Stripped threads on pedal/crank.

Brandane

Fair weather cyclist.
Location
Ayrshire.
We have a problem I am hoping the good knowledgeable people of CC can help with.

Lovely fiancees daughter recently bought a new bike from Halfords online. A Boardman hybrid with Shimano Acera gears, and a crankset manufactured by a company called Prowheel. Chainset is a 9 speed double 48/32 teeth, 175mm cranks, square taper type.

Bike was delivered about 2 weeks ago, and she built it herself out the box. Sadly, she may have somehow messed up fitting the right hand pedal, as it fell off after about 30 miles of use, stripping the threads on the crank. I have tried to source a spare but as yet to no avail. There are plenty of 9 speed TRIPLES but not doubles. Is it a possible option to buy a 9 speed TRIPLE chainset, then simply remove the small ring?
 

classic33

Legendary Member
 

tyred

Legendary Member
Location
Ireland

fossyant

Ride It Like You Stole It!
Location
South Manchester
10 speed doubles will be OK. Doesn't have to be 9 speed.
 
OP
Brandane

Brandane

Fair weather cyclist.
Location
Ayrshire.
With that information, I just ordered this one for her. New pedals too. Hope it all works. Expensive lesson for her!
Thanks for all the help, CC :okay:.
OK...... Now I've fitted the new chainset to her bike - but why does the right crank and chainrings not go as far up the spline on the square taper BB as the original did? I've had to adjust the limit screws to compensate for the discrepancy (of about 3mm probably) but I was wondering if I've done something stupid/wrong? Are they not all manufactured to the same dimensions? Obviously I also moved the front derailleur up the seat tube to compensate for the extra diameter of the big ring (2 extra teeth) but I did make sure it was parallel to the big ring when I did that. NB... It all seems to work fine as it is; but just wondered, why?
 

Vantage

The dogs chew toy
Are they not all manufactured to the same dimensions?
This ^^^

You'll notice the BB axle tapers along it's length getting thicker towards the frame end, hence the name. As you tighten the bolt, the crankarm moves along the BB axle until it's a nice tight fit. Over time it'll loosen a bit as the alloy gets squished and further adjustments of the limit screws might be needed. All perfectly normal.
 

C R

Über Member
Location
Worcester
OK...... Now I've fitted the new chainset to her bike - but why does the right crank and chainrings not go as far up the spline on the square taper BB as the original did? I've had to adjust the limit screws to compensate for the discrepancy (of about 3mm probably) but I was wondering if I've done something stupid/wrong? Are they not all manufactured to the same dimensions? Obviously I also moved the front derailleur up the seat tube to compensate for the extra diameter of the big ring (2 extra teeth) but I did make sure it was parallel to the big ring when I did that. NB... It all seems to work fine as it is; but just wondered, why?
Not all crank sets take the same spindle length. It could be that the new crank set requires a shorter bottom bracket spindle, for instance, 118mm instead of 122mm.

In general, for a double, the crank set should end in a position so that there's minimal chain deflection when the chain is in the middle sprocket at the back. If not, chainline is wrong, and chain wear will be quicker.
 
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