G/S project... sort of

Hi Rossi, I’m confused as to why you have a 4 stud bevel box on a monolever.

On my G/S I’ve fitted the ‘Prutser Triples’ (as seen on advrider)which take the 49mm Showa forks from a drz and a 100mm extended swinging arm. This arrangement gives good suspension travel at both ends and a much better action at the front compared to the gs fork. The yokes are beautifully designed and made and overcome all the disadvantages of using the original drz yokes. With the 100mm extension at the rear the seat height may be an issue.
 
Hi Chasf

The 4 stud bevel box comes from the fact that the previous owner built the bike up from bits - ST frame, G/S engine and bodywork, GS forks and tubeless wheels. The forks were chosen as an upgrade to the G/S forks and the front wheel would have been necessary with the larger diameter spindle. I don't know whether the 4 bolt hub was due to parts availability or to have a tubeless on the rear to match the front. For me, the price was lower than an original G/S and with plans to modify it anyway it made sense not to buy a more expensive original bike.

I have seen the Prutser triples but I seem to remember they cost something like €600 and my budget won't won't stretch that far.

Unfortunately there doesn't seem to be a low budget way forward. I haven't yet ruled out making do with cartridge emulators in the GS forks, however having read more about the G/S and GS bikes, I now know that the tubeless rims are a lot heavier than standard rims and are also on my list to change, especially as I would prefer an 18" offset rear wheel to increase tyre options. Fitting emulators would be cheaper but unless my spare GasGas wheel can be fitted to the GS forks (the wheel itself could but I suspect getting the brakes to work would be challenging) it would mean having the hub re-drilled if I wanted a standard rim - more expense.
 
I detailed the low budget way forward earlier, the GS forks can be made to work as well as any, with a slightly softer spring matched to a soft, good quality shock.

Read Ohlins

Remember that the GS forks have compression and rebound damping in different legs so are easier to fine tune than some.
The HPN inserts on my GS forks on my GS have adjustable damping and work best with the rebound set at around 75% of of the max and compression around 25%, depending of course on the ambient, terrain and age of the suspension fluid.
Which also tells you how precise the final tune has to be.

It may be possible to reduce the length of the preload spacer in the GS forks, it is certainly possible to have say 5 wt suspension fluid in compression and 15 wt in rebound, and even just Synthetic Suspension fluid makes a noticeable difference to the way the forks work.

Just bolting on bits from other bikes is unlikely to be an improvement, you still need expert setting up after they are fitted, and with the same degree off expertise applied to the stock components they can be made to work equally well.

All you loose is the look, and these days the look seems essential if you are in the business of selling motorcycles.
But if yours is a keeper----------.
 
Just in case there is any doubt, the plan is that the bike is a keeper. I enjoy working to improve my bikes and value function over form. I'm also too much of a cheapskate to follow fashion for the sake of it. If making the original forks work sufficiently well is significantly cheaper than replacing them, then that is the path I will take, providing I can make do with the GS wheel. It does however seem a shame not to try to make use of a perfectly good Excel wheel which is next to worthless here on Cyprus because there are so few GasGas bikes.

While I wouldn't claim to be a suspension expert, I am able to set up the suspension on a bike, within the limits of oil height and damping adjusters for forks, preload and damping on the rear. Stripping down a set of forks to replace seals and bushes is no problem at all and I have no doubt I could dismantle the shim stacks in a set of forks and replicate a known good setting. Beyond that, it is time to call in the experts.

I read a thread about the GS forks on ADVrider yesterday which suggested that the compression leg only really affects compression damping towards the end of the stroke since the damper rod is tapered - sort of an anti bottoming out feature - and that the rebound leg actually provides the main damping in both directions. It also described how damper rod forks provide progressive damping - not by the amount of compression but by compression speed - the faster the compression the greater the resistance. The description continued that what is required is divergent damping - plenty of damping of slow speed compression to resist fork dive but less resistance to high speed compression to allow the wheel to respond over bumps. This is provided by modern forks, and to an extent by fork valve emulators, and allows the front wheel to float over hard bumps while maintaining enough damping to control fork dive under braking.

The description seems to match what I am experiencing, The compression damping feels about right under braking but whenever I hit a bump the impact is sent straight through to my wrists, one of which is recovering from scaphoid surgery in November. Based on the description above, I could fit softer springs and attempt to reduce the damping further but to get the forks to work as I want I am going to have to consider either cartridges or cartridge emulators.

Gold-valves are the cheapest option but only fit to one leg, don't adjust rebound and must be removed from the fork to adjust compression. I also came across these which appear to get round all of those issues while still being half the price of the cheapest cartridge inserts. Conveniently I have friends in NZ so could probably avoid the VAT on import.
 
I wouldn't pay too much attention to the self styled experts on ADV, there is some incredibly imbecilic junk posted there.

I am short on theory and long on practice. I seem to be one of the few who have discovered that " current technology does nor permit the manufacture of springs which are progressive to any meaningful degree " or who has discovered that the single click adjuster on Ohlins style shocks actually adjusts compression and rebound ,or that the best quality synth suspension fluid will improve he action of most forks.

Suspension is all about balance, front to rear, so to discus forks in isolation without stating what they are working with at the rear just doesn't make sense.

When I jack up the preload on my twin shock for a passenger if I fail to wind it down again for solo riding it is the harsh fork action which reminds me more than the action at the rear.

Which is why I suggest that you decide on the rear shock and spring before you start experimenting with the forks. And possibly decide on the tires too!

My G/S has a Ohlins with a spring a fair bit softer than the tested at 425 lb spring on the WP it replaced - I found it on Ebay for a couple of hundred dollars as it wasn't the G/S specific model although it had been fitted to one.

The WP is still livable at a similarly modest price, had a service not long before it was replaced but the spring suits a RTW amount of luggage r rather than solo riding.

Once you have a compliant well damped rear it is a question of setting the front to match, and around 10% more rider sag seems to work for most.
My G/S has stock forks, with the softest factory 36mm fork spring and 5 wt synth fluid, Forks were finally dialed in with washers over thm, even on washer made a noticeable difference!
The GS forks on my GS HPN inserts have a spring which gives around 65mm rider sag which is around 5mm more than the rear.
It ha the Ohlins magic carpet both ends
Havent measured the G/S sag but it is a little more at both ends. Both float over bumps, the GS slightly better.
Reducing the air gap by increasing the oil level will give a progressive action a bit cheaper than these inserts, which will still need dialed in for a off road bike as they are for a stiffly sprung road bike.
 
No, could you summarize it into twenty or less for me, please.
If you can find twenty sensible words in it, that is.
 
I dipped into it, just the usual stuff and nonsense from know it alls who haven't a clue clue what they are doing.

Maxton do know what they are doing, and 100% of what you spend will be spent on what matters, a custom made latest technology insert which will be made specifically to suit your requirement, and will perform flawlessly, right out of the box.

Even the old tech HPN insert in my GS work better than any USD conversion I have compared it with, and the Maxton inserts will be another step up from them.

Might be better if you learnt something about suspension before you post, and IMHO ADV s not the place to learn it.
 
Have you read this thread rossi?
an-unholy-union

I've read some of the unholy union threads but haven't read through all of that one yet. I suspect that DRZ forks would be a better option than 50mm WP's though, if I take the fork swap path, purely because of availability.
 
I dipped into it, just the usual stuff and nonsense from know it alls who haven't a clue clue what they are doing.

Maxton do know what they are doing, and 100% of what you spend will be spent on what matters, a custom made latest technology insert which will be made specifically to suit your requirement, and will perform flawlessly, right out of the box.

Even the old tech HPN insert in my GS work better than any USD conversion I have compared it with, and the Maxton inserts will be another step up from them.

Might be better if you learnt something about suspension before you post, and IMHO ADV s not the place to learn it.

I’m sure the action of the standard GS fork can be improved with cartridge emulators but at the end of the day their performance is limited by the diameter of the stanchions. The flexing soon becomes a limiting factor if you have an improved front brake or a braced frame
 
I’m sure the action of the standard GS fork can be improved with cartridge emulators but at the end of the day their performance is limited by the diameter of the stanchions. The flexing soon becomes a limiting factor if you have an improved front brake or a braced frame

I agree. Better to have a set of forks designed from scratch to perform than trying to adapt on improve old components. I should be careful though because that line of thinking would also suggest a new bike rather than improving an airhead. ;-) The question is where to compromise. I do know that spending lots of cash would result in divorce though.
 
If Moto GP bikes can struggle through with 42 mm forks it is hard to see how anyone actually needs 50mm forks.
Perhaps they like the feel of them in their hand-------------.
 
A billet SJ top triple and SJ style lower brace work wonders for the G/S fork.
But remember, the forks are unbushed, and most will be well worn and slopping around enough by now that a little flex isnt going to make to much difference to the way they move!
Most folks also tend to ride the bike that they are on, and adopt a riding style which masks any deficiencies in their equipment, probably without even realizing they are doing it.
You just have to grab the thing by the scruff on the neck!
 
Still wrestling with the options for the front end. I am certain that the GS forks could be improved with a set of lighter springs, and possibly cartridge emulators but this is still going to cost a few £. With most of the front end from my wrecked gasgas available it has the possibility to make a cheap upgrade if it can be made to work. So I had a quick measure and might have stumbled across something useable.

I have already checked and the bearings have the same outer diameter as the BMW. With the forks still on both bikes my measurements aren't completely accurate but the GG stem looks like it is about 5 - 10 mm longer so it should be possible to pack it out with a spacer providing the stem isn't tapered just beneath the bearing. Other dimensions come in between the DRZ yokes and Prutser yokes - 25mm offset, fork spacing around 195mm - and the pinch bolts on the lower yoke don't interfere with the steering lock. While it will still reduce the lock compared to the GS forks, and the width of the USD forks may make it non-viable, it has got to be worth pulling the yokes and from the bike and offering them up to the g/s.

Unfortunately the forks are well beyond use but I have everything else and if the yokes can be made to work I could pick up a set of used forks relatively cheaply and can get a 320mm disc for £100. If I sold on the current GS front end, which is non-original anyway, it could be a free upgrade. Hmmm.
 
Still wrestling with the options for the front end. I am certain that the GS forks could be improved with a set of lighter springs, and possibly cartridge emulators but this is still going to cost a few £. With most of the front end from my wrecked gasgas available it has the possibility to make a cheap upgrade if it can be made to work. So I had a quick measure and might have stumbled across something useable.

I have already checked and the bearings have the same outer diameter as the BMW. With the forks still on both bikes my measurements aren't completely accurate but the GG stem looks like it is about 5 - 10 mm longer so it should be possible to pack it out with a spacer providing the stem isn't tapered just beneath the bearing. Other dimensions come in between the DRZ yokes and Prutser yokes - 25mm offset, fork spacing around 195mm - and the pinch bolts on the lower yoke don't interfere with the steering lock. While it will still reduce the lock compared to the GS forks, and the width of the USD forks may make it non-viable, it has got to be worth pulling the yokes and from the bike and offering them up to the g/s.

Unfortunately the forks are well beyond use but I have everything else and if the yokes can be made to work I could pick up a set of used forks relatively cheaply and can get a 320mm disc for £100. If I sold on the current GS front end, which is non-original anyway, it could be a free upgrade. Hmmm.

As you say,it will easily be fitted.
It really depends on the riding you intend to use the bike for.
I’ve ridden loads of converted GS’s with upside down forks,
The lack of lock has me out.(unless done properly)
It’s that one off manoeuvre that will catch you out,with potentially painfull results.
It’s hard to explain how weird it is to attempt a uturn with a shit steering lock,the bikes running wide and ,,you fall over.:comfort
 


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