B1KE

I'm replacing a Shimano Tiagra rear derailleur because I accidentally stripped one of the bolts. On the website I have 2 options. Short cage and Medium Cage. I'm not sure which one to pick. Which is the one that suits the following bike specs that I have on my Specialized Secteur;


Crankset Shimano Tiagra
Chainrings 50/34
Front Derailleur Shimano Tiagra
Rear Derailleur Shimano Tiagra
Rear Cogs Shimano Tiagra, 10-speed: 12-30
Shifter: Shiamno Tiagra



Thanks for your help!

JonathanGennick 

I'm a little bit tired, so hope I am doing the math right. You have a 16 tooth difference in front, and an 18 tooth difference in the rear. You thus need a derailleur capable of soaking up 16 + 18 = 34 teeth.

Shimano should say on their site how many teeth each cage length is good for. I'm guessing you'll need medium, but check the numbers on the Shimano site to be sure.

Cross Creek

I'd say medium, based on Ultegras with which I'm familiar, but either will probably work. What cage does the one you're replacing have?

B1KE

Well that's what I'm trying to figure out; I'm a newbie and it's my first road bike so its a bit challenging but heres what happened

I accidentally stripped the bolt on my Tiagra 10 speed 4601 derailleur the shop replaced it with what I thought was a Tiagra 10 speed 4601 but it turned out to be a Tiagra 9 sped 4500. I find my low end and high end gearing is very weak and I have to switch into the big cog more often to get into gears that I was comfortable in at the small cog which is effecting my ride and performance.

The specs on the 9 speed 4500 are as follows;

Wide link design
• Total capacity: SS 31T, GS 37T

Specifications:
• Series TIAGRA
• Model No. RD-4500
• Pulley Cage: SS/GS
• Speeds: 9
• Max Front Difference 16T (SS)/22T(GS)
• Total Capacity 31T (SS)/37T(GS)
• Max Rear Sprocket: 27T
• Min. Rear Sprocket: 11T

What I'm wondering is if the above derailleur specs are even compatible with;

Crankset Shimano Tiagra
Chainrings 50/34
Front Derailleur Shimano Tiagra
Rear Derailleur Shimano Tiagra
Rear Cogs Shimano Tiagra, 10-speed: 12-30
Shifter: Shiamno Tiagra

If anyone could help me out with that I would greatly appreciate it because I'm just a noobie and I really want my bike working in tip top shape again.

Thanks in advance!

B1KE

How can I figure this out?

Bezalel

When staying within the same road groupset, short cage is for a double and medium cage is for a triple. In the change from 9 speed to 10 speed the capacity of the Tiagra groupset has been increased so when using a 30T cog it would be incompatible with almost all previous generation road derailleurs.

FBinNY 

You measure the distance between the pulleys. Shimano may have this dimension in their specs as "pulley distance" or cage length" or similar. In case it's not listed, short cages are typically 55mm or so, and medium cages 70-80mm depending on brand. Some companies offer long cages win the 90-95mm range.

Note, size names can be about as useful as they are with clothing, with one company's medium being another's long, but at least short tends to be pretty uniformly close to 55mm.

B1KE

I'm running a double chain ring in the front with 10 gears in the back, the specs are as follows;

Crankset Shimano Tiara
Chainrings 50/34
Front Derailleur Shimano Tiagra
Rear Derailleur Shimano Tiagra
Rear Cogs Shimano Tiagra, 10-speed: 12-30
Shifter: Shiamno Tiagra


Would I need a short or medium ring cage?

Drew Eckhardt 

Not necessarily. In the 10 speed era Campagnolo made short (55mm, double with no cassette bigger than 12-25 or 13-26), medium (72.5mm, double with all cogs, triple through 12-25/13-26), and long (89mm) cage derailleurs.

When they introduced 11 speed triples in 2012 they added an 82mm medium+ derailleur alongside short and medium.

dr_lha

With that set up: Short.

Ronno6

Well..................the short cage derailleur is good for 31 total teeth takeup.
The OP's requires one that will handle 34t.

Looks like the original medium cage derailleur needs to be replaced with same.

dr_lha

I haven't done the tooth calculations, but I'm damn sure that with a compact up front and a max 30T at the back, you can get away with the short cage. This is certainly true of my RD-5701 105 rear derailleur. Pretty sure you only need the medium cage if you're running a triple or want to go up to 32T max.

Ronno6

I agree that it would work.
However, if you rear the OP's other thread on this issue, where he took umbrage at someone's statement that it will work "fine," you will understand that he does not want a setup that he can "get away with."
Yes, you should never cross chain, which is the only scenario that would require the full capacity, but from
a strict specifications point, the short cage is rated for 31T; his setup is 34t.

This derailleur was replaced by a LBS; they should have replaced his broken derailleur with a like unit.

dr_lha

The RD-4600-SS is rated for 34T. The long cage version is rated for 39T. Not sure where you're getting 31T from? (EDIT: OK from the fact that the stupid LBS installed a 9-speed derailleur?)

RD-4600-SS

Ronno6

The LBS installed a 4500. Rated for 31t.
Shimano Tiagra Rd-4500-ss rear derailleur 9sp

However, I see your point.
He is looking for a recommendation for replacement, and you are indeed correct.

bikemig 

Is that what was installed? Not clear from the OP's posts whether the shop installed a short or medium cage version.

dr_lha

Yeah, OK I missed that weirdness. Why the hell did they replace a 10 speed derailleur with a 9 speed one?

Ronno6

Sorry. I have responded to both threads. The LBS installed a RD-4500, which is a short cage.

Must have been what they had on hand.
However, typically it should not have mattered. 6s,7s,8s,9s,10s; I have used them interchangeably without incident (except 7400 DA.)
In this case I have read that Shimano added the 30t cog when they went to 10 speed
in that group. Apparently, that's where the problem arises.

dr_lha

Somebody needs to find a new bike shop!

B1KE

I know what a mess, with my limited bike knowledge it is becoming frustrating.

B1KE

Hmm the problem is I don't know if I have the 34T or 39T installed But here is what happened since the install. The gearing is very off. For example I normally run in the small ring towards the high end of the gears but now I find the power very low in the low ring and have to switch up to the high ring more to maintain the same speed that I had in the small ring before.

It feels like the overall power band of the gears is off and I have to switch into higher gears to maintain the same power and speed I did with lower gears before.

Could it be the "too big" cage causing this? Or something else? I really don't know but any help would be appreciated.

B1KE

Here is what I have read about using a 9 speed deraileur with a 10 speed cassette on another forum

"The spacing between 9 speed and 10 speed is controlled at the shift lever.A 10 speed rear dérailleur will work with a 9 or 10 speed cassette and shifter. A 9 speed rear dérailleur is not compatible with 10 speed.
The width of the chain and the cogs is the biggest issue. The pulleys on a 10 speed dérailleur are narrower, and a 10 speed chain will not rest correctly on the jockey pulleys of a 9 speed dérailleur.
That does not mean it will not physically work, only that the shifting performance will be slow, you may drop gears unexpectedly, or have the chain skip unexpectedly.
Long story short, 10 speed should be 10 speed all the way throughout your bike for it to work consistently and properly.
Cable tension has nothing to do with cog spacing. That is designed into the shift lever. It is not adjustable, except by replacing the shifter. I hope that helps."


Which is why I want the original set up back because for me the gearing is messed up and I paid for a direct replacement, not an older or different model.

B1KE

Is that a matter of opinion or is that concrete the way it should be?

I'm seeing conflicing results here but from my limited understanding I think with running a double ring at the front an 10 gears on the back along with the Specialized Secteurs shorter top tube perhaps short is the way to go?

Ronno6

You've just pedaled into "The Twilight Zone"

If all else remained the same, there is no difference in gearing.
Besides, the cage on the 4500 is shorter than on the 4601.

I wonder if the LBS shortened the chain??
Again, that would have no effect on gearing.
I'm just wondering..........

Ronno6

The RD-4600-SS is has ratings that would indicate that it should function with your setup at least as well as the original unit..
(I am choosing my words carefully.)

As for the 6s thru 10s interchangeability, I stand by my experience.
I have several bikes with 6s-9s rear derailleurs with 10 speed shifters and cassettes; I am not going to change them.
I have always been happy with their operations. But, of course, I set them up myself!