Step-thru wobbles fully loaded

[DrSmile]

I have a RadCity 5 Plus step-thru, and I was returning from my grocery run from (banally bourgeois) Trader Joes with fully loaded rear Ortlieb Panniers when I started to notice a resonant wobble throughout the bike frame when turning the front wheel even mildly rapidly. It feels quite unsafe. This occurs even when almost stopped so it isn't a speed wobble. I checked the wheels, headset and stem and everything is tight. The wobble pretty much goes away if the panniers aren't loaded, so I'm wondering if this due to the geometry of the bike and long steerer (moving too much weight off the front wheel maybe?), an insufficiently rigid fork (it feels better with the fork locked), or perhaps just a side effect of the step-through design? Has anyone else experienced this?

[DrSmile]

I looked into this some more on other forums, and apparently there are two things I hadn't considered that I will try:

1) Make sure the weight distribution in both panniers is fairly equal and
2) Make sure the pannier bags are centered over the rear axle, not behind.

My panniers were neither of those, so I will try to correct and report back.

[Tony]

When I take my grandson to school on the seat on the back rack I get no problem. The seat is centred just a little behind the rear axle.                I also regularly carry a long heavy load on the rack that extends well beyond the centre of the axle, this shows a little of the steering wobble symptoms you describe. So it looks like a more rearward load will cause this.  Hopefully you have it sorted. My bike is a Radmini 4.  Tony.

[Veggyhed]

I have the mini 4 and runner plus which I use panniers on and carry fairly heavy loads with groceries. I've never experienced this problem but I do make sure that the heaviest items are in the bottom of the panniers. I have never worried about one side being heavier than the other however you do notice it while riding but it's never been an issue. I also do have to say the trip to the grocery store for me is 2.4 mi so I'm not traveling that far and I'm on City roads.

Please let us know if those two things sold your problem that you mentioned.

Sent from my Pixel 3a using Tapatalk

[mwillis201]

I have both Step thru 5 P & High Step 5 P:  Make sure your tires are firm and not under-inflated.  You should have 27 x 2.00 or 27 x 1.95 tires. I recommend no less than 63 to 64 PSI. in each tire.   

[DrSmile]

Short version of this post - the problem was the "Rad City" tires

Long version:

I tried again riding the bike with the panniers over the axles and with even weight distribution. I tried different tire pressures. No improvement. At this point I double checked for tightness on the bar, stem, headset, fork, and axles. No issues. I spun the wheels and noticed that the tires seemed to be out of true both laterally and radially, with significant "humping" on at least 2 spots. I proceeded to remove both wheels (rear is pretty easy actually which was surprising). I put the wheels on my truing stand and checked spoke tension and lateral trueness. The front wheel was off a few mm and the spoke tension was fairly uneven but given the spoke count I didn't think that was the issue and I expected some of this as the rims aren't really high end quality. I unmounted both tires and put the wheels back on the truing stand, no radial issues at all. I retrued and tensioned the wheels, but mounting the tires I could see the issue was still there, so it had to be the "Rad City" OEM tires causing the problem. They are anything but round and seem very unbalanced. I had to order replacement tires since I only stock 700c tires, The ones I ordered aren't "pro" tires or anything (Vittoria Randonneur), they are the same size (2 inch) and very similar tread. The stock tires weigh over 1400 grams each (wow!) while the replacements weighed over 900, which isn't light either but that's an improvement of 2.2 pounds just in tires! After re-installation the problem is gone, I can ride fully loaded without any issues. There is a noticeable improvement in ride comfort as well as the bike rolls much more smoothly. Before if I let go of the handlebars the bike would vibrate back and forth uncontrollably even at 5 mph, now I can ride no handed at 25mph (not recommended!) 

[LarryM]

RadCity 5+  For me, front wheel wobble was greatly reduced by installing 2.3" knobbies.  Maybe the wider tire added enough friction to act as a steering stabilizer.  Even without a pannier load the bike now feels steadier.   Just speculation here; could there be an inherent geometry issue with this model bike??  In general, installing 2.3" knobbies sure enhanced handling on dirt & gravel pathways encountered here in the Phoenix, AZ area.   (no I didn't want a RadRover with 4" fat tires)

[david.platt@mac.com]

Did you try locking out the front shock.
O I think you can adjust the firmness too.

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjL8OjrxMn3AhXSWM0KHd2GBNEQFnoECBUQAw&url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DtGl3I0Ez974&usg=AOvVaw3YearcbuHiGl_eXU94MBBp

[DrSmile]

Did you try locking out the front shock.
O I think you can adjust the firmness too.

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjL8OjrxMn3AhXSWM0KHd2GBNEQFnoECBUQAw&url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DtGl3I0Ez974&usg=AOvVaw3YearcbuHiGl_eXU94MBBp

The lockout didn't change anything. The first thing I did when I noticed the wobble was lockout the fork. The fork quality is pretty terrible but I wasn't expecting much given the bike's price. It works well enough.

[david.platt@mac.com]

I get it firmer tires worked. I found these tires and could not help think of your thread.

Kwick Drumlin | K1216 - Cargo 4ply

https://shop.kendatire.com/Kwick-Drumlin-p/k1216.htm

[DrSmile]

Seems this may be a safety issue:

https://www.bicycleretailer.com/industry-news/2022/08/02/rad-power-bikes-giro-face-wrongful-death-suit#.YusCdXbMJhE

I have to wonder whether it was actually the quick release or the tires?