Replace Cassette with Freewheel

[swmmr1928]

I have a road bike with a Shimano Tiagra, 12-25T cassette.  I have a freewheel that should provide higher power on top gears.  How would I go about removing the cassette and hub and installing the freewheel?
What exactly is needed?  Is it possible

Will swapping the cassette for the freewheel result in a significant difference ie attaining higher top speed and/or more difficulty on major gradients?


I found this related thread for the opposite conversion.  

[Painkiller]

Why don't you just replace your cassette with an 11t-30t? you should do your chain at the same time too

[nfmisso]

And rear derailleur - your RD is rated for 28T max in the big cog. A 11-28 cassette MIGHT suit you. If not, change to a Shimano M592 RD, which will handle 11-36T cassettes.

Replacing a cassette with a freewheel is backwards and expensive.  You need a different rear hub (or usually cheaper, whole new wheel).  

What do you mean by "higher power in the top gears" ?

[swmmr1928]

(07-27-2015, 12:35 PM)nfmisso Wrote:  And rear derailleur - your RD is rated for 28T max in the big cog.  A 11-28 cassette MIGHT suit you.  If not, change to a Shimano M592 RD, which will handle 11-36T cassettes.

Replacing a cassette with a freewheel is backwards and expensive.  You need a different rear hub (or usually cheaper, whole new wheel).  

What do you mean by "higher power in the top gears" ?

When I go downhill, my speed is too high to continue pedaling on any gear. To attain high speeds, do I want less teeth and a smaller cog for the highest gear (most powerful)?

It may cost $55 for a new Shimano M592 RD and require me to purchase a new hub and new tools?
That is too much to purchase.

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(07-27-2015, 07:15 AM)painkiller Wrote:  Why don't you just replace your cassette with an 11t-30t? you should do your chain at the same time too

I purchased that freewheel without understand what was required to install it.
Sounds like I can replace the cassette and not touch the freehub.
Can you please help me understand the gear ratio?
What does the first and second number specify (The number of teeth on what and what)?
What does the T specify? If the second number is 36, will I have a very large largest cog on the cassette and very easy gear for hills? Similarly, if the first number goes from 12 to 10, I have a smaller smallest cog for higher top speed?

[nfmisso]

11-28T => 11 tooth small cog for speed, 28 tooth big cog for climbing hills. T = teeth
 
For higher top speed, you want a smaller small cog.

For hill climbing, you want a bigger big cog.

Anytime you replace a cassette, replace the chain.  Longer chain required for 28 vs 25.

[Painkiller]

T is just short for tooth/teeth, Nigel stated that your Derailleur has a 28t max. The small number would be the high gear(11t). and the large number (30t) low gear i.e. better climbing. If you choose to exceed 11t-28t you should replace the derailleur with one that can handle the larger cog capacity.
look at the following chart and play around with it.
http://www.machars.net/bikecalc.htm
put in your info and go to the speed tab and it will show you speed @ cadence, only you know how fast that is