Hammertoe

I would like to build up a 9 speed road bike with a XTR derailer and wondering which I should use...

The chainrings are going to be 48/36/26 and the cassette will be 11/34...

Do I need the standard shifting model and would a GS (medium cage) have enough chain wrap or should I go with the SGS...

Thanks

Al1943

Go to the Shimano website and find the chainwrap capacity for each derailleur in question. Subtract the small ring teeth from the big ring teeth, subtract the small cog teeth from the big cog teeth, add the two results together and that is the minimum capacity that your rear derailleur should have.
(48 - 26) + (34 - 11) = 45

You can use either a high normal (more common) or a low normal (rapid rise) derailleur. If you use the low normal the brake lever will shift the derailleur toward smaller cogs (backwards from road derailleurs).

Al

Hammertoe

Ok, so it is "Top Normal" for me...

The only derailer that has a 45 capacity is the M972 (most expensive model), the others have a 43 capacity...

Anyone know if this derailer will work with Ultegra shifters...

Al1943

I hate to say for sure but I'd bet the 43 would probably work fine. If there is a problem it will be when the chain is in the smallest ring, smallest cog combination which should be avoided anyway.

Al

JiveTurkey

+1, you'll probably be fine. You can minimize the problem by using the minimum amount of chain as possible. I prefer the Sheldon method (I think it's Park's too): 1) Wrap the chain around the largest chainring and largest cog (do not route through the rear derailleur), 2) Find the length that is just long enough to connect (outer link to inner link), 3) Add one full link (1", outer plus inner).

This will give you a chain long enough to allow the 48T/34T combo (which should also be avoided by the way), but short enough to where the derailleur will only fold into itself in the 26T/11T and maybe 26T/12T combos (which should be avoided anyway).

[edited chainring sizes]

Retro Grouch 

Without a doubt you'll be fine with the derailleur with 43t slack take up.

Think about how you really ride your bike. You only use the granny chainring with the largest 2 or 3 rear cogs. You'll never, never, ever need enough slack take up to handle the 26/11 combination.

On the other hand, like Jive said (I almost called him the turkey), it's important that your chain be long enough to safely cover the big/big combination even though you'll never deliberately use that combination either.

JiveTurkey

I'm The Jive, so that's what you call me. You know that or His Jiveness or Jiver. Or El Jiverino if you're not into the whole brevity thing.

(I hope someone gets the paraphrased reference.)

JiveTurkey

Don't know if these two questions were cleared up:

GS or SGS? Definitely SGS

Work w/Ultegra shifters: Rear, definitely; Front, yes if using a road type front derailleur (or use MTB-style with a cable travel agent) AND the front shifter is triple-compatible

Hammertoe

Thank you everybody, including Mr. Jive...

I will be using a 9 speed triple Ultegra FD, Ultegra 9 speed cranks with 48/36/26 TA chainrings, Ultegra triple shifters and the XTR RD...

The cassette will be a 12/26 for my regular routes and 11/34 for hillclimb races...

Thanks again for all the replies...

Al1943

I replaced the chainrings on my wife's 9-speed Ultegra triple with TA Alize rings, 49-39-28. The FD is the standard Ultegra 9-speed triple. The 8/9 speed TA rings are thicker than the original Shimano rings and this caused some problems.
With the chain on the big ring and smallest cog a shift to the middle ring caused the chain to run with the side plates on the tips of the teeth instead of engaging the teeth. To correct this I added a 1.5 mm bottom bracket spacer to move the chainline out slightly but I also had to file the backside of the teeth on the middle chainring to get the chain to drop over the teeth.
With the chain running on the largest cog a shift from the middle chainring to the smallest chainring sometimes causes the chain to drop to the inside.
TA now makes 10-speed compatible chainrings, I'm wondering if that means they are spaced narrower or if the teeth are thinner.
The wife's bike is CF with a braze-on type FD hanger. It was necessary to grind the inside of the hanger down in order to get the FD low enough. A clamp-on derailleur would not have this problem.

Al

JiveTurkey

That sounds good, but I'm confused about the crank. Doesn't the middle and outer chainring position of the crank use a 130mm Shimano standard BCD (bolt circle diameter)? If that's the case, you may not be able to use a 36T middle ring as 130 BCD requires at least a 38T ring. Or does this crank use a 110mm compact BCD?

Al1943

Good catch! The Ultegra middle ring is a 130 BCD, smallest possible middle ring is a 38.
What about it Hammertoe?

Hammertoe

Yes good catch...

Minimum teeth on the 130 BCD is 38...

Middle ring is a 38, I purchased 48/38/26 from Peter White Cycles..


I hope this shifts OK, I do not think I am up to filing teeth on the chainring...

I should be building the bike up in May, I will post pics when finished...


Thanks again...

Another BF satisfied customer...

I_bRAD

The XT is way cheaper and pretty much just as good from a functional standpoint.

I just set up my current commuter/touring bike with the SGS XT. 48-24 up front, 12-28 in the back. I considered the 11-34, and you could do it for sure with 48-26 on the front but I didn't think I needed as wide a ratio as it's pretty flat around here.