Campy ct UT BCD question
 

I read a few days ago that the campy compact cranksets have a weird 110 BCD? Looks like one of the arms is a little bit longer ???

Im asking because i need a set of campy cranks with a 48 T chainring and looks like all i could get is a 50T crankset. I saw FSA makes a 48T chainring for 110 bcd. My quesion is if its posible to put that 48T chainring in the campy crank???

How much is the difference in that longer arm so using a dremmel to move the hole IN THE CHAINRING and compensate the longer arm in the crank spider?? The difference it is too much?

THanks.

Which model UT crank do you have?

I think the strange BCD extends only through the Record, Chorus and maybe Centaur CT cranks. To test this, I put a generic (RPM) 50t 110 bcd ring on my Veloce UT cranks. The pictorial evidence is here
http://lh5.ggpht.com/jberkompas/RyUV...4/IMG_1419.jpg

Even if you have a Record or Chorus CT crank, I believe the off-set bolt is only about 2 mm out of line. I've heard of guys elongating one hole in an aftermarket chainring with a file or a Dremel to make it fit. Just be sure you keep the ramps and pins lined up properly to keep the shifting performance good. For an outer ring, the chain drop pin has to be in the right place so it's pretty obvious which hole to modify.

BTW, this seems to be a lot of work to substitute a 48T for a 50T ring. What is the need?

HI thanks for the answers. I bought a Scott SUB 20 time ago for cheap, like 200 bucks less than the official market price. I want that bike to go out with the kids.

Since all the shimano stuff that model has is not acceptable under my standards I decided to move the frame to the next level with some stuff i had at home moving around... These are the mods so far.

Fork swaped for a carbon fork with disc adapter incorporated.
Wheels swaped with a set of Cane creek strados disc and Vittoria tires.
Avid bb7 disc brakes
Campy veloce 10sp flat bar brifters
Campy chorus FB CT FD.
Token FD handlebar
Campy Chorus Crankset 50/39 <-- this is a problem so it needs to be changed for a compact one.

The main problem with my project is that the seat tube in the SUB 20 is not all the way rounded, it is rounded probably for 10 inches then it changes its shape to oval and the diameter gets wider. With a 50T chainring the FD its located just where the tube starts to get oval so it cant be fixed right, it tends to move down no matter what i do. (electrical tape, ect) I even built sort of an adapter to fit the FD a little bit upper in the FD clamp, it sort of worked out but i'm still to high and it tends to moves down anyways.

A 48 will fix the problem, even a 46 might do even better. Wonder how hard it is to put a FRONT DERAILEUR BOSS RIVIT ON STYLE, anybody knows? instead of rivets I can bolt it on. Well those are my problems, and thatswhy I was asking about that 48T chainring.

Thanks.

I believe the Campy Centaur cranks have the standard (not weird) 110 mm bcd so any aftermarket chain ring will fit without the need to modify the bolt circle. So, if Centaur isn't too down-scale :) you might see if it will work as received. A Veloce crank certainly will as pictured above. TA and Suguino both make 48 and 46T chainrings in 110 mm bcd and Harris Cyclery carries both brands.

You currently have a STD crank with 53/39. The CT chainrings will not fit on this crankset as they have a vastly different BCD.

I suggest you sell your existing STD crankset and buy a new CT crank outright. You'll probably be even, or perhaps ahead, and there will be no need to modify anything now, or in the future.

The OP says he has a standard 135 mm bcd Chorus crank with, he claims, 50/39 rings and the 39 isn't small enough for his needs.

He wants a Campy CT crank to provide the smaller inner chainring but wants it with a 48T big ring. The problem is Campy CT cranks (down through and including Centaur as I've discovered) have a proprietary variation on the "standard" 110 mm bcd so an aftermarket 48T ring like a TA or Suguino won't fit without some surgery.

Any suggestions?

Thanks guys... I found all what i need... actually there is a guy at ebay that is selling a set of chorus carbon (no ut) crankset in 48/36... it is too expensive for me, sadly :)

I found some stuff at univ. cycles and in pro cycle kit or what ever the name is. The funniest thing is that it will be chaper to buy at UK than in oregon, and probably i'll get the stuff before also. I read that pbk is quite fast and living in the east coast probably it will help a little bit.

Anybody have ideas for cable stops besides using plastic straps??? The routing of all the cables is changed.

UM

The point about the chain drop pin made above is a good one. You'll notice in the picture I posted above that the pin sits offset due to the Campy hidden fifth arm crank design. If this is important (and it might be, for ramp/pin placement and thus shifting performance,though you could rotate the inner ring to match), then nothing but a ring made for the hidden fifth design would work.

2007/ 2008 Chorus UT CT cranksets are offered with the following chainring combinations: 34-48, 34-50 and 36-50.

I'm not sure how the OP has a 39-50 as the STD are only offered as 39-52 or 39-53.

Something is not correct.

The good news is the OP has the FB CT Fr Der. This will help.

I don't know where the 50/39 chainring set came from either but that's what he said.

Interesting that the CT does come in 48/34 as that would solve his problem directly.

HI again... i changed the 53 with a FSA 50T i bought long time ago. That sort of worked out but it is still too big, besides the FD doesnt like the 50/42 combination because i have a CT FD as bob remarks.

Yes it is cool it comes in that combination but looks like nobody have them in stock. There is a guy selling a carbon Chorus set squared tapper at ebay but I cant afford it, it is too much money for me. I even have the bb that fit that crankset already installed in the bike... Damm it! :)
Well a city bike with carbon cranks... that should be cool right? :)

Have you thought about Centaur? Or Veloce? This would be a lot less expensive and you can get exactly what you want. Performance wise you're really only adding some weight. It's a flat bar city bike so this can't be too important.You may need to shop around to get the combination you want but it is possible.

Good luck.

Thanks bob... actually I looked at centaur, veloce and mirage. All the UT stuff gettin xpensier now as makes sence.

But this is the deal... Cranks, bb cups/bb axle, the 48T chainring and im still missing the RD. Doing numbers even with old squared tapper Centaur grey i get nearby 270 bucks shipped unless i get the stuff in pbk for example but with them who knows what they will send me hehehe. The other thing i noticed is that nobody stocks campagnolo, almost all the places i called they had a 2 days delay because they needed to order the stuff and the people who stocks campy sells super expensive. The chorus cranks are nice and have the combination i need plus i have the axle right in the bike already. I need to find the money now because looks like is easier just get that crankset. Anybody can borrow me 100 bucks??

I understand wieght is not important but making numbers even if that chorus crank is expensive always I can take the chainrings out and sell the crank. Each chainring cost like 150 bucks if i get them separetely (the coated ones)

UM :)