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Chain length Query

by nsmithson2010
Wed, Aug 10, 2016 11:59
8

Morning All

I want to put a more hill friendly cassette on my Boardman Road Comp, currently the max tooth is a 25 but living in south wales i cannot avoid brutal hills (in fact to get home i have a nast climb that averages over 18% and peaks at about 25% up to the house)

Firstly i'm pretty certain that the deraileur will accept a 28 but if not please shout straight away, its a 105 deraileur as fitted to this:

http://www.bikeradar.com/gear/category/bikes/road/product/review-boardma...

Normally i would happilly put a new chain on with the new cassette but the one on there now has only done about 100 miles and is in really good condition and money is not the best at the moment.

So here is a little pic of the rear deraileur in the 25t and the front in the 50t (Big, Big), i know this is not a gear that should be used but sometimes around here i get plenty of little steep bits that chainging down the front and back up immediately after becomes counter intuitive.

//i63.tinypic.com/2rgdzxc.jpg)

My question is looking at the chain and deraileur position here, does it look like i could safely get away with going to a 28t (+3t) without a new chain?

Thanks in advance

If you're new please join in and if you have questions pop them below and the forum regulars will answer as best we can.

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8 comments

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TypeVertigo | 8 years ago
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A Shimano 105 RD-5700-SS "should" work fine with 30T, but in my experience it has trouble at the extreme cog combos when paired with a 50/34T compact crank (it works great with a 46/36 CX crank). I replaced mine with a mid-cage GS unit instead; works better.

As for chain length, I'd advise a new, properly sized chain. Two more links ought to do the trick.

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nsmithson2010 | 8 years ago
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Thanks All for your advice and comments, i'm going to order the cassette and give it a bash and see what we are looking like with it on. I don't want to leave it too much longer to order as it's on sale atm

Thanks Again

Avatar
BlindFreddy | 8 years ago
0 likes

Having done this  a 28 works fine. Cann't comment on 30. Need longer chain so splice in a couple of links, LBS will have a few links lying around. However it is only a minor improvement. May l suggest you put a Mtb 11-36 cassette on the back along with 9 speed Mtb long mech and a new chain. If that is insufficient, White Industries make a 24/48 chain set.

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Hxs | 8 years ago
2 likes

I think your chain should be long enough.
3T on the full circle cassette only need 2t more on chain (as the chain does not fully wrap around the cassette.

You can quickly check by grabbing a part of chain and pull it together to make it like there are 2 links missing and see how it goes.

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vonhelmet | 8 years ago
0 likes

The SS mech will take up to a 30t cassette. I don't think that chain is long enough to go to a 28t, though. Besides, if you're changing cassettes you should change chains anyway, wear and that.

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huntswheelers | 8 years ago
0 likes

you'll just get away with a 28t or go to a medium cage...if you are swapping out the cassette...new chain is good practice....see VeloUSA post on sizing....

Avatar
VeloUSA | 8 years ago
2 likes

Go here for chain length sizing. Equation is simple to understand and follow.

http://www.parktool.com/blog/repair-help/chain-length-sizing#article-sec...

Avatar
mike the bike | 8 years ago
0 likes

 I would say the 28 cog will be a comfortable fit on your bike, in fact you could probably manage a 30, which would compensate for your 36 tooth inner ring.  And the best of luck on those Welsh hills.

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