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Hi
I have just replaced 2 bikes with new cassttes, chains and gear inners.
Sunrace 11-42t
Kmc chains
Both 10 speed
Both running oval front rings
Both running clutch mechs
Chains slipping on low gears on both bikes, one slightly worse than the other.
I Have changed front ring over, still slips.
I have changed the new cassette to the old one and still slips.
Chain line looks good
Mech not bent
Changed jockey wheels
I am thinking it's got to be the gear cable not properly adjusted, but tried I think every adjustment.
I am going mad.
Are the lower gears on the right way round. I know from experience that on some freehubs they can be put on the wrong way round and slip like crazy.
You can tell on the sunrace. They have the tooth number stamped on the outside edge. All the numbers should line up if you've got it right.
Does the mech still look straight when up in the 42t?
I've had this with Sram mechs a few times, a little play in the mech, sat straight in the 11t. Bent as hell in the 42.
I pretty much put them on the way they came out of the box, I thought that to.
But yes to my knowledge they are on the right way round.
Mech does look straight.
Have you set the B-tension screw properly?
Lock ring nipped up tight with the right spacers? Happens in lower gears because the larger cogs move more, relatively.
This is probably a long shot but I had something similar with my set up (all new bits) turned out to be that I had the gear cable clamped above the bolt instead of below it on the Derailleur which threw the indexing out just enough to cause a similar issue. Did my head in until I figured it out! MB
Are you absolutely sure your mech hanger isn't slightly bent?
Can look ok, but best checked and straightened with a mech hanger tool if you have such a persistent problem. Turn crunch/graunch into oily zip.
I have the same issue. Had an xt cassette with an expander and it was slipping on the small cogs under power, so I threw money at it and fitted a brand new Sunrace 11-42t and KMC 10-s chain. First ride on it last night and it was still doing it.
Like you, all seems fine with my mech. Gear hanger/dropout is brand new.
😥
A new gear inner in an old outer? It's always worth replacing outers when you're experiencing indexing problems that aren't fixed with a quick twiddle.
A mech hanger alignment tool should be in everyones shed/garage. You'd be surprised what a difference it can make - even on a new mech hanger.
Just because it's new, doesn't make it straight. I'd estimate about 80% of new bikes/hangers need attention from the hanger alignment tool, some needing just a little tweak, others being miles out.