Road bike chain line issue
Discussion
My girlfriend is now riding my old 2008 (ish) Giant TCR Alliance Zero, and I've made a few changes to it to fit and suit her better including bringing the fairly brutal gear ratios down a bit.
It's running 2x10 SRAM Rival and a GXP BB. It was originally 53-39 on a 130 BCD 172.5 chainset, with 12-25 at the back. Firstly I swapped the cassette to a SRAM 11-28 which I'd had in the spares box, it had done about 100 miles on one hilly sportive, and all was well when I fitted it and we ran it with the 53-39 for a while. I then found a NOS (new old stock) Rival Compact chainset on eBay (50-34 110 BCD) and fitted it last night, along with a brand new SRAM 10 speed chain.
However, I now have really bad chain rub on the inside edge of the big ring, when running small ring to the smallest 3 or so sprockets on the cassette. Running small to small, the chain is almost trying to shift onto the big ring occasionally. Of course, I'd never run small to small, but with my girlfriend being a novice cyclist it would be better if the drivetrain would at least put up with this occasionally without trying to tear itself apart!
It looks as if I either want to somehow move the chainset out, or move the cassette in towards the centreline is possible...however I don't think there's any scope to do this, unless I somehow remove the spacer that goes between the cassette and freehub body, and compensate by adding a spacer between the small cog and the lock ring...but I don't think this is "normal".
I can't really find any technical data on the chainline of the new chainset, but as they are both SRAM Rival, 10 speed, GXP BB, I would have hoped it would be a straight swap.
Is there any way to resolve this? Thanks in advance!
It's running 2x10 SRAM Rival and a GXP BB. It was originally 53-39 on a 130 BCD 172.5 chainset, with 12-25 at the back. Firstly I swapped the cassette to a SRAM 11-28 which I'd had in the spares box, it had done about 100 miles on one hilly sportive, and all was well when I fitted it and we ran it with the 53-39 for a while. I then found a NOS (new old stock) Rival Compact chainset on eBay (50-34 110 BCD) and fitted it last night, along with a brand new SRAM 10 speed chain.
However, I now have really bad chain rub on the inside edge of the big ring, when running small ring to the smallest 3 or so sprockets on the cassette. Running small to small, the chain is almost trying to shift onto the big ring occasionally. Of course, I'd never run small to small, but with my girlfriend being a novice cyclist it would be better if the drivetrain would at least put up with this occasionally without trying to tear itself apart!
It looks as if I either want to somehow move the chainset out, or move the cassette in towards the centreline is possible...however I don't think there's any scope to do this, unless I somehow remove the spacer that goes between the cassette and freehub body, and compensate by adding a spacer between the small cog and the lock ring...but I don't think this is "normal".
I can't really find any technical data on the chainline of the new chainset, but as they are both SRAM Rival, 10 speed, GXP BB, I would have hoped it would be a straight swap.
Is there any way to resolve this? Thanks in advance!
Hard-Drive said:
My girlfriend is now riding my old 2008 (ish) Giant TCR Alliance Zero, and I've made a few changes to it to fit and suit her better including bringing the fairly brutal gear ratios down a bit.
It's running 2x10 SRAM Rival and a GXP BB. It was originally 53-39 on a 130 BCD 172.5 chainset, with 12-25 at the back. Firstly I swapped the cassette to a SRAM 11-28 which I'd had in the spares box, it had done about 100 miles on one hilly sportive, and all was well when I fitted it and we ran it with the 53-39 for a while. I then found a NOS (new old stock) Rival Compact chainset on eBay (50-34 110 BCD) and fitted it last night, along with a brand new SRAM 10 speed chain.
However, I now have really bad chain rub on the inside edge of the big ring, when running small ring to the smallest 3 or so sprockets on the cassette. Running small to small, the chain is almost trying to shift onto the big ring occasionally. Of course, I'd never run small to small, but with my girlfriend being a novice cyclist it would be better if the drivetrain would at least put up with this occasionally without trying to tear itself apart!
It looks as if I either want to somehow move the chainset out, or move the cassette in towards the centreline is possible...however I don't think there's any scope to do this, unless I somehow remove the spacer that goes between the cassette and freehub body, and compensate by adding a spacer between the small cog and the lock ring...but I don't think this is "normal".
I can't really find any technical data on the chainline of the new chainset, but as they are both SRAM Rival, 10 speed, GXP BB, I would have hoped it would be a straight swap.
Is there any way to resolve this? Thanks in advance!
Don’t run small to small or big to big. There are other suitable chainring - sprocket combos, which will give you a very similar ratio, without the extreme small-small big-big. The electronic shift groupsets can be set with custom shifts / synchro shifts so that this is calculated and the mechs move accordingly to give the requisite ratio. With a mechanical group set, you have to work it out yourself, and click the levers accordingly, but the end result is the same.It's running 2x10 SRAM Rival and a GXP BB. It was originally 53-39 on a 130 BCD 172.5 chainset, with 12-25 at the back. Firstly I swapped the cassette to a SRAM 11-28 which I'd had in the spares box, it had done about 100 miles on one hilly sportive, and all was well when I fitted it and we ran it with the 53-39 for a while. I then found a NOS (new old stock) Rival Compact chainset on eBay (50-34 110 BCD) and fitted it last night, along with a brand new SRAM 10 speed chain.
However, I now have really bad chain rub on the inside edge of the big ring, when running small ring to the smallest 3 or so sprockets on the cassette. Running small to small, the chain is almost trying to shift onto the big ring occasionally. Of course, I'd never run small to small, but with my girlfriend being a novice cyclist it would be better if the drivetrain would at least put up with this occasionally without trying to tear itself apart!
It looks as if I either want to somehow move the chainset out, or move the cassette in towards the centreline is possible...however I don't think there's any scope to do this, unless I somehow remove the spacer that goes between the cassette and freehub body, and compensate by adding a spacer between the small cog and the lock ring...but I don't think this is "normal".
I can't really find any technical data on the chainline of the new chainset, but as they are both SRAM Rival, 10 speed, GXP BB, I would have hoped it would be a straight swap.
Is there any way to resolve this? Thanks in advance!
Have you got the spacers on the crank axle in the right place? there are different combinations depending on the BB width and axle length. Might need a wider spacer on the drive side to bring the crank out a bit. have a read of this:
https://www.sram.com/globalassets/document-hierarc...
https://www.sram.com/globalassets/document-hierarc...
BrundanBianchi said:
Hard-Drive said:
My girlfriend is now riding my old 2008 (ish) Giant TCR Alliance Zero, and I've made a few changes to it to fit and suit her better including bringing the fairly brutal gear ratios down a bit.
It's running 2x10 SRAM Rival and a GXP BB. It was originally 53-39 on a 130 BCD 172.5 chainset, with 12-25 at the back. Firstly I swapped the cassette to a SRAM 11-28 which I'd had in the spares box, it had done about 100 miles on one hilly sportive, and all was well when I fitted it and we ran it with the 53-39 for a while. I then found a NOS (new old stock) Rival Compact chainset on eBay (50-34 110 BCD) and fitted it last night, along with a brand new SRAM 10 speed chain.
However, I now have really bad chain rub on the inside edge of the big ring, when running small ring to the smallest 3 or so sprockets on the cassette. Running small to small, the chain is almost trying to shift onto the big ring occasionally. Of course, I'd never run small to small, but with my girlfriend being a novice cyclist it would be better if the drivetrain would at least put up with this occasionally without trying to tear itself apart!
It looks as if I either want to somehow move the chainset out, or move the cassette in towards the centreline is possible...however I don't think there's any scope to do this, unless I somehow remove the spacer that goes between the cassette and freehub body, and compensate by adding a spacer between the small cog and the lock ring...but I don't think this is "normal".
I can't really find any technical data on the chainline of the new chainset, but as they are both SRAM Rival, 10 speed, GXP BB, I would have hoped it would be a straight swap.
Is there any way to resolve this? Thanks in advance!
Don’t run small to small or big to big. There are other suitable chainring - sprocket combos, which will give you a very similar ratio, without the extreme small-small big-big. The electronic shift groupsets can be set with custom shifts / synchro shifts so that this is calculated and the mechs move accordingly to give the requisite ratio. With a mechanical group set, you have to work it out yourself, and click the levers accordingly, but the end result is the same.It's running 2x10 SRAM Rival and a GXP BB. It was originally 53-39 on a 130 BCD 172.5 chainset, with 12-25 at the back. Firstly I swapped the cassette to a SRAM 11-28 which I'd had in the spares box, it had done about 100 miles on one hilly sportive, and all was well when I fitted it and we ran it with the 53-39 for a while. I then found a NOS (new old stock) Rival Compact chainset on eBay (50-34 110 BCD) and fitted it last night, along with a brand new SRAM 10 speed chain.
However, I now have really bad chain rub on the inside edge of the big ring, when running small ring to the smallest 3 or so sprockets on the cassette. Running small to small, the chain is almost trying to shift onto the big ring occasionally. Of course, I'd never run small to small, but with my girlfriend being a novice cyclist it would be better if the drivetrain would at least put up with this occasionally without trying to tear itself apart!
It looks as if I either want to somehow move the chainset out, or move the cassette in towards the centreline is possible...however I don't think there's any scope to do this, unless I somehow remove the spacer that goes between the cassette and freehub body, and compensate by adding a spacer between the small cog and the lock ring...but I don't think this is "normal".
I can't really find any technical data on the chainline of the new chainset, but as they are both SRAM Rival, 10 speed, GXP BB, I would have hoped it would be a straight swap.
Is there any way to resolve this? Thanks in advance!
itsnotarace said:
Shimano left shifters have a hidden click that allows you to offset the front derailleur to an intermediate position to alleviate this, pushing further results in a full shift to the big ring. Don't know if SRAM do similar
If not, don't cross chain
The chain rub is on the inside of the big ring, it's nothing to do with the front mech. I could remove the front mech entirely and it would make no difference.If not, don't cross chain
lufbramatt said:
Have you got the spacers on the crank axle in the right place? there are different combinations depending on the BB width and axle length. Might need a wider spacer on the drive side to bring the crank out a bit. have a read of this:
https://www.sram.com/globalassets/document-hierarc...
Yeah, I had a look at this, and the plot thickens due to the fact that for years SRAM was sending out duff information. Apparently you should only use those spacers on a 68mm BB is you are fitting an MTB crank, which obviously isn't Rival!https://www.sram.com/globalassets/document-hierarc...
There seem to be some cases of people sorting this issue by fitting one spacer on the drive side, although it then puts a higher lateral force on the BB bearing which wears it out quicker. TBH for a leisure rider I'm willing to take this route, however it won't be ideal if the BB explodes 20 miles from home...
Took it all apart and checked EVERTHING. Cassette assembly, axle in dropout alignment, BB torque, crank torque, and every measurement between the old and new axle. All seals etc present and correct. The distance between the teeth on the big ring to the frame is identical, so it's obviously running the same chainline.
Annoyingly, the old (stretched) chain is now in the bin and gone...the only thing I can think of it that somehow the old and new chain are very slightly different. The old one was a SRAM1051 and the new one a SRAM1031. On some (not all) websites the 1051 is shown as "recommended for Force/Rival/Apex" however they are both shown as 10 speed road compatible chains.
I could try a 1051, or put some 0.6mm chainring spacers between the spider and the big ring...any thoughts?
Annoyingly, the old (stretched) chain is now in the bin and gone...the only thing I can think of it that somehow the old and new chain are very slightly different. The old one was a SRAM1051 and the new one a SRAM1031. On some (not all) websites the 1051 is shown as "recommended for Force/Rival/Apex" however they are both shown as 10 speed road compatible chains.
I could try a 1051, or put some 0.6mm chainring spacers between the spider and the big ring...any thoughts?
Surely it's a case that the inner (smaller) front ring is that bit smaller than the old one so the amount of the outer (larger) front ring visible is greater, therefore when running small to small (tsk tsk) the chain has starts has more of the outer ring to negotiate it's way cleanly past which it can't do.
Possibly spacers between the outer and inner front rings may help, or a larger inner ring (which defeats your intention) but probably the easiest and most sensible solution is not to use the bottom 3 or 4 gears when on the little front ring.
Possibly spacers between the outer and inner front rings may help, or a larger inner ring (which defeats your intention) but probably the easiest and most sensible solution is not to use the bottom 3 or 4 gears when on the little front ring.
Marcellus said:
Surely it's a case that the inner (smaller) front ring is that bit smaller than the old one so the amount of the outer (larger) front ring visible is greater, therefore when running small to small (tsk tsk) the chain has starts has more of the outer ring to negotiate it's way cleanly past which it can't do.
Possibly spacers between the outer and inner front rings may help, or a larger inner ring (which defeats your intention) but probably the easiest and most sensible solution is not to use the bottom 3 or 4 gears when on the little front ring.
I was thinking about this, however when viewed from above the chain should be meshing with the small ring in the same place, only just slightly behind top dead centre as it were...everything behind the axle is fairly irrelevant. Also, although the small ring has gone from a 39 to a 34, the big ring has also gone from a 53 to a 50 (although I guess the small ring is 5 teeth smaller, where the big ring is only 3 teeth smaller....)Possibly spacers between the outer and inner front rings may help, or a larger inner ring (which defeats your intention) but probably the easiest and most sensible solution is not to use the bottom 3 or 4 gears when on the little front ring.
it's all to do with the circumference of the rings not necessarily the number of teeth (yes of course one creates the other) a 34 is quit a bit smaller than a 39 and to me looks to be a bigger difference between a 53 to 50.
I'm not at home atm so can't check but if you've still got the 53:39 then measure the gap from the tip of the 39teeth to the tip of th 53 teeth and compare that measurement with the 50:34 I'm almost certain it'll be smaller on the 53:39.
I might not be explaining this very well, the chain will leave the ring front at top and from there is trying to go to the top of the rear ring but there's more of the 50 ring to negotiate it's way past before it can go in a straight line from front to rear.
on the 53:39 it's less noticable but on the 50:34 it's enough to catch on the 50 to try and engage it.
I'm not at home atm so can't check but if you've still got the 53:39 then measure the gap from the tip of the 39teeth to the tip of th 53 teeth and compare that measurement with the 50:34 I'm almost certain it'll be smaller on the 53:39.
I might not be explaining this very well, the chain will leave the ring front at top and from there is trying to go to the top of the rear ring but there's more of the 50 ring to negotiate it's way past before it can go in a straight line from front to rear.
on the 53:39 it's less noticable but on the 50:34 it's enough to catch on the 50 to try and engage it.
Thanks Marcellus. I’m all sorted now...fitted some 0.6mm CNC chainring spacers between the inner edge of the big ring and the crank spider. There’s a teeny weeny murmur of rub on small to small, but it’s just a gentle reminder to stop cross chaining rather than the drivetrain pulling itself to bits! Interestingly you now need to use the front mech “trim” (which is on the small ring on SRAM Rival, not the big one as per my Shimano 105) when on the old chainset it wasn’t really required. I suspect it’s all to do with sticking a much bigger cassette and smaller chainset compared to what the frame was designed to do, but at least it’s perfectly useable for the other half now until she decides to upgrade to a new bike!
Thanks all for the input.
Thanks all for the input.
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