Tarmac BB guide screws up SRAM red shifting

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mdusink
Posts: 47
Joined: Fri Aug 23, 2013 7:39 pm

by mdusink

Specs: Tarmac pro 2014, SRAM RED 10 speed, 2013 and up.

I had troubled getting my beautifull red cassette to shift nicely. The cassettes make a lot of noise, so it has to be super perfect. The tarmac has internal routing, which, according to several reviews, can be a b*tch. So I did science. I removed the whole cable and independently put a cable through every part of the frame and bar, with and without caps and stuff. So I checked the downtube, the chainstay, the shifters+bars all independently. Final conclusion, the bb guide of tarmac is the problem.

I mean this thing:
Image

If you think about it, it makes sense. It bends the cable and it does so while having a large contact patch with the cable. So after cleaning it up, lubing it a bit. I got quite better shifts. I still have 2 questions, which I'd like your opinion on:

1. I think a cable set with ptfe liner all the way through can help me a lot. Any other thoughts?
2. Is it faulted by design?, as the 2015 has a different style, but... external shifting also have these kind of BB guide's, and I never had any problems with external shifting.

by Weenie


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NealH
Posts: 548
Joined: Sat May 12, 2007 3:40 am
Location: Ormond Be, FL

by NealH

Red 10 was always noisy no matter what I did (changed cassette to Shimano, chain to Shimano, etc), so I took it off and replaced it all with 7900 10 speed, and never a problem since. Today I have 25K miles on it and it continues to shift very well - and with the same guide shown in your picture. The problem is a combination of things, and may include the guide, but Red 10 is the dominant contributor.

As far as the cable is concerned, yes the ptfe lined cable makes a big difference. I have Gore Ride-On Pro but I believe today its Jagwire Elite or something like that. Otherwise, do your bike a favor and get rid of the Sram drive train.

Asymptotic
Posts: 253
Joined: Mon Jul 11, 2011 11:06 am
Location: North Adelaide, South Australia

by Asymptotic

The problem is you have left off the outers that come with the cable kit so that they provide a buffer from the cable rubbing the cable guide. They look similar to the outers that come taped to the frame to help you route the internal cables. They should have been installed at wherever you got the bike built up at. As NealH commented, they perform essentially like the old Gore outers.
Norwood & Adelaide Uni CC

rcb78
Posts: 54
Joined: Sun Mar 02, 2014 6:17 pm

by rcb78

I keep a roll of Nokon liner around the shop for jobs like this. Internal routing doesn't make sense to me if the dirtiest part of the bike still has exposed cables. I like to use the Nokon brake lining for sealing up areas like this. The ID is sized for brake line so there is no drag with the smaller shift cables in it.
The 2015 model is still very similar, except it forces you to use a liner as the guide is actually molded into the carbon. The liner is required so you don't wear the carbon with the cables. They took it one step further though and kept it all internal, hidden by an inspection plate. It looks very clean.

NiFTY
Posts: 1493
Joined: Sat May 26, 2012 11:26 pm

by NiFTY

The cable guide is not the problem. If you are having problems with shifting look at the big players - what housing are you using, how old is it? How old are the cables (they look new) Do you have the correct length of RD to generate a smooth curve. Is your derailleur hanger straight? How old is the chain - is it correctly sized for your gearing, is the chain lubed? How old is the cassette. Is your cable tension correct.

Full length liners will generate more friction because PTFE is higher friction than air.

2013 SRAM is quiet if set up properly. 2012 and earlier was noisy due to the solid dome of the cassette.
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Marin
Posts: 4035
Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

I also think the guide is not to blame, in my experience these work pretty well in the worst conditions. Must be something else.

I've had problems with the entry and exit points with internal routing, but I'd expect Spec to have gotten the angles right...

mdusink
Posts: 47
Joined: Fri Aug 23, 2013 7:39 pm

by mdusink

@everyone: thanks for chipping in and taking the time to post it:

@NealH: I agree shimano is quiter, but I do like the weight difference of Red and the lower-tooth cogs of the red cassette are pretty quiet. It were the 28-25-22 cogs that were noisy and I could fix it with adjusting it with my hand.

@Asymptotic: Thanxs for the input and the DM. So the outers you describe are just like the ones that came from the frame, but a bit shorter (like 10 cm orso?) Won’t they eventually slip into the frame if there not attached to anything, or does the cable tention solve that problem?

I will try your solution though. I have a lot of spares and probably the outers you describe. I only didn’t know what they were for.

Thanks!

(and yes, I understand why mechanics prefer external routing. If I can’t get this to work nicely. I’m going to get a allez or something )

@rcb78: At what length do you cut the liner and do you fixate in in anyway or rely on friction? Thanks!

@NiFty: I should have given more specs: new cables: straight derailleur hanger (I have an adjuster), new cassette, new chain.

The (incorrect) cable tension was a result of the problem. To tight and it wouldn’t shift up nicely and to slack and the downshifting would be rubbish. I don’t understand your comment on the PTFE versus air. Shouldn’t it be that the liner friction is less then the friction of the contact patch of the cable guide?

@Marin: In my opinion, the entry points were good. I also used a decent amount of cable to avoid strong angles. Also, on a positive note for the tarmac. I didn’t use any liners routing the cables/testing for rub in the frame. It was easy getting the cables through the frame. Especially the chainstay. I got it through several times just pushing the cable.

TomHelly
Posts: 72
Joined: Sun Feb 22, 2009 12:31 pm
Location: UK

by TomHelly

Make sure you are using SRAM spec 1.1mm inner cables and suitable housing instead of 1.2mm, which is the standard for Shimano.

Possibly doesn't make as much of a difference for 10spd but I've found that its essential for perfect indexing of XX1/Red22 11spd drivetrains (as you would expect...)

mdusink
Posts: 47
Joined: Fri Aug 23, 2013 7:39 pm

by mdusink

@TomHelly: I have the 1.1 inner cables, but thanks for pointing it out. I found that it's almost impossible to get 1.2mm cables in the shifters, especially in the front derailleur shifter. The 1.1mm went in a lot smoother.

Pottsy
Posts: 134
Joined: Mon Dec 08, 2014 11:54 am

by Pottsy

Make sure you are using the short sheaths at the head tube cable stops, these help reduce friction there.
check that the where the cables were cut is nice & round/ clean as well.
I also put a drop of lube on the cable path in the shifter.

I have built many Tarmac's, Venge's & Roubaix's with SRAM Red or Force & have never had issues. Only when the bike is built with a KMC chain there will be noise issues, once I swap that out to a SRAM or Shimano chain everything is perfect.

mdusink
Posts: 47
Joined: Fri Aug 23, 2013 7:39 pm

by mdusink

@Pottsy:

Short sheaths at the head tube: I got those!
Rounding cut cables: Do that as well. I have a 'bodkin' (sharp pointy thing) clearing out the cable ends.
Lube in the shifter: do that as well :), (as seen on Faustino Munoz making contadors La Bici Roja (Tarmac 2012 I believe))

On the KMC chain. That's a good one. I use a KMC10SL and for back-up a PC-1070. I didn't notice a noise difference, but I will check again.

Thanks!

rcb78
Posts: 54
Joined: Sun Mar 02, 2014 6:17 pm

by rcb78

mdusink wrote:@rcb78: At what length do you cut the liner and do you fixate in in anyway or rely on friction? Thanks!


On my personal bike, I use the nosed ferrules and run full length liner, even though the frame is internally routed. BUT like I said, I use the liner that's sized for brake, since the ID is not a tight fit there is no discernible drag through the run, I've checked with just a cable run front to back. I started this with my cx bike that had external runs and was making it though a full year with a season of muddy races without ever touching the cables. I recable once a year and the shifting stays consistent throughout the year. Decided to try it on the road bike and have no regrets.
On customers bikes, I use a section about 12" long and it stays put on it's own. This is what Spec. has recommended for the new Tarmacs, and includes the liners with instructions to use it that way.

mdusink
Posts: 47
Joined: Fri Aug 23, 2013 7:39 pm

by mdusink

Follow up!

So there it was in a nice plastic bag in which I kept the spares I got with the frame. One small little liner, pre-lubed, exactly the size of the cable guide. It fitted snugly in the rounded part that goes in the chainstay. Reassembled everything back. Carefully thightening the screw on the guide holder. Only a small adjustment needed on the derailleur and tada! perfect shifting. Even with the KMC chain, very smooth, accurate and silent. Totally happy!

Thank again for everyones input, ideas and solutions.

by Weenie


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