Splitting cassettes

[sittingbull]

I'm looking at fitting a 9 speed 11-32 cassette onto a 7 speed HG Compact hub body by removing one cog and one spacer.

It's the 32 cog I'm looking to remove making the cassette 11-28, leaving the ramping from one cog to the next "as is".

I know this is possible with a Shimano HG50 11-32 cassette as all cogs can be "split".

Anyone know if it's possible with a SRAM PG950 11-32 cassette? (I'd rather use the SRAM).

Any help appreciated

 

[Brommyboy]

Unsure quite what you intend doing, but the spacers for 9 and 7 speed cassette sprockets are different thicknesses, so you may well have to swap all of them over too. Your gear change lever will need the correct spacing on which to operate.

 

[SatNavSaysStraightOn]

@Nigelnaturist do you know?

 

[T.M.H.N.E.T]

Why not just buy a 7 speed 28-11?

 

[Nigelnaturist]

Why not just buy a 7 speed 28-11?

No fun in that.
@sittingbull as far as I know SRAM have screws instead of rivits, all the 7/8/9 sp cassettes I split all had individual cogs once split.
I got 8sp cogs to work on a 7sp set up using 7 cogs and 7sp spacers.
These are the dimensions of 7 to 10sp cassettes spacers and sprockets in mm.

You can see that 8 and 9 sprockets interchange pretty well only being 0.02mm different even 7 and 8 are only 0.05 so again are interchangeable but the shifting may suffer, the biggest difference is in the spacers 9sp to 7sp of 0.59mm this will cause problems, so use use the 7sp spacers, and the 9sp cogs, 7 of them on a 7sp. It will work but the shifting may not be perfect.

 

[sittingbull]

Some very helpful replies, all appreciated thank you

A little more background info may help me explain a little better:

I intend building a lightweight steel road bike from a suitable frame, likely to be either 531 professional or 531 competition (I bought one complete 531c bike which turned out to be too large but provides some useful donor parts - including wheels with a 126mm HG 7 speed hub). From what I've read, both 531c and 531p are unsuitable for cold setting. Hence my wish to optimise the potential of the 7 speed hub.

A 7 speed cassette is 31.9mm overall width, a 9 speed cassette (minus one sprocket and one spacer) is 32.16mm overall width, that's just 0.26mm wider. A little research has told me that using this modified 9 speed cassette will work in practice on the 7 speed hub, giving me 8 sprockets, with the spacing remaining 9 speed compatible. Hence I can use 9 speed STI shifters (or at least the first 8 indexed positions) and indexing should be perfect.

The reason for my original question is because I know lower end (without the spider) Shimano cassettes can be split. However I'm uncertain about SRAM, I've got an 8 speed SRAM cassette which looks like the sprockets are separate, but I'm not confident I could accurately drill out the pins. So the info about screws rather than rivets (@Nigelnaturist ) is particularly helpful However one seller has told me the PG950 has a spider , but another says it has pins

I hope I've addressed the 7 speed 11-28 cassette suggestion (@T.M.H.N.E.T), I've already got 9 speed STI's. Should I decide to retain the down-tube shifters then this would be the simplest solution

I guess I'll have to get the SRAM cassette to see what looks possible, providing I don't butcher it I can always use it as a spare for the MTB

 

[SatNavSaysStraightOn]

Sadly I only have an 8 speed SRAM cassette in the house which I could check on tomorrow if that would help.. Can't guarantee that a 9 speed would be the same but @Nigelnaturist is usually accurate on these matters... He takes enough cassettes apart

 

[Nigelnaturist]

@sittingbull exploded diagrams of almost everything SRAM bar cassettes, according to this picture it should be, this the 990 next to the 950

 

[sittingbull]

As I understand it, lower end Shimano cassettes can be split by filing down (or grinding) the heads off the 3 rivets, then splitting the sprockets/spacers with a screwdriver. Any SRAM cassette using screws will hopefully be easier to split. On the 8 speed SRAM cassette I examined I don't remember seeing any screw-heads.

 

[Nigelnaturist]

As I understand it, lower end Shimano cassettes can be split by filing down (or grinding) the heads off the 3 rivets, then splitting the sprockets/spacers with a screwdriver. Any SRAM cassette using screws will hopefully be easier to split. On the 8 speed SRAM cassette I examined I don't remember seeing screw-heads.

you are correct with the shimano ones, the screws I believe are recessed hex heads, but don't hold me to that.

 

[Nigelnaturist]

This might make it clearer

 

[Big_Dave]

Sram PG950 9 speed and PG850 8 speed both have one allen screw that holds the whole cassette together

 

[sittingbull]

That (@Nigelnaturist ) looks like 3 slot headed screws, requiring removal with a flat headed precision screwdriver.

Useful info (@Big_Dave ), I've just taken this of my PG850, can you confirm it's an allen screw? I thought it was circular rather than having any flat sides.

 

[Nigelnaturist]

is this not the same

 

[sittingbull]

Possibly