Brucey wrote:I estimate that you are out by a factor of two.
Care to show me?
Brucey wrote:I estimate that you are out by a factor of two.
Brucey wrote:in degrees;
1/(2 x tan(1)) = 28.6mm/mm rather than 14.3mm/mm
or have I missed something?
cheers
OnYourRight wrote:
As Brucey says, there may be no significant difference in chainline between the Shimano 110 mm and Stronglight 107 mm. It’s just that the Stronglight collides with the chainset before the bolt (or screw to be more accurate) reaches the required torque.
.....
Does anyone know which Japanese chainset (a Sugino maybe?) the new-style Stronglight Impact is based on so I might look up its recommended bottom bracket length?
Brucey wrote:I think the machining on the crank is a bit weird; I wonder if they started making a triple and just forgot to machine the bolts for the inner ring and then called it a double instead. In general terms it is a bit odd for much of the crank boss on a double to protrude inwards past the inner surface of the inner chainring.
Putting some numbers to it (distance from centreline) ;
the RH end of the BB unit will sit at ~37mm (on a 68mm shell with a 3mm lip).
With a 43.5mm chainline the inner surface of a chainring 3mm thickness will lie at approximately 38mm ( 43.5mm less half of the ~8mm chainring spacing and half the chainring thickness).
So if you sight across the inner face of the inner chainring, pretty much anything that sticks out inwards is either going to clash with the BB or is meant to nestle inside the end of it.
recordacefromnew wrote:Please correct me if I am wrong. It seems you are finding/saying: i) the 107mm Stronglight clashes on the drive side, ii) the chainline from a 113mm is too great at 46.5mm, while iii) the 110mm Shimano bb delivers the same chainline as the 107mm (which I fully expect) although it doesn't clash because the Shimano cup geometry is different?
recordacefromnew wrote:If I were you I would either: a) get a Shimano UN5x 110mm, or b) wrap one single layer of kitchen tin foil over all 4 taper faces evenly on the drive side of the JP400 before installation.
recordacefromnew wrote:Blimey, I hope not everybody who bought or is buying one of these Stronglight chainset/bb combo has to go through your experience...
Brucey wrote:I think the machining on the crank is a bit weird; I wonder if they started making a triple and just forgot to machine the bolts for the inner ring and then called it a double instead. In general terms it is a bit odd for much of the crank boss on a double to protrude inwards past the inner surface of the inner chainring.
Brucey wrote:In the normal run of things, faced with a clash like yours, I'd probably modify one or other of the parts so that it fitted properly. I'd be somewhat disappointed (but not entirely surprised) if both parts came from the same manufacturer and were meant to fit one another.
Brucey wrote:Re removing the broken bolt; try tapping it round with a centre punch first, but this might be a job for the LH drill bit. If the axle is hollow all the way through, you can use a long series RH drill from the other side and that might shift it. If the bolt protrudes at all, you might be able to weld onto it.
BTW what torque setting are you using on the crank bolts? If the bolt hole in the BB spindle is skewed, (or the crank doesn't sit square because of a clash) tightening the bolt normally will cause it to see low-cycle fatigue in bending as the bolt is wound in. Barring excess torque, this is quite likely what caused the bolt to break.
CREPELLO wrote:Looking at the photo of the rear of the spider, the extra metal that extends beyond the taper mount seems unnecessary (apart from in a well engineered set up, it might add some marginal protection from water ingress).
CREPELLO wrote:I think that a well worded letter to Stronglight highlighting their shortcomings might be useful to them as well as yourself and others. You might be able to get the cost of a BB out of them if nothing else.
andrew_s wrote:niggle wrote:What causes problems is when you use inner and middle shifter positions for your 2 chainrings.
If using a triple shifter on a double chainset, you should use outermost clicks with the lower limit screw blocking off what would be the granny position.