# Max # of teeth on front chain ring?



## links0311 (Aug 20, 2004)

Is 53 the highest out there? I saw in the latest Bicycling magizine a track bike from the 
40s that looked like it had about 70! (pg. 77). Can you find bigger than 53 chain rings out there and if so, where? Thanks.

-Links


----------



## estone2 (Sep 25, 2005)

links0311 said:


> Is 53 the highest out there? I saw in the latest Bicycling magizine a track bike from the
> 40s that looked like it had about 70! (pg. 77). Can you find bigger than 53 chain rings out there and if so, where? Thanks.
> 
> -Links


http://www.amazon.com/FSA-TT-Aero-Road-Chainring/dp/B000MUP8P0

That's the most common.

The massive ones that are 60 or 70 are on track bikes, they're used for motorpacing behind a car or motorcycle at really high speeds.

-estone2


----------



## wim (Feb 28, 2005)

T.A. makes a 61T ring, but only for a 110 bolt circle diameter ("compact") crank. Harris can get T.A. chainrings, but it might take a while.

http://sheldonbrown.com/harris/chainrings/110.html


----------



## links0311 (Aug 20, 2004)

61 is perfect, that'll make a man out of me for sure. With the 17T track cog I have on my wheel right now, that's almost 100 inches! I'm in luck, I already have a set of 110 cranks on the bike. The price is a little steep though. Maybe I can find them for less than 74 dollars somewhere. Thanks for the post.

-Links


----------



## wim (Feb 28, 2005)

Before you buy, make sure a 61T will clear your chainstay. You can get a rough idea of overall chainring diameter in mm with this formula: tooth count _multiplied by _13.2 _divided by _3.14.

If you need more chainstay clearance, you could move the ring away from the frame, but that could screw up your chainline. Or do what we used to do back in the day when a bike was just a piece of outdoor equipment: put a dimple in the chainstay with a hammer. The other alternative for 100" is a 52 x 14 or a 48 x 13, but I'm sure you know that


----------



## links0311 (Aug 20, 2004)

I would have never thought about chain stay clearance. If your calculations are right, a 61T chain ring would have a diameter of 10", that's the size of a frisbee. I will have to take a closer look at my bike before I move forward. Thanks for the reply.

-Links


----------



## Lectron (May 29, 2005)

You do the counting......


----------



## JCavilia (Sep 12, 2005)

*Riiiiight*



links0311 said:


> 61 is perfect, that'll make a man out of me for sure.


A man who hobbles around on bad knees. I can't imagine why you'd want to do this. I also note (as two other posters have in both threads) that you can get the same gear cheaper and without the goofy giant ring by just getting a smaller cog. 

But I suppose if you REALLY like the way it looks . . . . . . . . . . .


----------



## Einstruzende (Jun 1, 2004)

Lectron said:


> You do the counting......


You're going to tell me the fork is backwards because of aerodynamic considerations, right?


----------



## wim (Feb 28, 2005)

> _You're going to tell me the fork is backwards because of aerodynamic considerations, right?_


That's correct. The purpose of the reverse fork, the small front wheel and the steep head tube angle is to get the stayer as close to the pacer as possible to get maximum draft. There is also a positive side effect of a reverse fork: it increases trail, which would otherwise be very small due to the steep head angle and the small front wheel. Some say that the reverse fork also absorbs shock well when you hit the roller hard (which you will do several times during a stayer race), but I'm not sure if that holds up to scrutiny.


----------



## JCavilia (Sep 12, 2005)

*Very interesting, Wim*

I've never seen the term "stayer" before. This is the same thing that's also called a derny race, right (the funny motorbike is the derny)?

I didn't actually count the teeth on the picture Lectron posted, but I'm estimating around 100.

Here's a more compact way to get huge gear ratios








The double reduction gear has a 70-tooth ring driving a 13 tooth cog, which turns a 60 driving a 15. With the 18-inch wheels that's about a 450-inch gear. Fred Rompelberg set the motorpace record of about 167 mph on this bike.


----------



## wim (Feb 28, 2005)

The terminology is confusing, and there's also a difference between British, U.S. and continental European word usage. The UCI only uses the term "motorbike" and "moped." I and many others use the word "stayer" to mean racing behind big motorbikes, but that doesn't mean it's the correct term everywhere. 

In very general terms, the racers that are paced by big motorbikes (500 -1000cc engines) reach speeds of up to 50 mph. The limit is the banking of the track. (At full speeds, the rear wheel of a stayer's bicycle sometimes starts to slip *up* the banking.) These races were big where I grew up, mostly because of the wild and woolly goings-on in the infield: beer, bands, partying, cigarette smoke as thick as a forest fire—all overlaid by the thunder of 1000cc bikes without mufflers. NASCAR without the cars  

Other races are done behind a much smaller and slower motor bike, like a moped. Some call such a moped a "derny." The idea is for the moped to afford no more aerodynamic shelter than a bicycle rider.

If you're interested, here are the gory details. Chapter II has the rules, Chapter VI the specs for the motorbike and the moped.

http://www.uci.ch/english/about/rules_2004/ch03.pdf


----------

