Originally Posted by
Chombi1
Curious to know, what brand/'model dropout is that?
Some dropouts like the Suntour GS seem to have more of their share of cracking at that exact place, through the years.....
Back in the 70's we sold some Crescent's bikes. The mid range non Campy Pepitas came with Suntour dropouts instead of Campy's. We had a number of the drive side Suntour dropouts break. We though that they were made of a steel that got hard from cooling too fast and ended up being brittle???
They were a different model dropout than the OP's but maybe the same cause/issue???
Originally Posted by
davester
It's pretty certain that happened due to dropout misalignment. When I took my frame in to have it painted a couple of years ago, the frame builder doing the painting pointed out that my dropout was cracked in just such a way that dropout misalignment was the cause (even though mine was only a 120 -> 126 spread and I had the frame cold set and supposedly aligned by an experienced mechanic). He noted that clamping the quick releases shut on misaligned dropouts puts a constant stress on the dropout that results in the cracks and that he'd seen this on many bikes where people had just spread the frame without realigning the dropouts. Fortunately mine wasn't too bad and he managed to braze it back together.
This not to scale drawing show that spreading a 120mm rear triangle to 126mm without realigning the dropout leaves them sitting with a 5° toe in (assuming they they were properly aligned to begin with). Going from 120mm to 130mm leaves the dropout even more misaligned.
Not only does the misalignment put stress in the dropouts but causes the axle to bend enough when the QR is clamped down to result in uneven wear on the cones. They will be angled in at the same amount as the dropouts. This causes uneven wear in the cups too and can lead to bent or broken rear axles.
It's not just frames that have been spread, I've seen a lot of brand new high end bikes and frames with misaligned dropouts.
I bought this pair of Campy Dropout Alignment Tools in 1975 and I've used them on most bikes that I've worked on. One of my best bike tool investments.
Here's a YouTube video from RJ the Bike Guy that shows how to make a set of DIY dropout gauges with some cheap hardware.
Originally Posted by
cudak888
Grind a slight V in the crack and TIG.
Cold set it way it was supposed to be.
Touch up the minimally invasive TIG repair.
Ride.
-Kurt
Over a 2 week period a few years back I ran into a brand new stem with a crack, a crank arm with a crack and when I checked out what looked like a scratch in the paint, a cracked dropout.
I stripped paint off the "scratched" area and sure enough...
I had a frame builder friend TIG weld it for me. The dropout broke when he ground the V notches in so it was ready to go. It was a Shimano UF dropout which had a reputation for cracking in that area.
He ran a TIG bead on the inside and outside of the broken area, shot it with some primer and voilą. The weld will be stronger than the dropout.
TIG welding is a lot easier and results in much less stress in the stays than replacing the whole dropout.
verktyg
