Wobbly Wheels

woodyferrell · May 01, 2022, 01:54:04 PM

I have a RadCity 5 Plus. I noticed today when riding down hill the bide started to wobble. I checked all the wheels nuts and all were tight. When I get off the bike and shake the bike from left to right vigorously it seems very loose. Any theories or comments?

BBB · May 01, 2022, 02:54:21 PM

The spokes may simply need adjusted. This is common and can be done by a reputable bike shop or owner by having a basic spoke wrench tool and have access to Utube instructions. Certain spokes may need tightened while other get loosened on a wheel to bring the the wheel into the best radial alignment.

The wheel also may be bent or have a flat spot. This can sometimes be repaired by a reputable bike shop as well and could be less than purchasing a new wheel.

woodyferrell · May 01, 2022, 03:08:39 PM

Thanks BBB. I'll get it checked out.

Eric7 · May 01, 2022, 04:18:10 PM

You say you are seeing it when you go downhill. I interpret it to mean you have stability problems at high speed. This is so scary. Please figure it out before riding again.

Naturally, as suggested, check all fasteners and make sure they are tight. You can have something loose and at some vibration frequency at high speed, you reach resonance and the effect spikes.

Check wheel wobble. Rotate it and look at the edge, does the wheel go side to side or up and down? Check headset, stem, handlebar, seat and make sure they are tight enough.

Radding Along · May 03, 2022, 05:09:26 AM

I second the suggestion to check the headset. Since the bike was shipped with the headset apart, whoever built the bike may not have tightened everything up well.

Another common problem is the head tube not being pushed all the way up before tightening. This will create flex/movement in the headset area while riding.

Seldom have I seen a Rad bike delivered where the spokes are overly loose. On occasion they may be shipped loose enough to cause a clicking sound when riding, but not loose enough to cause a wobble.

Lastly, check the front wheel to be sure it is installed correctly and tight to the forks. I have heard multiple complaints about a wobbly from end, only to find the front wheel was not secured properly and ready to fall off.

DrSmile · May 03, 2022, 07:44:08 AM

Please see my post here:

https://www.radowners.com/index.php?topic=1733.0

Dlennard · October 09, 2022, 12:57:40 AM

Hi all, I've just taken delivery of my radcity 5 plus step through. At slow speed I definitely have a shimmy through the entire bike. The headset and stem are tight as is the front axle. Tyre pressures front and rear about 60. I have a front rack and a yep child seat on the rack. If I hold the front wheel between my knees and slightly shake the bars while facing the bike I do get a resonant wobble through the entire bike. Likewise at low speeds below 5 mph I get a wobble which means slow speed handling becomes very dangerous. I'm beginning to think that this is the bike geometry and construction at fault.

JedidiahStolzfus · October 09, 2022, 07:49:21 PM

My RR2 had a wobble in both wheels. I found that when I initially inflated them, the bead of the tire wasn't quite centered on the wheel. After I opened the valve to put in FlatOut I was more careful during inflation. Before inflating them I made sure the wheel was off the ground, and centered the tire as best as I could on the wheel and then slowly added air until the pressure held it in place.
No more wobble.

Ddaybc · October 10, 2022, 02:03:41 PM

Quote from: Dlennard on October 09, 2022, 12:57:40 AM
Hi all, I've just taken delivery of my radcity 5 plus step through. At slow speed I definitely have a shimmy through the entire bike. The headset and stem are tight as is the front axle. Tyre pressures front and rear about 60. I have a front rack and a yep child seat on the rack. If I hold the front wheel between my knees and slightly shake the bars while facing the bike I do get a resonant wobble through the entire bike. Likewise at low speeds below 5 mph I get a wobble which means slow speed handling becomes very dangerous. I'm beginning to think that this is the bike geometry and construction at fault.

What you're describing sounds like a loose axle, loose wheel bearings or a loose headset. Either carefully check them out or take your bike to a shop and have them trouble shoot what's causing the shake and then fix it.

BBB · October 16, 2022, 03:03:44 PM

If you have the step-thru style frame, we are finding that when loaded with a rear rack, the frame simply twists a bit. Yes it doesn't feel so stable at times but happens due to the nature of the aluminum constructed frame design and/ or lack of a top frame tube.

Seems to be worst at super slow speeds in our case, but I'll take the step-thru design with some frame wobble over the step-over design at this stage. Just hope it stays flexible and doesn't crack at the notch

Altema · October 16, 2022, 06:47:21 PM

Quote from: BBB on October 16, 2022, 03:03:44 PM
If you have the step-thru style frame, we are finding that when loaded with a rear rack, the frame simply twists a bit. Yes it doesn't feel so stable at times but happens due to the nature of the aluminum constructed frame design and/ or lack of a top frame tube.

Seems to be worst at super slow speeds in our case, but I'll take the step-thru design with some frame wobble over the step-over design at this stage. Just hope it stays flexible and doesn't crack at the notch

Sounds odd, which model do you have? I have the RadMini folding bike, and frame flex is not something I've encountered, even when riding with an adult passenger on the rear rack.

Dlennard · October 23, 2022, 04:07:40 AM

So. It's been to the bike shop and was disassembled and rebuilt. There is however no change to the slow speed wobble although it is worse when there is the front rack and child seat installed. The bike shop are on 100% sure this is an issue regarding the bikes construction and geometry. Is ever so slightly rubbish.

handlebar · October 23, 2022, 05:59:15 AM

Quote from: Dlennard on October 23, 2022, 04:07:40 AM
So. It's been to the bike shop and was disassembled and rebuilt. There is however no change to the slow speed wobble although it is worse when there is the front rack and child seat installed. The bike shop are on 100% sure this is an issue regarding the bikes construction and geometry. Is ever so slightly rubbish.

Maybe the rim is flexing side to side with respect to the hub. You could grab the fork with one hand and the rim with the other and see if you can move the rim back and forth. I'd try it at 60 degree intervals and do the same with the back wheel.

Even if it passed that test, i'd check for loose spokes by squeezing pairs together. I'm glad I did that to the Six Three Zero bike I bought a few weeks ago, before I even tried to ride it. The front wheel had several very loose spokes.

Eric7 · October 23, 2022, 01:20:02 PM

Are your wheels true? Have you inspected them on a truing stand?

You can check easily but taping a toothpick to the fork or the frame and have one end of the toothpick almost tough the rim. Then rotate the tires to see if the wheel wobble side to side or up and down.

My guess is that there is a fundamental frequency of resonance. When you hit it the bike resonates. Putting things on the rack or just the rack itself changes this frequency and that is why you are seeing the effect.

I assume you have already tightened the rack.

If you have a crack on the frame or a crack in the rack, or a loose connection, it can contribute to resonance frequency and amplitude.

Usually the frame has a geometry to prevent resonance and increase stability. But if the frame is bent then that may be hard.

One test, it is dangerous. I don't take responsibility if you do it. Can you ride the bike without holding on to the handlebar? That's a test of frame geometry. Don't go too fast. Don't do it if you don't know what you are doing and once again, I do not take responsibility if you get hurt.

handlebar · October 25, 2022, 04:42:36 AM

Quote from: Eric7 on October 23, 2022, 01:20:02 PM

One test, it is dangerous. I don't take responsibility if you do it. Can you ride the bike without holding on to the handlebar? That's a test of frame geometry. Don't go too fast. Don't do it if you don't know what you are doing and once again, I do not take responsibility if you get hurt.

I used to ride English bikes no-hands, but I never trusted my Radrunner that much. To see how the handlebars moved on bumps, I used a variation, not touching the bars but keeping them within rings formed by my thumbs and fingers. That's how I discovered that on bumps, they jumped aft more than up, relative to me. In other words, bumps made me lurch.

An experience at 10 psi is a reason I won't ride that bike hands free. When it snowed, I had to reduce the pressure that much to keep the tires from sliding sideways. On bare pavement, that made the bike treacherous. If I leaned slightly to turn right, the flattened front tread would contact the pavement farther to the right than normal. That would pull the bars right. My inertia would pull me left, relative to the bike. That would tip the bike left. The flattened tread would contact the pavement farther left than normal, pulling the bars left. I could have gone into severe oscillations.

I now believe low tire pressure is the cause of Diennard's wobble. Low pressure might also cause the stationary bike to seem to flex.

Radrunner got sued after a 15-year-old passenger died of head injuries although helmeted. The 15-year-old driver said they were coming down a steep hill, and it would oscillate violently every time she braked. A dealer was quoted saying that in the industry, the Radrunner's front brake mounting is known to be unsafe. I don't understand.

I think the company is more blatantly at fault. In the EBR video, the editor and the CEO each bragged about riding with low pressure for comfort. Then the manual tells the buyer he must maintain the pressure on the sidewall for safety, but it doesn't say what that pressure is. The CEO knew his flashy fat-tire design was very uncomfortable, so he encouraged customers to ride with low pressure, and the manual shows he knew it was unsafe.

With inadequate pressure, going down a steep hill would have flattened the front tread more. Braking would have flattened it even more, and the front brake would have made the side-to-side pull violent.

Lawyers made age the issue. Somewhere, Radpower says kids under 16 should not drive an ebike, and the plaintiff's lawyer said the warning is too inconspicuous. In effect, Rad lawyers were telling jurors to blame the parents for neglecting to read the fine print. Really? Would an older rider have realized that contrary to the video, inadequate pressure could cause a fatal crash? Would a rider of 16 or 66 have realized in time that the solution was to use the back brake only, and known in time which lever that was?

I'd ridden my Radrunner every day for a year before I discovered that reduced pressure was potentially lethal.

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Wobbly Wheels