So my crank fell off today,,,,,,,,

saracen fan

.....and I dont know why!

Bolt just came loose and the arm dropped off. threads are ok, no visable damage.

just wondering why it may have dropped off?

on a nother note.....weighed the crank and peddle.....600grams!!!! :shock: for one crank arm!!!! chuff......(Truvativ X-flow)
any strong cranks that are lighter?

nicklouse

square taper fitting?

the bolt came off and you would have felt the arm moving but you kept on riding.

Mostlikly the taper is now damaged.

New crank arm/cranks time.

saracen fan

hi nick, yeh I could feel a clunking under my left foot so stopped to check the arm and it was loose, I wasnt far from home so just free wheeled it down the hill and pushed it home, by the time I got it in my shed it had dropped off.

I have refitted it and it seems to fit tight on the square post thingy....and the bolt has redone nice and tight.....is it possible it is still damaged?

a.palmer

The likely-hood is that it will keep coming loose now as you ride because the square taper in the crank will have been changed from using it loose. It happened to me a few weeks ago and i had to get a replacement LH crank arm

The Joe Show

Take the bolt out (again) and dab some loctite on the threads then re-install it. If it falls off again, i'd probably advise a new crank arm.

saracen fan

damn, only had the bike 5months......
think I will look at some new crank arms....any recomendations?

a.palmer

You'll only need to replace the left hand one. Just find one of a similar shape and the same size and colour to your old one. There are a variety of left hand crank arms here
http://www.cyclesportsuk.co.uk/index.php?cPath=572

diy

unless you want to change the BB you are stuck with a square taper

The Rookie

Look around used, square arms are no longer 'in' and cheap, I have a Deore pair that cost me a fiver, 750g the pair.

Simon

saracen fan

*update

I have since done 5miles since refitting the crank arm, doesnt seem to be a problem so im hoping I have got lucky!

cdubu

Good old square taper! The same happened to me a few years back but I was in the middle of a long ride and had to scoot back with one leg, not fun!

UncleMonty

I'd take a socket set out with me if I was you, you dont want to get stuck and have to walk 10 miles back home.

I had the vary same problem for about 3 months, depending on the riding surface I could go for between 10 and 20 miles but it would always work its way loose, I tried locktight too but same thing, I finally bought a new crank with external barings, best £40 I've spent in a long time. .

saracen fan

dang.....so something like an octalink shimano jobby would be a better bet?

seems wierd that they dont reverse the thread on the left crank arm like they do on the peds, wouldnt come loose if they did!

saracen fan

so it came loose again today.....

does this mean new crank time? I dont know whether to replace with like for like or upgrade it while its knackered?

the current set is truvativ X-flow, im assuming this is an entry level set as the bike was only £550 when new.....?

any suggestions people?

Dirtydog11

saracen fan wrote:

so it came loose again today.....

does this mean new crank time? I dont know whether to replace with like for like or upgrade it while its knackered?

the current set is truvativ X-flow, im assuming this is an entry level set as the bike was only £550 when new.....?

any suggestions people?

Looks like a new chainset then.

It happened to my brother a couple of weeks ago on his brand new Giant Yukon (Truvative ISO Flow chainset). He was half way up the first climb at Llandegla when it came loose we tightened it up but it just kept coming loose again. I've just bought him a Deore Hollowtech 11 for Xmas. CRC have got them in black for £49.99.

If you can stretch to it then you would be better off with the SLX as it has Hollow crank arms (stiffer than the Deore) and a composite/steel middle ring.

saracen fan

http://www.chainreactioncycles.com/Mode ... elID=46025

well I just brought this....as money is tight and it matches the gearset

although i just thought is the problem the crank arm itself or the spindle?! if its the spindle im screwed! :shock:

I thought the crank arm square taper must have been streched out/misshapen, allowing movement thus causing it to come loose....please tell me im right and its not the spindle being rounded off!!!!!?

a.palmer

Yeah it'll be the crank arm that's changed not the spindle. The spindle is made of a harder metal

Dirtydog11

A.Palmer wrote:

Yeah it'll be the crank arm that's changed not the spindle. The spindle is made of a harder metal

+1

saracen fan

phew!
im glad about that..........hopefully I wont kill these ones.....
seems an awfull coincidence that I have a knackered crank arm and buckled rear wheel at the same time....to much air possibly?!

John Stevenson

Crank arms come loose if they are not properly tightened in the first place, or if they are defective - they just don't fit on the axle properly. Unfortunately the latter is hard to prove.

Correct tightening torque for square taper cranks involves a surprising amount of oomph. It's worth buying or borrowing a torque wrench to develop a feel for this.

The Rookie

On most ratchets its FT and a bit more, so moose it on up!

Reversing the thread won't stop it coming undone, its not twisted like a pedal as the square taper is the ant-rotation element.

Simon

saracen fan

well the new one should be here tommorow, so once its all bolted on I will do it a quater turn from shearing!

Am I right in thinking when changing the chain rings I can just slip the chain off the granny ring and just unbolt/replace accordingly?

The Rookie

Yes.....

bails87

No.








You'll need to remove the chainset from the BB.

saracen fan

I received and fitted my alivio chainset today, managed to fit it even without a crank puller!
wasnt expecting to have to re-set my gears up (but then this is my first time fitting a chainset) although the chain rings were the same number of teeth they must be bigger than my previous truvativ X-flow....so had to move the front derailuer up and slightly across.
managed to get the gears all fundementally working, however I cant stop the chain from rubbing against the front derailuer in certain gears (and not the gears that your not meant to use in certain combo's IE large C.R - large sprocket ect)
any tips to help me with this major headache please?

t-bone-king

Make sure you give the new alivio a good whack on, otherwise itll work loose and the circle starts all over!

Try putting the bike on its side, resting one side of the chainset on a block of wood, and whack the other side with a mallet or something. Then you can put the screw in. (Only hit it with wood or youll mangle it!)

saracen fan

I seem to be having problems geting rid of chain rub!
I followed numerous guides on how to set up front derailuers, basically all the gears work fine, but on the middle ring on the largest 2 cogs I get the chain rubbing slightly which is bugging me.......
basically what I have done is thus:
set high limit on top ring, small cog
moved to small ring, big cog, wound barrel fully in, removed cable from derailuer and set low limit, however, the guide says set the low limit so that the inner edge of the cage just misses the chain, if I set it like this I get unstoppable chain rub in nearly every gear on the middle ring no matter how much I adjust/tweek barrel adjuster, however if I set it so its nearer the outer edge of the cage its much better.
I then pulled tension on the cable and reclamped it in derailuer.
the main problem is if I wind out the barrel adjuster too much the chain rubs, if I have it so the chain doesnt rub theres not enough tension to chain gears smoothly.
ARGH help! :evil:

CFS

If you can't adjust out the rub, could be a chainline issue.

Recently replaced a very worn square taper chainset with a new chainset bought on chain reaction and in the end got the local bike shop to do it as the new chainset needed a different width bb axle to the old one.

The suppliers aren't always very good at telling you which bb axle width you need to go with your chainset.

The Rookie

Is the front mech parallel to the chain, it may be twisted round the seat tube slightly affecting its effective width.

Simon

saracen fan

im back....(laptop went down)

Simon- the front mech is lined up correctly as far as I can see

CFS- you may well be onto something there, I originally had truvativ X-flow set up, now have alivio but the chainline doesnt seem right, on the mid front ring and large rear cog the chain is at quite an angle.......prob is bottom BB.

will drop it up LBS in new year as need rear wheel truing anyway.

Dirtydog11

saracen fan wrote:

im back....(laptop went down)

Simon- the front mech is lined up correctly as far as I can see

CFS- you may well be onto something there, I originally had truvativ X-flow set up, now have alivio but the chainline doesnt seem right, on the mid front ring and large rear cog the chain is at quite an angle.......prob is bottom BB.

will drop it up LBS in new year as need rear wheel truing anyway.

Yes it will be your chainline. When you bought the Alivio chainset you should have also bought the BB to go with it which was why I suggested the Deore HT chainset as although its £50.00 it comes with the BB.

You will need to replace the Truvative BB with a 110mm Shimano BB.

http://www.chainreactioncycles.com/Mode ... elID=34652