The compact chainring front mech issues thread

[nobrakes]

I thought I would start this thread having been through the problem myself and seeing the same question come up again and again.

The problem: with compact doubles, it can be problematic getting the front mech close enough to the big ring for optimal operation.

In my case I have Sram Force 22 components with a 50/34 compact double. The front mech cannot get close enough to work optimally, as the yaw action requires the derailleur to be 1-2 mm from the big ring. Any further away and the slope of the derailleur cage as it ‘yaws’ makes shifting more difficult. The closest I can get is about 5-6 mm. I have spent hours and hours fiddling with it and studying YouTube videos on adjusting SRAM yaw derailleurs. The best I can get is ‘OK’ - with a bit of attention to your shifting technique it will change up reliably but if you don’t treat it really gently it can throw the chain. Back off all pressure and shift really fast is the way that works for me.

I believe this problem will manifest on any compact double with a front mech that has one central bolt hole. Older mechs that have 2 bolt holes to choose from are probably OK as you can get it closer to the chainring. I think Sram moved from 2 to 1 bolt hole design recently which is maybe why it hasn’t been addressed yet by Cruzbike.

The wickwerkz spacer does not work - it puts the front mech too close to the big ring. The place the front mech should be placed on a 50/34 with single bolt hole is right on the edge of the braze on mount where there’s no hole.

I imagine any front mech that does not have yaw action will be less affected by distance although I have not tested that so it’s just a hypothesis.

The ideal solution would be for Cruzbike to extend the braze on mount by another cm so there’s more adjustment available.

Other solutions - non yaw derailleur (untested by me), bigger chainring, or just put up with it and refine your shifting technique.

I do wish Cruzbike would put something on the site to stop people making the same mistake. I believe it’s the shift to single holes front mechs that is the root cause but it should be made clear that there can be issues depending on your front mech and big ring size.

I’d be interested to hear what other compact combos people are using and how well they work. Particularly if you have a yaw derailleur with a single bolt hole and a 50T or smaller big ring.

 

[mattwall]

I have a Silvio 1.5 with a 50/34 compact double and a Shimano ultegra front mech. I have the exact same problem. Also it is very hard to get the front derailleur adjusted out far enough to get the chain to shift onto the big chainring. The braze on mount needs to be positioned about another 5 mm out parallel to the chain line.

 

[paco1961]

Thanks for starting this thread. Having just bought and finished an S40 build the FD has been the biggest problem. After much frustration w the Sram Force 22/ 50-34 I pulled it off and tried an old 105 I had laying around. Same problem w der position. And since we're offering unsolicited redesign advice, the angle of the FD braze on needs adjustment. The chain enters the mech at too steep an angle. The braze on reeds to be rotated to decrease the chain angle of entry for smooth operation.

 

[cranky cyclist]

I took my bike in recently (Silvio V2.0) to have the front derailleur adjusted and the mechanic told me the same thing. I have a SRAM Rival and 50/34 compact double. He told me it works but is less than optimal.

 

[jond]

It’s a bugger that this is your situation. I’ve run a 53 and now a semi compact with nil issue. I’m betting the company is on to it but that is not helping your issue. I hope your less than spec fitting of your front mech proves as reliable as needed.

 

[mattwall]

I think that the" Rotor front derailleur braze on adapter for QXL/Q rings"looks promising. I am looking at the adapter that has a 20mm thick shim that the original bolt recesses into so it can go under the edge of the braze on mount where there is no hole. It also has another bolt and a second shim which is angled so the derailleur angle can be adjusted relative to the chain ring.

 

[nobrakes]

I think that the" Rotor front derailleur braze on adapter for QXL/Q rings"looks promising. I am looking at the adapter that has a 20mm thick shim that the original bolt recesses into so it can go under the edge of the braze on mount where there is no hole. It also has another bolt and a second shim which is angled so the derailleur angle can be adjusted relative to the chain ring.

I tried this one too - it didn’t work. The big block puts the derailleur in a worse position. The small shim improves things ever so slightly but I would save your money. Perhaps redrilling the front mech with a new bolt hole would work, although that is beyond my limited remit

 

[ElyDave]

I don't think it's just the case with CB, my M5 has a compact 50/34 and 11-40 cassette and the front shifting is similarly tricky. I've had several conversations recently along the lines of "standardisation!, don't get me started on that"

I think one of the issues is the massive range of components out there these days, and the constant needless change, just to justify selling the next best new thing, all of which makes it that much harder for people like CB to keep up.

 

[Seth Cooper]

I talked to Robert at Cruzbike about this a few weeks ago and he said there is a new chainstay in the works with a longer slot for the FD. Since I was interested in a the 21.5" stay I am waiting until the summer to get it, that way I will be a better rider and then I can get the redesigned FD mount.

 

[super slim]

https://www.ebay.com/itm/NEW-SRAM-R...503087&hash=item2a73c35ed0:g:W9IAAOSwl9RaAc-q

Could this $96 52T or a $168 52T Qring be used to replace the 50T chainring and get the teeth closer to the derailleur?
If you have a long cage rear derailleur, it will handle the 52/34 front change!

 

[nobrakes]

Yes a bigger ring will get it closer. That’s one of the options.

 

[3WHELZ]

I have a COBB 52/34 configuration combined with a Di2 Dura-Ace shifter. So far, no front derailleur shifting issues.

 

[dtseng]

When I built my Ti frame, I paid attention to the length and angle of the stalk for FD hanger, so the FD would fit both standard and compact chain rings. The frame could accommodate 700x35C tires while using standard short road bike caliper brake.

 

[dtseng]

CB stalk is too long. One thing you could do is to get a hack saw to cut the brazed-on off. Bolt FD near the lower end of the slot. Hold FD steady relative to the compact chain ring, then use TIG electrode to fix braze-on on the stock at two points. Remove FD and weld braze-on. The position and angle have to be correct so when the FD is clamped on, it has room to adjust for both standard and compact chain rings and the front derailleur blade is concentric with chain ring, and shifting should be initiated near the tail section of the FD blade.

 

[Seth Cooper]

When I build my Ti frame, I pay attention to the length and angle of the stock for FD hanger, so the FD would fit both standard and compact chain rings. The frame can accommodate 700x35C tires while using standard short road bike caliper brake.View attachment 6556 View attachment 6557

Wait, I have only been on this board for a few months, so I missed that YOU BUILT A TI MBB? Hopefully there is a build thread on here that I can ogle!

 

[LMT]

How about getting a different front mech? I have a 50/34 on my V20 with SRAM Red Etap (formally had an Ultegra mech) and a 40/23 on my S40 with an Ultegra front mech with a Wickwerts adapter. The Ultegra set up worked fine with a little bit of tinkering to get the trim right.

 

[Seth Cooper]

CB stock is too long. One thing you could do is to get a hack saw to cut the brazed-on off and re-weld. The position and angle have to be correct so when the FD is clamped on, it has room to adjust for both standard and compact chain rings and the front derailleur blade is concentric with chain ring.View attachment 6558

Yeah I considered just cutting 5mm out of the tube and using some threaded rod as an insert and jb weld to put it back together

 

[ccf]

When I put a 50t QXL on my Vendetta, this problem went away. Admittedly an expensive way to solve a shifting problem, but if you are on the fence about Q-rings this might be the reason to spend.

 

[dtseng]

Wait, I have only been on this board for a few months, so I missed that YOU BUILT A TI MBB? Hopefully there is a build thread on here that I can ogle!

I very much want a speed machine like V20 which has swing arms at rear with an effective suspension. The frame should be portable and would fit in an airline allowed luggage together with your clothes. The 700C wheels can be either rented at the destination or pack two wheel rims in shallow box with spokes and hubs removed. Let's break down the weight: the frame should weigh no more than 3 Kg, wheel about 3 Kg, the drive train about 3 Kg, therefore, the whole bike should weigh less than 10 Kg. Nowadays, DF road bikes are around 7 Kg. Why should a two-wheel recumbent weigh so much more?

 

[Gary123]

Seriously? Remove spokes?