[Mr. RMB]

Just took apart my 2007 XTR crankset.

Rings:
22T: 22 grams
32T: 44 grams (carbon/ti)
76T: 76 grams (carbon/ti)
Bolts: 14 grams

Rings & Bolts
156 grams

Bottom Bracket:
85 grams

Crank arms (no rings)
511 grams

Crank Arm Bolt
9 grams

TOTAL: 761 grams

 

[Hardtailforever]

76t big ring?! You must have some HUGE quads, eh?

Anyway, I just got mine and it weighs in at 768 on my scale, so that sounds about right. Not the lightest thing in the world, but like I've said before, the thing shifts like nothing I've ever used before.

 

[Mr. RMB]

Ya i found the stock 44 tooth too small so I upgraded...lol....

 

[akashra]

Don't you find there's a massive jump there? I mean, you wouldn't be able to use anywhere near the same gears you use on the rear chainring due to the massive size of a 76T front chainring - crossover would be a huge problem.

 

[Mr. RMB]

I was kidding....I accidentally wrote 76 tooth because thats how much it weighs.

The large ring is only a few grams heavier than an FRM 44t ring.

 

[Jesseg]

BB weight

That's interesting about the BB weight being significantly lighter than my raceface deus BB at, I think, 110 grams and I think FSA ones being about 130. I wonder who has got the lightest BB cups. Maybe keeping your external crank and changing to an XTR or perhaps even lighter cups might be an easy and economical way for some people to shave weight, particularly when bearings go anyway. If anyone else can measure their BB cups with and without the sleeve that some people won't want to run, that might be useful. If RMB could tell me how much of the 85 was the sleeve, I'd like to know. My frame has an "insulated" BB shell anyway, so I don't use that. It also seems like if water can get in at the spindle, the sleeve will keep it next to your bearings unnecesarily.

 

[Mr. RMB]

they are light!!!!!

My XTR FC M970 bottom bracket cups weigh 79. The "sleeve" weighs around 5. I don't see the point in the sleeve.

I'll start a new thread to get other peoples attension.

 

[dot]

What's the point using carbon/ti rings without saving ANY weight at all? They weigh like LX stuff.

 

[Mr. RMB]

They are supposed to last twice as long.....and who says they don't save weight?

You'd have to compare them to 2006 XTR rings....but since the entire crankest is lighter I'd say the rings contribute to a little of that.

 

[akashra]

Yeah, I'd imagine there would have to be some other benefits - I noticed the same thing with my cranks - they're 100g lighter than XTR cranks! (and about 1/5th the cost).

 

[sergio_pt]

Yeah, I'd imagine there would have to be some other benefits - I noticed the same thing with my cranks - they're 100g lighter than XTR cranks! (and about 1/5th the cost).

what crankset do you have?

 

[akashra]

It's actually just a standard Deore set.
However, after talking this over with a mate, we discovered why it weighted this way - the XTR includes the bottom bracket. The Deore crankset doesn't, and required a separate octalink bracket - adding about 280g. So the XTR in the end works out lighter.

 

[evilgeek]

so it's heavy as well as ugly.

 

[SBK]

They are supposed to last twice as long.....and who says they don't save weight?

You'd have to compare them to 2006 XTR rings....but since the entire crankest is lighter I'd say the rings contribute to a little of that.

Actually, the '06 XTR M960 rings are in fact lighter than the numbers you've posted. Here's how the '06 rings measured on my scale:

22t - 22g
32t - 40g
44t - 69g

The BB cups are apparently lighter on the new XTR crankset, as my '06s are 96g including the center tube. Between the heavier rings and lighter BB cups, it looks like a wash. The savings in the '07 must be in the arms. Makes sense that the '07 big ring is heavier, since it has to have "legs" to reach to the smaller chainring bolt circle, vs. the '06 which relied on longer integrated spider arms and an essentially round chainring.

 

[dan0]

Just took apart my 2007 XTR crankset.

Rings:
22T: 22 grams
32T: 44 grams (carbon/ti)
76T: 76 grams (carbon/ti)
Bolts: 14 grams

Rings & Bolts
156 grams

Bottom Bracket:
85 grams

Crank arms (no rings)
511 grams

Crank Arm Bolt
9 grams

TOTAL: 761 grams

hate to tell you but the big ring is aluminum, only the middle ring is carbon/ti

 

[Tracerboy]

not fair!

Hey, not fair! My XTR M970 weighs 790g all in, including spacer, crank fixing bolt (8g) with 175mm arms.

How did you get yours down to 768g?!

While I'm here, I'm not sure I understand the function of the little ring on the non-drive side arm. The instruciton say to rotate it after installation of the arm to 'take up play', so I assume you screw it up to the bearing, then tighten the little allen bolt.
What does this bit do? Apllies a load against the bearing? Helps seal the bearing? Can I toss it in the bin??!!

 

[macd]

Mine was also 790g. Because the left side crank arm presses on you need that adjuster to tension the arm against the bearing. Shimano redesigned the left crank arm interface from 06 because there was trouble with bearing play. Also don't use the al bolt to fix the left crank arm back on. Use the steel press piece that comes with the crankset.

 

[Tracerboy]

thanks...

..useful info, but this piece is not tensioning the arm against the bearing. The arm is on the axle, end of story. It does not connect with the bearing in any way. I tightened mine on up to 45Nm (with an accurate torque wrench) as per Shimano's instructions. It felt like it hit a stop at about 40 Nm, so it's on OK. But there is still about 10mm of gap between arm and bearing, with this little ring thing taking up about 5 of those 10mm. So I tightened the ring up by hand (using the little spanner they give you) so that it contacts the bearing and applies very slight pressure against it. Then tighten the allen bolt to hold in place.

I can only think that this gives the bearing extra lateral support....?

By the way, I did use the alloy bolt to tighten the arm on - it was fine up to 45Nm, no probs.

Because I am a dufus sometimes I also tried out the removal tool, as I forgot to put the 1 spacer in on the drive side!!! And I am happy to report that it works pretty well, if unconventionally......don't lose it!

 

[nino]

798g here...

i just read into this thread and it's interesting to see so many different weights. i weighed the 07
XTRs at 782g

 

[Tracerboy]

yeah, looks like I got reamed with my 790g set.....oh well!

Lets hope this chainset shifts well - I ditched my Extralite Ebones cos I was fed up with ISIS, so hopefully these bearings will last more than 3 months.

As for the 200 or so grams I just gained, I have managed to almost win them back with a KCNC seatpost (i/o Thomson), (-50g) XTR 07 rear mech (-20g) (i/o XTR06), and Syntace F99 stem planned (i/o FSA) -40g.

So the faithful old Sugar 1 is still at 9.55kg!

So Nino, u have an opinion on this preload ring thing? The instructions really don't explain at all what it's for.......