I've running these BBs on 2 bikes, a BLT2 and Prophet. The Prophet gets through a couple a year, despite being ridden in exactly the same places, same way and by a similar rider. The BLT2 is on it's 2nd after over 2 years.
Any reason they seem to wear quicker on different bikes?
And, does anyone know of a reasonably priced alternative that should last longer? What other models / brands are compatible with Truvativ cranks?
cheers
a,
The axle size is unique, requiring a GXP BB.
They do not use the Shimano pre-tensioning mechanism which can be highly destructive in some people's hands, but rely on the BB being exactly sized when the bolt is tightened. If the BB is not exact, the bearings will be wrongly loaded. If the BB is not 'clean-and-square-faced' the bearings could be slightly distorted as the assembly is tightened up. I am not suggesting you must get them faced at the shop, you can check for yourself by seeing the clearance is even all the way round with a feeler-gauge when slightly undone.
You can get ceramic bearing versions, but I do not hold out much hope of a longer life even if you repack the bearings frequently.
PaulD
Hope stainless are a longer lasting alternative IME
Yep, but what cranks at Hope BBs compatible with?
Thanks Paul - I have my suspicions that the BB was faced correctly and/or the BB threads are slightly mashed, that would fit with unevenly loaded bearings.
Just as well these things are only £20 and essentially disposable.
hope do an insert which you press into the NDS of their (and presumbly anyone else's?) bb's which allows you to fit gxp cranks. The sideways loading/tolerance issues will be the same though since it does up the same way, ie clamps on NDS bearing and either 'floats' on DS side or mushes it about because whole assebly is either too wide or slightly on the squint. Allegedly their bb's are better sealed and last longer though.
I had GXP cranks and BB on my Boardman, which wore out quickly - less than a year of very infrequent riding, probably a few hundred miles at best. Replaced it with a Hope stainless steel with the GXP adaptor - had the BB faced before it was fitted.
That's lasted almost two years so far, first on the Boardman, then on a Soul, with the bike being used a couple of times a week for a proper ride (in all weathers) and for a short commute most days. Already ten times as many hours of use from the Hope as from the original GXP.
bin the gxp and cranks and buy some shimano. utter dross IMHO.
Apparently the Superstar GXP BBs have bearings that don't suffer the side loading problems - not used them, but maybe worth a cheap go before spending £££ changing chainset/BB?
Thanks Steezysix, might give that a go.
One difference between the 2 bikes is that the Prophet has a BB mounted front mech, so I dont use a BB spacer on that side. Not sure the width of the BB mount would be exactly the same as the spacer?
Excuse my ignorance, but what is "press fit"?
[url] http://superstar.tibolts.co.uk/product_info.php?cPath=23&products_id=491 [/url]
strange BB width too, I need a 68mm GXP BB.
I've run a GXP crank for a couple of years on one of my bikes and have just replaced it with SLX. That tells you all you need to know.
The more recent GXP BBs have a "Gutter Seal" which is a plastic shim that fills the gaps between the axle splines, so as to prevent water ingress from damaging the bearings from the inside. It probably won't make much difference though, as I've dismantled a couple of ronnied Truvativ BBs and have found that the bearings cosmetcially look fine, so it's not rust that's causing the problems in my particular case.
Oh and nine months for a GXP BB used only in dry weather is about the best you can expect. By comparison, I've Shimano BBs that are about to enter their third year and which are doing just fine. If you really like your GXP cranks then a Hope BB is the only way to go, otherwise go Shimano.
@agent
Pressfit is for non threaded Bottom Bracket shells. It works in a similar way to a headset as the bearings are pressed into the frame. You don't want one of these if you have a 68mm BB shell.
Thanks - I'd better not buy press fit in that case!
Yep, XT BB on my hard tail, mainly ridden in the winter in west country claggy mud and it's still going in it's 3rd year.
I want an excuse to switch to a 10 x 2 set up, maybe now's the time
if you gpx bb is slightly worn you can't put a thin spacer between the frame and bb shell to take up the slack 0.25mm is enough. gpx is very sensitive bb shell width.
My experience with the Superstar angleset gxp bb was very poor. Very badly sealed and became gritty after a couple of (admittedly) very wet rides. IMO the original sram one is a lot better, and that's saying something!
Another voice of caution on the Superstar BBs. I bought one a couple of months back and it has already been replaced. OK so it was very wet for a few weeks but the bearings appear not to be sealed very well as they ran very loose quickly and then seized. I replaced it with a new style Sram BB and am keeping fingers crossed as it has only been in for a fortnight.