Shimano Tiagra front gear adjustment?

Mikomotor

Hi,

Wonder if anyone can help me?

I have three cogs at front and can't seem to get gear shift to move chain to largest cog. There are two small screws next to each other and I probably just need to understand which combo will work! Anyone have a quick solution for me?

Many thanks,
Mike.

msb123

the limit screws limit (as you would expect) the range of motion of the mech. you need to unscrew the one that limits movement out from the frame. usually this is the one furthest from the frame.

see also http://www.parktool.com/repair/readhowto.asp?id=75

Unknown

It could be the gear cable that is stretched, how far can you move the mech by hand, does it move over the largest chainring, if the limit screw is set wrong, then you won't be able to push it far enough.

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msb123

yes - if you move the lever and the mech doesn't move at first, or only moves a little, the cable may be too slack

inchcape

i had similar problem turn top screw anti clockwise by half turn at a time and see if this solves it.

Mikomotor

...many thanks, guys.

Mike.

Chris Welford

Hi Mikomotor. I was adjusting one of these last weekend, and I have to say I found it a bit of a pig. As others have said, read the Park Tool instructions, and take your time. As the instructions suggest, when you've worked out what the top and bottom limit screws are draw a diagram you can glance at while you work, or mark the mech since, if you're anything like me, you'll keep forgetting.

I eventually found that I could get my shifts to work perfectly when pulling on the cable by hand, but I can't change with the lever - it's attached to a Tiagra STI lever. I couldn't work out if they are always a bit feeble about holding on to the tension in the cable, whether I've damaged it (I've had a few crashes) or whether I simply needed to re-tension and re-set my limit screws. However, I was having real problems before getting down to the little ring and now it works perfectly, so I reckoned my set up was about right so I started to suspect the levers.

Any ideas anyone?

dakidcp

Limit screws and cable tension are unrelated, to a large degree. The limit screw for the lowest chainring should be set when the cable is not attached to the mech, and the limit screw for the largest chainring set by exerting the maximum possible tension on the mech, either by manually moving the mech, or by attaching the cable and pulling the cable as hard as you can. Once these limits are set (1-2mm gap from the mech plate to the chainring - inside plate for smallest, outside plate for largest), then reattach the cable with as much tension as you can with the fingers (obviously while not moving the mech), and use barrel adjusters (screw them in as much as possible before reattaching cable, then screw out to increase tension) to make sure it shifts readily between the rings.

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piedwagtail91

is there any road dirt around the limit screw? this area needs to be clean or it can affect the amout of travel if dirt gets on the end of the limit screw.

Chris Welford

Thanks dakid - I understood this in principle but in the heat of the moment I was confusing myself, that a usefully clear description.

I had already moved the mech down - it was set up by the manufacturer, but it was much too high, and with a 1-2mm gap it worked a lot better.