Wednesday, November 28, 2012

Do your homework and research; or else, face the Chain Reaction

Recently, I posted about replacing the chain and the rear cogs on Brahma. I replaced the stock SRAM 7-speed chain with a SRAM PC-1071 3/32" 10-speed chain. I had some troubles with it, which included slipping of the chain on the rear cogs (though they were brand new) and the front sprocket. I also felt a few more links should be taken off that chain. I was not too thrilled with the recommendation made by REI Dallas. The chain was expensive and it did not give me the desired results. It was the wrong chain to use.

I got a second opinion from a really popular bike shop in Fort Worth. They took a couple of links off; test rode the bike and gave it an A-okay. I brought the bike back to Irving and found out that didn't do the trick either. Alas!

However, one good thing that came out of the trip to Fort Worth was that, that particular bike shop showed me that there can be differences in the size of the rollers in a 10-speed 3/32 chain and a 7-speed 3/32 chain. The rollers in the 10-speed chain are narrower. This could cause the chain to slip.

See picture below; the chain on the top is the SRAM 10-speed 3/32 PC-1071 chain. The one on the bottom is a SRAM 7-speed 3/32 chain; which I bought from Foldabikes.
So, when I got home after my trip to Fort Worth, I decided I will be really brave and put on a different chain myself.

I measured the spare chain I had bought from Foldabikes; measured it to the approximate length I desired, based on a couple of really precise photos from my buddy Fernando of The Dirty Brompton; removed the appropriate number of links, used the quick-link and put on the new SRAM 7-speed chain.


Picture below shows the proper positioning of the chain tensioner - courtesy of Fernando. The chain tensioner is optimally placed when it is approximately at a 20 degree angle from the chain stay or approximately 3" from the chain stay.




No troubles since the SRAM 7-speed chain was installed. Knock-on-wood!

Lessons Learned:

  1. Do your research, in-depth, before deciding what chain/component to buy
  2. Your LBS mechanic may not know about a speciality folding bike, such as a Brompton
  3. All 3/32" chains are not made equal
  4. Ask fellow bloggers who own a Brompton for help. I got some help from Johnny who commented on my earlier post and also lots of help from Fernando, my FB buddy Dan Lenik and a whole bunch of others from the London Brompton Club
  5. Follow your heart
Next up : Replacing the gear-indicator chain on Brahma.

Peace :)


PS.
I have slowed down my posting frequency a bit, due to a variety of reasons. I hope to push it up a notch, when I am ready.

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