Weight Weenies
* FAQ    * Search    * Trending Topics
* Login   * Register
HOME Listings Blog NEW Galleries NEW FAQ Contact About Impressum
It is currently Mon Sep 26, 2016 10:04 pm
Recently the board software has been updated and there are some known bugs/failures:
- Avatars are currently not being displayed ✔ FIXED
- Tapatalk connection is currently broken ✔ FIXED
- Avatars cannot be uploaded ✔ FIXED

Please note that we will soon do some changes in WW board template design in case to get a fully mobile/desktop responsiveness board!
If you find more errors please post it here: http://weightweenies.starbike.com/forum/viewtopic.php?f=7&t=139062


All times are UTC+01:00





Post new topic  Reply to topic  [ 10 posts ] 
Author Message
 Post subject: xtr40-28 vs xx/xo 39-26
PostPosted: Fri Apr 20, 2012 3:35 am 
Offline

Joined: Thu Apr 19, 2012 5:04 am
Posts: 4
which is better for 29er xtr 40-28 or xx/xo 39-26? please help me decide..thanks
:)


Top
   
PostPosted: Fri Apr 20, 2012 3:46 am 
Offline
Shop Owner

Joined: Sat Jun 13, 2009 4:02 am
Posts: 1980
Location: NoVA/DC
ive had both. both are exceptional. my vote is for the xx because of the slightly lower gearing, but that would really depend on the terrain you ride.


Top
   
Posted: Fri Apr 20, 2012 3:46 am 


Top
   
 
PostPosted: Fri Apr 20, 2012 3:40 pm 
Offline

Joined: Thu Apr 19, 2012 5:04 am
Posts: 4
thankyou :D


Top
   
PostPosted: Sat Apr 21, 2012 1:57 am 
Offline

Joined: Tue Dec 16, 2003 4:24 am
Posts: 956
You can get an XTR 38/26 crank too.


Top
   
PostPosted: Sat Apr 21, 2012 4:53 am 
Offline
Shop Owner

Joined: Sat Jun 13, 2009 4:02 am
Posts: 1980
Location: NoVA/DC
the xtr 38/26 is a different crank. it's actually their triple crank with an inner 26 and middle 38. chainline is inboard more because of it. if your bike takes a direct mount front derailleur, you have to be specific with your fd choice.


Top
   
 Post subject: xtr40-28 vs xx/xo 39-26
PostPosted: Thu Apr 26, 2012 2:08 pm 
Offline

Joined: Tue Jul 12, 2011 4:41 am
Posts: 31
thisisatest wrote:
the xtr 38/26 is a different crank. it's actually their triple crank with an inner 26 and middle 38. chainline is inboard more because of it. if your bike takes a direct mount front derailleur, you have to be specific with your fd choice.


Yes, but the weight difference is negligible and front shifting is excellent. I have the 26-38 on my Tallboy and Highball and love it. In fact, I put a 24t on my Tallboy and it works great for lots of climbing on long rides. I find that I spin the easier gears better, have more balance at slow speed, have less cramps and more endurance with the 24t. For perspective, I am 6'1", 170 and won my cat 2 age group (33-34) last weekend at sea otter....this is not coming from a heavy, slow or weak rider that just can't push bigger gears.


Top
   
PostPosted: Sat Apr 28, 2012 1:46 pm 
Offline

Joined: Thu Apr 19, 2012 5:04 am
Posts: 4
its great, im waiting for my highball alu..i am just not sure whether i can live with two more teeth with 28 vis a vis 26 teeth..


Top
   
PostPosted: Sun Apr 29, 2012 1:14 am 
Offline

Joined: Mon Jul 18, 2011 8:01 am
Posts: 1
I have a 26 xtc advance and put a xtr 28 40 it which I find great. Could go with a slightly smaller front in the narly climbs though.
Just brought a 29er xtc and putting on the xtr 26 38 which I'm hoping will match the 26.


Top
   
PostPosted: Mon Apr 30, 2012 8:54 pm 
Offline

Joined: Thu Apr 07, 2011 5:06 pm
Posts: 45
Quote:
Yes, but the weight difference is negligible and front shifting is excellent. I have the 26-38 on my Tallboy and Highball and love it. In fact, I put a 24t on my Tallboy and it works great for lots of climbing on long rides. I find that I spin the easier gears better, have more balance at slow speed, have less cramps and more endurance with the 24t. For perspective, I am 6'1", 170 and won my cat 2 age group (33-34) last weekend at sea otter....this is not coming from a heavy, slow or weak rider that just can't push bigger gears.


How's the shifting from the 24 to the 38? Thinking of doing a modified 2x9, and that gearing looks promising, as long as the jump isn't too big for a standard 3x front derailluer to handle.


Top
   
Posted: Mon Apr 30, 2012 8:54 pm 


Top
   
 
PostPosted: Tue May 01, 2012 1:49 am 
Offline

Joined: Wed Oct 26, 2011 4:07 pm
Posts: 47
Short answer: I'd recommend the SRAM XX 26/39.

Some things to note: the XX crank accepts 26/39 or 28/42 only and the rings start from a slightly thinner 6mm blank to save weight, since the crank's integrated spider provides the rings with extra stiffness and keeps things lighter than a swappable spider system. It's a great lightweight system that proven by the top racers, which a lack of mechanical faults, providing similar gearing range as a triple, but lighter. Another thing to note is how some full suspension frame designs may not be optimized for it, as far as anti-squat figures go, with the 26/39 equipped FS bike having less anti-squat than if equipped with a triple crankset.

More in-depth answer: From an engineering perspective, the 26/39 X Glide design is better designed. SRAM made the rings more affordable & lightweight, yet stiffer, and with consistent shifting that's no worse than Shimano. They accomplished this with their proprietary BCD, making the BCD as widely spaced as possible, allowing them to cut down on material on the ring, the minimal amount needed to guide the chain, yet retain stiffness. The 2:3 tooth ratio is kind of gimmicky, providing SRAM with numerous timing opportunities with fixed spacing, where they can place pins, ramps, and teeth shape profiling to give you shift points at specific parts of your stroke, such as when the crankarms are at 2 o'clock and 8 o'clock. Shimano does the same, but picked another ratio that puts those shift points in areas they find more ideal, which people may prefer over SRAM.

Not completely sure how Shimano does things, but their 26/38 uses a diff BCD than their 28/40 and 30/42, with the latter 2 being proprietary double chainring only BCD (88 bcd?). Looking at the 26/38, the 38t ring looks like an eyesore, with so much material on it. Shimano chainrings typically have far more tech invested in them, but have a high price tag as well. Shimano typically goes their own route, not liking to license existing standards (except UST), but I wonder what their basis was behind their BCD choice here. The ended up with a big ring that needs a lot of tech in it to retain stiffness, due to its anchor point being so far from the teeth, not to mention MTB cranks only having 4 arms instead of 5. To me, all the material showing on the 26/38 Shimano chainring set's big ring is an eyesore, despite their attempts of hiding it with their contrasting two-tone color scheme.

Mixing and matching random chainrings together isn't going to give you good shifting performance, as the ramps and teeth shaping won't sync with each other. I've noted that Truvativ Tru-shift rings in the same teeth count won't necessarily match up with the other rings on my Noir crankset that I had before my XX crankset, being really bad at downshifts, holding the chain and then dumping the chain down hard. Chainrings are where most of your shifting performance is (not derailleurs, cables, and/or shifters), so you need to invest a lot in it. Drivetrain stiffness, including the frame, delivers precision/accuracy (no ghost shifts/mis-shifts), and teeth shaping and ramps and contoured chains determine the shifting quickness, smoothness, and quietness.

As for anti-squat, too little anti-squat is typically less efficient than too much anti-squat, and typically has less behaved suspension habits. Lower anti-squat designs typically have super active and sensitive rear ends, which higher anti-squat designs are more controlled/metered. The sweet spot for anti-squat is arguable, but I personally prefer Sotto group's take on it, over DW's take on it. DW's design is good, as it has good IC and wheel path profiles, allows for a stiff frame due to a fully triangulated rear end, but it's has a weight penalty over a single pivot or 4-bar system, but the similar things can be said for Maestro, VPP, and the other dual short link designs--just different ways to do the same thing. All designs are viable, but which is best, yet lightweight, and efficient? Specialized has proven itself with it's FSR + Brain combo, with the brain making it super efficient and the 4-bar design making it super active and sensitive, yet being lightweight and sufficiently stiff. Check out the Linkage program or see if your bike has been analyzed at linkagedesign.blogspot.com to find out more about anti-squat, which is more important for XC racers.


Top
   
Display posts from previous:  Sort by  
Post new topic  Reply to topic  [ 10 posts ] 

All times are UTC+01:00


Who is online

Users browsing this forum: No registered users and 9 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Limited