Replacing front bearings

[Kwikasfuki]

Seems that every 20k my front bearings are shot. I replaced them over the weekend but wasn't too happy with how I did them, so am intending to replace them again.

There isn't much room on the bearing to hit against, so I got a long flat screwdriver, pushed the spacer out of the way and hammered it out. Unfortunately I did damage the spacer a little, but nothing that wasn't fixable with a file.

When inserting the bearings, I did freeze them for about an hour before putting them in. One side went in relatively easy, but I had to use a 27mm socket get it flush. The other side was a pain, and whilst I avoided the inner ring, I did manage to scuff the the seal between the two rings. I also noticed that the axle got progressively harder to remove as the bearings went in (it was a pain to get the wheel off the bike as well as the axle refused to move once it have been unthreaded from the opposite bolt). As I'm not confident that I did it right first time I'm going to do them again.

This time I will put the bearings in the freezer for longer, but am also thinking of using a heat gun to warm up the bearing housing. Any ideas at what temperature I want to do this at? Also, what size socket will match the diameter of the bearing, but not get stuck in the housing.

Alternatively, there is the chance I've done it right first time. Is there an easy way of checking? Both bearings turn, just that one turns more easily than the other. It could be I'm just being paranoid.

Of course, I could get a mechanic to do it, but where would be the fun in that? 

[lather]

When I did this with a different bike I put the bearibgs in the freezer overnight and they literally dropped in.  The wheel was likely pretty warm at the time maybe 90F If you use a heat gun to heat the wheel I would thibnk 120F should be plenty. If you cannot pull the axle out by hand with the weight of the wheel supported I would think something is wrong.

[Kwikasfuki]

If you cannot pull the axle out by hand with the weight of the wheel supported I would think something is wrong.

Every time I've had the tyre changed, they've had to hammer the axle out (gently) from the opposite side with a brace. It seems the deeper the bearings go in, the harder the axle is to remove

[Breaker19]

Every time I've had the tyre changed, they've had to hammer the axle out (gently) from the opposite side with a brace. It seems the deeper the bearings go in, the harder the axle is to remove

That's not terribly uncommon; sometimes they get a burr from the washer behind the nut, or it's just some corrosion built up on the axle itself. Whenever I yank a front or rear tire, I clean and sand the axle with like 400 or 600 grit wet/dry and some WD40 as a lubricant; then, thoroughly clean it again and coat with a very light amount of never seize. When I do that, the axles nearly fly out with a light tap on the thread end with my dead blow hammer.

As for bearings, there's that flange inside that goes around the spacer to keep it somewhat centered when installing. You just have to get a small diameter drift from the other side and carefully, rap the bearing out. I've never had a significant problem getting them out or back in on any bike... yet... lol But I have ground the drift down to a wedge-shape to get a purchase on the bearing. Gotta be really careful with that however, because then it can act as a chisel on the aluminum of the wheel as the bearing moves outward (yea, been there, done that too)

[ZG]

If you're pulling your bearings out anyways, take that opportunity to get your wheels powder coated black! 

[B.D.F.]

The key to installing bearings is to only drive the race that is the press fit; on the front wheel of a motorcycle, only drive the bearing in by tapping or pressing (tapping is preferred) on the outer race. You can use just about anything that is a hard metal (brass, steel, bronze) and is smaller than the bearing OD (so it does not get stuck in or damage the wheel bearing mounting surface in the wheel), and large enough to contact only the outer race. The size isn't critical and there is probably a 1/8" to 3/16" range of round objects that would work with a socket being the most commonly used.

It is really critical that the bearing is driven into the wheel straight. Any rocking or cocking of the bearing will result in catching a 'lip' on the inside of the wheel, stop the assembly and damage the wheel bearing diameter.

Cooling the bearing shrinks it and heating the wheel will expand that. If taken to the extreme, this is called a shrink fit and it is a one- way assembly method that cannot ever be taken apart without destroying one part, usually the outer diameter. Heat / cold can help install bearings but it is not necessary as they are a light press fit.

Technical reason: Steel (generic type) expands (or shrinks) at the rate of 6 1/2 millionths of an inch per inch per degree F. Aluminum (generic alloy) expands / shrinks at the rate of 13 millionths of an inch per inch per degree F. So if the bearing is 2 1/2" in diameter, and you bring its temp. down 50 degrees F, it will shrink by (2.5" X .0000065" X 50 degrees) is 0.000813" or just under a thousandth of an inch. If you heat the wheel hub by 200 degrees F, the expansion will be (2.5" X 0.0000130 X 250 degrees) 0.008125" or just over 8 thousandths of an inch. As you can see, heating the aluminum wheel is far more effective at changing relative size than cooling the steel bearing. The reasons are that the aluminum expands at double the rate of steel (approx.) and you can raise the temp. a LOT more from room temp. than you can cool the bearing.

Brian

Seems that every 20k my front bearings are shot. I replaced them over the weekend but wasn't too happy with how I did them, so am intending to replace them again.

<snip>

This time I will put the bearings in the freezer for longer, but am also thinking of using a heat gun to warm up the bearing housing. Any ideas at what temperature I want to do this at? Also, what size socket will match the diameter of the bearing, but not get stuck in the housing.

Alternatively, there is the chance I've done it right first time. Is there an easy way of checking? Both bearings turn, just that one turns more easily than the other. It could be I'm just being paranoid.

Of course, I could get a mechanic to do it, but where would be the fun in that? 

[VirginiaJim]

When I did this with a different bike I put the bearibgs in the freezer overnight and they literally dropped in.  The wheel was likely pretty warm at the time maybe 90F If you use a heat gun to heat the wheel I would thibnk 120F should be plenty. If you cannot pull the axle out by hand with the weight of the wheel supported I would think something is wrong.

Got a cold, Lather?

[Shoe]

Has anyone ever used a hot plate to heat the wheel before dropping the bearing in? Just wondering.

[MAN OF BLUES]

Has anyone ever used a hot plate to heat the wheel before dropping the bearing in? Just wondering.

Usually I would reply to that question with "if you have to ask......don't try it."

but I'll just say it simply is not suggested, or needed.
Chilling the bearing has merit, but there is such a small interference in the bearing bore fit, it isn't necessary.
I coat the o.d. of the bearings sparingly with a smear of anti seize.

[lather]

Got a cold, Lather?

No I am feeling well, other than the usual lack of sleep. The frequent typos in my posts however I blame on fat fingers or overly close keys. If they would put the keys about a half inch apart I could do better.

[Kwikasfuki]

Found a socket that fits the outer brace nicely whilst not big enough to get stuck in the housing.

My bike has done 45k now and this is the second time I'm replacing the bearings (last time was at 22k). I'd had thought the OEM bearings should last longer.

Now got SKF bearings which I'm informed are the Rolls Royce of bearings. We shall see ...

[VirginiaJim]

Could you tell us the bearing number?

I'm wondering why some need bearings and some don't.  I've got 47k on my bike and they're fine.  I've checked them at every tire change and they still feel good.  Smooth as silk, unlike my C10 which did eat bearings.

[Kwikasfuki]

I will do when i get home tonight. Right now they are in the freezer!

[VirginiaJim]

At least they won't go bad...

[Kwikasfuki]

Sorry Jim, forgot to make a note of the bearing model. Will get it later

Put the bearings in today. I have a question: how flush should the spacer be between the bearings? When I originally took the bearings off, it wasn't flush at all. After I messed up bearing install no2, I realised I had it quite flush. I asked my dealer and he stated that it should be flush, but not overly so. So that's how its done on bearing no3. To move spacer out of the way now requires a little bit of force.

This might should like a stupid question after I've replaced the bearings, but what's the relationship between the wheel, bearing, and axle? I assume the bearing functions once under load in conjunction with the axle?

Some pics of the bearing and spacer. If the spacer is moved to the side, only a few mm of the inner brace will be visible. I used a flat blade screwdriver to knock them out as there was no chance of ever hitting the housing.

To get the bearing moving, it was easier to tap it in a clockwise direction rather than alternate sides.





And the socket size to hammer the bearing in. Fits perfectly onto the outer brace and small enough not to get stuck in the housing

[VirginiaJim]

Sorry Jim, forgot to make a note of the bearing model. Will get it later

No tea for you! 

[Son of Pappy]

When they go bad, they feel, well, really bad.  Jim, if ya ever get above Prius speed ya may notice, never mind, at those speeds they should be good for another 150000 miles

[VirginiaJim]

When they go bad, they feel, well, really bad.  Jim, if ya ever get above Prius speed ya may notice, never mind, at those speeds they should be good for another 150000 miles

Actually the fronts went out about 175k and they were a real PITA to switch out.  So much in fact, I'll never do them again if the need arises.  They glue themselves to the carrier.  At 250k, they're still sounding good.

[Kwikasfuki]

No tea for you! 

How about now? 

[VirginiaJim]

Tea time!  Thanks.