|Spacers for chainring bolts||McAndrus|
Oct 28, 2001 5:27 AM
|I run standard Campy 53-39 chainrings. When I'm on the 39 in front and 12 in the rear, the chain rubs against the 53 ring. Please, no lectures on a crossed chain line :-).
I've read where there are spacers you can use on the chainring bolts to push the 53 out a mm or two. I've been looking at the web dealers and I can't find any.
Does anyone know where I can find these spacers?
|re: Spacers for chainring bolts||Jofa|
Oct 28, 2001 10:56 AM
|I don't quite know which responses you intend to prevent by your 'no lectures' condition, but I presume you know that this combination is not recommended partly because it may result in chain rub against the large 'ring, as you describe.
When I worked in a shop a few years ago we used to get these spacers from Fisher International, a large UK distributor who deal in bulk supplies of oddments like this. I'm sure that your local shop can get hold of some. They are intended to solve problems which occured when mismatched components were for other reasons used together, not to improve the function of matched components which I assume you are using: you may find unpleasant results like the chain dropping between the two 'rings. Perhaps some of our current shop 'wrenches could elaborate.
|Your point is well taken||McAndrus|
Oct 28, 2001 11:59 AM
|The lecture I'm trying to avoid is the one about using the big cogs with the small ring and the small cogs with the big ring. In other words; don't cross-up the chain line while riding.
You're point about potentially dropping the chain between the rings is well taken - I hadn't considered that.
Yes, the components are matching - it's all Campy stuff and I'm still surprised about the rub in the 39-12 gearing. I've heard others complain about that as well. My other bike has a triple 36-42-52 and it does not rub in the 42-12 position. But then (without measuring) I'm assuming the 42-52 are in different positions in the chain line than are the 39-53.
Okay, sorry to get long winded but you've answered my question. Thanks.
|Not a lecture, just some facts||Kerry Irons|
Oct 28, 2001 2:41 PM
|Fact 1: what you are experiencing is very common. If your chain line is right (chain rings centered on the center line of the cassette) then they only realistic opition you have is to goof up the chain line by moving the right crank farther to the right. Even this might not really be realistic depending on your BB length choices.
Fact 2: as noted in another post, you would run the risk of dropping and jamming your chain between the two front CRs if you added even a mm of spacing.
Fact 3: spacing the inner CR closer to the BB would probably mess up your front shifting, as the chain would have to make a sharper angle to catch the large CR from the small CR. Dropped chains would become more common shifting large to small, and balky shifts would be common going from small to large.
Fact 4: 53/16 is the same as 39/12 and will result in a lot less chain and cog wear.
So, why is it you want to run the 39/12?
|It's totally for convenience||McAndrus|
Oct 29, 2001 3:47 PM
|I'm just going to have to learn to live with it, I guess. Here's where I use (or would use it) - with a fast group, in the 39-13.
Making one rear shift up is a no-brainer for instance acceleration. Making two shifts 39-53 and 13-14-15 is more difficult while trying to hold an accelerating wheel in front of me.
But, I have adapted in the past and will continue to adapt my shifting style. (My niece - who used to race for the University of Michigan once asked me "how did you learn how to shift?" I said, "Honey, I'm still learning.")
Thanks for the advice, guys.
|Two shifts?.....||Len J|
Oct 30, 2001 4:39 AM
|You make it sound like you do them sequentially. Is this true?
Why not try simotaneously? I have found that shifting 39 to 53 with my left hand while shifting 15 to 16 (Or similar) at the same time with my right hand gives me higher gear inches (slightly) and allows me to maintain (or accelareate)speed. If you want to upshift both front & back, you use the brake lever shift on the left while using the shift lever on the right, just do them both at once. You have to time it right (I use cadence awareness) to do it right, but it works pretty well. You can also do a second shift pretty easily.
It also works in the opposite direction.
|re: Another Option||KStone|
Oct 28, 2001 2:59 PM
|You could put the 1mm "spacer" between the frame and BB on the drive side. This would move the crankarm and chain rings to the right, possibly improving the chain line without the chain suck problems of just spacing out the big ring.
|re: Spacers for chainring bolts||grzy|
Oct 29, 2001 11:26 AM
|A properly designed, setup and adjusted bike should NOT have this problem. The fact that you do indicates that something is out. Putting spacers in there will really mess with the shifting, both interms of the chain sliding along the top of the 39 and the index shift points having the wrong spacing. Your propsed course is treating the symptoms, not the cause.|
|No problem?||Kerry Irons|
Oct 29, 2001 5:48 PM
|Grzy, every racing bike I've ever seen has this problem (a bit of chain ring rub on the small-small combo), so I don't see where you say this shouldn't be happening. My bike's chain line is dead on, I have 40.6 cm chain stays with a 13-23 9 speed and 39/53 front, and I have this problem. I can ride in this setup, but the chain definitely is contacting the large CR, so I just don't do it. The only way to eliminate this problem on my bike would be to space the crank farther to the right, which would goof up the chain line. How would you properly "design, set up, and adjust" my bike to eliminate this "problem"?|
Oct 29, 2001 6:32 PM
|Still waiting for an answer to Kerry's question on why anyone would want to run a 39x12 . . .anyone?|
|Saw the answer, thanks.||jacques|
Oct 29, 2001 7:01 PM
|"For convenience" makes sense on one level. A quick drop into the last cog you got is always quicker than a double shift.
As you ride more and more , you'll develop a feel for what's happening in the group. Long before you need to go to your 39 x 12, you will have gone to the big ring. It's difficult to describe, but the group shift from small to large ring is usually happens at a definite point in the ride. If you miss it, well yes, you might have to do some 39x12 hammering until things calm down.
For what it's worth - given the same gear inches, a larger number of teeth are a bit easier to push than a smaller number. Give yourself a break and get on that 53, even if the ride was advertised as one of those "small ring only" rides. These rides never stay in the small ring anyway for long ;-)
|re: Dump the 39 and get a 42.||dzrider|
Nov 1, 2001 7:43 AM
|The increased diameter will lessen the contact with the big ring. If necessary you can increase the size of your biggest two rear cogs to keep the easiest gears similar to what you have now.|| |