11-28 to a 12-30

[migrantwing]

Just watched a handful of videos showing a 5700 and 5800 short cage mech handling a 32t, so it's possible. I don't crosschain anyway, so I won't be using big/big, so all should be OK. I'll pull the trigger on a cassette and new chain tomorrow.

 

[Ajax Bay]

Do you think I could get away with an 11-32t cassette, @Ajax Bay? Plenty of room in my B screw, or do you think a 30t is my limit?

Your RD will work with a 30 but the 32t will be challenging. Even with full use of B screw the issue is the clearance between the top jockey wheel and the bottom of the large sprocket. The diameter of a 28t sprocket is 113mm. The diameter of a 30t is 121mm - basically 2mm additional radius per tooth Measure what you have now and do the sums: is there 8mm spare space there ie to get a 32t in (probably not)?

Think @Smokin Joe has has ridden a 30t successfully and he may have a view on coping with a 32t.

 

[migrantwing]

Your RD will work with a 30 but the 32t will be challenging. Even with full use of B screw the issue is the clearance between the top jockey wheel and the bottom of the large sprocket. The diameter of a 28t sprocket is 113mm. The diameter of a 30t is 121mm - basically 2mm additional radius per tooth Measure what you have now and do the sums: is there 8mm spare space there ie to get a 32t in (probably not)?

Think @Smokin Joe has has ridden a 30t successfully and he may have a view on coping with a 32t.

That's a great explanation and description, @Ajax Bay. What I'll do later is have a tinker with the B screw and see what the maximum clearance from the jockey wheel to my 28t is, and then see what space is available between the two. This will hopefully determine if I'll max out at a 30t or 32t.

@Smokin Joe, where are ya?

 

[migrantwing]

New problem: I can't get the rear shifter to drop down the cassette now. It is stuck in the 28t. Trust my luck.

 

[Smokin Joe]

That's a great explanation and description, @Ajax Bay. What I'll do later is have a tinker with the B screw and see what the maximum clearance from the jockey wheel to my 28t is, and then see what space is available between the two. This will hopefully determine if I'll max out at a 30t or 32t.

@Smokin Joe, where are ya?

Here, my love

30t is no problem. Use this http://www.machinehead-software.co.uk/bike/chain_length/chainlengthcalc.html to sort the correct chain length. If necessary adjust the B tension screw to give correct clearance.

 

[migrantwing]

Here, my love

30t is no problem. Use this http://www.machinehead-software.co.uk/bike/chain_length/chainlengthcalc.html to sort the correct chain length. If necessary adjust the B tension screw to give correct clearance.

Oh, there you are, darling!

Excellent! Thanks for the link/advice.

I've shifted too far over with the chain off and now that little pip on the RD cable that sits in the shifter has moved. All my tools (including Allen keys) are at my mate's house as I'm doing some work there, so I can't even undo the bluddy RD bolt to get the cable out. FML!

**Update: Managed to find an IKEA multitool thing with Allen keys on, got the cable out, so all good. Only downside is that I don't have my cable cutters to trim the new cable.

 

[migrantwing]

@Ajax Bay and @Smokin Joe

Decided to have a look at my bike and take some pics. Click on pics and then right click > view image. The image will be in its original, large size to show what clearance I have with the B screw turned about 3/4 of the way in.

I wonder if reversing the B screw to go from the opposite side would make the gap larger?

The gap between the 28t and the upper jockey wheel is roughly 9.53mm (as shown in photo)

 

[e-rider]

12-30 is a better ratio than 11-28 or 11-32 IMO - I wish Shimano made 12-30T as standard across their range

 

[migrantwing]

12-30 is a better ratio than 11-28 or 11-32 IMO - I wish Shimano made 12-30T as standard across their range

Agreed. I'd like a 12-30 or 12-32. I never, ever use the 11t, I just coast.

 

[Ajax Bay]

I've given you the approximate formula. I think you'd get interference with a 32t but others on here may say they've tried it and it worked (I haven't tried it; a 30 is enough for my riding). Why not see how much more the distance is with the B screw right in?

 

[migrantwing]

I've given you the approximate formula. I think you'd get interference with a 32t but others on here may say they've tried it and it worked (I haven't tried it; a 30 is enough for my riding). Why not see how much more the distance is with the B screw right in?

The B screw is as far as it will go. It's hitting the ledge on the mech hanger and won't turn any more. I may try and put the B screw in from underneath and see how it goes.

Thanks for your formula and help, @Ajax Bay. Appreciate it!

 

[kiriyama]

Could you fit a triple chaining to the front? Would get much lower gears with a granny ring.

 

[TheDoctor]

Also needs new STIs, chainset, front mech...
Going crazy big on the cassette will just need an MTB mech in extremis.

 

[migrantwing]

All out of 32t cassettes. I was going to pull the trigger on one today. Will have to wait til the end of the month to get one for a good price when stock is back in.

Thanks for all the help/advice, folks. Ya gotta love CC

 

[sidevalve]

Just make up a cassette to suit you - it's no big deal. Get anything with a 30 tooth and fit the sprocket to whatever you want - easy.
PS have just done it on the old Dawes from 28 - 30 and yes it makes a lot of difference.