900 Sie forks upgrade?

[Bitza]

Hi all, OK I doing a bit of a winter sort out with my much tweeked 1994 M900. I've had the rear shock recond, I've extended the side stand (due to having extended the rear suspension hoop), adjusted the shape of the brake pedal so it's a bit easier to find?! and now I'm contemplating up-grading the 2001 M900 Sie Showa forks (fully adjustable), possibly with a cartridge kit. So over to you-all what's on offer, what works & what doesn't, what have you tried etc.? One further thing is the spring stiffness question any suggestions for a 90kg lump like me (raised rear end, shock fitted with a 29/90 spring (i.e. 90 newtons or is it 90kgs/mm sorry I haven't a clue), clip ons & rearsets, and strictly solo riding only. All suggestion welcome, Bitza.

[Flip]

Well it's a bit like asking how long's a piece of string as it really depends on your budget to a large degree.

But you are starting from a relatively good place as you have Showa forks which means there are quite a few options open to you from simply fitting better suited and correct weight springs from the likes of Hyperpro:

http://hyperpro.com/springs/

To full cartridge replacements such as the K-tech ones:

http://www.ktechsuspension.com/products/road?field_prod_cats_nid=7

Or those from Maxton:

http://www.maxtonsuspension.co.uk/files/gp20.htm

And of course there are a myriad of expert services willing to take your money in return for a better handling motorcycle.

Personally I decided to go with Maxton's GP20 cartridge conversion (coupled with a Nitron rear shock) as I had Marzocchi forks on my '97 900 (I also used Maxton for the suspension on my 1965 classic race bike) and they have been a revalation.

Not only have they allowed the bike to handle as the chassis is capable of (far better than me) but they also remain compliant and comfortable over long distances- 1100 miles in four days on my European jaunt earlier this year- no problem.

This is what Richard at Maxton says about the Monster's forks:

"The forks feel very notchy and harsh and kick off small bumps, this is because they have too much compression damping over small movements, however when you brake very hard you may be able to feel the forks bottom out, this is because there is not enough support in the compression damping over large movements.

The other problem with the damping is there is not enough rebound damping which means when you let go of the brake the forks spring back at you and the bike does not turn into the corner as well as it should, this also causes the bike to run wide out of a corner. The springs inside the forks are actually too hard and we fit softer springs to suit your rider weight and also to suit what type of riding you do.

The biggest improvement felt is from increasing the rebound damping to control the forks extension, reducing the compression damping over small bumps to stop the forks kicking off small bumps and increasing it over large movements giving more support with the spring."

Hope that helps some at least but if you need any more detail about my set-up ask away and I will do my best.

[SteveG]

I second Flip's advice. On my 96 M900 -which also had Marzocchis at front I went the Hyperpro route to start with using PDQ in Slough (primarily as money was tight). Made a difference for sure but not as much as I was expecting.

Eventually I went the same route as Flip after doing some research on the forum (mainly provided by Flip tbh!!) and after a discussion with same knowledgeable chap- the legendary Richard at Maxton. The GP20 cartridges and set up by Maxton made a huge difference - the symptoms described in Flip post I knew very well. Maxton are great in my opinion but cheap they aren't and if you do go for it try not to catch them at the start of the race season as you are likely to have to wait a long time to get them back. Let us know how you get on if you take the plunge - be it in the shallow or deep end :)

[utopia]

Well, to start the ball rolling at a very preliminary level ....
The rear spring rate will be 9 kg/mm.
But strictly speaking, kg is a measurement of mass, not of force.
Using one of Newton's basic laws of motion, Force = mass x acceleration.
In this case, the acceleration in question is the acceleration due to gravity, which is 9.81 metres per second squared. ....which is roughly 10.
So the correctly quoted spring rate (ie stiffness) would be approximately 90 N/mm.

Suspension is a science, but such a complicated one with so many different aspects that it assumes the status of an art.
If you want perfection (or at least the best possible compromise) then you may be well advised to rely on the experts and get the forks modified by the likes of K-Tech, Maxton etc.
On the other hand, if you want to learn, there may be something to be said for experimentation.

The other factor is whether or not the bike is a keeper.
If it is, the Maxton, K-Tech route may be worth the expense in the long run.
If not, then it may be worth going for a lesser but cheaper improvement by altering spring rates, oil viscosity, airgap etc. You would need to be up for a bit of work though as it may be necessary to strip the forks a few times before getting it right ..ish. ..but probably never perfect.

I certainly can't claim to be a suspension expert but I do have a half-reasonable grasp of the engineering/physics involved.
For this reason, its very tempting to experiment a bit, in the hope of learning summat as I go along, as well as (hopefully) improving the forks to some extent.
However, my 750 is a lifetime keeper so I will probably send them off to Maxton and let them work their magic.

Certainly, the "Richard at Maxton" analysis of the Showa forks rings true to me.
But then again, my Showas are non-adjustable and I have no idea whether their internals are the same apart from the provision for adjustment, or whether they have an even more budget damping system.
And presumably the harsh springing and compression damping would be more obvious for me due to my body weight being not a lot over 11 stone, compared to your 14.
I do have a similar low bars, rearsets, extended hoop, weight forward set-up to yourself though.

Here's a link to Race Tech's FAQ page.
http://racetech.com/page/id/30
This looks as if it contains a fair bit of relevant info to provoke a few thoughts.
I thought that Q12 was particularly interesting as a starting point.
And I believe there is info out there, possibly on the American monster forum or maybe from the likes of Brad the bike boy, or Chris Kelley, on experiences with their "Gold" valve kit.

I have also come across replacement internals for Showa forks from FG Gubellini.
I know next to nothing about them (other than its the same company that makes Ducati Performance paddock stands).

And finally, I know that Jerry has been tweeking the forks on his S4 (?) for quite some time and now has a compliant set-up which I believe involves lighter springs.

Well, not quite finally cos I've just thought ....
If you were to consider progressive springs, first read Q5 on the Race Tech page.

And ...
It would also probably be worth fitting one of those fork travel indicators (that look like an O-ring).
This should give you some sort of indication as to whether you have the correct springs.
Though the picture will be somewhat confused by the compression damping.

:spin:

[Mr Gazza]

I would be interested to see if you can improve those forks. I have fully adjustable Showas on my Sie too.

I've got no complaints about the handling, steering or roadholding on mine at all.
I did start to think that the ride could be smoother at one time and I got a bit fed up with bumps.
I backed off the damping a little, to see if it would ride the bumps a bit smoother. By coincidence I then started using mainly better surfaced A roads for my trips out of the County. The ride was certainly more comfortable and I noticed no adverse effects to the handling.
However when I returned to riding my beloved Norfolk B roads, I noticed some difficulty in holding a line round some of my favourite bends. Worse still was the effect of the bumps on the steering, deflecting wildly off some of the road "imperfections".

I dialled the damping back to about one click from factory default on rebound and compression and regained control... Sure I feel the bumps... I ride bloody bumpy roads, but I now go where I want to go and not where the bumps send me, so I think it's about right.

I don't know what spring rate I have nor the exact oil viscosity, but according to the previous owner there is an Ohlins cartridge in there? maybe I will have a look one day when I feel the need for an overhaul, but till then as mentioned I will be interested to see if you can make any improvements.

I did also notice that she became a bit "wanderey" towards the end of Summer, she had a bit of a meander round some bends?
My first thoughts were that the head bearings were on the way out, but it turned out to be a flat coming on the back tyre. I managed to transform the handling back to normal in two minutes by grinding the tyre back round.. I kid you not.

My point is that tyres can alter the feel of a bike profoundly.... Might be the first place to look?

[Flip]

And presumably the harsh springing and compression damping would be more obvious for me due to my body weight being not a lot over 11 stone, compared to your 14.
I do have a similar low bars, rearsets, extended hoop, weight forward set-up to yourself though.

Yes I would say so and perhaps as I weigh around 10 stone coupled with the notably worse feeling Marzocchi forks that feeling of harshness was even more apparent.

I also have low bars (Renthal Ultra Low), rearsets, raised rear (oooo-er missus) and the forks pulled through the yokes.

[Flip]

I would be interested to see if you can improve those forks. I have fully adjustable Showas on my Sie too.

I've got no complaints about the handling, steering or roadholding on mine at all.
I did start to think that the ride could be smoother at one time and I got a bit fed up with bumps.
I backed off the damping a little, to see if it would ride the bumps a bit smoother. By coincidence I then started using mainly better surfaced A roads for my trips out of the County. The ride was certainly more comfortable and I noticed no adverse effects to the handling.
However when I returned to riding my beloved Norfolk B roads, I noticed some difficulty in holding a line round some of my favourite bends. Worse still was the effect of the bumps on the steering, deflecting wildly off some of the road "imperfections".

I dialled the damping back to about one click from factory default on rebound and compression and regained control... Sure I feel the bumps... I ride bloody bumpy roads, but I now go where I want to go and not where the bumps send me, so I think it's about right.

I don't know what spring rate I have nor the exact oil viscosity, but according to the previous owner there is an Ohlins cartridge in there? maybe I will have a look one day when I feel the need for an overhaul, but till then as mentioned I will be interested to see if you can make any improvements.

I did also notice that she became a bit "wanderey" towards the end of Summer, she had a bit of a meander round some bends?
My first thoughts were that the head bearings were on the way out, but it turned out to be a flat coming on the back tyre. I managed to transform the handling back to normal in two minutes by grinding the tyre back round.. I kid you not.

My point is that tyres can alter the feel of a bike profoundly.... Might be the first place to look?

I would be interested what is inside them too as I would be surprised if anyone (other than a racing god) could feel one or even two clicks difference on the standard forks but I think you hit the nail on the head with saying it kicked off bumps when you backed it all off then when you returned to close to the original setting it didn't kick off so much but you felt the bumps again.

All I can say is my Marzocchis kicked off bumps when travelling at a reasonable speed and would literally jolt at slower ones (this isn't even going into the realm of compounded compression when braking hard over said bumps) and since the Maxton job it no longer kicks off bumps but floats over them at any speed letting me feel the road and what's going on without making the ride feel harsh and tiring.

However, as Steve said- it doesn't come particularly cheap but I for one wish I had done it years ago it's made such a difference for me.

As for tyres, absolutely they can change the feel of the bike.

When I swapped from Pirelli Diablo's to Michelin Pilot Road 3's I was very disappointed initially due to the way they slowed the steering- the grip felt amazing though.

Admittedly I changed them at the same time Maxton converted my forks and Nitron serviced my rear shock so it was difficult to say the slow steering was all down to the tyres - a good lesson there for only changing one thing at a time but a need to renew the MoT before scooting across the channel for a mini Euro tour meant that wasn't going to be possible.

A little more fiddling with some extra rear ride height along with new head race bearings had my quick steering, sweet handling Monster back in no time.

Oh and just to throw another (rather famous) name in the mix here's the Öhlins alternative:

https://www.ohlins.com/products/motorcycle/

[jerry]

my S4 has showa forks from a 996 , they have Kteck valves and custom made 7.5nm springs oil level is at 125mm they are compliant and the bike now handles superbly but its taken a lot of testing ,,mcompression is currently set at 7/16 and rebound at 3/18 fork oil is 7.5w i have experimented with different oils 5 , 10 and settings,,,

the oringinal forks wer showa also but had no proper rebound circuit even though supposedly fully adjustable ,i had experimented a lot with those crap forks including oil weight , height and hyperpro progreesive springs s all a waste of time IMHO ,

if i had a standard S4 or Similar setup again again i would go the Maxton internals route for ease of getting it done as the cost would be about the same as what i have done with less hassle ,,



the only handling problem i have now is above 110mph the front end goes light and starts a wobble ,, but a damper may be the only way to stop that as I have changed ride heights and balance front to rear a lot ,i have also noticed that front screen fairing makes it worse taking it off and the wobble starts at 115mph , rear shock is an ohlins PRCS 46 it very good ,,

[Darren69]

Please keep us posted how you get on with whichever option you go for. I shall follow the thread but would tend to agree with what Jerry said regarding the Hyperpro kit. I think that while it does make a small improvement the cost outweighs the benefits. I did mine as a refresh expecting similar results to those that I had when I had fitted them to '80's Jap tourer stuff and early Hinkley Triumphs. They were only better on the S4 in the fact that I could back off the damping top and bottom by a few clicks to make them smoother but not as much better as I had experienced before on cheapo 20 year old Jap bike forks. The Showas are god but still a budget fork and I guess that means they can't be improved much for a small budget. I can't help thinking that they're over damped and better suitaed to a much heavier bike than the monster and also that a total re-valve with better quality gear would make them so much better.

[Flip]

I know a lot of this is down to personal 'feel' if you like but until you have had the suspension properly tailored (by whatever means) for your weight, riding style and use then it is difficult to get across just how good your bike will feel.

For me Maxton have worked wonders, firstly on my 1965 250 Ducati Mach 1 race bike which after my first season in 2012 racing it as I had bought it I decided to talk to Richard because I knew they had a lot of experience with classic bikes (Manx/Classic TT, Goodwood Revival/Lansdowne Classic etc.). I told him I was new to classic racing and wanted it to feel a little more 'familiar' as it was bad enough with drum brakes let alone suspension using engine oil to damp it. So the forks were sent off and they machined the internals to accept their GP20 cartridges while keeping them looking original as per classic racing rules. They also made a pair of rear shocks so I could dump the un-damped and over sprung (for me) Hagons. The result was amazing, they had turned my fifty year old physically tiny 250 into a sweet handling stable racer that a novice like me could feel at home on letting me concentrate on getting smoother, an upside down right foot gear change and drum brakes to reel it all in with.

So like others here, over the years I have played with the forks on my Monster trying to get a good compromise with the limited options available to me but never achieving it.

Fast forward to my Monster refresh of last year- as I was stripping it down and replacing this and that it seemed daft not to do something with the forks as I was getting the Nitron shock fully serviced after ten years of use.

I did have a pair of 888 Showa's I had bought (from Natty) which were in excellent condition and for a time considered fitting but as I suspected they would also need a service and quite probably re-springing for my weight or possibly more work to get them right for me.

Another call to Richard to ask my best route- modify my existing Marzocchi's or have them go through the 888 forks and see what's needed with both options potentially costing a similar amount.

So after the chat with Richard I made the decision to sell the 888 forks to fund the conversion of the Marzocchi's knowing the end result would be the same.

Well the rest is history- I couldn't be happier and wish I had done it years ago. Not only do they allow the true handling of the bike to be exploited they also (and this is the really important bit) make the whole riding experience so much nicer at ANY speed and on ANY road I have (so far) ridden from bumpy B roads to continental auto routes.

Simply put and coupled with a good rear shock (assuming everything else is within spec) the result is Night and Day!

[Bitza]

Have decided to bite the bullet so am taking the forks over to Maxtons over at Frodsham tomorrow on my way to Scotland. I'll post an update on the success or otherwise of the winters up tinkering sometime in the spring. Thanks again to those who have made helpfull suggestions, Bitza.

[utopia]

That made me chuckle.
While its not clear which is the right way to approach this problem ..
.. that certainly isn't the wrong way.
Keep us posted.

[Bitza]

Hi all, have picked up my reworked forks from Maxton's today, a totally professional service and friendly/approachable to boot. This of course means I now have the original damper units, springs and top nut/adjusters surplus to requirements, so if anybody can use them let me know. (The forks were off a M900 Sie, i.e. fully adjustable Showas from 2001). Bitza.

P.S. Will post an update when I've ridden the bike for a few miles, so late spring I'm thinking.

[Mr Gazza]

Blimey! Did they feel the need to get rid of all the standard guts?

Very interested to hear what they did and to see what your forks look like now. Especially the new adjusters.

[Bitza]

Hi, well yes the whole damper/spring/spacer/top nut adjuster unit is replaced, the new top nut/adjusters are very neat and smaller/lower than the originals (black with purple rebound adjusters in the center). Interestingly Maxtons consider the original forks to be generally under sprung (0.775 kg/mm), but heavily over damped for compression giving the forks their stiff feel and bouncing off bumps in the road as the forks compression damping almost locks the fork. Mine are now replaced with 8.5 kg/mm (bearing in mind that I weigh 14 stone) which are the softish option aimed to give a plusher ride over dumpy A/B roads, with the shim stack of the GP20 unit adjusted to drastically reduce the compression damping on short/sharp movements. Another thing is that they also said that If I was disatisfied with the results, and wanted say the have harder springs they would would do this on a straight exchange basis.

[utopia]

Yep, that's exactly what I would have expected them to say, and its how my bike feels (it has basic Showas).
When I had a fork compression indicator fitted, it looked like I was using a decent spread of the available travel (which presumably occurs for the most part as a progressive loading) and yet the front end jars awfully when asked to respond fast to bumps etc.
That does seem to say soft (ish) springs and hard compression damping I guess, but I can see how its counter-intuitive to be fitting harder springs as part of the cure for harsh forks.
And yes, I reckon the price includes guaranteed customer satisfaction in the end result, at no extra cost.
They will be getting my money when I've saved enough of it up.

I would be interested to see a pic of the fork top adjusters.
I have minimal clearance available for conventional adjusters due to my flat bars .. and I don't really want to fit extra risers.
But I think my ideal arrangement would be to have preload adjustment, as I would like to be able to dial in pillion settings on occasions (rarely, but definitely sometimes) .. that's how the back end is set up already.

[Flip]

Blimey! Did they feel the need to get rid of all the standard guts?

Yes they junk the lot and machine the internal fork lowers to accept their GP20 (proper) cartridge assembly.

Some say by doing so they are re-inventing the wheel but (especially in the case of the Marzocchi forks) by starting again you are working with a known, proven product both on the track and the road at all levels which can be tailored not only to the motorcycle itself but also to the individual rider and their intended use.

As we know they don't come cheap but that level of quality and service seldom does and personally speaking they have transformed both my Monster and my little (1965) race bike.

But you're right though- you do end up with a lot of left over bits!!! :D

[gary tompkins]

I had H&M racing rework the forks on the gsxr750 with Ktech parts

made a big difference