RichieC
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| posted on 22/11/05 at 04:34 PM |
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Front Wheel Bearings - How Tight?
Hi all,
Just fitted new bearings to my Sierra uprights.
Torqued up to 340 nm, as a gauge, how tight are the hubs to rotate ? Certainly tighter than other cars Ive done.
I appreciate this was just byhand with no wheel or anything on, but I was suprised how tight they felt, but I guess that may well slacken off as they
bed in.
[Edited on 22/11/05 by RichieC]
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DarrenW
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| posted on 22/11/05 at 04:53 PM |
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i was well surprised how hard my huns were to ratate after fitting mine. This is well threaded and similar experiences have been had by most. After
putting wheel on they felt a bit better. After 2 first drives (no more than 400 yards) they were a lot better. Dont worry, the bearings wont be
damaged. It sthe way they are. My guess is that some aftermarket bearings may be sized slightly different to OEM spec. They do bed in OK.
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RichieC
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| posted on 22/11/05 at 04:55 PM |
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Lovely jubbly, I suspected they would, just seemed a good deal toiter (like a tiger) than I expected.
Cheers
Rich
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DarrenW
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| posted on 22/11/05 at 05:02 PM |
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Yeah. Cant remember exact reason why they are OK but it is something to do with the outer races being squeezed but seeing as they are parallel
bearings they dont get deformed to the point where they will fail. Once bedded in they loosen up lovely. Also when new the grease wont be distrubuted
fully etc etc.
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RichieC
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| posted on 22/11/05 at 05:04 PM |
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Yeh, thats what I was hoping for. I suppose the crazy torque these things are done to is bound to squeeze it all up and it will take a little time to
all settle down and grease to start working.
Thanks again
Rich
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JoelP
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| posted on 22/11/05 at 06:50 PM |
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my cortina ones i did hand tight, beacuse thats what they were when i took them off. Would the sierra be so much different? I literally put a socket
over the nut, tightened it til my hand slipped on the grease, then backed it off to the last hole for the split pin.
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RichieC
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| posted on 22/11/05 at 06:51 PM |
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I cant see them being that different, the Sierra ones are 320-350NM I think, thats some torque
Rich
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andyps
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| posted on 22/11/05 at 09:39 PM |
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Are the Sierra bearings tapered roller?, in which case overtightening can have pretty disastrous consequences.
Andy
An expert is someone who knows more and more about less and less
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RichieC
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| posted on 22/11/05 at 09:41 PM |
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Yes they are - theyre not overtightened though, theyre torqued up to spec
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NS Dev
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| posted on 23/11/05 at 09:48 AM |
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Ahhhhhhhh goodness me!
READ THIS - GUIDE TO SIERRA AND CORTINA HUBS!!!!!!!
SIERRA HUB!!!
Has 2 (identical) taper roller bearings, and a split hub that goes through them. The hub is VERY accurately machined so that when the two halves are
tightened together, they give the right preload on the taper roller bearings. You are relying on Ford's machining and bearing
manufacturer's attention to Ford's prescribed tolerances to set the bearing preload. The torque on the nut is irrelevant to the bearing
preload. If that torque was applied to the bearings they would be destroyed!!! The high torque value is needed because a big thread is needed to
retain the hub safely under high cornering forces etc and to have a big safety margin, and that big thread then needs a MASSIVE torque value in order
to elastically deform it enough to keep the nut tight.
CORTINA HUB:
This is totally different, being the "old fashioned" type using 2 different bearings, on a stepped stub axle, and with the bearing preload
manually set by the combined adjuster and retaining nut. On this the nut is nipped up to seat the bearings, then backed off a tad to keep a slight
preload. Then a seperate method of locking the nut in position is applied.
So there you go, TOTALLY different types of hub, so don't try and compare the two!
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NS Dev
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| posted on 23/11/05 at 09:48 AM |
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PS, yes sierra hubs are usually tight when assembled, don't worry!
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DarrenW
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| posted on 23/11/05 at 09:53 AM |
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The sierra bearings are not the usual tapered type. The cortine ones described above are secured with a split pin through a castleated retainer. The
Sierra are different to that in that the main outerraces are parallel and secured by high torque with nyloc nut. Leave them hand tight and they will
soon fall out! - not nice.
Follow manufacturers instructions for fitting and you cant go wrong. If anyone is interested the main general differences between OEM and aftermarket
grades are;
1. OEM parts tend to be made on fully approved detailed production processes with auto checking and tight change control.
2. Ball grades on OEM are higher - meaning they are sized more accurately to reduce noise and improve durability.
3. OEM control Cpk's to a tight level - both internal processes and supplier processes.
4. Aftermarket tend to be manual assembly, not as tightly controlled. General tolerances are looser to allow more parts to pass through.
I have seen OEM process rejects being used as aftermarket. This sounds bad but in reality it actually means the aftermarket parts are a very high
grade.
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RichieC
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| posted on 23/11/05 at 11:03 AM |
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quote:
Originally posted by NS Dev
PS, yes sierra hubs are usually tight when assembled, don't worry!
Cheers Dev (did you get the msg I sent about wheel studs and nuts?)
Rgds
Rich
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NS Dev
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| posted on 23/11/05 at 11:25 AM |
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Nothing unusual about the sierra taper roller bearings.
They are perfectly normal ones just like the cortina ones, just used in a different way!
The outer races of the sierra and cortina ones both press (or drift) into their housings, the sierra ones are just the same inside and out
that's all.
Difference is the sierra ones are not adjustable preload, tighten the nut up and they are set.
PS Working for Timken gives me an interesting insight into the issues you mention Darren!!
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andyps
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| posted on 23/11/05 at 09:52 PM |
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It is as an ex Timken employee that I asked my question - I couldn't remember what type were in the sierra and it was too cold to go outside and
look in the manual!
The Sierra type require pretty close manufacturing tolerances for the bearing stand dimensions and I would advise against using cheap replacements
which may not be made to such tolerances.
Andy
An expert is someone who knows more and more about less and less
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NS Dev
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| posted on 23/11/05 at 10:47 PM |
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quote:
Originally posted by andyps
It is as an ex Timken employee that I asked my question - I couldn't remember what type were in the sierra and it was too cold to go outside and
look in the manual!
The Sierra type require pretty close manufacturing tolerances for the bearing stand dimensions and I would advise against using cheap replacements
which may not be made to such tolerances.
That's exactly it, the stand dimension and the tolerance on the hub halves actually sets the bearing preload (as you know!) in the sierra
application.
It's not possible to overcompress the bearing by overtightening the nut as you are just pulling the hub halves together against a machined
shoulder on them. if the bearing stack height is too great though of the hub shoulder has retreated somehow then the bearings will be over preloaded
and will almost certainly fail.
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DarrenW
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| posted on 24/11/05 at 09:34 AM |
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The Ford OEM are likely to be NTN, SKF, GKN, Timken or something like that. Id dare bet the OEM outer race thickness tolerance is something like
+0.015/-0.035mm. Aftermarket will be along the lines of +0.02/-0.05. You also have to bare in mind the hub machining tolerances and assembly press
forces (inc method od applyingtorque to the bolt - believe me a black art in its own right).
Once the hubs are 10years + old, maybe being subjected to a rough arsed bearing change in the past, almostcertainly been derusted and coated as part
of our donor prep then it is safe to assume the hubs will be out of tolerance. New bearings will not be pressed in using same type of tooling as Ford
(definitely not using a highly engineered repeatable process). Couple this to the fact we will be using a torque wrench that may not have seen light
for a few years, certainly not calibrated every 6 months and definitely not repeatable (speed of wrench rotation can even affect what torque is
applied) then the use of any aftermarket wheel bearings is actually not really a bad idea. By all means use Ford dealer parts but imho a waste of
money.
Oh - also forgot to factor in that all important durability spec. Ford OEM assemblies are probs specced at 60K miles per life (or whatever the
warranty period is), the hub unit will be tested to at least 3 lives, and probably onto 6 to understand the failure characteristics. How long will it
take us to get to 30K miles, after which we will consider a bearing change to be routine maintenance.
Bottom line - nowt to worry about.
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andyps
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| posted on 25/11/05 at 12:28 PM |
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The originals were almost certainly Timken, there will be plenty of reasonably priced wheel bearing kits which will use the Timken bearings without
having to go to Ford. At least if you get these any other wear will have less consequence for the eventual fit.
Halfords kits used to be assembled by BRT Bearings (and may still be) who only use quality products, and used Timken whenever the price was acceptable
(not necessarily the cheapest). I would be surprised if they have changed their policy.
Andy
An expert is someone who knows more and more about less and less
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