Crank arm bolts too tight?

[bigfella]

Previously posted on another Forum but getting a lot of conflicting information. I know I should have used a torque wrench, but you live and learn...

Is it very easy to overtighten the crank arm bolts? The only reason I am asking as on my geared bike there is around 4mm of taper showing on the drive side and 2 mm on the other?

I am worried that one side is "too far down the taper".

I used the same tool as pictured below, its around 20cm long, I do have strong arms too!

I'm using a Campag Veloce 111mm Italian threaded BB and Campag Crankset.

If it has been overtightened, does that mean new crank? I take it the bottom bracket will be fine?

Here are some photos, it doesn't show the differences between drive side and non drive side very well.

Thanks in advance for any advice.

 

[steve52]

the taper inside the crank arms can vary if it works with no click or knocks and is smooth dont worry,

 

[PpPete]

Lost count of the number of square taper cranks I've had on and off over the years. Never used a torque wrench. How far the crank travels up the taper is not going to be affected by the precise torque you apply to the bolt. Just give it a good heave™. You'll never strip the bolt.

 

[02GF74]

it can be possible to overtighten but eventually you will split the alloy clranks andwould need extremely strong arms.

The lack of symmetry may be due to the BB design.

I would expect one cup is fixed to the BB - drive side usually and the other slides over the BB as you fit it tot he BB and tighten it. (one cup has to come off since how else would you be able to install the BB?.)

the important bit is how far the cranks are from the chain stays - if they are symmetrical, hen do not worry.

 

[Tim Bennet.]

What's a torque wrench? I heave on an allen key of that size till my eyes pop and have never had any trouble.

If the cranks go round without fouling anything, you're good to go.

 

[bigfella]

Thanks for the advice, much better than the other forum!!

it can be possible to overtighten but eventually you will split the alloy clranks andwould need extremely strong arms.

The lack of symmetry may be due to the BB design.

I would expect one cup is fixed to the BB - drive side usually and the other slides over the BB as you fit it tot he BB and tighten it. (one cup has to come off since how else would you be able to install the BB?.)

the important bit is how far the cranks are from the chain stays - if they are symmetrical, hen do not worry.

You can from the photo the spacing from the crank arms to the chainstays, it is ever so slightly different. Drive side 11mm ish and non drive side is around 8-9mm.

 

[Tim Bennet.]

If you measured yourself with the same degree of precision, I think you would find you are more lopsided than that.

It doesn't matter.

Go ride it.

 

[bigfella]

Haha, fair do's!

First commute tomorrow, not ridden it yet!

 

[swee'pea99]

Just remember when you come back covered in shredded skin, leaking blood and throbbing in every limb, it was all Tim's fault.

 

[bigfella]

Don't say that, you've got me worried now!!

 

[brodie]

You can't really tell if the cranks are too tight or too loose from the amount of axle showing or how close the cranks are from the chainstays.

The crank, axle and bolt should be clean and greased, then tighten to 35-40Nm. This is a weight of about 27kg on the end of a 15cm spanner. After about 100 miles, check the bolt; it will be looser but do not tighten again, just make sure it is tight enough so it doesn't fall out.

 

[bigfella]

I didn't think you were supposed to grease square tapered axles?

It was around a 15cm tool, so 27kg is quite a bit of force I guess.

 

[Tim Bennet.]

I didn't think you were supposed to grease square tapered axles?

While the usual suspects sit around and debate this to death, everyone else either greases or not, depending on their whim, and then go off riding.

I've done both at different times and it makes not one scrap of difference.

 

[bigfella]

Yes I have seen the debates alright, I will ride it and see how I get on. Just out of interest - what gets damaged, the crank or the bb?

 

[Tim Bennet.]

what gets damaged

When?