Is it normal wheels go out of true after a fall?
 

Ran over a really bad bump, next time I knew I was falling on the drive side, handlebars took most of the brunt, RD had some scratches, steering went out of alignment, but I still could continue 150km after the fall.

Checked my bike by turning it upside down today and realized both wheels are slightly out of true, not sure how could this be given the handlebar took most of the brunt when kissing the tarmac..

You only think the handlebars took most of the impact but you are wrong. The bike took the impact but the most outboard part...handlebars...appear to have taken the impact. The "really bad bump" may have caused the wheel to go out of true or the fall could have caused it. Overall it doesn't matter.
Turning the bike upside down for any reason is similar to putting your motor vehicle on its roof to change the oil...never turns out good.

Yes. Wheels are very strong for their weight in a vertical direction (the direction that closely follows the spoke pathways) and are much less strong in a lateral direction (across the spoke angles). You can easily see this by pressing on the wheel/tire vertically (as a pot hole would do) than press sideways across the wheel/tire and see how much easier it is to deflect the rim.

If a rider went over a bump and didn't even fall, but when they hit the bump they were weighting the bike unevenly to one side (say when turning or leaning to one side a bit) the force would have more lateral aspect and could "knock" a rim out of true. If the rider hadn't lifted their butt up and off the seat while this bump was being hit the added load of their body only adds to the force the wheels see.Andy

Gotta disagree. While it is true that a wheel is less strong in the lateral direction, it is still strong enough for most uses. The bike and rider would put far more lateral force on a wheel when cornering than would happen during a crash. Most of the force in a crash is going to be centered on the most massive part of the system which is the rider.

That’s assuming proper tension on the wheels, of course.

See, you're doing it all wrong! Your wheels went out of true because you turned your bike upside down! Nothing to do with the crash! :rolleyes:

For a moment, I thought you were serious :roflmao2:

Well Stuart- I agree and disagree. Agreed that wheels are made to be strong/stiff enough for normal conditions and riding, and then some. (Although I know of no manual or educational materials that suggested hitting a bump in a corner was a good idea:))

The disagree is that for the rider's body to see the force when riding over a bump (and that is how the OP's situation started) the wheels are first in line for that force and any force the body sees has to travel through the wheels. Now if the rider does fall down and the body impacts the ground things change.

But we are closing the barn door after the horse left here. Whatever happened, and however it did, the forces were enough and directed enough to injure the wheels. So in this case the wheels were not strong enough. This is not a JRA incident.

I couldn't even begin to count the number of wheels I have trued or replaced dur to crashed and simple potholes/curbs. Nearly all the time the rider is not hurt and some of the time the rider didn't remember (or want to admit) to doing anything bad or wrong (and might try the JRA defense). Andy

Doesn't really matter why they got out of true. Just get them trued up by a decent wheel person at a shop. Might be after the crash you were just looking closer at the bike and the wheels were like that before. I've had many new wheels that are probably machine built need attention after 200 - 300 miles, however once they've had the spoke tensions checked and adjustments made, they are generally good for quite a few thousand miles after that.

If you want to find out whether crashes make your wheel go out of true, then I suppose you could crash some more. But you'd have to do quite a few so you know you aren't getting outlier data from a few.

ummmm i was serious

On day 2 of riding my then new to me hybrid, I made an unplanned abrupt stop.
I did a nose stand with the rear wheel about 3' (I wasn't looking back at the time) off the ground.
I kind of stepped off to the left and the rear wheel came crashing down at about a 45 degree angle from vertical. (I was basically holding on to one end of a large hinge with the other end under the influence of gravity)

It knocked the wheel out of true enough that I had to release the rear brake to ride home.
Simply put- The factory spoke tension was extremely uneven.
So, sometimes it doesn't take "That much" to knock a wheel out of true.

I ordered my spoke tension gauge the same day.

Hitting bumps in corners is common…stuff happens. It’s even more common in mountain biking where the surface is not even close to as consistent as paved surfaces. Mountain bikes don’t suffer an increased incidence of the wheels being out of true on either the front or rear because of that. Mountain bikes also tend to be more likely to be involved in crashes and, again, they don’t suffer an increase in damage to the wheels

That assumes that the bike and rider are a solid body. It’s more nuanced than that. The rider’s joints serve to absorb some of the shock of the impact. Simply hitting a bump…even hard enough to throw the rider off the bike…isn’t going to throw the wheels out of true. I’ve had impacts hard enough to dent the rims and seen lots of other blipped wheels that weren’t out of true. Simply falling over shouldn’t cause the wheel to buckle.

The question I have is were the rims already out of true and Ev0lutionz just noticed it after the crash? That seems more likely than a crash that happened 150 km ago.

I have had a set of wheels go out of true....I crashed into the side of a bridge to avoid a person coming straight at me....was tryy not to crash but better the bridge side than head on.
the wheels were true before and got knocked out...not sure exactly how. ulegra 6800 hubs, double butted spokes and mavic reflex tubular rims

so it can happen, not sure hour routine it is

I have observed that my wheels had more of a tendency to go out of true, if I had inadequate air pressure.

Actually, it most definitely can.

I managed to hit some debris once (fair-sized rock or piece of concrete in the road that I didn't notice in time to avoid safely) and do exactly that. I didn't crash, but the wheel (which was true prior to the incident) was was definitely not true afterwards.

There is no lateral force on the wheels.when cornering. The bike is leaning into the corner, that converts any lateral force into perfectly straight down force as far as the bike is concerned. You would only have lateral force if the bike is unable to lean, such as in trikes.

any broken / sketchy spokes? have you checked them all individually?

And your wheels went out of true! I don't understand the the surprise. Sure they went out of true!

You always need to check everything on your bike after a fall. Even my old steel ones. I know you know this. Check your Pre-Flight, In-FLight, Post-Flight and Crash-Inspection lists. They should be long. Especially if your ridding a modern bike made of exotic materials with fancy Do Dads. Just a little spill could be disastrous in cost.

My last little spill was just one of those "got my front tire stuck in a crack" fall. Just a busted spoke and handle bars out of alignment but still I took a step back, went through my Post Crash-Inspection list, and found my rear wheel out of alignment and my rear quick release bent too... Go Figure...

It's good to hear you were able to finish your ride and also that you did not receive injury, other than your poor bike... Ha

If you mean that the stem got twisted on the steer tube, than the wheel most likely WAS subject to a equal but opposite twisting force. At the very least the fork was.

You are incorrect. The lateral force is the centripetal force that pulls the bike around the corner. When riding in a straight line, the normal force is perpendicular to the wheel. Pedaling does introduce some lateral force to the wheel but we’ll ignore it for now.
https://cimg3.ibsrv.net/gimg/bikefor...63608ead9.jpeg

In a corner, the downward force (red arrow) is at an angle to the normal force. The forces are a combination of the normal downward force due to gravity (green arrow, which is in the wrong direction, sorry) and the horizontal force on the wheel due to the centripetal force on the wheel that pulls the wheel around the corner. For the wheel’s point of view, the rim is bent out of line with the hub.

https://cimg6.ibsrv.net/gimg/bikefor...fc8ab4e29.jpeg

I just got done with you on that brake heat debate and am not really interested in debating you on yet one more of your physics misconceptions. Yes, you can dissect the force into the horizontal and vertical component forces, that's how a free body diagram works, but that doesn't mean the horizontal force exists on its own. The vertical component is there too. The summed force vector is in the plane of the bicycle wheel. This is part of the fundamental balancing mechanic of bicycles. You are always leaning the bike to the exact degree such that the force is straight down from the perspective of the bike. That's how the bicycle stays upright. The bicycle is a bizarre device that has no left-right support. You must always keep the force completely straight downward via manual corrections, or you will topple over left or right. This applies to both straight riding and corner riding. You must always keep that force straight down in order to remain in balance. There is never any lateral force as long as you are riding the bicycle properly. If you ever find yourself experiencing a lateral force, it means you've f'ed up your steering and you are now currently in the process of falling over.

If you wish to experiment: go to your rim brake bike. Release the cable tension on the brake arms. Grab your rim next to where the brake pads are and wiggle it side to side. Notice how you can move the rim side to side about 5mm with very little hand force. This is because bicycle wheels are not very stiff laterally. Now set your brakes back into place. How much gap do you keep between the pad and the rim? I build my own wheels and like to keep my brake levers responsive, so I set my pads only 1.5mm from the rim. You might have a bit more. If there was any lateral force on the rims during turns, they'd be rubbing the brake pads in every corner. I don't know about you but my pads do not rub when I turn corners.

Explain please. I have a stand to work on my bike but have turned it upside down to take off a wheel to fix a flat.

I’m looking forward to this. :popcorn

me too…..i never bought a stand…always flip a bike over…especially changing a flat on the trail…

Cyccommute—you definitely know your physics…but the reality is that most of us have been biking 30+ years…and when you take a spill or hit a particularly bad bump…well…the wheels often go out of true. They just do.

What’s the fun in that?

I never said the horizontal force exists on its own. But the horizontal force exist and it does have an effect on the forces on the wheel. The bicycle wheel is a tensioned structure which behaves differently from a rigid structure. The rim is detensioned (slightly) directly above the contact patch. The rim deflects upward when the wheel is vertical and it deflects out of plane when angled. Although exaggerated, this illustration shows what happens to the rim when cornering. The spokes on the outside of the curve are going to undergo a decrease in tension while the spokes on the inside of the curve are going to undergo an increase in tension. Because the structure isn’t solid, the rim can float on the spokes and will bend more in response to side loads in a corner than rigid wheel would.
https://cimg1.ibsrv.net/gimg/bikefor...6ece351b8.jpeg

That said, the balance between the tension on the spokes on each side of the wheel keeps the wheel from collapsing. It doesn’t mean that the rim won’t bend upward but only that the whole structure doesn’t collapse.

That’s not how that works. In a corner your center of gravity is not “straight down” nor is it aligned with the ground. Your CG can be quite a bit to one side of being aligned with the bike and can be way off to one side. The limiting factor is that sideways force and the friction of the tires.

5mm of side to side play? Say what? Only if your spoke tension is barely enough to have engaged the spokes in the rim. 5mm of play would be a lot for a wheel in the initial stages of building.

I don’t disagree that they aren’t as stiff laterally as they are horizontally but that was sort of my point. Bike wheels are stiff enough laterally that they won’t go out of true simply because you hit a bump or because you drop the bike on the ground. Trap the wheel in something and the wheel is going to bend like an untensioned spoke but for “just riding along” you aren’t likely to make the wheel go out of true because of a crash. If you notice that the wheel is out of true after 150 km of riding after a crash, I would attribute the lack of trueness to be due to some other event.

No, the rim would not bend at the brakes (unless the wheel is severely under tensioned). The angle of the bend in the illustration above is not the only thing that is exaggerated. The force on the rim is going to be at the contact patch and only that part of the rim is going to deflect away from being perpendicular with the hub. Since the rim isn’t very rigid, the spokes on the upper part of the wheel are going to keep the rim perpendicular with the hub. The actual picture of the wheel will be more like a hockey stick than what is depicted in the illustration.

Again, this is all predicated on a wheel under proper tension.