Shimano Sora Flight Deck … help adding granny gear.

AberdeenAngus

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Wonder if anyone can help?
I have a Dawes Audax Sport with Shimano Sora gears and Flight Deck indexed shifters.
Currently 2 x 8, but I would like to add a granny gear.
Can I just change the chainset and front derailleur for triples, or do I have to change the rear derailleur also.
If I can just change the front, do I need to change the shifter too?
I don’t know if there’s a limit on the travel or if the double/triple shifters are the same.

As you can tell, complete novice to derailleur gears.
 
Wonder if anyone can help?
I have a Dawes Audax Sport with Shimano Sora gears and Flight Deck indexed shifters.
Currently 2 x 8, but I would like to add a granny gear.
Can I just change the chainset and front derailleur for triples, or do I have to change the rear derailleur also.
If I can just change the front, do I need to change the shifter too?
I don’t know if there’s a limit on the travel or if the double/triple shifters are the same.

As you can tell, complete novice to derailleur gears.
Probably worth going to see a good bike shop, eg one that fixes bikes not just selling. Sometimes a triple on the front requires a longer axle through the bottom bracket. It is usual to have a triple front shifter, however you can trim 2 speed ones which may work.

Lastly turning to the rear derailleur Im not sure if your current set up will handle the “slack” when you drop onto the granny ring.

So probably havnt helped here other than saying visit a bike shop.

Just as an aside if you are running 8 speed your biggest ring on the back maybe 27 or 29. You can get 32/34 rear sprockets that would give you virtually a 1:1 ratio without a triple on the front.

Current wisdom is to reduce front chainrings eg 1 X so again that maybe an option.
 
Thanks Steve. I suspected a trip to the bike shop would be the best bet. We have a good one here so I’ll pop in and see him.
Not sold on the drops anyway as I prefer a more upright position, so might just save the hassle and see if he’ll take a trade in.
 
I would guess that the shifter would need to be changed to a triple, unless it already had triple indicators on it as one of my previous twin ring bikes did.

The number of gears on the back isn't an issue for a front triple setup.

Thinking about it, I did this back when I first started cycling. I needed a longer caged front mech, new triple shifter, and a longer armed rear derailleur to allow the excess chain to be folded back on itself when running the shorter gear paths. Also, avoid using the smallest rear cog with the smallest front ring and vice versa as it'll be trying to twist the chain sideways a fair bit.

That bike put me in hospital, I paid to have it rebuilt and modified some more, but never felt 'right' on it after the accident.
 
I would keep the original set up but possibly change the rear cassette for a wider set of ratios. Obviously this depends on what the Sora mech will take. This would be the simplest and cheapest way to give you some lower gears for climbs. Very rare for people to use the largest rear cog and the smallest ring on a triple front as your feet are going like mad and you are getting nowhere.
I would take advice from the LBS. You would need a new front changer, new chainset, possibly a new bottom bracket and possibly a new front mech and cable.
 
Spoke to bike shop today.
Very enthusiastic and knowledgeable young guy who was a pleasure to deal with.
Going for an 11-34 cassette. Guy in the shop thinks I might get away with my existing derailleur but we’ll see.

When you are used to buying parts for motorbikes it’s a pleasant surprise how reasonable parts are for push bikes.
 
Spoke to bike shop today.
Very enthusiastic and knowledgeable young guy who was a pleasure to deal with.
Going for an 11-34 cassette. Guy in the shop thinks I might get away with my existing derailleur but we’ll see.

When you are used to buying parts for motorbikes it’s a pleasant surprise how reasonable parts are for push bikes.

Excellent result, now where are those hills !
 
Sounds like you are sorted. If you do find the rear derailleur can't manage the large low gear on the new cassette, which I doubt will be the case, instead of a new derailleur with longer arm consider a smaller front chain ring which will give you some chain back and lower the gearing even further.

2 speed changers with three front rings is a no go.
 
And.... if you fit the new cassette with the larger diameter low gear and hear a grating noise, don't panic.

There is something called a B screw which alters the angle of the top arm of the derailleur to the frame. The top arm is responsible for shifting sideways and pulling the chain into another gear, the bottom arm is just a chain tensioner.


Anyway a larger diameter gear on the rear may result in the top jockey wheel grating on the chain. It's easy enough to adjust if you google derailleur B screw.
 
And.... if you fit the new cassette…/QUOTE]

Thanks for that.
I was tempted to just give the bike to the shop but I enjoy the learning curve so I’m keen to do this myself.

Excellent! You may then benefit from 2 new tools - an adaptor to undo the existing cassette and a chain whip which stops the cassette spinning as you're undoing it.
 
11-34 cassette bought and fitted. Just fettling the new chain and seeing if I can get away with the existing derailleur. It’s looking close.
 
You can change the derailleur cage if that’s the problem. I had to do that when I changed from an 11-28 to 11-32. Finding the parts was a bit of of a challenge but it was cheaper than changing the entire derailleur.
 


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