Steering Head bearings

[CaptainScarlet]

Guys. Replacing my steering head bearings. Mine is an early 2007 Tiger -- so one of the last 955s.
Anyway, 3 things:
Lower bearing is a koyo sized at 55x25. Is that correct? It certainly doesn't want to 'slide' down the stem -- I've come to a halt with almost 20mm to go.
2. Fitting the outer part of the lower bearing. It's come to a halt about 4mm into the stem, with 2mm to go until the lip. I know I should have measured it before I removed the old one, but does it have to go all the way up to the lip?
3. Finally -- embarrassingly -- I accidentally gave the top bearing a slight bump after installing it, leaving a dip of about 2mm in the plastic (?) seal between the races. Is it now knackered, or is a small dent unlikely to do any harm?
Thanks, guys.

[CaptainScarlet]

Follow up. I found the inner race of the lower bearing in the bin and had a wee measure. Right enough, it has an internal diameter of 30mm. I found this problem working on the forks: just ordering parts for a 'cast wheel' 955 doesn't seem to always work, seems there's two varients.
So, unless any of you folk out there say different, I guess I'll have to get both parts of the lower bearing back out and start again...

[Sin_Tiger]

There do seem to be a lot of "Copy" bearings going around so the machining tolerances might not be what would be expected. Is there any chance you've inadvertently marked the stem while removing the original? I'd be tempted to remove the new bearing to inspect the stem. I'm not quite visualizing where the relative dimensions, pics might help if you can.

Girly part numbers / variations is not my field, Bixxer or someone else might be better placed to advise on that. Quite often a variation in parts sub supplier will result in another part number rather than any change in dimensions.

If you're referring to the seal on the upper bearing when you talk about a "dent", so long as the dent doesn't contact the rollers, which I don't think it will, it should be OK.

[blacktiger]

FYI, the bearing numbers for my 2002 are:-
Top bearing = 6205DDUNR
Bottom bearing = 32006JRRS
You'll also need the seal that goes under the bottom bearing as this always gets destroyed getting the old bearing off.

[CaptainScarlet]

Thank you to both Sin_Tiger and blacktiger for your input. Much appreciated.
So...another update: this afternoon, after a therapeutic tidying of the garage, I did some more measuring -- decided the 55x25 printed on the box bore no apparent relevance to the bearing on my steering stem -- put on some loud music (Porcupine Tree: 'In Absentia'), and hit it with a bigger hammer. Success.
When it comes to this mechanicing lark, confidence is key. And sometimes us home amateurs are too worried we're gonna break stuff. Anyway...
That leaves the problem of the lower bearing race (?) fitted into the headstock, and the question: is 4mm far enough up,  or does it have to go all the way up to the wee lip?

[Sin_Tiger]

Really has to go all the way in until you can no longer detect a gap between the back of the bearing and the shoulder inside the head tube. Easy way to check (if you don't have a 90 deg scriber) is bend the end of a needle or safety pin at the pointy end about 15mm from the point to 90 deg. Poke it behind the shell and feel for a gap. If there is one, keep pushing the shell in until you can't. Hammering isn't ideal, use an appropriately sized socket with a length of stud bar through the tube and a stopper like a flat bar with a hole in it or similar at the other end. Keep the thread on the stud bar well oiled to reduce the loading and warm the tube up if you can, it's not quite tropical yet 

[ghulst]

It definitely needs to go in all the way. What I have done before, is to grab a threaded stud bar and stick that through the whole frame head. The bigger the diameter that can go through, the better. Then where it comes out, put large rings on it top and bottom and complete the set with a big nut. (I have been known to stack different ring sizes to make sure the pressure is spread evenly from the nut to the largest ring. Then slowly tighten the whole thing so it slowly pushes the bearing in place. Another thing I would usually do, is to put the bearing in the freezer first and slightly heat up the head. Everything sane and with equal pressure is allowed in war and replacing head bearings.

[CaptainScarlet]

ghulst and Sin_Tiger,

Thanks both for your help. I have a sufficiently long M20 bolt, so I've ordered a couple of oversized washers to place top-n-bottom of the steering head to use as you've suggested. As for heat, I have an electric heat gun so I'll use that on the head for 15mins before bringing pressure to bear.

Watch this space for further updates!

[ghulst]

Just be careful that it goes in straight. It is easy to pull it hard and then find that it is not in straight.

[blacktiger]

ghulst and Sin_Tiger,

Thanks both for your help. I have a sufficiently long M20 bolt, so I've ordered a couple of oversized washers to place top-n-bottom of the steering head to use as you've suggested. As for heat, I have an electric heat gun so I'll use that on the head for 15mins before bringing pressure to bear.

Watch this space for further updates!

You really don't need any of that. Just grind down the old bearing outer a little so that it goes into the hole easy and use that as a drift to knock the new bearing in. Once it's started by knocking it around the full circumference and it's in a few millimetres, you can really bash it in with a lump hammer.....still using the old bearing. The way to tell it's fully home and hard against the shoulder in the headstock is that the tone it makes when you're hitting it changes.

[CaptainScarlet]

Bearings installed! Using a combination of all techniques discussed here...hammers, drifts, huge bolts and massive washers!

Next step: how tight do they need to be nipped up? Just enough to not feel any untoward movements, or a wee bit tighter than that? Maybe put the fork legs back in then tighten everything up?

[blacktiger]

Next step: how tight do they need to be nipped up? Just enough to not feel any untoward movements, or a wee bit tighter than that? Maybe put the fork legs back in then tighten everything up?

Adjusting Taper Rollers is a bit of a black art. Until you get some experience it's a bit of trial and error. They need to have absolutely no play but the handle bars need to be able to flop from side to side without resistance. The skill comes when you appreciate that doing up the top nut (the nut on top of the top yoke) will clamp down on the bearings a bit. Good luck and be patient.

[London_Phil]

Fitted taper rollers to my XC during the lockdown. Have adjusted it to have zero play with as close to zero drag as possible.
I haven't been out on it yet, but I would expect it to bed in a little and require adjustment again after a while. It goes from floppy to binding in a very small adjustment, unlike the ball roller original, but there was definite notches on the cups when the old ones were removed.

[Sin_Tiger]

  rollers last a lot longer due to the larger contact surfaces but are of course considerably more expensive to manufacture 

[blacktiger]

rollers last a lot longer due to the larger contact surfaces but are of course considerably more expensive to manufacture 

I have to disagree with you about rollers lasting longer. In my experience with the Angular Contact Ball bearings in the 800s, they have lasted 40K miles on my first one and my second, current 800, is on 32000 miles and they're still going strong. I had to replace the tapers on the Girly every 30K. The AC bearings also seem to be less critical on adjustment too.