Throwing my chain - Flexible Chainrings?
Last Post 01/26/2016 10:55 AM by 79 pmooney. 26 Replies.
Author Messages
Jimmy

Posts:33

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01/11/2016 04:39 PM
I have a Wilier Zero.9 which has FSA SL-K compact cranks with a 50T big ring.  It's a FSA BB386 bottom bracket and a new chain.  Chain line appears to be correct and has also been checked by a mechanic.

When I go into a sprint at speed, and then wind up the power, I am fairly consistently throwing the chain over the top of the big ring.  As you might imagine, this is fairly disconcerting.  I am at speed, under very high load and I throw my chain.  It makes me not want to sprint, which is bad, because that's my primary area of strength. 

I used to race as a Cat 2, then Master's, and often won crit's.  The point being, I used to have a lot more power than I do now, and this has never happened before on a variety of other bikes.  This is my first time sprinting on a compact crank.  I just can't figure out what is going on.  My only thought is that the SL-K big ring is twisting.  But I have used FSA rings before with no problem.  I need help before I end up stacking it.  Thanks!
Nick A

Posts:625

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01/11/2016 05:33 PM
Assuming everything is adjusted correctly, as it sounds like it is, could it be flexibility in the frame?

When I was younger and stronger, back when they had stiff steel frames, but downtube friction shifters, if the shifter was a little loose, and you flexed the frame enough, you could change a gear in back.

N
ChinookPass

Posts:809

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01/11/2016 06:45 PM
Can you make it happen in a stationary trainer? Might be able to video it or have someone watch. In high-def, might be able to see what is flexing.

Thinking about throwing a chain in a sprint gives me the shivers.
Jimmy

Posts:33

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01/11/2016 09:47 PM
I can't seem to get it to happen on a trainer. I am not sure if its because the stress is different or simply because i don't have the same ramp up of torque and rpm as on the road. It could be the BB, but it's a pretty stout BB. And while not exactly a scientific measure, it's the same frame Marcotte won the crit championship on. And that boy generates some big numbers.

Thinking about throwing a chain in a sprint..a true sprint..gives me the shivers too. I snapped a crank doing an uphill sprint workout several years ago, and went down like a ton of bricks. So I am extra fearful. (Crank had to have been defective, not as impressive as it sounds,)
Cosmic Kid

Posts:4209

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01/11/2016 10:01 PM
I would doubt it is the CR....100bcd and a 50T is pretty stiff. Maybe I could see it happening if it was a 52T, but even then it would be a stretch.

My gut reaction was frame flex....and chance you have a crack somewhere?
Just say "NO!" to WCP!!!!
79pmooney

Posts:3178

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01/12/2016 12:27 AM
A trick I used to do when I ran the super quick shifting (for its era) Shimano Uniglide chain (circa 1978) was to narrow the FD stops until the chain just rubbed in the big front - small rear and small front - big rear combos. You might try that. I only used the Uniglide chain for big races, using the much longer lasting Sedis chains with my training wheels. In your case, you might try narrowing the stops only for races. If that works, perhaps you could document how much you need to tighten the stop screws (say 1/3 turn) then it would be a brain dead operation to tighten and return the stops. (And I know, brain dead both before and after a race is good because that was often where I was.)

Ben
Nick A

Posts:625

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01/12/2016 10:16 AM
Even though a mechanic checked it... there's up and down adjustment of the front derailleur. There's rotational adjustment, etc., there's a lot to tweak...

I've had slightly loose bottom brackets, slightly loose chain ring bolts, crank arms, rear hub cones, a little loose rear cassette, just weird stuff that isn't obvious at slow speeds or on a work stand, that present problems under more extreme conditions.

Could all be stuff you've checked, but just throwing it out there.

N

Nick A

Posts:625

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01/12/2016 10:19 AM
79,

I miss those Sedis chains. Lasted forever, and CHEAP. As a poor junior, I would clean and run them forever. Finally did break one, and was scary. Pre- cell phones. I walked in my cleats, and rolled down hills, in an aero tuck for the three or four miles home.

N
longslowdistance

Posts:2881

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01/12/2016 08:05 PM
I have little to offer to the OP other than I agree it sounds like a combination of frame flex and perhaps a slight derailleur misadjustment.
.
Sorry for the thread hijack. Anyone younger than 35 stop reading now. Really. I mean it. You kids get off my lawn!
Regarding the sedisport chains, I used to venerate them too. Cutting edge wonderfulness back in the day. I had one saved for many years and mounted it about a decade later on a (for then) more modern setup, perhaps an eight speed. Chain size had not changed. It sucked! The chain was too flexible.
Old school has its charms but what was cutting edge a few decades ago doesn't always mean much. Tech moves forward, and that's mostly very good.
79pmooney

Posts:3178

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01/12/2016 09:17 PM
lsd, those Sedis chains worked very well with SunTour Winners, Perfects, DTs and Cyclone derailleurs. The Uniglides were smoother shifting but the Sedis shifted well and qualified as race reliable needing little attention.

Now asking it to run smoothly over cogs the manufacturers had no conception of, well that could be asking a lot. Sort of like expecting the finest Weber carburetor back in the day to work in any car now. (And as I recall, the Sedis was oldschool 3/32" 5-speed. 8-speeds were two steps narrower.)

Ben
Nick A

Posts:625

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01/13/2016 02:06 PM
No! Nostalgia. Everything used to be better. HA!

One "new" thing that I really appreciate are sealed bearings. So nice to not have worry about that. Also, now that I live in the land of goat heads, clinchers that aren't terrible are nice to have.

Nick
Orange Crush

Posts:4499

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01/13/2016 06:21 PM
I am obviously a sprinting nitwit but trying to picture windiing up a sprint changing front ring particular on compact. I ride compact and even at modest speed I am in big ring, the small ring is for uphill and gravel clay trail.

Not that this solves anything, answers any Q's or fits in chain nostalgia cat so carry on.
longslowdistance

Posts:2881

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01/13/2016 08:34 PM
Any geezers remember the state of the art regina oro chains? If so, Would you admit that?
Ben, my memory is corrected - the sedisport from the vaults was on an appropriately spaced freewheel. What was awesome back in the day with friction shifters sucked with index shifters.
OC, thanks for that post. Made me smile through my dentures. (not really, just trying for a cheap laugh. Now you kids get off my lawn!)
I do hope the OP's problem is fixable with a screw turn and not a frame repair.
Jimmy

Posts:33

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01/14/2016 07:21 AM
No worries on hijacking the thread. I am old, too. Started with a six speed, remember 7sp SIS being a huge deal and poo-pood for the "click" alerting others to your likely.

I think I'll bring my bike in for a second opinion elsewhere. It's worth checking again. Thanks!
zootracer

Posts:833

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01/14/2016 11:43 AM
I had the same problem with a Campy 53/39, after I installed a new front der. Threw chain over big ring. Worked fine in garage but not on the road. Packed a screw driver with me and adjusted on a ride. Never had the problem again. Although my frame is pretty stiff (Colnago Master X-Light)...things work different when under load...
Nick A

Posts:625

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01/14/2016 01:15 PM
Campy Super Record (the original), Sedis Sport chain, and five speed Sun Tour Winner freewheel. :-)

I was a junior, so 53-42 up front, and a straight 15-19 in back. I would have to push that bike up hills now!

Nick
longslowdistance

Posts:2881

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01/14/2016 07:14 PM
Stealthy shifting was a useful dark art. We'd hit that right down tube shifter with our right knee for the sneaky upshift prior to making a jump.
Gawd I'm old.
Orange Crush

Posts:4499

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01/14/2016 09:08 PM
I was conviced beyond a reasonable doubt you guys were old many posts ago. You can stop now. But I take it that suggestion falls on deaf ears or is lost in selective amnesia.
79pmooney

Posts:3178

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01/14/2016 10:07 PM
Nick, I raced against David Lamb when he was a junior. Chased him up Smuggler's Notch. I had my 23. He had your cluster!

lsd, I never got to the stealth part. I used to do it out of the saddle climbing walls. Usually alone. And I never felt like a winner on 18% in a 42-13!

OC, did you say something?

Ben
Nick A

Posts:625

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01/15/2016 08:47 AM
I did the Empire State Games qualifying race with those gears. Four 13 mile loops up Lake Welch at Harriman State Park. It was like doing ten thousand squats each four mile climb. But that was what ya did! LOL. I'm so slow now. Shoot, I was slow then, but worked really hard, and was good at staying near the front, but not at the front. :-)

LSD. Never did the knee thing. But certainly, shifting to big ring a little early, and big cross to the second biggest in back. Then you could drop the rear quickly and "GO GO GO". And if you were me, it was for a few minutes of glory before getting reeled in, then trying to not get spit out the back.

"The older I get, the better I was."

N
smokey52

Posts:492

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01/16/2016 08:37 PM
Hey Nick,

In Harriman, was that loop down Tiorati Brook and up Lake Welch or down Lake Welch and up Tiorati?
There's still a race there every Mother's Day. Keith has been up for it. Either way, it's one of my favorite rides, and just a few miles from my house.

smokey
79pmooney

Posts:3178

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01/16/2016 10:51 PM
Nick, I pulled off something like that at the State Championships for the field sprint. (Everything that mattered was up the road.) I had misjudged the course and race badly. Rode a 54-44 x 12-17 thinking that this flat race was going to be fast. It wasn't and I rode almost the entire course on the 44! Came around the last corner and quietly put it on the big-big. I knew the shift up 2 cogs to jump early using the Uniglide chain would be virtually silent. Hung out 2/3s back (tiny field) on the right hand side. There was a breakdown lane big enough to park diagonally in, but with glass so it was shunned. Wind was from the left but because of the glass, nobody looked right. Hadn't all race. With about a mile to go I put it on the 15 and went. Was passing the leader before anyone said anything.

Very small potatoes but a huge deal for me. That was my last season, my last States and first big race after my head injury. My 10th place felt like a win. Grace Jones, our district rep, got to see me pull it off. (She was at our fall awards dinner 6 months before when word went out to all that I was in a coma. She became my biggest fan after the Stated. Upgraded me to a 2 so I could ride the Mt Washington road race as my final race. Watched me get dropped like a rock at 1,2 criteriums that summer, once drafting the national champion TT woman (and clubmate) in one criterium 'till I got caught and had to pull out. That year the Mt Wash. RR was point to point from almost the Mass border north to Conway. Flat and very windy. Field of 40. Only one other rider as high on a bike as me. Never came out of the drops, never straightened my elbows the first 60 miles. Got dropped at 50 miles, stayed out in the middle of the lane so the wheel van with Grace Jones in the front seat couldn't pass me because I knew I was cooked if it did. She watched from that front row seat as I caught the next dropped rider, the two of use eventually getting 3 more and back on. I finished in the field. Another victory.

From the heart, "Thank you, Grace Jones." (If anyone knows if she or her husband are still with us, let me know and I will send this thank you on to her. At one time, Jones Cycle Wear of Lunenburg, MA)

Ben
79pmooney

Posts:3178

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01/16/2016 11:01 PM
I just googled Grace Jones and saw this. http://www.ltolman.org/99arch/00625gracejones.htm Sad. But it re-enforces my memory of her as a racing official/USCF rep who was a real asset to the sport we love. I remember Alan Kingsberry (sp) being hit by a cement truck a year later at the Nationals,; the driver having been given no clue that a bike race was running a stop sign and crossing his path. My thought at the time? Grace would never allow that course.

Ben
Nick A

Posts:625

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01/17/2016 11:09 AM
It was down Tiorati, and up Welch. We trained their sometimes too, and ran it the other way. I was in lower Westchester, so it was a weekend adventure.

This was the early '80's. I got third in the Empire qualifying games, which was the lowest place to qualify. I think the group started out like a dozen, and we dropped them one by one. There were four of us left, and I got the fourth guy in a sprint. By comparison, they had junior Pan Am game qualifiers there that year too with a big group, at least 50, and I got dropped the first time up the climb.

I think of that climb a lot when I go up Tramway here in Albuquerque. Don't quote me, but it's about 6 miles long and I dunno, a couple thousand feet up. Also, like Welch, you can see way up the road too. Sometimes, I just look at my front wheel to try to ignore it. LOL. Long steady climb. All but the slowest pass me, but it's all good.

N
Gonzo Cyclist

Posts:568

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01/26/2016 08:41 AM
it does almost sound like frame flex like Nick A is saying, I had a steel Merckx back in the 80's, after a couple of years of racing on it, it became quite flexy, I could change gears just by tweaking the handlebars and BB at the same time

Check the height of the front D, sound like it may be a bit high? Had that issue on a cross bike once, and it was my front D, it was like maybe 1mm, maybe 2 mm too high?
Cosmic Kid

Posts:4209

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01/26/2016 09:20 AM
Good suggestion there from Gonzo re: the FD...sometimes a small difference can cause big problems.
Just say "NO!" to WCP!!!!
79pmooney

Posts:3178

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01/26/2016 10:55 AM
I set my front derailleurs so I can just see between the top of the teeth and the outer cage as it passes over the chainring on the upshift.

Ben


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