sysrq

For simple bikepacking with triangle bags or ebike conversions with mid drive kits and triangle batteries (stealthiest and safest way for secure attachment) it should be trendy. Most motorcycles use only one type of rear suspension with two shock absorbers attached to seat. Bicycles need adjustable seat height which complicates things.

sysrq

The need for rear suspension increases with heavier cargo on a touring bike at high descending speeds on otherwise smooth roads with unexpected deep potholes.

sysrq

Agreed, the this trend seems weird while knowing that bikepacking is so popular.

Ironfish653

Look more than 10 feet in front of your front wheel and the Road surface will be less of a surprise all the time. On trail is one thing, but on a road intended for motor vehicle use, at bicycle speeds, very little should catch you by surprise such that you can’t try to avoid it.

Bikepacking and touring never really embraced rear suspension. Probably due to the extra weight on an already heavy bike, and the need to have enough adjustment in the suspension to make it handle decently both loaded, unloaded, and in between; along with the need to be able to make those adjustments while on the road, was a complication that so few riders asked for, that nobody really put one into production; outside of a couple boutique manufacturers.
It’s not that the technology isn’t there, there’s just so little demand for it, that it never really made mainstream production

MTBs , on the other hand, embraced suspension, and as it developed over the last three decades, to improve performance, (without regard for cargo racks) the shape of the frame moved away from the touring-bike based designs of the 1980s ATBs.

Yan 

Because people want to use dropper seatposts to get the saddle low, so they don't get anally impaled when they ride technical terrain and do jumps. That's the purpose of a full suspension bike. Nobody in their right mind is attaching a freaking rack to a full suspension mountainbike.

Bikepacker fashion has moved to gravel bikes.

PeteHski

Yeah if I was bikepacking I would definitely choose a gravel bike over a full suspension mtb. If gravel bikes don’t need rear suspension then I don’t see why a tourer would either.

cyccommute 

A smaller rear triangle shouldn’t have any impact on the rear rack nor the space available. The bikes below all have rear racks but the size of the rear triangle varies greatly.

This is a 58cm bike


A 19” mountain bike with 26” wheels.



This is a 43cm frame with 650C (571mm) wheels



Another 43cm bike with 700C wheels.



And this is another 43cm frame



Smaller frames are a little harder when it comes to mounting the rack but the size of the frame doesn’t change the size of the rack nor the frames ability to carry stuff.

cyccommute 

“Unexpected deep potholes” are rather rare on smooth roads and full suspension isn’t needed for most (if not all) smooth road touring. Off-road bikepacking is a different beast but the equipment is carried differently there as well.

big john

Most of the motorcycles I have had use a single shock with a linkage, like this 40 year old model.

Modern full suspension mountain bikes use designs similar to motorcycles, single shock with different types of linkages and different amounts of travel. This KHS has 150mm rear travel.

This bike has a 125mm travel dropper seatpost but droppers are available up to 200mm for bikes that can accommodate them. Since I don't jump or perform aerial moves the dropper helps by lowering my COG for steep descents and cornering.

sysrq

There was also a Shockster made for those who like to modify their bikes constantly, but as I'm aware it was made for bikes with V brakes and 26" wheels only. Probably there is a way to attach it directly to seat stays using clamps or weld some V brake studs on, but nobody is talking about it

PeteHski

I just looked that device up and I can see why nobody is talking about it.

Trakhak

Thanks for mentioning the Shockster---never heard of it. In fact, most people have probably never heard of it, so it's not surprising that they're not talking about it.

It's been out of production for many years. Here's one review I found (in fairness, the evaluation is based on its use off-road rather than with a touring bike):

"STRENGTH:Turns a hardtail into a F/S bike - NOT!

WEAKNESS:Adds 3lbs. weight to rear of bike and 3" of wheelbase, resulting in a heavy, sluggish-handling hardtail.

Put this on various steel and alu hardtails at the bike shop and riding them back in the day. On the trail the added weight of the Shockster (all over the rear wheel, btw) radically alters the balance and center of gravity, making climbing a real chore. The longer wheelbase caused by adding the Shockster results in a sluggish steering bike that is a bear on singletrack. Travel I found nowhere near claimed (3 inches). Full-suspension bikes are so much better balanced, and handle so much better it is a crime to compare them to this thing. The shop carried them for a year, I think we sold one - I think. Originally listed at $329, they were almost giving them away at the end. Zero chilis for this dog of a product."

big john

There have been a number of Rube Goldberg contraptions sold over the years.

sysrq

People on bentrideronline are quite happy with it. They say they don't need anything better for rear suspension and are thankful that Shockster was still popular in 2022. It's also said to be less affected by chain tension due to being restricted to vertical movement only, unlike swing arm suspension with circular movement. Increased wheelbase is the main benefit they say.

sysrq

Depends on a specific country. In a countries with many potholes one is always prepared for them but in a UK for example with otherwise smooth roads with noisy surfaces due to coarse chipseal there can be sudden deep and wide cracks.

Ironfish653

Are you building a 'bent or a conventional diamond -frame bike? The needs of / what works for a 'bent vs a DF bike have almost nothing to do with each other.
As to the Shockster; it's not "still popular," it's been out of production since Y2K or so, and it was still a jimmy-rig back then. It's just that a bunch of NOS ones have popped up on eBay recently (an the reason that they've been sitting around unsold isn't that they're some undiscovered secret sauce)

There's a couple reasons why this unicorn F/S touring bike doesn't exist; first, bikes with integrated racks aren't really popular in NA, and even then it's mostly limited to utility/city bikes. Sure there's some bespoke racks like the Trek 1120, but very few permanently integrated into the frame. Just no demand for that specific feature.
Second, and more importantly, the last 30 years of development have shown that to get a suspension system with any kind of meaningful performance benefit, you end up with the shocks, linkage and mounting inside the main triangle. There's a few different ways to accomplish it, but to get an "optimal" rear wheel trajectory (not vertical, either), that's just how the math works.
If you're really seeking a comfort option, then there's a reason why suspension seatposts are perennially being offered, even the high -end ones like Redshift and Kinect; they're lighter and simpler. No one is going to take on the expense, weight, and complication of full suspension just for "unseen potholes"​​​​

sysrq

Suspension seatposts use only springs or elastomers so there is no damping and rebound adjustment. I have suntour ncx with preload adjustment only which reduces the available travel @ 90kg. Will have to get red spring for higher weight but at this point it's hard to justify investing more money into something so cheap yet expensive.

There is now rear suspension on a gravel bikes being used, but since those are quite boutique currently then it's not worth looking at.
https://www.cyclingabout.com/rear-suspension-on-gravel-bikes-genius-or-gimmick/

Ironfish653

Those bikes are Gravel Racers; high performance bikes for going fast on unimproved surfaces. The "soft-tail" rear end isn't anything new either; Moots did it 30+ years ago with one of their titanium MTBs. The same conditions applies to these bikes as well: it's lighter than a shock -and-linkage swingarm setup, but you only get a fraction on the wheel travel (10-20mm) and there's very limited amount of tuning available. In any case performance is the main goal, followed by comfort; cargo carrying is a distant third, if it's even a consideration at all.

Looking back through the posts, trying to figure out why you want a suspension frame that isn't shaped like a suspension frame and full racks, I'd guess that you're trying to make some sort of E-assist tourer/ long distance commuter. This is one of those "A,B, or C; Pick Two" situations: Picking a conventional FS frame would definitely complicate adding your E-assist kit, and limit your cargo options, while choosing a frame shaped to accommodate your chosen e-kit and rack setup would preclude most effective suspension setups, you're going to have to make that calculation yourself.

cyccommute 

Closer to 40 years than 30 and not just on their mountain bikes. They were using the YBB link in Psychlo Cross frame in 96 and they continue to do it even today in both gravel and mountain. The idea was used by several other companies in the late 90s. My YBB is from 1998.

sysrq

There is only one person with who has built a bike with Taut Terrain Panamericana so far.
https://motoredbikes.com/threads/bui...ng-bike.57007/
The rest of the fs bikes converted by users look too much like contraptions.
So far haven't stumbled upon any air shocks being used in suspension seatposts. Probably cause it's not worth the engineering since they are used for comfort only despite being capable of reducing the impact load on the rear wheel since rider weight is 80% of total mass.

PeteHski

I have never used a suspension seatpost, but elastomers can be self-damping in short travel applications like this. A hydraulic damper is more controllable, but probably not worth the complexity in this case.

For a touring bike focused on comfort over rough roads, wide, high volume tyres and a high-end suspension seatpost should work fine. Most of the “soft-tail” road bike frames seem to have disappeared as tyres have grown in width and volume.

sysrq

I think elastomers might be more affected by ambient temperature than springs.
Seems like going bigger than 37c or 40c and below 35 or 40 psi would be too much due to increased rolling resistance and weight. Only high speed motorcycles need wide tyres to prevent them from overheating.

Trakhak

Many people seem to be willing to make the trade: slightly higher efficiency and somewhat low weight for increased comfort, reduced shock transmission to the frame and components, and a bit more tire life. Going either way necessarily involves some sort of compromise.

PeteHski

So now you are showing some concern about tyre weight on a FS Tourer. I think you need to take a step back and decide what you are trying to achieve with this bike. But 40c tyres would seem like a good choice to me. Rolling resistance is more a function of tyre type, compound and construction than width.

You may be over-thinking elastomers vs springs in this application.

big john

Elastomers are affected by temp but any suspension component which is hydraulicly damped is going to be affected by temp as well. Any component just using a spring is going to be a boingy pogo stick. True whether the spring is metal, composite, or even air.

If you're just using a short travel spring to absorb a shock load then damping might be unnecessary.