Bmx Crank on Dirt Jump MTB

PB Forum :: Dirt Jumping & Street
Bmx Crank on Dirt Jump MTB
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flag Emperor3415
Posted: Dec 19, 2016 at 19:13 Quote
Does anyone here uses BMX cranks on their Dirt Jump Mountain bikes? If so, is it possible? Thanks Smile
flag walkingtall76
Posted: Dec 19, 2016 at 23:31 Quote
Well its not as simple as "yes and yes". What BB do you have?? Seems you're asking this im gonna guess standard mtb cranks with a euro BB at 68mm? So you would need the appropriate BB in order to fit Bmx cranks.

Not difficult to do... and can be done. Octane one make a euro BB to fit the common 19mm bmx cranks.
flag Emperor3415
Posted: Dec 20, 2016 at 6:04 Quote
But what are the advantages of using BMX cranks in MTB?
flag Ajarm19
Posted: Dec 20, 2016 at 9:46 Quote
for dirt jumping it's really preference some people like the feel of mountain bike pranks because theyre a little flexier and sometimes lighter others like the stiffness of the bmx its all preference
flag SolarLonsky
Posted: Dec 20, 2016 at 9:55 Quote
You need to make sure that the spindle is long enough
flag cmc4130
Posted: Dec 20, 2016 at 10:52 Quote
Black Market Mob with Profile BMX cranks, Profile 6 inch (not 5.75"!!!!) 19mm chromoly spindle, Odyssey Euro internal bottom bracket, and 53mm tube spacer (because the bottom bracket shell is 73mm wide instead of 68mm like on all bmx and some DJ frames).



BMX or MTB cranks?
https://www.pinkbike.com/forum/listcomments/?threadid=188243

What crankset will fit my frame?
https://www.pinkbike.com/forum/listcomments/?threadid=174145&pagenum=2

Chainstay width on Black Market Mob. 73mm wide bottom bracket shell.
photo

Odyssey bmx Euro bottom bracket on a Black Market Mob
photo

Chainstay width on a Liquid Feedback 24" BMX (you can see it's narrower than the MTB-DJ frame).
photo
flag walkingtall76
Posted: Dec 20, 2016 at 12:14 Quote
Ajarm19 wrote:
for dirt jumping it's really preference some people like the feel of mountain bike pranks because theyre a little flexier and sometimes lighter others like the stiffness of the bmx its all preference


??? Actually chro-mo bmx cranks have more flex than stiffer Alloy mtb cranks! Weight is variable
flag foreverfreeriding
Posted: Dec 20, 2016 at 12:34 Quote
If you have a spanish bottom bracket, those are made for bmx cranks and depending on the width any bmx cranks will work. However octane one makes a longer spindle crank to get a good chain line for dirtjumpers (26 inch).

If you have euro its pretty easy. Grab yourself a profile external euro bottom bracket in the correct spindle diameter you wish to run.
https://www.danscomp.com/products/456019/Profile_External_Euro_BB_Kit.html

I would then suggest using a longer spindle crank such as the ones octane one produce.

I currently run the aforementioned profile BB with 2 pcs pro octane one cranks and it works beautifully.

Remember if you want to run bmx cranks you will need a bmx sprocket, chain and rear driver on your hub. Its ALLOT cheaper to get a pair of shimano zee cranks that come with a botom bracket, a cheap single speed chain and a single speed conversion kit for your rear hub.

I hope this helps.
flag SolarLonsky
Posted: Dec 20, 2016 at 12:57 Quote
You don't need a bmx style driver, a regular single speed conversion will work fine.
flag walkingtall76
Posted: Dec 20, 2016 at 13:02 Quote
foreverfreeriding wrote:
If you have a spanish bottom bracket, those are made for bmx cranks and depending on the width any bmx cranks will work. However octane one makes a longer spindle crank to get a good chain line for dirtjumpers (26 inch).

If you have euro its pretty easy. Grab yourself a profile external euro bottom bracket in the correct spindle diameter you wish to run.
https://www.danscomp.com/products/456019/Profile_External_Euro_BB_Kit.html

I would then suggest using a longer spindle crank such as the ones octane one produce.

I currently run the aforementioned profile BB with 2 pcs pro octane one cranks and it works beautifully.

Remember if you want to run bmx cranks you will need a bmx sprocket, chain and rear driver on your hub. Its ALLOT cheaper to get a pair of shimano zee cranks that come with a botom bracket, a cheap single speed chain and a single speed conversion kit for your rear hub.

I hope this helps.



He's only asking if he can use BMX cranks on his DJ... he hasn't suggested its a geared MTB
flag cmc4130
Posted: Dec 20, 2016 at 14:26 Quote
walkingtall76 wrote:
Ajarm19 wrote:
for dirt jumping it's really preference some people like the feel of mountain bike pranks because theyre a little flexier and sometimes lighter others like the stiffness of the bmx its all preference


??? Actually chro-mo bmx cranks have more flex than stiffer Alloy mtb cranks! Weight is variable

Seems like it depends a lot on what cranks we're talking about....

I tried these FSA cranks on my 4x bike and they were horribly flexy--like I could flex them just pressing on the pedal with my hand.
Unsecure image, only https images allowed: http://i255.photobucket.com/albums/hh138/upsetbmx/FSAcrankwithMRPchainguide_zps81f83f41.jpg
I returned them, and got these Truvativ Holzfeller cranks. Definitely stiffer than FSA... but still notice a little flex.
Unsecure image, only https images allowed: http://i255.photobucket.com/albums/hh138/upsetbmx/Holz1_zpse7761b7b.jpghttps://www.pinkbike.com/forum/listcomments/?threadid=144510

My chromoly bmx Profile cranks (pictured above) are definitely stiffer.

I've also had Primo Powerbite bmx cranks. They're aluminum, and yeah, they're pretty stiff.

Unsecure image, only https images allowed: http://i95.photobucket.com/albums/l124/opengroundpark/PRIMO/IMG_9652_zpsobqpghsy.jpg
Shimano Saint cranks are also known for being stiff.
https://www.pinkbike.com/product/shimano/Saint-Crankset/
flag Stanley-w
Posted: Dec 20, 2016 at 14:32 Quote
Ajarm19 wrote:
for dirt jumping it's really preference some people like the feel of mountain bike pranks because theyre a little flexier and sometimes lighter others like the stiffness of the bmx its all preference

Actually I feel the exact opposite. Might have something to do with the fact that I have only had beefy mtb cranks and shitty bmx cranks before.

To me the main considerations are 1: what bb does your frame have, if you havent have a choice of frame then consider: 2: difficulty to source, to me mtb cranks wins hands down, there are far fewer choices, more transparent prices and information such as weight and etc etc. 3: what sort of gear ratio you are going to run. usually mtb chain rings on a single ring crank (such as a zee) cannot go under 32 teeth (some brands make 30t offset rings), so if you are running a bmx style rear hub with 9 teeth, it is going to be a bit too hard to pedal.

Just my 2 cents, might have made some mistakes here and there
flag cmc4130
Posted: Dec 20, 2016 at 15:36 Quote
Stanley-w wrote:
. . what sort of gear ratio you are going to run. usually mtb chain rings on a single ring crank (such as a zee) cannot go under 32 teeth (some brands make 30t offset rings), so if you are running a bmx style rear hub with 9 teeth, it is going to be a bit too hard to pedal.
. . . .

Good point.

Unsecure image, only https images allowed: http://www.cycleexif.com/wp-content/uploads/2013/03/blackmarket-bikes-edit-13.jpg

Unsecure image, only https images allowed: http://p.vitalmtb.com/photos/users/20312/setup_checks/19338/photos/3222/s1600_p5pb8575083.jpg?1355032989 size=m align=c][/P]

photo
flag walkingtall76
Posted: Dec 20, 2016 at 16:17 Quote
Stanley-w wrote:
Ajarm19 wrote:
for dirt jumping it's really preference some people like the feel of mountain bike pranks because theyre a little flexier and sometimes lighter others like the stiffness of the bmx its all preference

Actually I feel the exact opposite. Might have something to do with the fact that I have only had beefy mtb cranks and shitty bmx cranks before.

To me the main considerations are 1: what bb does your frame have, if you havent have a choice of frame then consider: 2: difficulty to source, to me mtb cranks wins hands down, there are far fewer choices, more transparent prices and information such as weight and etc etc. 3: what sort of gear ratio you are going to run. usually mtb chain rings on a single ring crank (such as a zee) cannot go under 32 teeth (some brands make 30t offset rings), so if you are running a bmx style rear hub with 9 teeth, it is going to be a bit too hard to pedal.

Just my 2 cents, might have made some mistakes here and there


Yes- same, for me as mentioned chromo cranks are more forgiving. However, also I have had stiff cranks like Saint.

As for the 9t rear I don't know why that's important information?? He wants to know if he can use bmx cranks.. so therfore he's obviously already running mtb cranks. So his setup as is- is obviously/probably not geared for a 9t rear if he has MTB cranks- id say 13 or 14t. If he replaces for a bmx crank he'll be fine with a 30 or 28t front ring...
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