Tiagra square taper = chanring teeth total difference

Yesterday i pulled my Tiagra square taper crankset off a frame. i noticed that the Tiagra crank has an inner third chainring capability. i checked it against an old school Shimano triple and saw that the Tiagra will accept a 24 teeth inner chainring. if i were to put that 24 teeth ring on that's be a 52, 42, 24 set. That's 28 teeth difference right there. If I use it with a 12 - 32 rear cogset thats another 20 teeth. That's a total of 48 teeth of chain to wrap. Will an Acera long cage rear derailler handle that (not the one with oversize pulleys)? Will an old school Deore front derailler handle that 28 teeth chainring difference? what can i expect in front shifting? Good, acceptable or poor? BTW, it'd be with 9-speed dura Ace bar end shifters in friction mode.

Thanks and cheers

On 27/12/15 22:07, Sir Ridesalot wrote:
Yesterday i pulled my Tiagra square taper crankset off a frame. i
noticed that the Tiagra crank has an inner third chainring
capability. i checked it against an old school Shimano triple and saw
that the Tiagra will accept a 24 teeth inner chainring. if i were to
put that 24 teeth ring on that's be a 52, 42, 24 set. That's 28 teeth
difference right there. If I use it with a 12 - 32 rear cogset thats
another 20 teeth. That's a total of 48 teeth of chain to wrap. Will
an Acera long cage rear derailler handle that (not the one with
oversize pulleys)? Will an old school Deore front derailler handle
that 28 teeth chainring difference? what can i expect in front
shifting? Good, acceptable or poor? BTW, it'd be with 9-speed dura
Ace bar end shifters in friction mode.

Thanks and cheers

Won't the issue will be the throw of the front derailleur?

On Sun, 27 Dec 2015 14:07:54 -0800 (PST), Sir Ridesalot
wrote:

Yesterday i pulled my Tiagra square taper crankset off a frame. i noticed that the Tiagra crank has an inner third chainring capability. i checked it against an old school Shimano triple and saw that the Tiagra will accept a 24 teeth inner chainring. if i were to put that 24 teeth ring on that's be a 52, 42, 24 set. That's 28 teeth difference right there. If I use it with a 12 - 32 rear cogset thats another 20 teeth. That's a total of 48 teeth of chain to wrap. Will an Acera long cage rear derailler handle that (not the one with oversize pulleys)? Will an old school Deore front derailler handle that 28 teeth chainring difference? what can i expect in front shifting? Good, acceptable or poor? BTW, it'd be with 9-speed dura Ace bar end shifters in friction mode.

Thanks and cheers
I have a 52-42-24 set and it shifts OK but extreme combinations (24
front, 13 back) are best avoided. You can do this with no problems,
just all combinations on a stand. You may have to avoid just 1 or 2.

Your Tiagra crank has a 74mm bcd for the inner chainring. Before the current Shimano nonsense of using a 96mm bcd on triple cranks which limit the small ring to 30 teeth. I have a bike with Campagnolo using 52-42-24 rings and 13-28 cassette and triple front derailleur. I only use the inner 24 ring with the biggest 2-3-4 cogs. Never anything else. I suspect your bike would work fine if you just use the inner ring with the biggest few cogs. I'd advise making the chain long enough to go over big-big combination just in case, even if you never plan to use that combo.




On Sunday, December 27, 2015 at 4:07:56 PM UTC-6, Sir Ridesalot wrote:
Yesterday i pulled my Tiagra square taper crankset off a frame. i noticed that the Tiagra crank has an inner third chainring capability. i checked it against an old school Shimano triple and saw that the Tiagra will accept a 24 teeth inner chainring. if i were to put that 24 teeth ring on that's be a 52, 42, 24 set. That's 28 teeth difference right there. If I use it with a 12 - 32 rear cogset thats another 20 teeth. That's a total of 48 teeth of chain to wrap. Will an Acera long cage rear derailler handle that (not the one with oversize pulleys)? Will an old school Deore front derailler handle that 28 teeth chainring difference? what can i expect in front shifting? Good, acceptable or poor? BTW, it'd be with 9-speed dura Ace bar end shifters in friction mode.

Thanks and cheers

On Monday, December 28, 2015 at 2:30:05 PM UTC-5, wrote:
Your Tiagra crank has a 74mm bcd for the inner chainring. Before the current Shimano nonsense of using a 96mm bcd on triple cranks which limit the small ring to 30 teeth. I have a bike with Campagnolo using 52-42-24 rings and 13-28 cassette and triple front derailleur. I only use the inner 24 ring with the biggest 2-3-4 cogs. Never anything else. I suspect your bike would work fine if you just use the inner ring with the biggest few cogs. I'd advise making the chain long enough to go over big-big combination just in case, even if you never plan to use that combo.


I had a shop install a new chain and cassette ONCE. They made the chain too short for the big big combo and i acccidently shifted into it when starting to cross a busy highway. Equaled an instant jam and resulted in a tumble to the pavment. fortunately I was able to get myself and the bicycle out of the way of approaching traffic. After that I ALWAYS make sure the chain can handle the big big combo - just in case.

Thanks to all.

Cheers