Author Topic: Chain hitting chainstay  (Read 259 times)

steveparry

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Chain hitting chainstay
« on: July 13, 2017, 07:12:08 PM »
I bought this bike recently; barely used since it was built up in 2011ish: https://photos.app.goo.gl/2qmyjJRyDQatgsTx2  The chain hits the chainstay prompting me to think it may have too many links. The middle chain ring is quite small; 32 tooth. So I guess it may be expected. I don't know how to check what chain tension there should be though. If anyone has a tip I'm all ears. If it is normal can anyone recommend a chainstay protector I could attach with cable ties. Thanks, Steve

mickeg

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Re: Chain hitting chainstay
« Reply #1 on: July 13, 2017, 10:54:11 PM »
You will get chain slap on most derailleur bikes, it is not an issue of the size of the chainrings.  When you hit a bump in the road, if you were not pedalling at that time (pedaling puts tension in the upper part of the chain) then gravity will prevail and the chain will go down towards the chainstay, impact it, and cause paint nicks.

If you can put the chain on the biggest sprocket in the rear and largest chainring in front and have almost no extra abilty of the rear derailleur to take up any more slack, then you have the right length of chain.  But if you could remove two or more links and still be able to put the chain on the biggest and biggest, you could take out a few links.  If you can't get the chain on the biggest and biggest, you need more chain because if you accidentally tried to shift into that gear you could jam things up if your chain is too short.

On my most recent build, I used black electrical tape.  Photo attached.  In this case, the frame is Titanium, no paint on it.  I did not want the steel chain causing nicks in the Titanium so I put on a strip of electrical tape.

I also attached a photo of another bike I built up a year ago, red paint.  This frame also has a piece of black electrical tape on the chainstay for the same purpose.

You can buy more expensive chainstay protectors, but I find a piece of black electrical tape works fine.

If you put fresh paint on the chainstay, let it dry for quite a bit of time (maybe a week or more) to make sure it is fully hardened before you put any tape on top of it.

Danneaux

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Re: Chain hitting chainstay
« Reply #2 on: July 13, 2017, 10:58:27 PM »
Hi Steve!

I usually size my chains by placing the chain on the big-big combination (cog and chainring), then pull the chain ends to meet, then add two links before cutting (per Shimano's instructions). This ensures the chain will be long enough in the most demanding state while being minimal in length to keep chain tension reasonably high to prevent chain slap in the (largely avoided) little-little combination.

Keep in mind, extreme cross-chaining (i.e. big-big and little-little combinations) leads to rough running and greatly increased drivetrain wear thanks to the extreme angles involved, so best avoided in actual use. With most 9-sp transmissions, the secret to long life is to use cogs 1-5 with the small chainring, cogs 3-7 with the middle chainring, and cogs 5-9 with the large chainring to minimize chain deflection.

You'll also want to make sure your B-tension screw is adjusted properly so the upper jockey pulley will clear the large cog in the big-big combo, yet not be so far away as to adversely affect shifting. I generally go for about a 5mm-6mm gap (also per Shimano's instructions).

Looking at your photo, I would suggest shortening the last bit of cable housing as it goes into the derailleur. You should be able to get a straighter shot at it. Big score, lovely bike! :)

As for chainstay protectors, I ordered an M:Part carbon chainstay protector to go with my 2011 Sherpa. It attached with adhesive on the back as well as a couple cable-ties. It held very securely and did a nice job protecting the 'stay. I am sad to see it no longer appears to be in SJS Cycles' current inventory. Some of my other bikes have adhesive-backed stainless chainstay protectors. While other people are happy with "LizardSkinz" style neoprene sleeves, I tend to avoid them because I have found they can trap moisture and even grit beneath, causing problems over time. I've also used clear plastic protector tape, but found it can become pitted and looks pad over time with continued chain slap.

Finally, I've found Shimano's "Shadow" series of rear derailleurs are more resistant to chainstay slap because the upper pivot is fixed, rather than spring-loaded.

Best,

Dan.
« Last Edit: July 13, 2017, 11:55:29 PM by Danneaux »

steveparry

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Re: Chain hitting chainstay
« Reply #3 on: July 14, 2017, 01:41:56 PM »
Thanks so much - such great support on this forum! Steve

jags

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Re: Chain hitting chainstay
« Reply #4 on: July 14, 2017, 10:08:35 PM »
i don't think i ever had chain hitting chainstay i suppose its possible but it never happened to me.if you look at mikes  rear mech thats the way it should look when your in the big chainring up front and smallest cog at reay  ;)
keep your chain spotless clean good lube is the trick for perfect shifting triflow or progold is my choice .

jags