freewheel advice needed please.

[dablad75]

Hi, apologies if this is a stupid question!
Recently bought a 1978 gazelle champion mondial. It's got a 600 shimano arabesque groupset. I want to upgrade the rear freewheel to a kinder gearing for eroica. Currently it's 14-21 and wanted 14-28 or 14-32, is this possible? I'm also a bit stumped on how to remove it, can anyone offer any advice? I bought a freewheel removal tool but it doesn't fit? Sorry if this is basic stuff!

 

[Retro Spud]

Re:

What tool did you buy,

I believe you need on of these http://www.jensonusa.com/Freehub-Cog-To ... mover-2PRG

sorry can't help yah on your other question

 

[originalshinkicker]

Hi, that looks like a 6 speed UG cassette on a freehub, not a screw on freewheel. You need 2 chain whips - one to hold the sprockets still and one to place on the smallest sprocket to unwind it (normal thread). The smallest sprocket screws off and the remaining 5 will slide off the splines on the freehub body.

Looks like it has a dust cap missing from the freehub body as I can see the hub bearings?

You can get a lower ratio cassette but you will need to check your rear mech to see what it can handle, some short cage mechs will do 26T, some 28T but 32T will almost certainly require a long cage mech

 

[dablad75]

Ah thanks, I assumed due to the age that this was a freewheel (I'm new to the vintage stuff so excuse my ignorance). I removed the dustcap as I thought maybe that's where the tool fitted, it's back on now. I have two chainwhips so will hopefully be able to remove the cassette. How do I tell if I have a long or short cage mech?

 

[daccordimark]

Looking at your photo it's a short cage mech but if you measure the distance between the jockey wheel bolts that will tell you. They do vary a bit but for reference my old Suntour short cage mech is 57mm and a modern Campag one is 55mm.

Mark.

 

[t47b]

Re:

I was just working out the very same thing for a 14-28 freewheel

So...

a simple formula: add up teeth on the biggest chainring and sprocket and then deduct the sum of the smallest chainring and smallest sprocket.
(Big Chainring + Big sprocket) – (Small Chainring  + Small sprocket) = rated capacity   (T)
According to Shimano, their derailleur’s rated capacities are 45T for long cages and 30T for short cages.

Mine
52+28 - 42+14=80-56=24T

But then again I'm an artist not a mathematician

 

[daccordimark]

Re: Re:

I was just working out the very same thing for a 14-28 freewheel

So...

a simple formula: add up teeth on the biggest chainring and sprocket and then deduct the sum of the smallest chainring and smallest sprocket.
(Big Chainring + Big sprocket) – (Small Chainring  + Small sprocket) = rated capacity   (T)
According to Shimano, their derailleur’s rated capacities are 45T for long cages and 30T for short cages.

Mine
52+28 - 42+14=80-56=24T

But then again I'm an artist not a mathematician

Nothing wrong with the maths there but the maximum sprocket size also depends on the geometry of the mech. If it can clear the teeth of the largest sprocket as it moves under it then you're okay. My Suntour has a stated maximum of 26 or 28 depending on the type of dropout.

Mark.

 

[dablad75]

Thanks for the posts chaps. I measured the rear mech, it's approx 52mm between the jockey wheel bolts. My large sprocket is 52 and 42. Rear is 14-21. 73 -46 =27?? So is this the largest I can go to? Do I need to buy a complete cassette or can you buy the sprockets separately?
Thanks, Dave.

 

[t47b]

Re:

Thanks for the posts chaps. I measured the rear mech, it's approx 52mm between the jockey wheel bolts. My large sprocket is 52 and 42. Rear is 14-21. 73 -46 =27?? So is this the largest I can go to? Do I need to buy a complete cassette or can you buy the sprockets separately?
Thanks, Dave.

First, far be it from me to criticise someone's maths skills, but your second number should be 56

The answer to your sum is not the maximum you can have, it is what you do have, as I said Shimano states that the answer to your sum needs to be under 30T to use a short cage.

My example is what I currently run, and works fine with 14-28, my jockey wheels distance (campagnolo nova record) measure the same as my Shimano 600ex.

The only problem that could occur is the chain on the top jockey wheel could touch the 28 cog, which can be avoided by moving your wheel back a bit in the drop out.

You have a freewheel not a cassette, cassettes are separate cogs, you can buy a complete 14-28 freewheel replacement, you will need the correct tool to remove the old freewheel, dependent on the brand of freewheel.

Read the great Seldon Brown, who knows everything!...

http://www.sheldonbrown.com/free-k7.html

 

[legrandefromage]

If you have access to other parts/ frames, attach the 600 mech to a frame and run wheels with bigger cassettes to see what the max is in the real world. For instance I managed 30t with a later 600 tricolour shortcage without much fuss.

*I have one of those hubs too, someone had tried to take the 'freewheel' off! Pics later if anyone is interested in the internal gubbins.