zachsherm

Hey guys,

It's my first post here so I hope I'm doing this right.

​​​​​​I have a 2003 Fuji Track Bike and I ride street with it. I presume due to skidding my chainring bolts keep getting lose and it looks like it's shearing so I'm in the market for a new chainring, crank etc.

I was looking at Miche Pistard Air Chainset 172.5mm - 50T. There was a good deal on probikekit.com and it suggested I buy the Miche Evo Max BB30 Cups (68x42) for it as well.

I just wanted to make sure this will all be compatible with my frame, but I wasn't sure. Any advice would be great! Thanks in advance.
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andrewclaus

The specs look right but I haven't made that mod.

Andrew R Stewart 

We see a lot of home "made/serviced" single/fixed bikes with way too tight a chain. Given the lack of perfectly round cogs and rings this leads to massive forces on the ring hardware (and BB or FW bearings). As Francis says, " the correct chain tension on a single speed is no tension". Andy

Russ Roth

Your fuji is almost certainly english threaded, the BB30 suggests a pressed in bb, not threaded and the 68x42 reinforces that. Being a 24mm spindle its probably meant to work with a basic shimano threaded external bb which is cheap even for Dura Ace.

andrewclaus

That was my first thought but I think the OP is looking at this.

Russ Roth

That's what I assumed at first as well but threaded is usually referred to as 68x1.34(I'm probably wrong on the exact .34) which I believe works out to 41mm and not 42 but I could again be wrong. The threads in the picture do seem to lean towards it being right but it might just be a stock photo. But the product stating BB30 I wouldn't take the chance.

70sSanO

Sheared off chairing bolts on a fixie? As in it no longer stops?

You need to listen to Andrew R. Stewart regardless of what crank you go to. You need to get the chain tension set up correctly. You might want to go a narrow-wide chainring or a tensioner if the chain is still too slack/tight at different points in the rotation. I’m sure others have more fixed gear experience.

John

zachsherm

The chainring slips on the crank arms. It appears due to wear, the holes are now larger than originally and when I put a lot of force on the cranks quickly forwards and backwards, the cranks slip.

70sSanO

I’ve never had a chainring slip on a crank or had chainring holes elongate. I’m trying to picture how locking and skidding the rear wheel destroys a crank and chainring.

John

Edit added: I honestly don’t know if the miles of high torque pedaling forward is greater or less than the stopping.

zachsherm

I think it may be that the chainring is stamped and an older chainring as well. I do have strong legs as well, but I'd rather credit the deformation to the age and quality of materials.