# BMX cranks on a MTB?



## The_Mickstar (Apr 22, 2008)

I like the look of the small chainwheel/small cog setup, and the tubular crankarms. I also like the fact that the setup should be more than strong enough to handle anything an aggressive 195lb XC rider is likely to throw at it.

I don't love the weight, but I can live with it. I'm also not too sure about how well-sealed the BB bearings are.

I'm currently running a 32x18 setup on my 2010 Kona Unit with a 180mm FSA V-Drive SS crankset and the stock MegaEXO BB. The frame has a 73mm English thread BB. Since I'd like a slightly harder gear, I'm thinking of moving to a 26x14 BMX setup. But, I'm not sure how to proceed, or even if it's wise.

1. What, specifically, do I need BB-wise? From my research, I believe I need a "Euro" BB. But, I'm not sure about axle length or axle diameter. (I think I need a 6", 19mm axle, right?) My main concern, though, is that BMX bikes/parts are not necessarily designed to see the amount of mud, snow and water that a MTB sees on a typical ride. How well-sealed are these BBs? How "high maintenance" are they? 

2. I see that most of the 3-pc BMX cranks use 19mm, 48-spline axles. But, some chainwheels use a 48-spline drive, while others use a bolt. Advantages/disadvantages of each?

3. Specific recommendations for components? I'm looking to spend as little as possible while still having a reliable, low maintenance setup. And, I do require 180mm+ crank length.

4. Anything else I should be aware of?

Thanks.

Steve


----------



## wu501 (Aug 12, 2010)

Profile makes 3 piece cranks and bottom brackets to fit mountain bikes. There was a similar thread a while back if you do a little searching. I will try to find it to you.


----------



## wu501 (Aug 12, 2010)

some good info here and links for the profile cranks I mentioned:

http://forums.mtbr.com/showthread.php?t=660807&highlight=bmx+cranks


----------



## sasquatch rides a SS (Dec 27, 2010)

I have tried the same thing and ran into alot of issues. First off you'll probably need a 7" or longer spindle, and you want to make sure that the euro bb will thread into the frame. You will need a wide spindle because mountain bikes have wider chainstays for wide tire clearance whereas bmx bikes aren't as wide. But if you can get a wide enough spindle and get the bb threaded in you will be good to go. It's a great idea to run bmx stuff on single speeds but it will be more expensive. Bmx parts in my opinion are very pricy for anything that's somewhat good. They're strong, but heavy and expensive. My only suggestion is to go to a local shop where you can see if the parts will fit before you buy them. Even if you measure you may run into something that ruins everything. Plus the shop may have some ideas on what works better with certain parts and they can compare prices and specs quickly. Hope that helps, if you've got any questions just ask.


----------



## 1SPD (Apr 25, 2010)

I thought about going this route myself after having Profile cranks for years on all my bmx bikes. But I am glad I went the route that I did and picked up a used XTR M960 crank and got it modified to be SS specific. It has to weigh have the amount of the Profiles, bolts right up, cost me about half of what the Profile set up would have run, have not a single problem with it what so ever. Stiff, strong, light, CHEAP! A rare collection of qualities imo.


----------



## KodiakBear (Feb 6, 2010)

I did this on my fixed-gear road bike with a set of profiles. Expensive, but extremely durable and does not creak (after two years of riding). I use a splinded sprocket as well; not having to worry about bolts is very nice, since single bolt sprockets WILL wear out (but most sprockets have 4-5 holes, so it can be rotated). Profile makes a 4 and 5 bolt splined spider as well, but this defeats the defeats the purpose of not having chainring bolts. If you can find a long spindle (I'm not sure sizes) to accommodate for the wider chainstays and bb shell, it shouldn't be a problem, though you may need a spacer or two. You'll need a Euro BMX bb; most come without a spindle, though FSA makes one that comes with a spindle but was out of stock just about everywhere. I use an odyssey and have no complaints, though keep in mind its meant for tricking, not XC. 

That being said, I wouldn't do this on my XC bike.


----------



## jeffgothro (Mar 10, 2007)

Profiles are an excellent choice, been using them since the mid-late 1980's on bmx, never a problem. If it doesn't work for you, you might try Shimano Saints, that's what I run...it to is quite light for a F/R-D/H-D/J crank, and plenty strong, bearings are smoothe as butter.


----------



## nuck_chorris (Jun 6, 2008)

ive used redlines square taper 5 bolt racing bmx crank set with no problem , just make sure to get the right BB


----------



## bad mechanic (Jun 21, 2006)

They're just a lot of unneeded weight in my opinion. They can do anything you can with BMX cranks for generally lighter and cheaper with MTB specific gear.


----------



## Mr.Bee (Aug 22, 2010)

I use them and they just feel safe you can hammer the crap out of them.


----------



## ISuckAtRiding (Jul 7, 2006)

bad mechanic said:


> They're just a lot of unneeded weight in my opinion. They can do anything you can with BMX cranks for generally lighter and cheaper with MTB specific gear.


i agree.

and if you like the look of the small chainrings, there are plenty of mtb cranks out there that have a removable spider, allowing you to go pretty damn small.


----------



## Mr.Bee (Aug 22, 2010)

Once you have tried them it's hard to go back I believe it's the strongest crank you can put on your bike for the price.


----------



## bad mechanic (Jun 21, 2006)

Mr.Bee said:


> Once you have tried them it's hard to go back I believe it's the strongest crank you can put on your bike for the price.


You're not going to break an XT or LX crankset. You're just not.


----------



## sasquatch rides a SS (Dec 27, 2010)

bad mechanic said:


> You're not going to break an XT or LX crankset. You're just not.


You can't do many crank grinds with an XT or LX crankset though!  I was going to use a BMX crankset for the cleaner look of it and the ability to have microdrive for clearance, but never did.


----------



## byknuts (Aug 9, 2008)

my surly 1x1 has pretty wide chainstays and the profiles clear them just fine with the standard spindle.
no need for an extra long spindle for me, but if you're running something silly like 1" thick alloy chainstays? then maybe it might be something to look at before buying.
profile arms are THICK where the pedals thread in... so your Q-factor (if you care about such things) is hard to bring in towards the centre of the bike. 
not that you really CAN without buying a new spindle...


----------



## wjphillips (Oct 13, 2008)

bad mechanic said:


> You're not going to break an XT or LX crankset. You're just not.


+1 on that!

Get an XTR crank. They are totally bomb proof and light.


----------



## nnoo (Apr 2, 2011)

I'm curious, are you guys able to get away with using a 6" spindle? What spindle lengths are you using?


----------



## Gritter (Dec 21, 2010)

nnoo said:


> I'm curious, are you guys able to get away with using a 6" spindle? What spindle lengths are you using?


Yeah, I installed some chrome Profile Racing (175mm) cranks on a Soma 4one5 that had a 68mm BB. I ordered their MTB kit: http://profileracing.com/profileracing/estore/product.php?productId=43&categoryId=8

It came with the 6" spindle and worked wonderfully!

The BB bearings are so silky smooth, and spin a lot more easily and longer than my Chris King BB.

Aesthetically, the Profile Cranks look amazing!

As far as performance - very awesome!

A little more confusing to install than "normal" forged cranks, but after you do it once, it all makes sense - (you can message me, if you run into any issues, and I'll try to help...)

That kit, direct from Profile Racing, linked above - was all I needed - you have the choice to go with a spider, or a regular BMX style chainring. Even though the Chainring is aluminum, it's stout and burly as all get out.

The chainring was also more "true" than my Surly Stainless Ring - it actually seems to be higher quality - and I think all the Profile Stuff is still made in the U.S.A. (if that matters to ya).

Edit - I checked, and all their stuff is made in the U.S.A. - except their saddles, which are made in Taiwan.


----------



## blunderbuss (Jan 11, 2004)

Yep, Profile parts are made in St. Petersburg, FL.


----------



## Yeti Clyde (Dec 12, 2004)

bad mechanic said:


> They're just a lot of unneeded weight in my opinion. They can do anything you can with BMX cranks for generally lighter and cheaper with MTB specific gear.


They do add alot of extra weight, but are bullet proof...

I was going to go with Profiles but went with the flights to stay with the Redline theme...

Great for that BMX look and feel....


----------



## Gritter (Dec 21, 2010)

Yeti Clyde said:


> They do add alot of extra weight, but are bullet proof...
> 
> I was going to go with Profiles but went with the flights to stay with the Redline theme...
> 
> Great for that BMX look and feel....


As this picture shows... they look amazing :thumbsup: Love that imperial chainring too. Sick drivetrain, Breh.


----------



## proline69 (Apr 14, 2009)

Profiles on my Stout .


----------



## aTomOfAllTrades (Apr 22, 2010)

Like a few of the posts above, I used the standard 6" spindle with no issues in terms of spacing or spline engagement length on my Karate Monkey. The bearing spacer tubes supplied are both too long for that BB shell, but that's easy to remedy, and probably not all that necessary in the end.

As far as the merits of BMX cranks over traditional MTB cranks, yeah there is a good bit more weight, which will be deemed unnecessary because the vast majority of people will never break a normal MTB crankset. Ever. The rest is mostly aesthetic, though you could argue the "peace of mind" knowing that your cranks will survive the apocalypse, even if the rest of your bike won't 

The main reason I went with them is because I wanted 190mm arms and that's basically impossible to find in any off-the-shelf MTB crank. Profile makes a quality product.


----------



## PoorBehavior (Sep 1, 2005)

To each their own. I had a hard time finding something cheap, 180mm and durable at the same price when I put mine together. I don't mind the extra ounces, as a clyde I have found that heavier is better a lot of times. I am using the newer profile BB but that is only because I could not source the FSA Euro BB when I bought it. I have folded good aluminum chainrings, I ovaled a Surly SS ring on the first ride. Anything with four bolts I have damaged. This setup is also ultra stiff, more than any other crank I have used.


----------



## vaultbrad (Oct 17, 2007)

Oooo. Love the jab with profiles, Mr. Behavior.


----------



## STSBADL (Mar 16, 2011)

Profile is overrated IMHO


----------



## PoorBehavior (Sep 1, 2005)

STSBADL said:


> Profile is overrated IMHO


Thanks vaultbrad.

As far as profile, I can't argue. I got these arms because at the time they fit what I wanted, raw and 180mm. I would have used some nasty boy arms and been fine. At the time though the profiles were available and I could not find the FSA stuff. I did not feel like waiting. If I purchased today I would save myself +$100 and get the FSA arms and BB. I do have a 7" hollow spindle in there and I have put my Boone ring away. Replaced it with a red 28t chainwheel, forget the brand. Nice and thick and cheap.

Like I said, to each their own. If I did not destroy chainrings I might go another way but I really like how solid the whole thing feels when dialed in and BMX rings don't fold like the XC ones I used to use.


----------



## Bataivah (Feb 19, 2011)

If you only want a higher gear then would'nt it be easier to just change your ring and cog?


----------



## ADDam (Jun 7, 2008)

Check out this Atomlab setup...

http://www.atomlab.com/mtbdrivetrain.html


----------



## PoorBehavior (Sep 1, 2005)

ADDam said:


> Check out this Atomlab setup...
> 
> http://www.atomlab.com/mtbdrivetrain.html


Aebike has the black 180mm for $150, (just noticed that the chainwheel and spider are both $50, so it is really $200). Considering they use shimano compatable BB if they also use a standard bmx chainwheel setup I would consider those for a new build. I would not replace what I have for them them though. And the chainwheel looks proprietary, which limits your options. I like the idea but there are a few drawbacks depending on what you want.


----------



## Mr.P (Feb 8, 2005)

When I go to the BMX race track, I see about 50% of the racers on MTB cranks. 

P


----------



## Slow Eddie (Jun 13, 2007)

vaultbrad said:


> Oooo. Love the jab with profiles, Mr. Behavior.


And is that a bmx-splined Boone ring? Talk about rare....


----------



## PoorBehavior (Sep 1, 2005)

Slow Eddie said:


> And is that a bmx-splined Boone ring? Talk about rare....


Yes it is. Had it custom made, by Boone. Since I can't replace it I am scared to use it. Gorgeous though.


----------

