Login required to started new threads

Login required to post replies

Please confirm math/understanding re: shimano rear derailer
Quote | Reply
A couple of basic questions for more experienced bike peeps:

1) I have a shimano ultegra rear derailer, it is 10 speed on a 2005 cervelo dual, and there currently is a 12-28 cassette with a 50-34 compact up front. I believe it is a long cage 6700 based on the current combination I have but I could not find any marks or model # on the derailer, is this a long cage (vs. a short cage)?

2) Based on google, the capacity is 39 teeth. Math computation of a 50-34 compact, the max rear cog would be 11-34 coming in at 39 teeth (16+23)??? So, I can fit a 11-32 on the rear with no issues?

(I know this question has been explored before but I could not piece all the information of the threads together).
Quote Reply
Re: Please confirm math/understanding re: shimano rear derailer [auto208562] [ In reply to ]
Quote | Reply
Long cage is generally for triple chainrings.
If yours was factory setup, you probably have the shorter cage.
2005, that year the rear der was probably limited to 28t. Some people get away with more. Newer do 30 or maybe 32.
Others know more than me, but I don't think 32t will work.
Quote Reply
Re: Please confirm math/understanding re: shimano rear derailer [auto208562] [ In reply to ]
Quote | Reply
I'm with Rumpled. I suspect your derailleur would be short cage, and designed to take a maximum cog of 28 teeth on the cassette.
Quote Reply
Re: Please confirm math/understanding re: shimano rear derailer [sharkbait_au] [ In reply to ]
Quote | Reply
Shoot. I was hoping I could just swap out the rear cassette. I guess I have to research about the derailer too. Thanks for the info guys.
Quote Reply
Re: Please confirm math/understanding re: shimano rear derailer [auto208562] [ In reply to ]
Quote | Reply
Visual difference between long and short cage seems striking to me. Google image long cage and short cage and compare with what you have.

________
It doesn't really matter what Phil is saying, the music of his voice is the appropriate soundtrack for a bicycle race. HTupolev
Quote Reply
Re: Please confirm math/understanding re: shimano rear derailer [departed] [ In reply to ]
Quote | Reply
This looks like long, right?


Quote Reply
Re: Please confirm math/understanding re: shimano rear derailer [auto208562] [ In reply to ]
Quote | Reply
that is short ... but its hard to tell in that photo. pull it forward. its usually pretty easy to tell.

-----------------------------------------------------
But, he said I was an Ironman.
Last edited by: kwolo: Apr 19, 14 10:00
Quote Reply
Re: Please confirm math/understanding re: shimano rear derailer [kwolo] [ In reply to ]
Quote | Reply
Can you tell with this one? Thanks for your help.


Quote Reply
Re: Please confirm math/understanding re: shimano rear derailer [auto208562] [ In reply to ]
Quote | Reply



This is a long cage on a felt z3. Ultegra 6800.. It's my Mom's, it has a 50/34 and a 12-28.


As you can see it is substantially longer than the one in your photo

-----------------------------------------------------
But, he said I was an Ironman.
Last edited by: kwolo: Apr 19, 14 10:27
Quote Reply
Re: Please confirm math/understanding re: shimano rear derailer [kwolo] [ In reply to ]
Quote | Reply
Yea, that looks like a big difference. Thanks for your help and confirmation. I've now got to weigh the cost of the new dearailer + cassette (and maybe chain) vs. sucking it up with what I got. I think I'll be ok with the gearing for my next race but an extra one or two cogs on top gives me peace of mind.
Quote Reply
Re: Please confirm math/understanding re: shimano rear derailer [auto208562] [ In reply to ]
Quote | Reply
Yea, it will come down to what you think you will need.

I checked again and I guess the bike in the photo has a 12-30, not 28. So that explains the Long cage stock on the bike. I think the felt website lists the cassette as 11-25. But, I built that bike directly out of the box about 4 days ago and that's what it came with.

Good luck on your decision

-----------------------------------------------------
But, he said I was an Ironman.
Quote Reply
Re: Please confirm math/understanding re: shimano rear derailer [auto208562] [ In reply to ]
Quote | Reply
Short for sure. One way to think of it is that on short cage, the two jockey wheels are very close -- couldn't be much closer.

On ebay new long cage R. D. is $52 (105), or $99 (ultra), quick look at buy it now offerings (slight weight difference between 105 and ultegra, but you'll never know difference. Chain is $40-50. Cassette is $50-100 (sram). For sure you could do it for $150. Switching everything out is 30 min to 1 hour job. Got any friends who could help you do this?

Now you can agonize over whether you should get more expensive/higher end components, but the only practical difference is weight and you'd be talking about something on the order of 100-200 grams (like the weight of 3-6 gu s).

________
It doesn't really matter what Phil is saying, the music of his voice is the appropriate soundtrack for a bicycle race. HTupolev
Quote Reply
Re: Please confirm math/understanding re: shimano rear derailer [departed] [ In reply to ]
Quote | Reply
Would another option be to just get a compact crankset in the front?
Quote Reply
Re: Please confirm math/understanding re: shimano rear derailer [jl2732] [ In reply to ]
Quote | Reply
Not for the original poster.

________
It doesn't really matter what Phil is saying, the music of his voice is the appropriate soundtrack for a bicycle race. HTupolev
Quote Reply
Re: Please confirm math/understanding re: shimano rear derailer [auto208562] [ In reply to ]
Quote | Reply
I would just try it. I've used a 32t cog with the 105 short cage from that era before. Cross chaining caused an issue though.
Quote Reply
Re: Please confirm math/understanding re: shimano rear derailer [corneliused] [ In reply to ]
Quote | Reply
If I get this correctly, you currently are 34-28 in your lowest gear.
Do you really want to ho lower?
I'm a Clyde and a horrible climber. I run 34-27 at my lowest. Anything I can't pedal with that I would do the walk of shame.
Quote Reply
Re: Please confirm math/understanding re: shimano rear derailer [Rumpled] [ In reply to ]
Quote | Reply
You're incorrect. Try a 30% gradient however and let me know. All I meant to say is I've used a 32t cog with a derailleur that was only rated for 28t. I also exceeded the rated capacity w/o much consequence.
Quote Reply
Re: Please confirm math/understanding re: shimano rear derailer [Rumpled] [ In reply to ]
Quote | Reply
Rumpled wrote:
If I get this correctly, you currently are 34-28 in your lowest gear.
Do you really want to ho lower?...

This is my thought as well. OP, are you running out of gears while climbing that makes you want lower gearing?
34-28 is pretty low gearing on road & tri bikes. In fact, that's generally what I recommend to average athletes on courses with a lot of climbing like Savageman. If that doesn't cut it, then we've got some work to do on the engine.

____________________________________________
Don Larkin
Reach For More
http://www.reachformore.fit/
USAT Lvl1 Coach, NSCA-CPT, NASM-CPT, BS Exercise Science
Quote Reply
Re: Please confirm math/understanding re: shimano rear derailer [TriMyBest] [ In reply to ]
Quote | Reply
The only reason I was thinking about going to the 32 was I have IMLT on my schedule and after doing several searches on this race, it seems several people though the 32 was a good backup for the 2nd loop. I did use a 12-28 at wildflower and it was ok but not sure it would have been if I do a 2nd loop. For me, it is more for precaution...the amount of climbing + altitude. I am not sure how altitude will affect my ability to race/climb, so I'm just worried (may be unwarranted and a little bit of over analysis) on that 2nd loop.
Last edited by: auto208562: Apr 20, 14 9:12
Quote Reply