TA Pro 5 Vis chainrings and STI shifters

[Eric Hounshell]

Will STIs shift the newly made TA Pro 5 Vis chainrings? I'm thinking of a 42/26. Claris 8sp brifters are so much cheaper than a set of brake levers + bar end shifters that I thought I might go this route for a build I am working on for the wife.

I can't tell if the rings have ramps and pins and whatnot to assist in shifting. If STIs aren't a viable option, I might either go for a downtube lever just for the FD or scrap the plan to use Stronglight 49d cranks and instead find some 110/74 and run 'em double with a chainguard.

Thanks for sharing your experience.

-Eric

[Ryan Watson]

I’ve used 8s Dura Ace and Ultegra STI with Pro 5 vis cranks&rings, no problem! No ramps or pins.

Ryan

On May 16, 2022, at 09:33, Eric Hounshell <ehoun...@gmail.com> wrote:



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[ericni...@gmail.com]

STI can work OK with TA 50.4 BCD rings. IME what matters more is your choice of front derailleur. A modern shaped cage may not play well with such a small ring combination. The shapes and bumps on the cage are intended to work with specific chainring sizes. The same can be said of ramps & pins, which the TA rings do not have. It can often be better to use a FD with a smooth/straight cage. 

Another challenge with compact doubles can be that the bottom of the FD cage can interfere with the chain stay.

Eric in NH

[satanas]

FWIW, I've used Dura-Ace 7400 STI with flat rings extensively with no problems. There's no reason why 50.4 rings should be any different as long as the spacing isn't weird. 7800 (10 speed) was also fine with basic 50x34 rings, assuming you didn't attempt to shift under high load. Like Eric says, many road FDs will hit the chainstay when lowered enough for smaller outer rings. With something like a CX70 or R7000/R8000 42T is about the minimum on most frames before trouble starts, and many other road FDs will contact sooner. If you use a friction front shifter and shorter cage MTB FD it's often easier to get away with a smaller outer ring, however another problem is that most 50.4BCD crankarms have minimal room between the outer ring and crank, so many modern FDs will struggle to fit if aligned normally, or shift properly if misaligned to miss the arm.

Later,

Stephen

[fordb...@gmail.com]

I find flat TA 50.4 rings work fine on my 10 speed bikes. I concur with 42 as the size it gets tricky but even if the derailleur clears the stay you might need to reroute an above the chainstay rear derailleur cable.

Ford

Ghent, NY

[Eric Hounshell]

Thanks everyone. It sounds promising. I did a little back-of-the-envelope math and figured out how much I'd need to drop the FD to go down from the current (ridiculous) 52t big ring to a 42t. It looks like I've got plenty of room before the bottom of the FD cage would hit the chainstay. Now I just need to find a front derailleur dropper in stock somewhere...

It's possible the old Suntour FD that came on the frame will work alright. If not, I've thought about using an IRD Sub-C. No idea (having never seen one irl) whether it would fit the bill of having a smooth/straight cage as Eric of NH recommends. Shimano CX70s seem hard to find. I've written to Microshift to ask if they still make their short cage FD (which some have said is rebranded as IRD Sub-c anyway).

> you might need to reroute an above the chainstay rear derailleur cable.

Ford, can you explain that?

[Ford Bailey]

> you might need to reroute an above the chainstay rear derailleur cable.

Ford, can you explain that?

Sure- on some bikes the derailleur cable is routed above the bottom bracket to a stop on the top of the right chainstay by the drop out. It represents an obstruction to the operation of the front derailleur as it can snag on the bottom of the cage.

I like to keep the cage 2 mm above the ring, not possible without fouling cable.

Ford

Ghent, NY

As in this picture-

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[Eric Hounshell]

Ah. Got it. Luckily this frame has some slick internal routing thru the chainstay (early 70s!).

-e

[Alex Israel]

For a maybe helpful data point, a CX-70 shifted a 44/28 on an old triple just fine, combined with Shimano 105 55xx 9 speed STIs. The 44/28 were on the inside and middle ring spots of the triple crank, and I kept the triple BB (so rings were a bit inboard of where you might be on the TA). 

I liked the 44 a lot for up and down the cassette (11-32 ran great with the 550X triple RD). Probably should’ve kept that more economical setup by using a Shimergo setup with hubbub routing, but went more to a fully Campy 10s on the last overhaul. I personally like the Ergos more than the old STIs for my comfort preferences. YMMV

Shifty Alex in CO

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[njh...@gmail.com]

Back at the turn of the century I was racing on Dura-Ace 7700, but I replaced the 53t ramped/pinned large chainring with a 49t that had no shifting aids, and I really couldn't tell that the front shifting on/off the 49t ring was any worse than with the 53t ring.

As for FDs and chainstay clearance with small chainrings, I routinely use MTB FDs intended for 2x setups on drop handlebar bikes using using either STI or SRAM doubletap shifters. e.g. The Shimano FD-M786 specs say that it is intended for use with a large chainring size of 38-44t, but it will clear the chainstay with a considerably smaller large chainring than that. Here's one setup with a 32t big chainring:

Nick

[satanas]

Unfortunately, the CX70 FDs went out of production just before the pandemic, and by the time we knew this was going to happen they were just about all gone from the supply chain. Occasionally one will turn up on eBay, but usually in top pull in 34.9...

That bike Nick has in the photo has M737 XT cranks and a chainguard in the outer ring position, so isn't really indicative of what's likely to happen with most 50.4BCD cranks - there's a lot more room for the FD to occupy than with TA or Stronglight cranks; I can't recall if the Sugino PX had more room, don't know about Sun XCD, and IIRC the VO cranks are deliberately made with more clearance. MTB FDs with highly contoured outer cage plates will require more space than will old road FDs with flat cages, something to be aware of. I haven't seen a Claris FD, but I imagine they will be relatively compact (laterally), and cheap, plus obviously compatible with the Clark's STI levers. However, it's entirely probable that the cage will be longer than ideal for chainstay clearance; at least there isn't a protrusion below the working part of the FD to connect the two cage plates.

If the OP's frame has a braze-on FD mount, Sugino make a widget that will lower the FD, likely available only direct or perhaps from Japanese sources like alexscycle.com

Later,

Stephen

[Brad]

If you go underneath,  based on sound advice from other people on the list, I used seriously strong double sided tape to attach the plastic guide to an undrilled bottom bracket.  Works like a charm.

[Eric Hounshell]

Nick, thanks for that tip. I have been collecting up model numbers of mountain double groupsets for this purpose.

Stephen, good point. Maybe I should try the Claris FD, if only for the guaranteed STI compatibility alone. I've got another bike with Claris, so I could even borrow before I buy. The Claris FD shifts a 46/30 just fine. I hadn't been considering the Claris b/c Grant Peterson claims they do not work well with friction, and I had been considering friction for the front shifting as a backup (or maybe even preferred since it's infinitely trimmable).

-EH

[lena...@gmail.com]

Somafab just posted IRD Sub-C Front Derailleur V2, Double, Braze-on | Soma Fab Shop. Hoping this will have more chainstay clearance than CX70 and a contour suitable for smaller rings.

[Eric Hounshell]

Interesting. I have been eyeing the Sub-C anyway and tried to get measurements from Merry Sales but failed.

[Stephen Poole]

I suspect this is basically the same Microshift FD that Gevenalle sell:

https://www.gevenalle.com/product/burd-front-derailleur/

Later,

Stephen

[jeffre...@gmail.com]

@ehounshell: a data point that may be helpful to you: I have successfully used an IRD Sub-C FD to shift a Velo Orange 50.4 crankset using 42 / 26 chainrings (the chainrings are TA Specialities).  As you may know, the 42 / 26 combo is the smallest and fits right in with the capacity of the Sub-C FD.  The rear cassette was an 11-speed Shimano Ultegra 11-34.  I did use microSHIFT bar ends in friction mode, so YMMV.   That combo was mounted on a Black Mountain Cycles Monster Cross frame (rim-brake model).  The FD came close but did not touch/interfere with the chainstay.

I've since converted the BMC to a heavy tourer, on and off-road.  I mounted up a really old mountain bike crankset (Shimano M737 series - 44/32/22) mated to a 9-speed cassette (11-36).  Yeah, really LOW gearing.  I was able to locate and find an old Shimano FD that mates well with the M737 crankset - an FD737 (a guy here in Southern California had a large stash of them).

Good luck,

Jeff

Claremont, CA

[Eric Hounshell]

Jeff, awesome, thanks for the info! 42/26 with TA rings is exactly what I am planning to run, probably with an 8sp 11-32 cassette for starters. I think that should be plenty low gearing for asphalt and smooth gravel, even in my hilly/mountainous area. If the fortuitously small old SunTour FD I have in my parts bin does not work for me, I'll probably spring for the Sub-C given your glowing review.

Complicating matters is the fact that the frame has a braze-on meant for an old road double, so I will have to run a FD-dropper as well. The things I do for love (the build is for my wife).

On my 90s MTB/off-road tourer/commuter I've got a 44/32/22 triple and an 11-34 cassette. Wonderfully low gearing, and I actually found myself in the low gear quite a bit on a recent hilly tour full of singletrack and grassy fields. I love it.

-E