Front derailleur with wide throw

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Mike_P

Guru
Location
Harrogate
Is there a front derailleur that will throw to a chainwheel around 50mm from the seat tube (or a way of adopting an existing one). I have fitted a bottom bracket motor to a hybrid and the supplied chainwheel is shaped to overcome the projection of the motor.
IMG_20190202_132250539reduced.jpg

Fitting a further chainwheel, the supplied spider is a 110 BCD, gives an offset akin to a triple chainwheel albeit with the centre chainwheel missing with the extra chainwheel around 50mm from the seat tube.
IMG_20190202_142224619reduced.jpg

My front derailleur, a Shimano Tourney FX51 for a triple chainwheel, does not have enough throw - the outside of the cage is in line with the teeth of the extra chainwheel at full throw.
 

Cycleops

Legendary Member
Location
Accra, Ghana
I think you might have to tackle the problem the other way around. That chainset looks like a bit of a lash up so you might have to consider changing it for one with more conventional spacing. The spacing from the middle to outer might not even work even with a FD with a wider throw.
Maybe someone else will have some better ideas.
 
D

Deleted member 23692

Guest
I've the same motor and whilst I'm running an Alfine 8 speed hub gear I only gears 5 to 8 (with 4 very very occasionally). That's with a 42/18 chainring/sprocket ratio

I honestly doubt you need two chainrings at the front
 
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Mike_P

Mike_P

Guru
Location
Harrogate
I've the same motor and whilst I'm running an Alfine 8 speed hub gear I only gears 5 to 8 (with 4 very very occasionally). That's with a 42/18 chainring/sprocket ratio

I honestly doubt you need two chainrings at the front

Found pedalling unassisted the supplied chainring was being over paced so the extra chainring is for such occasions rather than with motor assistance.
 

Levo-Lon

Guru
Found pedalling unassisted the supplied chainring was being over paced so the extra chainring is for such occasions rather than with motor assistance.


I think you need to find a compromise . Single front seems to be the E-bike standard.
I manage 26 mph tops on my E-bike with a 11-42 and the 15 front going through a bosch geared motor. Which gives assistance to 15.5 mph
I just accept its not a normal geared bike.


That said I've never seen your set up, so maybe a bit of tinkering and a cleaver bit of tinkering may solve this?
Goog luck..
 
D

Deleted member 23692

Guest
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Mike_P

Mike_P

Guru
Location
Harrogate
With the extra chainring behind the spider the offset from the seat tube is down to c 43mm and the relationship of the chain rings is now quite sensible compared to yesterdays ultra wide spacing.

I think your answer might be in fat bikes, and an adaptor for direct mount MTB front mechs..

Thanks - I had noted the direct fit Mechs and those adaptors might be the answer. possibly with an appropriate spacer if necessary, if the existing mech still does not work (not tried resetting it yet but looks a bit and touch).
 
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Mike_P

Mike_P

Guru
Location
Harrogate
Do those chainrings even have shift ramps on them though ?
Good point, but the existing FD has lifted the chain off it (by mistake when I had cabled up the FD but not locked it out of use with just the single chainring)
 
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Mike_P

Mike_P

Guru
Location
Harrogate

Single Track Bikes have the Problem Solver ones listed twice - presumably because their are two basic versions but each listing is unclear as to which it is referencing. I imagine the ones which are £2 cheaper are possibly those for the smaller bottom bracket. The drop down list on each page simply gives a seemingly confusing listing of tube diameters, most duplicated to add to the confusion - have emailed them but to date no reply - they are all listed as in stock supplier which I read as them having none and given the confusing listing they probably have never sold any on line.
Amazon have a RMS branded at £19.79 which looked like a good deal until it materialises it is being sold from Italy with a postage charge of £17.90 :ohmy: so I looked for any suppliers other than £40.51 ebay from the USA of the Origin 8 one and found SJS Cycles have them at £29.99 plus £2.50 postage.
https://www.sjscycles.co.uk/gear-spares/origin8-derailleur-direct-mount-adaptor-black/
Did need also a reducing band for my seat tube so an additional £3.49 as the Origin 8 is not supplied with any reducing parts but still cheaper than the RMS Amazon one and they arrived together yesterday somewhat quicker than Amazon were quoting.
Having already a suitable Shimano derailleur from Wiggle for the vast expenditure of £6.99 I assembled the lot together and found a new problem in that the derailleur is now too far out with the inner chainring rubbing on the cage. Presumably explains why a US seller of double chainrings for that ebike motor sells standard chainrings https://www.electrifybike.com/store/p69/TSDZ2-Double-Chainrings.html as its the concave shape of the supplied chainring that makes it rub on the cage. So a new inner chainring purchased from Spa Cycles to go with the outer but as the ebike is largely for work purposes wearing office clothing I have put it on hold until a chainring guard arrives - seemingly the only UK available ones suitable for the outer chainring are plastic mounted on the crank rather than the chainring so I am awaiting a metal chainring mounted one from Taiwan, superbicycle.shop-uk on ebay.
 
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Mike_P

Mike_P

Guru
Location
Harrogate
The Origin 8 mount worked a treat and the shim actually turned out to be the key as fitted on the bike the derailleur was slightly too far out. I realised that by modifying the shim so that the mount was hard up against the seat tube the derailleur would be correctly positioned.
 
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