Gears when sat on full-sus bike

thecremeegg

Trying desperately to set up my bike based on an enduro s-works 2004 frame and the gears have got me stuck. When I sit on the bike, squishing the suspension, then everything moves such as derailleurs so if I configure the gears without me on the bike, when I do sit on it they dont work at all.

supersonic

The outer cable is too short between the front and rear triangles.

nicklouse

or just poor routing.

thecremeegg

Still having issues with this, so I've posted a video

http://www.youtube.com/watch?v=r84_RbrQyxs

The cables are routed fine as far I can see, and I dont have housing on the cable apart from at the top from the shifters and at the bottom where it goes into the derallieur. Is this likely the issue? Do I NEED housing?

Cheers

stu8975

Pretty sure you should have some outer cable underneath the bottom bracket area...from downtube to chainstay.

Skonk

If it's the type that has the plastic cable clips bolted into the under-side of the downtube (which is how most specialized bikes are setup) then the gear cables should be using full length outers.

EG:

Skonk

Just to add, it is a little anoying when the outer splits and needs replacing and you want to put some good quality braided stuff on but it costs almost £5 a meter and you need like 2 meters just for the rear.

Certainly cheaper when you only need partial outer cabling.

Anonymous

thecremeegg wrote:

Still having issues with this, so I've posted a video

http://www.youtube.com/watch?v=r84_RbrQyxs

The cables are routed fine as far I can see, and I dont have housing on the cable apart from at the top from the shifters and at the bottom where it goes into the derallieur. Is this likely the issue? Do I NEED housing?

Cheers

Yes you need housing.
However, what the flinking blip is going on in that video?
It looks as though the effective chain length DECREASES as the suspension is compressed. Eh?

thecremeegg

I wish you could tell me whats going on as I'm so close to chucking the thing in the skip The gears work fine when on the stand, but as soon as I sit down on it they dont!

Oh and skonk I dont have those clips underneath, I have the older style that have 2 different length plastic runners that wont accommodate an outer

Anonymous

I think you've been given your answer - gear cable outers.
Sticking it in a skip seems a bit harsh for your technical ineptitude, but if you want to get rid of it, PM me, and I'll give you my adress so I can re-home it with a responsible owner.

supersonic

Let's have pics of all bits of your cable routing.

Skonk

Yeh defo gonna be easier to solve this if you provide some pictures.

With the bike having an main pivot which is offset from the BB the effective chain length does change when the suspension is compressed; but it shouldn't make a huge difference.

The pivot is above the BB but then it curls down so the chainstays actually extend out from the same level as the BB; so it could indeed slacking the chain a little.

diy

I had exactly the same problem on my 02. Sonic and stu8975 are exactly correct you need a longer cable outer running under the bottom bracket. I routed mine thru the Swing arm for a while but it gets stiff.. I will take a pic of my 02 frame and show you..

thecremeegg

yeehaamcgee wrote:

I think you've been given your answer - gear cable outers.
Sticking it in a skip seems a bit harsh for your technical ineptitude, but if you want to get rid of it, PM me, and I'll give you my adress so I can re-home it with a responsible owner.

Heh well I dont like being defeated by things! I'll go get a few photos so you can critique

thecremeegg

So is the concensus that I need an outer in the same place the diy has one?

diy

Like I said Sonic was correct everyone else was not.

This is the alternative route if you don't like the flappy gear cable, but it gets stiff unless you use thinner cables (e.g. XTR)



you also have the wrong cable guide on your BB you need one like mine - not that it matters, you can trim it down.

You also need them to cross before they go down the forx - they are on the wrong side and you have them only running down one side of your forx.

supersonic

Yep, the outer is completetly missing, and routed wrong! This means as the sus compresses, the inner length changes tension fecking the gears up.

Reroute and will be solved.

diy

..We'll he'll need a bit more cable too. He needs enough so that can fully compress and still have a tiny bit of slack in the loop. Although in my first pic the bike is hanging up so its a little longer than it is under static sag.

thecremeegg

Thanks for that diy, very much appreciated I dont suppose you could take a photo of the cable routing to the rear derallieur ie the bit that actually goes into the derailleur itself?

diy

here you go..


I measured the cable outer I have under the bb and its approx 25cm. It certainly doesn't need to be longer.

thecremeegg

Thanks very much

Cheers for the help everybody, I'll buy some more cable tomorrow and see how I get on!

diy

Good Luck - I guess I should really clean my bike :oops:

Anonymous

Skonk wrote:

With the bike having an main pivot which is offset from the BB the effective chain length does change when the suspension is compressed; but it shouldn't make a huge difference.

I realise that. But I'd never seen a bike appearing to shorten it's chainlength as it compresses.
That HAS to be because the rear mech is trying to shift gears (but can't).

supersonic

After about 90mm of travel on the FSR, the effective chainstay length does shorten.

diy

Nothing the mech cant handle

Anonymous

supersonic wrote:

After about 90mm of travel on the FSR, the effective chainstay length does shorten.

Fair enough, but it looks like it's shortening from static in the video!

thecremeegg

Well sorted out the routing this morning and it seems to be a success! Thanks very much for the help guys

Bar Shaker

Shortening the chain length is the ideal as pedal loses are turned into gains. My iDrive did this.

Anonymous

Bar Shaker wrote:

Shortening the chain length is the ideal as pedal loses are turned into gains. My iDrive did this.

That can be a severe cause of bobbing. Virtually all full suss designs use chain extension so that when you pedal, it tends to extend the suspension.
With the right balance, this means that any downwards momentum of your pedalling is counteracted by the suspension extending the same amount. So, the sus cancels out any pedal induced bob.

diy

agree you want the drive pushing the swing arms down not up. Thats how motorbikes work, cant imagine any benefit of having it any other way.

As I've said before ideally you want it on a para lever and tele lever so that the geometry doesn't change (e.g. like a Beemer motorbike). Of course the downside would be all the extra mass (like a beemer motorbike).

Anonymous

BMW's designs have their own problems though. Which is why no really high performance bikes use that system - and it's not to do with the weight.