April 9th, 2007 by Nathan
Spring is a great time to overhaul your bike! Here in the Northeast it’s still a bit too wet to ride but it’s plenty warm enough to want to.
Links and tips for spring tune up / rebuilding:
SPD Overhaul:
http://www.parktool.com/repair/readhowto.asp?id=84
You can whip up a substitute PD-40 by drilling a piece of 1x pine board with 10 holes of 3/32″ diameter on a 3/4″ diameter circle, and punching out the center of the circle. Smush the board onto the knurled axle retainer and it’ll allow you to apply even torque to back the retainer out. (Be sure to remember that right hand pedal’s axle retainer is left-hand threaded.) Using vice-grips or pliers also works but runs the grave risk of breaking the plastic retainer. PD-M540s and M959s use a hex bolt-style retainer and don’t require the PD-40.
If your rear shifting mechanism is not performing well try the following things in the following order:
1: Fiddle with the indexing for a minute. If your indexing is off a hair it can effect a twitchy drivetrain. Fiddling with the indexing is the first solution to attempt, it’s easy and it’s reversible. Shift the bike into the highest (smallest) gear and then shift down one gear. If the chain doesn’t jump to the 2nd smallest sprocket back out the adjusting barrel until the chain shifts. (The barrel is located either where the cable exits the shifter or where the cable enters the derailleur.) Experiment a bit, it’s fun and it’s rewarding! (Those of you with rapid-rise / low-normal derailleurs will need to reverse this procedure — start at the lowest gear and work higher.)
2: Ensure that your derailleur hanger is straight. If your rig shifts well in the low cassette gears and not the high gears (or vice versa) that’s a sign of a mis-aligned derailleur. The derailleur should pivot about an axis parallel which is parallel to the wheel axle. Look from the rear of the bike, if the cage looks like it leans inwards or outwars the hanger may be bent. Look from the top of the bike, look for the main pivot bolt being bent backwards a bit. Go to the hardware store and buy an M10×1.00 nut & bolt (the longer the better) and use it as a gauge & lever to straighten the hanger.
3: If your rear mechanism shifts well as the cable is pulled, but shifts poorly or fails to shift as the cable is released your problem is most likely excess cable drag between the cable & housing. But before you replace your cable and housing check and see how worn your chain is (procedure below), and if your chain is sufficiently worn replace it. (If your chain is worn it needs to be replaced anyways and it may solve your shifting woes to boot.) Failing that replace your cable and housing with new. You mainly need to do this for your rear derailleur, your front derailleur has a much stronger return spring and is much more tolerant of cable drag. If you rear shifting is still poor spray some silicone lubricant into the body of the shifter and derailleur, cycle the system a few times to work the lube in. If your rear is still shifting poorly try adjusting your B-Tension screw to move the jockey pulley closer to the cassette. Failing that check and make sure your cassette lockring is tight, and that your pivot bolt itself is straight, then try swapping parts out and/or sacrificing chickens. (You can feel a bent pivot bolt as you screw it into the hanger, it’ll feel a bit wobbly)
Check your chain for wear!:
Having a worn chain is the fastest way to wreck your crankset’s chainrings or your cassette. Buy a Park CC-3 now! (Or from Jenson.) It will save you a ton of money in the long run. Alternatively measure a 12-link section of chain. When new it will measure exactly 12″ long. When the section is 12 1/16″ long it’s time to replace the chain. If it’s 12 1/8″ long or longer your drivetrain is wearing extremely rapidly.
To tune up your front mechanism:
First check and make sure the front derailleur is aligned parallel to the bike. This is a critical adjustment and as little as two degrees can make a big difference. Look down at the derailleur from above, the straight parts of the cage should be parallel to the chain rings and the bike frame. If you need to adjust the derailleur first release all the cable tension by shifting to the smallest ring.
Next check the height of the derailleur in relation to the biggest chainring. The cage should be between 2-4 mm away from the teeth. (Too high and shifting performance suffers, too low and the derailleur chain and big ring will grind together as you shift to the big ring.)
Next set the “indexing,” by shifting into the middle ring and rotating the barrel adjuster on the shifter. With the chain in the middle ring and the biggest rear cog the cage should be as close to the chain as possible without rubbing. According to Shimano shifting to the big and little chainrings is not controlled by the cable pull adjustment. So the cable pull barrel adjuster control the middle chainring shifting only.
Set the low limit screw so that the chain reliably drops to the smallest ring when the shifter is actuated, but high enough that it doesn’t drop off the rings all together and onto the bottom bracket shell. Set the high limit screw similarly: just enough to reliably shift up to the big ring but not so much that the chain falls off of the big ring.
Check your headset for looseness:
Engage the front brake with your left hand, grasp the steering tube/ headset / spacers underneath the stem and rock the bike back and forth. Use your finger tips to try and feel out any play between the steering tube and the top headset cup. For threadless headsets only: loosen the stem clamp bolts (which clamp the stem to the steering tube.) Tighten the top-cap bolt until the play disappears. Do not overtighten more than 1/4 turn. The fork should turn freely, there should be no perceptible drag in the bearings. Align the stem straight with the wheel and tighten the stem clamp bolts.
Bonus link:
Cup and cone ball bearing edification: http://yarchive.net/bike/ball_bearings.html
This collection of cup an cone Usenet posts seems to suggest that some preload is appropriate for cup and cone bearings. Certainly a little preload won’t hurt in your headset (but don’t over do it.) Although I wonder if extended bearing life is worth added drag for wheels / pedals / bottom brackets.
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