side. Guess someone in the design department fell asleep that day.

Ahhhh bet a lot of the youngsters never knew that the early chryslers have left hand lug nuts on the left side and right hand on the right side...
The thought was the lug nuts would be self tightening so they would not come off when loose. As you know they quit that since it was not worth it...
Was fun to watch a newbie with a impact wrench try to take them off not knowing about it...
Guess I'm telling my age..

quote Originally posted by jscott1: I'm about to tackle replacing the front rotors on my 84 and I'm still perplexed...you mean to tell me that a cotter pin, (and a finger tight castle nut) is all that holds the front wheels on?? I can't believe what I'm seeing in the instructions. I think I understand the part about repacking the bearings but in the end I torque the bolt to 12 ft-lbs to seat the bearings then I back it off finger tight and put in a cotter pin...and that's it? How is it that wheels are not falling off all the time from such a crappy design? I'm completely confused.

It's actually not as bad as you think Truth be told, the steering knuckle / spindle is extremely strong. I won't say it's aircraft grade, but it's made to more than withstand the weight of the vehicle. By 1973, almost all vehicles in the United States had converted over to front disc brakes, and EVERY single car used this design. Currently, every rear wheel drive vehicle with independantly sprung front wheels (basically, every SUV, and rwd sedan) uses this design. And basically EVERY vehicle in the late 70s and early 80s used this design (since almost no vehicles were FWD except the Toronado and Eldorado).

A single steering knuckle can independantly support more than TWICE the entire weight of the vehicle it's supporting.

As others have mentioned, the cotter pin is merely there to prevent the castellated nut from backing out.

Nascar, Indy Car, and Formula-1 cars also all use this technology. I was a little surprised when I first learned about this too several years ago. Working in NASA, you probably know very well the difference in various steel strengths. I guarantee to you this wheel knuckle isn't made of pot metal! hahah...

Lets not forget of course, if a nut fails on a car, they slide off the road at 0-50 miles an hour typically. In the space shutting... it blows up.

------------------
Todd,
2006 Pontiac Solstice
2004 Volkswagen Beetle Convertible (Wife's Car)
2002 Ford Crown Victoria LX
1987 Pontiac Fiero SE / V6 (3.2) 5-Speed
1984 Porsche 944 5-Speed
1981 Pontiac TransAm (Olds 455BB)
1973 Volkswagen Type-2 Transporter

50s Mopars had right and left hand threads on the nuts and lugs on each different side. If they got loose the wheel tended to keep them tight. A friend in my Corvette club has a 65 I think that has the real knock off wheels. They all tighten the same direction. We were all on a long drive in the country and the nut spun off, then his front wheel. Luckily it was on a straight right after a curve on a road with 5 foot ditches on both sides. He just ended up with some buggered up threads and a 2" crack in the fiberglass. My 66 Coronet has drum brakes, a nice heavy V8 and a heavy car and just a washer, nut and cotter pin keeps it on just fine.

quote Originally posted by 82-T/A [At Work]: It's actually not as bad as you think ... Lets not forget of course, if a nut fails on a car, they slide off the road at 0-50 miles an hour typically. In the space shutting... it blows up.

Thanks for the explanation....A "+" to all the helpful people in this thread. In NASA we treat all catastrophic hazards the same i.e. loss of vehicle and crew... If a washer floats away during a spacewalk that's considered catastrophic, because its moving at 17,500 mph. Although the odds of recontact are low, they are not zero. In a car, most failures have you on the side of the road, but able to make it home eventually.

I have learned more about how the wheels and axles work, and if I feel a wobble, I will certainly stop to check it out. Now to finish up those rotors.

quote Originally posted by jscott1: Thanks for the explanation....A "+" to all the helpful people in this thread. In NASA we treat all catastrophic hazards the same i.e. loss of vehicle and crew... If a washer floats away during a spacewalk that's considered catastrophic, because its moving at 17,500 mph. Although the odds of recontact are low, they are not zero. In a car, most failures have you on the side of the road, but able to make it home eventually. I have learned more about how the wheels and axles work, and if I feel a wobble, I will certainly stop to check it out. Now to finish up those rotors.

Just to add one more thing, this will NEVER be a point of failure. If it's tightened properly (1/2 turn more than finger tight), then it won't fail. The only thing that does fail are the bearings, in which case you'll hear a grinding and have ample time to pull the car over (you could probably drive 30-100 miles with failing wheel bearings.

------------------
Todd,
2006 Pontiac Solstice
2004 Volkswagen Beetle Convertible (Wife's Car)
2002 Ford Crown Victoria LX
1987 Pontiac Fiero SE / V6 (3.2) 5-Speed
1984 Porsche 944 5-Speed
1981 Pontiac TransAm (Olds 455BB)
1973 Volkswagen Type-2 Transporter

quote Originally posted by 82-T/A [At Work]: Just to add one more thing, this will NEVER be a point of failure. If it's tightened properly (1/2 turn more than finger tight), then it won't fail. The only thing that does fail are the bearings, in which case you'll hear a grinding and have ample time to pull the car over (you could probably drive 30-100 miles with failing wheel bearings.

You are half correct: If they are tightened properly, they will not fail. But, a "1/2 turn more than finger tight" if not proper! It is way too tight and will set a preload on the bearings. They will get tighter as they heat up. They may not fail tomorrow, but the life of the bearing will be drasticly shortened, possibly leading to catastrophic failure.

Proper is tighten the nut down (12 ft lbs). Loosen the nut. Tighten the nut finger tight. LOOSEN the nut till the first cotter key hole lines up. Insert key. The procedure is on page 3c2 of the 86 manual. Should be close in the other year manuals. The design intent is to have no preload on the bearings.