New SRAM PC850 chain issue.

CRAIGO5000

My old KMZ chain came with my bike and I've counted 113 links - my Trek FX has one of those 7-speed Shimano mega range cassettes where gear 1 is huge compared to gear 2.

The new SRAM PC850 chain is for an 8 speed BUT it has 114 links. I can't see how I can make it into a 113 links as the master link is an outer link joined to an inner link. This means removing 2 links so I'd end up with 112 links. The chain as it is with all 114 links doesn't look like it sags or wobbles excessively when on the largest front gear and smallest rear. In this position the rear dérailleur in perfectly vertical too which I've been told is what you should aim for when fitting a chain to bike when you have no old chain as a guide to work from. If I then move the rear dérailleur to gear 1, the small guide pulleys move to near horizontal and I think that removing anymore links will push the dérailleur out of it's working boundary.

I've concluded that the PC850 with 114 links chain may well be suitable for my 7-speed based on the fact that is has that huge mega-range 1st cog on the cassette?

Am letting myself in to a world of hurt with this? I need the bike to be 100% reliable as it's my work horse.

Cheers,
Craig

PBo

CRAIGO5000 wrote:

My old KMZ chain came with my bike and I've counted 113 links - my Trek FX has one of those 7-speed Shimano mega range cassettes where gear 1 is huge compared to gear 2.

The new SRAM PC850 chain is for an 8 speed BUT it has 114 links. I can't see how I can make it into a 113 links as the master link is an outer link joined to an inner link. This means removing 2 links so I'd end up with 112 links. The chain as it is with all 114 links doesn't look like it sags or wobbles excessively when on the largest front gear and smallest rear. In this position the rear dérailleur in perfectly vertical too which I've been told is what you should aim for when fitting a chain to bike when you have no old chain as a guide to work from. If I then move the rear dérailleur to gear 1, the small guide pulleys move to near horizontal and I think that removing anymore links will push the dérailleur out of it's working boundary.

I've concluded that the PC850 with 114 links chain may well be suitable for my 7-speed based on the fact that is has that huge mega-range 1st cog on the cassette?

Am letting myself in to a world of hurt with this? I need the bike to be 100% reliable as it's my work horse.

Cheers,
Craig

Recount old chain - it's not possible to have an odd number is it? Did you take a power link out and forget to include it?

UndercoverElephant

Yeah, I'm not sure how you'd manage to get a chain with an odd number of links, as they tend to come in pairs. Have you tried measuring the chain compared with the sizes of the largest cog and chainring?

http://www.parktool.com/blog/repair-hel ... gth-sizing

Blue Meanie

So, what's a half-link :oops:

PBo

Blue Meanie wrote:

So, what's a half-link :oops:

aren't they only used on single speed chains to help get tension right?

dondare

Leaving aside the unlikelihood that your old chain had an odd number of links, I'm willing to bet that the "stretch" (mostly wear, in fact) that has taken place since it was first installed means that it is as long as the new 114 link one.
The 114 link will work just fine, assuming all other adjustments are correct*.










*get-out clause.

desweller

dondare wrote:

Leaving aside the unlikelihood that your old chain had an odd number of links, I'm willing to bet that the "stretch" (mostly wear, in fact) that has taken place since it was first installed means that it is as long as the new 114 link one.

Note that, if this is indeed the case, chances are you'll need a new back block as well.

CRAIGO5000

The bike rides fine with the 114 link SRAM chain but there is some stretch in the old chain evidence is a side-by-side display of links not matching up.

I also had some issues with the gearing not going from 3 to 4 on the rear. I tuned that out on the barrel adjuster and now I've noticed that when in the large front cog, the chain sounds like it's rubbing at the rear. Can this rubbing be tuned out at the rear by adjusting the H L limit screws?

nicklouse

maybe maybe not.
what gears is it happening in?

most likely to be cable tension still.

CRAIGO5000

If I'm in the middle front, I can cycle through all the rear gears nicely. If I'm in the big front and cycle through fron the large rear to large small, I get a chain rubbing noise when in the smaller rear gears as I peddle.

phy2sll2

CRAIGO5000 wrote:

If I'm in the middle front, I can cycle through all the rear gears nicely. If I'm in the big front and cycle through fron the large rear to large small, I get a chain rubbing noise when in the smaller rear gears as I peddle.

Rubbing in smaller rear gears? Sounds like you need to (very slightly) loosen the high limit on the front derailleur. If chain jumps off big ring when you change up then you've gone too far.

CRAIGO5000

Okay it's all fixed now as best as I can get it. The chain no longer rubs at all but I can't 100% dial out the fact that I can either have my gears well through 7 to 6 OR 3 to 4. A quarter turn of the adjuster makes changes from 3 to 4 great but then going from 7 to 6 stutters. A quarter turn the other way makes 6 to 7 great but then 3 to 4 stutters.

Oh and the old KMZ chain did have 114 links just like the new SRAM replacement - I had miss counted! :oops: