Triple double conversion

larkim

I've converted a road bike (Triban 3) with a triple front mech and shifters to a claris double mech and shifters.

The big ring is mounted on the outside of the spider, with the smaller mounted on the middle position. The inner 5 bolt BCD is now empty.

This means that the chainline on the big ring is pretty poor in the higher (bigger cog at the back) gears and I've had the odd occasion where the front mech has dropped the chain in between the bb and the spider.

As a thought, to solve the inner dropping I though maybe there'd be something like a bash guard that I could mount there, but can't find either a 74mm bashguard that is big enough or a 130cm BCD that I could mount inside of the 39T ring that isn't a 52T sized thing.

I don't think I can use spacers to bring the chainline inwards because the spider needs the big ring mounting on the outside.

Is outer / middle the right choice for the cheap triple to double conversion, or should I have gone middle / small and sourced a 74mm chainring for the 39T ring instead?

Just to say I think I've tuned the position of the front mech as well as I can, in terms of height, lateral direction and limit screws (though it is possible that that could be improved).I am reasonably confident about it for the moment though.

pangolin

Dog fang? https://www.spacycles.co.uk/m2b0s124p2695/DEDA-ELEMENTI-Dog-Fang

larkim

Oh, good shout. Looks like a cheap and easily usable option!!

dj58

Getting a good chainline is going to be an issue if you are still using the O.E. triple BB and crankset spider. Your suggestion to use the middle and inner ring positions may have been a better option if you can source the ring size and BCD you want to use. As a matter of intersest did you look into the cost of a compact double crankset and matching BB? Sometimes a complete crankset works out cheaper than buying separate chainrings.

First.Aspect

What you need to do is search eBay for a "rim brake crank set" and you'll pick up a bargain.

larkim

https://forum.bikeradar.com/discussion/comment/21071102#Comment_21071102

£20 for two rings seemed a decent enough price! Can't find one to go on the 74BCD inner though.

Actually put the fang on last night and when son went to ride it the chain still dropped, so I took it out and it became clear that the inner ring was pretty worn too which I'd not spotted - had only replaced the big ring up to yesterday. Ordered for £8 a new 39T inner ring and will see how that works.

Looked at cranks but when I checked I should be able to do the crank stuff for about £30 I was happy that that was better value than a whole crank.

Option 3 is to whack the old third ring back on just in case, even though it won't be used.