Bike Doesn't Like Top Gear

autolycus

Well-Known Member
Location
Surrey
I've just fitted a new(ish) chain to replace a badly stretched one that was tending to come off. But the other problem i had - slightly sluggish changing up - remains and top gear (smallest cog) is elusive, needing several turns to engage. When the chain is on the smaller crank chainwheel it won't engage the smallest cog at all.

I've adjusted the h screw and b screw but it made no difference. I don't think the (internally routed) cables are binding but if i help the mech outwards the chain drops down OK.

The new chain has 58 links but the online calculator suggests i should have 59 so i will add a link when i can get hold of one (no-one seems to sell them) but i'm not sure if that will fix the problem. The chain i replaced only had 57.

It seems as if the spring in the derailleur is too weak, but i don't think there is any way to adjust it (?) It's a Sram GX EA 10sp.

Can anyone suggest a solution please?
 

Milkfloat

An Peanut
Location
Midlands
My bike hates Top Gaer too, even after Freddy Flintoff took over presenting.

To me is sounds like a classic case of your derailleur cable being a bit sticky, you can try lubing it around the tight turn at the rear, but you are better off replacing it and maybe the outer too.
 

Globalti

Legendary Member
Firstly, why do you want to have the chain on small-small? That is crossing the chain too far and will wear it out in double quick time because the rollers will be loaded unevenly four times in every turn of the pedals as the chain is forced to change direction. By the time you get 2/3 way down the cassette you should be considering moving up to the big chainring so as to keep as straight a chainline as possible. It's about having mechanical sympathy for the bike.

Secondly, did you also change the rear derailleur cable outer where it curves round to the RD? This wears fast and gets crudded up with wet and dirt, which prevents the derailleur spring from pulling the derailleur fully outwards when it's near fully relaxed, its weakest position. The cable outer needs changing every six months to keep optimum shifting performance.
 

Cycleops

Legendary Member
Location
Accra, Ghana
Let it watch The Grand Tour instead. Sorry couldn't resist. Milky beat me to it!

You should always replace the cassette when you put on a new chain but I don't think that's causing your problem. If your old chain had 57 links why didn't you stick with that? Again shouldn't be a problem.
It's a cable issue caused by insufficient tension so try tweaking the adjuster up. Might also be worth replacing the inner cable too as suggested.
 
OP
autolycus

autolycus

Well-Known Member
Location
Surrey
Thanks for the replies. I was of course referring to Clarkson's Top Gear.

(Naturally, I never run small/small - i just thought i'd mention that it would not go there like it always used to)

I was surprised the old chain had 57 links because it was a lightweight one i fitted myself and i would have used the same calculator. It replaced a 58 linker - now reinstalled - which was probably the original. However, I have a bigger chainwheel than originally, so 59 links is probably optimum.

I took the bike to Evans several months ago when I could not get the front mech to work correctly. They replaced the cables and liners and I'm sure the liner sliding along the cable had been screwing the front mech adjustment. But shifting to higher gears never seemed quite as slick as before. I think the chain was stretched by then too, because it was so stretched when i took it off yesterday it was about the same overall length as the new 58-link chain!

In any event, consensus seems to be that neither the number of chain links nor the cassette would likely be causing this particular problem. Despite the fairly recent replacement of the rear cable i guess the starting point is to do it again and maybe try to incorporate a slightly less tight (longer) outer around the mech? I hate threading blind inside the down tube but i don't suppose there's anything that could create an unseen problem there?

Any further hints welcome, otherwise i'll come back and bother everyone if the new cabling doesn't work.
 
OP
autolycus

autolycus

Well-Known Member
Location
Surrey
Just about, but it doesn't do it smoothly. Typically takes 2-3 turns of the cog. And overall changing up just doesn't feel as slick as changing down.
 
Let it watch The Grand Tour instead. Sorry couldn't resist. Milky beat me to it!
Surely "who wants to be a millionaire" would be a cheaper option then the bike would not have to pay Amazon prime membership.
 

CXRAndy

Guru
Location
Lincs
On the smaller cogs, the chain needs to wrap around more. Having a too long a chain (your case) one link means the derailleur is further back and insufficient wrap. Reduce the length and your issues should clear
 

Globalti

Legendary Member
Just about, but it doesn't do it smoothly. Typically takes 2-3 turns of the cog. And overall changing up just doesn't feel as slick as changing down.
Change that cable outer. I change mine a couple of times a year to maintain shifting performance. You'll be surprised at the amount of rust and dirt you find.
 
OP
autolycus

autolycus

Well-Known Member
Location
Surrey
Thanks so much for all the help and suggestions. It seems in the end it was a straightforward matter of a sticky cable. I think the worst of it was around the BB cable guide which i loosened off and treated with GT85 together with adjacent stretches of cable liner. I also lubricated the cable outer around the mech. It's a pretty tight curve but in the end i didn't bother to change/lengthen it because it's recently been done and the changing up and down is now nice and smooth.

One thing i'm never too sure of: is the inner cable meant to move relative to the liner (i.e. slide inside it)? I'm guessing not because this seems to cause the liner to creep along the inner cable towards the front/rear derailleur and cause function/adjustment problems when it reaches the mechanism.
 

Cycleops

Legendary Member
Location
Accra, Ghana
Glad you got it sorted, with these issues it's usually something quite simple and basic.
It is supposed to slide inside the inner, if it is pulling the outer at the same time use grease instead of the GT85. I would have replaced the outer where it goes into the mech with a nice gentle curve if it's sharp as you say.
My LBS guy down here reckons that it takes about three months before rust starts forming in a outer cable if it's not treated.
 
OP
autolycus

autolycus

Well-Known Member
Location
Surrey
Thanks - i'll certainly do that next time.

Just to be clear, i'm not asking about the outer and inner cables between shifter and frame and around the mech. These are internally routed cables and I'm referring specifically to the liner that wraps quite tightly around the inner cable inside the downtube, through the BB cable guide and a short distance along the otherwise exposed cable towards the front and rear mech.
 
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