29er Gearing Mindf*ck

[Ratty]

Indeed. I think I might have eventually faded into the mindset that different bikes suite different courses. I'm building the 29'er for Trans Baviaans and courses where a 29e'r might be better. My 26'er won't be retired and will probably be used most of the time still. My 'Rida eats 29'ers for breakfast. But, like on Last year's Trans Baviaans - when I'm spinning my moer out on slight downhills, the bloody 29'ers just roll past you and you can do nothing but watch in awe.

 

lol, I was also one of them. Also said I wouldn't retire my 26'er and would use it for places like Tokai, Jonkers etc and use the 29er for Knysna, K2C etc. 3 weeks in and I have fallen in love with my HT 29er and am seriously considering selling the 26'er DS.

[Stig]

Depends on the terrain you are riding and what you weigh. Gear ratios is all about power to weight ratios.

Less than 85kgs 2x10 with 26/39 ratio is fine for most marathon/ trail riding.cassette 11/36.

More than 85kgs 2 x 10 better with 24/38 with 11/36 cassette.

Remember you have wheels that are 10% larger in diam than before. So your final drive ratio is automatically larger.

[VincentBikes]

If you are not a serious weight weenie put a 3x10 on. There are some climbs out there where you will need the 22-36 to get up them as the 29" wheel circumference is much longer than a 26". Remember it is all about final drive ratio which includes the wheel circumferece. Or unless you have a 9kg full carbon 29er or something which you can power up a climb.

[Azonic]

I weigh 77-78kg at the moment, and as someone asked whether the person is a spinner or a grinder, I'm a grinder. Well, to be honest this thread has not really cleared anything up! I'm still in two minds. As most people I'm able to go up Bergplaas in middle ring on a 26'er, which is a 32t, and I think at the time I had a 34t at the back. So surely a 28t x 36t on a 29'er must be fine?

[Bike Mob]

yes you will be fine with a 28/36

[Tankman]

 

There is a nice crankset on CRC that I'm after, but its "meant" for a 9 speed system. If I have a 10 speed cassette and chain (I guess the chain is the thing here), will that chain run over the rings of that "9 speed" crankset? I've heard guys put 10s rings on, but stock? Will it work? I'm guessing a 9 speed crankset - the rings are a ballhair further appart to give space for the slightly fatter 9 speed chain. So that being said, with a 10s chain being marginally narrower, lets say you are in big ring and you click once down to middle ring (if you had a 3 ring crankset). The front jockey will have to move a little bit more before it starts touching the chain to start moving it to the smaller ring. AND, the middle ring is also fractionatly further away from the big ring than on a "10 speed" crankset. Will that shift (work)?

 

You can use a 9spd chain/groupset on a 10spd crank no problem. The same for 10 & 11 speed.

 

But using a 9spd chain on 11spd crank won't gel!

[NINER_boy]

I weigh 77-78kg at the moment, and as someone asked whether the person is a spinner or a grinder, I'm a grinder. Well, to be honest this thread has not really cleared anything up! I'm still in two minds. As most people I'm able to go up Bergplaas in middle ring on a 26'er, which is a 32t, and I think at the time I had a 34t at the back. So surely a 28t x 36t on a 29'er must be fine?

 

Dude,

This is going to be a costly exercise for you!!!

I have a 29er, and so do most of the other guys commenting here.

 

The answer has been given to you:

26/39 with a 11/36 cassette.

 

Done

[IronTree]

Ok right, so you saying you're running a 10s cassette and chain, on a XT 770 crankset which is 9 speed... and its fine?

 

11/36 10 Spd Cassette, 10Spd XT Chain and the same crank, Runs fine, did a bit of research before hand, were a few minor concerns regarding the spacing between blades which might make the setting of the derailleur a bit fine, but I have got it going perfectly on a 3 x 10. Given I don't do the Big Big or small small combos deliberatley....

[sometime]

I weigh 77-78kg at the moment, and as someone asked whether the person is a spinner or a grinder, I'm a grinder. Well, to be honest this thread has not really cleared anything up! I'm still in two minds. As most people I'm able to go up Bergplaas in middle ring on a 26'er, which is a 32t, and I think at the time I had a 34t at the back. So surely a 28t x 36t on a 29'er must be fine?

 

It's not about what gear is good for you when you ride Bergplaas or what gear works for you 98% of the time. If that was the case then yes possibly a 28x36 is as low as you need to go. What you need to plan for is having the right gear available to you for that 5% of your riding when you're just not feeling too strong, or you're at the end of a 5 hour marathon and you're confronted with a tough, steep 5 km grind to the finish, or when you've hit the wall and just need to get home without having to walk.

 

In that case (unless you're a pro - but then you wouldn't be asking this question) you need to be able to drop into a lower gear. In these 5% of cases a 28 is not low enough. In my experience a 26t is not low enough either. I'm 85 kg and for me a 24/38 would be the best combination. A 24/34 is there for those few occassions when you really need it and a 38/11 on a 29er is long enough to allow you to do 50km/h at 100rpm cadence. Any sustained speed above 50km/h on an MTB is on a downhill which means it's time get your head down and let gravity do the rest.

[Azonic]

Dude,

This is going to be a costly exercise for you!!!

I have a 29er, and so do most of the other guys commenting here.

 

The answer has been given to you:

26/39 with a 11/36 cassette.

 

Done

 

China, my cart on CRC is sitting on R3601 already... I know its going to hurt.

 

I would do 39x26... but find me that in a 180mm length? Hen's teeth...

 

That being said, at a given RPM, does a 39x11 roll faster on a 29'er compared to a 42x11 on a 26'er ?

[Azonic]

...and a 38/11 on a 29er is long enough to allow you to do 50km/h at 100rpm cadence. Any sustained speed above 50km/h on an MTB is on a downhill which means it's time get your head down and let gravity do the rest.

 

That pretty much answers my previous question... If you can do that on a 38t, a 39t is a given. 42t might be too tall.

Edited July 4, 2012 by Azonic

[IronTree]

China, my cart on CRC is sitting on R3601 already... I know its going to hurt.

 

I would do 39x26... but find me that in a 180mm length? Hen's teeth...

 

That being said, at a given RPM, does a 39x11 roll faster on a 29'er compared to a 42x11 on a 26'er ?

 

Azonic, this might be a pain to do, but would give you the answers you seek, http://sheldonbrown.com/gears/, plug in your crank length ,cassette specs and see the results.... ?

[Azonic]

Azonic, this might be a pain to do, but would give you the answers you seek, http://sheldonbrown.com/gears/, plug in your crank length ,cassette specs and see the results.... ?

 

I did that earlier today. The lowest gear on a 28x36 combo is slightly lighter than a 22x28 combo. BUT, given the wheel size, you have to add about 15% onto that, making it slightly harder than the 22x28 combo...

[sometime]

China, my cart on CRC is sitting on R3601 already... I know its going to hurt.

 

I would do 39x26... but find me that in a 180mm length? Hen's teeth...

 

That being said, at a given RPM, does a 39x11 roll faster on a 29'er compared to a 42x11 on a 26'er ?

 

Yes

 

@100rpm

 

26er 42/11 47.5 km/h

29er 39/11 49.2 km/h

[Azonic]

You can use a 9spd chain/groupset on a 10spd crank no problem. The same for 10 & 11 speed.

 

But using a 9spd chain on 11spd crank won't gel!

 

Shot, but I asked the opposite... 10 speed everything... on a 9s crank.

[NINER_boy]

China, my cart on CRC is sitting on R3601 already... I know its going to hurt.

 

 

 

I would do 39x26... but find me that in a 180mm length? Hen's teeth...

 

 

That being said, at a given RPM, does a 39x11 roll faster on a 29'er compared to a 42x11 on a 26'er ?

 

 

By asking advice, and TAKING it, it WILL save you lots of $'s.

PS, you do not need to waste money, asking advice and taking it WILL save you $'s.

 

180mm cranks, E-Thirteen make some nice ones, on CRC.

 

29er rolls faster than 26" bike as spec; YES

Edited July 4, 2012 by NINER_boy