Poxy gears something is wrong

[Andy B]

I am a professional cycle mechanic

I have 15 years experience in cycle workshops

I have never ever had to file a taper bb

I strongly advise that you do not do it

It will be something else, it will not be the tapers on the bb

 

[Danthefestaman]

Re:

Sorry I don't mean to sound like a know it all, genuinely appreciate any help advice. The main thing I'm trying to achieve is finding the cure, at that point I can sort out the best resolution. For example it may be that the SR Suntour crank matched to the standard Carrera VP bottom bracket had a different offset and so worked well. So me replacing like for like doesn't work and I need a completely different bottom bracket. I have found a picture of the bike prior to me doing bits to it and I cant make out the components.

 

[lensmansteve]

I have used Alivio cranksets (M442) on a couple of my bikes, they are "wider" than most old cranks, both in chainline and "Q", which is the distance between the planes that the pedals rotate in. Try a 107mm bb, or even a 103mm. What length bb's have you got now?

 

[JoeH]

If you have changed the crank arms, it sounds like they sit too far out

This is exactly what I think too.
I have loads of Q's /assumptions

1) what length of BB do you currently have?
2) what exact model of triple Crankset?
3) what model of left shifter (assume 3 speed)?
4) assume you have all new inner and outer cables, running kink free? - they can stretch and you need to reset.
5) assume front derailleur isn't bent/or rotated around. (a photo from birds eye will confirm?
6) assume that when in the small ring, 1 click/micro click on shifter immediately moves front shifter outwards

Finally, I find that a front derailleur, especially a triple on cheaper older bikes albeit decent enough bikes/kit, are THE hardest thing to set up on a bike.
This is because you want the derailleur to touch the chain at the right point and not at the others, unlike a rear derailer which is always in contact with chain via jockey wheels.

Personally I would buy a few cheapy BB's of differing lengths of SJS and have some fun experimenting.
https://www.sjscycles.co.uk/bottom-brac ... m-bracket/

 

[lensmansteve]

I personally don't understand why a "cheaper, older" bike should be any different to an expensive new one. If the front mech is properly aligned, and adjusted correctly for height, the point at which the chain touches the front cage can't be improved/altered.
And save money, don't buy a bunch of bb's. Measure up carefully using your existing one(s) and just buy the one, aka the right one.

 

[legrandefromage]

Looks like a Suntour 'SR' branded one piece chainset

something like this should give you the same offset as the originals

https://www.ebay.co.uk/itm/M-Wave-Chain ... 0005.m1851

 

[JoeH]

I personally don't understand why a "cheaper, older" bike should be any different to an expensive new one. If the front mech is properly aligned, and adjusted correctly for height, the point at which the chain touches the front cage can't be improved/altered.

From personal experience I find that. I do tend to mess with old bikes, don't we all. Main reason because of dirt and wear - pivots can wear on front mech, obviously an 'expensive new one' won't be worn. Also 'expensive new' can have more rollers and pins on rings etc to help catch the chain. The point i'm making, I find as a bike mechanic one of the hardest things to get spot on is a triple to change - especially when BB/Chainset combo is of unknown compatibility, and/or possibly old or of low quality.

And save money, don't buy a bunch of bb's. Measure up carefully using your existing one(s) and just buy the one, aka the right one.

That is sensible advice but how do we know what the right one is? to know crankset details will help (hence q).
Again personally I like to try one or two to see the difference in practice, (only when the official data of BB length for chainset can't be found - which so far is the situation we are in). Also worth remember that going down by say 113 to 110 mm only moves your cranks set by 1.5mm (as differences is 3mm, / 2 as two sides = 1.5mm reduction per side). That may or may not be enough.

 

[Danthefestaman]

Re:

Current BB is 68 x122.5 STD taper. Used a Shimano one when built recently changed it to Carrera OE which is VP components. A little better as in it selects but not running right. All mechs and crank are Alivo, not sure on specifics, shifters I cant remember but new. Only part of the original bike I kept was the headset. Il add pics to show as they arrived might see a clue. If I get chance I will see if I kept all the old parts in the loft.

 

[Danthefestaman]

Re:

This seems to look like mine

https://www.ebay.co.uk/itm/Shimano-Aliv ... SwYpxd1n96

Says it dual pull, excuse my lack of knowledge does that mean pulls from under BB and down seat post tube?

Manually operating the mech by hand you cant seem to get enough movement to clear the chain.

The crankset suggested seems reasonable price. I remember when I built it I was going to use FSA but decided to go for matching to rule out compatibility issues

 

[legrandefromage]

122 is waaaaaayy too long!