Gear Ratio Problem

[line71]

Hi
Im seeking advice on a suitable gear ratio set up on my road bike

I presently have 2 bikes,my Giant Defy has a 50/34 & 27/12 set up
I ride in a fairly hilly area and do long rides where the gradient is 5% or more for several miles

I usually ride on the 34-27 rings as i cannot ride comfortably up these inclines with anything harder

My reason for seeking advice is that i have just bought a used bike with a 50/39 & a compact 25/11 cassette
As it is the lowest gear ie;39/25 is just too hard to climb steep or even moderate inclines with but i do enjoy the compact gear ratio on the flat

I would like to know whether i should change my smaller chainring to a 34 and keep the compact 25/11 or to keep the 39 chainring and change the rear compact cassette to include a 27/12 set up

To clarify things,which ratio is easiest on climbs 39/27? or 34/25?
Are the roughly equal?
As i said i like the compact nature of the 25/11 because it changes smoother than the clunkier looser feel on my Giant (27/12)

many thanks for any help

 

[Rickshaw Phil]

The 34/25 will be the easier of those two set ups giving approx 36 gear inches compared to the approx 38 gear inches of the 39/27.

By the way, compact refers to the chainset rather than the cassette. This is when compared to a standard chainset which might be 52/39 or similar.

Edit: If you want to consider a different cassette too, there is quite a choice available. For example: LINK

 

[line71]

Thats great thanks,apologise for the compact description,im not well versed in the tech side yet

Thanks for the link
I noticed during the tougher Giro stages the riders used a 29 rear cassette
would that be Ok with the 39 front chainring? as there are some very steep inclines where i live

Would it be cheaper or just preferable on a technical side to replace the cassette?
I do like the 39 on the flat as opposed to the 34 but a couple more easier gears are a necessity for me

 

[Rob3rt]

I would take a proper double every time. The difference between 34/25 and 39/27 is not really perceptible to me but the double arrangement "feels" better, smoother. Possibly because of the larger number fo teeth engaged with the chain? No idea, but double chainsets feel and look better! The jump between chainrings on a double is nicer too. Dropping to the 34 on a compact is awful!

 

[line71]

Thats really interesting because on my Giant changing from the large chainring to the smaller 34 it really throws it down with a clunk which i dont like
And also the rear gear changes on my Giant on the 27/12 cassette it just feels clunky and loose as opposed to on the other bike (25/11)
I love the gear ratio on my used bike on the flat,its great but i want to take it out on the hills which i just cannot do at present
If i keep the 39 up front i figure i may need a rear 29 or 30 top gear to compensate
I forgot to say,its a 9 speed Tiagra groupset on this bike and 9spd Sora on the Giant

 

[simmi]

Thats really interesting because on my Giant changing from the large chainring to the smaller 34 it really throws it down with a clunk which i dont like
And also the rear gear changes on my Giant on the 27/12 cassette it just feels clunky and loose as opposed to on the other bike (25/11)
I love the gear ratio on my used bike on the flat,its great but i want to take it out on the hills which i just cannot do at present
If i keep the 39 up front i figure i may need a rear 29 or 30 top gear to compensate
I forgot to say,its a 9 speed Tiagra groupset on this bike and 9spd Sora on the Giant

It is a very easy job to change your cassette, the thing to consider is does the rear mech have the clearance for a bigger cassette my ribble came with a 12-25 and I managed to fit a 11-32 cassette this shouldn't have fitted but it did.
I have found this gear calculator very useful.

 

[line71]

Thanks for the advice,im not sure about the rear mech clearance but ive decided to keep my 50/39 and change the cassette
I think a maximum of 29 or 30 rear with the 39 chainring will do as im fairly ok on the hills so that will probably equate to the 34/27 gearing i use