Ohlins Cartridge Conversion to Commando Forks?

We've had some discussions on this possibility in another thread


so I thought I should start a new thread to deal with it.

Dan Kyle brought up the possibility of fitting the Ohlins NIX 22 cartridge conversion into Commando forks,


so I thought I'd see if I could give it a shot. Dan is an Ohlins dealer and service center, so has access to the different conversions kit applications, and can hopefully sort out one that can be used on the Commando forks. It will for sure require making new adjuster bodies at the top, since Ohlins doesn't make a kit with a body that can be fit to the skinny Norton forks. And there might be some issue with sorting small enough diameter springs, and probably some minor machining at the bottom bolt area. But all that looks doable. In the process, I put together this collection of dimensions on the Commando forks, and I'm posting it for anyone interested. Hopefully, we will soon be able to add Ohlins cartridges to the list of other conversions available for Roadholders.



Ken

I realize that you haven't yet installed these yet and that getting the damping and spring rate to match the laden weight of the test bike as well as having the handling behavior you are seeking at the speed of the sweet-spot, but from a "money is no object" can you speculate how the Ohlins may stack up against the Consentino inserts?

I replaced the OE dampers on an '07 BMW R1200 GS with Ohlins and was blown away by how much better the motorcycle felt and how much more adjustability I got and the noticeably broader the sweet spot got; Ohlins on the initial offerings of the new Norton almost made me buy one.

Any sense of what these jewels might retail for?

Best.

RoadScholar said:

I realize that you haven't yet installed these yet and that getting the damping and spring rate to match the laden weight of the test bike as well as having the handling behavior you are seeking at the speed of the sweet-spot, but from a "money is no object" can you speculate how the Ohlins may stack up against the Consentino inserts?

I replaced the OE dampers on an '07 BMW R1200 GS with Ohlins and was blown away by how much better the motorcycle felt and how much more adjustability I got and the noticeably broader the sweet spot got; Ohlins on the initial offerings of the new Norton almost made me buy one.

Any sense of what these jewels might retail for?

Best.

Click to expand...

I can answer some of your questions.

first we know what the stock Norton spring is, thanks to Ken.
36.5 lb in that converts to just over 6Nmm
Ohlins makes a 6.0 Nmm as well as 6.5Nmm and 7.0Nm as well as stiffer.

We know the stock fork stroke, thanks Ken, 120 mm.
length fully extended 743 mm and fully compressed 623 mm
120mm is pretty standard for most street bikes forks.

How do we pick a spring? we start with a 6.0 Nmm install it and measure rider sag, we know from experience we are looking for 40 mm Rider sag, we will use a small range of spring preload to get there.
the springs will vary depending on the rider weight. the 40 mm rider sag will not.
so once we pick a range of springs, and we know the stroke, we go back to Ohlins to see what they have already developed in that rate and stroke.
That part is really just that easy.

As far as cost, we have to start with an Ohlins 22 Nix kit, and a set of Ohlins springs. They are $750 to $800
We have to add a few new parts, a different cap that will have to be made, some other small parts, and Ohlins fork oil $30
I do not know what the caps will cost yet.

As far as comparing the Cosentino inserts.
I have no first hand experience with them.
I have read that they are based on a Showa cartridge, that would be a 20 mm valve. The compression adjuster is located in the fork bottom, again from what I have read, That would make it very likely it is a Ducati based cartridge.

I have a ton of experience with 20 mm Showa cartridges, we have worked on thousands of them.

Showa is Owned By Honda so all Honda's have Showa suspension, other than the Moto GP Honda's that use Ohlins, like every other Moto GP bike, and some street Honda's which use Ohlins such as the Limited CBR1000SP
Showa suspension parts are also used on other brands as well, HD, Ducati, Suzuki, etc.

20 years ago we were reusing the stock valves and reshiming them . They were better
At some point maybe 15 years ago, we started replacing the Showa Valves with Ohlins valve, the difference is dramatic.
At some point we started replacing the entire 20 mm Showa cartridge with Ohlins 25mm and then 30 mm Ohlins Cartridges, the difference was huge.

The Ohlins NIX 22 cartridge kit we will use has a number of improvements over the Showa cartridges.
The first is Much lower friction, starting with the valve and valve piston, along with a hard crammed steel staff, that looks like it came from a $2500 Ohlins gas charged cartridge from a few years ago.
Much better sealing, meaning sealing the oil in the cartridge, the seal head is much tighter,, which is better as any oil leakage around the sealed, ends up making the damping vary.
Much better spring control, as the Ohlins uses a spring guide along with very short springs. This reduces friction, keeps the oil cleaner, and quieter.
the Ohlins are designed to be rebuilt forever, so they are easy to work on, easy to disassemble, unlike the Showa Cartridges.

Most important is the damping, day and night better.

Dan, a slight correction. KTM has WP suspension on their MotoGP bikes.

Mike40M said:

Dan, a slight correction. KTM has WP suspension on their MotoGP bikes.

Click to expand...

Of course. Thanks
KTM owns WP

The Cosentino inserts are based on CBR600RR Showa 20mm ID inserts, the shims are set to be much more compliant than the same inserts as Showa supplied to Ducati but are easily changed either way. There are Moto Guzzi springs at the right length and poundage.

kommando said:

The Cosentino inserts are based on CBR600RR Showa 20mm ID inserts, the shims are set to be much more compliant than the same inserts as Showa supplied to Ducati but are easily changed either way. There are Moto Guzzi springs at the right length and poundage.

Click to expand...

Are the compression adjusters on the bottom?
Looks like they make a new bolt for the bottom and added their own needle as well.
Thanks

Dan Kyle said:

Are the compression adjusters on the bottom?
Looks like they make a new bolt for the bottom and added their own needle as well.
Thanks

Click to expand...

"There's a needle valve in the top cap and bottom bolt, giving adjustment to compression and rebound damping. Only drawback is the axle needs to come out to adjust the bottom allen"

There is a fitting made for the bottom that replicates the original shaped cone for the compression hydraulic bump stop, inside is the low speed compression needle in a vertical hole accessible when the axle is removed.

kommando said:

The Cosentino inserts are based on CBR600RR Showa 20mm ID inserts, the shims are set to be much more compliant than the same inserts as Showa supplied to Ducati but are easily changed either way. There are Moto Guzzi springs at the right length and poundage.

Click to expand...

Could they have used more than one type of cartridge as a donor?
The one shown on their website is not a CBR600RR cartridge.
All CBR600RR had hydraulic stops as far as I know.
Ducati's did not
The one in their picture does not


And the CBR600RR you can see the hydraulic stop

The Norton fork tube is a very thick sidewall. this makes it very heavy as well as small ID
I measure it with caliper at 26.2 mm
This is large enough to fit the Ohlins NIX22 kit.
It limits the springs more than I would like.
We have 3 rates of Ohlins spring that will fit 4.5 Nmm, 5.5 Nmm and 6.0 Nmm
Racetech looks to have a number of springs as well, I ordered one set to test fit. I may need to shorten them.

Another possible solution is boring the ID out another mm, I will look into that as well.

Some new questions
Does anyone make a modern lower and or upper bushing?

On the Norton aftermarket fork tubes are they all the same wall thickness as the originals?

Thanks

NYC Norton (made by Cosentino) offers a Teflon upper and lower and JS Motorsport has a Trucite upper and lower.

The Turcite bushes work very well. Mine just neede a slight fettle with some wet dry on the upper bush of one.

Dan Kyle said:

Could they have used more than one type of cartridge as a donor?
The one shown on their website is not a CBR600RR cartridge.
All CBR600RR had hydraulic stops as far as I know.
Ducati's did not
The one in their picture does not

And the CBR600RR you can see the hydraulic stop

Click to expand...

They do not have the external hydraulic stops but the internals are the CBR600RR valves and shim stacks, the adjusters are also CBR600RR not Ducati. Honda made a few changes and the last version of the 20mms had an internal top out spring like Ducafi. I have just made a set of cartidges using CBR600RR valves and bought alloy rod and tubes and machined them to suit my application, I also used Ducati adjusters this time for the click feature not present on the CBR600Rr.

I just realized I left out a link in the Rob North thread mentioned above, to the thread about a Honda F4i cartridge conversion to Commando forks a few years back. Basically, I copied Chris' conversion, with a few changes. For anyone intersted, this is the link


Ken

FWIW, the cartridges I used were from 2001-2006 Honda CBR600 F4i. Those are conventional, not inverted, forks. I think those are the same components Chris Cosentino uses. They do use a hydraulic lock at the bottom of the cartridge, but Chris' conversion doesn't use it. Neither did I. In my case, I made a new end cap to match the hydraulic lock design in the stock Commando forks.

Ken

lcrken said:

I just realized I left out a link in the Rob North thread mentioned above, to the thread about a Honda F4i cartridge conversion to Commando forks a few years back. Basically, I copied Chris' conversion, with a few changes. For anyone intersted, this is the link

Commando Fork Cartridge Conversion

I just finished the work on converting a set of Commando forks to take Honda F4i cartridge internals, and thought I'd post some pictures. I won't get a chance to try it out for a while, because I'm also refurbing the rest of the bike, a second MK3 to complement the one I've been riding. I'm...

www.accessnorton.com

Ken

Click to expand...

Great thread a lot of infor there.
Some comments, as this was done a number of years ago, some of you may know this stuff already.

Oil level.
As low as possible, most manufactures put the oil level higher than needed as a precaution, If it is below the seal head of the cartridge air can get in and you will lose all damping.
So with the cartridge full of oil, air pumped out, the level needs to be above the seal head.
With Ohlins Spring charged or Gas charged CARTRIDGES, Not forks, we add as little as 20 cc of oil to the forks, just to lube the bushings and seals, the cartridge contains its own oil.
The reason for this is the air in a fork is compressible, as the fork is compressed, the PSI inside the fork is increasing, this effectively is changing spring rate in a very progressive way.
We do not want that, it is unpredictable, as we are using a spring that has a know rate that we have picked already.
For a production street bike, it keeps the fork from ever bottoming out, no matter what weight is on the bike.
The Norton fork is very bad here due to the small fork tube size and the very thick side walls, there is not a lot of air to start with.

Oil weight
Fork oil weights have nothing in common with engine oil weights.
With an engine oil the manufactures are consistent, with fork oil they are not.
One brands 10 weight could be the same as another brands 5 weight or 30 weight.

More later