CQP Cook Bros Chainset & Front Mech Clearance Problems

[peteteamtig]

Mmmm

Ya crank doesnt look right mounted , it looks like you need some spacers between the drive side lockring and the bottom bracket shell/frame , just to move the cranks away from the frame .

I concur with Lagrande , most compact front mechs will work to 46 tooth , after that you can be struggling with set up issues . And i'm sorry to say it but , they look knack'd anyway mate all chewed up in the square taper interface .

 

[julesg007]

Hi,

Buggered tapers I hope not :cry:

I've had a pretty good gander at them and they look OK. I think they looked a lot worse than they are as they were a tad dirty. The fit of the bb spindle into the crank arm taper also seems OK. I also tried the non drive side crank arm on the drive side and the clearance between the rear stays is the same as when the chainset is fitted - being around 7mm.

That said, is there any way that I can confirm if they are knackered?

I have, however, seemed to have had some success in sorting out the problem. I have raised the mech (as advised) and I can get clearance - well just around 1.5mm. However, the cage clearance above the top of the chainring teeth is around 8mm whereas I think this would normally be around be around 1-3mm. Also this seem to compromise the preformance of the mech - limited in using the bottom 2 gears only when on the granny ring (wouldn't be as bad if a 32 but only have a 28 bottom).

The XT front mech I am using was originally used in conjunction with an XTR M900 crankset (although a 46 chain ring) which is non compact so I was hopeful this work with the CQP.

Comparing the XTR against the CQP the XTR has more clearance between the chainring to the back of the crank. The XTR is 11mm and the CQP is only 7mm which I think may have a bearing on the problem.

Could it be the case that the problem is being caused because the 48 chainring is actually too small for this particular version of the CQP - could it be that with this length of crank arms it was designed for something bigger?

I have also checked the BB shell width and that is 68mm. I did insert a 1mm spacer and that didn't improve things the clearance remained the same.

I am going to check things using the XTR cranks to see how that goes - would have used them but they are too short as only 170mm - and will report back.

Will also report back when I have the XTR M901 mech.

Please keep your help and comments coming.

Jules

 

[mvd1974]

..don't know about the front mech, but I used to 'tune' mine while using Ritchey cranks. If you use an old enough front mech you can get out the screw on the back end of the cage and switch the front part of the cage to the back of the back part, making the cage about 1mm narrower. That did do the trick for me...

 

[utahdog2003]

your xt mech is designed for compact drive rings and may have trouble with rings over 46t


allegedly of course.

I'll second that. I was reading the thread and waiting for somebody to give up this as the cause.

 

[julesg007]

Evening All,

As promised an update.

I started a thread on MTBR.COM and that has proved to be very helpful.

http://forums.mtbr.com/showthread.php?p ... ost6230996

From what has been said there is a simple explanation to the problem. This crankset has clearance problems and what I have experienced is pretty common especially due the age of the crankset - most definately from an era of much simple components and far fewer gears.

The solution seems to start off with trying to use a front mech that has a narrow cage and flattest outer cage frame you can and some fine tuning.

If that doesn't work you'll have to break out the file and create a notch in the back of the crank arm. I understand this is not as dramatic as it sounds although probably scary for the first time (one guy has done it 3 times). There is a link in the MTBR thread which takes to you an advertisment for these cranks from I think 1991 and the notch was machined into the arm.

I have now changed the XT FD-M737 and fitted an XTR FD-M901 and installed a 1mm shim/spacer behind the bb drive side cup and that has helped. I am sure that with some further fiddling and farting around I will only have to resort to the file to remove only the smallest amount.

That said by using a larger ring the clearance issues become less of a problem even disappering so at this stage I am even mulling over using a 50T rather than the 48T as the bike will spend practically all it's life on the tarmac.

Once finally set up I'll update and post some pictures.

Jules

 

[rumpfy]

MTBR VRC can, on occasion, be helpful.

 

[gsy971]

have the RSRs and plan on installing them on my 01 Klein Adept but i have a problem on the non-drive side where the inside of the crank arm is not clearing the lower portion of the full suspension swing arm. its not clearing by that much so i am just think of getting a longer bb spindle. right now i have the 73x113 and i guess i would just swap out to get a 73-122? i have not yet installed the drive side cuz i haven't received my middle chain-ring yet but i may have to anticipate the probs the OP (and other) ran into. i'd rather not "grind" down my crank-arms so just getting a longer spindle solve the problems? what about using a spacer?

 

[utahdog2003]

Evening All,

As promised an update.

I started a thread on MTBR.COM and that has proved to be very helpful.

http://forums.mtbr.com/showthread.php?p ... ost6230996

The solution seems to start off with trying to use a front mech that has a narrow cage and flattest outer cage frame you can and some fine tuning.

Jules

The solution IS a front derailleur with a narrower profile and a flatter outer cage...which means a period front derailleur...like I said, a non compact, 6-7 speed front derailleur. On the MTBR thread...Rumpfy's post is spot on.

Please don't file the crank. :?

 

[utahdog2003]

MTBR VRC can, on occasion, be helpful.

Smarty-pants.