HG50 11-25 swapped for 12-32

[sayek1]

Guys,

Thanks for all of your help. I looked last night at the article kindly linked to - doesn't look like the 105 has a "B" screw and plenty of tampering didn't make things any better - I can't see any way how I can keep i clear of the 32t sprocket so this looks like a dead end. This weekend I will try to canabalise an old MTB derailleur and see how this works. Failing that CRC look like they will have another purchase.

I need to sort it this weekend as it looks like spring is here in Scotland and my daily commute needs to start again.

Thanks for your help.

K

 

[sayek1]

Watch out for "rapid rise" or "low normal" MTB rear mechs, which exist as an alternative to the traditional top normal mechs.
These work the opposite way round to road mechs, so the main lever would shift to a higher gear/smaller sprocket, and the inner lever to a lower gear/larger sprocket. This would be confusing.
Low normal mechs can be spotted because the cable clamp is on the inner parallelogram plate rather then the outer one.

Well, tried fitting an old Deore MTB Derailleur yesterday and it didn't work too well - put on a longer chain from the bike the derailleur came off, but there was lots of clanking rubbing and chain suck. At this point I want to avoid spending too much on new bits and specialist help, so today I will try and use an old Shimano 12-28t cassette I have just swapped off my other bike (for an Apex 12-32 which works brilliantly by the way) and go back to the 105 derailleur. I will use the old SRAM chain which I am assuming will work OK with the shimano mech etc.

The bike is going to get used on a long (600m) ride around Scotland in June and I was hoping for as much help on the hills as possible, but if I have to make do with 28t rather than 32t then this will have to do. Plan B would be to sell it and get the new Boardman CX which looks very nice, but cant afford to do this.


To top off my poor Saturday I was out on a 55miler and had a major rear blow-out at 45miles. So bad I couldn't fix it and had to call the wife out for a pick-up. Not too popular.........

 

[Sittingduck]

I think you are going to have problems if you are trying this with old chains. Are the chains the correct speed (width) for the new custom setup? If the chain is old and worn and the cassette is new, you're going to have problems there too.

Good luck though Interesting thread this is.

SD

 

[PatrickPending]

Guys,

Thanks for all of your help. I looked last night at the article kindly linked to - doesn't look like the 105 has a "B" screw and plenty of tampering didn't make things any better - I can't see any way how I can keep i clear of the 32t sprocket so this looks like a dead end. This weekend I will try to <snip>

I believe they do - fitted 2 rear mechs this year alone and had to play with the b-screw

see

http://techdocs.shimano.com/media/t...00-5501/SI-5TK0D-En_v1_m56577569830603908.pdf

'How to use the b-tension adjustment screw'

Mind you its probably a case for a long cage rear mech anyway, if it were me I'd try the longer chain and b-screw adjustment before major surgery.


see also here for setting up:-

http://bicycletutor.com/adjust-rear-derailleur/

 

[sayek1]

Well I got it to work. The SRAM cassette is spinning along nicely on the 105 derailleur. I think I'll just have to suffer a bit on the highland roads as I can't be bothered (or afford) all of the hassle of getting a 32t cassette to work.

I think this highlights the good aspects of the SRAM Apex system where they have a 32t cassette available which I have found to be excellent out on the road.

Thanks to everyone for the advice - I have learnt lots and can now do a number of things I'd previously have needed to go to a shop for.

Regards
K

 

[Banjo]

Just to clarify, which bits have you got on there now ?

Took my bike into the shop that I got it from the mechanic in there had no hesitation in saying I can change my 25 tooth cassette for a 28 which will be enough for me 99.9% of the time. (105 groupset)

Got off and walked on the steepest bit of Gospel Pass rd going South yesterday but pretended i had stopped to take photos of the other cyclists spinning up behind me with there larger cassettes no doubt

 

[potsy]

I have recently (yesterday) gone the alternative route and put a slightly smaller front ring on, was concerned about what I could get away with cassette wise, so this seemed an easier option, £7 for a steel inner ring.

 

[Banjo]

What size ring did you change from and too Potsy?

 

[potsy]

What size ring did you change from and too Potsy?

I just went from 30 to 28, I also put a 12-26 on the back instead of the 12-25 it had, as it needed a cassette change anyway.
Has given me enough to get up most of the stuff I need to, any more and it'd be quicker to walk anyway

 

[frank9755]

I think you are going to have problems if you are trying this with old chains. Are the chains the correct speed (width) for the new custom setup? If the chain is old and worn and the cassette is new, you're going to have problems there too.
SD

+1
That's the most obvious explanation for it not working.
Even if it had worked acceptably, the old chain would have worn your new cassette more quickly so not getting a new chain wouldn't be cheaper in the longer run!

 

[sayek1]

Just to clarify, which bits have you got on there now ?

Took my bike into the shop that I got it from the mechanic in there had no hesitation in saying I can change my 25 tooth cassette for a 28 which will be enough for me 99.9% of the time. (105 groupset)

Got off and walked on the steepest bit of Gospel Pass rd going South yesterday but pretended i had stopped to take photos of the other cyclists spinning up behind me with there larger cassettes no doubt

I've got the standard 105 derailleur with an SRAM 11-27t cassette and an SRAM chain (both SRAM bits came from a RIVAL groupset on my Verenti bike which I swapped out for a APEX 32t cassette and long arm derailleur).

I think I should be OK on the 11-27 - I used it last year on about 4 x 100mile sportives I took part in including the Trossachs Ton & Ken Laidlaw, both of which have some very steep hills on them. Whilst I swapped out the 11-27 on the Verenti to make it easier this year on the sportives the trip in the summer on my CDF will have to just be a bit tougher now on the hills.

I will try a few hills with it and see how it goes - failing that it will need to be a bike-shop-job as I dont want to keep buying, trying and testing parts myself - I may as well just tell the shop what I want and pay a bit more to get it right first time.

However, I have learnt a few things which I am sure will save me a lot of money in the future.

 

[PpPete]

As mentioned up thread, although road mechs like the 105 are only rated up to 27T or 28T ... you can push them a bit. As you've found, 32T is too far. 30T works great for me. Being an utter wuss and over weight, + with crap legs the regular triple chainset and a 30T sprocket isnt quite low enough, so I changed my chainrings for 50-38-26 , again beyond the rated capacity of the mechs, but it's oK if you get the chain length just right. I can get up a 20% now while staying the saddle. 25% out of the saddle is do-able too, but only for short periods - like I said crap legs.

Why didnt I go for a Deore mech? Well I'm vain as well as all my other faults. It just had to be a road mech.

 

[RecordAceFromNew]

The 105 must be taking up quite a range there Pete! What size is the smallest cassette sprocket?

 

[frank9755]

I've got the standard 105 derailleur with an SRAM 11-27t cassette and an SRAM chain (both SRAM bits came from a RIVAL groupset on my Verenti bike which I swapped out for a APEX 32t cassette and long arm derailleur).

I think this is the set-up that is working ok, but SRAM cassettes don't normally index properly with Shimano shifters - different spacing between the sprockets. However if it is working, then practice is more important than theory!

 

[frank9755]

I changed my chainrings for 50-38-26 , again beyond the rated capacity of the mechs, but it's oK if you get the chain length just right.

I've got 50 / 26 with a 105 front mech too, Pete (39 middle ring). Plenty of clearance. Just means I can't do the extreme cross-chain gear, which I never would attempt anyway.