Steering head bearing.

[Mosin]

I am in the process of replacing my very old and worn out ball bearings with a nice new set of taper roller bearing from SRM.

When I come to slide the lower inner bearing cage down over the tube on the bottom yoke, I notice that it does not slide right to the bottom. This is because there is a slightly raised section of 6mm or so at the bottom of the tube and the bearing cage sits up against it. I am sure that when I removed the original bearing it slid right to the bottom over the top of this raised bit. Is this correct?

[chaterlea25]

Hi Mosin,
Try the other bearing, they have different size bores

John

[Mosin]

Thanks John,

I had just come to this realisation myself. But not before completely destroying the new bearing as I was trying to remove it to swap them. 
It would have been nice if SRM or Haynes had taken the time to mention that they were slightly different as they look identical to the naked eye. Especially as SRM send the bearings out with fitting instructions which doesn't bother to mention it either. Grrrrrr.

Simon

[RichardL]

Worth asking for a replacement.

Richard L.

[Craigy]

Hi guys, this is exactly the info I needed and saves me posting the question again.

No I know there’s a taper bearing alternative, could you please post part no. or size. (It’s for an A10)

Cheers Craig

[Craigy]

Or if anyone knows the bearing number (not SRM part number) that could be very handy.

Cheers

[Mosin]

Worth asking for a replacement.

Richard L.

I have been in touch with SRM this morning and they are sending me out a replacement bearing FOC. This is absolutely excellent service because at the end of the day, it was me who destroyed the original. Fair play to SRM.

Simon

[RichardL]

They have always been great with me. In the early days of my bike's restoration (2005ish).I learned on Gary and John quite a bit for advice. They were always generous with their time and extensive knowledge, even while guiding me through things that they otherwise sold as services.

Richard L.

[chaterlea25]

Hi All,
Craigy, the bearings are not a standard catalog size,, they are modified

Fair play to SRM

John

[Russ]

Craigy I realize this post is a bit old but this information may of help.  If you are fitting SRM Taper bearings to a Plunger frame you have to modify the inside of the head stock. Grind off the internal shoulder. Refer to their website if this is you.

[Swarfcut]

 I'd add a note of caution before considering modifying a Plunger Frame.

   While the standard cup and cone bearings are the same for both frames, the Plunger shoulder, being part of a substantial headstock forging is considerably wider, almost matching the width of the cup periphery. There is little internal overhang of the cup (if any) so the usual method of removal with hammer and punch is well nigh impossible as there is nothing to knock against. Original cups have an internal thread to take a screw in boss type extractor which can be hammered out, withdrawing the cup. Faced with a worn later type aftermarket cup with no internal thread, or with no extractor to hand, tack weld a bar across the cup and knock on that.

 The S/A frame headstock in comparison is a simple flared relatively thin walled tube. The bearing  locating shoulders are narrow,  so plenty of overhang on the cup to take the drift, and thus relatively straightforward to knock out. To match that on a plunger frame means removing a fair amount of material. I reckon Russ means to grind away and enlarge the centre hole of the headstock, but leave  a narrower width of locating shoulder.

 For low mileage leisure use on a Plunger bike I would stick with the original cup, cone and ball design.

 Swarfy.

 

[RDfella]

Rather than get involved with a lot of fiddly grinding, is it possible, with the old bearing out, to drill a couple of holes so a pin punch will get behind the bearing?

[Rex]

Some recommend doing just this on certain "C" range frames, but it seems a little extreme to me.
Just run a bead of weld around the inner surface of the bearing and it'll drop out when it cools.

[morris]

Rather than get involved with a lot of fiddly grinding, is it possible, with the old bearing out, to drill a couple of holes so a pin punch will get behind the bearing?

Yes. I drilled a small hole left and right both in the top and bottom. I tapped them to M5 and screwed in a short grub screw with a bit of loctite to close up the hole. The hole can then be used to push out the bearings with a longer screw.

[Rex]

But how many times would you forecast needing to push the bearings out in your lifetime?