lateral tire movement

mattjf said:

Sorry for all these simple questions 🙂.

How much movement should there be laterally with a tire? I don't mean whether or not the wheel is true. The wheel is perfectly trued. But when the wheel is on the bike, and I grip the wheel, how much should I be able to move from side to side? I can move it slightly (touch the brakepads), but that is it. When I was riding today, I felt wobble at certain times. The simple explanation is it was the road, since I didn't feel it all the time. But due to my crash yesterday, I am worried. It seems like I should be able to grip it and move it a few millimeters, but I want to make sure. It was all I could think about when I was decesnding a pretty big hill.

-Matt

It is Physics:
1. How much force applied
2. How stiff is the wheel (Spokes, support angle, rim, etc.)
3. How stiff is the fork?
The range is large.. from .5 mm to 10 mm depending on the above and even hub related issues.. including QR Skewer.

mattjf said:

Sorry for all these simple questions 🙂.

How much movement should there be laterally with a tire? I don't mean whether or not the wheel is true. The wheel is perfectly trued. But when the wheel is on the bike, and I grip the wheel, how much should I be able to move from side to side? I can move it slightly (touch the brakepads), but that is it. When I was riding today, I felt wobble at certain times. The simple explanation is it was the road, since I didn't feel it all the time. But due to my crash yesterday, I am worried. It seems like I should be able to grip it and move it a few millimeters, but I want to make sure. It was all I could think about when I was decesnding a pretty big hill.

-Matt

As David said, all wheels have play. I'd first check the hubs for play and adjust them if necessary, then go on to look at spoke tension. If you have some riding buddies, maybe check the lateral play and spoke tension on their wheels.

If your spokes are loose, an LBS wheelbuilder can retension and retrue the wheel. Or, you can try it yourself, but it takes the care and patience to bring the spokes up to even and correct tension while keeping the rim true.

dhk said:

As David said, all wheels have play. I'd first check the hubs for play and adjust them if necessary, then go on to look at spoke tension. If you have some riding buddies, maybe check the lateral play and spoke tension on their wheels.

If your spokes are loose, an LBS wheelbuilder can retension and retrue the wheel. Or, you can try it yourself, but it takes the care and patience to bring the spokes up to even and correct tension while keeping the rim true.

Spoke tension is important for durability in the wheel, but, unless the spokes are totally loose, it has no effect of lateral stiffness of the wheel.
"1. Does stiffness vary with spoke tension?
Some believe that a wheel built with tighter spokes is stiffer. It is not. Wheel stiffness does not vary significantly with spoke tension unless a spoke becomes totally slack.

I measured the deflection of Wheel #2 while gradually loosening the spokes in quarter turn increments. The wheel did not display any significant change in stiffness until the spokes were so loose some became totally slack.

If the spokes are so loose that some become slack, the wheel becomes much more flexible. The last two data points below, 9 and 10, taken when the spokes were so loose the wheel was almost sloppy, show that the wheel becomes significantly more flexible when spokes on the detensioning side of the wheel actually become slack. That is expected: a slack spoke cannot add stiffness to the wheel; it buckles easily in compression.

A wheel whose spokes become slack while riding is a weak wheel, because slack spokes cannot support the rim. This can be avoided to a large extent by building wheels with tighter spokes. If spokes are tighter initially, then the sudden increase in flexibility shown in data points 9 and 10 is less likely to occur in use because a tighter wheel can bear a higher load before spokes become slack."
Quoted from:
http://www.sheldonbrown.com/rinard/wheel/index.htm

daveornee said:

Spoke tension is important for durability in the wheel, but, unless the spokes are totally loose, it has no effect of lateral stiffness of the wheel.
"1. Does stiffness vary with spoke tension?
Some believe that a wheel built with tighter spokes is stiffer. It is not. Wheel stiffness does not vary significantly with spoke tension unless a spoke becomes totally slack.

I measured the deflection of Wheel #2 while gradually loosening the spokes in quarter turn increments. The wheel did not display any significant change in stiffness until the spokes were so loose some became totally slack.

If the spokes are so loose that some become slack, the wheel becomes much more flexible. The last two data points below, 9 and 10, taken when the spokes were so loose the wheel was almost sloppy, show that the wheel becomes significantly more flexible when spokes on the detensioning side of the wheel actually become slack. That is expected: a slack spoke cannot add stiffness to the wheel; it buckles easily in compression.

A wheel whose spokes become slack while riding is a weak wheel, because slack spokes cannot support the rim. This can be avoided to a large extent by building wheels with tighter spokes. If spokes are tighter initially, then the sudden increase in flexibility shown in data points 9 and 10 is less likely to occur in use because a tighter wheel can bear a higher load before spokes become slack."
Quoted from:
http://www.sheldonbrown.com/rinard/wheel/index.htm

That's an informative report; and the result isn't what I expected or implied in my post. Your expert knowledge is appreciated....I obviously don't know a lot about wheels.

I did look at a wheel on a friend's bike that was very loose laterally, and retensioning cured the problem. But now that I think about it, several spokes were very loose, ie, so loose I could bend them easily out of column.