Before I torch my Mono...

[Rob Farmer]

I'm having suspension nightmares with my Mono g/s. I bought a Wilbers rear shock a few months ago. £350 so not the cheapest thing and it seems ok, nothing fantastic just ok. The problem I have is the emphasis has no been moved to the front end. I have standard springs and currently have 10W fork oil in. With me sitting on the bike there's 50mm of sag on the front forks. The problem is it feels crap. I tried 5W oil but it was terrible.

Anybody know what sag the forks should have?

 

[Mr K]

50mm of sag would be about right for a sportsbike, but I think it's also important that your rear-end sags the same amount....

 

[(RIP) Kaister]

try this -you'll like it and its nearly free.

if it doesn't work - nothing lost

drain the fork oil and refill with half the quantity of 20/50 engine oil.

this will stiffen up the compression and rebound.

if its too severe add atf until it waters down to what feels best

it works - i've done it on my dominator and it feels planted instead of twitchy

 

[Deleted account 211025001]

Thicker oil will help but, if you've just put on a nice new rear shock with a nice stiff spring that will maintain rear ride height then, yes, the front may well feel worse.

I'd have thought the ultimate answer is some slightly stiffer springs in order to regain the balance between front and rear but, worth trying would be to raise the preload by adding some spacers/washers/coins below the fork caps.

I'm guessing a bit but between Mr Kelly's 50mm sag for a sports bike and a typical dirt bike running 100-110mm why not go for 70ish mm.

Andres

 

[Rob Farmer]

Thanks guys.

I've set the rear shock to have 50mm of sag with me on it, worryingly I've had to back the rear spring off as far as I can to get that, it looks like the rear spring is too stiff.

A bit of measuring on the front end with me bouncing on it gives a total travel of 120mm (supposed to be 170) so the sag is eating up around 40% of the available travel. thats got to be too much?

I think I need to talk to every accessory about that rear spring as well.

Any thoughts?

 

[Kenny]

Bung a 10mm spacer in the top ( as previously mantioned )....I think the spacer at the bottom of the forks is 10mm so worth looking for a pair of them....your not the ...ahem...erm...lightest of gentlemen ( thanks to Sids bash/food) so maybe the spring is to hard and putting a spacer in the front forks means tippy-toe-ing around car parks etc.

Posh springs my arse..OE jobbie is only £210

I certainly wouldn't go heavier than 10w fork oil either...stick with 7w

 

[carinatauk]

Is there a cartridge for the monos? or is just for paralevers?

I tend to find the fronts travel too much with a slower than expected rebound, but I do have a very stiff rear Ohlins It may be a weight thing but its not too worrying until you apply greater than gentle pressure (suddenly).

Mine is in for some work at the moment and awaiting the options available. Don't really fancy a new front fork set, this machine has cost enough already with all the necessary bling and upgrades there are available

 

[cookie]

fit a set of progressive springs, then play with the oil?

 

[MiGSel]

I found 15W better for the standard forks.

 

[(RIP) Kaister]

Sag on all bikes is nominally 1/3 of full measured travel - inc extension.

On modern bikes they've stiffened up the damping and left the springs softer rather than rock hard - and tuned the valving to suit.

Doing the thicker oil trick achieves the same effect

 

[Rob Farmer]

Just been out taking some measurements.

Front

Static sag = 34mm
Dynamic Sag = 52mm
Total travel should be 200mm (according to BM Bikes but I could only get 120mm by bouncing on it)

Rear

Static Sag = 25mm
Dynamic = 50mm
Total Travel should be 170mm

Looking at the bumf that came with the Wilbers the front should have 25-30mm Static and the rear 10-15mm static.

Dynamic should be, as Phil says, 1/3rd of the total suspension travel.

So it looks like I need to take 10mm of the static sag out of the rear but that may affect the dynamic figure in which case I need a softer rear spring. The front needs 5mm less static sag and I need to find out why there's only 120mm of travel.

It feels as though there's too much emphasis on the front end and the rear doesn't react well to sudden bumps, feels too harsh.

I've got a set of Motorworks own progressive springs that I could fit Cookie, they aren't brilliant though they distort and rub on the inside of the fork tubes. May give me some comparison though.

I've never had much to do with suspension. I've just bolted decent components on in the past and they have worked well.

 

[Rob Farmer]

Is there a cartridge for the monos? or is just for paralevers?

I've got a pair of RaceTech Cartridge emulators but they need a matching set of springs to get the most out of them.

I'm going to get the bike setup as well as I can using the original components before I even look at fitting the racetechs.

 

[Shep]

Sell all the trick bits, put it back to stock and just ride the thing

So what if you have to slow a little more for bends, I doubt anybody will even notice

Save yourself a fortune as well

Shep

 

[Rob Farmer]

That's easy to say from the comfort of your Paralever

I haven't been riding the Mono because it's not riding too well. If there's no pleasure in riding it there's no point in having it.

 

[bakerlonglegs]

I know jack-all about suspension so can't offer much in the way of advice, but my mono isn't seeing much use at the moment, other than a slowing-forming plan to head for the Hograost. If you wanted to borrow any components off mine for comparison during your on-going investigations, help yourself. I rebuilt the forks during its restoration - new seals and rechromed fork legs, left the springs as is. Can't remember what weight fork oil, can check tonight if you want.

 

[MattW]

There's obviously only one solution Rob - sell it to me for £500

 

[(RIP) Kaister]

Just been out taking some measurements.

Front

Static sag = 34mm
Dynamic Sag = 52mm
Total travel should be 200mm (according to BM Bikes but I could only get 120mm by bouncing on it)

......................

put that into recognisable figures and 200mm is 8" while 120 is 5-ish inches.

bearing in mind you've got oil in them and you'll never go the last 1" by bouncing, then in reality you've got 6" - which is much nearer a true figure.

so you're looking at 2" in, 2 " to go in and out with and 2" to spare ( to paraphrase an old joke )

do the oil thing and stop messing about

save any money to take your missus out for a meal and you might get to practice the joke

 

[Beemerboff]

YSS make inserts for the mono forks.

Munich Motorcycles in Perth , Australia is the only place I have seen them.

Wilbers will have a set of fork springs to match your shock spring, and a recommendation on the oil to go with them.

Generally, the recommendation for shocks is that you start with 17 mm preload on the shock spring, and check to see if your sag is within the recommend range at that setting.

If you cant get it in the range with a 2 mm change either way to the preload you have the wrong spring, and this goes for any shock you can buy.

Then you want the set the front to 5/10 mm more dynamic sag than the rear.

So if you have backed the preload right off wind it back up to get around 42/44 mm sag at the back, to match the 52 mm at the front, then check to see how much preload you have on the spring. I have the Wilbers shock/ fork springs up on my VFR set that way, although the adjustable preload on the forks makes it easy to get the final balance just right.
I ended up with the stock 42mm at the rear and 48mm sag at the front on the Veefer.

IMHO it is the balance front to rear that you are setting when you fine tune the suspension, not some arbitrary sag figure.

I can adjust both ends of my GS on the move, and it doesnt matter which end I do the fine tuning at, when the balance is right both ends feel their best.

I know it sounds silly but there is a school of thought that says that the fork action on the BMW forks is better with 15 wt oil in one leg only, than it is with 7 1/2 wt in both legs - remember the paralever forks have all the compression in one side , and all the rebound in the other, and they work fine that way.

I try Motul full synth 10 wt fork oil in everything I have - I got fed up having half a dozen different half used bottles of fork oil lying around, and I like soft set springs / more damping too, so I add a bit 20 wt oil if the damping seems a bit weak.

 

[lurcher]

Rob If you liked the way the front end performed why not leave it alone and just sort out the rear. Sounds to me like you need a softer rear spring

 

[Rob Farmer]

To be honest I haven't been too happy with the front end for a while. The front and rear had obviously worn in together so didn't feel too bad.
The Wilbers comes with a note saying it's all setup and nothing needs adjusting, in reality the spring had been set with far too much preload, so much so that there was zero sag. I'd then backed it off too far. I've now set it up with 1 inch of sag and it feels much better though still harsh on big bumps. The front doesn't feel so bad either now that the back ends working properly. I'm now convinced that the only issue is that the fork springs are worn. I'm going to fit a pair of Wilbers springs and 7.5W fork oil (recomended on the Wilbers site).