SunXCD cranks and 9 sp front shifting

[Max]

Lately I've been experiencing frequent chain drops with front up-shifts on a SunXCD crank and a 9 sp chain. The chain rings are TA Cyclotourist model - a modern version, but without ramps / pins common on typical 9/10/11 sp chain rings. I checked the alignment of the FD, chainline, chain wear,.. all seems to be fine. Doesn't happen with an 8 sp chain and cogset.

Any advice?..

[Peter Turskovitch]

No advice, but I'd like to note a problem that I had with the same crank / ring combination.

I was using the SunXCD cranks with new 44-28T TA rings, and a wide 10 speed cassette in the back. The crankset came with instructions for setting ti up 10 speed, which amounted to leaving out some washers on the chainring bolts. Nevertheless, I frequently had a serious problem when shifting from the big ring to the small: the 10 speed chain would "stall" in between the rings and just sort of skitter along without engaging. If I was shifting under load I imagine that it could have been wedged in there.

I couldn't figure out the cause, so I ended up swapping the rings for the SunXCD rings, which are ramped and pinned and designed for 10 speed from the ground up.

Peter

[Max]

Thanks for your note, Peter. What's a good source for SunXCD rings?

[Jeff Bertolet]

Are you using friction shifting in front?

It seems the der cage is too wide for the application, or to put another way, the chain really needs to be shoved into the big ring. So, it won't shift onto the big ring without backing the limit out so far that the chain can fall off. Sometimes you can play with the angle/height of the front der to compensate for the lack of ramps. You could also squeeze the cage of the der a tiny bit (if using friction shifting). Ramped ring would probably be easiest.

[Daniel Jackson]

My suspicion is that the narrower 9sp chain is just narrow enough to cause overshifting when the limit screw is set for an 8sp setup. With 8 sp chain, the chain engages the big ring when the derailer is relatively more inboard than it would with a 9 dp chain.

Try bringing in the FD high limit screw a quarter turn. FD should be as close as possible to the chain when in big up front and small out back without a rub.

[mitch....@gmail.com]

+1 what Jeff and Daniel said.

I recently set up a 9sp chain/cassette with early 80s Campagnolo SR front derailleur (and old school ring spacing).
It shifts fine up from the small ring but requires significant over shift to put the chain up on the ring. Every shift requires an immediate trim back, more trim back than an 8sp chain by far. I'm using a guard ring in the outer position but the over shift required would be enough to unship the chain to the outside like the OP described.

Before getting new rings I'd experiment with a front derailleur designed for 9 or 10 speed.

--Mitch

[Max]

Thank you all for the suggestions!

I've set up many bikes, from fixed to old 6sp to indexed 10sp, and always managed to get the front shifting to work. This set up in particular, using downtube Silver shifters, has been more finicky for front shifting than anything else I've tried. I do have a Daytona 10sp crankset with ramped / pinned rings in a parts bin, but would prefer to get this SunXCD unit to work, as I like the gearing and the low Q-factor.

I will have a look first at mounting a 9sp FD, then perhaps ramped rings, as suggested.

[satanas]

TA say "for 8 speeds maximum" for Cyclotourist rings, however I saw someone at PBP last year with 11 speed, so it must be possible, if not ideal. Pinned and ramped rings may or may not help, unless you can perhaps find a paired set (in 110 bcd to fit the Sun XCD adaptor) that can be fitted; I used non-matched TA pinned and ramped 9/10 speed triple rings last year (47x35x24) and had the worst front shifting I'd ever experienced.

Later,

Stephen

[Andrew Fatseas]

I had a similar problem. Bending the outer plate of the derailleur inward slightly to narrow the derailleur channel solved it. 

On Sunday, 6 November 2016, Max <msh...@gmail.com> wrote:

Lately I've been experiencing frequent chain drops with front up-shifts on a SunXCD crank and a 9 sp chain. The chain rings are TA Cyclotourist model - a modern version, but without ramps / pins common on typical 9/10/11 sp chain rings. I checked the alignment of the FD, chainline, chain wear,.. all seems to be fine. Doesn't happen with an 8 sp chain and cogset.

Any advice?..

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[Evan Estern]

I've had very good results with the Suntour Cyclone ll FD.  I use it with a 9 speed drivetrain and unpinned, unramped, chainrings in 46/30, though not the SunXCD.

[Peter Turskovitch]

I got the SunXCD rings from Velo Duo in the UK. I'm in europe and shipping was fine. No idea whether they ship to the US or how much that would cost.

[LBleriot]

I purchased XCD rings from Velo Duo and had them shipped to the US.  Easy Peasy.  Velo Duo were great to work with.

[TomT]

To add my personal experience to Peter's post,  I too have been trying to use XCD crankset with XCD 3 bolt rings and have had problem with chain drops, and or chain rubs when using small ring to small cogs, the outermost 2 or 3.  It seemed that a certain pin on the big ring would snag the chain on every revolution.  I tried adding the included thin washers to the chainring bolts - did not work.  Tried changing the chain line by adding a 2 mm spacer on the drive side, nope. Finally I flipped the small ring over, so that the counterbored holes are facing the front, I know it's not meant to be but it gives me more space btwn the rings, and that worked like a charm.  Everything shifts great, no rubbings even at the small/ small or big/big combo.

It lead me to thinking that something is amiss, either with the specs or the machining of the small rings.  Maybe they just need to provide a slightly thicker bolt spacers?

My drive train is Shimano 7800 w/ Microshift barend shifters.

I am using a 113 mm BB and have plenty of clearance btwn the ring/stay and arm/stay. I suspect you could go with a 110 mm BB but I'm fine the Q as is.

I think that the 3 chainring bolts are a bit undersized, I find them prone to loosen or snapped if overtightened.

I love the look of the crank and am glad that I finally got it to work properly.

[Max]

Interesting. Thanks for sharing. My crank is the TA Cyclotouriste style, so this solution might not readily apply, but I'll have a closer look... (the bike is a bit muddy now after a dirt road ride in the unseasonably warm weather.)

- Max in A2

[Peter Turskovitch]

2 months in and I can report that the Sun rings work perfectly for me. When first installed I had chain suck when shifting into the small ring under load. That disappeared within about 500km. Maybe the rings wore in? The chain? I don't know but now everything is perfectly smooth.

I have the Sun 3 bolt crank and 26-44 rings, shifted using a shimano cx-77 front derailler. Shimano 600 tricolor downtube shifters mounted on bar end pods. In the rear a 10 speed 11-40 sunrace cassette. Wipperman stainless steel chain. I love it - this is the best set up I've ever used, and I've used a lot. I chose the Sun crank based strictly on wanting small chainrings and a road chainline without breaking the bank. The chosen rings turn out to be perfect for my riding. I live in the Alps and pull a toddler in a trailer.

BUT there is some cheap shit included with the crankset. The chainring bolts are woefully soft. Torquing them hand tight with a normal allen key led to significant galling of the tool. I could have stripped the bolt heads if I wanted to. The dust caps, furthermore, are total GARBAGE. Throw them away! They are allegedly loosened with a 5mm hole in the middle. Well, I greased and installed them, did a hard ride, and then thought to give one last torque to the crank arm fixing bolts (as I like to do). Tough luck - I stripped the hole out of the dust cap into a perfect circle before I realized what was happening. Normal hand strength, well greased part, newly installed! It remains there now. When I have time I'll drill a couple holes to remove it with a pin spanner, so it's not fatal. Just very annoying.

My advice about using the SunXCD chainset:
- If you're using a 10 speed chain, get the sun rings and not the TA.
- Install the ring bolts with care and grease. They are soft.
- Throw the dust caps in the garbage.

Peter.

[John P]

That's mountain bike low gearing.  I know I like it on my mtbs.

Slightly off topic, but anyone who rides 44-11 high on road, how does it work for you?  Spin it out often, or not?

  -John

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[Nick Favicchio]

44-11 is just the ticket for me. I was using 42/26 up front and 11-28 9s in the rear, switched to 44/28 up front and those 2 extra teeth on the big ring make it just right for me.

42-11 spun out a hair too quick.

[Jim Bronson]

I've ridden probably 10,000 miles on 44-11 being the highest gear.  Works great 99.9% of the time.

I have been out with some rando buddies on a 200K with an extremely strong tailwind where they had higher gears and I was unable to pedal fast enough to keep up.  It's a pretty unusual situation though when 30+mph is attainable on flat ground and it's only happened once.  I can usually keep up with my friends when going downhill by going into a tuck, even when they are pedaling.

I have had other strong tailwind situations where I was still able to keep up at around 25.  I think that one situation, there was a certain person on his carbon-fiber go-fast that pushed the situation.  That same person now rides a different, not so aggressive bike that doesn't go quite as fast or weigh as little, so problem solved.

-Jim

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[satanas]

I've never needed a higher gear than 46x12 on randonnees, and that only on long downhills with a tailwind; one of our regular couses had 100km of overall descent at the end.

I'd only use 44x11 for Alpine descents on good surfaces, and mainly for overtaking cars. :-)

Usually 46x14/42x13 is enough for touring, and overkill for offroad. I'll probably take 42x12 to PBP 2019, and if there aren't tailwinds then 42x13 would likely be plenty. YMMV.

IMHO it's more useful to have closer ratios where they'll get used often, or lower gears, than to have high gears that might see occasional use.

Later,
Stephen