Rear Derailleur Adjustment and gear change issue

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Rear Derailleur Adjustment and gear change issue

Postby marty_one » Mon Oct 01, 2012 2:51 pm

Hi All,

two months ago I bought a new bike (Avanti Giro 3.0). When I got the bike the gear change on the rear was really nice a smooth in both directions, after about 5-6 weeks the derailleur wasnt quiet changing as well as it did when brand new, but that was because it was a new bike with brand new cables and the cables stretching. Im not the best when it comes to actually doing the maintenance myself and the first 12 months of servicing is free. So I though why not it's free!

Problem now is after I got the bike back the gear changes were not as smooth and would sometimes not change to a smaller cog easily, plus sometimes the chain felt like it would just slam in to the next gear instead of the smooth transition like it did before the service. Any ideas?

I have played with the cable adjustment (after watching some videos on youtube and reading a few different sites) it seems to change better but im still concerned that I might not have fixed it properly.

Marty.
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by BNA » Mon Oct 01, 2012 3:52 pm

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Re: Rear Derailleur Adjustment and gear change issue

Postby adrian_d » Mon Oct 01, 2012 3:52 pm

Can you tell if certain gears are not as smooth as others? You can make some fine adjustments using the high/low adjustments.

The cables stretching issue can usually be resolved by adjusting the rear deraileur index which will tighten the cable. You want to make sure that this isn't too tight though as it may make the issue worse (may encourage the biggest rear cog to want to fall off the cassette (and too loose could allow the chain to jam in between
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Re: Rear Derailleur Adjustment and gear change issue

Postby marty_one » Tue Oct 02, 2012 8:39 am

Hi, forgot to mention that the groupset is shimano tiagra, on the upside with the adjustments I made it is almost back to where it originally was. Very disappointed with the shop where I bought the bike from.
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Re: Rear Derailleur Adjustment and gear change issue

Postby biker jk » Tue Oct 02, 2012 9:19 am

marty_one wrote:Hi, forgot to mention that the groupset is shimano tiagra, on the upside with the adjustments I made it is almost back to where it originally was. Very disappointed with the shop where I bought the bike from.


Hi. Sounds like the bike "mechanic" may have overtightened the cable. If so, this could explain why you found it harder to change up to a smaller cog. Perhaps one quarter of a turn to the right on the rear cable tension adjuster. You'll often find bike shop "mechanics" not taking the bike for a ride after "adjusting" the gears and so it ends up being a poor "fix".
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Re: Rear Derailleur Adjustment and gear change issue

Postby Reman » Tue Oct 02, 2012 12:52 pm

I find the easiest method is the put the bike into the middle/middle cogs, then turn the index adjuster until the gear changes, then turn it the other way counting the number of quarter turns until it moves down two cogs, halve the number you counted and turn back that many. On my 9 speed 105 rear derailleur it is 16 turns to go between the 4th and 6th gear, so 8 turns from 6th should put it smack bang in the middle of 5th gear.

The other thing to check is the B screw adjustment, see sheldon for more info http://sheldonbrown.com/derailer-adjustment.html
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Re: Rear Derailleur Adjustment and gear change issue

Postby marty_one » Fri Oct 05, 2012 10:03 am

I decided to go back to the rear derailleur again last night cause I found the technical document for it on shimano's website (if in doubt go back to the source!!). While attempting to readjust the cable tension with the adjustment bolt on the derailleur I undid it so much that it came out, as I was following the document to make the derailleur push the chain back to the previous cog in the cassette. When this happened I decided to check the cable tension and found that it was way too loose. So I corrected the cable tension adjustment bolt to where it should be based on the document and fixed the cable tension. Miraculously the derailleur started behaving as the document stated. I haven't been out for a ride yet, but during testing the gears were changing almost perfectly again. Looks like I might have to read up on the b screw adjustment a bit more. But I think I have solved it now, if not I will try and get it sorted with the bike mechanics at kinglake tomorrow ;)
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Re: Rear Derailleur Adjustment and gear change issue

Postby adrian_d » Fri Oct 05, 2012 12:44 pm

marty_one wrote:I decided to go back to the rear derailleur again last night cause I found the technical document for it on shimano's website (if in doubt go back to the source!!). While attempting to readjust the cable tension with the adjustment bolt on the derailleur I undid it so much that it came out, as I was following the document to make the derailleur push the chain back to the previous cog in the cassette. When this happened I decided to check the cable tension and found that it was way too loose. So I corrected the cable tension adjustment bolt to where it should be based on the document and fixed the cable tension. Miraculously the derailleur started behaving as the document stated. I haven't been out for a ride yet, but during testing the gears were changing almost perfectly again. Looks like I might have to read up on the b screw adjustment a bit more. But I think I have solved it now, if not I will try and get it sorted with the bike mechanics at kinglake tomorrow ;)


Very well done mate. Its amazing the initiative you took to learn something new and with such awesome success too.

It took me a while to figure out how the deraileurs worked, and sometimes I still scratch my head lol

Hope you have a very awesome weekend.
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Re: Rear Derailleur Adjustment and gear change issue

Postby ironhanglider » Fri Oct 05, 2012 10:32 pm

adrian_d wrote:Very well done mate. Its amazing the initiative you took to learn something new and with such awesome success too.

It took me a while to figure out how the deraileurs worked, and sometimes I still scratch my head lol

Hope you have a very awesome weekend.


Well done Marty, although I wouldn't go as far as calling it amazing or awesome. You got dudded by a poor mechanic, learned some stuff and did a better job than 'he' did.

I must say Adrian that I am not convinced that you have figured out how derailleurs worked. Your first post in this thread had me confused but I am not sure how much of that is the interesting nomenclature you use.

adrian_d wrote:You can make some fine adjustments using the high/low adjustments.
If you are referring to the limit adjuster screws these only make contact with the mechanism at either extreme. Anything in between and these screws might as well be non-existant These screws need to be adjusted so that the chain will engage the extreme cogs easily, but no further. If the derailleur is allowed to move too far you can get some expensive problems.

adrian_d wrote: The cables stretching issue can usually be resolved by adjusting the rear deraileur index which will tighten the cable.
I don't understand, rear derailleur indexing died a not particularly mourned death in the early 80's with Shimano Positron. Indexing is now days all done at the gear lever and simply regulates how much of the cable is pulled through with each click. The 'tension' on the cable is the secret to making one click's worth of cable pull at the lever translating to one cog change at the back. Perhaps you are referring to the cable adjusters which are often found on the derailler, but there are also inline and frame mounted adjusters around. These often have spring loaded shaped washers to encourage you to turn a 1/4 of a turn at a time.

adrian_d wrote: You want to make sure that this isn't too tight though as it may make the issue worse (may encourage the biggest rear cog to want to fall off the cassette (and too loose could allow the chain to jam in between
I just can't make head nor tail of this. The cogs all fit on the freehub body as a cassette and are held in place by a lockring. Chains jamming between cassette cogs is so rare as to be almost unheard of. The chain jamming between the cassette and either the spokes or the frame are the expensive problems I mentioned before. Chains jamming between chainrings is more common but can be awkward to solve cheaply.

Reman provided the link to Sheldon Brown's website. That is as good an explanation as you will find.

Cheers,

Cameron
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Re: Rear Derailleur Adjustment and gear change issue

Postby adrian_d » Fri Oct 05, 2012 10:56 pm

ironhanglider - Thanks for fixing up my comments. It might be best I go back to the drawing board again and read up a bit more before I post.

Marty - Hope I didn't indicate any advice that may have been incorrect. Sorry
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Re: Rear Derailleur Adjustment and gear change issue

Postby marty_one » Sat Oct 06, 2012 8:33 pm

Nah its all good.

Well the rear derailleur shifting is a ton better. ddnt have to do any tweaking during the genovese kinglake today it is so close to being the way it was before it went in for service. Which I think for my skill level (re: absolute newb!!) is pretty good. All I can say is thank god for youtube and manufactures instructions :)
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