Mega Exo BB replacement

paulbnix

I have recently noticed some clicky/clunky noise when pedalling.
The bike is a Boardman road comp and the BB is FSA Mega Exo.
I removed the chanset and the bearings and it looks like the left hand one is shot as its full of muddy looking grease and is rough compared with the rh side.
I see that CRC have the SRAM GXP Team BB Cups for about £25 http://www.chainreactioncycles.com/Models.aspx?ModelID=55194&_$ja=tsid:46412|cgn:SRAM+-+Bottom+Brackets|cn:Chain+Reaction-UK-PLA-PLA-All-DT-SE|kw:199313UK_GXP+Team+BB+Cups&gclid=CPmaweOO0LgCFRMRtAod_loAtA
Is this a good choice?

Instead of replacing the whole thing can the bearing be removed from the threaded section as I only need one? Is so how?

desweller

GXP is not compatible with Mega Exo. HTII is though; I have an el-cheapo ceramic HTII BB on mine for a FSA chainset at the moment.

You can only get the cups as a pair.

turnerjohn

get a shimano mega exo BB....bearings are better....by DA one refuses to die !

jonnym5

Double check the part number on the BB itself. A Fsa Omega chainset with a BB4000 19mm BB will not work with a shimano crank.

Any FSA Cranks using a 24mm spindle seem to work fine with shimano external cups. They do require a slight tap to get over the small steps on the axle. They last a lot longer in my experience.

paulbnix

I have taken a couple of pictures on the BB. Do you think Shimano HT2 will be compatible?

Ouija

With the exception of GXP BB's, where the right hand side expects a 24mm axle and the left a 22mm, most 24mm bottom brackets are interchangeable. Shimano holds the copyright to the word "Hollowtech II", but not the design, so most companies can make hollowtech II copies but are forced to call them by another name, such as MegaExo for example. As long as you don't mix up the road and MTB variety you are all right (and even then the two different types can be interchangeable if you use the right amount of spacers).

paulbnix

So could this be a valid replacement?
http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_919007_langId_-1_categoryId_210159

hstiles

That would be a good replacement. Slightly cheaper from Merlin Cycles

http://www.merlincycles.com/bike-shop/road-parts/transmission/bottom-brackets/ultegra-6700-hollowtech-ii-bottom-bracket.html

paulbnix

Sorry to keep harping on about this but my understanding is that the FSA Mega Exo axel, although 24mm, is slightly larger than the Shimano Hollowtech 2 axel but it can be forced through a Hollowtech 2 BB.

Am I correct?

The reason I say this is because I asked Hope if their BB would fit and they replied no because of the size difference - maybe theirs is less tolerant.

Monty Dog

There are different models of MegaExo BB - the carbon cranks use a narrower bearing and aren't compatible with HT2 according to FSA. If the crank is Gossamer, then HT2 works fine IME. It's down to the length of the spindle, not the diameter (unless Taiwanese millimeters are different from Japanese?)

paulbnix

Thanks Monty - my crank is FSA Gossamer so I will go ahead and try the Ultegra 6700.

Ouija

Monty Dog wrote:

There are different models of MegaExo BB - the carbon cranks use a narrower bearing and aren't compatible with HT2 according to FSA. If the crank is Gossamer, then HT2 works fine IME. It's down to the length of the spindle, not the diameter (unless Taiwanese millimeters are different from Japanese?)

I imagine those carbon cranks could be made to work with Shimano MTB HT2 cups, which are narrower than the road versions (the road has wide cups and narrow axle sheaf, the mtb has narrow cups and wide sheaf). You'd just have to omit the longer sheaf or swap it for a shorter one.

To the OP:
Why buy a new bottom bracket at all? Simply buy some new sealed bearings for the bottom bracket you've got. Simply push the bearing rings out and measure the inside, outside and thickness and buy some new ones off ebay for less than a fiver (if you don't go to specialized bike stores and purchase from a general online hardware shop you can buy packs of up to six for less than a tenner).

And if you do want a whole new bottom bracket, don't get it from Halfords, you can buy Shimano ones off ebay shops for less that £20.

paulbnix

Just replacing the bearing was one of the questions in my original post. I did try hitting the exposed part of the bearing with the end of a screw driver but could detect no movement of the bearing.
Do you have any further info on how I remove the bearing from the shell?

I am looking for Evans to price match the Ultegra for 19.99 and I can pick that up rather than waiting for the post.
I will continue trying to remove the old bearing because I will then have a replacement for the next time it happens.

Ouija

Some bottom brackets (shimano, for instance) have a design that makes getting the bearings out almost impossible (forcing you to buy whole new bottom brackets every time). A better solution is to buy one which you know you can get the bearings out of, such as these trailbright ones, and then simply do that in the future.

paulbnix

Thanks for that I have ordered a stainless steel set from Trailbright.

Ouija

Those take 25x37x7mm bearings. You can pick up packs of ten for a tenner....

The trick to getting the bearings out isn't to try and gauge them out from the front but to leave each cup in the frame for grip and simply pushing something that's wider than 24mm wide against the inside back of the cup and giving it a tap with a hammer (i actually use a head tube removal tube). The bearing and front seal usually jumps straight out of the cup.

desweller

I found replacement bearings very difficult to source. It's difficult to justify when a new BB costs less than £25.

On the FSA BB you'll have a bit of a job stripping it without damaging the top hat bush and the other seals. If you've got water ingress you'll want to replace those seals anyway, at which point it becomes uneconomical (not that it stopped me, but hey). If you do go this route then it's worth sourcing some silicone grease for lubricating the seal interfaces.

onbike 1939

Rather than face all of this faffing around every year (which is about right with these FSA bearings) and the associated costs, you could of course just chuck the whole thing and buy a conventional square-taper BB and chain-set. No drama, no yearly replacement of bearings but year after year of undisturbed use. I've worked on two bikes in the past week and each have had the same square-taper BB bearings for the past fourteen years.

Ouija

onbike 1939 wrote:

Rather than face all of this faffing around every year (which is about right with these FSA bearings) and the associated costs, you could have course just chuck the whole thing and buy a conventional square-taper BB and chain-set. No drama, no yearly replacement of bearings but year after year of undisturbed use. I've worked on two bikes in the past week and each have had the same square-taper BB bearings for the past fourteen years.

God. I wish i had your experience with square taper bottom brackets. I must of gone through 10 of them in under 2 years. That's why i switched to HT2 (that and the substantial drop in weight). The HT2's haven't proven to be any more or less reliable, as far as i can see, especially the Shimano low end ones (which just die after a couple of months, even a couple of weeks in some instances), but the bearings are a damn site easier to replace.

paulbnix

onbike 1939 wrote:

Rather than face all of this faffing around every year (which is about right with these FSA bearings) and the associated costs, you could have course just chuck the whole thing and buy a conventional square-taper BB and chain-set. No drama, no yearly replacement of bearings but year after year of undisturbed use. I've worked on two bikes in the past week and each have had the same square-taper BB bearings for the past fourteen years.

Thats fine if I was not in the position I am in i.e. with a chain set with lots of life in it. Chucking the chainset equates to a few years of faffing in money terms.
I also have had a square taper BB fail well before its time - 6 months and about 600 miles.
If the HT 2 compatible BB that I have ordered works ok with my FSA chainset then that opens up a number of possibilities ranging from £10 bottom end Shimano right up to £70 Hope.

onbike 1939

paulbnix wrote:

onbike 1939 wrote:

Rather than face all of this faffing around every year (which is about right with these FSA bearings) and the associated costs, you could have course just chuck the whole thing and buy a conventional square-taper BB and chain-set. No drama, no yearly replacement of bearings but year after year of undisturbed use. I've worked on two bikes in the past week and each have had the same square-taper BB bearings for the past fourteen years.

Thats fine if I was not in the position I am in i.e. with a chain set with lots of life in it. Chucking the chainset equates to a few years of faffing in money terms.
I also have had a square taper BB fail well before its time - 6 months and about 600 miles.
If the HT 2 compatible BB that I have ordered works ok with my FSA chainset then that opens up a number of possibilities ranging from £10 bottom end Shimano right up to £70 Hope.

I agree that it's a real bind to have to do this but for me it was preferable to changing the outboard bearings until I pop off so I found an unused old stock Campag Chorus chainset and used that as a replacement.

As to your experience with conventional square taper BBs then I do think your experience is far from the norm and I have worked on a fair number of bike over a forty-year period. They really are a durable piece of kit.

keef66

I think some cartridge BB's were better sealed than others. Nameless square taper object in my son's Saracen MTB which was used for paper rounds in all weathers disintegrated in a year. Octalink XT BB in my MTB was still going strong when it was stolen after 12 years.

Driveside seal on my HT2 105 BB appeared to have disgorged most of it's grease but still felt smooth when I replaced it after 6 years. I'm hoping the press-fit BB in my new CR1 lasts as long.

paulbnix

The HT 2 BB from Trailbright arrived today.
I have fitted the BB and find that they are very slightly shallower than the previous Mega Exo BB. With the preload fully tightened there is a gap of less than 0.5mm between the crank and the seal on the top of the bearing.
The gears work fine after a small adjustment of the FD.
The BB arrived with some spacers but they were all 2mm and not suitable.
I have had a brief ride and only noticed that there was no longer any noise

Should I try and find some 0.5 mm spacers? Any suggestions where? Or will this small gap not be an issue?

Ouija

They are a combined MTB/Road BB. MTB BB cups are narrower than road ones so you need to use a spacer to get them out to the same width as a road BB. You can get 1.0 and 0.5mm spacers too (some bottom brackets come with 2x 1.5mm, 1x 1.0mm and a 0.5mm). ChainReaction do 1mm spacers.

The axle will slide from side to side if you don't get it touching the bottom bracket. In the meantime, just put one of the 1.5mm spacers that came with it on the non drive side cup so the axle doesn't end up being too short. It shouldn't significantly alter your chain line (0.5mm is really too small to notice).

And don't overtighten the left hand crank arm.. HT2's are susceptible to side loading and will significantly shorten their life span (the GXP system of cranks where invented to specifically prevent this, as many users end up crushing the bearings from the side).

paulbnix

Thanks - I did wonder about just adding one spacer - 1 each side was definitely too many.
I'll give it a try.

Update - presumably the spacer goes between the bearing cup and the frame?

Ouija

yep.

gsk82

Thought i'd bring up this thread again for the purpose of keeping the forum tidy.

I have an FSA mega exo BB and crankset. After a bike fit i'm going to change to a shorter crank length, but 167.5mm mega exo crankset seems illusive. Will a Sram or Shimano BB fit my frame? If it will it gives me a far greater selection of cranksets.

Thanks

imposter2.0

Mega Exo is a threaded BB for a 68mm shell, so any other threaded BB for a 68mm shell will fit