Technical Tuesday: Shimano XT Crank And Bottom Bracket Installation

Jul 27, 2010

by Mike Levy

Although installing a new crank and bottom bracket can look overwhelming, it's actually an easier job than you may expect. While the video below shows you how to install Shimano's new XT cranks, the process shares many of the same steps with other models and brands. There are actually only a few pieces to the system and it's pretty hard to get it wrong, but it's worth noting that other makes may require different assembly steps and different torque numbers. Before starting it is important to be sure that your bottom bracket threads are in excellent shape, if they're not you'll likely struggle to turn the cups in and there is a good chance that you will damage the threads on either the frame or the cups. Likewise, if your bottom bracket shell is not faced smoothly and evenly, your bearings may wear out prematurely. A lot of frames come faced from the factory, but if you are not sure it is worth taking your bike to your local shop for them to have a closer look. If you are hesitant to do this job on your own be sure to have your shop do it instead.

Tools needed: 5 mm allen key, flathead screwdriver, bottom bracket tool, and grease.

Watch the video to learn how to install Shimano's crank and bottom bracket:

Tech Tuesday - How to install Shimano Cranks

by spoiledgoods

Views: 84,570 Faves: 94 Comments: 16

A note on torque...

It is recommended to use a torque wrench on the majority of repairs, especially jobs like this, but the reality is that most home mechanics do not own one. If you are not using a torque wrench, use common sense when tightening anything. Shimano gives torque measurements for the bottom bracket cups, crank preload cap, and the left crankarm's pinch bolts that you can find in the video below. But don't fret if you lack a torque wrench, there is a simple method to estimate torque. Bicycles usually use in/lb (inch/pounds) when measuring torque, but I find it easier to convert this to ft/lb (foot/pounds) as it is simpler to estimate. The conversion is 12 in/lb = 1 ft/lb. This means that there is one pound of force at the end of a foot long bar. Now that we know this it becomes easier to estimate torque values. For example, Shimano recommends tightening this crankset's bottom bracket cups to 300 - 435 in/lb.. Do the math and you'll discover that this equals 25 - 36 ft/lb, meaning 25 - 36 pounds of force at the end of a foot long bar. Now that you know this, you can do the conversion for the rest of the torque values given in the video below. Happy math!

Shimano also has a great technical page with further instructions on any and all parts that they make.

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mikelevy
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39 Comments

iamamodel (Jul 27, 2010 at 7:04)

Cloverleaf is right that cross-threading is more likely than stripping the threads. In order to guarantee you have not cross-threaded, turn the cups in the opposite direction of the 'Tighten' arrow (printed on the cup). turn it until you feel the cup 'click' and the cup will move towards the BB shell. This means that the start of the thread on both the cup and the shell have passed each other and then you can start tightening the cup.

If you are not sure what I mean, get any screw-top jar and practice with that. These days I automatically turn every lid the wrong way until it clicks and then I start tightening.

iamamodel (Jul 27, 2010 at 6:56)

For those of you without torque wrenches (please note that I'm getting the torque settings off the top of my head, but the force reckonings I'm using are about right and are based on when I sue a torque wrench in the shop.

BB cups take 40nm, which for a weakling computer nerd like me and using a similar length tool as in the video, is all the force I can muster and when I hear my ligaments get tweaked I know I'm done.

The plastic cap takes barely anything - once the cranks have no lateral play give the cap a 1/8 to 1/4 turn and you'll be golden. Don't do it up tight.

The crank pinch bolts take 15nm(?) which is enough to start to bend a very long allen key or enough to put a serious dent in your thumb with a short allen ket. Make sue you swap back and forth between the two bolts until neither move. I use TWO allen keeys at the same time that are the same length, but that's just me.

Tryxt (Jul 27, 2010 at 0:41)

For those of us planning to do this for the first time, is it imperative to use a torque wrench? Is the BB and crank easily damageable if over/under torqued, or is it something that is easy to do with a little common sense? Thanks!

chilli06 (Jul 27, 2010 at 0:50)

Just use common sense, if your competent you will be fine, I was.

Terrafire (Jul 27, 2010 at 0:52)

Well, its your call, would you like to risk stripping your BB shell and ruining your frame? My dobermann forever a tramp bike? I think not.

cloverleaf (Jul 27, 2010 at 1:50)

Yes, a torque wrench is useful for this as well as many other assembly tasks on a bike. But not essential, as long as you use common sense. The biggest risk of damaging threads on a BB comes not from overtightening and instead cross threading as you start the cups into the frame. Take care with that (and of course get them the right way round) and you can get away with using either a normal socket handle or large wrench to tighten them up. Just take your time if it's your first attempt and be careful - with practice you learn to feel for the torque required.

kev-jones (Jul 27, 2010 at 2:49)

just to point out... i've not watched the video so he might tell you their, but a Race Face X-type BB installation is exactly the same, just the way the cranks are secured into it is slightly different

norm (Jul 27, 2010 at 8:50)

Easy install. You don't need a torque rench. 300+ inch pounds is pretty much over the max any one can apply with that version of the tool by park with out breaking their own hand (it has a very narrow edge and begins to hurt lol). The end cap for the crank arm is driven by a plastic wheel as shown on the end of the parks shimano bb/crank tool. You just need to turn till it becomes difficult then a 1/8 to a 1/2 turn further (varies from person to person). On a side note that plastic wheel will take some really strong hands to over tighten the end cap to the point of damaging it so don't be scared. also if the cranks don't spin smooth cause you may have over done the torque on the end cap just back it out in small 1/8 to a 1/16 of a turn increments till they do. once you completed all that take a standard Alan key and hold it in your hand so you have your thumb just over the bend, when you thumb is extended, and the rest of it kinda in the fold of your palm (closer to your thumb, you should get a feel for what i'm saying when you try this). I am dead serious with the last bit because it will allow you to apply enough pressure to attain the right torque but will make it difficult to over tighten the pinch bolts. and that's all there is to it. the only bolts that are easy to over tighten are the pinch bolts and they need quite of bit of torque to begin with.

On a little side note its not a 10 speed set of cranks, comes with triple rings and shimano list no 10 speed xt cranks and my xt's came in the same box as the xt's shown lol.

zoolander07 (Jul 27, 2010 at 10:04)

I'm pretty sure the 10-speed and 9-speed are the same (looks wise) but the 'Dyna-Sys' branding means its 10-speed in this case a little brand on the largest chainring. And of course the other changes they made for the 10 speed

nwthumbs (Jul 27, 2010 at 10:07)

The only difference is the chain rings width. Ten speed Shimano stuff will be out for 2011 hence why it is not on the website yet. Pinkbike got their hands on one because they are a tester/ advertiser and it just makes sense for Shimano to flow them a few sets

thedemo7rider (Jul 27, 2010 at 11:27)

is it the same or pretty close to the same thing on all cranks and bottom brackets

zoolander07 (Jul 27, 2010 at 15:34)

to be honest i don't know i was thinking to myself 'what truly makes a crank 10 speed compatible?'. like will the chainring width be that decisive in not being compatible with a 9 speed or a normal XT crank with a 10sp cassette?
ive read in other forums of people modifying their front derailleurs to run a 10sp rear and a normal 3x crank

norm (Jul 27, 2010 at 18:38)

never heard of the dyna-sys till you mentioned it. heard shimano had a 10 speed in the works didn't think it was out yet. but there is a difference in the rings. teeth width and all those different shift indexes on the inside of a chain ring are different from 9 speed. its like try putting a 9 speed mtb chain on a road 10 speed. would keep skipping gears in the cassette and would cause excessive wear on the chain and chain rings because of all the play.

you could do what you said you read about the 10speed rear with the triple ring front. its just unless you buy road rings that will fit your cranks or get a some of the new mtb 10 speed rings that are slowing coming out from different companies you will be going through chains and chain rings pretty quick cause of the extra play on the front. they would still have a good life span but if you used a chain stretch gauge you would find it wearing out probably as much as 25% to 35% percent faster depending on the rider.

nwthumbs (Jul 27, 2010 at 22:05)

well i knew about the differences i just didnt feel like going into details and gave u a "make a long story short" version

, as well it is ten speed specific(look at SRAM with the XX line) but yes chains for me even in 8 speed last like a month(i mash pedals i cant help it) so i see my self spending a shit load of cash on chains... (yay) just my two cents but do we REALLY need ten speed mountain bike cassettes? cause even on trail rides i only use like 4-5 gears? just my two cents

norm (Jul 28, 2010 at 8:26)

Oh i'm on board with the why do we need 10 speed mountain bike cassettes --> freaking stupid. just another way to make more money. "get ppl to upgrade to a system that wears faster" It seems like one giant scam not to mention how its already harder to find 9 speed stuff this year. Its like trying to find a medium or short cage sram x9 this year hasn't been easy. shops were having trouble ordering them and ones that had them shocked up only had the medium cage at best.

scwr (Jul 28, 2010 at 4:19)

can anybody explain to me how you can measure 25-36 pounds of force at the end of a foot long bar? how exactly do you know when you have enough or too much torque? Do the tools come with some sort of indicator to let you know when you have reached enough torque? how do i measure torque??

dirtydroog (Jul 28, 2010 at 5:06)

You need a torque wrench, they are expensive.

mikelevy Mod (Jul 28, 2010 at 8:59)

The "25-36 pounds of force" statement is just referring to the fact that it is easier to estimate that number than 300-435 in/lb.

seraph (Jul 28, 2010 at 11:25)

You can get a Park Tool TW-2 for about $65.

omnicell (Nov 8, 2011 at 20:57)

Great... some of us are more artist then Mechanic... What this means...>? In the artists mind , they would rather turn a car into a sculpture with tools, then to get it running... !!

Mechanics can be a bit intimidating simply because of the way ones temperament thinks..

Therefore, good, simple , to the point instructional videos can take the pain away and bring back the reality. This is one of those video's.

Im so glad for tech Tuesdays... I hate having someone else work on my bike... I HATE IT.......!!!!

Great Stuff... I love seeing a site like this take care of its own...

escapologist (Jul 27, 2010 at 10:10)

He seems to blink a lot! Probably the lighting on him is too bright! Give him some reflective goggles!

vaguehue (Oct 25, 2010 at 14:19)

Mwahahahaha 'c u next tuesday' priceless xD
Torque wrench is usefull anyway, one for shimano non-drive crank arm can be pretty small and fairly universal (up to 25Nm will do

sicsoma (Mar 23, 2012 at 18:11)

this is great but....i cannot stress enough how important it is to use anti-seize compound on the bottom bracket cup threads. that is, if you ever want to get your bb off again.

ScottTrepanierPhotography (Jul 27, 2010 at 7:33)

Funny how he doesn't use a torque wrench! or even show one as the required tool!

Terrafire (Jul 27, 2010 at 0:52)

Loving the new Pinkbike.com animation at the end.

luigi (Jul 27, 2010 at 1:09)

never knew this was so easy.

caiocrz (Jul 27, 2010 at 4:20)

how the hell do i know how much pounds...

jasonleebeer (Jul 27, 2010 at 8:25)

www.parktool.com/products/detail.asp?cat=13&item=TW-6
You can use a torque wrench. With the appropriate bottom bracket tool.
www.parktool.com/products/detail.asp?cat=25&item=BBT-19

masterk (Jul 27, 2010 at 0:45)

this easy as one two three buddy

masterk (Jul 27, 2010 at 0:46)

should take no more the 5mins i say five minutes because i have chainguide

dirtydroog (Jul 27, 2010 at 5:46)

Hooray! Another advert for Park Tools! Surely there must be cheaper alternatives?

brule (Jul 27, 2010 at 9:26)

Park Tools is what we use and what most professional shops use - they are the snap on if you will of the bike industry. If you don't like the tech pieces, you can skip them, kinda like your comment, you're spouting off to possibly look cool, when in fact you just make yourself look like a whiner.

dirtydroog (Jul 27, 2010 at 11:08)

Park Tools are great, expensive but great. I own some Park tools.

Is Tech Tuesday sponsored by them or not?

brule (Jul 27, 2010 at 11:59)

Yes they liked what we are doing, so we are working together on the tech pieces. We will have to step outside their programs at time in order to do more suspension or brake pieces, but for standing bike shop tech fixes, yes we will be promoting the Park Brand of tools. Thanks for the reply, it is appreciated.

cloverleaf (Jul 27, 2010 at 12:58)

In every industry there are tools which are accepted as the best. There are always cheaper alternatives, and in some cases these prove to be just as good as those more expensive, but if you want a guarantee of a decent minimum standard across their range then the top manufacturers are the ones to go for. If I was to do any of these articles then the chances are it would be with Park or Shimano tools, some of which have been in regular use from my toolbox for the past fifteen years which is a fair amount of use in anyones book. For bike specific tools Park and Shimano are my go-to's whilst Pedros also make high quality kit. For the less specific stuff Snap-On and Bahco (for wrenches) are good, if a little expensive. Britool & Stanley produce cheaper but very good quality kit that for the average user who wrenches their own bikes at weekends. I have some Bahco adjustables in my toolbox which are over thirty years old which says it all really. You really do pay for quality, and if that quality company happens to be working in conjunction with these articles then so be it, the chances are they would be the tools of choice in any case, regardless of any support they give.

caliber-410 (Jul 27, 2010 at 13:15)

Park Tools are Sweet

dirtydroog (Jul 27, 2010 at 14:23)

Thanks for the reply, Brule!

seraph (Jul 27, 2010 at 23:52)

"Shih-man-oh." That's the funniest pronunciation of Shimano I've ever heard.

k2dan (Jul 27, 2010 at 5:34)

man i love shimano cranks so easy to install