If you have any questions, please use the BikeGremlin forum (I try to respond to every comment, but UA-cam sucks at notifications, especially when it comes to any follow-up questions): www.bikegremlin.net/ Relja
Hi, I am building my first custom. And it is funny to see how everyone (frame manufacturer, BB and crankset) are trying to shift responsibility for the chainline to each other. It is a pretty common Cannondale Supersix EVO Generation 3 frame. The front chainline is stipulated to be road standard (43.5mm), the crankset is a Praxis Doon and is stipulated to be 44.5m (unsure how they come up with the number, probably if used with their BB). I awkwardly and with a great trouble measured the front chainline to be 42mm. The Wheels Manufacturing PF30a BB that I bought only comes with 3mm worth of spacers and I had all of them installed at the driveside. Looks like I need even more spacers to bring it up to a standard, which is a bit odd. At the same time, the rear chainline measures 47.5mm which is even further out... However, if I pull a straight string fromt in between the two front chainrings to the cassette it currently lands around the middle of the cassette, which should not be the case, it should end up around 5mm inwards. Very strange. I doublechecked all the measurements several times. Any advice? Thanks PS I tried a simpler measurement method for the front chainline: I measured from the bottle mount bolt which appears to be centrered to the inner edge of the small and large chainrings, added two numbers and dvided by two, than subtracted half of one chainring thickness. It equated to 43.5mm road standard, but it still does not explain the discrepancy between front and rear.
For comments, questions, or advice, I’d be happy to help over on the BikeGremlin forum: www.bikegremlin.net/ To keep everything organized, I’m only providing answers there. Thank you for understanding! Relja Novović
I have been working on my vintage road bike from the early 80's that i have not rode for many years until recently. When i was young i rode the largest chainring most of the time and never noticed the chain rubbing. Today, i to ride on the 42 tooth chainring mostly and i hear chain rub and wondering if this is a chain line issue. Not sure if age is made me more fussy or if there always some chain rub to be expected.
I was always told to use the front small chain ring with the largest gears on the rear cassette and then if i was using the large front to then use the smaller rear cassette rings that way the chain stays straight ❤
If the rear chainstays were parallel to the bike's centre-line, that could work OK(ish). Since they aren't, you can only reliably tell if the chainline is waaay off or not, but you can't tell if it's "only" 2-4 mm off. Combined with short chainstays on most modern bikes, that's still enough to make the chain rub or drop more easily (and get more component wear) in certain gear combinations. Now, a steel rod or a ruler that's not flexible - that works better than just eyeballing it, at least when you get the chain and the front derailleur out of the way. Relja
If you have any questions, please use the BikeGremlin forum (I try to respond to every comment, but UA-cam sucks at notifications, especially when it comes to any follow-up questions):
www.bikegremlin.net/
Relja
Thank you very much for the article and video. He helped me set the correct chain line on my bike.
You always have the best explanations.
Hi, I am building my first custom. And it is funny to see how everyone (frame manufacturer, BB and crankset) are trying to shift responsibility for the chainline to each other. It is a pretty common Cannondale Supersix EVO Generation 3 frame. The front chainline is stipulated to be road standard (43.5mm), the crankset is a Praxis Doon and is stipulated to be 44.5m (unsure how they come up with the number, probably if used with their BB). I awkwardly and with a great trouble measured the front chainline to be 42mm. The Wheels Manufacturing PF30a BB that I bought only comes with 3mm worth of spacers and I had all of them installed at the driveside. Looks like I need even more spacers to bring it up to a standard, which is a bit odd. At the same time, the rear chainline measures 47.5mm which is even further out... However, if I pull a straight string fromt in between the two front chainrings to the cassette it currently lands around the middle of the cassette, which should not be the case, it should end up around 5mm inwards. Very strange. I doublechecked all the measurements several times. Any advice? Thanks
PS I tried a simpler measurement method for the front chainline: I measured from the bottle mount bolt which appears to be centrered to the inner edge of the small and large chainrings, added two numbers and dvided by two, than subtracted half of one chainring thickness. It equated to 43.5mm road standard, but it still does not explain the discrepancy between front and rear.
For comments, questions, or advice, I’d be happy to help over on the BikeGremlin forum:
www.bikegremlin.net/
To keep everything organized, I’m only providing answers there. Thank you for understanding!
Relja Novović
Very good explanation thank you 🙏
Many thx for such informative explanation! Grate Video!!!
Care svaka čast za ovo!
Perfect explanation! Thank you!
I have been working on my vintage road bike from the early 80's that i have not rode for many years until recently. When i was young i rode the largest chainring most of the time and never noticed the chain rubbing. Today, i to ride on the 42 tooth chainring mostly and i hear chain rub and wondering if this is a chain line issue. Not sure if age is made me more fussy or if there always some chain rub to be expected.
I was always told to use the front small chain ring with the largest gears on the rear cassette and then if i was using the large front to then use the smaller rear cassette rings that way the chain stays straight ❤
Klasse T-Shirt😂😂😂
Cant you just use your eyes to look down the chain line to see if its in the correct place?
If the rear chainstays were parallel to the bike's centre-line, that could work OK(ish).
Since they aren't, you can only reliably tell if the chainline is waaay off or not, but you can't tell if it's "only" 2-4 mm off. Combined with short chainstays on most modern bikes, that's still enough to make the chain rub or drop more easily (and get more component wear) in certain gear combinations.
Now, a steel rod or a ruler that's not flexible - that works better than just eyeballing it, at least when you get the chain and the front derailleur out of the way.
Relja