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?
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.
Thanks BBB. I'll get it checked out.
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.
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.
Please see my post here:
https://www.radowners.com/index.php?topic=1733.0
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.
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.
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.
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 ;)
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.
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.
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.
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.
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.
Quote from: handlebar on October 25, 2022, 04:42:36 AM
A dealer was quoted saying that in the industry, the Radrunner's front brake mounting is known to be unsafe. I don't understand.
Thanks for your tips in your full email.
I don't take a position on the lawsuit - just my thoughts on this sentence.
I think when the brake is behind the front axle, ●when you apply the front brake going forward●, it tends to pull the front axle away from the fork. The front axle may be loose because of user error or the neighborhood kid decided to play a bad joke on you. Bad things happen when you lose the front wheel. Conversely, ● when you apply the brakes going backwards● it tends to wedge the front axle deeper into the fork. In other words, even if the neighborhood kids completely loosen the front wheel bolts, if you brake going backwards, the wheel is not coming off the bike. This situation would occur say you are going uphill and stopped and the bike wants to slide downhill backwards.
<<Please don't ride with loose axle bolts. I am just saying as an example - a hypothetical.>>
Therefore, according to some way of thinking, it would be safer putting the brake pads in front of the front axle because when you brake going forward, which is most of the time, the axle would be pushed up into the fork and you don't have to rely on the front axle bolts to work.
<<Side story. It is an interesting design in cars because it has been used for an anti-dive system. If the brake pad is behind the car, the harder the car brakes, the harder the front would be pushed up, countering some of the front-diving tendencies of a braking car. This does not apply to bicycles because of the simple fork design.>>
Many bikes have brakes like Rad. My guess is that it is a design decision for simplicity - which may be a safety feature in itself.
Putting the brake pads in front would increase the chance of damage (e.g., in a crash) and possibly make the cables longer and make the design heavier, and complications increase the risk of failure due to damage or bad maintenance.
Just my guess of the answer. I don't know if this is a good argument and it is easier to say after the fact. For example, having a welded on non adjustable seat and handlebar is probably safer too. Getting rid of all bike front racks and backracks would make the bike safer. It goes on and on.
Quote from: Eric7 on October 25, 2022, 07:17:41 AM
Quote from: handlebar on October 25, 2022, 04:42:36 AM
A dealer was quoted saying that in the industry, the Radrunner's front brake mounting is known to be unsafe. I don't understand.
Thanks for your tips in your full email.
...
<<Please don't ride with loose axle bolts. I am just saying as an example - a hypothetical.>>
...
I like your theory about the crash. I didn't go into oscillations with underinflated tires, so I can't say for sure it could have happened.
I believe quick-release front wheels were developed for racers, whose very light front wheels were often damaged. A standard English bike came with a bag hanging on the back of the saddle. It was big enough for a lunch or garment. It came with a sheet-metal wrench, maybe 3mm thick, with holes for the various hex fasteners on the bike. Boxing instead of spanning would prevent rounding off fasteners. You could count on having it because there was only one piece to avoid losing, and it wasn't much good for other applications. That wrench made wheel removal quick and convenient.
I think quick-release axles are a disservice to most riders in terms of convenience as well as safety. Adjustment requires trial and error and may still not be as secure as using a conveniently small wrench. Both ends clamp simultaneously, and I can't be certain that both were fully seated at that instant. I wish it were feasible to retrofit front axles with nuts, like rear axles.
Quote from: handlebar on October 26, 2022, 05:44:03 AM
I think quick-release axles are a disservice to most riders in terms of convenience as well as safety. Adjustment requires trial and error and may still not be as secure as using a conveniently small wrench. Both ends clamp simultaneously, and I can't be certain that both were fully seated at that instant. I wish it were feasible to retrofit front axles with nuts, like rear axles.
I agree with you. Thank you for your insight.
Just adding a qualifier. I took 2 years of physics in college and got good grades. I apologize if I over simplify below but it makes the discussion shorter.
When quick release was first introduced, the brakes were at the rim, at the top. When the brakes were applied, the wheel axle were pulled ●backwards●, roughly 90 degrees to the fork opening which was pointed down. So some problem but not much even if you forgot to use the quick release - I know from experience by being stupid as a kid. <<please don't try this, you will get hurt>>
When the disc brake pads were put behind the front wheel axle, the axle were pulled ●down● during braking in the same direction as the fork opening (down), causing problems as I described. So the rules changed. If you forgot to tighten the front axle you will hurt yourself.
A further problem is the disc brake pads were so close to the axle and cause a force multiplier effect. If the braking was 100 pounds say, where the rubber meets the road, the braking force on a rim sidepull brake would be say 110 pounds and the force on the front axle would be about 110 pounds because the rim is in the interior of the wheel. With modern disc brakes, the brake pad may be only 1/3 of the diameter of the wheel or maybe 1/4 so the force is multiplied 3 to 4 times. Once again, if the force was 100 pounds where the rubber meets the road, the force on the disc brake may be 300 to 400 pounds and the pulling force on the front axle would be also 300 to 400 pounds down in the direction of the opening causing great demand on the integrity of the quick release lever. About 3 to 4 times the demand of a traditional quick release. And if the bike is 70 pounds and loaded with a passenger, maybe 5-10 times the demand of a traditional quick release on a racing bike.
You can do a thought experiment to see this is true. If you are trying to stop a spinning tire on a stand with no brakes, it is much easier to put your hand on the rubber. It will take 3-4 times the effort/hand strength/pressure to try to stop the wheel by rubbing against the disc brake only.
Quote from: Eric7 on October 26, 2022, 01:27:43 PM
Quote from: handlebar on October 26, 2022, 05:44:03 AM
I think quick-release axles are a disservice to most riders in terms of convenience as well as safety. Adjustment requires trial and error and may still not be as secure as using a conveniently small wrench. Both ends clamp simultaneously, and I can't be certain that both were fully seated at that instant. I wish it were feasible to retrofit front axles with nuts, like rear axles.
I agree with you. Thank you for your insight.
Just adding a qualifier. I took 2 years of physics in college and got good grades. I apologize if I over simplify below but it makes the discussion shorter.
When quick release was first introduced, the brakes were at the rim, at the top. When the brakes were applied, the wheel axle were pulled ●backwards●, roughly 90 degrees to the fork opening which was pointed down. So some problem but not much even if you forgot to use the quick release - I know from experience by being stupid as a kid. <<please don't try this, you will get hurt>>
Ah, rim brakes! I think it was in 1919 that cars in America became as popular as bicycles. In the preceding 20 years, bicycle periodicals urged riders to get brakes, which a lot of riders eschewed. On this side of the ocean, brakes were coaster brakes. They could fail on hills. When Schwinn eventually came out with something that looked like an English bike, it had only a coaster brake. Swept-back bars were the fashion offered by American companies, and maybe that would have made a front brake dangerous.
As a teen, I lived at the bottom of a thousand-foot, 10% hill on US 4, with a traffic light at the bottom. Coming down that hill in pouring rain, I'd pull the levers very hard, knowing that eventually the rubber pads would dissipate the film of water and take hold.
I took physics in 11th grade. The teacher told my father I was brilliant. That was a feather in my father's cap, but to me it was weird. How could I be brilliant at was essentially grade-school math? There were several boys in my class whom I found just as capable.
That class was one of my few chances to associate with kids not in my designated group. In grade school, all the boys my age had been friends. The only worthwhile part of school was the playground:after breakfast, after lunch, and two recesses each day. They say Facebook is bad for mental health and I agree. As in a classroom, a remark you make to somebody is really putting on a show for the audience. On a school playground, you could chat freely. Playground segregation meant we didn't know the girls well. Starting in 7th grade, we were segregated into 6 classes. I didn't know any of my classmates, and without a playground, we couldn't bond as kids had in grade school.
Without Physics, I would never have met Doug, the only other kid in the school who could be seen on a bike. (I didn't blame the others for never riding. They owned Schwinns.) He sometimes rode his Huffy 4 miles to school. He had to climb 1100 feet to get home. At the end of the school year, we rode on an overnight camping trip. Looking back, I don't know how we managed to schedule it. "Lord of the Flies, which the author said misrepresented what boys were like, was treated like required reading. Parents and teachers considered boys a bad influence on each other, so home visits were discouraged, and we were overloaded with homework, organized activities, and employment.
During those 24 hours, we didn't talk or act differently from at school, but the absence of an audience made a big difference. Big Brother wasn't watching. A friend is someone with whom you can be at ease, and we were at ease.
Speaking of physics, another problem with disk brakes that I don't see discussed much is they can be way harder on spokes and rims than rim brakes. When the brakes grab the disk, the breaking force has to be transmitted through tension in the spokes out to the rim and tire. Rim brakes do stress the spokes some but nowhere near as much. I have seen several rear disk rims where fatigue cracks have grown out of the holes on both the drive and non-drive side of the rim. With rim brakes, the only fatigue cracks I have seen in the rims have only been on the drive side.
Quote from: Roverdrive on October 29, 2022, 07:11:42 PM
Speaking of physics, another problem with disk brakes that I don't see discussed much is they can be way harder on spokes and rims than rim brakes. When the brakes grab the disk, the breaking force has to be transmitted through tension in the spokes out to the rim and tire. Rim brakes do stress the spokes some but nowhere near as much. I have seen several rear disk rims where fatigue cracks have grown out of the holes on both the drive and non-drive side of the rim. With rim brakes, the only fatigue cracks I have seen in the rims have only been on the drive side.
I found an article about the choice between rim and disk brakes. It said disk brakes have more stopping power. I wondered why, since my disk brake operate on 1/3 the rim radius.
In stopping power, I think the rim brake's Achille's heel is the distance between the pads and the hinge bolt. The distance may be reasonable on a road bike, but an ebike will probably have bigger tires, entailing longer arms and more leverage to bend arms or hinge pins. Ebikes may have more weight and speed, but rim brakes would have to be designed for less braking force.
I think the smaller diameter of the disk rotor is offset by how much force the pads can exert on the breaking surface. Most road bike rims are relatively thin, and all of the higher end ones are aluminum (or even carbon). They tend to use only mildly abrasive pads to reduce wear as thinning of the breaking surface can mean rim failure. If rim brakes used similar pad materials and forces as disk brakes, rim life would be severely compromised. I worked with a guy that used to "ride" his brakes all the time and he seemed to go through a rim a year!
Well this post has gone off topic quite a bit.
My RadCity 5 Plus StepThru still has a low speed wobble that can initiate a whole-bike shimmy. It is not headset looseness, fork softness, spoke tightness, tire pressure or tire bead location. It has been to 2 bikeshops and 2 bike mechanics. All agree it is a combination of front for bridge and headset angle : in other words it is baked into the very geometry of the bike itself. My partner and I have each fallen off it twice in traffic and will no longer ride it. This is a dangerous bike.
As I stated in the link I posted previously, my Step-through Radcity 5's wobbles were cured by replacing the OEM tires. I have ridden it at 40mph downhill since then without issue. It is quite stable at speed as long as you don't mind the coefficient of drag close to 1... it feels like I have a parachute on compared to my road bikes. I don't think it's possible to exceed 40mph unless you throw it off a cliff.
DrSmile, I remember that post and that's a good reminder. If your bike has a wobble, vibration etc and everything checks out then perhaps change the tires. Purchase good quality tires as it's potentially the last thing to look at and not overly expensive. It may solve the problem as it did for you.
If the wheel is not true, meaning it's not perfectly straight and round, your bike wheel may wobble (https://biketoworkday.us/why-is-my-rear-bike-wheel-wobbling/). This can result from a bent rim or loose spokes. Inspect the wheel for visible deformities and have it trued by a professional if necessary.
Wow, lots going on in this thread! Most of the wobble in bikes is due to loose tolerances or improper assembly, but this bike has been apparently reassembled by pros. The most likely suspect is the front suspension fork, and I've seen this on other brands as well. A quick check is to hold the handlebars in the normal riding position with your feet on the ground, hold the front brake only, and rock the bike back and forth. A suspension fork with loose tolerances internally will look ok on the outside, but the sloppy movements on the inside will contribute to wheel or frame oscillation at certain speeds. If your front fork seems loose in this test, take it back to the shop to have them confirm, then they may recommend a replacement fork.
Regarding tire pressure, there's low pressure compared to normal tires, then there's low pressure that's far away from the recommended pressure for that specific tire. The K-Rad tire Kenda makes for a lot of Rad bikes is made for 30 PSI and it's printed right on the tire. 10 PSI is way out of range. 16 is the extreme minimum, and that should only be used in extenuating circumstances like ice. On bare pavement at 16 PSI, handling and safety will be affected. The minimum pressure I will use on pavement is 18 PSI, and my normal pressure is 20 to 22 PSI because of the horrendous sidewalk cracks and tree root issues where I often ride. It should be noted that K-Rad tires, even at 20 PSI, are stable up to 40mph, so I don't think there is a safety issue with Rad tires that would cause a crash... unless the tires are underinflated due to a leak, ignorance, or lack of maintenance. All bikes are unsafe if the tire pressure is too low.
The front brake issue does not apply to Rad bikes, and was a "try anything" attempt by the lawyers to place blame. When disc brakes were first went into use on bicycles, the quick release lever had enough travel to actually get caught in the brake rotor, causing serious crashes. This is impossible with Rad's design, and the most obvious way to demonstrate it is to bring a rad fork and wheel into the courtroom and have ANYONE replicate the lever/rotor interference issue. It just can't happen. I feel sorry for the loss of a child, but responsible parents would not have let them ride a powered vehicle they were not old enough for, especially if it was not in proper working order. One of my kids got a used pedal bike last week, and we spent an hour making adjustments and corrections before I let her get on it.