what is the torque that is being used to
prevent hub/bearing failure
thanks Spike
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what is the torque that is being used to
prevent hub/bearing failure
thanks Spike
In the front? Put a 30mm socket on the biggest breaker bar you can find, then find the biggest pipe you find to put over that and then get the biggest guy you know to jump on the bar. Thats what I have been told. Hope that helps.
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Sam Rolfe
TBR Motorsports
#85 VW Rabbit
I would be careful with the "jumping on the big breaker bar technique." I've seen the threads on the axle & nut yield. They are made of steel, and are subject to all normal engineering principles. Which means that there is an optimal torque to provide the clamping force you're looking for. Once those threads yield, the clamping force will reduce!
That being said, this is what I've done for the last five years: I take a 1.5" O.D. pipe (leftover from building a rollcage), approximately 30" long. With the car in gear and a chock in front (right) or behind (left) wheel, I put the pipe over a breaker bar and carefully apply my weight until the nut stops tightening. No jumping, just a steady pressure until I can feel the nut completely tighten and then I stop.
This is well over 250 ft lbs! (I don't put all of my weight into it.) http://Forums.ImprovedTouring.com/it/smile.gif
MC
#14 ITC VW Scirocco
[This message has been edited by racer14itc (edited October 15, 2001).]
Mark has it right. I was obviously exagerating. However when you way 135lbs sometimes jumping on things will help http://Forums.ImprovedTouring.com/it/smile.gif. Ahh racing the only sport where it helps to be small. Though I do have a problem with car being anywhere from 20 to 40 lbs underweight since they added the 180lbs for the driver.
There is a school of thought that assumes that VW might have actually done the math and that the factory-spec torque is the best answer. I don't remember what it is, though... I know that some folks crank the doody out of these things, though.
A 30" bar is 2.5 feet long so (in big numbers) you would only require a force of 100 pounds at its end to provide 250 ft lbs of torque. Pressure (vs jumping) is repeatable so probably good choice and, if a person wanted to be clever, he or she could decide what kind of torque is "right" and then work backward from his/her own weight to decide how long to make the pipe.
Of course there is also the method that my brother used to employ when we first started racing (he was a pretty burly kid). Lean on it until the bolt goes soft, then back off a 1/4 turn. (KIDDING--please do not attempt this at home!)
K
Kirk,
I don't think the factory torque spec is adequate enough for a racing application. As you and most of the other experienced VW guys know, this is a weak point in the design of the car.
That all being said, I use a 30mm 1/2 drive impact socket w/ a 3/4 drive gun w/ 175psi behind it. I give it enough until I don't see the axle nut move any more. I also change out the hubs/bearings every 4-6 races just because.
I spoke w/ someone who has his hubs shot peened and he says that he has greatly increased the life of the hubs this way. I spoke to Sven Pruett in Denver, and he assured me that this was legal.
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MARRS #25 ITB Rabbit GTI
In practice, our process with the Golf II and the ITC Rabbit before it was almost exactly what racer14itc describes in his post--probably something in the range of 450 ft-lbs. My point is that I am not sure (academically, anyway) whether the additional torque is really making a difference--relative to the book spec.
Shotpeening, really good grease jammed in there under pressure, and proactive replacement of the parts concerned make sense(again, from a theoretical/logical point of view). I am hesitant to fully accept a "tighter is better" answer unless the mechanism that makes it work makes sense. The forum went down this road earlier this summer but I don't think that anyone explained why squeezing that nut down tighter would prevent (or put off) failure. Not that I wouldn't DO it... http://Forums.ImprovedTouring.com/it/smile.gif
K
Kirk,
I think the prime reason for VW front hub failure is that the factory torque spec doesn't hold the hub 'tight' enough to withstand the lateral loads put on it in a racing situation. I belive that the high lateral loads coupled w/ constant, hard acceleration 'loosen' the hub somewhat. I'm talking miniscule amounts here. The problem is, the 'shoulder' on the hub is a weak point, and since the products are not designed to withstand racing forces, I think even the slightest amount of play (or lack of support) at the hub shoulder will lead to failure, sometimes catestrophic.
I think the BFP method of torquing the axle nut mitigates this to some degree.
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MARRS #25 ITB Rabbit GTI
I've found outer nuts that are thicker with more threads. They seem to have come on 2.0L 16V Passats. I've been jumping on the breaker bar for years and NEVER had a catastrophic hub failure on the race car (unfortunately, I have on a street car, but that was probably to factory torque). My guesstimate is about 500-600 ft-lbs does the trick. I did occasionally strip the threads from the nuts (never the joint), but haven't even had that problem since discovering the thicker nuts. Before the thicker nuts, I also had some luck running doubled thin nuts (especially when I thought one was starting to give).