# 34 X 20 Tooth combo versus 32 X 18???



## jtcastillo (Oct 8, 2006)

Is there any noticeable difference between these two setups? Would one be better than the other?

Any suggestions?

Notes:
I currently am running a 26er SS with a 34 X 18 setup


----------



## asphaltdude (Sep 17, 2008)

32/18 = 1.7777777
34/20 = 1.7

So 32/18 gives you a bigger gear.

And bigger ring + cog = less wear.


----------



## gte819s (Aug 13, 2006)

Generally wear decreases and efficiency increases with the larger bend radii.

However I doubt you will notice the difference in wear, efficiency, weight, and gear ratio by adding 2 teeth to a 32/18 on both CR and cog.


----------



## 7daysaweek (May 7, 2008)

I went from a 32/17 to a 34/18... which is an even smaller difference than what you're talking about doing and it was a noticeable change. Flats and downhills (obviously) didn't make much difference but every single tooth makes a difference when you're climbing. I think you'll notice it but overall it'll come out about the same.


----------



## Ptor (Jan 29, 2004)

The reason to go 34 teeth on a crank is so you can use a compact road crank (lowest number of teeth that fit there) -- you can get some strong, light, cheap, and narrow Q-factor cranks that way. I myself use a Ritchey WCS Compact road crank with a 34 tooth chain ring mated to a Shimano XTR Octalink bottom bracket. As far as actual gear inches go, no big deal. As far as efficiency and wear go, I notice differences on how much binding occurs and how much wear develops on smaller cogs on my road bike. So I'm in the "bigger rings and cogs is better" camp...


----------



## dummey (Nov 14, 2008)

PeT said:


> The reason to go 34 teeth on a crank is so you can use a compact road crank (lowest number of teeth that fit there) -- you can get some strong, light, cheap, and narrow Q-factor cranks that way. I myself use a Ritchey WCS Compact road crank with a 34 tooth chain ring mated to a Shimano XTR Octalink bottom bracket. As far as actual gear inches go, no big deal. As far as efficiency and wear go, I notice differences on how much binding occurs and how much wear develops on smaller cogs on my road bike. So I'm in the "bigger rings and cogs is better" camp...


Why would you use a compact road crank, other then weight?


----------



## Ptor (Jan 29, 2004)

dummey said:


> Why would you use a compact road crank, other then weight?


My main reason is narrow Q-factor (also known as "tread"). I've been a serious cyclist since before mountain bikes were a gleam in Joe Breezer's eye, so I cut my teeth on a Q-factor on the order of 135mm on the Campy Nuovo Record Cranks. With a modern road crank, I can have a Q-factor of around 142 mm -- compare that to most MTB cranks that have Q-factors well in excess of 170 mm. Despite getting older and thicker, my hips haven't spread and I like to pedal with my feet closer together rather than like a duck...


----------



## dummey (Nov 14, 2008)

PeT said:


> My main reason is narrow Q-factor (also known as "tread"). I've been a serious cyclist since before mountain bikes were a gleam in Joe Breezer's eye, so I cut my teeth on a Q-factor on the order of 135mm on the Campy Nuovo Record Cranks. With a modern road crank, I can have a Q-factor of around 142 mm -- compare that to most MTB cranks that have Q-factors well in excess of 170 mm. Despite getting older and thicker, my hips haven't spread and I like to pedal with my feet closer together rather than like a duck...


Ahh, never really took notice of the Q-factor before, thanks for the knowledge.


----------



## beewee (Mar 17, 2008)

26er fixed or freewheel- 34-17 "2 to1"
29er freewheel- 32-20
29er fixed- 32-18

IMO


----------



## RogerDoger (Sep 20, 2008)

http://software.bareknucklebrigade.com/rabbit.applet.html

Easiest ratio AND inches chart I've ever found.


----------



## ATBScott (Jun 4, 2006)

A 34 x 19 is very close to the ratio on a 32 x 18. At 1.7894 it is .6% higher than the 32 x 18 gear. As a comparison, it is 5.3% lower than the gear you are using now (34 x 18 = 1.8888). The 34 x 20 is 10% lower than what you use now. If you need more climbing ability, lower is better but on the flats you will pay for it. I've been running 33 x 20 for a couple of years, and it is going to be time to replace my chainring this spring. I'll probably opt for the 34t as I think I can push the extra tooth OK.


----------



## tburger (Apr 27, 2004)

I have one SS running 32/18 and another running 34/20. For me, the 34/20 gives me just enough of a little extra edge to get up (farther, if not over) some pretty tough climbs. So it does make a noticeable difference on the climbs. Flats and downhills, not so much.


----------



## Miker J (Nov 4, 2003)

*"tread"*



PeT said:


> My main reason is narrow Q-factor (also known as "tread"). I've been a serious cyclist since before mountain bikes were a gleam in Joe Breezer's eye, so I cut my teeth on a Q-factor on the order of 135mm on the Campy Nuovo Record Cranks. With a modern road crank, I can have a Q-factor of around 142 mm -- compare that to most MTB cranks that have Q-factors well in excess of 170 mm. Despite getting older and thicker, my hips haven't spread and I like to pedal with my feet closer together rather than like a duck...


Never knew it was also known as "tread".

I must admit I like a narrow Q. It feels better and IMO puts less latter stress on the BB area.

Also, I didn't realize the deal with the 34t fitting on road cranks. Thats good to know. Too bad very few road cranks come in a 180 or 185, though I have a set of Carminas in 18 and like'm a lot.

Thanks for the info.


----------



## dontheclysdale (Mar 12, 2008)

This thread and that calculator above has given me a lot more understanding.... I think I've got the leg strength for a little more gear on the climbs. Here in Houston our climbs are short but in most cases very aggressive (usually around 30-60 degrees for the aggressive ones but no more than 150' long - mostly bayou walls and washouts.) On many I can carry enough speed that it requires very little cranking to get up. On some, they are covered by roots or rooted sections leading up to them so you can't carry enough speed and have to pedal it up. 

With a 34" inseam and a 350ish lb squat I think I have enough power in me legs for those kind of climbs if I switch from 32x19 to 34x19. It doesn't seem like a big difference but I remember how the short climbs got a little easier going from 32x18 to 32x19. It probably helps that my pedal stroke and stamina have gotten a little better since making the change as I've become more acclimated to SS life. Also, I think the higher gear ratio will give me a tad bit more resistance to help me stay in the 90-100 cadence range a little easier. With no resistance my feet start floating all over the pedals and my stroke starts getting sloppy. 

Of course this is all on paper. The real test will be when the new chainring comes next week I can put it on and test this "theory". Thanks for thread and the new gear calc. It has definitely given me some good info.


----------

