sram xx1/x01 in 650b-er

Discuss light weight issues concerning mountain bikes & parts.

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bikemaniack
Posts: 331
Joined: Thu Jul 16, 2009 9:33 pm

by bikemaniack

Hi everyone

I would like to know, how many of you using the 1x11 gearing with 27,5 wheels bikes. How big front chainring are you using,is 38t front chainring is enough in terain/road ride,and more of your experience.

jeffreyj
Posts: 25
Joined: Mon Nov 03, 2014 11:50 pm
Location: Florida

by jeffreyj

I use it on my Santa Cruz 5010c and it works GREAT with the 30t chainring (11.5k/25.5lbs with pedals and dropper!). I'd say the largest you'd likely want to use is a 32t.

by Weenie


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bikemaniack
Posts: 331
Joined: Thu Jul 16, 2009 9:33 pm

by bikemaniack

how fast you can ride on flat part with 32t on front??

prodigy
Posts: 115
Joined: Sat Nov 10, 2007 4:10 pm
Location: EU

by prodigy

I have the same configuration and on flat at 40-45 kph I spin out.

bikemaniack
Posts: 331
Joined: Thu Jul 16, 2009 9:33 pm

by bikemaniack

somebodys with 32t on front in 29ers have problem on road flat sections at 45km/h they have to pedaling very fast. I think better will be 36t

jeffreyj
Posts: 25
Joined: Mon Nov 03, 2014 11:50 pm
Location: Florida

by jeffreyj

Was actually going to say on my 29er (has a 32t right now) I hit 50kmh (31mph) on a flat road the other day. Was pedaling at a fairly moderate ~70 cadence, and easily could have done 57kmh+ (36mph+) if my legs had some more umph (or a downhill section!). Don't think I personally would be happy with a 36t when climbing...but you may have better luck/legs?

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mattyNor
Posts: 337
Joined: Wed Mar 19, 2014 3:18 pm

by mattyNor

Who cares how fast your MOUNTAIN bike is on a ROAD.......

grover
Posts: 1302
Joined: Mon Jul 26, 2004 1:06 pm

by grover

I run a 34t on my 29" hardtail.
I run a 32t on my 27.5" 140mm duallie (although is has 2.4" tyres which makes wheel diameter similar to my 29" hardtail with 2.2" tyres).

If I were to use a 27.5" XC bike I'd run 36 or 38 course dependent.

Nino runs a 38t on his 27.5"...although he's a monster...and his 27.5" is rumoured to be more like 28.25" (ETRTO marked '600' which is inbetween 27.5" and 29" standard).

I'd suggest using a gear calculator like http://www.bikecalc.com/speed_at_cadence
Plug in tyre size and width, a few chainring sizes and the min and max cog size to look at bottom and top speed for the cadence range you like.

Eg. 27.5x2.2 tyre 32x10 at 110 cadence is 46km/h, 36x10 at 110 cadence is 52km/h.

jeffreyj
Posts: 25
Joined: Mon Nov 03, 2014 11:50 pm
Location: Florida

by jeffreyj

mattyNor wrote:Who cares how fast your MOUNTAIN bike is on a ROAD.......


100% agreed. My example was just the short 1/4 mile road to the trail head where I wanted to see what she could do on a flat road. There is no way in H$*# I could climb comfortably with anything over a 32t, but again, I'm no monster, just a weekend warrior. Even on a downhill, I wouldn't need that kind of gearing as my feet typically stay at 3 and 9 while descending.

drider85
Posts: 183
Joined: Fri Apr 13, 2007 4:53 pm

by drider85

I raced Cat1 with 36T with 10 speed 11-36 this whole season on a 9.3kg 27.5". If I would go to 11 speed I would likely go up to 38.

skyfire1202
Posts: 193
Joined: Wed Apr 16, 2008 7:43 am
Location: Sapporo City, Hokkaido, Japan
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by skyfire1202

I just got back to racing this year, but unfortunately, I didn't have much time for training, but got back to elite level on my second race. I raced 26", hardtail 6 years ago with 42/29 x 11/32 or 11/34 depending on terrain, full-sus 26" this year with XX1 and prepared 38T and 36T front, but I didn't feel the need for the 38T maybe because I lack training too, so maybe with a 27.5", 36T would be a good choice if you plan to go off-roads too, unless you have more power for uphills and can climb with a 38T on XC race courses. If only for road rides, 38T would be good for those long smooth downhills.
Last edited by skyfire1202 on Fri Nov 14, 2014 5:04 am, edited 1 time in total.

boots2000
Posts: 1393
Joined: Mon Oct 15, 2007 9:28 pm

by boots2000

I run a 30 tooth on my Santa Cruz 5010 with XX1- but it depends entirely on where you live, terrain that you ride, and riding style.
I need the 30/42 low gear for some of the extended climbs that I have. I need this more to be able to ride at a tempo than I like. I could possibly ride a 32 if I wanted to grind or be forced into a maximal effort.
I have a brand new 36 tooth xx1 ring if that is of interest. Let me know- I will sell it cheap.

bikemaniack
Posts: 331
Joined: Thu Jul 16, 2009 9:33 pm

by bikemaniack

When i was talking about road sections,i was thinking about first few kilometers of bike marathons on flat terain. Now i see that chosing front ring is like a test and it may be difficult to buy at first time.

prodigy
Posts: 115
Joined: Sat Nov 10, 2007 4:10 pm
Location: EU

by prodigy

Depending on how the race starts, but it happened to me that I spun out on my 29er running 38x11. Only for a breif moment and it was on fairly flat surface, which wasn't going downhill almost at all.
I would start with 32t front ring and go from there.

grover
Posts: 1302
Joined: Mon Jul 26, 2004 1:06 pm

by grover

Just want to point out that those pointing to experience with an 11 tooth cog is quite irrelevent. XX1 has a 10 tooth cog. That is a 10% bigger gear. So a 38x10 would be a 42x11. That used to be my top gear on my 26" hardtail running 2x9 back when that was the 'ideal' drivetrain. Now on a 29" hardtail with the wheelsize to account for...38x10 on a 29er is like a 44x11 on a 26" hardtail. Yes you'll probably spin out on a fast road descent but for XCO racing it's plenty.

Are you happy with your current gear spread? What wheel size do you use now? What gear ratios do you use now? Plug them into the gear calculator and figure out what speed you can go at what cadence. Then plug in 27.5 wheel size and an xx1 cassette range and various chainring sizes. Choose the ring size that most closely matches up to the speed range that your current setup provides.

by Weenie


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