Something about a shalow depth of field just makes me happy.
Tonight at bike time, we were doing a lot of crank work. Justin replaced the bearings in his classic Fuji's bottom bracket. Sadly, it seems the races are toast. I swapped the ISIS Bontranger triple on my Penna for a Raceface double.
To get cranks off a bike.. you need to remove the bits holding them on. In this case, with an 8mm allen wrench.
If everything is right with your bike, that won't actually get the cranks off. The fit between the spindle and the crank arms is everything short of interference, and it will be very tight. They sell crank pullers to deal with that. Here's mine.
To use one, you thread that outer nut into the crankarm, then you twist the lever (or inner bolt, if you have a cheap one) until the crankarm pops off the spindle.
Pop goes the crankarm. That kind of spindle interface is the old style ISIS. It's got a bunch of scaloped surfaces providing a huge number of places for the crank to index and support itself off of. square tapers only have four faces, and are subject to wiggling and if they're ever overloaded they will continue to get looser. I suspect an overloaded ISIS crank would just crack..
And the non drive side..
Next to be extracted is the bottom bracket itself. This is a sealed bottom bracket, with the modern instalation drive splines. That's what the funky socket is designed to work with.
The non drive side on my bike was... we'll say firmly stuck into my frame. It only took a minor grunt to get it loosened once I had both wrenches on the socket.
And then comes the drive side. It too was in there really freaking tightly. I think the specified torque is something like 50lbft, but it took way more than that for the cups to come out.
Here's the new bottom bracket that's going in. It's an external bearing setup. The black bit in the middle is just a plastic tube to keep crud from inside the frame getting into the bearings. The red stuff on the threads is a pre-applied thread locking compound.
You install the cups seperately. Which does pose some problems. By being short and wide, making sure the threads are lined up is somewhat difficult. With conventional sealed bottom brackets, the spindle keeps the cups aligned and cross-threading is a much smaller issue. ... I'm bring this up, becuase I did manage to cross thread the drive side.
The pre-applied threadlocking compound is what really did me in. It causes about the same amount of drag on the wrench as if you've cross-threaded it. Knowing this, I ended up spinning it almost two full turns. Yeah... not good. I think the next crank on this bike will need to be a spindle setup, so I can have deeper threads than you find on external bearing cups.
Next up is to install the crankarm. External bearing cups have rubber seals, and those ride on the shiny bits of the crank. To get those seals to slide over the spindle, you should use some grease. you should use some grease anyway so the seals can slide.
And here I'm fitting the new drive side crankarm. This crank has something called a captured bolt. So it won't need a crank puller. The captured bolt, has a small cover over it, as you unscrew the bolt, it pushes on the cover, and pulls the crank out for you.
Because the bolt sticks out a little bit, getting the crank on the splines can be a little hard, as you need to align the splines, and turn the bolt at the same time. It's only a "little" more work.
And Viola, new cranks.
These cranks are a LOT stiffer than the last set. Not that I found the ISIS spindle particularly flexy. The frame is a Fetish Cycles Penna, which uses some really big tubing all over, so it's really stiff too. It makes any flexible components really stand out.
Once again, thanks to NegativeK for having patience and taking good pictures.
No comments:
Post a Comment