Is the frame type (diamond, step-trough) still relevant for stability

Skelshy

New Member
I'm on the heavy side, plus I often have a kid seat mounted on the bike which makes it much harder to swing a leg over the bike to get on it. I was wondering if a diamond frame is still needed for stability (it used to be step-through bikes were all wobbly)? If no, I would just have an easier time getting on and off the bike in the city with a kid with a step-through design.

Opinions?

Thanks
 

indianajo

Well-Known Member
I'm carrying 170 lb me and up to 80 lb supplies on the step through frame left. I bought that one because it is special for short people. My pants inseam should be 28". It is a yubabikes.com .
No wobbles. This is not a racer, weighed 63 lb as delivered and rides about 75 now with full set of tools, tubes, bags, battery, motor.
Other stretch cargo bikes, xtracycle, surlybikes (steel frames high capacity), pedego stretch, radwagon, blix packa, the original kona ute, tern GSD (20" wheels) . these put the rider's weight on the front wheel and leave more of the rear tire for the cargo. Many have special features to interface with certain brands of child seat. Mine has spoke shields standard to keep the child's fingers from being pinched. Look into the double leg frame, makes loading much easier.
See this topic about cargo bikes, which usually have a weight rating. https://electricbikereview.com/forums/forum/cargo/
I've converted my pedal bike with a front drive geared hubmotor $221 and $620 for a 17.5 ah battery that doesn't have a patented shape or connector. So I can buy any generic battery in 4-6 years when this one wears out. Likewise if the motor craters, a new one is about $250 with drive, throttle, PAS, brake handles.
The yuba was perfect when I got it, needed no spoke torque checking monthly that rad specifies, and I got 5000 miles out of the 8 speed chain since the motor doesn't drive through it. Sprokets no wear yet. The front drive is not a problem, plenty of traction. I don't ride on black ice. I do ride year round, don't run a car anymore. do all my shopping off the bike.
See you are in Germany. Reise & mueller sells an expensive & respected cargo model both in Europe & the US. Bosch mid drive wears out chains more like 1000 miles, and pedals without power like dragging an anchor. I've ridden mine home 25 miles unpowered when a heavy rain disabled the throttle. I ride unpowered 90% of the time, reserving motor for headwinds >12 mph, trips over 25 miles, and crossing 6 lane streets on 6 second green lights with the throttle to the max.
 
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TMH

Well-Known Member
While full diamond will likely continue to be the most solid/rigid, I believe that in general the improvements in frame design and materials (especially things like hydroformed tubes which allow more structural rigidity when required) make many of today's step-thru's less flexy than previous generations.

Different bikes also are designed for different overall weight carrying capacities. The ones with the highest carrying capacity, if choosing between step thru's by different manufacturers or even just different models from the same manufacturer, will generally be the stiffest.

Different designs choices will also improve rigidity. For example, when I have ridden my wife's Ride1Up step thru, I can definitely feel frame flex. It's frame looks like this, with an extremely low step over height:

700-Series-ST-BlueSteel-Side.jpg


However a design like Specialized chose for the Turbo Vado/Como uses an extra bar which results in a higher (but likely still very comfortable) step over height, but much less frame flex:

i-KmnH3S2-XL.jpg
 

Timpo

Well-Known Member
I'm on the heavy side, plus I often have a kid seat mounted on the bike which makes it much harder to swing a leg over the bike to get on it. I was wondering if a diamond frame is still needed for stability (it used to be step-through bikes were all wobbly)? If no, I would just have an easier time getting on and off the bike in the city with a kid with a step-through design.

Opinions?

Thanks
I don't know what step thru bikes you're talking about, but I'm assuming you're not trying to do anything super crazy since you're carrying a kid.

Downhill MTB racers, trial bike racers, Redbull Rampage Championships, etc.. yeah athletes competing in those races demand very rigid frame and they can actually feel the difference.

I've ridden a few ebikes with step thru design, they sure feel different, mainly because of handle bar position and all that, but in terms of flex and rigidity, did I feel the difference? Oh heck no. At least not when I was test riding it around the block.

Maybe a little bit, if I try to do hard braking and jump down the stairs, but as far as riding normally on the road? No.

You're worried about compromising your safety by getting a step thru bikes, because they flex more. I don't think that would be a problem if you're just riding normally like most people.
 

Stefan Mikes

Well-Known Member
Region
Europe
City
Brwinów (PL)
The modern step-through frames made of hydroformed aluminium are very stable, especially with the top tube adding to the structural stability. I was 107 kg (236 lbs) when I first started riding e-bikes, no issue with the stability. Many manufacturers offer lifetime warranty on the frame, meaning they are sure their frames are durable.
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Timpo

Well-Known Member
I really don't think diamond frame is necessary.

Have you ever seen Honda Super Cub and CT125?

They can go 60mph, carry lots of weight, or passengers, for many miles.

Guess what, the frame is one piece pipe.

スーパーカブ50 フレーム C50-0281

プレスカブフレーム 1

新車・中古バイク購入・バイクを買う | 新車バイク・中古バイクの販売 ...

off-road Archives - Asphalt & Rubber

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Dewey

Well-Known Member
Frame flex or speed wobble is still an issue on some ebikes, Court's video reviews sometimes demonstrate this, for example on the Pedego City Commuter step-through here
But as others have pointed out it varies between different designs so test ride before you buy.
 

Timpo

Well-Known Member
Frame flex or speed wobble is still an issue on some ebikes, Court's video reviews sometimes demonstrate this, for example on the Pedego City Commuter step-through here
But as others have pointed out it varies between different designs so test ride before you buy.
I am not convinced about this.
I think Court didn't know the possible cause of wobbles.

Although I'm not an actual mechanic, I have been riding motorcycles and working on motorcycles for a long time and consider myself as an amateur backyard mechanic, and I know and talk to many mechanics, watched tons of YouTube videos, articles on Google, etc.

Anyways, the speed wobble that he's talking about is a very common problem.
There are several possibilities.

- poor quality or broken steering head bearings.
- poor quality or broken wheel bearings (in ebike's case, hub bearings), worn out or defect axles
- misaligned rim or spokes out of true
- wheel weight & balance is off

Just by watching the video, the first thing I suspect is wheel wight & balance.
Is it not common for bicycles to check weight & balance, when changed my tire, I noticed that ebikes do not require weight and balance, so I did a research and found out why, mainly because in most cases, it is not necessary for bicycles.

Notice the reflector on the spoke? Something like that is definitely a cause of wheel going off balance.
Considering even for motorcycles, how we adjust less than 1 gram of error, that plastic reflector easily weigh something like 10 grams.
Even a lower speed, that could easily cause speed wobble.

If I was there, and if Court was complaining about speed wobble, I would ask him to let me check the bike, I will make sure the bearing and axle are in good condition, I will realign and make sure the wheel's weight and balance is good, and see what happens.

Look how Court is riding, that's like the most ideal riding condition ever, and he's going slow.
If frame is actually flexing at such low speed, on flat ground, Pedego must have put one crappy frame on that bike.
 

steve marino

Active Member
That Honda Super Cub is drop dead gorgeous. Much nicer than anything being made today or in the last 30 years. Personally, I've never heard of a step thru frame exhibiting wobble or instability on a bike or a motorcycle. Maybe it happens, but in over half a century of riding both, no one I knew of had a lick of trouble w/ this.
 

Timpo

Well-Known Member
That Honda Super Cub is drop dead gorgeous. Much nicer than anything being made today or in the last 30 years. Personally, I've never heard of a step thru frame exhibiting wobble or instability on a bike or a motorcycle. Maybe it happens, but in over half a century of riding both, no one I knew of had a lick of trouble w/ this.
I agree, I've ridden a few step thru bikes and never had a problem or felt dangerous.

If step thru bikes are causing wobble on a flat surface, at slow speed, like that above video when Court was demonstrating, that would be a serious problem. It will probably break if you go over a big bump.

I don't think that wobble was due to the frame, it was something else, most likely the weight & balance of wheel.

I'm a bit disappointed with Court, he really didn't know what he was talking about.🙁
 

steve marino

Active Member
Well, it's a rare day when I know what I'm talking about, but I've learned to fake it pretty well. Like my ex wife used to say, if you can't dazzle 'em w/ brilliance, baffle 'em with BS.