Issue fitting FSA SLK Chainset - *SOLVED* due to non compatibility of Truvativ GXP BB with 24mm axle

[yvs24]

Hi guys,

I have a bit of a strange issue where I am in the lucky position of having a carbon De Rosa King frame and am kitting it out with mainly SRAM Red and in the case of the chainset (or at least I hoped) a FSA SLK Light Mega EXO double. The issue I have is that the frame already has external BB cups on it which I was told at time of purchase were either SRAM or FSA and therefore compatible with Shimano Hollowtech. I therefore measured it just to be sure using my digital calipers and whilst they do tend to vary a bit all of the different measurements I took cam in at around 23.76mm to 24.17mm so it does appear to be 24mm. I have tried fitting the axle through the BB cups and frame from the drive side and basically it stops. It is pretty tight just getting through the external cup (but I don't have a problem with a snug fit, no issues with movement etc) and then stops.I've managed to wiggle it back and fore a bit at this point and it seems to sit as if it wants to go through but is visibly at a slight angle and I don't want to force it when it is like that. For comparison I have also tried a Shimano Ultegra Chainset which I dropped off another bike and that went through no problem, or at least as far as the non drive external cup where it also stopped but that may just be a matter of fiddling about a bit and I didn't want to do that as it's not the Ultegra which I want to use on this bike going forward. I've never had this issue with external BB cups before and wonder if anyone has any ideas ? The SLK chainset, it's brand new BTW, was supplied with a ceramic BB and slots through both cups no issue. What I'm wondering about is the "sleeve" that you always get the BB cups supplied with, in the past some people have told me that they fit this into the frame in addition to the cups whereas other people have said that's definitely not the case. I've seen a mixture of both and as I'm normally dealing with used components and don't have this "sleeve" it's therefore not an option. What I'm thinking is that if the sleeve from the BB that's fitted is in there and has any variance in diameter it may be preventing the SLK axle going through as the tolerance seems to be very little even when going through the external cups. So now the obvious question, why don't I just take the existing cups off , replace with the supplied FSA ceramic BB and then try again. Basically it's not that easy as whoever put these cups on and whatever they used to do so were no respecters of torque settings. I've never come up against anything so tightly fitted and even though I've got the right tool the forces I'm having to exert, so far with no success, are frightening me / causing the tool to slip off, and I'm worried I'm going to damage what is a fantastic frame. I've had the frame jammed and have been leaning with half my body weight or more (and I'm not small) down onto a wrench and the cups haven't budged at all. As it stands I'm therefore looking at a 120 mile round trip to the best LBS I know of in my part of the country where I am sure they will be able to clamp the tool on with the frame fixed in some way if necessary and have extensions to wrenches etc. that can probably generate extreme force and hopefully get them off without any harm. Any comments ? Views ? Inspirational thoughts ? This is probably a £2K frame so I shouldn't take any chances right ? Thanks, Neil.

 

[T.M.H.N.E.T]

external BB cups on it which I was told at time of purchase were either SRAM or FSA and therefore compatible with Shimano Hollowtech.

Which is it? Because SRAM is not HT2 compatible

 

[Citius]

As above - plus, are you sure you are turning the cups the right way?

 

[yvs24]

 

[yvs24]

I don't know if the photos I just posted will a) get through to the forum OK b) be of any use but with the general appearance plus the Drive Side / Non-Drive side etching on there you have all the information I have. In terms of direction, I've been trying to turn opposite to the direction of the arrows also etched on so in the case of the second photo anti clockwise. Someone has also had a crack at this before me by the looks of things as the "grooves" that receive the splines on the tool have started to strip.

 

[HarryTheDog]

I would say the non-drive side looks to have the damage done in the direction to tighten it , not undo it. I always remember with BB threads it should undo in the direction you pedal. Pedal are the opposite. ie if you can undo a pedal , the BB is the opposite direction to undo it.

 

[jowwy]

Im using a dura ace HT2 bottom bracket with the same fsa k light megaexo crankset with no issues at all.......so yes they do work together, just need to be patient

 

[bpsmith]

How did you happen to have this frame @yvs24?

How come it was damaged prior to you having it? Can we assume that is why you ended up with it?

At face value, without the answers to the above, I would hazard a guess that you acquired it cheap due to the BB needing to be replaced, but couldn't be done due to the BB being hacked about with?

 

[yvs24]

It's possible, that prior "owners" have had issues with BB and maybe that's why it was never sold individually. Frame came as part of a job lot of stock from a bike shop closure. Most of the rest of the stuff was more retro (late 70's/80's framesets, wheels etc.) but there were some newer frames of which this one appeared to be stand out better than the rest. I don't have any more history than that, just will be a shame if it's not possible to use this due to a crazy situation like not being able to remove external BB cups. Out of interest I just measured the non drive side BB cup as my Ultegra axle didn't successfully get through the non drive side when I tried it and it's consistently coming up as closer to 22mm rather than anywhere near 24mm. Doing a bit of reading given this fact I'm wondering if this could be a Truvativ GXP BB with 24-22mm taper as described here: https://www.bikeman.com/bicycle-repair-tech-info/bikeman-tech-info/1599-bottom-bracket-types As it hapens I've got a Truvativ GXP crankset on a Boardman hybrid I have that is currently in bits and pieces; that bike came 70% assembled and I've never had any reason to take the crankset off, but it does use external cups so tomorrow I'll be disamantling that for a look at the sizes, axle etc. I've never heard of tapered axles and am struggling to think why you'd want to do that, so it will be ironic if I've had one for a a year or more without even realising it. Thanks for the suggestions so far.

 

[bpsmith]

Getting something to fit will be one thing, but pointless if the BB actually needs replacing before you start.

 

[yvs24]

Mystery over (at least for me anyway) as it is most definitely a Truvativ BB fitting. I got the Truvativ Elita GXP crank off the Boardman hybrid and it fis perfectly. So I'm going to proceed with my set up with this crank on for the moment and when is rideable see what the existing BB is like. Other than the wear and rear marks from someone having "fun" trying to get it on or off (off I asume but probably trying to turn in the wrong direction) it looks pretty perfect. In fact the whole frame looks like it's never really been out for any serious sort of ride if out at all. Hardly any marks around the dropouts, nothing around the chain stays, no marks on any tube in fact which would indicate it has ever been anywhere other than on display in the bike shop (which is what was suggested). If the existing BB is fine then I will probably buy a Truvativ road crankset, there are still one or two places around that have some by the looks of things, and hope to get it set for (who knows) 3000KM as it is. If then the BB needs to come off so be it, if the bike is used and used well (barring crashes) that point is bound to come and will cross that bridge when I get to it. I certainly will not be selling the bike to anybody else with this BB on unless someone really wants it, and if that is the case I will ensure they have all of the info I do including details about the BB and a practical demonstration of attempted removal with them present / trying it themselves so they can see what the issues are. Thanks for your suggestions, I hope if anybody else is in this situation they stumble across this thread and possibly manage to save themselves some time / money and stop themselves potentially damaging a frame, As it is I've got a spare FSA SLK Light chainset, still I've plenty of other bikes that can go on. Keep on riding guys !