Cassettes

[graham jw]

I have a specialised allez 16.

It has a shimano 2300 group set. The cassette is 12-25 8sp. When attempting to climb 14% hills I generally have to push! Anything less than14% is just about manageable. It is a double with a the small ring being 39t.

Can I get an 8sp cassette with a 27t sprocket? And will there be much of a difference between the 2. Would it be a straight forward swap? I understand it is advisable to get a new chain also. What size do I need and can you recommend any brands.

I'm a bit new to all this!

Thanks.

 

[rusty bearing]

Getting 8 speed can be a bit like hard work but Chain reaction have a Shimano 11-28 and an 11-30 (shimano hg70). Problem will be whether your rear mech will cope with it. You would need a long cage version which you may not have on given the current ratios.
Chains; SRAM or Whipperman?

 

[HLaB]

I have a specialised allez 16.

It has a shimano 2300 group set. The cassette is 12-25 8sp. When attempting to climb 14% hills I generally have to push! Anything less than14% is just about manageable. It is a double with a the small ring being 39t.

Can I get an 8sp cassette with a 27t sprocket? And will there be much of a difference between the 2. Would it be a straight forward swap? I understand it is advisable to get a new chain also. What size do I need and can you recommend any brands.

I'm a bit new to all this!

Thanks.

Yes, you can fit a 27t but you might need to search around a bit before you find an 8sp in that range, that's probably the cheapest way to do it and it will lower your gears a fair bit. Alternatively you can put a bigger cassette on to get an even lower gear but that would need a new derailleur cage at least or you can change your chainrings from a traditional double to a compact double but this is also more cost. The other and cheaper way is practice, at 14% you are already more than half way there for most hills ;-)

Chainwise you are right when you put a new cassette on you are best to fit a new chain, you just need to order any 8sp chain; it'll come to long so you just have to make the same number of links as your old chain and remove the excess. I like SRAM 8sp chains because of their quick link which makes fitting faster and easier but that is only my preference any brand will do :-)

Edit Rusty has said similar in a lot less faff ;-)

 

[Andy_R]

Chainwise you are right when you put a new cassette on you are best to fit a new chain, you just need to order any 8sp chain; it'll come to long so you just have to make the same number of links as your old chain and remove the excess. I like SRAM 8sp chains because of their quick link which makes fitting faster and easier but that is only my preference any brand will do :-)

Edit Rusty has said similar in a lot less faff ;-)

That's true if you are using the same size large sprocket on the cassette. If you are putting on a lower geared cassette then you'll need a longer chain (big ring to big ring)

 

[RecordAceFromNew]

If your chainset is the same as the current Allez 16 then it would be a 52/39. That combined with the 2300 rear mech's spec you have an official wrap range available at the back of 35-(52-39), which is 22.

What that means, is assuming there is enough clearance between the mech's upper jockey wheel and the cassette, the widest range cassette you can theoretically have is 11T to (11+22) or 33T.

However the 2300 rear mech's official maximum sprocket size is 26T - but that figure is nearly always a pessimistic guide, while in reality it is dependent on frame/mech hanger geometry as well as the rear mech's parallelogram dimension - fortunately you can find out what the largest rear cog your existing set up can* handle by just a ruler - the number of teeth you can add to the 25 currently is the clearance between the 25 and the upper jocket wheel (when the chain is on the 25) in mm divided by 2. If e.g. the distance is 10mm then the largest rear cog your system can handle is 30T, but 29T will probably be best to allow for measurement error and a bit of wriggle room for the chain etc.

8 speed Shimano compatible cassettes are widely available - since you can pick any Shimano or Sram 8 speed cassette, whether "for" mtb or road. In fact since you are looking for low gears, Shimano or Sram mtb cassettes will offer a wider choice, e.g. all Shimano and Sram 8 speed cassettes on this page within the right tooth range are eligible.

Unless close ratio is important to you, if I were you I would pick one that starts from 11T (since wrap capacity is not going to be the limiting factor for the rear mech, and it will help speeding you downhill), and go up to near the maximum sprocket size limit by measurement as described above - that will give you the biggest range for the biggest hill most economically.

Regarding chain, if the existing chain is optimal in length then for every 4T increase in max rear cog size you should increase the new chain's length by 2 links above the existing. But if I were you I would not assume the existing length is right and just work out the optimal new length using a chain length calculator.

* if you wish the clearance can be maximised, allowing a bigger cog, by adjusting the mech's B screw.

Hope it helps.

 

[rockyraccoon]

I have a specialised allez 16.

It has a shimano 2300 group set. The cassette is 12-25 8sp. ...

My Allez 2010 came with a 13-26 cassette. It's been advertised everywhere as a double front (52-39) and 8sp 12-25.

I was wondering whether people got the same or not!?

Anyway, I found it was easier to replace the front crankset for a compact (50-34) instead of replacing the cassette, rear mech and chain. It has helped a lot ..

 

[HLaB]

That's true if you are using the same size large sprocket on the cassette. If you are putting on a lower geared cassette then you'll need a longer chain (big ring to big ring)

Not always for two teeth, I was advised when I changed my cassette on my old bike from a 34 to a 32 not to change the chain length and it didn't have a bad effect; when I changed it again to a 30, I did do the wrapping round the big/ big thing (not threaded through the derailleurs and allowing for a 2 link overlap. I guess that was up gears, I've never lowered them it might be more crucial that way.

 

[graham jw]

In response to rockyraccoon, I've just got home and checked my cassette, it's the same as yours 13-26t! As allez are advertised as having an 11-25t cassette!

Blimey, I'm more unfit than I thought I was!

Could you tell me how easy/cost of changing to a compact set up?

Thanks for everyone's information so far.

 

[rockyraccoon]

Could you tell me how easy/cost of changing to a compact set up?

Very easy! I got the compact (50/34) crankset (same groupset 2300). You can get it for around £30 from parker int. You'll also need a crank extractor (around £5).


The bottom bracket on my Allez is square taper crank type therefore the crankset has to be the same type (check that). In my case no need to shorten the chain. I just had to lower the front derailleur because the chainring is smaller. That's pretty much it.

 

[graham jw]

Thanks everyone so far.

I understand I will need some special tools. A lock ring spanner and a chain whip. Is there anything else I will need?

With regards to the lock ring tool, are they specific to certain manufacturers? Eg, if I'm swapping from a shimano cassette to SRAM will I need 2 lock ring tools?

Thanks once again.

 

[HLaB]

Thanks everyone so far.

I understand I will need some special tools. A lock ring spanner and a chain whip. Is there anything else I will need?

With regards to the lock ring tool, are they specific to certain manufacturers? Eg, if I'm swapping from a shimano cassette to SRAM will I need 2 lock ring tools?

Thanks once again.

You'll need a chain tool only to adjust the new chain length if you are using a quick link and to close if not.

One lockring will suffice I've changed quite a few cassettes from Shimano to Sram because I prefer the range they offer. Campy Lock rings are where it differs and I believe they also differ between size (11t and 12t) but that doesn't affect you :-)

 

[Chrisbpr]

Very easy! I got the compact (50/34) crankset (same groupset 2300). You can get it for around £30 from parker int. You'll also need a crank extractor (around £5).


The bottom bracket on my Allez is square taper crank type therefore the crankset has to be the same type (check that). In my case no need to shorten the chain. I just had to lower the front derailleur because the chainring is smaller. That's pretty much it.

Did you have to get a new bottom bracket as well as I think it 113 on my allez and parkers told me I would need a110mm?

 

[youngoldbloke]

Compact chainset looks like an easy option - you are going to lose your highest gear of course, and you may well need to adjust the position of the front mech. Otherwise - I have just fitted a 12-32 cassette to my old Peugeot 525 road bike. (48/38 at the front). It has an Exage 500 (?) shortcage rear mech. I wasn't expecting it to work, (long cage needed etc, etc) but it is smooth as silk. No adjustment needed, clearance fine. I haven't even had to adjust chain length (was running 28T bottom) - Chain length calc (Google it) was predicting less than 1 link extra only, and it runs fine.