E-type mechs, mounting question

ishaw

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I know that they mount via the BB in place of a spacer, but is that all there is to it? I've seen frames with a mount on the frame but I don't have one and wondering if it will all be a bit flimsy without it being held by more than just the BB mount.

Enlighten me please.
 

CassidyAce

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I've only ever had one E-type front mech and it was many moons ago. Like yours, my frame didn't have mounts on the seat tube but the front mech did have a tough, horizontal plastic piece with a semicircle cut out to fit around the seat tube and prevent gradual rotation of the front mech (like the one in this current ebay listing: HERE). I can't remember having any difficulties with it but that horizontal piece did collect dirt, leaves and debris. Like you, I would be suspicious if there was nothing more than the BB fixings to resist the rotational force of the cable pull.
 

ishaw

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Thanks, I suspected as much. Putting a band round the seat tube for fixing means I may as well use a normal mount mech I guess. Good to know though, as I'm sure I'll have a frame with the mounts needed one day (think I did have an orange once actually).
 

jimo746

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My Orange P7 originally came with an e-type front mech, and had the bit on the seat tube for it to bolt to.
I can't see why it wouldn't still work without being bolted to the seat tube though, I use a Gamut chain guide on one of my bikes that is simply held in place by the bottom bracket, never had an issue with that.
Ultimately though you'd probably be better off with a regular clamp-on style front mech, a low clamp/top swing one if that suits better?
 

CassidyAce

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My Orange P7 originally came with an e-type front mech, and had the bit on the seat tube for it to bolt to.
I can't see why it wouldn't still work without being bolted to the seat tube though, I use a Gamut chain guide on one of my bikes that is simply held in place by the bottom bracket, never had an issue with that.
Ultimately though you'd probably be better off with a regular clamp-on style front mech, a low clamp/top swing one if that suits better?
Presumably the chain guide is not subject to cable tension in the same way as a front mech. That would make it safer. However, a front mech is subject to cable tension, pulling to the rear of the axis of the BB's spindle. The cable tension would create a rotational force, tending to rotate the mech on the ring that slips over the BB, and the greater the cable tension, the greater the rotational force. Without being anchored to the seat tube in some way, it's just friction created by the BB fixings that prevents the rotation of the front mech. If that friction is, or becomes, insufficient, the mech will tend to rotate—and, if it does, you have a spot of bother. Anchoring to the seat tube negates the risk.
 

d8mok

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If it didn’t need a bolt I’m sure they wouldn’t have used one. As above it’s different to a chainguide and if it moves a tiny bit it’ll not work.
 

jimo746

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I guess the bolt helps with rotational alignment, I don't imagine it would take much load. In my experience the bolt isn't needed as the bottom bracket keeps things in place, seen a few bikes with these type of mechs and no frame provision to bolt them to.
 

TOMAS

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So I have an XTR M95x e-type mount (the one with the carbon plate) on my Fuquay, you DEFFO need the top mount (seat tube bolt) for it to work correctly in my view. It's waaay too flimsy without, they can be an utter bitch to setup too, i'm a full-time cycle mechanic and have to admit it took me a while to get mine bang-on! You also have to have near perfect chainline for them to work correctly, very tight tollerance than the usual band mount jobbies.
 
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