Enzo wheel Bearings

Thanks Dave.

Hear me out for just a second.

I understand that the torque on the bolts holding everything together in a sandwich is the preload for the assembly. Or the clamp load needed so that when Jimmy takes his ride to the triple digit zone everything stays together. When things get torqued down all the pressure is put on the outer edges of the bearing races, no? So I don't think that the working of the bearing itself has any preload from the retaining bolts, other than what has already been designed in on the bearing, via the engineered spacing of the bearings between the inner and outer races. From just looking at the diagram nothing is actually forcing the inner/outer race to squeeze tighter together against the ball (?) bearings, because it gets stopped buy the outer rims of the races. Again just from looking at the diagram, and a total guess as I have never seen an Enzo bearing first hand.

What I was talking about was, the bearing getting preload akin to some American tapered wheel bearings (pic below), where the bearings are exposed and held in place via the torque on the spanner nut to the spindle (in the case of the pictures below 70ft/lbs). That was the preload I was refering to.

Not trying to argue, I just wanted to clear up what I was talking about in regard to the preload on the bearings, I'm guessing isn't there from the retaining bolts. But I could very well be wrong, and I am interested to know how it really works on Jimmy's car.
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No worries Ernie...and, certainly no "argument" taken

It's difficult to see exactly how the parts interact with one another from the crude diagram --- my "educated guess" would be that the outer bearing race is interference fit (or, at least held fully captive) to the flange carrier, and that the inner race is snugly matched (if not interference fit) to the wheel hub's outer diameter, and that there is a feature on the inboard face of hub which contacts (and applies force to) the inner bearing race ---- this would allow the outer and inner races to be displaced relative to each other when everything is bolted up ---- thus, effectively applying a preload to the bearing. It is possible that the geometry of the components themselves establish the preload, and the bolts just restrain everything.

The true scenario may be different --- I'd have to physically examine the actual parts to be sure. But, trust me, the bearing IS somehow subjected to a preload ---- you simply can't run a "loaded" axle through a supporting bearing (unless it is a needle roller bearing, which this is not) without a preload......Mechanism Design 101, my friend

 

Oh of course.

It'll be interesting to know how it really works, and what solution Jimmy's mech's come up with.

 

The hub parts are machined to bolt together solidly with the CV joint face, the outer diameter of the CV is also the inner hub., the dimensions are such that the bearing is assembled without preload on this style. These have a large number of small diameter balls in each side. At least that's how they were on the F1 cars. hence my comment about preload. These are a limited life bearing, we would run less than 1000kms in F1. temperature and side loading such as on banking will certainly have a big affect. I'm sure that the street driven cars would be OK apart from the temps from the CCB brakes.

In effect, Ernie says it in his first paragraph above.

 

Ferrari has been using similar double row ball bearings at all 4 corners for some time now. The Enzo's are larger in diameter as you would expect for a car anticipated to be driven at over 200 but similar in many ways. They do have a limited life, do get noisy and is the indication it is time to replace them. The Enzo bearings are a little spendy but I suppose as a percentage of the price of the car not out of line. I suspect if Sal took one out to have a look it would be no mystery why they are noisy.

 

Thats the way to "preload" sealed roller bearings on the Enzo too I reckon.

Tapered roller bearings are preloaded the way Ernie described or the 'feel and drag' method.

I have replaced countless sealed roller bearing units on all makes and models of cars. I torque the CV nut to the specified torque and that is about all you can do with them. You cant shim them etc..etc.

But looking at Ernie's pic, it seems the wheel bolt keeps the bearing in check.

Hope you get some answers from the Engineers JG. Looking forward to hearing what they have to say.

Fitt

 

Know some of the top endurance teams( i.e. Lemans) are using ceramic wheel bearings. Is F1 behind on this high tech engineering improvement?

I didn't think the wheel nut on the Enzo has anything to do with bearing preload...wheel nut just provides clamping force btwn wheel and hub...
Bearing preload(if you prefer to call it that)?????? I thought that was from the thru bolts(cv joint to wheel hub).

On the 908,917,935,936,956,962 Porsches we had really great engineered wheel bearings(SKF)...would easily last 3000+ continuous all out racing miles where we were hitting upwards of 235+mph top speeds(at LM before the chicanes) and approx. 145mph+ average for 24hrs....if there was a wheel bearing failure approx. 90% of the time it was due to the grease/lubrication.

I'd be interested in what type grease is used on the Enzo..if in fact it is using steel ball bearings.

You couldn't use the grease Kluber made for us on a street car.

 

Not havimng acess to a bearing, I am not sure whether they are ceramic ball or not. For sure they have been for a number of years in racing. My last restoration was on the Leyton House Marches and they were using steel balls at that time. They were about $800 each back in 2000. The Reynard F3000 also had the same.

 

I wish I weren't 1200 miles away from you Jim, as I'd love to have a look at these parts myself just out of curiosity. I'm sure you have the staff at your disposal to figure it all out. When you do, if you would please take a moment to post the results, that would be great

 

Jim, not sure of the exact design of your enzo rear bearings but typically there's two distinct flavors: adjustable tapered roller bearings (two sets) or press fit sealed bearings with ball bearings (again, two sets). The tapered bearings are usually set with a process of backing off the nut by a set amount from the point at which some drag is measured, while the press fit are simply pressed to a shoulder and the position of the shoulder sets the bearing clearance.

One mistake I've seen made for the press fit bearings is that the installer will heat up the bearing to allow the drive flange and hub to slide in when the whole assembly won't fit in the press to do it cold....and thereby boils the grease out of the bearing or melts the seal...that bearing isn't going to last very long....

The taper fit with an adjustable lock nut is the superior design, but it takes up more space which isn't always available (CVs get too short for the suspension movement).

Like others have said, examining the bearing is really the only way to tell. If the bearing is worn you'll see "bluing" (heat) and the race surface will look like its been pounded.

 

I would expect to pack more grease into the CV itself. Be sure that you use the GKN Racing grease or equivalent, a much higher operating temperature range than the stuff comes in a standard CV package.

 

It's also interesting that the inner CV boots are installed with the clamp on the small diameter to seal and locate the boot, whilst the outers are without that clamp and have 'shrunk' into the housing, that along with the heat and dust from your last endeavour could well have alloed sand in and caused early retirement for the CV. Also note there seems to be encroachment of grease onto the face of the hub suggesting to me that the install may be slightly out of spec (to the way I would have it set)

 

I trust those parts include 12 new through bolts and nuts.

 

Jim, you did in fact determine that the wheel bearings are toast?


If so?????.....now the engineering fun games begin....which came first, the chicken or the egg....lol

 

Don't know if this is applicable but here goes. I have a car that drove me nuts for several years with CV boots splitting whenever I drove it hard for extended periods (120-140mph for an hour). It turned out to be heat related as the exhaust would get cherry red under that load and cause the boots to balloon up then finally fail. I had sealed the joints so well and in my case I couldn't fully shield the boot from the exhaust. So I drilled a very small hole in the backside cover and glued a piece of dense thick felt over the hole to act as a filter. That allowed for just enough breathing but I never saw any evidence of grease after that. Worked for me.

Bob S.

 

I'm really going to stick my neck on the line here and say that the CV outer doesn't look quite right? - You would "normally" see the induction hardening discoloration like shown in the attached photo? Hardness test would confirm - I would expect to see 55Rc minimum. The only reason I have chimed in on this as I have had to make a new set of valve spring seats (Lower cups) for an Enzo last year - the original factory parts were way too soft and the valve springs were wearing them away.

Jim - Its awkward to see on the other photos but is there any discoloration on any part of that CV outer? Out of interest when you get the new one have a look and compare!

Interesting....
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