Steel cranks

[silva]

Since I have had 2 cranks (3 weeks inbetween) broken at their pedal mounts, and both times had alot luck (on the way home, a mere 3 and 5 km), I want to minimalize this risk by going for better cranks / better materials, steel above aluminium.
My bike is now at a local dealer, who informed that his suppliers didn't have such models in stock, and asked me to search and buy the cranks myself, and bring them to let him mount them.
So I'm now looking around for cranks with specs square taper JIS, 107 mm, and steel crankarms and thus thread for the pedal mounts.
I accept the extra weight.
Any recommendations?
I searched around and found some, but experience made clear that the most accurate answers origin from people using the products, not the people selling these.
Thanks in advance.

 

[I like Skol]

Do you mean 170mm?

I don't know how you have broken 2 cranks in such a short time, how have these cranks broken?

Any cranks made in steel these days are likely to be very low-end budget parts of dubious quality. Personally I would look for something mid-range from Shimano. This might mean going second hand if you need to stick with the square taper bottom bracket.

Breaking cranks is not normal, are you stronger than Mark Cavedish (was)?

 

[Ian H]

Either just coincidence, or perhaps something to do with over-tightening the pedal. Pedal washers can help as well. Some older TA and Campag cranks were rumoured to be a bit fragile.

 

[sleuthey]

I would be more tempted to buy a crank extractor, washers and torque spanner and fit another set of standard cranks myself rather than paying a different sort of spanner to fit them. They should last longer than 3 weeks if fitted correctly.

 

[Milkfloat]

@silva You do seem to have a tremendous amount of 'bad luck' with your bike. How much work are you doing on it yourself and how much is being done by a bike shop.

 

[SkipdiverJohn]

You do seem to have a tremendous amount of 'bad luck' with your bike.

I'm not convinced luck has much to do with it personally....

 

[silva]

Do you mean 170mm?

I don't know how you have broken 2 cranks in such a short time, how have these cranks broken?

Any cranks made in steel these days are likely to be very low-end budget parts of dubious quality. Personally I would look for something mid-range from Shimano. This might mean going second hand if you need to stick with the square taper bottom bracket.

Breaking cranks is not normal, are you stronger than Mark Cavedish (was)?

No 107 mm, it's not referring crank length but bottom bracket, hence that "JIS", one of the 2 square taper versions (the other is ISO).
Both cranks broke around their pedal mounting holes, the first crank just broke off completely, the others pedal started to wobble, with 10 sec later totally ruined the cranks pedal holes thread, to then later on at inspection show 2 cracks starting from (again) the pedal hole. Probably the pedaling force pushed the crack abit open, effectively disengaging the pedal thread from the cranks thread.

Pedaling force is ofcourse not the cause, this must have been stress in the metal, maybe due to flexing, the axle is quite long in order to bring the chainring far enough outboard to keep clearance to the frame tube widening that provides room for 62 mm tyres. Just one idea, maybe there is another explanation, only that atm I can't think of one.

Yesterday and today I checked my previous bike. The axle is a spline with 8 ridges. A word I found for it is "Octalink". Since I used that previous bike at least 8 years in a similar role, and never suffered crank problems, I went to the shop and asked it it was possible to replace the new bikes crankset with such crankset.
Hollowtech was said to be no option due to a fixed axle length so inability to correct chainline along the axle length.

What did the shop do: chose the parts, assemble the bike, replace the original crankset to the current (broken) - not due to failure but to change the chainrings mount from 110 to 144, in order to find 1/8" chainrings for it.
What did I do: replace a chain, a chainring, and a cog. And the broken left crank, the poormans method (saw, punch, hammer).

Question: my current chainring mount (bcd) is 144 mm.
With the 8-spline / Octalink the 144 mm would be not available, the max would be 130 or 135.
That's crap because I bought spares for the 144 bcd so lost money.
I also hope the chains tension variaton gets solved with the crankset/axle replacement. Because I started to suspect the square taper as cause. It clearly deforms when tensioning a crank, and maybe that deformation can bring the spider offcenter the axle.
-

 

[rogerzilla]

Steel cranks don't normally use square taper, which relies on a soft crank bedding into a harder axle. They normally have a 2-piece design with a splined interface of some kind for the LH crank (e.g. the 30 year-old Tioga Revolver, Bullseye, etc which Shimano basically copied in aluminium for HT2) or are cottered. You don't want cottered; it's horrible even if you own a cotter press.

 

[SkipdiverJohn]

You don't want cottered; it's horrible even if you own a cotter press.

Nothing wrong with cottered so long as you assemble the parts using some grease and not dry. I've never needed a cotter press either. Just undo the nut a turn or so (or until flush with the end of the thread on the pin), give it a whack with a big hammer, then undo it another turn and give it another whack until the pin comes out. The trick is to place another piece of metal between the hammer and the cotter pin. Wood is usually too soft and absorbs the shock you often need to get the pin to shift..

 

[rogerzilla]

Yes, antiseize during assembly means they come out easily. But it's a small contact area, prone to wear and loosening, and to maximise this area needs careful filing. Cotter pins these days tend to be pretty poor quality.

The cranks weigh a ton, too!

 

[SkipdiverJohn]

But it's a small contact area, prone to wear and loosening, and to maximise this area needs careful filing.

If you've never filed a cotter pin to fit properly - you're not a proper cyclist!

 

[silva]

About pedal washers - according to what I've read the problem they should solve is that of a pedal mount along a flat surface so movable, fretting out the aluminium of the crank, triggering cracks that then grow away from the pedal mount. The washer protects the crank.
But a washer takes space, and 1 argument against their usage, that I heard, was that it means less thread screwed in.
Which would mean that the amount threads inside the crank arms, as designed by their producers, does not take into account a presence of pedal washers. True, not true, or is it a sometimes depending on... ?

 

[rogerzilla]

Pedal washers don't really work. The washer frets against the crank, rather than the pedal fretting against the crank. If pedals had conical or spherical seats, fretting would be much less of a problem and we could have RH threads on both sides.

 

[silva]

But a washer shares a principle with a roller from a roller chain: there are two sliding contacts in "series" therefore reducing the slide per contact and thus friction per contact.
And since the force comes from the other side (to the crank) of the washer, the distribution of the slide also leans to there.
Just shift the story to an extreme: imagine 10 washers, what will remain of the slide at the last one? Nearly nothing.
And on top of that, the pedal mount is steel, the washer is steel, the crank is aluminium. Steel frets out alu way more than other steel.
So I do see a benefit of pedal washers.

 

[davidphilips]

Why not just buy secondhand square tapper 105 cranks (or similar) on Ebay they can be bought for a few £s and are very strong and light.