baron von greenback
Retro Guru
How do you work out what size front derailleur you need do you just measure round the down tube and that's it or is it more complicated than that cheers
Front derailleur
- Thread starter baron von greenback
- Start date
bikeworkshop
Old School Grand Master
A few details:
Tube dia: 28.6 (classic) 31.8 34.9
Large ring size: Mtn- 42 to 48 Road 52
Double, triple
Cable pull - top or bottom
Cable pull ratio, road, Mtn,
Cable pull compatibility 789, 10, 11.
I'm sure there's more
In around 2010, shimano web ordering offered 140 varieties...
It's dropping back now with the rise of 1x and the decline of triple.
Tube dia: 28.6 (classic) 31.8 34.9
Large ring size: Mtn- 42 to 48 Road 52
Double, triple
Cable pull - top or bottom
Cable pull ratio, road, Mtn,
Cable pull compatibility 789, 10, 11.
I'm sure there's more
In around 2010, shimano web ordering offered 140 varieties...
It's dropping back now with the rise of 1x and the decline of triple.
I think the only details you missed were:
High or low band (I believe it may be referred to as top or bottom swing).
You also have direct mount variations and e-type.
I think I've also seen side pull as well, whatever that is.
I've seen talk and markings on front mechs relating to seat tube angle but I've never had an issue.
It was simpler back in the day, I'm sure front mechs will make a comeback, after all, it's an extra component to sell, as are chain rings.
High or low band (I believe it may be referred to as top or bottom swing).
You also have direct mount variations and e-type.
I think I've also seen side pull as well, whatever that is.
I've seen talk and markings on front mechs relating to seat tube angle but I've never had an issue.
It was simpler back in the day, I'm sure front mechs will make a comeback, after all, it's an extra component to sell, as are chain rings.
baron von greenback
Retro Guru
It's for a Marin Indian fire trail triple crank top pull I want a xtrm900
bikeworkshop
Old School Grand Master
IFT aluminium - i think in 93 it was 34.9 seat tube, but dropped to 31.8 some time later iirc.
If that's the size,
it's "m900, 34.9, top pull"
Ideally you'd measure with verniers, but you can calculate the circumference by wrapping a piece of paper round and marking it, measure, and divide by Pi.
The seat clamp is usually the same size, and often has diameter stamped into the underside, worth a look.
If that's the size,
it's "m900, 34.9, top pull"
Ideally you'd measure with verniers, but you can calculate the circumference by wrapping a piece of paper round and marking it, measure, and divide by Pi.
The seat clamp is usually the same size, and often has diameter stamped into the underside, worth a look.
baron von greenback
Retro Guru
Cheers mate I have a look
The only other couple of details missing, but will not really be a concern is chain-stay angle and BB shell width.
Only a concern when dealing with larger chain rings for a MTB FD (like in old school DH) or fitting a FD to very old frame with very slack angles.
Diameters of the clamp is fairly standard, since about 2000 the 28.6mm for (older) skinny steel MTB is gone now and replaced with a plastic spacer and you fit 31.8mm (normally included in NIB). 31.8mm and oversize 34.9mm is / was for things like oversized AL seat-tubes and suspension bit and wider tyres, and also the somewhat wider 73mm BB shells like on GTs, Cannondale and a few others like Gary Fisher if I remember right.
The few Marins I had were all 31.8mm if I remember right.
Personally find older MTB FDs are more friendly if you have some non-standard wide ratio type double thing up front.
On the road side. A yawn fest. Nothing exciting.
Only a concern when dealing with larger chain rings for a MTB FD (like in old school DH) or fitting a FD to very old frame with very slack angles.
Diameters of the clamp is fairly standard, since about 2000 the 28.6mm for (older) skinny steel MTB is gone now and replaced with a plastic spacer and you fit 31.8mm (normally included in NIB). 31.8mm and oversize 34.9mm is / was for things like oversized AL seat-tubes and suspension bit and wider tyres, and also the somewhat wider 73mm BB shells like on GTs, Cannondale and a few others like Gary Fisher if I remember right.
The few Marins I had were all 31.8mm if I remember right.
Personally find older MTB FDs are more friendly if you have some non-standard wide ratio type double thing up front.
On the road side. A yawn fest. Nothing exciting.
baron von greenback
Retro Guru
Cheers mate all my stuff will be retro MTB stuff late 80 to late 90 frames orange p7 zaskar le. Orange c16 Marin fire trail Klein pinnacle Klein mantra that's what I be building up to now cranks kooka cooks xtrm900 got a crank with springs on either side can't remember the name derailieurs with be xtrm900 or proshift billets and Paul's if I can get my hands on some also I need to work out BB but how do you know how to match to crank if say the shell is 68mm is there a list or can you measure some how cheers
baron von greenback
Retro Guru
So if the seat post is 31.6 that means I would need a 34.9 front derailleur is that right and if seat post is 27m I would need a 31.8 fd with a shim in it cheers
First shell width to get right.
2nd spindle / axle length. This will depend on the crank and your frame. An old database is on Sheldon Brown, but best pop the question for your crank here. You can already measure what kind of clearance or Q-factor you need by measuring from the BB centre to back to the chain-stays by about 185mm, then measuring across the chain stays at this point, and adding on about 10mm (5mm or so crank clearance either side). Q-factor will be typically about 160mm - 170mm region or even over in special more modern cases.
In general straight arm cranks require a spindle / axle in 120mm region, and later "profiled" cranks that have a distinct curve in them are 107mm - 115mm.
2nd spindle / axle length. This will depend on the crank and your frame. An old database is on Sheldon Brown, but best pop the question for your crank here. You can already measure what kind of clearance or Q-factor you need by measuring from the BB centre to back to the chain-stays by about 185mm, then measuring across the chain stays at this point, and adding on about 10mm (5mm or so crank clearance either side). Q-factor will be typically about 160mm - 170mm region or even over in special more modern cases.
In general straight arm cranks require a spindle / axle in 120mm region, and later "profiled" cranks that have a distinct curve in them are 107mm - 115mm.
