Workshop Stories: Chain Measure Tool

[scuzzy]

Well, I think it''l be a bit difficult to measure 306.32mm in any case.  So steel ruler in inches it is.

[Christopher Brunsdon]

Mmmm ... replaced my chain on Sunday it seems it might be too late ... bummer. Using a rather unscientific method of calculating chain length I hung the new and old on the wall using a small hook.

 

To my dismay the old chain was a link longer at the bottom from "stretch" - its an 8spd with only 1300km on it. To be hounest I'm sick this week so I will double check it again this weekend .... aaarrrgggghhhhhh

 

[TreeDodger]

 

 

Just my 87 cents worth:

 

I use a vernier to measure 6 links on the bike. A standard vernier is 160 to 170mm long so 6 links is the max that will fit.

 

1. 6 links = 6 inches = 152.4mm

2. Replace chain after 1/16 inch wear (which is 0.5%)

3. 0.5% of 152.4mm is 0.76mm

4. Round down if you're conservative (153.1mm) or round up if you a cowboy (153.2mm)

6. Hook the vernier pointy bit on the edge of a pin and measure to the edge of the pin 6 links away. If you're below 153.2mm all is well. A vernier measures in 0.05mm increments so this is quite easy. You can even measure to 153.15mm so no need for cowboy tricks.

7. It helps if someone puts some pressure on the pedals to make sure the chain is stretched at maximum and then you can use 2 hands, or just shift to big big combination and measure the chain where the d?railleur pulls it nice and tight.

 

Obvious problem with this method is measurement error because you are only measuring 6 links but I have found that because the vernier has very sharp pointy bits one can make a very accurate measurement.

 

If you can get hold of a JB specially modified blue ruler that is probably still better.

 

If anyone wants I can post some pictures, will have to take them first.

 

Piktar of a vernier: http://upload.wikimedia.org/wikipedia/commons/9/96/Vernier_caliper_new.png

 

TreeDodger2009-09-02 03:57:17

[Tieffels]

I'm also going the vernier route, at the department's workshop they've got verniers that can measure up to 1m i think, and micrometers that can handle about the same. Amazing pieces of equipment, art almost of an era gone by.. 

[Cicada]

It seems to me some of you guys like to "kloof hare"

 

Earlier in the thread I mentioned that I have a "brand new", blue Park Tool, not yet modified, ruler - but alas, no takers!

 

[Dynamix]

Normal 30cm steel rules are at least 31cm long. Usualy they are blank on the flipside. Borrow a tool, make the 2 marks (306.4mm & 308mm) with a scribe and you're set.

 

Hello Jan!