I recently performed a similar conversion on a 2001 Specialized Sirius. The bike began with a 52-42-30 triple and 12-25 9 speed cassette. I replaced the middle and inner chainrings with 39-24. I will install the appropriately sized bash guard from
https://bbgbashguard.com/ in the outer position when it arrives in the mail.
The old cassette was removed and an 11-32 9 speed cassette was installed.
I lowered the front derailleur as much as I could without interfering with the lower seat tube bottle cage braze-on, and tightened the outer limit screw to prevent the derailleur from moving into the outer position. Finally, a Wolftooth Roadlink (
https://www.wolftoothcomponents.com/products/roadlink) was installed to give the rear derailleur clearance for the
32t cog. The 105 long cage derailleur just barely has the capacity to handle the entire range.
In theory, this probably should not work perfectly, but it seems to work just fine even without the bash guard installed. The chain rubs on the larger ring when in the 24:11 position, but this isn’t a ratio one should be using anyway. However I think I could solve this problem with a longer bottom bracket spindle.
My son is planning to ride this on a mountainous road/gravel tour this summer. The original configuration had too many high gears and not nearly low enough gears. Now he has a range of 97-20.5 gear inches.
This photo was taken before installation of the bashguard. Obviously some swapping of shorter chainring bolts was needed to get the pictured configuration to work.
I can update the photo when the bashguard arrives.
