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Truing the Rim
If your wheel moves slightly side to side as you ride, your rim is out of true.
Problems: Brake pads may touch the tire at some point during its rotation, requiring you
to back off the cable tightness. Brakes may "wump, wump, wump" as you apply
them. The bike may wobble at high speeds. Dangerous stuff.
The first thing you should do is inspect the rim carefully. Look for nipples
(the thingies that the spokes screw into at the rim) that are pulling through
the holes, bulging or cracked metal near a spoke nipple, or cracks along the
braking surface. If you see significant signs of rim damage, it's time for a new
wheel -- not just minor "tweaking."
If you're a beginner at bike repair, anything but minor side-to-side wobble
may be beyond your fix-it ability. If you're going to get serious about truing
wheels, you need a truing stand. And you need more instruction and experience
than we can give you.
A good truing stand lets you detect:
side-to-side wobble
(laterally untrue)
flaring of the rim (time to buy a new one)
height
variation (concentrically untrue -- hub is off-center)
flattened areas on the rim
incorrect dishing*
tilt (one side of the rim higher than
another).
A truing stand will cost a bit. The UMB
on-line store sells a high-quality truing stand for serious cyclists.
*on the rear wheel,
the spokes are longer on one side than the other -- called dishing -- to
compensate for the cogs
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Yes, you can perform quick 'n dirty
"on-trail" truing without removing the wheel or tire. But for a good adjustment,
you should remove the tire from the wheel and do the work in a workstand. Trying
to "true" a wheel on the bike, without removing the tire, is a
good way to mess up the wheel. |
| If you already have a workstand, you can get an add-on
truing attachment. This is a bit better than doing it on your bike, but it
doesn't compare to a real truing stand like the one above.
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But let's face it. You aren't going to spend the money to do
it right.
Unless you have the right skills and right tools, you're better off
having a pro fix your misbehaving wheel. But here's the rub: when your
wheel starts to wobble, do you leave it at the shop for a week, or do you
true it up yourself so you can "make that ride?" |
So, the remainder of this section tells you how to (pathetically)
attempt to true your tire while it sits on your bike. Remember: this is
for minor adjustments of side-to-side wobble only.
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Before you start playing with the spokes, make sure the wheel wobble isn't
something else. Check for rocks tucked between the tire casing and the rim. Check that the
axle is correctly fitted in the dropouts. Take the tire off and spin the rim alone, just
to be sure a damaged tire isn't deforming the rim. Check to be
sure the axle sits properly in the dropouts, then check to be sure the wobble isn't the
tire's fault. |
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Take the tire and the rim liner off. Lube the spoke holes in the hub, rim,
and where the spokes enters the nipples. Now you need to put the rim somewhere where you
can assess the wobble. If possible, use a truing stand. If that's not possible, put it
back in the dropouts of the bike frame. Use the distance from the front tip of your brake
pads as your measurer. |
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Here's a poor man's truing stand: Remove the tire,
then place the rim on your upside-down bike. Clamp some sort of marker to
the chainstay or front fork, so it barely touches the rim. A screwdriver
or center-punch works well.
Here the point on the corner of the
screwdriver is the marker for both lateral (side to side) and concentric
(distance from the hub) truing. |
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Replace any bent or broken spokes. Remove a spoke by unscrewing the nipple
from inside the rim, then turning the spoke and pulling it out through the hub. For a
non-radially laced wheel (virtually all mountain bikes), you may need to remove TWO spokes
to replace one, because the shaft of one spoke may overlie the head of another. If the
broken spoke is on the freewheel side of the rear wheel, you'll have to remove the
freewheel to remove the spoke. This requires a freewheel removing tool (or a bike shop). |
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When replacing a spoke, tighten the nipple until the spoke has
just a tiny bit less "wiggle" (when you push it back and forth in the middle of the spoke shaft)
as those adjacent to it. Don't overtighten.
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Check around the entire wheel for any spokes that are obviously floppy.
(Make sure the looseness isn't a damaged hub or flattened rim. If the
problem is in the hub or rim, it can make things worse if you tighten the
spoke!) Tighten floppy spokes to just less than the average tightness of the nearby spokes. |
Spokes stretch slightly with time. Our truing discussion assumes that it's
spoke-stretch, or a nipple "unscrewing" itself, that's put the wheel
out of true. Therefore we suggest tightening of specific spokes. If, however,
your spokes seem to be under significant tension -- already very tight -- you
may want to do the opposite. That is, you'll want to loosen spokes to relax the
pull on the rim. But here's the basic strategy:
Truing action, based on overall spoke tightness!
Spokes overall rather loose:
Tighten 2 spokes that attach on side
of gap, 1/4 turn each (clockwise)
Spokes about right, on average:
Tighten 2 spokes on side of tap, 1/8
turn each (clockwise)
Loosen spokes between (attaching to
opposite side), 1/8 turn each
Spokes seem generally too tight:
Loosen 2 spokes on side OPPOSITE gap,
1/4 turn each (counterclockwise)
Repeat until rim comes into true!
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Time to start the truing process. Rotate the wheel. Stop the rim when it's as far from the brake pad
as possible -- maximum wobble, the furthest untrue.
On the side with the gap showing, find the spoke on that side which is closest to the
point at which you're measuring the gap. (Select the spoke that starts and ends on the
side of the rim that shows the gap between rim and brake pad.) Tighten that spoke by
turning 1/4 turn clockwise. |
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Turn the wheel again, and again find the spot that's the furthest untrue.
Again tighten the spoke on the side that's closest to the maximum untrue spot. Continue
adjusting spoke tension until the rim rotates without side-to-side motion. |
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To evaluate concentric truing (roundness), rotate the rim while holding a
reference. (Here we're using the point of a nail, with the nail immobilized against the
front shock. Locate the spot on the rim that seems highest. Correcting a
roundness problem is trickier, and can be frustrating. But if you want to
try it, here's what you do: Select the TWO spokes on
each side of the high spot (a right spoke and a left spoke) and tighten 1/8 turn each.
(Alternative: find a low spot and loosen each spoke 1/8 turn.) Turn the wheel again,
and repeat. |
| Squeeze sets of spokes gently, going around the wheel. Now check the side-to-side and
concentric truing again, adjusting as needed. |
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