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Help! Front Derailleur Chain Rub

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Help! Front Derailleur Chain Rub

Old 06-27-09, 09:34 PM
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ModeratedUser06022019
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Help! Front Derailleur Chain Rub

As a part of my bike build, i'm trying to convert the 3x7 speed drivetrain on my Jamis Trail X2 to a 3x9 speed drivetrain.

did the following:

- replaced generic 7 speed cassette with Shimano HG50 cassette
- new SRAM 951 chain
- replaced Shimano Acera rear derailleur with a Shimano Deore RD-M510
- replaced Shimano TZ-30 front derailleur with a Shimano Deore FD-M531

however, i'm having trouble

the rear is working beautifully, but the front has been an ongoing nightmare

i did the best i can so far to adjust the front derailleur
the chain rubs against the chain guide in the following manner:

1+1: severe on the outside chainguide
1+2: moderately on the outside chainguide
1+3: slightly on outside chain guide
1+4: OK
1+5: OK
1+6: OK
1+7: OK
1+8: OK
1+9: slightly on the inside chain guide

2+1: moderately on the outside chain guide
2+2: slightly on the outside chain guide
2+3: OK
2+4: OK
2+5: OK
2+6: OK
2+7: slightly-moderatey on the inside chain guide
2+8: moderately on the inside chain guide
2+9: moderately-severely on the inside chain guide

3+1: very slightly on outside chain guide
3+2: OK
3+3: OK
3+4: OK
3+5: very slightly on inside chain guide
3+6: slightly on inside chain guide
3+7: moderatey on the inside chain guide
3+8: severely on the inside chain guide
3+9: severely on the inside chain guide

Could it be that i'm running a mystery crank? (i was told when i bought it last year that it would work with 9-speed systems)

Perhaps the derailleur is not parallel?

Any help is appreciated!

Last edited by ModeratedUser06022019; 06-27-09 at 09:52 PM.
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Old 06-28-09, 05:35 AM
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Have a look at your rear wheel to see if it is centered behind the seatpost. If it is off, then you may have to redish your wheel, since it is an aluminum frame and your sporting a quick release axle.
The fd should clear the big ring by 3mm, and check for any parallel issues.If you move the fd, then you should reset the cable tension and limit screws.
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Old 06-28-09, 06:32 AM
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You didn't list shifters...what'd ya get?
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Old 06-28-09, 06:54 AM
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Assuming you checked the rear wheel to assure the dish is correct (centered) as qurry suggested, next I'd check you limit screws. Have you backed off sufficiently to prevent rubbing?
BTW, I wouldn't worry about chain rub when you are cross-chaining. You should never ride in those modes.
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Old 06-28-09, 08:28 AM
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Originally Posted by gurry View Post
Have a look at your rear wheel to see if it is centered behind the seatpost. If it is off, then you may have to redish your wheel, since it is an aluminum frame and your sporting a quick release axle.

Yeah its centered pretty well.

Originally Posted by chelboed View Post
You didn't list shifters...what'd ya get?
Well i broke my deore 3sp shifter, (the end of the stop popped out of the housing and i didnt notice, and i tried to shift up.. and *SNAP*)
so i replaced it with something the shop gave me, markings say SL-MG40, indexing appears to be the same as the deore

Originally Posted by roccobike View Post
Assuming you checked the rear wheel to assure the dish is correct (centered) as qurry suggested, next I'd check you limit screws. Have you backed off sufficiently to prevent rubbing?
BTW, I wouldn't worry about chain rub when you are cross-chaining. You should never ride in those modes.
Yeah i have been pretty liberal with the limit screws, and no i never use "cross chained" ratios lol. its just annoying when i have a new bike with these odd quirks


i did another tune and this time it seems to be a bit better, before this i didnt do a proper adjustment for the intermediate chainwheel

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Old 06-28-09, 11:01 AM
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When you set the inside limit (for the granny ring) try doing it with the FD cable unattatched. Then with the FD and shifter in the granny position, pull the cable just tight enough to take out all the slack, then anchor the cable.

FD's can be finicky to adjust/set up.

Also you can go to Park Tool and get some tutorial.

Edit: Make sure you back out the FD shifter's barrel adjuster a couple turns before you anchor the cable so that you will be able to fine tune the indexing on the middle ring. Remember that the barrel adjuster is only for the middle ring.
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Last edited by kenhill3; 06-28-09 at 11:07 AM.
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Old 06-28-09, 01:03 PM
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Oh yeah, something i left out, i think my bottom bracket is too short

originally it was too long (122.5mm) then i put in one that was shorter but it turned out to be too short (111mm) the smallest chainwheel was way too close to the seatpost, I couldn't set the low limit because it was already at the mechanical limit which was too far out, so I "shifted" the bottom bracker out further by screwing the "loose" end of the bottom bracket in a bit further, put te cartridge back in and tried it again, this time it shifted better but still sketchy. So i think i need a properly sized bottom bracket.

now that I look at the 9-speed Jamis hardtails like the Durrango 2, i notice they use a 118mm bottom bracket.

Also, is it possible to have a square taper crank compatible with 9-speed systems?
or do they have to be octalink with deore or better cranksets?
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Old 06-28-09, 10:57 PM
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Originally Posted by efm-7 View Post
Oh yeah, something i left out, i think my bottom bracket is too short

originally it was too long (122.5mm) then i put in one that was shorter but it turned out to be too short (111mm) the smallest chainwheel was way too close to the seatpost, I couldn't set the low limit because it was already at the mechanical limit which was too far out, so I "shifted" the bottom bracker out further by screwing the "loose" end of the bottom bracket in a bit further, put te cartridge back in and tried it again, this time it shifted better but still sketchy. So i think i need a properly sized bottom bracket.

now that I look at the 9-speed Jamis hardtails like the Durrango 2, i notice they use a 118mm bottom bracket.

Also, is it possible to have a square taper crank compatible with 9-speed systems?
or do they have to be octalink with deore or better cranksets?
Spindle length is specific to the crank on square tapers, so who knows what you've done going from an extreme of 122.5 to 111. Just crazy.
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Old 06-29-09, 10:38 AM
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Crazy indeed! definitely been a hard learning experience, makes me appreciate pre-built bikes, but they don't make anything in my size with anything other than department-store-level components.

well, im gonna try 118, and then 113, and give up after those, maybe go to an octalink system with a deore crank
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Old 06-30-09, 04:47 PM
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alright so 118 failed, chain was riding up the biggest chainwheel because it wasnt within stretchable limits of the chain. (the edge of the inner links of the chain were on the teeth)

tried 115, better, now the bike is ridable! i can use 8 of the 9 while using the middle chainwheel,
still kinda sketchy on the large-large/small small combo but like everyone says, it's never used.
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Old 06-30-09, 08:11 PM
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I may be wrong, but the most common BB spindle seems to be 113.
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Old 07-01-09, 02:03 PM
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yeah. i do get the hunch that 115 is still on the longer side. but i think i will leave it for now. ill try 113 if it starts to bothers me a lot
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