Stupid question alert!!

[Sunny Portrush]

I think i already know the answer but I thought i would check anyway and i freely admit that i know diddly-squat about bike mechanics!

Basically, my good bike, an Argon 18 runs Shimano 105 with a rear cassette of 26/12 which makes it a bugger for a 53 yr old to cycle up hill. The front rings are 50/34.

I also have a Cannondale synapse (2014) which runs tiagra gruopset. Its still all the original mech but it’s practically goosed.

Is it actually possible to swap the group set from the Argon onto the Cannondale and then get a new easier to climb cassette for the Argon.

I suspect not as i seem to recall that one of them has a bigger bottom bracket than the other but thought i would ask anyway

Off for a spin now so will catch up later.

 

[bikingdad90]

why don’t you swap out the short cage 105 for a long cage 105, fit a longer chain and bigger cassette?

 

[DCLane]

+1 to the above, although you could fit a 12-28 cassette on the current Argon without changing anything.

A wolf-tooth link would give you the cassette option without having to change the rear mech, but I'd recommend a long cage rear mech.

 

[Slick]

I think i already know the answer but I thought i would check anyway and i freely admit that i know diddly-squat about bike mechanics!

Basically, my good bike, an Argon 18 runs Shimano 105 with a rear cassette of 26/12 which makes it a bugger for a 53 yr old to cycle up hill. The front rings are 50/34.

I also have a Cannondale synapse (2014) which runs tiagra gruopset. Its still all the original mech but it’s practically goosed.

Is it actually possible to swap the group set from the Argon onto the Cannondale and then get a new easier to climb cassette for the Argon.

I suspect not as i seem to recall that one of them has a bigger bottom bracket than the other but thought i would ask anyway

Off for a spin now so will catch up later.

I know very little much like yourself but I did swap my 105 to my cannondale and upgraded the entire group set on m Genesis. it did entail new wheels for the cannondale as it was only a 10 speed if I remember correctly but the original wheels were pretty goosed anyway.

 

[Cycleops]

As per @bikingdad90 suggestion. Doesn’t have to be 105, any that can handle a 34t cassette will do.

 

[Ajax Bay]

my good bike, an Argon 18 runs Shimano 105 with a rear cassette of 26/12 which makes it a bugger for a 53 yr old to cycle up hill. The front rings are 50/34.
I also have a Cannondale synapse (2014) which runs tiagra gruopset.

https://si.shimano.com/pdfs/si/SI-5X90B-003-ENG.pdf
What model number has the 105 RD got - eg RD-5700 SS - you'll find this on the 'underside' of the mech?
Think just fitting a cassette with a larger (than 26t) large sprocket will meet your requirement (for a lower low gear on the Argon 18) as far as possible. Certainly you can run a 28t (7% better gearing). If you did go ahead with a groupset swap, unless the 105 groupset is 10 speed (ie ?7+ years old, I suspect it's 11sp) you'd be swapping the STIs over as well: seems not worth it to me.
Bottom bracket width difference is irrelevant. You could leave the cranks and FD as is.

 

[Sunny Portrush]

Cheers for the replies, I’ll do some more research! The whole drive train on Cannondale hardly works, it takes more effort than it should to turn the pedals by hand. I was hoping i could take the drive train from the Argon and just add it onto the Cannondale (by that i mean the bike shop!)

And all i can see about the 105 mech on the Argon is 11 S 50-34MA

 

[Ajax Bay]

Yes, 11 speed, compact chainset (50-34) on the Argon 18.

The whole drive train on Cannondale hardly works, it takes more effort than it should to turn the pedals by hand

Worth tracking down what the problem is, starting with the BB. Take the chain off. Do the cranks rotate smoothly? If not: new BB required. Spin the rear wheel. Does it stop spinning quickly (brakes opened out)? If so, hub service probably needed.
If neither of those, then what do you mean by 'hardly works'?

 

[Globalti]

I bet you'll get away with an 11-30

 

[Sunny Portrush]

Yes, 11 speed, compact chainset (50-34) on the Argon 18.

Worth tracking down what the problem is, starting with the BB. Take the chain off. Do the cranks rotate smoothly? If not: new BB required. Spin the rear wheel. Does it stop spinning quickly (brakes opened out)? If so, hub service probably needed.
If neither of those, then what do you mean by 'hardly works'?

I mean all the mech on it is the original mech that came with the bike so at least 6 years old and has done probably 15,000 miles - original chain and everything. It has been used a winter bike for the past two years but I always do my best to keep it clean. It got athorough clean when I lasted used it about a couple of months ago but when I took it out of the shed day before yesterday, I noticed that the cranks were not rotating smoothly. Wheels run fine - I just think it`s suffering from old age!

 

[Ajax Bay]

has done probably 15,000 miles - original chain

That's amazing and let's put it down to your cleanliness regime.

 

[Sunny Portrush]

Cheers - I know very little about fixing things so think the best way of keeping things running is to keep them as clean as possible!