Shimergo with Doubletap?...SHAM????
 

Greetings mechanical gurus!

I'm building up an 8 speed bike right now and am considering going Shimergo and using Campy shifters but I've read on Lennard Zinn's blog that SRAM doubletap shifters pull the same amount of cable as Campy 10s...

Has anyone out there tried SRAM 10 speed shifters with a shimano 8 speed rear derailleur and cassette?...

Would I be better off using a SRAM front derailleur with SRAM shifters (or a campy front derailleur with campy shifters) or will I be fine using a Shimano front derailleur?...

Where do the extra two clicks end up?....are they on the inside or outside of the cassette?

Also, I have a choice of using two different rear derailleurs: a 9 speed short cage 105 or an early 90's era short cage 105 with a far stronger spring...which one would yield better results with a campy or SRAM shifter?

Thanks in advance for your insight!...

The extra clicks should be inboard.

Make of front derailleur shouldn't matter much at all.

The geometry on the Shimano derailleurs should be identical; assuming the old one isn't worn I'd use it cause the stronger spring will provide more reliable shifting (I've modded derailleurs to increase the tension of that spring).

Can't answer your other questions.

HMMM...No one seems to have tried SRAM 10sp. Doubletap shifters with a Shimano rear derailleur and 8 speed cassette...

After measuring the cable pull of my old Shimano 8 speed barend shifters at 3mm per click (identical to Lennard Zinn's measurement of SRAM's Doubletap cable pull), I have decided to take the risk and order a set of Rival shifters to try for myself...

If it works, I'm naming the pairing SHAM...If it doesn't, I'm calling it Doublecrap...

I'll keep you posted...

Just hope Zinn was nice and accurate... how did you measure the cable pull?

Good luck... seems like a clever gradual upgrade path from 8spd Shimano to 10spd SRAM, if it works

I ran the cable in the shifter and then firmly secured the other end in a bench vice...In order to make a clean measurement, I removed the barrel adjuster...I pulled the cable tight and marked where it entered the shifter with electrical tape...I then shifted through seven clicks and used calipers to measure the amount of cable pulled: 21mm...I divided that number by 7 which results in 3mm per click...Since I was sinking a few hundred bucks into the purchase, I repeated the test three times to be sure and came up with the exact same result every time...Though I've never met the man, Lennard Zinn seems to be a pretty precise fellow so I'm taking him at his word...
It's actually not an upgrade path, I'm building up a brand new bike with all new parts (except for the old shimano rear derailleur)...I'm just not impressed with the durability of 9 and 10 speed drivetrains...

My understanding is that Shimano and Campy pull different amounts of cable depending on the shift, while SRAM is the same for every shift. That doesn't seem to have been a problem for Zinn's frankenbike, but it could be for your combo. I'm interested to see how it goes though. It could be a nice alternative for putting integrated shifters on a bike with a mountain cassette (touring, cyclocross, etc). The double-only front might be an issue of course.

http://c0d3.name/images/double-facepalm.jpg

3mm per shift on average.

Might wanna check how much each shift actually is...

Received my parts order and assembled my bike this evening...
SRAM Rival shifters and front derailleur, SRAM 890 chain, SRAM 850 12-23 tooth 8 speed cassette, Shimano 105 5500 rear derailleur, Shimano R700 crankset with 1.2mm spacers between the small ring and the spider with Jagwire Inline J2 inline adjusters...
Initially, it shifted like crap but after applying a bit of oil on the cables where they entered the housing and some patience on my part with the limit screws and the barrel adjusters, I was able to get the system dialed in pretty well...The biggest issue right now is some front derailleur rub in the more extreme gear combos...I suspect that if I remove the chainring spacers and give the front derailleur a bit more TLC, I can have it shifting as well as any other system out there...
I'm not all that into the new style Jagwire inline adjusters....They look nice but they're not as easy to use as the old ones...

Here are the facts. Zinn is wrong about the cable pulls of Campy 10 and SRAM 10 being the same. SRAM pulls a uniform 3mm per shift. Campy pulls 2.5mm five times 3mm twice and 3.5mm twice. The total pull divided by 9 averages just over 2.8mm. After only 5 pulls, a SRAM shifter would pull enough cable to make 6 shifts on a Campy 10 drivetrain. That's a huge difference.

It just so happens that Shimano 8 shifters average a nearly identical 2.8mm of pull per shift, but they are also nonuniform, so a SRAM shifter would greatly overshift on the first several pulls. A Campy 10 shifter would probably work a whole lot better than SRAM 10, with Shimano 8.

Interestingly, I swapped out the rear derailleur on the SHAM bike for a 24 year old Shimano 105 RD-1050 6 speed derailleur that I bought at the local community bike co-op for five bucks and the rear shifting is now flawless...Most likely the credit for the improved shifting is due to the RD-1050's stronger spring and the flexibility of the Shimano floating pulley...

My only stumbling block right now is the chain rub with the 8 speed chain and the SRAM Rival front derailleur...I'm going to try and source out an 8 speed Shimano or Sachs front derailleur to see if they'll play nice with the Rival shifter...

http://sphotos.ak.fbcdn.net/hphotos-..._5773441_n.jpg