Sprocket hubs failure

Hi,

Well I was about to replace on my SPF GT40 MK2 the rear wheel bearings by Timken wheel bearings but I've discovered why I had to retighten my wheel bearings 3 times last year.

In fact the outside and inside wheel bearings spin on the sprocket hub meaning that the wheel bearings don't work as they should do.

You can see on pictures (red arrows) my problem.

What is the reason to get sprocket hubs in this state ? Maybe a bad assembly at factory (the wheel bearings have never been changed). They may have assembled too lose ?

I've tried to install new wheel bearing but it's the same they spin on the sprocket hub.

The third and fourth pictures show the wheel bearing protection. They are totally destroyed !

Now I have to find a solution: Has anybody met that problem before ? Is it possible to repair the sprocket hubs by adding a part (I don't know the exact name in english) on the wheel bearings location ? The other solution is to buy new sprocket hubs but is the material has been improved (harder) comparing to the ones I have ? what is the price for these parts (sprocket hub and wheel bearing protections)

Thanks for your help. (I planned a trip of 800 miles next week.. I think I'll have to find another solution....).

OliveR
 

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I would say the tolerances were off allowing the bearing to turn on the stub axle. You can have a machine shop knurl the axle so that the bearing will press on with the required interference. I did that with an original Cobra that had the front spindle worn due to poor use.

The knurling process will raise enough of the surface to provide grip to the bearing race.
 

Randy V

Admin
Lifetime Supporter
Hmmm... I would also look into knurling, but the tolerances were definitely off in the machining process.. If you are careful, you could use red Loctite to seize the inner race but it will be a bugger to get back apart for later service.
 

Pete

Lifetime Supporter
Another common fix is to have the area affected built up with hard chrome plating and then have it ground down to the diameter you need.
 
Many thanks for all your relies but:

- my machine shop doesn't recommend to knurl the axle. For him it's a temporary solution. With different effort applied on the wheel bearings and the axle when running the car I'll met the same problem in few months.

- for chrome plating I went to see a guy that could do that job but the price stops me !!! He asked me 850$ (600€) for the job.

I went back to my machine shop and he told me he's going to add a thin ring (1,5mm / 2mm) for the inner wheel bearing and another one for the ouside wheel bearing. Of course he has to remove axle material to install the rings and adjust the rings to the wheel bearings.
Moreover he's going to add a spacer between the two wheel bearings in order to solve the problem for the life of the car....

I'll make pictures once I'll get the parts modified and post them.

OliveR
 
Many thanks for all your relies but:

- my machine shop doesn't recommend to knurl the axle. For him it's a temporary solution. With different effort applied on the wheel bearings and the axle when running the car I'll met the same problem in few months.

- for chrome plating I went to see a guy that could do that job but the price stops me !!! He asked me 850$ (600€) for the job.

I went back to my machine shop and he told me he's going to add a thin ring (1,5mm / 2mm) for the inner wheel bearing and another one for the ouside wheel bearing. Of course he has to remove axle material to install the rings and adjust the rings to the wheel bearings.
(((((((((Moreover he's going to add a spacer between the two wheel bearings in order to solve the problem for the life of the car....))))))))))

I'll make pictures once I'll get the parts modified and post them.

OliveR
PRE-LOAD SPACER..This is what they all need to cure the wheel bearing issue... simple case of a $10.00 part being left out to cost owners heaps, takes a little extra time to get the pre load right, but just about bullet proof after that.
 
Thanks Jac Mac.

For info on 99% of European cars you have a pre-load spacer between wheel bearings.

I cannot understand why SUPERFORMANCE didn't study/think about that when they started rebuilding GT40 !!!!

Superformance is like other replica manufacturers: if you want a car with no problems you have to replace bad quality parts or make adjustments to get reliability !!!

I know many friends who bought Cobra replica or Cobra Csx 4000 (I currently own a 289FIA and a 427S/C): everybody has some problems with engines/clutch (75%) or rolling chassis (25%).
Once you have repaired/adjusted/replaced parts the cars are perfect but many things should have been done/better assembled in factory..

OliveR
 

flatchat(Chris)

Supporter
"Knurling" tch tch tch! -- by ruffasguts engineering.( a desperate measure only)

Your Machine shop has the correct method--- or electroless nickel build up or hard chroming and then finish cylindrical grind the journal dias to the recommended bearing tolerances.
After "plating" (nickel , chroming ) have the parts normalised --to cure hydrogen embrittlement
 
PRE-LOAD SPACER..This is what they all need to cure the wheel bearing issue... simple case of a $10.00 part being left out to cost owners heaps, takes a little extra time to get the pre load right, but just about bullet proof after that.
Were the spacers accidently left out on this car, or do SPF cars simply not come with a spacer at all?

How can this system possibly work without a spacer in between the two bearings? What locates the bearings within the hub carrier? Does the hub carrier have 'steps' machined inside, which the bearing races are pressed against?

I'm looking at the GT40 (original) parts book, trying to understand how it all works, but it's a bit confusing.

Can anybody show me the complete inner workings of these things, i.e. has anybody ever taken it fully apart and photographed all the components so we can see how it is all held together? From the parts book, it appears that the inner yoke has a stud threaded in one end, and a nut/washer on the other, and the bearings, spacers etc. are sandwiched in between. I just can't see what the inner bearing acts against. It would either have to have a spacer between the bearings, or a step on the inside of the hub to locate the bearing race.

Educate me please?

Thanks!

FWIW, I am intimately familiar with the Pantera setup, which (although not pin drive) is broadly similar. They use a (heavy!) cast iron hub carrier; there is a stepped shoulder on the outside which supports a (fixed) ball bearing (not tapered roller bearing). On the inside, there is a smaller ball bearing, which simply presses into the cavity and is free to float. Positioning of the inner bearing is dictated by the use of a spacer sleeve in between the two bearings. The axle slides through the bearings (light press fit), a yoke goes over the end of the axle, and then a nut secures everything together from the inside.

They are known for failing due to inadequate press fit and/or the spacer wearing/fretting, allowing movement of the bearings, which wear 'wagon tracks' on the axle surface. It manifests itself by acting like a loose wheel bearing--the wheel/hub will wobble noticeably. Tightening the nut has no effect, because by this point the axle has worn; the play is taking place between the inside of the bearings and the axle surface. The only proper solution is to replace the axle and bearings, and ensure that things are tightened properly.

A friend used to repair damaged Pantera axles by welding in the groove, then machining them back to spec and having them hard-chromed. After a 'repaired' axle snapped during very gentle driving, he stopped doing that!
 
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What they have is fundamentally a front wheel bearing set up off a 4WD or a fully floating rear wheel bearing of a truck.
They work without spacers ,you have inner outer( tapered )race facing into each other and the cones are pressed into the housings.
The preload is set on the nut which must be locked by a pin or tab.
It is no different to the front wheel bearing inner and outer race.

If you have axial bearings (Balls) then spacers are required.

And yes Jack you can also have spacers with tapered races, but looking at the design of what is there the ID of the race should just be a slip fit onto the axle just like a 4WD front hub.


Jim
 
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Hi Rick,

Thanks for the drawing.

Could you provide me the N°10 parts please ? 2x for inner left and right wheel bearings and 2x for outside left and right wheel bearings ?

OlivieR
 

DaveM

Supporter
I had a similar rear axle that SPF replaced under warranty. Outer bearing should be a press fit and inner bearing a slip fit (to allow for adjustment). Even my replacement axle had a slip fit on the outer bearing so I used green bearing Loctite which has worked well. The wear you have looks more severe. As advised either hard chroming or a replacement axle is the best fix. As to the destroyed seals I check my inner one every time I adjust the bearings and regrease the bearings every 5000 miles. The outer seal usually holds up much better, but as soon as either starts cutting a groove in the seal replace it. Grinding up a seal aggravates bearing and axle wear.
 

Jack Houpe

GT40s Supporter
Knock on wood, I have never had an issue with front or rear bearings but I worry about it, I've listened for noise (thats a joke really) and checked front and rear for play and I don't feel anything unusual before every race. I know Richard from Idaho has had problems both front and rear, he has 35,000 miles or better on his car. Lets see if Jim from CA will chime in, he has more miles than Richard.

If there is going to be a preload spacer there will have to be shims to adjust the preload. Rick is this another kit in the works?
 

Dave Hood

Lifetime Supporter
I live near Dennis Olthoff's shop and he performs all of my maintenance. He's told me that the bearings are an ongoing issue, and said (as DaveM suggests above) that the bearings usually need to be adjusted and regreased every 5,000 miles. Sounds to me like an issue that Superformance needs to address in their manufacturing process.
 
Don't have a horse in this race, but it will depend on the tolerances used in manufacture of upright/axle as to whether shims or just a range of spacers would be reqd, shims more likely since cars are scattered all around the globe. While its not a big deal to set the preload, who ever does it will need to look at the car & owner and the manner its operated to decide on the amount of preload to use as with the alloy upright/steel axle there are some expansion/contraction factors that will come into play with hi-speeds, tire width & brake heat etc.
 

flatchat(Chris)

Supporter
Another thought --- Re the spf spindle --can anyone tell us what material it was made from?
To me, it looks to be something like 1020 steel --judging by the hobbing or brinelling of the bearing journals
If it was at least 1045 or 4340 steel the bearing journal areas could be induction toughened or hardened prior to finish grinding the diameters.

An inherent design fault may also be the culprit -- a FEA (finite element analysis) could high light the issue
 
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