Fibber

I’m about to embark on my second “convert-a-drop-bar-road-bike-to-a-flat-bar-road-bike” FRANKENBIKE project. The first was a 2x7 Trek, so the conversion was relatively cheap and easy. I threw a few MTB components at it (combo brake-shifters, a 105 rear derailleur and wider ratio mtb cluster, a smaller front chainring to increase the ratio spread, etc.), and it all stuck beautifully. I’ve been riding the bike for 2 years now.

I recently picked up a Giant OCR-2 drop-bar road with a 3x9 all-Tiagra drivetrain, and want to do this again. There are 3x7 Sora ‘flat bar road’ shifters available along with Sora adjustable-pull brake levers, but the combo will likely top $150. I can get combo MTB bike brake-shifters for 3x9 relatively cheap. I’m pretty sure the pull ratio will work as is with the existing rear road derailleur and freehub cluster (12-25), but pretty sure it won’t with the front derailleur because of the 3x 52-42-30 chainrings.

Searches revealed several informative threads, such as this one: https://www.bikeforums.net/bicycle-m...ifference.html Also, the Cassettes & Drivetrains Spread Sheet was informative, but didn't answer the pull-ratio question. Or perhaps I'm just not understanding the data table information presented....

In summary, the MTB pull ratio would cause the Tiagra 4403 series front road derailleur to overshoot both on the 30 and the 52, when centered on the 42. Yes, I can adjust the limit on the lower, but I’ll be stressing the shifters on the upper if I restrain it before it ‘clicks’. Changing to a MTB front derailleur has it’s issues as the 10 tooth M to H rings is below the Shimano spec of 12 tooth minimum, and also out of bounds of the suggested max chainring. And then we have the seat tube attachment point mismatch.

So…. Has anyone thought about changing (in this case reducing) the ‘travel’ of the Road FD by moving the cable attach slightly outboard on the crank arm? It looks like by slotting or using a custom bolt, there is some latitude here.

Or…. Has anyone ever added thin shims to the right crank arm spider to large chain ring attachment points to move the ring outboard a millimeter or so to compensate for the additional derailleur travel? Just enough to allow the shifter to ‘click’ against the H limit screw? Any idea how far that added travel might be?

I know…. Crazy engineer solutions to create an inexpensive one-off fix, but can’t help but wonder if anyone has solved this in the absence of money?

maddog34

As to adding distance between the mid and large rings... .. you will, most likely, discover the experience of yanking a chain out from between two somewhat flexible chainrings after one upshift.

look for an Early Deore LX front derailleur... they can be had for under $20 , sometimes for free. the early MTBs typically used larger chainrings.... seat tube clamp size and cable pull direction must be considered.

jasoninohio

You've probably already ruled out friction shifters I suppose?

Fibber

Valid point, especially considering the narrower chain. I figure I could get away with a millimeter, but maybe not much more.

A good start. I'll need to go back to some old Shimano documentation and see what I can learn.

Fibber

I was hoping, maybe for aesthetic purposes, to have a matched set of MTB brake-shifters left and right. But if this gets too complex I might go friction on the chainrings.

I'm looking at hardware options in my parts box for possibly extending the cable anchor bolt attach point a little beyond the current screw to see if I can impact the ratio of cage movement.

All suggestions are helpful and appreciated as I work thru this. Of course the fallback position is just to sell a bike to raise the money to buy the Sora shifters. Are they any good?

maddog34

the Sora line is nothing fancy... they work.. similar to Shimano Alivio in quality, maybe a bit lower, IMO.

Lombard

Ever think about getting separate MTB brakes and shifters?

Fibber

Well, my wife looked at me like I was nuts when I told her about my deliberations: "You got the bike for free. You want to make it fit your riding needs but don't want to spend enough to do so? Are you nuts? Go buy the parts!" So today I placed an order with Performance, after reviewing the Shimano catalog.

The bike was built with mostly Tiagra 9 speed, with is now largely obsolete. Tiagra is now a 10 speed groupset. Sora is now the 9 speed group. So yes, it gets a little messy. I decided to stay "Flat Bar Road" rather than mess with MTB shifters and the required change to a MTB front derailleur. The big chain ring (52T) can make that a bit more complex. Why mess with something that works? I read that some 3x road front shifters may have a 4th 'trim' spot, but we'll see if that is true.
The Tektro brakes aren't that great (hard pads), but for not much more than the cost of new pads I got the newer Tiagra 4700 calipers on sale to go along with the flat bar levers.

This will get me started (I have a riser stem, flat bars and ergo grips already). The chain is still at less than 50%, so I can get some ride time in and assess if other drivetrain parts are necessary.

One thought.... The current cassette is 12-25. The Shimano catalog says 27T is the max for the medium cage derailleur. But it looks like the 9 speed 12-27 is history. Anybody try a SRAM PG-950 12-26?

Lombard

Shimano's specs are conservative. You could probably even go up to 12-30T or 11-28T and it would still work. Just be sure to go through all the gears before you ride to make sure the chain doesn't bind in the large-large combo or go slack in the small-small combo. Especially make sure it doesn't bind in the large-large combo or it could rip the derailleur off the bike with potentially catastrophic results. Your chain is likely sized for the 12-25T cassette, so you may need to replace it.

Fibber

Thanks for the feedback. The 12-30 cassette would be extremely attractive but maybe too far for the existing derailleur cage length.. Going to the 11-28 gets me better climbing than the existing 12-25, but that 11 combined with the 52 up front is probably unusable with the exception of a sharp downhill run. But maybe fun to try but a kind of a wasted cog on most roads.

Time to get step one of the build done first, and then see if this is a project worth further investment. I'll be back in a few weeks.... Winter seems to have made a comeback in the NE.

Fibber

Making progress. This is what $200 gets you. I was going to just buy pads for the old Tektro brakes, but new dual pivot road calipers on sale weren't much more.