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 Post subject: BB Mounted Front Mechs
PostPosted: Sun Jan 29, 2012 10:22 am 
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Location: High Peak, Derbyshire
Does anyone have experience with the above?? Looking for a front mech for my build and considering getting a BB mounted one, any pro's and con's to this idea? Would I be better off sticking with a traditional post mount one??


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PostPosted: Sun Jan 29, 2012 8:19 pm 
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Are you talking about an e-type front mech? (google them)
If so generally there are 2 mounting points, 1 is putting the BB through the mech and screwing it into the frame, then there is a small hole above the BB mount. You put a bolt through that hole and screw it into the e-type mount on the frame.
If you don't use the top bolt the derailluer will flex alot and not change properly.
If your determined to use an e-type front mech on your non e-type frame you can use one of these instead.
http://www.chainreactioncycles.com/Mode ... odelID=745

It's what I used on my partners bike, it could only use an e-type front mech, but the e-type bolt mount had been ground off.


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PostPosted: Sun Jan 29, 2012 10:34 pm 
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I shall more than likely be using a top-pull e-type front mech, with the adapter in the link, on my other cro-mega as I'm fitting Maguras and will have a spare cable-stop...


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PostPosted: Sun Jan 29, 2012 11:24 pm 
retrobike rider
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isitafox wrote:
Does anyone have experience with the above?? Looking for a front mech for my build and considering getting a BB mounted one, any pro's and con's to this idea? Would I be better off sticking with a traditional post mount one??

I think generally yes, unless your frame is designed for it. I have one on my 98 E4, but I notice that most 98 E4s owners have fitted standard fms.

Remember that you need an E bottom bracket as well, because a standard bb would be skewed outboard, and position the cranks further out than the centre of the mech's operating range.


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PostPosted: Sun Jan 29, 2012 11:47 pm 
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Anthony wrote:
isitafox wrote:
Does anyone have experience with the above?? Looking for a front mech for my build and considering getting a BB mounted one, any pro's and con's to this idea? Would I be better off sticking with a traditional post mount one??

I think generally yes, unless your frame is designed for it. I have one on my 98 E4, but I notice that most 98 E4s owners have fitted standard fms.

Remember that you need an E bottom bracket as well, because a standard bb would be skewed outboard, and position the cranks further out than the centre of the mech's operating range.


You can combat the BB issue by using a 73mm BB, putting the right spacers in the right place, and then getting the right length axle to suit. I have done this sucessfully, but my mate owns a bike shop and quite happy for me to go in there and try out half a dozen BB's to get the right one :D


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PostPosted: Mon Jan 30, 2012 7:22 am 
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Ah right, didn't realise you needed a specific frame to fit as they look so convenient to use! Cheers for the info guys!


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PostPosted: Mon Jan 30, 2012 10:32 am 
retrobike rider
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FST4RD wrote:
Anthony wrote:
Remember that you need an E bottom bracket as well, because a standard bb would be skewed outboard, and position the cranks further out than the centre of the mech's operating range.


You can combat the BB issue by using a 73mm BB, putting the right spacers in the right place, and then getting the right length axle to suit. I have done this sucessfully, but my mate owns a bike shop and quite happy for me to go in there and try out half a dozen BB's to get the right one :D

Yes, that works on the drive side (but only if your bb shell is a 68 ), but I'm not so sure whether the adapter would work properly, and I can't get my head around whether a 68 or a 73 adapter would be better


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 Post subject:
PostPosted: Mon Jan 30, 2012 1:15 pm 
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...though there's a very easy way to find out :wink:


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PostPosted: Mon Jan 30, 2012 1:21 pm 
retrobike rider
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We_are_Stevo wrote:
...though there's a very easy way to find out :wink:

Easy yes, but not necessarily pain-free. It hasn't happened to me, but my trusted LBS adviser said if the adapter isn't located properly onto the bb, there can be enough joggling about to damage the threads on the drive side of the frame. He could have been exaggerating I suppose, but I wouldn't risk it myself.


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 Post subject:
PostPosted: Mon Jan 30, 2012 3:05 pm 
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Location: Heathfield, East Sussex
Anthony wrote:
We_are_Stevo wrote:
...though there's a very easy way to find out :wink:

Easy yes, but not necessarily pain-free. It hasn't happened to me, but my trusted LBS adviser said if the adapter isn't located properly onto the bb, there can be enough joggling about to damage the threads on the drive side of the frame. He could have been exaggerating I suppose, but I wouldn't risk it myself.


What's to do wrong?

You have a f*ck off big curved mounting bracket for the derailleur that you bolt up to the BB shell with your E-type BB ( http://www.ebay.co.uk/itm/Truvativ-Squa ... 19cceaa49a ), you bolt your Problem Solver ( http://www.chainreactioncycles.com/Mode ... odelID=745 ) to the seat tube and bolt said curved bracket to it - job done, n'est pas?

Assuming everything lines up correctly of course... :wink:


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