Hi,

Am aware that people replace the bearings in their Shimano HT2 cups although the replacement bearings are 7mm wide not 6mm as per shimano.

To my mind this means that the non-diveside crank arm will sit 2mm further out than designed for and the splines won’t be fully engaged?

Has anyone had issue with this or does everything seem to work ok?

shimano ht2 bearings have an 1mm external seal which makes up the difference, what isn’t compatible is the top hat.

Top hat isn’t used & bearings sit directly on the axle.
Works OK.

Top hat isn’t used & bearings sit directly on the axle.
Works OK.

depends on what bearings you use.

Was thinking of using 6805’s from the local supplier which are 25mmx35mmx7mm whilst Shimano use 25mmx37mmx6mm.

Although I have seen 25mmx37mmx6mm they are very,very expensive.

Shimano axle is 24mm so tophot is used to shim the 1mm needed (think Jonny Panic is referring to the BETD ones).

Klunk – not sure what you’re saying, is it pull the old ones, drop in new bearings, omit the 1mm seal and use the tophat to shim for the axle?

the top hat from a shimano cannot be used “as is” with traditional cartridge bearings its designed to work with the external seal of the one sided ht2 bearing.

25mmx37mmx6mm is not needed, the shimano 6mm + 1mm external seal is the same as a 7mm cartridge.

You can sand the lip off the top hat flange and then everything fits fine. 6805 bearing + seal + top hat. And you also have the added bonus of double sealing – the bearing seals and the Shimano seal.

I’ve haven’t experienced any problems with the extra width and I’ve been using this technique for a few years now.

Much prefer using top hats rather than running the axle direct onto the bearing.

Think I know what Entonox is getting at but still can’t visualise what you’re saying, Klunk.

Take out 6mm thick bearing with 1mm external seal and top hat.

Replace with 7mm thick bearing but not the external seal?

What do I do with the tophat? I assume sand it like Entonox says, its got to go back in cos the axle of the cranks can’t run directly on the bearing surface on 6805s.

Think I may have to open one up and figure it out myself, I’m being pretty thick tonight.

Thanks anyway.

I had a problem with this using the betd bearings – wrote off a crankset in the way you describe – splines not engaged (xtr :(, but a bit past it so no huge loss).

Given that many people do replace the bearings no sweat I’m sure it was something I did wrong, not sure what though. It seemed that the bearing plus seal was too wide, so maybe I hadn’t quite pressed it in correctly. I could tell it wasn’t quite right, but rode it anyhow which wasn’t the most intelligent thing to do. It was also an xtr from a few years back, not sure if it could have been a slightly different size shell.

Anyhow, it sounds like you know what to look out for with respect to seating the bearing properly and engaging the cranks, so I’m sure you’ll get it right.

Cursed now Garry, likely that the whole bike will disintegrate into component parts at the farthest distance from home. 😀

Anybody else find that standard 6805’s are really tight on the axle?

I suspect the Shimano bearings are ever so slightly (0.0005″ish) oversize on the ID – sneaky.

I made some new top-hats from nylon. Next time I shall just buy new shells.

What do I do with the tophat? I assume sand it like Entonox says, its got to go back in cos the axle of the cranks can’t run directly on the bearing surface on 6805s.

you either file/sand it down or get a replacement they only cost about £2. But if you haven’t got a spares box with more 5 knackered sets you could take some from your not a proper mountain biker ;). You will have to be careful removing the top hats as they are very brittle, i’ve found steaming them in a kettle spout to soften up the plastic a bit helps a lot.

oh and by the way these are the best replacement bearings bar none.

Yeah put the top hat back on.
You have to sand the lip off the top hat flange otherwise the axle will not fit through. Maybe that’s why Betamax’s were ‘really tight‘ ?

I’ve had good mileage (6 months to a year depending) out of £2 ebay budget bearings. Choice is yours.

think Jonny Panic is referring to the BETD ones).

Yep. The Enduro Seals sets from BETD.

Thanks lads, just pulled a couple open and have it all straight in my head now and can see why I need to sand a bit off the topcap to get that mm back.

As an aside its always the non drive side that rusts up and dies so I have ended up with a few good drive sides – just pushed the bearing out of a drive side and pressed it into a non drive side cup so can get my big bike back on the road tomorrow. 😀

It’s the top of the hat you need to sand. I think I may have confused the issue by using the word flange.

Can you see the lip that runs around the edge?

The bit at the bottom of your picture?

Edit: Of course it’s that bit (slaps forehead), that bit seats behind a 6mm thick bearing but would constrict when in a 7mm bearing.

Do you insert the rubber shield as per normal?

To my mind this whole replacement process will leave the splines on the cranks 2mm short compared to if 6mm wide shimano bearings were used, does it make no real difference?

Why do shomano use bearings sealed on 1 side only?

No idea, perhaps its to give room for the rubber seal.

Leave the seal out as you guessed. Older ones never had that seal anyway, and then it was simple swap of bearings.

http://www.youtube.com/watch?v=A1Lw67eTU30&feature=player_embedded

The original XT hollowtech II BBs used standard 6805 bearings and different sealing. I believe they changed designs to make it troublesome to swap out the bearings hence the bespoke ones they use now. And maybe they were lasting too long? – two levels of sealing rather than the ‘open’ bearing and one seal they use now.

I don’t know if you’ve noticed but that ‘lip’ clips into a groove on the inner ring of the shimano bearing. 6805 bearings do not have this groove so that’s why it needs removing with a light sanding. If you don’t remove it you can’t get the axle through.

I keep the seals in – double sealing.
It makes no difference in the width as the top hat has a shoulder that fits against the inner edge of the bearing. Leaving the seals out creates a gap. I’ve never had a spline problem with the extra 2mm. The safety locking pin on the crank arm still easily engages into the hole on the axle.

Cheers.

some pics and some instructions would be good 😆
like

Thanks Entonox – All becomes clear.