|Chainline (?) problem for the experts - any suggestions.||Steve Young|
Dec 8, 2003 8:03 AM
|Well, I finally got to fit the new Record Pista Crankset to the Fuji this weekend. The delay was waiting to get all the begged borrowed or bought tools necessary together and that finally happened early last week.
All went pretty well. It was a real struggle to get the old cranks off but with the right tools this was achieved with no slips (and no further loss of skin!).
Everything went back on nicely and looks great. I am running 46 tooth up front and 16 out back which moves the wheel back nicely in the drop-outs and enables fitting of a 700c 25 tyre on the back with reasonable clearance. (Jeff you were wondering about this a few weeks back). The wider tyre significantly improves ride comfort.
So: The Fuji is now somewhat overdressed with the Phil hubbed wheels and the record crankset. Here's the problem.
Chainline seems reasonably good. Everything runs fairly quietly - certainly no noisier than it was when new and unmodified. However, there is STILL some chain noise and this is worse under heavy load. Investigation shows that although the chain is engaging the chainwheel correctly, the inner plates of each chainlink are binding slightly on the outside surface of the chainting tooth. This is evidenced by every other chaintooth being oily on the outside surface (from lubed chain). The other teeth (which sit betwwen the outer plates of the link (i.e. the wider aperture on the chain) are clean on the lateral surfaces. What gives?
Is the the chainring positioned slightly too far outboard (can't be more than about 1mm at max). Would moving it in slightly correct the problem? When I look at the cog on the back it appears to be meshing perfectly with the chain. This was not the case with the original set-up as supplied - when I took it apart the first time there was clear wear on the rear cog on every other tooth - so same thing as described for the chainring but appears to have been corrected when I replaced the wheels.
Is is possible that a minor chainline deviation might cause the chainring to mesh slightly off centre whle the rear cog appears perfect ?
Finally, When I fitted the new (cartridge) bottom bracket, it was clear that the bottom bracket shell was a bit untidy (i.e. some paint spots etc on the mating surface with the fixed cup). I didn't worry about this (or have the BB faced) as I figures it was probably non critical with a cartridge set up. Was this a mistake? Would stripping it down and facing it (and moving the chainring inboard about 1mM (certainly <2mm)) have any effect on the alignment with which the chain and chainring mesh.
I would really appreciate any thoughts as I'm running out of ideas in my quest for a quieter drivechain (I'm not where I want to be yet although you will probably have realized that I'm being a bit picky about all this - it's a bit of a crusade now!) [but it's not stopping me riding!!]
|One thing at a time....||rcmann|
Dec 8, 2003 8:29 AM
|You said you replaced the crank-I assume with a new one? Is the cog new as well? Putting an old chain on a new ring/cog can cause noise. Also, don't guess at the chainline, lay a metal straightedge across cog/chainring and see if lies flat across both. If not, adjust BB (if possible), swap out some washers on the axle (which requires redishing the wheel), whatever it takes to make the chainline dead straight. Once you know the chainline's true, you've completely eliminated one factor and can work on uneven chain/cog/chainring wear, compatibility, chain too tight, etc.|
|Thanks: Some extra info and more questions||Steve Young|
Dec 10, 2003 8:25 AM
|I think the noise is coming from the chain not meshing completely square with the teeth on the cogs and chainwheel. It rubs on the inside of the cog and the outside of the chainwheel (every other tooth only).
The cog in use at the time of the experiment above was a 16 tooth cog with ca. 500 miles on it. It looks pretty fresh in terms of tooth profile although there are some superficial signs of wear on every other tooth (only on the edges).
The crankset was new out of the box at the time of fitting.
The chain has about 600 miles on it but there is no detectable wear (elongation) using a Rohloff caliber.
I stripped everything down again last night (much easier the second time with all the torques adjusted and all the threads greased), CAREFULLY filed off the paint from the end of the BB shell with a smooth file and reassembled.
The problem persists.
The problem is also seen on a different cog (18 tooth with only about 100 miles on it). This cog is on the other side of the fixed/fixed wheel and the exact same problem (noise which I am now almost certain is due to flawed chainline) is present.
The frame is a Fuji Track. I haven't checked frame alignment (I will do this when I work out how) but I'm sure it will be fine (new bike no crashes). When I measured the rear drop-out dimensions they are near perfect at 120mm (digital caliper).
Rear wheel is Open Pro rim on a high flange Phil Wood track hub. It's fixed/fixed with no dish. If chainline is the problem I would have to space the cog out from the centreline. I can't afford to do this as there is insufficient thread on the lockring to allow me to lose enough to correct the chainline. Also it's very important to me that the wheel is reversible - I'm looking for perfect chainline on both sides.
The wheel is perfectly centred in the dropouts (I measured it and it's within 1mm on each side at all of 8 points on the rim where I checked (both sides). (It's a very nice wheel:)
Only two possibilites remain.
a) I need to replace the chain. (I really can't believe this is the problem but have ordered an SRAM PC1 just to be sure. I'd feel an idiot if this was the cause and I can always keep it as a spare if it proves not to solve the problem)
b) The new crankset is outboard a few mm. I can't see why this would be given that I fitted a Record Pista crank on a record bottom bracket. The crankset and the hub are all standard track equipment and should be compatible - right ? There is no way to move the crankset inboard with the current set-up so I think the only way to address the problem would be to try an alternative bottom bracket which allows for adjustment.
P.S. The fixed cup of the BB does go on the right (drive) side of the bike doesn't it ? I'm casting around for idiot mistakes as well although I'm reasonably confident I haven't made any.
I will get a straight edge suitable for measuring the chainline as suggested and quantitate the error. That was a good idea.
I could probably take this to a local shop and get it sorted faster and cheaper but I really want to solve it myself - once I have this down I will feel like I know a lot about chainline !! (If I get there)
This board is a tremendous resource.
|Two more questions :)||Steve Young|
Dec 10, 2003 8:34 AM
|Can anyone recommend a good quality BB compatible with Campy record Pista crankset which allows for adjustment. IIRC I think someone once said that Phil Wood BB's have some built in adjustability - can anyone confirm?
If I have the bottom bracket shell professionally faced is this likely to result in the removal of a significant amount of material and move the crankset inboard a mm or more? Is there a standard size (width) for the BB shell that I can check mine against?
Anyone got any ideas I haven't listed ? (o.k. that's more than two questions)
Dec 10, 2003 9:21 AM
|...assuming it's the chainline, which is what it sounds like. You can use the same BB, respace/dish the rear wheel then only use one side of the flip/flop. The other option, as you say, is to use a Phil BB. Talk to Brent at Phil, tell him what you've got, and he'll give you the correct length and taper BB for the application. Phil BBs allow ~5mm L/R adjustment, which makes for a really easy chainline adjustment. I use one on my 29"er MTB with a Rohloff hub, and it works great. I like classic cup/cone track stuff for the fixed, and I had to respace/dish the rear wheel ~1mm to get it straight, but then again I'm using a hub that's threaded on only one side. BTW, just get a metal carpenter's square ~18-24" long, and lay the edge across the cog/chainring. Good luck.|
|I picked up 2 Campy (Athena?) BBs with no lip on either side...||TFerguson|
Dec 11, 2003 6:32 AM
|Simple cartridge type that I can position anywhere I want, within reason. They were $20-$25 each - way cheaper than a Phil. I'm using them with a Campy Strada with the outside ring.
|re: Chainline (?) problem for the experts - any suggestions.||ukiahb|
Dec 8, 2003 9:09 AM
|I'd also say to measure and set your chainline carefully...I finally got mine dialed in this weekend and the bike runs better and more quietly. there is a great article on chainline at http://www.sheldonbrown.com/chainline/|| |