I have a Cannondale CAAD4 tri frame, 650cc. I got Rotorcranks and installed them today. The front chainring is 63/44.
I just wanted to put the front derailleur back on and it doesn’t fit anymore. The 63 seems to be too large and it hits the derailleur. Since the “vertical” downtube isn’t round (airfoil shape), the front derailleur must be attached with this “front derailleur hanger”. Does anybody know if those “front derailleur hangers” come in extended, larger versions? Did anybody else run into problems when installing large chainrings? How did you solve them?
Actually it would be equivalent to a 58 on a 700C bike. Wouldn’t you agree that it is a huge gear? I was just wondering what the application was. He must be one heck of a strong rider to push that gear.
Kind of the opposite of the compact crank idea that a lot of people are going with.
for the curious ones of you that wonder why I would put a 63 front chainring on: I was sick of loosing time on the downhills. I’m riding 650cc and had a 53/12 on there. So I changed it to a 53/11. This was a little bit better but I still easily spin on slight downhills, especially with a tailwind. I’m not much of a high-cadence rider. You might wonder why I didn’t uprade the front chainring to a 56 or 58. Good point.
I did some calculations for the gear ratio of 53, 56, and 63 chainrings. I wanted to get Rotorcranks and 56 and 63 were the only two bigger front chain rings available.
Gear Ratio of 53 chainring
53/11 = 4.82
53/12 = 4.42
53/13 = 4.08
53/14 = 3.79
53/15 = 3.53
Gear Ratio of 56 chainring
56/11 = 5.09
56/12 = 4.67
56/13 = 4.31
56/14 = 4.00
56/15 = 3.73
Gear Ratio of 63 chainring
63/11 = 5.73
63/12 = 5.25
63/13 = 4.85
63/14 = 4.50
63/15 = 4.20
63/16 = 3.94
63/17 =3.71
63/18 = 3.50
63/19= 3.32
I looked at those ratios and thought that the 63 would be better than the 56. Although the 56/11 would give me a higher gear ratio than my old 53/11, the 56/12 would already be lower. Just enjoy spending some quality time in those gears
I think that the 63 chainring will be better for me. Of course I won’t put the 11 on the back…unless I’m riding down the Matterhorn :). In general I thought that the 63 would give me better gear ratios than the 56.
Some of you might think that it is a waist of energy to go fast during races. I understand that the aerodynamic drag force doesn’t increase in a linear manner (it increases squared). I agree that higher velocities will waist more energy. But I believe that sufficient high gears can be an advantage on rolling courses. Let’s take PCH North of Malibu for example. I always run out of gears on thosre rollers there (on the downhill part that is). If I would have higher gears I would be able to go faster on the downhill portion. Going faster downhill translates into a greater amount of kinetic Energy at the bottom of the hill. Well, this would mean that I would make it further up the hill without pedaling. I’m just taking a guess, but I would think that overall I would use less energy because I wouldn’t spend as much time climbing. Even if I spend slightly more energy, I still think that the overall time will be faster. That’s the reason I got the 63 instead of the 56.
One more thing, the 63 looks really cool. My bike now reminds me of my first tricycle…
Joe Peterson, 2004 California state TT champion and one of our mega 44/63T chainring users writes:
“My bike is custom, the deraileur braze on is high to accomodate my chain
rings, My front deraileur is Shimano. My 63/44 shifts like a champ. Hope that
helps.”
So sounds like you had a valid idea about raising your front derailleur.
What you need is a plate to space the front deraileur up. I have one on a bike of mine,any local machinist could make you one,mine is 3/8 inch wide(slightly wider then the deraileur where it bolt onto the hanger)this piece will need the same radius on the front as the deraileur so it can bolt into the hanger,it will also need the radius in back for the deraileur can bolt on the back of this spacer,you need this spacer to be long enough to be able to bolt the deraileur to the spacer then a second hole lower on the spacer that is threaded to accept the deraileur. So the bolt holding the deraileur to the spacer is above the hanger and this positions the deraileur up.Mine is slightly different than what i have tried to discribe,but will work,if you need a picture let me know and i will see if someone could post it for me.Hope this helps
