Crank and Pedal Fell Off

[redburnsblack]

Hi,

I am looking for some expert advice please!

Whilst I enjoy cycling and am competent at changing a tyre and all that sort of basic maintenance I was cycling to Uni this morning (yes students are awake in the morning) my left-side pedal and crank fell off which left me somewhat stumped and flailing in the rush-hour traffic.

Anyway, my bike is a 2006 Carrera Kraken (Halfords), which has Truvativ Isoflow cranks, which it seems aren't that great (from what I have been reading on various sites)

From what I've gathered, as the inner thread is completely chewed up, I won't be able to just stick a new bolt on it and be up and running, but I will have to get a new one. The site I was looking at seemed to suggest that the thread being chewed up was the result of poor installation - which would mean halfords I guess.


So my question is which one do I go for, what do I need to look for, what size do I need to get or is it all the same?


I don't mind spending a little bit more if it's going to result in a marked improvement. But more than anything I just want something that's solid and isn't going to fall apart on me again. My budgets probably £40-50 but like I said I will pay more if it will be a lot better.

Cheers and many thanks!

Rob

 

[Mr Pig]

Hi there, welcome to the forum :0)

Unfortunately I'm not a bike mechanic but I do know you'll be able to sort your bike for well under your budget.

The bottom bracket, the part of the frame your crank bearings go into, is the same size on all mountain bikes. However the length of the shaft that the pedals bolt to varies. What you need to do is buy a BB bearing that is the same size as the one you have on the bike.

There are a few different types of crank/bearing and you need to buy a bearing and cranks that are the same type. However, I'd look carefully at the cranks you have as if they are ok you'll just need a new bearing.

If you remove the bearing from the bike, which requires the right tool, it will have a number on it that will help you to make sure you buy the right one. You can just measure it but sometimes even bike shops get it wrong.

 

[John the Monkey]

redburnsblack, whereabouts are you? Someone may be able to recommend a good LBS for you to take the bike to.

 

[redburnsblack]

Thanks Mr Pig and John the Monkey,

I live in Reading, Berkshire,

So basically

either a new set of bearings if i can get away with it or a new set of cranks entirely

i'll post some pictures so its easier to diagnose. to my eye it looks pretty shot.

cheers again

 

[redburnsblack]

For your viewing pleasure, please find attached link to album of pictures of damage, any questions at all please don't hesitate to ask me

http://photobucket.com/crankfelloff

 

[02GF74]

looked at the photos - it appears to be similar to the shimano splined bottom bracket. it is unlikely that the bottom bracket is damagaed as it is made from hardened steel but the splines in the pedal look a bit rough.

it looks to me that the bolt holding the pedal loosened, the pedal came off the splines a bit and the as you pedal it stripped some of the splines.

there appear to be splines still on the pedal - are you able to fit the pedal onto the BB and it stays in place?

All that may be required is to clean the lot up, fit a bolt and do up the bolt tight - there looks like there is enough undamaged spline left in the pedal to stay put - quite hard to tell without seeing it for real.

 

[redburnsblack]

cheers, I will give that a go and see if i have any luck

 

[redburnsblack]

hi i tried that, and it goes on about half way (using the persuasion of a rubber mallett), but then sticks fast, so I have taken it off now

i guess i need a new bb and crank as both, to me, seem too smoothed over and messy tbh?

what would anyone recommend?

 

[Mr Pig]

I guess I need a new bb and crank

Looking at the pictures, the bottom bracket looks fine to me, just the cranks that are chewed up. I'd just buy new cranks.

The cranks 'should' be tight from just beyond half way. I'm not saying that you'll get away with that crank you've got, I'd need to see it in the flesh, but you pull the crank onto the BB with the fixing bolt.

You could use this as an opportunity. If you use your bike mainly on road you could buy a crank set with more teeth on the big ring. That'll give you a bit more speed at the top end. You'd need to move the dérailleur up a little but it's an easy job. Failing that just buy an exact replacement for what you have, should cost you about £30, bolt it on and you're done :0)

 

[jay clock]

look like you need a new crank arm that side only. The splines on the BB axle look ok. I am sure that is the sort of thing you can find on EBay....or a shop may have an odd spare. Or someone on here may.

 

[jay clock]

I just looked. Tryvativ Isoflow is a model type. I think the BB type you have is ISIS. If so any ISIS left hand crank of the right length should be ok

eg this

this

but check the length. May be worth taking to the bike shop to check what is wrong, then buying of Ebay and doing a DIY job

 

[Mr Pig]

....or a shop may have an odd spare.

Yip, worth asking. I got a new crank/chainrings that were lying around in a shop for £15 a few years ago. Remember to check the length of the arms, they are not all the same.

 

[redburnsblack]

cheers everyone for the help i'll have a look into just a left crank for now.

thanks again

 

[fossyant]

ISIS again......... if the BB splines aren't chewed then a new crank might be OK, otherwise replace the lot....... ISIS got dropped pretty quick.

Square taper - been there for years, ISIS type....a few years, and very quickly dropped for Hollowtech.....

On a budget, get square taper...loads available.......

 

[Mr Pig]

ISIS got dropped pretty quick

Why was that? Not very good?