Building an Ohlins Shock

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I have wanted to make an Ohlins shock fit the Commando/Roadster for a long time.

I am hoping to get feedback form people on the forum as to what you would want in a replacement shock.

Ohlins has been making them for the "New" Nortons since 2010.
While I was looking for info, I came across this forum, Lots of Good info, as well as some threads on Shocks and some pictures of various Ohlins Shocks on Bikes.
So I am going to give it a try.
First I learned a lot on this forum, the first issue was the fitment problem with the chain guard.
The OEM shock is very small diameter by today's standards., and on the Ohlins it is an issue. More on that later.
First things I had to get in order:
Know what is on the bike already
I have 4 Nortons, but only one is a "late" model one, (850 JPS)
So I have stock shocks.

Specs on the OEM Shock

OEM length 329 mm (Just shy of 13 inches.)
Stroke 83 mm
Width 18 mm top and bottom
Spring 22 Nmm Straight rate
Spring free length 224 mm
Installed length (preload) at "0" setting 213 mm
Installed length (preload) at "1" setting 205 mm
Installed length (preload) at "2" setting 198 mm

The Installed height, also known as spring preload, is the length of the spring when it is installed on the shock.

We like to see 15 to 30 mm preload on a twin shock set up.
We have a lot of Harley Davidson experience with twin shocks, some on /5, /6,/7 BMW's and Ducati Bevel drive twins.
With HD's a 1 turn preload increase (1.5mm) equals a 25 lb rider/passenger weight change.
This means if we set up a shock for a 200lb rider, and they add 25 lbs to the bike we increase spring preload by 1,5 mm or on an Ohlins shock 1 turn, 150 lb increase 6 turns, easy, right?
The chart is made on our Shock Dyno using an attachment that allows us to measure springs.


Check what weight that spring may work for by checking Rider sag
With a 209 lb rider:
At "0" preload Static sag 22mm Rider sag 47mm
At "1" preload Static sag 18mm Rider sag 38mm
At "2" preload Static sag 8mm Rider sag 29mm

What we shoot for is the rider sag at 30 mm and the static sag number is a check number, it should be between 5 and 15 mm

We will end up trying 3 different rate springs and see which ones work best for different rider weights.
if we need to try more we can, that part is easy.

18 Nmm, 20 Nmm, and 22 Nmm,
The lighter springs will require more preload assuming the rider weight were to be the same.
This means we could end up using a 18 Nmm spring with a 200 lb rider with a lot of preload, I suspect this is what we will find works best.

Next we ran Dyno tests on the stock shock, and as a comparison on one of the possible Ohlins shocks
I will post these later today, and explain what you are seeing in the charts, as without that they will not mean much.

Back to picking an Ohlins shock to start with.
There are a number of Ohlins shock that are close to that.
Not only does the length have to be correct the stroke, damping, spring rate, width.
We can change anything on the Ohlins shocks, but the closer they are to start with the easier it will be.

There are a few
SU143, Length 331 mm stroke 84mm Out of stock until Oct
DU140 Length 331.5 Stroke 93mm
HD159 Length (adjustable) 324 to 334 mm Stroke 77 mm

I am going to start with this shock, HD159.
This is one of a family of Harley shocks, Ohlins has these in Silver, or Black, with Black springs or Yellow, No chrome.
There are also versions with different part numbers with different features.
Ohlins has 3 versions in 2 colors for the HD's,
The 3 versions are at different price points.
The simplest only has an adjustment for spring preload , no damping or length adjustments (329mm)
The next version has adjustable spring preload, adjustable length, and adjustable rebound damping
The last version has adjustable spring preload, adjustable length, adjustable rebound damping, and adjustable compression damping

More later
Thanks

 
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Awesome! I will be looking forward to following this thread as it develops.
 
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Awesome! I will be looking forward to following this thread as it develops.
Shock Dyno Charts

the first chart is the OEM shock
The lower Graphs are Rebound, the top lines are the he compression, pretty much none. and no change with shock shaft speed.
The reason there are mutable lines is the test is done at mutable Speeds.
Six different speeds are used, which is why there are six lines, it is in a circle, or at least supposed to be, as it is continuous movement of the shock shaft.
The varying speeds produce more damping with higher speed.
The lower the lines the more rebound damping
On the upper lines, compression, there is no change.



lower graph show the Ohlins HD159 shock.
The his is a normal looking dyne chart, showing both rebound and compression.

 
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gortnipper

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This is awesome.

I would also love to see a graph of an IKON 7610-1653, as this has been a popular performance shock for Commandos for a long time: three preloads, progressive springs and variably rebound damping.
 
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This is awesome.

I would also love to see a graph of an IKON 7610-1653, as this has been a popular performance shock for Commandos for a long time: three preloads, progressive springs and variably rebound damping.
I do not have one.

If someone would sent one to me, I will run it on the dyne and post graphs on the spring and shock.

Or for that matter, any of the aftermarket shocks, I will do the same .

I would only need it for a day.

I mounted up the first set of Ohlins today, I should have the next two different sets ready by tomorrow.

I have also found some Ohlins chrome spring that should work.
 

gortnipper

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I would send it, but am in NZ and the last parcel from there to here took 3 months!

Anybody in the US?
 
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So the Ohlins only have single rate but adjustable damping, so no real upgrade against most currently available damping units.

For a real upgrade then either the Wilbers or the Nitron R3 shocks would be a better option, these have dual damping rates based on speed of shock movement giving digressive damping and both rates are adjustable separately giving 4 adjustments. High and low speed compression plus high and low speed rebound.
 
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So the Ohlins only have single rate but adjustable damping, so no real upgrade against most currently available damping units.

For a real upgrade then either the Wilbers or the Nitron R3 shocks would be a better option, these have dual damping rates based on speed of shock movement giving digressive damping and both rates are adjustable separately giving 4 adjustments. High and low speed compression plus high and low speed rebound.
There are 3 models of Ohlins Shocks that will work on the Norton
The First has no outside adjustable damping, of course as with all Ohlins shocks you can internally adjust the damping.
The second shock has adjustable Rebound damping
The third has both adjustable rebound and adjustable compression damping.

I have no idea what you mean by "the Ohlins only have a single rate" perhaps you can explain that.

As with most shocks the damping is increased with increased speed of the shock movement. As is shown in the dyne charts.

High speed damping is built into the shocks, and will not need to be adjusted.

Digressive damping is NOT always a good thing.
No Ohlins twin shock designs use this.
I cannot think of any Ohlins Motorcycle Monoshocks that use it either.
As far as you blanket statement, of other shocks being better, you have no way of possible knowing that.

There is a lot More to a shock, and how well it will work, then how many adjustments it has.

Thanks for you input, always good to hear other opinions.

Here is a picture of just some of the shocks that will work
They all will fit, out of the box, with mods to fit the bolt hole sizes and widths, without a chain guard or with a modded chain guard.

Top shock is the HD357, Adjustable comp, adjustable Rebound, adjustable length, Hose mounted Reservoir,
Next one the HD159, Adjustable Rebound, adjustable length
Next 2 are both HD022 One with a 200 mm spring the other with a 220 mm spring, you can see this will move the spring collar up, which gives us the clearance for the chain guard. You can also see that the upper spring mount is higher than all the shocks with a rebound adjuster making installing a 200 mm spring easy and able to have the correct preload. No damping adjustments, no length adjustment
Bottom Blackline HD764 Adjustable comp, adjustable Rebound, adjustable length, Piggyback Reservoir,

 
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Thank you for posting these, I have seen them already.
This interstate, is doing the same thing I am with the Non adjustable emulsion type shock.
They have switched the spring to a 200 mm length, so that it clears the chain guard.
The chain guard is what makes morning the shock a little tricky.
As the Ohlins all a larger diameter, they use a 36 mm diameter piston, the shocks with the normal 220 mm spring all hit the chain guard.
The other pictures, show different 2 Ohlins shocks with the chain guard removed. All of the Ohlins Shocks fit easily with the guard removed, or it it was modded to clear the shock.
The tricky part is to make them fit with the stock guard.
On the shock in this picture, as I noted, it is a non adjustable emulsion type. Which may end up giving the bikes the best ride, not the best for track use.
Anyway the upper spring mount is higher than any of the Ohlins shocks with rebound adjustment, so installing the 200 mm spring was easy.
On the shocks with rebound adjustment, the spring collar is lower so there is room for the rebound adjuster.
I have made an adaptor that moves the upper spring mount higher to allow the lower spring adjustment collar to be above the chain guard.
Without doing this the amount of spring preload is too high using the 200 mm spring.
With the Ohlins shocks the greatest range of springs are either 220 mm or 200 mm.

Below are pictures of the shocks being run on our dyno, the first one is the stock shock, and the second one is the Ohlins HD159.
You can see the rebound adjuster located at the bottom.
I will post some pictures later of the shocks mounted on a bike

 
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p400

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Can you post the tech data spec sheet for
HD022
HD159
DU140
SU143
HD044

It would give us the ability to compare internal specs against any dyno charts generated.
Thanks for this thread.
 
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It is also interesting that you can look at these two bikes in the pictures above, and see the shock angles are completely different.
The red bike may also have a different length swingers.
These factors would require some differences in the shocks, most likely different springs, as the leverage is different, possible different damping as well.
On all of the twin shock designs, the leverage on the shocks is far less the most mono shock designs. This allow us to use far lighter spring rates, and even when we are changing the spring rates for different weight riders the damper changes if they are needed are very small. Usually the standard damping can cover 2 to 4 spring rate changes without the damping needing any change.
Most mono shock designs use a linkage, for two reasons, the first is to make the shock travel (stroke) shorter, this reduces the length of the shock, making it easier to package in todays motorcycles.
the second is that with a linkage you can design it to be either digressive, very rare to see this, linear, or progressive.
Progressive is what all sport bikes use. Usually a 3% to 5% progressive rate, works the best for solo riding. As well as track use.
When twin shocks are mounted straight up and down, as they are on the red bike pictured above, they are linear.
When the twin shocks are mounted an angle as on the Black Commando above, they are progressive.
As British bikes advanced, you can see they all started doing this, meaning mounting the shocks at an angle, making them progressive.

There are also Linear and Progressive springs. like most choices, they both have advantages and disadvantages.

But first what is linear, it means as the shock or spring is compressed, it produces the same movement or rate increase for each mm or if you prefer inch of movement.
Example: a 22 Nmm spring, or spring mounted on a shock, that is linear, as is the Stock Norton spring produces 22 nmm of resistance for each mm of compression, so the first 1 mm of shock movement produce 22 Nmm of resistance, and the last 22 mm produce 22mm of resistance, Linear.

This on a graph, appears as a straight flat line, as you can see in the spring chart I posted earlier.

Progressive:
With a progressive design the amount of movement of the shock stroke is changed, as it is moving thru its stroke, the further it is in its stroke, the more the shock movement is increased. the amount of change is based on the angle the shock is mounted at or the design of the shock linkage.

This means the shock is moving more at the end of its travel than it was at the beginning, so even if the spring on the shock is linear, because the shock is moving more, it is compressing the spring more, so there is more spring resistance. If you compress a 22 nmm spring one mm at the beginning of the shock travel you will get 22 Nmm of resistance, but at the end of the shock travel, if you are compressing it 1 mm PLUS another 5% you will get 22 Nmm of resistance plus another 5% of 22 Nmm of resistance.

on a graph, this looks like a line at an increasing angle.

I will post some graphs.
 
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Can you post the tech data spec sheet for
HD022
HD159
DU140
SU143
HD044

It would give us the ability to compare internal specs against any dyno charts generated.
Thanks for this thread.
Here you go,
The HD159, HD022, and HD044 use the same valve/shim stacks. So I will only post the HD159



 
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robs ss

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So the Ohlins only have single rate but adjustable damping, so no real upgrade against most currently available damping units.

For a real upgrade then either the Wilbers or the Nitron R3 shocks would be a better option, these have dual damping rates based on speed of shock movement giving digressive damping and both rates are adjustable separately giving 4 adjustments. High and low speed compression plus high and low speed rebound.
Just fitted a pair of Nitron R3s - they are phenomenal!
you are correct about two settings for compression damping (16 clicks each for low and high speed) but they only have one setting for rebound (24 clicks)
 

robs ss

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B8523868-71D4-41B0-97C5-1ED766179BA1.jpeg
74EBE2F4-A914-47F3-8195-FA1A102C17D4.jpeg

BTW - the ss spacer ring at the bottom lifts the lower spring retainer by about 30mm - now clears the chain guard. Lucky there was about 30mm of threaded body above the upper spring retainer.
 
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View attachment 17687View attachment 17688
BTW - the ss spacer ring at the bottom lifts the lower spring retainer by about 30mm - now clears the chain guard. Lucky there was about 30mm of threaded body above the upper spring retainer.
Very nice!! Beautiful bike as well!! Your thread about these is one of the drivers for me to get these Ohlins going.
I could not find a Nitron listing for the Norton, were these the triumph shocks? I relise you had the SS spacers made.
What springs did you end up going with?
 

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