Shimano HG70 7 speed Cassette

[TheDoctor]

Hi and thanks for the info. I didn't realise that the cassette has individual sprockets.... I will look into it.

The SRAM cassette is here but I'm yet to put it on..... this cassette's biggest sprocket has 32 teeth and my current cassette has 30.... it does look, by just looking at the cassette against the old cassette, that the 32 might be too big but I'm not an expert so my question is how do I find out if this new cassette will fit, without obviously attempting to fit the new cassette?


youngoldbloke, the link leads to an out of stock item but thanks anyway.

What rear mech have you got? If it's a road one (Sora, 105, Tiagra sort of thing), it'll not work.But equally, a road one probably wouldn't have worked with a 30T either! I'd assumed (possibly wrongly) that you'd have an MTB rear mech (Alivio, Acera, Deore and such like), which should work fine with 32T.
You may need to tweak the screw that sets the angle of the mech - not the high / low limit screws, the other one near where the mech bolts to the frame.

 

[Manonabike]

What rear mech have you got? If it's a road one (Sora, 105, Tiagra sort of thing), it'll not work.But equally, a road one probably wouldn't have worked with a 30T either! I'd assumed (possibly wrongly) that you'd have an MTB rear mech (Alivio, Acera, Deore and such like), which should work fine with 32T.
You may need to tweak the screw that sets the angle of the mech - not the high / low limit screws, the other one near where the mech bolts to the frame.

Hi actually it is a road rear mech, 18 years old though but in perfect working order, see pict. The picture shows the original cassette which, if I recall correctly, was 11 - 21. The current cassette is a 13 - 30

 

[TheDoctor]

Ah, you 'll probably need an MTB mech. Apols - I'd kind-of assumed you already had one.
I like the retro clipped pedals and Biopace chainset. and the fade paintwork - very 80s. That's a Peugeot, isn't it?
Anyway, what I'd do in your position is give it a go, but be prepared to buy an MTB mech. I use an Alivio with the 12-32 cassette, and it works nicely, but any MTB mech will do. CRC have the Acera for half price at £9.99, but even a Deore LX is only £30.

 

[Manonabike]

No problem. It's a Raleigh Vitese.

I will look into the advice given by MartinC, post #12 above, and see if I could buy separate sprockets.... not sure I could find any of the biggest such as 28 and 30.

The thing is I want to keep the bike as original as I can.... I was hesitant to change the cassette but my poor legs could not cope with the hills .... the rest is all original with the exception of brake pads. bar tape, tyres and of course a Team Pro Brooks saddle

 

[Manonabike]

I know that you've ordered a SRAM cassette but for the future - it may look like the cassette is all one part but often they're individual sprockest and spacers held together with rivetted or screwed pins that you can easily remove. Some higher range cassettes may have the bigger sprockets grouped on a carrier but if you buy spare sprockets for the right model of cassette (HG70 etc.) then they should fit. The sprockets have a position on the cassette (denoted by a letter) which you need to take into account - Shimano techdocs on the net will give the detail.

I found the specs for the cassette that I currently have HG70

Unless I misunderstood the specs, it sees that I might be able to change the sprockets!!!! --- While looking for sprockets I can find a few that are listed under Shimano HG70 sprocket 7 speed 17T for example, however, when it comes to the bigger sprockets they just say HG70 sprocket 30T... and this could well be for a 9 speed cassette and that confuses me

 

[TheDoctor]

I can't see why a 9 speed sprocket wouldn't work.The gap is set by spacers, so the sprocket being a fraction thinner should be OK.

 

[Manonabike]

Now, here is something to think about .... according to this great website for old and vintage bikes velobase.com my rear derauilleur can handle up to a max of 28T sprocket, however, my bike has a 30T sprocket and it works perfectly ....

I'm seriously considering to replace some sprockets on my cassette, 6 of the sprockets are in one piece, held together with rivets - how difficult is to separate them? And do I need any special tool for that? Do I need to replace the rivets too?

So many questions .... but with your help, I'm sure I can rebuild the cassette . The information will also benefit other people at some point....


Thanks in advance

 

[MartinC]

From your picture it looks like an old Suntour or a Shimano Exage short road mech. It probably had the theroretical capacity to handle a 28 sprocket (it's the ability of the top jockey wheel to track the sprockets correctly that limits this, the length of the jockey wheel cage will determine how many teeth difference front and back it can handle). It seems to have coped with a 30 OK but 32 may well be a step to far. You can't check this without installing it and trying it. I would guess that it won't.

There is a difference in the thickness of a 9 speed sprocket (7 is 1.85mm, 9 is 1.78mm) but it's marginal so if you use the original spacer you'll be OK. Remember too that you're talking about the last sprocket on the cassette so the derailleur throw isn't controlled by the indexing but by the stop screw on the derailleur itself.

 

[Manonabike]

After doing some thinking I've decided I will upgrade the bike after all..... I wanted to keep this bike as original as possible but my wife asked me yesterday what I was going to do with this bike when I get the "NEW" bike and I just didn't know what to reply - we already have 4 bikes in the shed and there's no room for another one.


I was reading a very interesting thread here and I think I would happy to use the 531 frame and use new components to bring this bike up to date, although I still ride on a regular basis.

I have an idea of what I need to upgrade it but I will have to start a new thread to learn in more details from people who knows their bikes

Thanks for all your advice