ezridernc

I had a bike built for me by an LBS (Surly Pacer, SRAM Rival) in July.

I'd had trouble shifting up to the large ring for some time. After multiple trips back to the LBS owner who built the bike, it was finally tuned correctly by a different LBS (actually a local franchisee of a national chain).

Anyway, the original builder said I had worn out the chain (less than 3 months, 700 miles, no cross-chaining). How? "You must be a pedal masher," he said.

This sounds like BS. 700 miles on a chain? (SRAM 1031). The second LBS who fixed the shifting problem noted that the b-screw adjustment was way off on the rear derailleur. SRAM states the upper wheel of the rear derailleur's tension pulley should be 3 or 4 mm from the largest gear. Mine was like 4 inches.

So, presumably this put more tension on the chain. I noticed when I sat on the bike (before the fix) the chain had no wiggle -like it was going to snap. Now I can reach down and nudge it a cm or so with my 210 lbs self on the bike. There's less "binding" noise now too while riding. Could the b-screw be what caused the chain to last only 700 miles?

DiabloScott

Nope, that's BS. There are ways of damaging your chain that would show up as a twisted link or something.

The B screw will not put more tension on your chain, neither will cross-chaining... and more tension would not wear your chain out faster anyway unless it's huge like you hooked it up to a diesel or something.

B screw wasn't the cause of your front shifting problem either.

cny-bikeman

Chain worn out: Was the chain actually measured with a ruler?
Pedal masher: You don't say what your normal pedaling rate is or what kind of terrain and gearing you have, all of which can have a marked effect on chain life, though something extreme would have to be involved for a chain to be "worn out" in 700 miles.
B-tension: Only if you rode all the time in low gear and the chain was too short, and you only rode up steep hills, and the b-tension screw was really long - and I can't conceive of how the upper pulley could be 4 inches from the rear cog.

fietsbob

were you too sparing on the lubrication of the chain?

more tension comes with increasing the wind up spring's back force, around the cage Pivot rotation..

davidad

The shortest chain life I have had is a little over 2000 miles. On the advice of Zinn I used Pro Gold and did not remove my chain to clean it. He was full of it.

The only way I can see to get only 700 miles from a chain is to ride it in a down pour and not relube it.

ezridernc

how does one increase (or decrease) the wind up spring's back force?

fietsbob

Alternate holes that the return spring is anchored in .. Older RD did that ... IDK Specifically about yours.. what ever that is ..

it requires taking the RD apart.

cny-bikeman

I believe fietsbob was merely telling you the way to increase take-up tension, NOT telling you that doing so would change chain life (as it will not). If you want accurate help we need more info as I requested above.

DiabloScott

That would be tension on the slack/bottom/return side of the chain - which is a small fraction of what the top/load side sees.

ezridernc

It was not measured with a ruler that I know of. I have no idea what my rate of pedaling is. It's hilly in the Charlotte, NC area. I ride on back roads that have the occasional broken pavement. The bike has 50/34 in the front, 11-25 in the back.

fietsbob

yea, Work puts the top tension on the chain ... Like data? KMC has a LCD Digital chain wear checker .

ThermionicScott 

Since you had trouble shifting up to the 50T, did you end up using the small ring with the smaller cassette cogs (11, 12, 13T) a lot? The flexing around smaller cogs can wear a chain out faster, but 700 miles is still pretty hard to believe! I bet what happened was that the chain was marginal, and they used a chain-checker tool, which are known to "fail" chains that still have some life left in them.

Next time you take a bike in for derailleur adjustments, you (and anyone else who's had shifting trouble) should ask them to demonstrate the shifting on the stand before taking it home. It shouldn't take more than a minute, and both parties can be satisfied that the bike shifted through all gear combinations without issue.

ezridernc

That's the funny thing - it never missed a shift on a bike stand. It would mis-shift about half the time while riding, specifically going from the small ring to the large ring. I would press the shiftlever in and the chain would go up but when I let go of the lever, the chain would drop back down.

Andrew R Stewart 

First- 700 miles before a measureablely worn chain is real quick but I have seen it before. Tandems, cargo bikes, bikes left to rust and not lubed, all extreme cases, all with very narrow chaind too.

Second- the vast majority of front shifting issues, assuming a somewhat well adjusted ft der, are rider dependent. Todays teeth designs are so much more shift friendly that many riders never have learned to shift with best technique.

Third- While chain tension is a factor in front shifting (hence the need to soft pedal, see comment #2 ) the tension placed on a chain by the rear der's cage spring is a FRACTION of what the rider can exert on the chain.

Fourth- I wonder if the first shop took the time to test ride the bike in front of the OP. Or go on a ride around the block with him. Andy.

HillRider

You DEFINITELY need a different LBS. The guy who advised you is clearly incompetent or a charlatan.

Andrew R Stewart 

Now this sounds like my qualification. the ft der wasn't well adjusted. If the up shift to the large ring did, in fact, occure and the chain engaged the ring's teeth then the only way for it to spontaneously down shift is because the der was pushing on the chain trying to down shift it.

The qualifications on this is that the lever is working well, that with proper lever/der cage travel the lever will engage the high gear ratchet and stay put. Too tight a cable could also cause the lever to almost but not quite engage the pawl. Andy.

cny-bikeman

Many chain checkers are not accurate - more a screening tool than an measurement device. A ruler is simple and accurate. No idea at all of pedaling rate? Is it close to one rev per second (60 rpm) or significantly higher? What gear combos do you ride in most of the time? Preferably the 50/11 and 50/12 combos should be used only when going downhill, and even the 50/13 would be on a very, very good day on the level for short periods of time (20+mph at only 70 rpm). Even the 34/11 is a pretty high gear (about the same as a 50/16) best for going over 18 mph. In addition the small chainring and smaller cog combos will wear the chain and cogs a bit faster.

AnkleWork

Seems very possible. Also, the extra narrow 9, 10, and 11 speed chains can wear breathtakingly fast, depending on several factors. Good idea to carefully measure the old chain to know what's really happening.

ezridernc

"You DEFINITELY need a different LBS. The guy who advised you is clearly incompetent or a charlatan."

Which guy?

LeeG

then ride in dirt

DannoXYZ 

Both of them are incompetent.

How often did you clean and lube your chain? with what kind of lube?

Bike Gremlin

I would not judge the level of expertise of LBS mechanics by a post made by an, obviously, no offence meant, unexperienced cyclist, who writes as he understood, interpreted. Just my experience from dealing with different people - always hear both sides.


SRAM is a bit picky - they want particular distance of der from the cogs - probably 4 mm from the cogs - that is correct.

Chain can get worn from 1000 km (700 miles). Poor quality one, or lots of cross chaining, or using the smallest sporcket at the rear most of the time etc. There is a simple way to test that - just measure the chain for wear.

Edit: it is 6 mm for SRAM, or 3 chain rivets for older SRAM models of rear derailleurs.

andr0id

There is a lot to be said for actually reading the documents that come with your components. Although it looks like you can just slap on an FD and adjust it, there are very specific difference between the way Shimano, SRAM and Campy are supposed to be set up. And different generations have variations too.

For FD, most specifically is how high above the big chainring the cage should sit and the exact angle of the cage with respect to the chainring.

For RD, they will tell you exactly which cog to adjust on and when the chain should start to touch the next cog when shifting. They will also give specific info for the tension screw.

Getting this correct makes on the road shifting pretty much perfect from the get go.

Getting it "kinda close" means you will drop chains inexplicably and have shifting problems under load.