Compact + Q-Rings = No Go?

Sep 21, 10 19:19

Post #1 of 28 (12293 views)

It takes a pretty tricky mechanical problem to stump me. Color me stumped.

Cervelo Soloist, circa 2005. SRAM compact crank. Q-rings in 50/34.

Chain drags along the tail of the FD cage when on the small ring, all the way until about the last 3 cogs. Sure, I can lower it so it doesn't do that, but then it would be below the big ring by at least 5mm, and obviously smack into it when the "tall" part of the oval reaches the FD.

I can't be the only one with this problem. First, the Soloist's braze-on hangar is steeply attached. That makes it worse because it rotates the FD clockwise when viewing from the drive-side. But I shimmed it up top just to see if tilting it counterclockwise would work, and it still wouldn't be enough. Second, I shopped around at some LBSs and they showed me some old compact FDs, and they wouldn't solve it either -- the cages really aren't very different.

What gives? Am I stuck with going to a round big ring? That just can't be right.

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Re: Compact + Q-Rings = No Go? [Aztec] [ In reply to ]

Sep 21, 10 19:36

Post #2 of 28 (12277 views)

SRAM Red compact + 52/34 Q rings = IMLP and Toughman

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Re: Compact + Q-Rings = No Go? [Aztec] [ In reply to ]

Sep 21, 10 19:39

Post #3 of 28 (12271 views)

P2C, SRAM Red compact, 52/36 aero Q-rings. No problem at all.

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Re: Compact + Q-Rings = No Go? [Tri509] [ In reply to ]

Sep 21, 10 20:09

Post #4 of 28 (12255 views)

How are you dudes keeping the chain from dragging along the tail of the cage in the small ring????

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Re: Compact + Q-Rings = No Go? [Tri509] [ In reply to ]

Sep 21, 10 20:10

Post #5 of 28 (12252 views)

What FD are you using?

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Re: Compact + Q-Rings = No Go? [Aztec] [ In reply to ]

Sep 21, 10 20:18

Post #6 of 28 (12241 views)

I don't know how to explain it. It simply works. What FD do you have? I use an Ultegra FD. Everything else is Red incl shifters. I would call rotor. They must deal with these issues all the time. 866-391-0493.

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Re: Compact + Q-Rings = No Go? [paxfobiscum] [ In reply to ]

Sep 21, 10 20:23

Post #7 of 28 (12238 views)

Quote:

52/34

I was under the impression that the maximum gap between rings was 16 teeth, regardless if Q-Rings, standard, 110 or 130 BCD.

Clearly not if it works for you. That opens up a huge range of gearing options. I would have thought the drop between the outter and inner rings would cause some pedalling inefficiencies, but I guess you just shift up another couple of gears extra at the same time?

A cunning plan indeed.

Re: Compact + Q-Rings = No Go? [grinning ape] [ In reply to ]

Sep 21, 10 20:41

Post #8 of 28 (12226 views)

And I would think the rear deraileur would struggle to adjust that far without a long cage. Hmm.

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Re: Compact + Q-Rings = No Go? [Tri509] [ In reply to ]

Sep 21, 10 20:42

Post #9 of 28 (12221 views)

In Reply To:

I don't know how to explain it. It simply works. What FD do you have? I use an Ultegra FD. Everything else is Red incl shifters. I would call rotor. They must deal with these issues all the time. 866-391-0493.

Campy Chorus. Two of them, about 3 years apart in age/design (but very similar cage shape).

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Re: Compact + Q-Rings = No Go? [Aztec] [ In reply to ]

Sep 21, 10 20:48

Post #10 of 28 (12213 views)

I have Campy record with 50/34 Q-Rings. No problem at all.

Campy previously had separate CT FD and STD FD. When I recently replaced my CT FD, LBS said they now only make the one FD now that covers both CT and STD setups.

Tinker with it, you'll get it right. There's always some adjustment process.

Re: Compact + Q-Rings = No Go? [Aztec] [ In reply to ]

Sep 21, 10 21:02

Post #11 of 28 (12207 views)

Depends on your frame. Blade - yes. P3 - no.
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Re: Compact + Q-Rings = No Go? [Aztec] [ In reply to ]

Sep 21, 10 21:09

Post #12 of 28 (12200 views)

FSA carbon compact with 50/36 Qrings. RD FD on a TitanFlex Transition . No problems.

Formerly DrD

Re: Compact + Q-Rings = No Go? [Aztec] [ In reply to ]

Sep 22, 10 1:09

Post #13 of 28 (12166 views)

take a look at your deraileur hanger. Sometimes ith all the compressive force of the clamping screw the hanger slot will start to widen/deform a bit and what happens is that when the derailleur is positioned above midline in the slot (to clear the q-ring) the bottom edge of the derailleur mount area drops deeper into the slot, tilting the back of the derailleur down and hence the rings catch on the trailing edge. I've seen it a couple of times including on my bike. You prety much just need to squeeze the hanger slot back into shape or if it gets bad like on my old bike I dropped a shim under one edge of the hanger mounting tab to kick it up a bit.

Might not be your problem but when it happened to me it sure was a mystery for a while.

I'm running a FSA compact with q-rings on my road bike btw and it works great.

Re: Compact + Q-Rings = No Go? [Aztec] [ In reply to ]

Sep 22, 10 1:13

Post #14 of 28 (12162 views)

No ideas but how are you?

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Re: Compact + Q-Rings = No Go? [Aztec] [ In reply to ]

Sep 22, 10 4:10

Post #15 of 28 (12114 views)

Is it possible to shim the derailleur back a little and drop it down?

jaretj

Re: Compact + Q-Rings = No Go? [Aztec] [ In reply to ]

Sep 22, 10 4:15

Post #16 of 28 (12111 views)

SRAM Red, with 50/34 Q rings, using a Campy Chorus standard FD. I can get it to work fine on two bikes (both with the same FD).

How? Dunno. Just works.

I had problems initially with the outer chainring clipping the FD at its largest point.

I am pretty sure that while the bike was on the stand, I did for a while have chain drag on the rear of the FD, but that was because I replaced a standard crankset with the 50/34. I also had drag on the chainstay when crossed in 34-12. I shortened the chain, and everything works fine.

Got a saggy chain?

FWIW, I have a 12/25 on the rear, and R3SL/SLCSL (so should have the same length stays as your Soloist - 399mm, off the top of my head). I'm using a Campy 10s chain with 52 links (a link for this purpose being the gap in which a tooth sits).

Last edited by: Greg66: Sep 22, 10 4:18

Re: Compact + Q-Rings = No Go? [Aztec] [ In reply to ]

Sep 22, 10 6:21

Post #17 of 28 (12076 views)

2009 53/39 Campagnolo Record+q-rings campy record front der=no go. BCD is correct but campy has a small tab on backside of rings that we could not get past for smooth shifting

Re: Compact + Q-Rings = No Go? [Tai] [ In reply to ]

Sep 22, 10 6:35

Post #18 of 28 (12067 views)

In Reply To:

take a look at your deraileur hanger. Sometimes ith all the compressive force of the clamping screw the hanger slot will start to widen/deform a bit and what happens is that when the derailleur is positioned above midline in the slot (to clear the q-ring) the bottom edge of the derailleur mount area drops deeper into the slot, tilting the back of the derailleur down and hence the rings catch on the trailing edge. I've seen it a couple of times including on my bike. You prety much just need to squeeze the hanger slot back into shape or if it gets bad like on my old bike I dropped a shim under one edge of the hanger mounting tab to kick it up a bit.

Might not be your problem but when it happened to me it sure was a mystery for a while.

I'm running a FSA compact with q-rings on my road bike btw and it works great.

Hey Tai. That's the opposite of my problem (and the braze-on hangar is in great shape). In my case, the tail is about 1 to 1.5 cm too high, so the chain literally sits on the end of the cage and drags.

**************
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Re: Compact + Q-Rings = No Go? [Greg66] [ In reply to ]

Sep 22, 10 6:39

Post #19 of 28 (12063 views)

In Reply To:

SRAM Red, with 50/34 Q rings, using a Campy Chorus standard FD. I can get it to work fine on two bikes (both with the same FD).

How? Dunno. Just works.

I had problems initially with the outer chainring clipping the FD at its largest point.

I am pretty sure that while the bike was on the stand, I did for a while have chain drag on the rear of the FD, but that was because I replaced a standard crankset with the 50/34. I also had drag on the chainstay when crossed in 34-12. I shortened the chain, and everything works fine.

Got a saggy chain?

FWIW, I have a 12/25 on the rear, and R3SL/SLCSL (so should have the same length stays as your Soloist - 399mm, off the top of my head). I'm using a Campy 10s chain with 52 links (a link for this purpose being the gap in which a tooth sits).

Ha! Thought of that and used my shorter chain from my P2C. I have just barely enough to allow the big/big combo without it seizing. In your case, the rear deraileur should have been taking up the slack, unless the chain was really long or you had too much span between small/small and large/large for the RD.

**************
Too f@ckin depressed from various injuries to care about having a signature line.

Sponsored by Blue Shield PPO.

Re: Compact + Q-Rings = No Go? [Aztec] [ In reply to ]

Sep 22, 10 7:01

Post #20 of 28 (12049 views)

I use fsa k force light compacts with a qring on a Lucero lite. I bought a dura ace front der that was ground down a bit to work with mine. Well I got my cranks a couple days befroe the front der so brought to my mechanic. He hooked it up with original dura ace front der and it works perfectly. No need for other.

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Re: Compact + Q-Rings = No Go? [bmanners] [ In reply to ]

Sep 22, 10 7:09

Post #21 of 28 (12040 views)

In Reply To:

I use fsa k force light compacts with a qring on a Lucero lite. I bought a dura ace front der that was ground down a bit to work with mine. Well I got my cranks a couple days befroe the front der so brought to my mechanic. He hooked it up with original dura ace front der and it works perfectly. No need for other.

Maybe the Shimano FDs have longer cages, or are curved/angled downward more or set farther back. Doesn't seem likely, but I have to wonder.

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Re: Compact + Q-Rings = No Go? [Aztec] [ In reply to ]

Sep 22, 10 7:37

Post #22 of 28 (12029 views)

I had a similar problem (52/36) running SRAM on a blue T14 - ultimately went to an ultegra triple - tried all the shimming stuff with the SRAM derailleur and it was never quite on. I assume you could find a campy triple front on e-bay somewhere.

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Re: Compact + Q-Rings = No Go? [jaretj] [ In reply to ]

Sep 22, 10 11:25

Post #23 of 28 (11980 views)

In Reply To:

Is it possible to shim the derailleur back a little and drop it down?

jaretj

Aztec,

Jaretj might be on to something here. Since your FD angles clockwise resulting in a "higher" tail hence the chain rub, maybe you should consider some sort of spacer or washer between the FD and the frame braze to "push" the FD back a bit which will allow you to lower it since it won't rub the big ring anymore. Long sentence I know but if you read it well you will get what I am saying. David Millar of Garmin has this same problem with his big chainring because of its very aggressive oval shape so he has a big 1cm spacer between the FD and frame braze. You could also just add a small shim that will allow you to rotate the angle counter-clockwise of your FD and lower the tail.

By the way, my FD is a SRAM Red and maybe it has a lower tail than other FDs.

P:)

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Re: Compact + Q-Rings = No Go? [jriosa] [ In reply to ]

Sep 22, 10 12:18

Post #24 of 28 (11952 views)

I'm using regular rings, on a BPStealth frame, sized 55 and 39. This is outside what Qrings recommends, and I know why!!! To make it fit I shimmed my DA front derailleur back by about 0.1" using two aluminum washers (prebent to the right curvature of the clamp) and THEN I had to grind off a little bit of the outer cage. It was pretty close but just barely dragging on the big Qring when shifting. I probably took off less than 0.1" of steel from the cage around the back/bottom of the arc. I hit it with some bluing compound and it hasn't rusted over the past 4 years of abuse, so it's probably safe.

I chose 55/39 because this way I have very little overlap between gearing. The 55 is great for TTs or downhills and the 39 is fine for anything short of a 20% grade.

Mad

Re: Compact + Q-Rings = No Go? [triguy42] [ In reply to ]

Sep 22, 10 21:51

Post #25 of 28 (11906 views)

In Reply To:

I'm using regular rings, on a BPStealth frame, sized 55 and 39. This is outside what Qrings recommends, and I know why!!! To make it fit I shimmed my DA front derailleur back by about 0.1" using two aluminum washers (prebent to the right curvature of the clamp) and THEN I had to grind off a little bit of the outer cage. It was pretty close but just barely dragging on the big Qring when shifting. I probably took off less than 0.1" of steel from the cage around the back/bottom of the arc. I hit it with some bluing compound and it hasn't rusted over the past 4 years of abuse, so it's probably safe.

I chose 55/39 because this way I have very little overlap between gearing. The 55 is great for TTs or downhills and the 39 is fine for anything short of a 20% grade.

You ground down the outside of the cage, near the front end of it? I think I see -- you could lower it slightly farther that way. I have more like 1cm to move it, but the combo of a shim, grinding may help. I have an old steel FD to experiment with.

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Too f@ckin depressed from various injuries to care about having a signature line.

Sponsored by Blue Shield PPO.

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