Down-sizing the Front chainring
 

I recently bought a 2009 Specialized Langster with 42/16 gearing which seems sufficient for now as I'm using it to lose some weight and recover from some back issues that I had last year. I found myself really liking it as a single speed and some limitations (tire width) and being addicted to the N+1 disease, I've also acquired a Cinelli Tutto with bigger tires (38mm) and bigger gears, 46/16...
So my question is ..Will I find a significant difference with a 46 tooth chain ring over the 42 ?..(the 46 has almost a difference of 10 gear inches) if so, and I downsize to a 42 (or ?), do I shorten the chain ? (like a road bike)...changing the front chain ring seems simpler and cheaper than changing the freewheel to a 18T (I have a Profile Racing Elite ).....All of this seems a lot more complicated than road bikes!..:)
Forgive my newbie-ism, as I'm a long time roadie and we've recently moved to Arizona and my road bikes haven't arrived yet...(I wonder if I'll like on/off road capability of the Tutto over my road bikes?..hmmm)

Time to measure ..
 

Bolt circle diameter Minimums : Track /144 42t , shimano road 130 38t , newer campag 135 39t

110 .. 34t ...

there are outliers , but most are these standards..

If you need a lower gear, a bigger rear cog will also accomplish that, often at lower cost than a new chainring.

Yep, I understand the bolt circle diameters, what I have a 144mm/5 bolt All City so I have choices ...

That's what I thought as well, but I have a Profile Racing Elite freewheel and It appears to me that the cog is an integral piece..and a new one with a 18T 0r 20T is $125 bucks!

The cog is integral to the freewheel, but the freewheel is not likely integral to the hub. Confirm that at a bike shop and order a replacement freewheel. Get the correct freewheel removal tool, too, or have the shop do the freewheel transplant.

Or...could just *try* a 20T Shimano freewheel for $30.00.
If it's the best gear ratio *ever*, you could spring for a new 20T Profile Racing Elite for the win!
Or what trakhack said.

SHIMANO SF-1200 Single Speed Freewheel (20Tx1/8 1 Speed)


https://cimg2.ibsrv.net/gimg/bikefor...523e361b6.jpeg

I have a number of 3/32" 144 pcd Campagnolo chainrings in my horde , to sell , FWiW

Make sure you have the right removal tool before installing the above...;)

Well the real question here then, is why on Gods green earth do you have such an expensive freewheel, and why do you believe you need to replace it with an equally expensive one? That’s nearly $50 more than a standard white industries freewheel, and they are already very expensive.

1 Remove that freewheel
2 sell it
3 use profits to buy several freewheels of normal price and new chainrings
4 enjoy