Chainrings size, help!

[Alpinestars]

Hello everybody!
Is there someone that can explain me why some chainrings have more teeth than others?
My outer chainring for instance, have 42T! What do I have to do in order to put a bigger one? To change the chain? And what are the advantages and disadvantages of bigger chainrings?

Thanks a lot guys!

Alberto

 

[jax13]

my take is that bigger chainrings will give you a higher gear.

I would look for a low numbered combination if the bike is destined to be used on hilly terrain or technical bits where you need very low effort gearing. If your using a bike as more of a hybrid then having a higher tooth count will give you a higher therefore potentially quicker speed for a specific cadence (at the cost of slightly higher effort)

 

[Alpinestars]

So, a lower number of teeth is better for mtb, while a higher number is better for road bikes?

 

[stewlewis]

More teeth on the front, less teeth on the back = harder pedaling faster speed due to more rotations of the rear wheel with each turn of the pedals.

Road front chainrings are usually bigger, a lot. Road cassettes smaller with a closer ratio between high and low.

Putting a bigger chainring on the front you may need more link/longer chain, and possibly with bigger sizes a different front mech.

 

[Alpinestars]

Ok mates! Thank you for the infos! But isn't 42t too small?

 

[stewlewis]

Depends on the terrain, on an MTB, no.
If you're on the 42 up front and the smallest at the back and you can't go any faster then yes put on a bigger ring, or move your legs quicker.

 

[Alpinestars]

Thank you! I asked because I found it difficult to find 42t outer chainrings! So I thought maybe it's an unusual size!

 

[feetabix]

42 is an unusual size really.....most (non microdrive!) chainsets ran 24/36/48 rings or there abouts.......you have different ranges between road and offroad to cope with lower average speeds offroad.....if the bike is used on the road and you have reasonable fitness then a 50 or 52 tooth ring will up the gearing a little so you dont spin out the top gear too easily.....changing a ring is simple, just make sure you have enough chain that should you select both largest rings, front and rear, you wont break anything.....

 

[bm0p700f]

Specialites chinook's come in 42T size 104 BCD 4 arm for 8/9 speed.

There is stock of those with the distributor too. Other sizes are availble in 2 teeth increments.

I do not think 42T is too large either.

 

[LesterOfPuppets]

Back in the day when 14T small cogs were the norm, 48T big rings seemed to be most common. Once freehubs with 11-12T small cogs became standard then 44T seemed to become most prevalent, at least on the bikes I've had.

If you want a bigger chainring beware that some frames don't have clearance for the big ones.