You don't need to be an 'investor' to invest in Singletrack: 6 days left: 95% of target - Find out more
Anyone know why replacement bearings for Hollowtech 2 bottom brackets are offered in different widths, ie 37x25x6 and 37x25x7? Just bought replacement 37x 25x 7mm bearings, but the ones that came out of the cups were 6mm thick. Checked the depth of the actual cup bore, and its 7.75mm , or therabouts.
I know i need to allow for the thickness of the plastic dust shield, so 7mm sounds about right to me.
Is this is a case of a previous owner putting the wrong replacements in, or have i dropped a bollock and bought the wrong bearings?
Me wanna know this too. Hate throwing hard plastic away
Road ones are wider than mtb ones
I'd be more interested in how you got both sets of bearings out of the cups.
The non-drive side ones are normally the first to go, as they don't have the chainset to protect them from mud and water, but they are almost impossible to remove, due to the shape of the cup, on that side.
Or have that changed the design?
You can ditch the Shimano bearings and the tophat bit and run the cranks on the bearing directly. Enduro do a kit with bearings & covers included.
Impossible? Nope, took mine out in 5 mins today, did need a second pair of hands and a set of engineering parallels though. Oh, and ,using my new revised method, a block of wood.
So, just place the cup bearing side down on a block of soft pine. I used the crap wood that comes in stillages and pallets. Position this block over the bench leg so that your impact is directly going into something with no flex. Very important , it prevents bouncing .
Using a small screwdriver, about 1/4" across the flat, carefully position the blade into the wee gap between bearing and cup wall. Be careful not to scratch it, but its not the end of the world if you do, you can always tart it up later with a bit of 1200 grit wet n dry.
Give it a solid tap, not a big one ,on the OUTER race, just enough to get it moving.
Rotate cup 180 degrees and do it again. Be careful not to move it too much at a time, the aim is to keep it as close to level as possible. Hit north south like this until bearing is bottomed out against the block of pine.
Here comes the tricky bit where an extra pair of hands is useful. Place the cups on two parallels , leaving enough of a gap for the bearing to fall out . There is not much room at all, so here is where the extra pair of hands comes in. Position the parallels north south in relation to you, again over a bench leg. Get your handy mate to press the cup into the parallels hard as he can. This is to stop them bouncing in the next bit.
Tap the bearing until you feel a lip. This is the bearing protruding slightly from the cup. You want this, this makes the next bit much much easier. Place the lip hard up against the BACK (south) parallel. Look at the distance between cup and parallel. Try and leave a slightly bigger gap between the bearing and the north paralle l for the bearing to exit. Give the bearing a tap, rotating the cup 180 degrees each time. The idea is to get a lip all around the bearing. Once you have that, just rotate and give it a tap step by step til the bearing falls out.
Sounds rough cos it is, but like I said i got both bearings out in about 5 mins today once I figured out the method and collected all the bits needed. Very minimal damage caused , a quick 10 second rub with the wet n dry sorted any bruising out.
Before you put your new bearings in, give the bearing cup bore a quick rub with wet n dry, i wet mine with plusgas . Dont take much out, just give it a quick 10 second polish.
I replaced old knackered ones with new bearings and reassembled with two blocks of soft wood and a hammer. No damage caused, bearings were silky smooth afterwards.
Problem is, 7mm bearings are too wide for MOUNTAIN cups, so they had to come out again. Again, same method, 5 mins, no damage.
Gotta buy 37x 25x 6 mm bearings now.
This is by no means the best ,absolute gospel method , but it works, and it was worth trying it on cheap deore cups.
@johnnymarone
From memory of the time I tried - a couple years ago) I used a similar technique for one cup (drive side,vi think) but the shape of the cups meant that it wasn't possible for the other side.
Did you notice any difference between the two cups?
This is by no means the best ,absolute gospel method , but it works, and it was worth trying it on cheap deore cups.
Where do you get bearings for <£6 each? 6805N-2RS ?
I just bought 2x Deore BB's but to be fair that was to make up £10 off or free delivery and still have the old cups.
On the pair of cups I have here, SM-BB51, the cups look identical other than one is a RH thread and the other is a LH thread. There is a difference in length of the threaded diameter, the cup marked R which confusingly is the LH threaded one,being longer by a few mm. Without taking a calipers to them, I would say that is the only difference between the two cups.
There appears to be no difference in shape, hole size,etc.
The initial bearings were 25x37x7, which would appear to be a standard size. They were £6.99 for a pair. Had a mate who used to make bearings for INA bearings check em out and he said they were tidy enough for the price.
They were from mcrbikes on ebay. Free p+p too, quick delivery .
They didnt fit my cups so ordered a pair of 25x37x6 at £8.99 for a pair, from the same seller. Still waiting on those, but I only ordered them last night/early hours so its still early days.
Hope that helps.
so ordered a pair of 25x37x6 at £8.99 for a pair, from the same seller.
That's about what I found but a new BB is only £12 or so if you shop around... and the Saint ones can usually be got for £15 (I ended up taking my hope BB off and replacing with Saint as it was less than 1/2 the cost of new Hope bearings)
Yeah I know theyre cheap enough to replace, the rationale behind it is that I have had to replace quite a few external BB's over the years, and the only issue ever is the bearings. By keeping a spare set of bearings handy, in an emergency I can whip the old ones out and put new ones in in a fraction of the time it takes me to go down the bike shop and buy a new BB.
Yes, I could keep spare BB handy too, but I can sort my cups out in work in 5 mins so why bother? Plus I love messing around with bikes, breaks the monotony of my job.
On a side note, the absolute best external BB i had was a Dura ace one on my Genesis Vapour. And, co incidentally, I had cup and cone bearings on my old XT hubs, and the best balls I ever had in there were Dura ace stainless. They lasted ages.
Plus I love messing around with bikes, breaks the monotony of my job.
Good enough reason 😉
I'm pretty bad for fixing stuff just cos you can.... so I end up having to pinch myself when it's going to cost more than the replacement cost.
24x37x7mm if you want to run the bearings without the top hat. That's the size if the Enduro kit ones.
Just curious @sv, any benefit to getting rid of the top hat set-up? Also how much are the enduro kits? Their website doesnt load properly for me on my device.
@johnnymarone the used to be quite brittle and easily damaged when taking them out. Think about £20 for the kit although that was a while ago!
@johnymarone - sounds like they've changed them, then.
Will have another look, next time I need to replace mine.
New bearings, ordered, delivered and fitted.
Bearing cups run smooth as silk again. Easy fix and cheaper than buying new. Time will tell if these bearings are any good, but at £9 a pair I'm not complaining.