Bontrager 'Magic Ratio' Doesn't Work

P20 · Sep 22, 2008

I decided to get rid of the chain tensioner on the Bonty, mainly for the looks, partly because i never liked the damn thing.
So the 'magic ratio' of 34:17 was sourced. King Steel cog, Goldtec 1/8 34t ring, half link chain to allow for fettling.
Set it up with a bit of slack in the chain, the chain could hit the chainstay :roll: So i took one link out, it was so damn tight that after forcing it on it wouldn't run properly :evil:
With the 16t original sprocket back on, its great, smooth and looks fab

Just hoping my legs can handle the 34:16 ratio :shock:

Agency_Scum · Sep 22, 2008

[ polite cough ]Half link?[ / polite cough ]

orange71 · Sep 23, 2008

this guy has them:

http://cgi.ebay.co.uk/3-32-HALF-LINK-si ... 286.c0.m14

gil_m · Sep 23, 2008

Weird, always thought the magic ratio was 36~18T but must admit I have never tried it

Don't worry to much about a tight chain, assuming everything is new the chain will stretch enough after a couple of rides

Good to know the "old dear" is still going strong

Max P · Sep 23, 2008

Rememebr the 'magic ratio' is always a 'bodge' (even if a well calculated one

) and will never allow the fine-tuing that makes for a perfect set-up, especially when things start to wear (ie stretch).

Agency_Scum · Sep 23, 2008

Also there's always this available here.

P20 · Sep 23, 2008

It got one of these half link chains on, so it was just half a link i took out.
It was unbelievably tight with the 17t, you couldn't install the wheel with the chain, wrapped around the cog and the chainring :shock:
I resorted to my favourite strengths, brute force and ignorance, chain on the ring, part on the cog and used the wheel to force it on the cog. Its actually taken a shaving off the steel king kog :shock: The cog is still usuable.

Might do some more research into the actual magic ratio, given Gils 36:18

P20 · Sep 23, 2008

Agency_Scum":1fmmldpn said:
Also there's always this available here.

Its running a Chris King SS

mtbfix · Sep 23, 2008

Er, chain tensioner? Magic ratio is a fantasy as chains wear. Eno hubs are nice but require brake resetting as the chain stretches and the hub has to be rotated further. A chain tensioner is no fuss, minimum visual impact and assuming vertical drop-outs the wheel goes back in the same place every time. IMO

P20 · Sep 23, 2008

I'm wanting away from the chain tensioner. It is mainly an aesthetic thing, but also i've hated the particular one i have from day one, because its shocking build quality/high price :evil:
Looks superb without the chain tensioner too

Bontrager 'Magic Ratio' Doesn't Work

P20

Agency_Scum

orange71

gil_m

Max P

Senior Retro Guru

Agency_Scum

P20

P20

mtbfix

Senior Retro Guru

P20

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