Rear Suspension - Linkage vs Direct Connection

[kuksul08]

There are some models of motorcycles on the market that utilize a direct frame-shock-swingarm suspension setup rather than a linkage. In my opinion there are some downsides to this. I never even knew to consider this until I rode bikes both with and without it. I much prefer linkage bikes.

A linkage type shock setup has the following benefits:
-Lower center of gravity
-Better mass centralization
-Customizable spring and damping rate profiles, which allows for both initial bump compliance and bottom-out resistance
-Allows the use of common linear-rate springs
-Easy to raise and lower via "links" without internal shock modification

A linkage type shock has the following disadvantages:
-Higher cost to manufacture
-More bearings to maintain (every 50-100k miles?)


Anything thoughts on the matter?

http://www.motorcycle.com/ask-mo-anything/the-missing-linkage.html

 

[Gary856]

Below's a comparison of KTM dirt bikes using non-linkage vs. linkage rear suspension. Their conclusion seems to be it doesn't matter if it's set up for the task. I didn't realize KTM uses non-linkage rear on their street bikes too; I'll have to take a closer look at mine.

https://dirtbikemagazine.com/ktm-suspension-shootout-pds-vs-linkage/

 

[kuksul08]

Below's a comparison of KTM dirt bikes using non-linkage vs. linkage rear suspension. Their conclusion seems to be it doesn't matter if it's set up for the task. I didn't realize KTM uses non-linkage rear on their street bikes too; I'll have to take a closer look at mine.

https://dirtbikemagazine.com/ktm-suspension-shootout-pds-vs-linkage/

Seems like from that article it takes a fine touch from the aftermarket to get PDS to feel right. Linkage is more common and forgiving, for good reason. I am betting the added ground clearance is the primary reason for using PDS in enduro, while the extreme suspension dynamics of motocross all use a linkage.

 

[asteve]

Seems like from that article it takes a fine touch from the aftermarket to get PDS to feel right. Linkage is more common and forgiving, for good reason. I am betting the added ground clearance is the primary reason for using PDS in enduro, while the extreme suspension dynamics of motocross all use a linkage.

The Huskys are linkage and the KTMs are direct.

 

[fubar929]

-Customizable spring and damping rate profiles, which allows for both initial bump compliance and bottom-out resistance

This is the key! My Super Duke 1290 has a direct connection between the shock and swingarm. It fucking sucks! Truly the worst thing about the bike...

The lack of a linkage, in my estimation, makes it really difficult to get a good balance out of the rear suspension. As far as I can tell the bike has two modes: the rear is either soft enough that the bike absorbs big hits but tends to wallow everywhere else, or it glides across good pavement but kicks you out of the saddle if you hit any bump that's moderately big. Might work better on a dirt bike with long-travel suspension, but on a street bike you want a linkage, IMHO.

 

[Gary856]

Well I'll be damned... Up until now I thought most if not all bikes use linkage rear suspension, but of my current bikes only the WR250F and the 690SM have linkage.

SuperDuke 990, 950SM, R1200GS and Multistrada 1200 all have their rear shocks bolted directly to the swingarm, NO linkage. The suspension on these bikes are all superb, so I think the notion that "linkage rear suspension is better" is out the window.

There are some models of motorcycles on the market that utilize a direct frame-shock-swingarm suspension setup rather than a linkage. In my opinion there are some downsides to this. I never even knew to consider this until I rode bikes both with and without it. I much prefer linkage bikes.

What bikes were you comparing? Maybe you were simply feeling the differences between component quality and/or setup, rather than intrinsic design differences?

 

[Z3n]

Linkages are a pain in the ass if the rising rate is wrong - ref the amount of work gone into 999 linkages to get the things dialed in.

I prefer direct connection, easier to service, adjust, no variation in expectations in reaction depending on where you are in the suspension travel. Not a purchasing decision for me tho, any of them can be set up well. Minor preference to non-linkage off-road and on track, minor preference to linkage on street (handles 2 up better).

 

[FreeRyde]

Linkages are a pain in the ass if the rising rate is wrong - ref the amount of work gone into 999 linkages to get the things dialed in.

I prefer direct connection, easier to service, adjust, no variation in expectations in reaction depending on where you are in the suspension travel. Not a purchasing decision for me tho, any of them can be set up well. Minor preference to non-linkage off-road and on track, minor preference to linkage on street (handles 2 up better).

What linkage has hurt you? I've never come across a linkage that was so wrong it became a PITA. Conversly, I've come upon many direct mount suspensions that were utter garbage, with no real way to tinker and fix them.

I sit here scratching my head wondering how it's "harder" to service a linkage suspension vs a direct mount. And have never I been balls deep in the suspension travel of any bike and wondered "What it's going to do next".

Damper-rod forks are bandaided with progressive springs. Direct mount rear shocks can never be optimized over every type of obstacle, which is why many of them are sprung with progressive springs. (Soft initial rate and a mild progressive curve towards the end of stroke, like any good linkage suspension)


Lastly, off road is where you NEED a linkage type suspension. Why do you think every freaking winning MX bike is linkage driven? Because the engineers think it's fun to spend hundreds of hours designing suspension travel and dampening curves? Sometimes I wonder about you...


Just because KTM is the best and Ducaca use direct mount suspension does NOT mean they are good... Take for example my 2012 BMW GS (without ESA), the rear suspension feels good 80% of the time, then utter garbage the other 20%... Where as my DL650 linkage driven rear suspension feels flipping amazing at all times.

Now that we are in the time of electronic suspension that changes dampening 100x a second, direct mount can work similarly to linkage. But that opens another can of worms...

 

[Gary856]

Conversly, I've come upon many direct mount suspensions that were utter garbage, with no real way to tinker and fix them.

Which bikes are those?

Just because KTM is the best and Ducaca use direct mount suspension does NOT mean they are good... Take for example my 2012 BMW GS (without ESA), the rear suspension feels good 80% of the time, then utter garbage the other 20%... Where as my DL650 linkage driven rear suspension feels flipping amazing at all times.

What's the 20% situation that makes the GS rear utter garbage?

The DL650 rear feels amazing compared to what?

 

[FreeRyde]

Which bikes are those?


What's the 20% situation that makes the GS rear utter garbage?
The DL650 rear feels amazing compared to what?

1290 (990/950 too), GS, FZ07(09?), Hypermotard, Zero's.
All of these just felt off to me when ridden hard. Even my buddies fully set up FZ07 and FZ09, the bikes just never felt right no matter what shock they threw at them. The hyper was the worst by far. You could only set it up on one end of the extreme or the other.

GS: Any time I ride that thing balls out and hit a large divot in the road, the rear end blows through travel and wallows itself into oblivion (soft semi progressive spring). Or choppy braking bumps it soaks them up to the point of the bike wriggling around like crazy. Like I stated before, I have the non ESA, and the stock suspension is known to be shitttay.

The DL650 rear suspension feels damn good all the time. Even with the stock shock it stays more composed in all circumstances compared to the bikes listed above. A true testament to the glory years of Japanese motorcycle manufacturing and design.

Without a linkage it is a straight rate rear suspension. Performance rear suspension requires a progressive nature on engineering principles alone. Just take a look at mountain bike suspension technology... Or extreme offroad racing rigs.

 

[Gary856]

^^^ OK I need to try a DL650. If it's as good as you say I want one, but I probably don't ride anywhere as hard as you do.

 

[Z3n]

You should swap the DR suspension on to all of those bikes. I’m sure it’s the suspension that’s the problem.

 

[kuksul08]

^^^ OK I need to try a DL650. If it's as good as you say I want one, but I probably don't ride anywhere as hard as you do.

Whether you want to cruise around, hit the track, or win in the twisties, the DL650 is there for you. Truly a jewel of the modern era, and by far the best bang for your buck.

 

[fubar929]

SuperDuke 990, 950SM, R1200GS and Multistrada 1200 all have their rear shocks bolted directly to the swingarm, NO linkage. The suspension on these bikes are all superb, so I think the notion that "linkage rear suspension is better" is out the window.

Perhaps what you're noticing is that having a linkage isn't as important on bikes with longer-travel suspension?

 

[Gary856]

Perhaps what you're noticing is that having a linkage isn't as important on bikes with longer-travel suspension?

I think I'm noticing the carefully engineered overall system. It's too simplistic for us amateurs to claim one design element makes or breaks it.

 

[wingnutthehutt]

Oh geez. This is going to be a complete cluster. You guys need to trust the OEMs to hire good engineers and get over it. KTM has been running linkless on the majority of their machines for DECADES. Cruisers are mostly linkless because that's how Harley did it in the stone age and old fat white guys freak out if you change things.

If you think your suspension sucks, try having it professionally set up for your weight and riding style - it will make a massive difference. Yes, it will require spending money.

Now get back to arguing about oil viscosity and V4s, mmk?

 

[kuksul08]

Oh geez. This is going to be a complete cluster. You guys need to trust the OEMs to hire good engineers and get over it. KTM has been running linkless on the majority of their machines for DECADES. Cruisers are mostly linkless because that's how Harley did it in the stone age and old fat white guys freak out if you change things.

If you think your suspension sucks, try having it professionally set up for your weight and riding style - it will make a massive difference. Yes, it will require spending money.

Now get back to arguing about oil viscosity and V4s, mmk?

This is way more interesting though. We all know that it doesn't matter what oil you use, as long as it costs enough to make you feel like you're doing the right thing.

I think your argument contradicts itself. Linkless suspensions are FAR simpler, cheaper, and a compromise compared to a link system.

 

[wingnutthehutt]

I fail to see the contradiction. Help me out. Where did I say that one was better than the other?

 

[FreeRyde]

Oh geez. This is going to be a complete cluster. You guys need to trust the OEMs to hire good engineers and get over it. KTM has been running linkless on the majority of their machines for DECADES.

These two thing cannot be paired together, contradictions.

Just because KTM has been doing it for decades DOES NO MEAN IT'S GOOD!!
They flipping produced a slave cylinder that leaked for how many years without an OEM fix? They knew it was fuct and just kept producing it! What makes you think their suspension design is any better?!

 

[Z3n]

Yeah Honda and Suzuki regulator/rectifiers blow up constantly so I don’t trust their suspensions at all. Makes complete sense.

Here’s the problem with linkage suspension in a nutshell - let’s say your damping is set perfectly for a bump when you’re in the top 3rd of the travel. But as you move through the travel of the shock, the linkage now changes how much force is needed to compress the shock, and your damping rates are off. You have the choice of making the top soft to get the damping correct towards the bottom, or you make it ride stiff high in the travel for good feedback and becomes non-complaint when the linkage ramps. You can go to a straight rate linkage system as racers use in the Ducati platforms, but now you’ve erased the supposed advantages of the linkage system.

If the concern is bottoming, there’s a bunch of different systems to help handle compliance in bottoming with non-linkage systems, like KTM/WPs PDS system.

No matter how you slice it, all suspension is compromise, minus the modern electronic stuff which can theoretically change damping on the fly to meet the exact road conditions. But those systems aren’t really customizable yet by end users to match different riding styles and preferences so they have their own series of compromises.