Wide range cassette for 'audax' bike

[stork]

I'm thinking of changing my cassette on my 'audax' bike so as to get a wider range of gears.

Currently it's got a 50/34 compact chainset, and a 12-23 8-speed cassette. I'm thinking of going for something more like an 8-speed 11-30/32/34 cassette. However, I'm not quite sure what else I will need and what would be compatible.

My current rear gear system is Shimano Sora 8-speed.

If I go for, say, the Shimano HG40 11-34, I imagine that I might need a new rear mech. But how do I know which one to choose?

Also, I assume that I will probably need a new (and also slightly longer) chain. But the array of chains is bewildering to me -- am I OK just to get any Shimano or SRAM 8-speed chain?

[fatboy]

You will need a new chain and a new rear mech. Beware that the 11-34 8-speed cassette is Mega-range so the bottom jump is huge!

As for rear mech a standard Deore would be a good choice, Acera are a bit cheap and nasty (I've worn two out). Regarding chains you will need a new chain as you'll need to lengthen it, SRAM chains are OK and have the advantage of a powerlink.

[stork]

Thank you, that's helpful. You're right about the ridiculously large jump to the largest sprocket on that model. Shimano's CS-HG50-8I looks a bit more sensible, with the following: 11-13-15-18-21-24-28-32.

Can I use any 8-speed chain?

[fatboy]

The 11-32 is a good set of gears. Any 8-speed chain will work, SRAM, Shimano etc are all interchangeable

[oldroadrunner]

As for rear mech a standard Deore would be a good choice, Acera are a bit cheap and nasty (I've worn two out). Regarding chains you will need a new chain as you'll need to lengthen it, SRAM chains are OK and have the advantage of a powerlink

I'm not sure that you would have to change your chain.I have a 13-34 on my tourer and I regularly remove it after tours and replace it with a 12-25 cassette for normal (panierless) riding with no problems. I have a Deore XL rear mech and 26/36/48 chainrings.

[andrew_s]

Any 8 speed Shimano/SRAM cassette will fit.
If the big sprocket is larger than 30T, you will need a Shimano compatible MTB rear mech.
A 30T large sprocket may or may not work with your existing rear mech - it depends on your frame's gear hanger length.

If your existing chain has been used too much, you'll need a new chain or it will slip on the cassette. Measure 12 inches of chain between rivet centres, and if it measures more than 12 1/8", a new chain is definitely required (you can measure 11 1/2 inches if you've a 12 inch ruler). A new chain is a good idea if it's more than 1/16" past the mark.

If you can use your existing chain, check it's long enough for you to change into the large sprocket when on the 50T chainring when turning the cranks by hand. If you can't, and you inadvertently select that gear when riding (eg at night), you could break your bike. Get a new chain if you don't fancy running the risk.

[fatboy]

If you can use your existing chain, check it's long enough for you to change into the large sprocket when on the 50T chainring when turning the cranks by hand. If you can't, and you inadvertently select that gear when riding (eg at night), you could break your bike. Get a new chain if you don't fancy running the risk.

If the chain is the right length for what you currently have it will be much too short for the new set-up. The above advice is spot on.

[deliquium]

You may find the large jumps between 15 - 18 and 18 - 21 really annoying riding on very steady gradients? Not to mention 11-13 and 13-15 on the flat or riding in a group?

[stork]

Thank you all again. I'm not too worried about larger gaps between gears -- I ride other bikes with 6-speed rear derailleurs across a wide range and they do fine.

Confirmed my thoughts about the chain. Whilst a longer chain might just about do if I swapped back to a smaller cassette, my current chain already pulls the derailleur forward about 45 degrees on the large ring and second-largest sprocket, so not much chance that it could handle another 9 teeth.

[Valbrona]

Is changing to triple too obvious? With compacts, jumps between the gears can be too large, especially with just an 8 speed cassette. As such you can spend a lot of your time on your bike trying to find the right gear.

[Russell160]

If you are changing to Mega Range 34 teeth you will need a long mech, known as Tourney in Shimano Land.

A word of caution, especially as last poster has set the triple hare running:

You can end up spending very large sums of money on these sorts of upgrades £150 easily, (cassette, chain, chainset, bottom bracket, don't mention shifters just yet) and you end up thinking god I could've bought a brand spanker of a new bike with everything sorted for £300 eg see Edinburgh Bicycle Cooperative website.

Look before you leap.

[stork]

Triple's not a good option because of the cost (my front shifters are only compatible with a double). Hence the rear upgrade option, on which I'm hoping to spend no more than about £50. With a bit of shopping around, this should be possible I think (although I might have to pass on the advice to go for the Deore mech rather than the Acera).

[stork]

Thank you all for the comments, I've now completed the changes at just under £40. I went for the 11-32 cassette, which seemed to have the most sensible spacing (the 11-34 has an enormous jump between the largest and second-largest sprockets), Acera mech and SRAM chain.

I've ridden out a couple of times and I'm pleased with the results -- the wider range of gears is nice even though I don't need the lowest few around here on a short ride. The spacing between gears is larger, but that's not really a problem for me at all. I think I'm tending to select slightly lower gears, and it got me thinking about the psychology of choosing gears -- I never liked the thought that I'd already got down to my lowest gear early in a ride, as there was always some comfort in having a gear or two in reserve.

First proper ride was a bit of a let-down though (pun intended). Not only did I get a puncture, I found that my last remaining patch in my repair kit was no good, and that my spare tube had a leak. So the last 2 1/2 miles home were on foot.

[timdownieuk]

I'm thinking of changing my cassette on my 'audax' bike so as to get a wider range of gears.

Currently it's got a 50/34 compact chainset, and a 12-23 8-speed cassette. I'm thinking of going for something more like an 8-speed 11-30/32/34 cassette. However, I'm not quite sure what else I will need and what would be compatible.

My current rear gear system is Shimano Sora 8-speed.

If I go for, say, the Shimano HG40 11-34, I imagine that I might need a new rear mech. But how do I know which one to choose?

Also, I assume that I will probably need a new (and also slightly longer) chain. But the array of chains is bewildering to me -- am I OK just to get any Shimano or SRAM 8-speed chain?

Just resurrecting this old thread as I was considering doing the same with my Shimano Tiagra/Sora set up.

Without knowing in advance whether it would work I fitted an 11-34 8 speed block and it turns out that if you get the chain length just right, it works fine with the Tiagra changer.

[Brucey]

the big-big combination poses one set of problems, but the small chainring- large sprocket one is the one that can cause trouble with the top pulley chattering on the sprocket.

BTW I just set up a bike with an 86BCD chainset, 50-32 chainrings, and a 13-15-17-19-21-24-28-32 cassette. Seems like a really good range of gears for unladen riding, even if there is a huge double-shift in there.

cheers