Cracked Sugino 75’s cranks ??

Hey guys!

I recently noticed some tiny hairline looking cracks on my sugino 75 mashsf cranks while cleaning them. They are very small, I’ve used a macro lense to get a close up pic. After noticing these cracks I checked my set of older sugino track cranks and noticed the same! :(

Is this common? What’s your thoughts?

Note: my mash 75’s are only about a year or two old.

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Get in touch with the place you bought them. You'd want warranty replacements if they're only a year or two old.

The problem is your legs. They are too strong.

Meanwhile, it's exactly the same place the Campagnolo Record/SR cranks would crack. Two separate examples:

Fuck, just saw this now, guess I shouldn't ride Paris Brest Paris with these then

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That's quite concerning. Also bearing in mind the thread on Miche Primato cranks cracking does the hive mind think that it might be happening due to load under braking/locking the rear wheel as opposed to drive mode?

I had a couple of Super Record cranks crack the same way. I ground out the cracks, checked by dye penetrant inspection. I shelved one set because the crack had gone too deep for my comfort. The other remained in use with no issues.

does the hive mind think that it might be happening due to load under braking/locking the rear wheel as opposed to drive mode?

Someone with better mechanical/physical/engineering understanding could probably explain it correctly but my understanding is that the forces are very similar. It might be the shock of going from driving to braking/skidding that is causing it?

Thinks its just the nature of crank design that it's a major stress point.
Dura ace cranks appear to have more material at point to spread the stress over a larger area and reinforce.
That said sugino are very well made, mostly they last for ever.

First pic look like Sugino Mighty from the 70's?

I seem to remember back in the day that it was common to very lightly file them down a bit, to get rid of the sharp edge which acted as a stress riser

my >10 yr old sugino xd cranks cracked this year :p

Interesting! I did a bit of searching and found another forum where people had similar cracks on cranks and had filed/sanded them out and kept riding. I wonder if this could be a safe option?

Is this cycling equivalent of square windows on airplanes? The DeHavilland Comet, famously had that design flaw.

Yes. Many older-style cranks have stress-raisers between crank and spider. Prophylactic rounding out can prevent cracks forming.

Feeling sad. Sg75DD. Check you cranks guys.
I have had these almost 7 years with at least 3 years of daily street use. And I bought them used, but have heard of some of the older bits lasting much better.
Omniums have arrived as a (hopefully) beefy replacement.

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