Generally speaking, how much runout can a bicycle wheel have and still be considered true?
4
-
2No wheel is ever truly "true". They just may have more/less runout than circumstances require. A wheel on a beater bike can be considered "true" so long as it's not rubbing. A wheel on a racing bike is not true if there is any measurable runout.– Daniel R HicksCommented Mar 14, 2015 at 13:27
-
One to two millimetres side movement is acceptable. Same for up and down motion. The front wheel being more sensible than the rear because wobble may shake the handlebars at higher speeds.– CarelCommented Mar 14, 2015 at 16:37
-
@Carel It all depends on it's use; see Daniel's comment. Handlebar shake is the least of your concerns on a twisty 80kph descent - the entire bike shakes!– andy256Commented Mar 14, 2015 at 21:54
-
It also depends on whether you have rim brakes or disc brakes.– Mike BaranczakCommented Mar 15, 2015 at 0:14
Add a comment
|
3 Answers
If your wheel is trued (lateral movement) to within 0.5mm it is considered good. Same 0.5mm tolerance for the roundness of the wheel. Just remember that you may need to take the "stress" out of the wheel as the spokes can wind up with the torque applied to the nipple. It is that pinging sound that happens when a freshly built wheel is ridden for first time. Simply squeeze the spokes together, as though you were playing it like a harp. You should hear some pings then check if it is true and round, adjust as needed.
You mentioned it was your front wheel so you can flip it round to check if you have it dished equally (lateral offset) as is the norm for most front wheels. A blob of blutac and a pin on the fork blade can be used as a guide. And finally the wheel will go out of true with use especially during the first few rides, so check it after a couple of months.
Hope this helps.
Mark
The standard for what "true" means varies by mechanic and the intended use of the wheel.
A perfectly true wheel, in the mechanical sense, may not be attainable. Roundness and lateral runout are measurable to .001 millimeters using commonly available shop tools. Most mechanics do not consider that tolerance necessary, but as that is the limit of the tools, that is what I would consider perfectly true. However it requires 4 things:
- Perfect roundness, measured by placing a gauge under the edge of the rim, and spinning the wheel.
- Perfect lateral runout, or rather a lack of runout. This is measured by placing a gauge at the brake track of the wheel, and rotating the wheel to track the runout.
- Perfect Dish. Dish refers to the centering of the rim on the axle, or in some cases between the dropouts of the frame. This is measured using a truing stand or a dishing tool.
- Perfectly even and balanced spoke tension. Measure using a tensiometer, the value here will vary significantly based on the type of spoke, the size of the rim, the material of the spoke nipple. But the constant here is that all the spokes should have exactly equal tension.
I am well aware that the description here is of a mechanically perfect wheel, and that such a thing does not exist. It would require a perfectly formed rim, a perfectly machined hub, which perfectly drilled and finished spoke holes, and that each spoke be drawn from a perfectly pure metal at exactly equal and even dimensions.
The beauty and simplicity of the bicycle wheel is that while our manufacturing tolerances are not up to that standard, the design of a spoked wheel allow you to offset the tolerances in one area with spoke tension. If a rim is not perfectly true and round, more or less spoke tension can be used to pull it true and round.
So a "perfectly" true wheel might not exist, but a functionally true wheel is relatively easy. And "perfectly" true isn't necessary.
-
1The additional to all that is that even if you had a mechanically perfect wheel, you still need to add a tyre (and maybe tube) to the setup. They aren't nearly as adjustable as a wheel. Commented Apr 17, 2015 at 17:05
-
A great summary. Any standards or rules of thumb on an acceptable amount of out-of-round, lateral runout and dish? I am looking at the front wheel I just built and wondering if there is much worth trying to do better than 0.5 mm out of round. (This is coming from a hobbyist perspective.)– Rider_XCommented Apr 17, 2015 at 19:30
-
What runout is acceptable depends on the use of the wheel, and the manufacturer. Xentis uses .2mm as acceptable runout. Lightweight, because of their manufacturing process, uses 1mm. I personally find anything more than .25mm to be an annoyance. But .5mm is not likely to be an issue. If you have doubts, check with the wheel or rim manufacturer.– zenbikeCommented Apr 18, 2015 at 23:26
Wheelbuilding machines can be configured for a .1mm precision. But the choice of tolerance is up to the wheel factory. Best machine-built wheels are trued to this maximum of .1mm precision, which is pretty good. Most man-built wheels have a run-out around .5 mm when new.
But when you are building your own wheel, or you are fixing it, a tolerance of around 1 mm is acceptable imho. More than 2mm and you will have problems with brake pads or you may feel some shaking while riding.
