FD won't shift
I bought a used bike and didn't notice on my test ride that the cranks (not OEM) are not centered. Upon inspection, it appeared that the seller had put both 2.5mm spacers on the left side. I moved one spacer over to the drive side as per the crankset's instructions, but then the clamp-on Ultegra FD-6800 wouldn't shift into the big ring even with the limit screws backed off completely and the cable tightened until it barely grazes the inner chainring. What are my options?
FWIW it's an FSA Gossamer Pro Modular AGX+ crankset on a 2016 Diamondback Haanjo Trail. |
Just thinking out loud here: Assuming the 2.5mm spacers are to fit a 68mm BB to a crankset designed for frames with 73mm BB shells? Does your crank fit the BB if there were no spacers? Does the frame have a 73mm BB shell? Just because both spacers were stacked on the NDS, does that necessarily mean the crank isn't centered relative to the frame? Do some manufacturers advise the user to place the spacers that way when fitting cranks made for 73mm BB shells to frames with 68mm BB shells?
|
Did the crank "offset" bother you besides aesthetics? Move the spacer back.
|
"the cranks (not OEM) are not centered" with respect to what? A published chain line dimension?
It seems to me that the spacers placed on the non drive side was done to allow better ft shifting and/or chain line. If the spacer was to be relocated to the ND side again will there be small ring/chainstay clearance? If so than that is your likely solution. For many decades bikes had their crank arms off set to the drive side on purpose and riders didn't die. Andy |
Take it to a shop where somebody who can understand the problem can actually see what the problem is. Or submit some photos.
|
A quick search came up with specs from Bicycle Blue Book
Drivetrain Bottom Bracket BB386 Cassette Shimano CS-5800 105 11spd (11-32t) Chainrings 46/36T Shifters Shimano ST-RS685 Dual Control 11spd Crankset FSA Gossamer Pro Cross Front Derailleur Shimano Ultegra Rear Derailleur Shimano Ultegra So going only by those specs it should have had a 2 piece FSA crank in it. That probably had the correct spindle length. So maybe a previous owner put a different crank and BB in it and didn't quite get the right BB length. Chain line on the GOSSAMER PRO MODULAR AGX+ is 47mm, I suspect that is different from the original crank which is more like a road cranks 43.5 mm chain line. But I didn't see FSA specs for that. |
Originally Posted by Andrew R Stewart
(Post 22718997)
"the cranks (not OEM) are not centered" with respect to what? A published chain line dimension?
It seems to me that the spacers placed on the non drive side was done to allow better ft shifting and/or chain line. If the spacer was to be relocated to the ND side again will there be small ring/chainstay clearance? If so than that is your likely solution. For many decades bikes had their crank arms off set to the drive side on purpose and riders didn't die. Andy |
Originally Posted by tFUnK
(Post 22718790)
Just thinking out loud here: Assuming the 2.5mm spacers are to fit a 68mm BB to a crankset designed for frames with 73mm BB shells?
Originally Posted by tFUnK
(Post 22718790)
Does your crank fit the BB if there were no spacers?
Originally Posted by tFUnK
(Post 22718790)
Just because both spacers were stacked on the NDS, does that necessarily mean the crank isn't centered relative to the frame?
Originally Posted by Andrew R Stewart
(Post 22718997)
"the cranks (not OEM) are not centered" with respect to what? A published chain line dimension?
Originally Posted by Andrew R Stewart
(Post 22718997)
It seems to me that the spacers placed on the non drive side was done to allow better ft shifting and/or chain line. If the spacer was to be relocated to the ND side again will there be small ring/chainstay clearance? If so than that is your likely solution.
For many decades bikes had their crank arms off set to the drive side on purpose and riders didn't die. Andy
Originally Posted by Iride01
(Post 22719177)
So going only by those specs it should have had a 2 piece FSA crank in it. That probably had the correct spindle length. So maybe a previous owner put a different crank and BB in it and didn't quite get the right BB length.
Chain line on the GOSSAMER PRO MODULAR AGX+ is 47mm, I suspect that is different from the original crank which is more like a road cranks 43.5 mm chain line. But I didn't see FSA specs for that. |
Originally Posted by SoSmellyAir
(Post 22719563)
My Cannondale Synapse has a (proprietary) BB30a bottom bracket which is not centered on the center line of the bike frame. Are other bottom brackets necessarily centered? It seems theoretically possible to offset the bottom bracket to the left (or non-drive side) to make room for chain rings but still have a spindle that is centered. An unequal number of spacers on either side of the bottom bracket does not necessarily mean that the spindle is not centered. What matters is that both pedals are equidistant from the center line of the bike frame, right?
Some of us are especially sensitive fitting issues. If a hip continues to be problematic find the fix (which likely what's happening right now), even if it means a different set up. Fitting solutions are not easily done via long distance. Andy |
Presumably, this is a road bike. Yes or no? FSA Gossamer came in two spindle configurations, 24 mm and 30 mm. Which one is it? Bearings for these spindles can be either press-fit or outboard threaded. If it's outboard threaded, is it an FSA bearing or Shimano, because the widths are different.
The purpose of chain line is to establish a kind of neutrality over gear combinations. The innermost and outermost rear cogs need to be equally accessible from the inner and outer front chainrings. The most straightforward way to check this is to lay a yardstick over the space between the chainrings (presuming it's a double) and cog #6 (presuming it's an 11-speed). The point is, you want midpoints. The yardstick should be parallel to the center line of the bike. If it isn't, you have to fiddle with the shims. On a 130 mm axle, the 11-speed cassette moves the chain line about 0.95 mm inboard from 10-speed. It might just be possible that this crank wasn't meant to be used with 11-speed systems. I can't tell because you haven't told us about the bike or shown us photos. But establish the chain line first. Also be aware that Shimano 11-speed front derailleurs use virtually no slack in the cable, unlike previous 8-, 9-, and 10-speed generations. Then there is the matter of the converter pin, whose position is determined by the pull angle of the cable as it emerges behind the bottom bracket. |
Originally Posted by oldbobcat
(Post 22719668)
Presumably, this is a road bike. Yes or no? FSA Gossamer came in two spindle configurations, 24 mm and 30 mm. Which one is it? Bearings for these spindles can be either press-fit or outboard threaded. If it's outboard threaded, is it an FSA bearing or Shimano, because the widths are different.
Originally Posted by oldbobcat
(Post 22719668)
The purpose of chain line is to establish a kind of neutrality over gear combinations. The innermost and outermost rear cogs need to be equally accessible from the inner and outer front chainrings. The most straightforward way to check this is to lay a yardstick over the space between the chainrings (presuming it's a double) and cog #6 (presuming it's an 11-speed). The point is, you want midpoints. The yardstick should be parallel to the center line of the bike. If it isn't, you have to fiddle with the shims. On a 130 mm axle, the 11-speed cassette moves the chain line about 0.95 mm inboard from 10-speed. It might just be possible that this crank wasn't meant to be used with 11-speed systems. I can't tell because you haven't told us about the bike or shown us photos. But establish the chain line first.
Originally Posted by oldbobcat
(Post 22719668)
Also be aware that Shimano 11-speed front derailleurs use virtually no slack in the cable, unlike previous 8-, 9-, and 10-speed generations. Then there is the matter of the converter pin, whose position is determined by the pull angle of the cable as it emerges behind the bottom bracket.
|
"Also be aware that Shimano 11-speed front derailleurs use virtually no slack in the cable, unlike previous 8-, 9-, and 10-speed generations. Then there is the matter of the converter pin, whose position is determined by the pull angle of the cable as it emerges behind the bottom bracket."
This! When this design series of ft ders is set up well they do shift really fast and with "authority". But that set up window is complex and narrow. Even after a few dozen examples crossing my repair stand I find myself doing far more fiddling with them than more traditionally designed ders. I would personally not run one if I could help it, (wait I can help it and I don't use these. The big reason is that I stopped my gearing count grail at 9x3 and these ders don't work on a triple or the wider 9 spd chain.) Andy |
Originally Posted by urbanknight
(Post 22719635)
Originally Posted by Iride01 View Post So going only by those specs it should have had a 2 piece FSA crank in it. That probably had the correct spindle length. So maybe a previous owner put a different crank and BB in it and didn't quite get the right BB length. Chain line on the GOSSAMER PRO MODULAR AGX+ is 47mm, I suspect that is different from the original crank which is more like a road cranks 43.5 mm chain line. But I didn't see FSA specs for that. Yeah, that's what I suspect. Just wasn't sure if there was a way to correct it. When you stand behind the bike and look from the center of the rear stack of cogs then when do they appear to be lined up more with the center of the front stack? When where the previous owner had it or when you made your adjustment? Happy T-Day! |
Originally Posted by Iride01
(Post 22720116)
Well it seems a previous owner corrected the chain line somewhat by putting the spacers on the left side of the BB shell. The Ultegra front DR is for a road crank and expects a road chain line. So weren't the spacers on the left side giving that crank made for a wider chain line about the correct chain line for that bike, what ever that is.
When you stand behind the bike and look from the center of the rear stack of cogs then when do they appear to be lined up more with the center of the front stack? When where the previous owner had it or when you made your adjustment? Happy T-Day! I'll have to look at it when I get back to it. |
Originally Posted by urbanknight
(Post 22720151)
That's what made me wonder if a simple fix would be getting a MTB derailleur, or even a different crankset since I prefer a different length anyway. But I also hate doing bottom brackets, so I'd want to get one compatible with the one that's installed already :lol:
I'll have to look at it when I get back to it. The solution to your problem is to swap the spacer back. It worked, why not just live with it? |
Originally Posted by cyccommute
(Post 22720176)
It worked, why not just live with it?
seriously though, I already moved the spacer back and will just use my OCD angst to pedal harder or something. |
Originally Posted by urbanknight
(Post 22720151)
That's what made me wonder if a simple fix would be getting a MTB derailleur, or even a different crankset since I prefer a different length anyway. But I also hate doing bottom brackets, so I'd want to get one compatible with the one that's installed already :lol:
I'll have to look at it when I get back to it. Going back to your original post, it seems you had a bike that shifted properly but you didn't like the asymmetry of two spacers on the non-drive side, so you made it symmetrical and now the bike won't shift. So it seems that the guy who installed the crankset knew what he was doing. And If you want the bike to shift again, all you have to do is move the spacer back. Look, the purpose of the spacers is to resolve the chain line, not change your pedaling dynamics. If the chain line doesn't work, the bike doesn't work. By the way, is your front derailleur band-mount or direct-mount? |
just a couple weeks ago did a quick scan for some GRX stuff (including 810 crank) on the QBP site and saw a lot of zeroes ... out of stock
|
When I did a quick glance at the FSA Gossamer Pro Modular AGX+ crank, I thought it was a three piece crank. But now I realize it too is a 2 piece crank. But it's made for wider BB shells and chain lines of what gravel bikes of late have been going to.
GRX cranks have that same 47 mm chain line. So going to GRX isn't necessarily going to do anything for you if your rear expects a chain line more typical of a road bike. So while a GRX FDR might give you the swing you need to reach the rings with the symmetrically spaced crankarm on both sides, then you still might have less than great shifting in some combos. Seems the bigger issue is going to require you change the crank to something that want's that narrower chain line. https://shop.fullspeedahead.com/en/f...ab79e2de27645/ https://shop.fullspeedahead.com/en/f...c298e69684883/ https://shop.fullspeedahead.com/en/f...847f3c9e4e882/ |
Originally Posted by oldbobcat
(Post 22720194)
You don't want to open another can of worms with MTB derailleur compatibility with your STI levers. I'd recommend chucking the whole 6800/FSA mix and buy a full GRX kit before you go throwing in MTB components.
Originally Posted by oldbobcat
(Post 22720194)
So it seems that they guy who installed the crankset knew what he was doing.
Originally Posted by oldbobcat
(Post 22720194)
By the way, is your front derailleur band-mount or direct-mount?
I will do as many of you suggested and run it with both spacers on the NDS. I didn't even notice it until I felt the play from the missing wave washer and went to inspect the problem. |
Originally Posted by Iride01
(Post 22720248)
When I did a quick glance at the FSA Gossamer Pro Modular AGX+ crank, I thought it was a three piece crank. But now I realize it too is a 2 piece crank. But it's made for wider BB shells and chain lines of what gravel bikes of late have been going to.
GRX cranks have that same 47 mm chain line. So going to GRX isn't necessarily going to do anything for you if your rear expects a chain line more typical of a road bike. So while a GRX FDR might give you the swing you need to reach the rings with the symmetrically spaced crankarm on both sides, then you still might have less than great shifting in some combos. Seems the bigger issue is going to require you change the crank to something that want's that narrower chain line. It looks like the Omega AGX might have what I need, but can't seem to find a manual or documents to support it. |
Originally Posted by urbanknight
(Post 22720320)
Band |
Originally Posted by oldbobcat
(Post 22720520)
On another forum I found some concern that the band mount unit doesn't reach as far as the direct mount. But I don't know if there's anything you can do about it. Anyway, good on you for figuring out the wavy washer.
|
Originally Posted by urbanknight
(Post 22720521)
Guess I could get a direct mount FD and an adapter, but I really should just ride it and see if it even bothers me beyond vanity.
Case in point. Years ago I did some work on a Cervelo with FSA cranks with a 24mm spindle. The owner had replaced the threaded outboard BB bearings with Shimano, a deceptively smart move because Shimano are less expensive and more durable. But the Shimano bearings were about 1-2 mm wider than FSA. While the spindle was long enough to clamp the left crank properly, the drivetrain was never happy cross-chaining from the big ring. Big-big was impossible, and shifting to the big ring from cogs 2-3 in back was hit-or-miss. |
All times are GMT -6. The time now is 09:06 AM. |
Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.