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PostPosted: Mon Mar 17, 2008 7:59 am 
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It seems it does. Well, according to Lennard Zinn it does. I have been suspecting this myself since being told then shown that a SRAM RED cassette/Shimano free hub wheel/KMC chain combo will work on a Campy bike. Saw this feat at BikeNut. Interesting article from Zinn.

http://www.velonews.com/article/73404

However, I'm not interested in a RED drive train. I'm more interested in the RED RD working in an all Campy setup. I'm thinking this will work since all a rear derailleur does is move the chain in a perpendicular manner. The shifter does all the precise movement over the cassette. All you need to do is set the limit screws and you're set. I think this should work. What do you guys think? I'm interested in hearing from the peanut gallery. :)

I'd love to replace my Record RD with a lighter RED RD. Don't you?


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PostPosted: Mon Mar 17, 2008 9:54 am 
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Location: A bigger rock in the Pacific (AUS)
http://www.wheelworks.co.nz/drivetrain. ... S=S4&CR=S4

http://www.wheelworks.co.nz/drivetrain. ... S=C3&CR=C3

Sorry, I'd write something more, but I have an aweful headache.

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Posted: Mon Mar 17, 2008 9:54 am 


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PostPosted: Mon Mar 17, 2008 10:51 am 
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Location: Newcastle, UK
It wont work, the shifter pulls a set amount of cable per click, the distance the rear mech moves the chain is determined by a mechanical ratio of its design. Campy and SRAM mechs have different mechanical ratios and hance will move the chain a different distance per mm of cable pull. It is not as simple as you make out.

Also, as an aside. That wheelworks thing... needs some work, ive run all campy 10 with shimano 10 cassette no problems (it says it wont work). In fact a lot of people on here do just that.

Rich.


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PostPosted: Mon Mar 17, 2008 1:41 pm 
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As a mechanical engineer with many years of manufacturing and precision measurement experience, I find Zinn's info to be incorrect on occasion. I measured the cable pull on a Campy 10 RD a number of years ago and came up with a total of 25.5mm, not 27. The amount of cable pull is also not the same for each shift.

The first five shifts (starting from the smallest cog) were quite consistent at .10 inch or 2.5mm per shift. The 6th & 7th shifts measured .12 inch or 3.0mm, and the 8th & 9th shifts measured .14 inch or 3.5mm. The total of all shifts moved the cable (25.5mm).

Of course their will be some small variation in the total pull, depending on how the limit screws are set.

SRAM's shifter is supposed to pull 3mm of cable on every shift, if the info on the SRAM website is correct. A Campy shifter would undershift on the first five shifts, then shift correctly twice and over shift twice. The total shortfall in cable pull is only 5-6%, BUT the RD is only moving 3.95mm per shift not 4.12mm. That means it will come up quite a bit short of the correct RD travel. By my calculations, the total RD travel would be 3.5mm short of what is needed, or nearly a whole cog's worth of spacing.

The bottom line is, you need a J-tek to correct the shifting. Even then, the Campy shifter won't produce the uniform pulls of the SRAM shifter.

I just remeasured the Campy cable pull this morning and got the same results. It's not rocket science. With the shifter on the first cog, wrap a piece of masking tape around the shift cable, 10 or 20mm in front of the cable stop on the chainstay, then measure the pull for each shift and the total.


Last edited by DaveS on Mon Mar 17, 2008 3:30 pm, edited 5 times in total.

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PostPosted: Mon Mar 17, 2008 2:04 pm 
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Find it hard to believe he got a simple measurement wrong. The Jtek adapter sounds interesting. From the article:

Quote:
For a simple solution involving an adaptor that you can by and install easily, you can use a Jtek ShiftMate It appears that Jtek now even sells an adapter to allow the use of a Campy 10-speed shifter with SRAM RED derailleur and cogs.

I did measure the difference in cable pull between SRAM and Campy 10-speed shifters. Nine clicks of a Campy lever pulls 27.0mm of cable, or 3mm per click. Nine clicks of a SRAM lever pulls 27.9mm, or 3.1mm per click. Jtek's adapter may adjust for this minuscule difference, but in my experience, it works perfectly with no adapter.

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PostPosted: Mon Mar 17, 2008 2:48 pm 
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Why does this have to be restricted to SRAM Red? Is there something different about the shifting mechanics in the Red group that make it incompatible with Force or Rival?

Just seems trivial to keep saying "SRAM RED" when, in fact, any solutions will be cross-compatible with SRAM's entire road lineup.


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PostPosted: Mon Mar 17, 2008 4:33 pm 
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Ok, let's say that Zinn did get it wrong, contrary to his findings in his article and that no one here has yet tried this combination of an all SRAM drive train and Campy shifters. Certainly, the responses so far believe that it is not possible but have you actually tried it?

If we have actual riders who have tried it and failed, then, yes, Zinn's article is of no value.

But, again, I'm more interested the Red RD and a Campy drive train setup. It seems, no one here has yet tried this combo. Well, being the curious person that I am, I ordered a Red RD from Performance (17% off one item, today only for St. Pat's day). I want to test it myself, instead of rely on the wheelworks site as the definitive answer. Anyway, if it shouldn't work, I'll just return it and at least then I can say, "it does not work" after all that is said and done.


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PostPosted: Mon Mar 17, 2008 4:33 pm 
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What I am left asking is WHY? Zinn obviously can't even wrap his bar tape, let alone pick a consistent groupset. Centaur levers with Red components throughout.... :?:


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PostPosted: Mon Mar 17, 2008 4:43 pm 
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coloclimber wrote:
What I am left asking is WHY? Zinn obviously can't even wrap his bar tape, let alone pick a consistent groupset. Centaur levers with Red components throughout.... :?:


I guess he likes knowing what works and doesn't as do I. And, yes, his bar tape is a little strange but so is mine. And why Centaur? Maybe cause it's cheaper to experiment with Centaur then to buy Chorus let alone Record.

My motivation is that I just I want to know if a RED RD and Campy drive train will work. And of course, it's this weight thing too. LOL


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PostPosted: Mon Mar 17, 2008 8:10 pm 
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XL_Carbon wrote:
coloclimber wrote:
What I am left asking is WHY? Zinn obviously can't even wrap his bar tape, let alone pick a consistent groupset. Centaur levers with Red components throughout.... :?:


I guess he likes knowing what works and doesn't as do I. And, yes, his bar tape is a little strange but so is mine. And why Centaur? Maybe cause it's cheaper to experiment with Centaur then to buy Chorus let alone Record.

My motivation is that I just I want to know if a RED RD and Campy drive train will work. And of course, it's this weight thing too. LOL


From the look of the bars its the odd new deda's that i doubt anyone could wrap smoothly with those silly "power eggs".
If he's right it means those nice Sram tt levers will work with campag mechs :D


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 Post subject: SRAM Parallelogram?
PostPosted: Tue Mar 18, 2008 12:57 am 
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What is different in the SRAM Parallelogram that they can have linear (3mm) cable pull per shift?
Also: Is dura ace cable pull linear?


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 Post subject: Re: SRAM Parallelogram?
PostPosted: Tue Mar 18, 2008 1:28 am 
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rabo16 wrote:
What is different in the SRAM Parallelogram that they can have linear (3mm) cable pull per shift?
Also: Is dura ace cable pull linear?


Actually, though I'm not an expert about all three road RD brands (Campy, Sram, Shimano), it seems there is no mechanical difference between the RDs. The differences are in the shifters and cassette. How much pull a shifter moves the derailleur over the cassette and how the cogs are spaced is the key to precise shifting. The parallelogram movement shouldn't make any difference in it's function. It's just a mechanism for moving the chain.

That's why I posted the question can a SRAM Red RD be used with an all Campy drive train. I guess I'll find out when I get the derailleur and test it since no one, yet, has come forward to verify this. Kind of an interesting experiment just like Zinn's article. Besides, if is does work, that means more grams save using Red over Record for the RD.


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 Post subject: Re: SRAM Parallelogram?
PostPosted: Tue Mar 18, 2008 2:04 pm 
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XL_Carbon wrote:
Actually, though I'm not an expert about all three road RD brands (Campy, Sram, Shimano), it seems there is no mechanical difference between the RDs. The differences are in the shifters and cassette. How much pull a shifter moves the derailleur over the cassette and how the cogs are spaced is the key to precise shifting. The parallelogram movement shouldn't make any difference in it's function. It's just a mechanism for moving the chain.

That's why I posted the question can a SRAM Red RD be used with an all Campy drive train. I guess I'll find out when I get the derailleur and test it since no one, yet, has come forward to verify this. Kind of an interesting experiment just like Zinn's article. Besides, if is does work, that means more grams save using Red over Record for the RD.


You're a bit confused. If there was no mechanical difference in the RDs, then SRAM and DA shifters would pull the same amount of cable to make the RD move the same amount, since their cog spacing is the same. The parallelograms are not the same, so the shifters pull different amounts of cable to perform exactly the same job. If the RD's were all the same then you could just put a Campy RD on a SRAM or DA bike. I can guarantee you that won't work.

The folks a J-tek have all this figured out and that's why they offer so many models of shiftmates.

Although A J-tek can correct the total cable travel, I don't believe that they can make a SRAM shifter work exactly like a Shimano or Campy models, since those don't pull equal amounts of cable on every shift. About the best that can be done is to produce an average pull that results in the correct total cable travel and RD movement.


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PostPosted: Tue Mar 18, 2008 2:11 pm 
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That RD design makes a difference to shifting is proved by the changes Campag made to the parallelogram action of their RDs a number of years ago - when they moved from metal to carbon on the Record RD. This change required a different shifter ratchet to maintain compatibility.


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Posted: Tue Mar 18, 2008 2:11 pm 


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PostPosted: Sat Oct 04, 2008 12:43 am 
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Location: Penzance
Hi, I know this is old thread now but I have just set up Campy Xenon 10 speed brifters with Sram Rival rear mech and Shimano 10 speed cassette for a friend.It shifts very well indeed for now and is a very cheap setup. The Sram rear mech is designed to carry on working with a bent mech hanger

One of my own bikes has Sram Force (with Record qs front mech which is superb) but half way into a 100 mile ride I had a noisy chain as the indexing was off a bit and gradually getting worse.When I finally stopped to look at I realised the mech hanger had become so loose it flapping around.I was surprised it still shifted at all.


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