Uneven crankarm clearance...

TONY.M
TONY.M Posts: 94
edited November 2012 in Workshop
...or something like that. Pictures are worth 1000 words so here is what I mean.

chainlineimg1146.jpg
chainlineimg1147.jpg

The clearance is actually around 2mm closer than the ruler shows so about 8mm driveside and about 2.5mm left side. Highly frustrating as you can imagine and I am clueless as to what is the cause.

The frame is a brand new Dolan Pre Cursa bought from Dolan this week.

The cranks are Stronglight 2000 (165mm) and the bottom bracket is a Stronglight JP400 107mm. The BB is brand new and the cranks are from my PX track bike with light use and are undamaged. Planet X recommend a 107mm BB for a 42mm chainine which is what I bought.

I fitted the old BB (also a 107mm labelled JP400 though different - see photo below) and believe it or not the chainring was up against the driveside chainstay leaving scratches.

The old BB from last year is on the right with pink grease, as you can see they are clearly different.
chainlineimg1134.jpg

So I am basically after suggestions from folk who possess more knowledge than me on how to fix this very annoying issue.

Thanks in advance.

Tony

Comments

  • nicklouse
    nicklouse Posts: 50,675
    buy another BB as there is nothing you can do with your new one.

    or live with it.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • TONY.M
    TONY.M Posts: 94
    nicklouse wrote:
    buy another BB as there is nothing you can do with your new one.

    or live with it.
    You recon that the BB is the culprit?

    Tony
  • nicklouse
    nicklouse Posts: 50,675
    yep just look at the thickness of the flange. it will do what it has done.

    stand them on a flat surface and you will see the top of the axles will be the same but the flange face will be lower.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • TONY.M
    TONY.M Posts: 94
    nicklouse wrote:
    yep just look at the thickness of the flange. it will do what it has done.

    stand them on a flat surface and you will see the top of the axles will be the same but the flange face will be lower.
    OK thanks, I think I know what you mean now. Effectively it does not go as "far" into the bike as the flange stops it thus meaning the left crank arm is closer to the chainstay.

    Any solutions to what would bring the clearance even on both sides?

    Cheers
  • nicklouse
    nicklouse Posts: 50,675
    a different BB that does not have such a fat flange.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • TONY.M
    TONY.M Posts: 94
    nicklouse wrote:
    a different BB that does not have such a fat flange.
    Cheers Nick!
  • sungod
    sungod Posts: 16,888
    just a thought, if you measure the width, face to face, of the bb shell of the bike, is it 68mm?

    if it's wider (or narrower) then the bb is going to be off-centre vs. intended position

    has the bb shell been faced? if the edges have paint on it probably hasn't been, if it is wider than 68mm then facing it would reduce it
    my bike - faster than god's and twice as shiny
  • TONY.M
    TONY.M Posts: 94
    sungod wrote:
    just a thought, if you measure the width, face to face, of the bb shell of the bike, is it 68mm?

    if it's wider (or narrower) then the bb is going to be off-centre vs. intended position

    has the bb shell been faced? if the edges have paint on it probably hasn't been, if it is wider than 68mm then facing it would reduce it
    Will head to the garage now to check.
  • nicklouse
    nicklouse Posts: 50,675
    TONY.M wrote:
    sungod wrote:
    just a thought, if you measure the width, face to face, of the bb shell of the bike, is it 68mm?

    if it's wider (or narrower) then the bb is going to be off-centre vs. intended position

    has the bb shell been faced? if the edges have paint on it probably hasn't been, if it is wider than 68mm then facing it would reduce it
    Will head to the garage now to check.
    and as it was fine before it will be in tolerance.

    not the problem.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • TONY.M
    TONY.M Posts: 94
    nicklouse wrote:
    TONY.M wrote:
    sungod wrote:
    just a thought, if you measure the width, face to face, of the bb shell of the bike, is it 68mm?

    if it's wider (or narrower) then the bb is going to be off-centre vs. intended position

    has the bb shell been faced? if the edges have paint on it probably hasn't been, if it is wider than 68mm then facing it would reduce it
    Will head to the garage now to check.
    and as it was fine before it will be in tolerance.

    not the problem.
    The frame is brand new and never used before, the old bb was from another track bike.

    The BB shell is 68mm and still has paint on it though not very much and would not make a few millimeters so the BB must be the issue. Even with the cranks "even" the crank spider is very close to the chainstay so a BB with a larger axle may be needed, this will mean a larger than 42mm chainline though.

    Thanks
  • k-dog
    k-dog Posts: 1,652
    It might be making the crankset sit at a very slight angle though. Can you tell if the unevenness is the same with the cranks pointing forward?

    Probably worth facing it for about £10. I didn't and my BB wore out sooner than expected. Just had it faced for a new one.
    I'm left handed, if that matters.
  • On the Dolan website, the BB sets they sell for track frames are 109mm spindle length. Those extra 2mm may well resolve your problems.

    http://www.dolan-bikes.com/Dolan-Compon ... %20bracket

    I'm convinced that your problem is the spindle being too short because you are suffering from the spider being too close and the non-drive side crank being too close. If it was a problem with the offset caused by e.g. the thicker flange on your new BB, one side would have too big a gap and the other too small.
    "The Flying Scot"
    Commute - Boardman CXR 9.4 Di2
    Sunday Best - Canyon Ultimate SLX Disc w/ DuraAce Di2
  • TONY.M
    TONY.M Posts: 94
    k-dog wrote:
    It might be making the crankset sit at a very slight angle though. Can you tell if the unevenness is the same with the cranks pointing forward?

    Probably worth facing it for about £10. I didn't and my BB wore out sooner than expected. Just had it faced for a new one.
    I will check again a bit later on. Do frames have to be faced for cartridge BBs or is that only for external bearing BBs?
    mpdouglas wrote:
    On the Dolan website, the BB sets they sell for track frames are 109mm spindle length. Those extra 2mm may well resolve your problems.

    http://www.dolan-bikes.com/Dolan-Compon ... %20bracket
    It might do and I will ask Dolan what they think.

    Thanks
  • I'm not sure if this is just the angle of the photo but the tyre / chain stay clearance looks uneven too. If so I suspect the problem is to do with the frame.
  • sungod
    sungod Posts: 16,888
    TONY.M wrote:
    <...>
    I will check again a bit later on. Do frames have to be faced for cartridge BBs or is that only for external bearing BBs?
    <...>

    it's possible it was faced by dolan before painting, some external bb systems specify a tight tolerance for width, but for a cartridge bb it's not critical as long as it's about 68mm, which you've verified

    the 109mm bb suggested above sounds promising, definitely worth asking dolan
    my bike - faster than god's and twice as shiny
  • Monty Dog
    Monty Dog Posts: 20,614
    The lack of chainring clearance would be my worry - it's unlikely you'd notice one crank being slightly closer than the other. Does suggest that rear triangle alignment could be out - worth getting it checked
    Make mine an Italian, with Campagnolo on the side..
  • TONY.M
    TONY.M Posts: 94
    There is no way a 42mm chainline is possible with this as the crank spiders are touching the chainstay... very frustrating and seems strange as a popular track crankset will not fit a popular frame. I am thinking that perhaps this batch of Pre Cursas have been altered but I'm speculating of course.

    I would love to hear from anyone who has a Dolan Pre Cursa and if they had any issues.
    Monty Dog wrote:
    The lack of chainring clearance would be my worry - it's unlikely you'd notice one crank being slightly closer than the other. Does suggest that rear triangle alignment could be out - worth getting it checked
    Thanks Monty, it is actually the crank spider that touches the frame with a 42mm chainline although the a 48t chainring is also very close. There is no problem at all with my other track bike (Planet X carbon) with the same crank and BB.

    Cheers
  • Just being curious because I have no knowledge. I'm assuming that the "chainline" you are talking about is the gap between the frame and the chain?
  • nicklouse
    nicklouse Posts: 50,675
    johnboy183 wrote:
    Just being curious because I have no knowledge. I'm assuming that the "chainline" you are talking about is the gap between the frame and the chain?
    nope distance between the center of the seat tube abd the center of the rings (ring).
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • nicklouse
    nicklouse Posts: 50,675
    sungod wrote:
    TONY.M wrote:
    <...>
    I will check again a bit later on. Do frames have to be faced for cartridge BBs or is that only for external bearing BBs?
    <...>

    it's possible it was faced by dolan before painting, some external bb systems specify a tight tolerance for width, but for a cartridge bb it's not critical as long as it's about 68mm, which you've verified

    the 109mm bb suggested above sounds promising, definitely worth asking dolan
    I always do as if it is out it can distort the BB causing the NDS cup being a bit of a pig to fit.

    OP so this is a new build? i was under the impression that the "old" BB had already been fitted and used and you were just replacing it.

    and as mentioned above talk to the supplier about the correct axle length for that crankset for that frame.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Thanks
  • Monty Dog
    Monty Dog Posts: 20,614
    The fact that the OP has measured the chainline at 42mm and that the chainring is touching the chainstay strongly indicates that the rear triangle is mis-aligned IMO.
    Make mine an Italian, with Campagnolo on the side..
  • TONY.M
    TONY.M Posts: 94
    Monty Dog wrote:
    The fact that the OP has measured the chainline at 42mm and that the chainring is touching the chainstay strongly indicates that the rear triangle is mis-aligned IMO.

    After doing the string test to check alignment it shows that it is perfect. Not that I could not have got it wrong but I don't think that is the issue.

    I have found out that others have had issues with the thick spider of this chainset, although the cranks coming close to the frame seem to indicate that the chainstays are just too thick for a 42mm chainline which is very annoying on a track frame.