Is using Cassette N-1 a simple trick to give access to modern cassettes on old 7 speed cassette hub?

[biker38109]

In my absence I have got a line on some great 90s mtbs however many are using 7 speed hyperglide. Also for a fraction of the price of so suggested new bikes.

As per this sheldon article it seems a simple matter of removing the smallest sprocket.

Since 34t 7 speed cassettes are none existent, or very rare that I can see, I thought why not just buy an 8 speed (or even greater) with the desired max low gear toothage and take off that highest sprocket. From sheldon it seems 8 would be good as he says there is little advantage to more gears but going above 8 speed would then require a new chain. So stick with 8-1 to avoid that.

In the case of 7 speed it seems cheaper to do that anyway as a 7 speed freewheel design (just for example, not any of the bikes I am looking at currently) at 34t costs £30 while an 8 speed 34t is only £13.99.

So is it a trivial task to remove that sprocket and away you go? Surely if Sheldon recommends it then it is an absolute.

Seems a good workaround vs. holding out for the rare retro bikes that are 8 speed or having to go backwards to freewheel. The majority that have come across my purview on the shortlist seem to be 7 speed hyperglide cassettes.

I would be using friction shifters so should not cause any issue there.

Would the rear derailleur be a limiting factor on size of low gear above a certain point? How big toother could an older RD take max do you reckon on normal 90s 3x7 mountain bike? Would dinner plates out of bounds? No cause to max out the back on 3x but I wonder if this 42t would be ok? That would be the same as the lauded Polygon Xtrada 5 then but at a fraction of the price and rigid frame!!!!

[531colin]

No cause to max out the rear sprocket size on a triple…. But you want to do it anyway?

[531colin]

To take the existing cassette off the wheel you will need cassette lock ring tool and chain whip.
The top sprocket on a cassette is usually (always?) loose, but the next sprocket won’t have the serrations which engage with the cassette lock ring.
You might be able to buy a “top” sprocket ( with serrations and built in spacer) the same size as the 2nd sprocket, that should use a bigger diameter lock ring.
Then the original 2nd sprocket needs to come off the cassette; it may simply be loose, or it may be bolted or riveted. It’s unlikely to be on a spider

[oaklec]

SRAM PG730 7 speed cassettes are readily available in 32t quite cheaply. They are shimano compatible

[rareposter]

That would be the same as the lauded Polygon Xtrada 5 then but at a fraction of the price and rigid frame!!!!

I can pretty much guarantee that by the time you've bought whatever bike you end up with, and the tools, and the replacement parts, and the replacement parts to replace the first ones which didn't fit/work, you will have a bike that costs more than, and is not as good as, the lauded Polygon Xtrada 5.

[cycleruk]

Given the Sunrace cassette you referred to :-
https://www.sjscycles.co.uk/cassettes/s ... ette-1142t.
How about removing the 42 sprocket which leaves an 11/34 seven speed cassette.
[11 / 13 / 15 / 18 / 22 / 28 / 34 ] (assuming that the 42T is a separate cog and not part of a spider.)
You may have to play around with a spacer to take up any slack.
I very much doubt that a 1990's derailleur will accept a 42T sprocket and possibly not even the 34T. ?

[scottg]

To take the existing cassette off the wheel you will need cassette lock ring tool and chain whip.
The top sprocket on a cassette is usually (always?) loose, but the next sprocket won’t have the serrations which engage with the cassette lock ring. [snip]

Some Shimano cassettes have serrated cogs in the first two positions,
for example the 10s 11-32 cassette is like that.

[NickJP]

The top sprocket on a cassette is usually (always?) loose, but the next sprocket won’t have the serrations which engage with the cassette lock ring.

The Shimano 9-speed 11-32 cassette has serrations on both the two smallest cogs (the cogs are 11-12...), so you can run eight of nine on a 7-speed cassette body as a 12-32 without worrying about the lack of serrations. You just need to find a lockring intended for a 12-tooth cog, as the lockring supplied with the cassette for use with the 11t cog is too small a diameter to engage the 12t cog. I have that exact setup on two bikes.

See viewtopic.php?p=1863661#p1863661.

[biker38109]

Given the Sunrace cassette you referred to :-
https://www.sjscycles.co.uk/cassettes/s ... ette-1142t.
How about removing the 42 sprocket which leaves an 11/34 seven speed cassette.

That would defeat the purpose! I would buy it only for the biggest cog.

[11 / 13 / 15 / 18 / 22 / 28 / 34 ] (assuming that the 42T is a separate cog and not part of a spider.)
You may have to play around with a spacer to take up any slack.
I very much doubt that a 1990's derailleur will accept a 42T sprocket and possibly not even the 34T. ?

Well I read that 36t has been cleared successfully on Deore.

See here: https://www.retrobike.co.uk/threads/deo ... et.389852/

I see though that there is no cause to 'push it' if using 3x with a granny. 36 would be sweet.

[biker38109]

To take the existing cassette off the wheel you will need cassette lock ring tool and chain whip.
The top sprocket on a cassette is usually (always?) loose, but the next sprocket won’t have the serrations which engage with the cassette lock ring.
You might be able to buy a “top” sprocket ( with serrations and built in spacer) the same size as the 2nd sprocket, that should use a bigger diameter lock ring.
Then the original 2nd sprocket needs to come off the cassette; it may simply be loose, or it may be bolted or riveted. It’s unlikely to be on a spider

Thanks, I might 'settle' for a middle ground of 36, 8 to 7.

[531colin]

viewtopic.php?t=54328&hilit=nightmare&start=30

link to an old thread where I was messing about re-building cassettes.

In the end I used parts of a 9 speed cassette designed for junior (reduced gear) racing and the rest from a 9 speed MTB cassette (I think....its a while ago!

[biker38109]

viewtopic.php?t=54328&hilit=nightmare&start=30

link to an old thread where I was messing about re-building cassettes.

In the end I used parts of a 9 speed cassette designed for junior (reduced gear) racing and the rest from a 9 speed MTB cassette (I think....its a while ago!

Thanks. Wow you are an old timer here I see. 2011 thread.

Someone wanting a 34t sprocket at the back (assuming a 34t front chainring on a double chainset) is probably better off with smaller chainrings at the front, as with a triple chainset. But most people are only able to think in terms of 'bigger sprockets' in order to get lower gears.

I'm not most people....
I'm old and weak, I like the small roads and the rough tracks in the Dales. I'm running 24, 34, 46 on the front. When 24 front 28 rear is getting marginal, your options for a significantly lower gear are a bit limited.

A man after my own heart! Small front rings, and biking terrain.