How to improve kickstand physics

Factual Questions
1

October 17, 2016

My question is about the physics of how a kickstand works and how to make mine better.

Three months ago I acquired a 1988 Honda GoldWing, which is among the heaviest of motorcycles. The kickstand is deployed in the usual way. You use your left foot to swing it down and forward till it’s fully extended then you let the weight of the bike lean left against it and dismount. It’s exactly how the kickstand on a bicycle works, except that you can deploy the kickstand on a bicycle after you’ve dismounted whereas with an 800-pound motorcycle you must deploy it first.

The problem is that if the GoldWing is parked even slightly nose-down when you dismount, the kickstand collapses. If the front tire is lower than the rear tire by only a degree or two, when you let gravity have its way it tries to make the bike move down, which is forward, which is what causes the kickstand to swing backward relative to the bike, which means it is no longer supports the weight of the bike, which is why it crashes forward (and of course to the left, not the right), which is embarrassing, inconvenient, and dangerous. I promise.

Whether this is a design defect or not, I need to fix it but I don’t know how. Google searches I’ve tried provide no help, so I’m turning to you experts.

To address the physics, please imagine facing the left side of the bike as it’s parked on flat, level ground. If the kickstand is horizontal, i.e., undeployed, let’s call that 90 degrees. If it’s swung out to where it’s dead vertical (plumb) we’ll call that 180 degrees. Needless to say, any kickstand’s angle relative to level should be more than 180 degrees, that is, it should prevent the bike from falling forward by gravity if the front tire is lower than the rear tire. The problem is that it takes only a really small amount of nose-down attitude to collapse the kickstand on my motorcycle. Said another way, I think the angle of the fully deployed kickstand is not enough more than 180 degrees.

I’m not sure that’s the problem, I just can’t think of any other explanation. If you can, please tell.

What repair or other improvement can you suggest that would most easily and properly solve this problem?

As I see it, and I know almost nothing about physics, one solution is to effect some sort of improvement so that the pad of the kickstand lands more forward than it does now. If the kickstand’s current angle is 185 degrees, it should be changed to maybe 190. If I’ve got that right, how would you do it? The best solution I thought of is to sever the kickstand halfway along its length and weld the bottom half back onto the top half at an angle that makes the pad rest on the ground an inch or two forward of where it rests now. Does this make sense from a purely physics viewpoint or is there a better way? Is there a formula in physics that tells how much resistance to forward movement there is relative to how far forward the pad is from plumb?

I know I don’t want to change the angle at which the bike leans left, when viewed from behind, when it’s normally parked. If it leaned any more to the right it would be at risk of tipping over to the right, where there’s no kickstand. Also, when someone climbs into the passenger seat, it’s important that that adding and shifting of weight not allow the bike to tip past plumb. But if it leaned much more to the left it would be too heavy to raise back to plumb after sitting on it. Whatever change is effected shouldn’t change the bike’s left to right tipping angle when it’s parked.

Here again, a physics question: What difference would it make to catastrophic kickstand failure if when I parked it I first turned the front wheel all the way to one side or the other?

Finally, is there any benefit to leaving the bike in first gear rather than neutral to help prevent the kickstand from giving way? My GoldWing is 1,500 ccs spread out among six cylinders.

This is a lot of questions, and any potential answers or other thoughts you care to offer about kickstand physics will be read and appreciated.

2

Why not put the bike in first, and see how much effort it takes to move it? Unless you park it on an extreme slope, it’ll probably stay put.

3

Hopefully someone will be along with some mechanical advice for adjusting your kick stand.

Addressing your parking in general:

The bike should always be left in gear.

If there is a curb nearby, the rear tire should contact it with the bike being between 90 degrees and 35 degrees perpendicular to the curb. If exhaust pipe or body work contacts the curb before the tire, discard faulty motorcycle, purchase new one. :stuck_out_tongue:

4

The problem you describe has to do with the bike rolling forward and off of the sidestand. Pointing the front wheel one way or the other won’t affect this, but pointing it to the left will move the front wheel’s contact patch to the right, resulting in a wider triangle and making the bike less prone to falling to the right if someone/something pushes it in that direction.

Cylinder compression won’t matter on long timescales (e.g. when parked for hours), because cylinder pressure will leak past the rings and offer little resistance to very slow engine rotation. OTOH, with six cylinders, you’ve got a lot of moving parts to provide stiction when the engine has come to a complete stop. OTOOH, small cylinders means small valve springs, so the valvetrain won’t offer a lot of resistance to rotation. Ultimately, leaving the engine in first gear will provide some resistance to forward motion, but not much.

The safest bet is to park the bike on level ground, or turn it around so you’re parked with the nose pointing uphill; now the friction of the sidestand against the pavement will help prevent rollback.

5

You should always park a bike in gear to prevent it from rolling. Never leave it parked in neutral. You should also turn the front wheel to the left.

Parking on a flat spot or slightly nose-up is just part of having a bike. Sometimes you just have to keep looking until you find a suitable spot to park in.

Our parking lot at work is horrible for bikes. Fortunately there’s a few spots on the front lot that are level enough that I can always park there.

Parking against a curb varies with your location. Some places don’t want you touching the curb or having any part of the bike extend over the curb. In other places this doesn’t matter at all. Some places don’t allow multiple bikes to share parking spaces as well. Check your local laws.

With a big bike like that, it’s a good idea to get something flat to put under the kickstand on hot days. I’ve heard of heavy bikes sinking their kickstands into hot asphalt and tipping over. If you ever have to park on gravel, having something to put under the kickstand will prevent it from sinking into the loose stone as well.

6

After posting the above, I went googling to see if anyone made any sort of locking kickstand for parking on hills, and it turns out that Harley Davidson bikes have a locking kickstand. If the kickstand is down and there is weight on it, the kickstand engages a slot that locks it into place.

Harley Davidson apparently has a patent on this though, so don’t expect to see it on non-Harley bikes any time soon.

7

The shape of your stand was carefully considered by the engineers who designed it. Honda isn’t some DIY outfit in a rented garage. They’ve also been making GoldWings for 40 years now. There are definitely design tradeoffs there and I’d bet that kickstand is pretty well optimized for the bike’s total situation.

If you were to bodge some re-angling of the kickstand there’s a good bet you’ll find the cure worse than the disease. Now it won’t retract fully or maybe it lays the bike too far over to the left.

Another vote that one simply doesn’t park motorcycles on nose-down inclines, period amen. I always rode smaller bikes* with center stands. If I couldn’t muscle the bike upwards and rearwards onto the center stand that was my clue that I’d picked a downhill parking space and needed to move.

  • Aren’t they all smaller than a Goldwing? :slight_smile: I’ve owned Volkswagens with fewer cylinders, less ccs, and almost less gross weight.
8

Don’t recall the bike I saw it on, and maybe it was something custom, but the kickstand moved far forward of a vertical position so it couldn’t be rotated back the bike was upright. The stand leg was a lot heavier than the typical kind of i’ve seen on bikes so maybe custom, not a rod or tube, but a heavy piece of steel channel.

9

IIRC the wing kickstand is quite a shallow reach down from the centre point to the ground, its also relatively short. These two make it relatively easy for it to roll slightly forward. Lots of kick stands also point slightly forward when extended so in the event of a slight forward more it tends to dig in a bit, the Wing - no so much

You might check out the amount of free play in your kick stand, over time this can increase - and with yours being such an old machine there is plenty of chance that there is a lot of play in there - if that’s the case maybe you can fit a bush in it, or get a weld to partly fill the hole and drill it to the correct size

The main stand can be a real pain, but I would be inclined to make it easier to use, by putting an extender on to the arm and thus gain more leverage.

10

This thread and the anchor chain thread were both very informative.

11

I would not even consider the cutting and re-welding the stand. That is an 800 lb bike and your suggestion is likely not going to be as strong and therefore will likely end with you coming back to a bike laying on its side.

I ride an 800 lb VTX and I always leave it in first gear when I park (no matter flat or hill or what). I know a lot of Harley guys put it in neutral and then crank it while it is sitting there, and I am not sure about a 1988 model, but my VTX will not crank if the kickstand is down.

As has been mentioned, Honda knew what they were doing when they built it, sure maybe you could make some changes, but why risk the bike.

Leave it in 1st and don’t park nose down.

I have never had mine roll off the stand.

Jeffery

12

I’ve had this happen to me a time or two. Then I learned to turn the motorcycle off, put it in first, release the clutch and let it roll forward a bit. That should keep the bike rolling forward any more. Then put down the stand.

If you do back in to a spot I personally wouldn’t put the tire up against the curb. I used to do that, until my tire got caught in such a way that I was unable to stand it up enough to retract the side stand. I had a heavy bike so I wasn’t able to push it forward by myself very easily.

13

Yes, I can imagine a kickstand where the prong is spring-loaded; it is out unless weight is put on it, in which case it moves in, say half an inch, and assuming it is in the fully open position, the end piece seats into a hole that locks it into the extended position. Unless you are the star of a motorcycle modification reality TV show, this is probably not something you could make yourself.

The physics is simple. Imagine a stick with a weight W on top, and the bottom is fixed on the ground. It is leaning toward you at angle a to the ground. You push it away from you. How much force do you need to move it? W cos(a) is the force pushing horizontal to move it, and W sin(a) is the force pushing the stick upward away from the ground. your physics for a kickstand is complicated by the fact the kickstand rotates on a fairly flat angle plane, not vertical to the ground. If you push your bike forward, the kickstand as it rotate to the 180-degree point, has to lift/rotate your bike upward a small amount.

Similarly, for a weight M pulled down a slope (b) by gravity, the force is Mg sin(b)

So for your motorcycle, when the pull downhill exceeds the amount of energy needed to lift the bike and rotate kickstand past the 180 point where it is ready to fold up, and there is not enough friction to stop it - then thunk.

14

October 19, 2016

First, thanks to everyone for all the advice so far. I will be more attentive to the pitch where I’m thinking of parking. I’ve already started getting in the habit of leaving the bike in first gear when I park (even though after some hours the engine compression will decrease significantly). I don’t so much want to cut and re-weld the kickstand shaft as I was wondering about the physics of what would happen if I did move that pad forward by a few more degrees. Nothing in the manual even hints at the possibility of kickstand collapse when parked nose-down.

Second, I just had a thought no one here mentioned, which is probably a good reason to believe it’s not a useful thought, but here it is anyway for your consideration.

Picture viewing the deployed kickstand from above. The oval pad at the distal end of the kickstand is about 3 inches from almost right to almost left (in line with the kickstand’s shaft) and about 1 inch from front to back (perpendicular to the shaft).

What if that front to back distance were increased?

To take an extreme example, imagine the pad is the same 3 inches from side to side but instead of 1 inch from front to back it’s 12 inches. Wouldn’t that extra distance help prevent the bike from rolling forward? For it to roll forward the bike would have to rise up in the air quite a bit, right? (I’m assuming a perfect coefficient of friction here.)

Now, 12 inches is absurdly long, but am I getting the physics right? Is it true that the longer that pad is from front to back the more resistance there will be to the bike’s rolling forward and collapsing that kickstand? As I’m seeing it right now, if the pad is longer in the front by just 1 inch (any addition on my exact kickstand must be made to the front, not the rear, of that pad, because of how it fits against the bike when it is in the up position), for the bike to roll forward it must rise up in the air by more than if it were less than an inch. The longer the extension the more it will resist the bike’s gravitary pull down, right?

If there’s a chance this idea has any potential, regardless of the exact way of implementing it, can anyone estimate in theory how long the pad must be from front to back to prevent kickstand collapse at a nose-down attitude of, say, 5 degrees?

15

I have never had a Gold Wing but the two bikes I owned* both had center stands in addition to kickstands, which makes all of this a moot point. For those who don’t know, a center stand swings down under the center of the bike and has two “feet” on it. You swing it down, stabilize it with one foot, and lever the bike up onto it, suspending the rear wheel slightly up in the air. A bike on a center stand ain’t goin’ nowhere, if the bike is reasonably vertical.

However, one time I parked on a soft asphalt lot on a hot day and the center stand sank until the rear wheel was on the pavement. The bike was still stable but it took a little effort to get the stand back up.

*Honda CB650, Yamaha Seca 750

16

One of my choppers has to be tilted slightly to the right to even get the kickstand to the full deployed position. It also has the need for the bike to be pretty well vertical before the the arm will clear the notch to begin to be moved to the stowed position. It also has a larger than normal pad on the bottom for soft ground and cleats for really soft ground.

Kick only bikes are many times parked in neutral, mine are.