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Suspension on cargo bikes

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Suspension on cargo bikes

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Old 02-08-18, 09:57 AM
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Saale
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Suspension on cargo bikes

Alright fellas, I need a little helping out with my thinking here.

Generally suspension improves ride comfort for occupants of any type of vehicle, and I know as a rule of thumb that in cars the less unsprung weight (wheel assemblies) there is, the less it'll upset the handling (important for building a sports car, hence why some people are obsessed with finding particularly light wheels).

Yet most cargo bikes I've seen in my life have been fully rigid, and even the rare exceptions only had front suspension with little travel. What gives? Is there something I'm missing about having a lot of cargo weight on a bike with suspension (beyond needing appropriate spring and damper settings)? Something about it being two wheeled, creating different vehicle dynamics than a four wheeled vehicle? Something about the ratio of vehicle weight to cargo weight?

What's the deal here?
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Old 02-08-18, 11:05 AM
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fietsbob 
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#1 what is the load how heavy is it and where are you moving it, and why?


My Dad had Air suspension spring compensation for when the car had a trailer on it, a heavy rubber air bag inside the coil springs..

in the early 60s..


heavier load? more axles and wheels .. seen a "bike" moved piano stage, In your Berlin , I think it was.. 10 wheels .. Power from 3 people.

the stage had a concert Grand piano, for it's player, on it,
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Old 02-08-18, 12:33 PM
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Saale
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I don't have any specific application in mind, I merely investigated cargo bikes out of interest lately and the question came up in my head.
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Old 02-08-18, 01:18 PM
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I think one of the differences is speed, so there is a huge difference between riding at 5 to 10 MPH than driving at 50 MPH.

Now, E-Cargo bikes, of course, bring in a mid speed of 20 MPH or so, perhaps even faster if given a very hot motor.

Tires also give a fair amount of spring.

There has been a discussion about springs in the Clydesdale subforum. At least many off the shelf spring systems aren't designed for 300 to 400 bikes/riders.

As a cyclist, I'm also pretty good at avoiding bumps (in part due to experience with pinch flats).

Anyway, I'm not sure if the springs are necessary. Perhaps if one is moving to a 3-wheel trike giving a lateral component to the bounces which could affect control.

Of course, there are springs in seatposts, handlebars, and etc. Perhaps easier to configure the springs to a rider, rather than compensate of a dynamic load of 0 to 500 lbs or so.

And, of course, weight. Even for for cargo, adding extra weight to the system may not be desirable.

Here were some photos of a cargo bike meet someone posted earlier, some bikes with suspension.
https://www.bikeforums.net/utility-c...-nijmegen.html

Anyway, in the future, we'll likely see a mix of some bikes and trikes with suspension, some without.
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Old 02-09-18, 05:06 AM
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Saale
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Alright, so I've found a piece of infovertisement by manufacturer Riese & Müller. They offer a long john with full suspension and their website says that "only E-bikes with full suspension can maintain optimal traction on bad roads and ensure rider control". Better road handling and safety at high speed and on bumpy surfaces, protection of the cargo from shock and vibration. Sounds plausible from a physical standpoint to me.

Now as I've come to learn these Riese & Müller bikes are laughably expensive (the long john starts at 5k) and have been compared to being the Porsche of the E-bike world, so I'm thinking that maybe it's simply been a cost issue in the past and that a lot of manufacturers went with a rigid design to be able to market their bikes at a more customer friendly price point. Maybe that's all there is to it. Am I on the right track here?
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Old 02-09-18, 06:19 AM
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Bikes at Walmart have suspension. Cost isn't the only factor. Now, Walmart suspension may not be the best for a 500 pound load. One could build a bike with a double rear MTB spring to get fairly good spring for heavy capacity. Perhaps a bit different design on front if one is using off the shelf parts. But, it would be easy enough to spring the head tube independent from the rest of the bike. Hmmm, it looks like Riese & Müller is springing the fork. Which then means a pretty custom fork if done right. Anyway, I doubt cost is the only factor.

As far as safety. I don't know. I've never felt bumps made me unsafe.

Ahhh... you're in Germany. I'm in the USA. Things may be different. Do you have cobbles? They're rarely used here. So, most of the riding would be on pavement. Yeah, they'll be bumps, but nothing that one shouldn't be able to handle.

The only advantage that I can really think of is that it might protect the bike slightly. Say you're running along and hit a 2x4. Without suspension, the front of the whole bike, then the rear will have to be lifted, travel over the 2x4, then return back to the previous position. That sudden jar may be hard on a bike with a heavy load. On the other hand, hit the 2x4 with suspension, and much of the difference will be taken up by the suspension, and the load more or less maintains the former place/momentum.

Anyway, a quad would more or less require full suspension so the wheels can stay on the ground when going over bumps.

A trike would be less prone to one wheel bouncing off the road and losing traction.

A bike even less so.
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Old 02-09-18, 07:28 AM
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The fork is a Suntour XCM32 according to R&M. Not sure if it's a particularly heavy duty model or adjustable.

We do have a lot of cobbles in Germany. In fact I think about 40% of my 2 mile work commute are cobbles. I'm thinking the suspension would also help keep the bike controllable. A rigid bike bounces a lot when you go over bumps or curbs, and when loaded this could cause loss of control or of course damage to the bike, at least more easily than with suspension.
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Old 02-09-18, 10:05 AM
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photobucket fails me again. the cargo bike i made had full suspension, but the pics in the homemade xtrarcycle thread are gone (i keep saying i'm going to switch to imgur, but i broke my camera too. once i finally pick up a new one i'll get more serious about it).

i'll admit though i just like making bikes and didn't use it much before i gave it away, but i liked it and the bits and pieces for future cargo bike projects are all full suspension ideas.

edit: kinda blurry and not much suspension detail shown, but cheating photobucket to show it.


https://www.google.com/search?q=carg...=1518192384885

Last edited by Philphine; 02-09-18 at 10:09 AM.
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Old 02-11-18, 12:56 AM
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I can think of a couple reasons you don't see suspended cargo bikes: 1) Cargo bikes are already a very niche product in a very niche category. If you think about what percentage of all bikes are purpose built cargo bikes, then you can understand that the reduced demand makes it prohibitive for a broad range of manufactures to produce them at an affordable price. That being said, a cargo bike with all the bells and whistles (read suspension) would put it that much further out of reach. Consider the difference in cost between a fully rigid mtb and a full suspension mtb. You may see that with the high cost of currently available rigid cargo bikes, the added cost of a full suspension cargo bike would be outrageous for most people who would actually want/use one. 2) Likening a cargo bike to a much larger, faster, and heavier machine in terms of suspension applications is an unfair comparison. If you think about the suspension in a car, typically it only has to manage a range of about 10-20% added cargo weight above that of the vehicle itself (e.g. a 4000 lb car with 400-800 lbs of cargo. And most people don't have to get their suspension tuned in their vehicles because the ratio of added weight to base weight is so small and the suspension can handle it just fine. A bicycle, however, is a very different situation. Most bikes, even cargo bikes, don't weigh more than 50-60 lbs while most cargo bike riders (plus cargo) don't likely weigh less than 150 lbs. You can see that with bikes, the ratio is inverse. The cargo weighs much more than the vehicle. Designing a suspension that can appropriately accommodate such a huge range of loading would be very difficult and expensive, and a poorly tuned suspension in that case could actually be very dangerous, creating tremendous instability. You would have to adjust your suspension (as is done on quality mtbs) depending on the weight of the rider plus the load. And because cargo bike can have a load fluctuation of 100-300 lbs, any simple/conventional suspension system simply could not properly accommodate that wide range with respect to the weight of the bicycle.
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Old 02-11-18, 07:44 AM
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The classic cargo bikes I know always had leaf springs. But it would take quite a heavy load to put those to use. There's also a bit of spring in the wheels and the frame, and of course in the tyres, with more weight of the bike itself.

I think that if you want to design a suspension that brings comfort at any load you'll have to do a very thorough job. I don't think you want a cargo bike and certainly not an electric cargo bike that feels comfortable and safe at high speeds but isn't.
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Old 02-11-18, 06:25 PM
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There is German costs then there is Chinese costs.. so work does tend to seek the best cost..

Taiwan has gained a lot of the bike business..
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Old 02-12-18, 12:27 AM
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Originally Posted by Saale View Post
Generally suspension improves ride comfort for occupants of any type of vehicle, and I know as a rule of thumb that in cars the less unsprung weight (wheel assemblies) there is, the less it'll upset the handling (important for building a sports car, hence why some people are obsessed with finding particularly light wheels).

The tire is the suspension.

The mass of the tire that deflects is the unsprung mass.

The remaining mass of the bicycle and load system is the sprung mass.
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Old 02-12-18, 10:15 AM
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I removed the short travel hybrid 700c fork from my Fuji Crosstown xtracycle conversion, replacing it with a steel suspension corrected fork. Handling improved and weight dropped. Safety and speed over comfort. A fully suspended cargo bike would feel unsafe, IMO. Fat tires and an eye out for potholes are good enough.
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Old 02-13-18, 06:27 AM
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Originally Posted by Philphine View Post
photobucket fails me again. the cargo bike i made had full suspension [...]
Really interesting looking construction, so you basically stretched a Y-frame MTB and added a rack directly to the frame with the free swinging rear wheel underneath? Looks like both wheels remained 26", correct?

Originally Posted by urbanescapee View Post
I can think of a couple reasons you don't see suspended cargo bikes: [...]
I understand your concern on a mechanical level, and you would have to tune the suspension for a full load instead of an empty one, leaving it very stiff when empty, but if a well tuned full suspension makes a loaded cargo bike more controllable then surely it's worth a consideration, costs notwithstanding.

Originally Posted by Stadjer View Post
The classic cargo bikes I know always had leaf springs. But it would take quite a heavy load to put those to use. [...]
That's kind of what I'm thinking. Well balanced when loaded, stiff when empty, but potentially preferable to stiff all the time.

Originally Posted by hermanchauw View Post
The tire is the suspension. [...]
By that logic a motorcycle tire is the suspension, but I wouldn't trust a motorcycle or even a scooter with welded springs with my life.

I mean, I'm aware that there's a great difference in weight between an empty cargo bike and a loaded cargo bike, and that you can't possibly tune the suspension for all scenarios, but by my understanding of physics and engineering a suspension adjusted for load would leave an empty cargo bike almost like a rigid bike, but improve loaded ride comfort and ride safety, wouldn't it? I'd allow reality to prove me wrong if I ever come across an occasion, but I'd be shocked because in my head the suspension pretty much makes sense.
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Old 02-13-18, 10:26 AM
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Originally Posted by Saale View Post
Really interesting looking construction, so you basically stretched a Y-frame MTB and added a rack directly to the frame with the free swinging rear wheel underneath? Looks like both wheels remained 26", correct?
yes, that's about it. a bike I got for about $10-15 and it just looked like it could be stretched. I really liked it, but gave it away 'cause I needed the garage space, plus like I said, I'm playing with other ideas. all but one (a little 20/16" crumbpicker idea) have suspension in the plan.
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Old 02-21-18, 12:35 PM
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Originally Posted by Saale View Post
By that logic a motorcycle tire is the suspension, but I wouldn't trust a motorcycle or even a scooter with welded springs with my life.
There are quite a lot of hardtails produced, not putting the saddle close to the unsprung wheel helps. Just like cars with a long wheelbase are more comfortable.

I mean, I'm aware that there's a great difference in weight between an empty cargo bike and a loaded cargo bike, and that you can't possibly tune the suspension for all scenarios, but by my understanding of physics and engineering a suspension adjusted for load would leave an empty cargo bike almost like a rigid bike, but improve loaded ride comfort and ride safety, wouldn't it? I'd allow reality to prove me wrong if I ever come across an occasion, but I'd be shocked because in my head the suspension pretty much makes sense.
It does make sense, last year someone posted a picture of a cargo bike with double whisbone front suspension, which is quite sophisticated. But that was a very expensive cargo bike. Hydropneumatic 'springs' like in old Citroens would be ideal, because it's extremely progressive and hardly sensitive to load, but that's probably not doable.
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Old 03-23-18, 02:15 PM
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I think the added weight and cost have most manufacturers not going this route
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Old 04-03-18, 03:52 PM
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I has suspention on one of my early long tails. it was always bottomed out or mostlly compressed because the weight pushing down on front. but it wasnt a fancy fork so yeah
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Old 04-06-18, 06:11 AM
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Originally Posted by Baiku View Post
I has suspention on one of my early long tails. it was always bottomed out or mostlly compressed because the weight pushing down on front. but it wasnt a fancy fork so yeah
Was it an effect of the design in particular? Because when I'm thinking of longtails it seems like the load area is pretty well centered on the rear wheel, or only slightly offset to the front, but surely making no more of a difference on the front suspension than a 20 kilos heavier rider.
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Old 04-06-18, 03:33 PM
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It was one of my home built longtail ones. though my xtracycle radish died and just now im rebuilding on a norco frame, before removing the suspention fork im gonna try it.
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