sorry... this is modern and silly

[Dead Rats]

Anyone here use(d) a Truvativ FireX chainset and matching BB?

I'm fitting one to a late '90s steel frame and I can't get the driveside arm to contact with the face of the BB cup. I tried very gentle persuasion with a soft mallet but no... they are still about 3mm apart. Bit confused as not very familiar with external type BBs... for the record, the bike was previously using a 110 x 68mm s/taper BB which gave a perfect chainline and I've fitted one 2mm spacer per side (between frame and cup)

Thing is, with the LH arm fitted, there's is no play at all, ie it feels fine, very smooth and solid... and, after I fiddled with the front mech stops, I can engage all the gears no trouble... surely this gap should not be there? Am I missing a spacer?

 

[sam264]

is it an external bb? if so, i think the gap is fine. if there isn't any play then it's ok. I'm running these cranks pictured below, are they similar to that? if so i think there was a slight space on that too, should be alright. Can you get any photos? you MIGHT be missing a spacer but i would have thought the cranks would slide from side to side if there was.

 

[Dead Rats]

thanks for that, yes it's an external BB, a Truvativ GXP with matching FireX crankset. Just seems odd that the LH side is flush with the BB cup face and the RH is not. I think if I used more spacers I would just get less bite on the LH side arm. The crank arms are both the same distance from the chainstays by the way.

I followed the instructions which I downloaded, they just say to push driveside arm through until spindle stops (check) and that a 68mm shell just need one spacer per side (check). I noticed that the instruction don't mention greasing the BB cup face to prevent friction against inside of crank arm, so maybe a 3mm gap is fine (given that there's no play I can only presume I'm ok)

As I say, if anyone else has this exact crankset & BB combo, please can you look at your bike and see if there's a gap to put me out of my misery? I guess I could take it off again and try to slide the RH bup onto the spindle and see if it goes flush when not fitted to the frame?

 

[longdog]

Wanders off to look at his bike!

 

[longdog]

Same crank and bb as yours and the same 3 mm gap.

 

[Dead Rats]

Same crank and bb as yours and the same 3 mm gap.

PHEW! problem solved thanks!!!

 

[Dead Rats]

ok final question on this matter, I have fitted 1 x 2mm spacer on driveside and 2 x 2mm spacers on LH as stated in manual for a clamp-on front mech and 68mm shell... and the chainline is too far to the right

Given that I was running a narrow 110 x 68mm BB previously for perfect chainline, does anyone think I can get away without a RH spacer? Or will my whole crankset be too far to the right (ie left hand arm closer to frame than right)?

 

[longdog]

I dont use any spacers on mine. Found That the spacers made the bb sit odd, but I dont use a front mech.

 

[Dead Rats]

hmmm... and did that improve your chainline? is your front ring in middle ring position?

 

[longdog]

40t ring on the out side.
Chainlines ok, could mybe be better, but am sick of messing about with it.