Thursday, May 20, 2010

Mavic 631 v. 631/2

Not entirely sure what the difference between a Mavic 631 and a 631/2 is? Here are some pics that'll make the difference abundantly clear.


On the left, a 631. On the right, a 631/2. Most of the differences are pretty plain to see. The spider of the 631 narrows gracefully as it reaches its ends. The 631/2's spider largely stays consistent in width. The spider is a little shorter and stockier than the 631, which allows it to run a smaller chainring in the outermost position - down to a 42 I believe.

The crank arm itself is less rounded on the 631/2 as well. It's middle flat section is slightly wider.


The backside. The spider has much less material on the 631/2, with relief work evident on the backside. At the very top of the picture, you may also notice that the 631 has some material taken off the edges of the crank arm, while the 631/2 does not. There's also some material removed on the 631 around the spindle interface, while the 631/2 has none removed.

The 631/2 is quite a bit lighter than the 631 - though it's hardly a lightweight. This can probably be attributed to the shortening and relief work done to the spider.

5 comments:

Fred Blasdel said...

Sweet -- I've got a 631 with a matching bottom-bracket, I'm going to get my ALAN machined for it in a couple weeks.

I bought it without rings at a yard sale, but I just bought a whole bunch of Mavic outers on eBay and it turned out a friend of mine had an outer too. I could really use a Mavic inner if you've got a spare one lying around. Are the normal chainring spacers 3mm wide? I need to get a set...

How did you get that track ring on your 631 without a double set of spacers? Did you remove the original steel mounting posts? What would you replace them with?

A french seller just listed a pile of vintage Mavic parts on eBay, I thought you'd be interested.

Anonymous said...

"How did you get that track ring on your 631 without a double set of spacers? Did you remove the original steel mounting posts? What would you replace them with?"

The steel 'posts' unscrew from the spider with an Allen key, a single ring can then be mounted directly onto the spider using the chainring bolts -if you have them. If not it's a standard metric size -you'd have to work out the length of bolts to use.
This is a feature of the 631 design, it can easily be reconfigured as a single double or triple chainset.

Done it myself.
Simon

Leighton said...

Certain that you've seen this, but if not, perhaps of interest:
http://pardo.net/bike/pic/mobi/d.mavic-631-starfish-crank/

Anonymous said...

The 631 is designed for sigle or double rings with existing hardware.

See here:

http://picasaweb.google.co.uk/dmczone/MAVICSSC631Crankset#slideshow/5329046762495967266

Anonymous said...

http://picasaweb.google.co.uk/dmczone/MAVICSSC631Crankset#slideshow/5329046762495967266

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