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Preload and Tapered Wheel Bearings

10/27/2008 1:41 AM

How do you determine the proper amount of preload to apply to tappered wheel bearings and how do you measure the amount applied?. What's the effects on drag or friction?. What setting would roll more freely without reducing bearing life.

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#1

Re: Jerrell Conway

10/27/2008 4:25 AM

Hello Jerrell Conway

Each tapered roller bearing has a Maker's rated pre-load, which is available from that bearing Maker.

You ask a very general question, and that is why you have my general answer as above, because it never pays to generalize with bearings.

Specific installations: Cars, trucks, railway wagons, locomotives and the like, also have specific requirements for each axle bearing.

For those specifics, consult the vehicle Maker, along with the bearing Maker, as they will advise you for the specific installation: Loading/RPM/Side Loading/Vibration and more.

Kind Regards....

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#3
In reply to #1

Re: Jerrell Conway

10/28/2008 3:08 AM

Sparkstation thanks for taking time to reply. This was asked without a specific because I would like to see a broadspectrum of replys. The specifics are race car wheel bearings. I asked during a bearing class and the instructor said there was to many varibels for him to answer. Car weight, speed, banking, center of gravity, traction on each wheel, and many more. There has to be a satisfactort setting that gives reliability and yet easy to duplicate.

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#2

Re: Preload and Tapered Wheel Bearings

10/27/2008 11:01 PM

Bearing adjustment is very important! Overtightening adjustable tapered roller bearings is a common error that can lead to premature failure. Tapered roller bearings on the front of RWD vehicles are never preloaded.

They're snugged up with no more than 15 to 20 ft. lbs. of torque while rotating the wheel to make sure the bearings are seated. Then the adjustment nut is loosened 1/6 to 1/4 turn, and locked in place with a new cotter pin. As a rule, end play should be about 0.001 to 0.005 inches.

On FWD cars with adjustable tapered roller rear wheel bearings, the bearing adjustment procedure is usually the same as with RWD vehicles (zero preload) - but some do require a slight preload. Ford, for example, says the rear wheel bearings on a Taurus should be lightly preloaded to 24 to 28 in. lbs. (2 ft. lbs.). A new cotter pin should be used to lock the hub nut in place. If the hub nut is a locking nut with no cotter pin, recommend a new nut.

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#4
In reply to #2

Re: Preload and Tapered Wheel Bearings

10/28/2008 3:17 AM

Thanks ed fuzzyE kedz, your imput combined with that of others should help me to put together a setting worth trying.

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#5
In reply to #4

Re: Preload and Tapered Wheel Bearings

10/28/2008 3:46 AM

The old VW's used a nut with a cinch screw on the side of it.

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#6

Re: Preload and Tapered Wheel Bearings

10/28/2008 4:34 AM

Hi,

most important is to set preload to a sufficient level so that never any impulse will loosen the contact between rollers and raceways.

There is an elastic deformation (Hertzian pressure) in the contact zone: if this is going to zero and the normal load restored quickly then the contact pressure will triple for a short time. This will overload (Brinelling) the raceways, you will not see the marks if only 10 to 30nanometers deep but noise and lifetime will degrade a lot.

So: proper amount of preload to be chosen by expected maximum load plus safety margin.

Drag and friction is in most bearings more a question of geometric accuracy: roundness of axis and housing, good quality of balls and rollers, perpendicular axial to circumferential surfaces of axis and housing, no dirt nor dust, filtered very clean oil!!!!!

RHABE

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#10
In reply to #6

Re: Preload and Tapered Wheel Bearings

11/03/2008 6:10 PM

Thanks RHABE. This is the kind of input I'm looking for.

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#7

Re: Preload and Tapered Wheel Bearings

10/28/2008 8:24 PM

Wheel bearing are slow speed bearings and as a rule are not built to very high standards because there is no need. A high quality grease and a proper hub design will let a wide margin of preloads last a long time.

There is minimal pressure and side load except when you hit a rock or chuck/pot hole. Even a 13 inch rim turns slow for bearing standards. The tire absorbs 99% of the bumps. I could be wrong but the original sets of bearings in my pickup just got new seals and repacked at 315,000 miles. Most wheel bearing fail from heat and or lack of lubrication.

Yes a race car is different. Not because they spin faster but weight costs in time and Carbon Carbon brakes get yellow hot.

Brad

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#11
In reply to #7

Re: Preload and Tapered Wheel Bearings

11/03/2008 6:24 PM

Thanks Brad.

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#8

Re: Preload and Tapered Wheel Bearings

11/02/2008 9:10 PM

Your question reminded me of a story that was attributed to Bill Jenkins, back in the sixties. Bill was racing a 65 Nova with a 327-350 in A stock, and had to race the Hemi Belvedere. One trick he used was to remove the grease seals from the front wheels, and lube the bearings with 30 weight motor oil after each run.

Just a story in an old car magazine. No way to know if true or not.

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#9
In reply to #8

Re: Preload and Tapered Wheel Bearings

11/03/2008 5:59 PM

Bob. Thanks for your input. Being familiar with Grumpy Jenkins that sounds like one of his many tricks. He was a very competitive racer and no matter how small the advantage in the end they added up to wins.

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#12
In reply to #9

Re: Preload and Tapered Wheel Bearings

11/03/2008 8:24 PM

I heard he failed tech inspection once for illeagle lightening. He had substituted a magnesiun TV antenna tube as a custum grill. Always one of my favorite racers.

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#13

Re: Preload and Tapered Wheel Bearings

03/13/2009 11:10 AM

If the bearings are back to back or front to front the bearing maker supplies a spacer which you put in between and you just have to tighten the screws or locknut completely and you get a preload that the bearing maker recommends.

But for some special applications you have to either grind the spacer to get greater pre-load or use a longer one to get less. But this is in the realm of very experienced technicians/craftsmen who have a feel and instinct for it and not for mere mortals like you and me. I have seen this done with excellent results

If the bearings are at both ends and you cannot use the spacer then it is said that you tighten the bolt/locknut till you cannot rotate the shaft, then give a quarter turn more. Again let the expert do it. I am a designer who gives a perfect layout on paper but it that guy who works with the assembly that makes my design a success. This is the symbiosis of getting a successful product out and neither can do without the other.

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Users who posted comments:

bob c (2); bwire (1); Dedaelus (1); ed fuzzyE kedz (1); Jerrell Conway (5); RHABE (1); Sparkstation (1); U V (1)

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