GordoTrek

ok... i have recently rebuilt my trek 930 with newer parts,
i went with the same parts just new..., the only major changes i made to the drive train was, i went from a 7sp freewheel to a 8sp cassette in the back, i replaced the back/ front derailleur/bb/ and crankset with all new components, copied the same sizes for everything from the original parts

everytime i adjust my front derailleur i get chain noise/rub on the outer part of the derailleur,when its on the big cog in the front and into the new 8sp cog in the back
i can't get it perfect, its a shimano slx triple front
https://www.amazon.com/gp/product/B00...00_i00_details

any thoughts would be great, really getting frustrated..

DCB0

What shifters are you using?

In my experience, to get a front derailleur perfect you often have to begin at the beginning - which means disconnecting the cable, loosening the bolt clamping the derailleur to the frame, and realigning and attaching everything. THe height and angle of the derailleur (outside of the cage 1-3mm above the big chainring, perfectly parallel with the chainring) are crucial.
Also, if you swapped cranksets, are you sure you got the correct bottom bracket length? If you changed cranksets and kept the same BB length as with the old crankset your chainline might be off.

Also, are you sure the deraileur cable is routed through the pinch bolt properly? THere is a very common mistake when routing the cable that seems to be correct but winds up causing excessive cable tension and poor shifting performance.

Go the parktool.com and follow their derailleur setup guide to the letter, without skipping any steps. If this does not work... then.. well... I don't know... maybe you should give up and ride a single-speed

MilitantPotato

Are you cross chaining? If not, start fresh on the front setup.

GordoTrek

i did everything that park tool suggests, still getting that noise, i did notice however that my chainline is a tad off, i did get the same bottom bracket size as the original, however the crank is new but the tooth count is the same, as the original... am i wrong ?

himespau 

You're not using road shifters and mtb derailleurs are you? That'll throw your front shifting off as the pull ratio is different in Shimano.

Bill Kapaun

Did you use EXACTLY the same brand/model crank?
The BB is determined by the crank you use, not what WAS on it.
Most newer cranks use a shorter BB spindle, so if that's the case, your BB is probably too long.

Exactly what crank & BB did you use?

GordoTrek

here is the crank i got
https://www.amazon.com/gp/product/B00...01_i00_details
and here is the bb
https://www.amazon.com/gp/product/B00...00_i00_details
68 x 127

sorry read it too quick... not 175, 127

DCB0

175 is probably the length of the crank arm, not the bottom bracket. THat crank wold likely be best fitted with a 113mm bottom bracket. Your stock crank was probably fitted with a 122 or 127 bottom bracket.

cny-bikeman

That does not tell us which UN 54 you got - different chainlines. Here's what I got by Googling "bottom bracket M361"

https://techdocs.shimano.com/media/te...9830667768.PDF

GordoTrek

im guessing my bb is too long, i didn't know cranks were affected by the length of the spindle , not really sure how i would of known this, its not in the item description.. i guess that's the game you play when you order online...

himespau 

https://techdocs.shimano.com/media/te...9830667768.PDF seems to imply you want at 123 mm spindle. If you got the UN54 with the 122, that probably would work. Unless I'm reading that all wrong.

himespau 

Would 4 mm really make that much difference in chainline on a derailleur bike? On a non-derailleur bike, sure.

To me your original description sounds like you're just cross chaining and in that case the sound is perfectly normal. It's your bike's way of saying, "stop doing that, I don't like it." But then I don't know what I'm talking about most of the time.
You don't want to ride in the big ring in front and the big cog in the back (or the small ring in front and the small cog in back. That's just bad news. Hard on your chain and gear teeth.

Bill Kapaun

According to the Shimano tec docs, you want a 113MM BB for THAT crank.

So much for replacing the "same" parts. They aren't!

himespau 

Where are you seeing 113 mm? I don't think you can just look straight down between the two tables as the columns don't line up well. The 113 mm is for the UN26E and the Crankset table says he needs the UN26K and the bottom table says the UN26K is 123 mm. At least that's how I read it.

whitefiretiger

the 1-3mm above the big chainring are you talking with the fd in default no tention or when pulled out and over the chainring?

ive never gone about it that way. i install about where i think it should be and if it doesnt work quite right ill change the position.

Al1943

That's a good question.


Another good question.

CACycling

New Shimano FDs (at least all I've seen) come with a piece of tape hanging below the face of the cage that has pictures of teeth on it. You line the picture up with the teeth on the big ring when the FD is all the way out and make sure the cage is parallel to the ring.

whitefiretiger

interesting. i tend to buy take offs from lbs. i love it someone drops $3k on a ned bike and has the parts upgraded before taking it home and the oe parts are new and cheap but dont come with dirrections.

Bill Kapaun

Put the chain on the middle ring.
Shift to 4th.
Eyeball the chain line.
Shift to 5th.
Repeat.
Does the chain seem to angle equal amounts on either side of lining up exactly?
IF not, what cog does it seem to line up properly with.
8 speed spacing is 4.8MM between cogs. IF it lines up perfectly with 6th, your chain line is (2.4+4.8) 7.2MM too much. Lines up with 7th? Add 4.8MM more etc.

DCB0

https://sheldonbrown.com/chainline.html

According the the Sheldon Brown article linke above, chainline on a MTB is likely supposed to be 47.5mm. If it is an older bike it may be closer to the road trip[le standard ot 45 mm. To determine whuich measurement to use, measure the distance between the locknuts on the hub - it should be 130mm or 135mm (Call this measurement the O.L.D.) , then measure the distance between the edge of the drive-side locknut and the centre of the middle cog, or (in the case of an even number of cogs) the centre of the space between the two middle cogs (call this measurement C). The formula for determining the chainline (CL) is: CL = (O.L.D./2) - C.
THen measure the distance between the middle chainring and the centre of the seat tube. If it is within a mm or two of the CL number calculated above, then chainline is not the problem. If it is not close to the CL number, then you need to purchase a bottom bracket spindle that is different in length of the current BB by twice the amount your CL is off.

For example, if your hub has an O.L.D of 130mm, and the middle of the middle cog is 20mm fromt he drive side locknut, then your chainline is (130mm/2) - 20mm = 45mm.
Then if you measure the distance between the seat tube and the middle chainring and it is 52mm, you need a bottom brackt that is different by:
(45mm-52mm) X 2 = -7mm X 2 = -14mm, or 14mm shorter. If you had a 122m bottom bracket, you would go to the size clostest to 122-14, or 108mm.

As for the 1-3mm above the big ring standard, I usually set the derailleur so it is perfectly parallel with the chainrings when viewed from the top, then pull the derailleur out by hand so the outer edge of the cage is direclty over the big ring, then measure the gap. In my experience you don't need to use a ruler calipers for this - just set it 'real close.' Having the cable attached during this operation just complicates things, IMHO.

GordoTrek

wow, a lot of great responses, thanks for all the help, after re adjusting everything from the start i was able to get it without any noise, i have a 127mm bb, and i guess according to the docs i needed a 123, however its not affecting my derailleur at this point...
i hope im not hurting it, but i don't see how

DCB0

If the BB spindle is 4mm too long, that probably means your chainline is off by 2mm... not a big deal. THe only consequence of this is that the chain will be at a slightly tighter angle between the crank and the cassette when in certain gears, which will increase the rate of chain wear when in those gears.. Avoid cross chaining (no big chainring-biggest 2 or 3 cogs or or small chainring-smallest cog combos) and you should be fine.

whitefiretiger

I just remembered that when I was younger I had a 1-piece crank 15spd bike that the cd never seemed right on and I pulled the crank out and there was a stack of washers between the chainring and cone about 1/2" thick. I pulled one washer out and put it back together and prob solved. Crazy things happen. The craziness part was it had never been serviced and was that way new.