A few thoughts about progressive fork springs...
 

...well quite a lot of thoughts really! ;)

Thought it might be worth sharing what I’ve discovered with progressive and linear fork springs on the Tenere, having now tried both Yacugar progressive and Ohlins linear springs back to back. I must point out that I am no suspension expert, although I have had some advice from both FTR and Maxton. What follows is just my humble opinion based on a bit of professional advice and some first-hand experience. This may be of help to someone out there thinking about changing their fork springs, but then again you might well have changed your fork springs and be more than happy with what you’ve found (in which case I wouldn’t bother reading on!)

I never intended buying two sets of fork springs (bit extravagant), but problems setting the suspension up to work properly for me after fitting progressive springs led from one thing to another and eventually to linear fork springs.

A tale of two springs…

I fitted Yacugar 0.51-0.79Kg/mm progressive springs (the starting rate being very similar to OE) and recommended SAE15 oil last winter. I was initially well impressed, mainly on shorter road rides and a few light, low speed green lane jaunts: Less brake dive, less bottoming, more direct steering and all-round sharper handling on the road. However, after a couple of longer rides (on road) I noticed I was finding things more tiring than usual due to a slightly harsh, jittery feeling, rattling over minor bumps and imperfections particularly as speed increased. I put up with this for a fair while and more miles, trying to remind myself that the trade of was better handling, but eventually some experimentation was needed.

Initially, increasing preload helped smooth things out but at the expense of sag (the bike riding too high at the front and the front wheel much more prone to leaving the ground!) Not happy; so changed the oil to SAE10 and reduced preload, with an immediate improvement in comfort (and correct sag again), but ended up with a bouncy ride over bigger bumps and rougher terrain. Adding preload now made things worse. This all suggesting to me that I was struggling to get the damping to match the spring rate at the various points in the springs travel; Compression damping being too great with the SAE15 oil giving a harsh ride, and rebound damping being a problem over large bumps with the SAE10 oil. So I thought stuff this, I’ll shell out �100 and see what linear springs can offer. Cue Ohlins 0.60Kg/mm (6.0N/mm) springs…

Fitted the Ohlins springs a couple of months ago with SAE10 oil, the standard air gap (all as recommended by Ohlins) and wow, what a difference. Sag easily set and spot on for my weight, firmer (than stock) but compliant ride, controlled damping and no harshness in the upper part of the fork’s stroke and no bounciness in the lower part of the stroke. Dive on the brakes is a little more than the progressives, but actually I think this gives a better, more consistent “feel” through the suspension when braking. Consistent being the key word, but then the springs would be, they’re linear!

So what's the problem with progressive rate springs then?

The first problem I think is that the initial softer part of the spring just gets used up straight away leaving a limited amount of travel for the stiffer portion to deal with, resulting in less compliance, less comfort and less traction. The second problem is setting the sag to any degree of accuracy is almost impossible. The third problem (the big one) is that damping rates need to be matched to the spring rates, in particular rebound damping; with progressive rate springs this is impossible. Damping is always a bit of a compromise but adding progressive springs to the equation just makes the job so much more difficult to achieve.

Here’s the rub with the XT, its damping rod forks. Being a very basic system (my 45 year old BSA has the same design!), it’s all a massive compromise between rebound and high/low speed compression damping; fitting progressive springs just makes the compromise greater. The high speed compression damping action is not sufficiently responsive or progressive by design and only just works with linear springs so doesn’t stand a chance with progressives, especially with heavier oil which won’t flow through the damping orifices as quickly, giving a slow response. There's not a great deal you can do to alter that other than change the oil weight/viscosity, and that mostly controls the low speed damping response... In real terms, the amount and speed of dive on the brakes rather than the ability of the forks to soak up sudden jolts and bumps in the road surface. This is why I guess the first thing that everyone (me included) notices after fitting progressives and SAE15 oil is that dive on the brakes is hugely improved – but it’s not all down to the springs.

So what did changing to lighter fork oil (with the progressive springs) achieve?

The lighter oil flows a bit better and gives an improvement by lessening high speed compression damping (rapid small movements), giving a more pliant and plush ride (the perceived improvement in comfort that I felt). Unfortunately, that brings you into conflict with the rebound damping requirements (you’re not going to have enough) which is even more of a problem with progressive springs as spring rebound is not linear (the bounciness that I felt at the bottom of the stroke).

My guess is that Hyperpro/Yacugar (and others) recommended SAE15 oil to bolster the rebound damping in order to better control the return stroke with from within the higher rate portion of the spring. The downside is that it seriously hampers the compression damping (particularly as the OE fork damping orifices are designed to work with much thinner oil), making it much more aggressive in the upper part of the stroke controlled by the lower rate portion of the spring, giving a harsh ride; in effect you’re riding on the oil (compression damping) rather than the spring!

Conclusions?

If you’re an average weight rider (90Kg kitted out) or slightly less (like me at 85Kg) I‘m really not sure progressive springs are the answer, due to the fact that you aren’t going to make best use of the higher rate part of the spring and you’re going to be rattling about in the over-damped (with SAE15 oil) softer part of the stroke. I guess, maybe progressive fork springs are better suited to the heavier rider? Then again, if you’re heavier I’m still not sure they’re the ideal because to get your sag right you’re going to have squashed out most of the soft part of the spring and be riding on the higher rate part of the stroke, nullifying much of the progressive effect of the spring, so you might as well have gone for a stiffer than stock linear spring in the first place?

After trying out both spring types I’m not convinced the progressive springs really work (for me), mainly because you can only achieve the correct damping for either the higher rate or the lower rate part of the stroke, but crucially not both (or for that matter the bits in between). Adjustable high/low compression and rebound damping would be much more effective and would have cured most of woes (but unachievable with XT forks), but even clever cartridge/USD forks can’t vary damping within a single stroke to match a progressive spring. As mentioned earlier, I think the improvement that most people who fit progressive springs notice first is reduced brake dive, but I reckon that’s more likely down to the original springs that were replaced being too soft in the first place and the change to heavier oil, not the fact that the replacements are progressive.

Basically I reckon progressive springs might be an issue if…

• You’re heavy, they’ll blow past the soft part early then ride hard and too low, so you’ll attempt to increase preload to get the ride height back and make the ride even harder.
• You’re light, the damping will be too great in the soft part and ride harsh (plus you’ll never use the stiffest part anyway), so you’ll attempt reduce oil weight and end up with too little damping in the hard part and bouncing.

Of course, everyone is different, every bike and the way it’s used is different. You may think what you have just wasted the last five minutes reading is a load of twaddle! On the other had you may not? You may, perhaps, have fitted progressive springs to your beloved Ten and love them, but for me, this is what appears to work best…

• Linear springs correct for rider weight/conditions and damping oil that exactly matches the spring rate (and matches what the damping orifices in the forks can cope with at speed).
• Use the air gap/oil level (not the springs) to control bottoming resistance and progressive stiffening at the end of travel.

Or better still fit WP forks (if you can afford them)!

Notes:

Whilst asking around I found that apparently Yacugar and Hyperpro fork springs are one and the same product, made in Holland in the same factory, but supplied in a different box (and also I’m informed that Hagon and Wirth progressive springs are the same as each other too.)

All the fork oil I used was Fuchs-Silkolene, so I could make direct comparisons, also Fuchs is one of only a handful of oil companies that use SAE grading which is comparable between other brands that also use the SAE designation ( a lot use just # weight, # w and Ohlins their own numbering system all of which aren’t really comparable, although Ohlins do supply a comparison chart to SAE spec).

Wow, that's quite a post! Given that I'm waiting on my Hyperpro progressive springs at the moment I'm wondering if I've shelled out my cash for nothing! I've got Kev's spacers as well so before fitting the Hyperpro's I might just try the spacers and a change of fork oil first and see what happens. What volume of fork oil were you using?

Cheers.

Great feedback on your experience.

Unfortunately you can't paint all progressive springs with the same brush, there are many different rated springs out there. 80% of suspension setup is a personal thing.

I fitted Hyperpro's to the front, the difference was immeasurable. I've not experienced the same harsh front end as you have. However, I did the rear at the same time - maybe something in that ?

+1 I quite agree Kev.

I hope I made that clear in the OP, if I didn't, then just in case... ;)

I just found it quite interesting experimenting with the front end and seeing what could be achieved (or not). I think the long and short of it is; whatever your suspension choice/preference/setup is, there's much to be gained by having a fiddle and trying a few things out. It's surprising how much you can change/influence, even with an essentially "non-adjustable" fork setup like on the Tenere!

+1:bienvenido:

Don't get me wrong, any replacement fork springs (progressive or linear) are a massive improvement over the OE items!


Far be it from me to tell you what to do! However, IMHO trying a fork oil change and the spacers would be a good, sensible and cost effective starting point.

As for oil volume... It's actually more to do with setting the the air gap correctly (space between top of oil and top of the fork tube with the fork compressed and spring out), the oil volume is a rough guide to get approximately the right amount in the fork to work from. With the progressive springs I started off with an 30mm larger air gap (less oil) as recommended by Yacugar in their instructions (this is mainly to take into account the larger diameter of the spring's windings (which displace more oil than the originals). I then experimented with small adjustments in level, keeping a careful note of what I'd done. With the linear springs I started with Ohlins recommendation of sticking to the OE spec air gap (which I can't remember off hand).

Just remember the golden rule of tuning suspension (or anything else for that matter) - Change just one thing at a time and record every change you make.

I'd go way beyond 80% on the suspension thing,it was a nice read,and for anyone that hasn't got one here's my favorite piece of kit.

http://yambits.co.uk/advanced_search...tion=1&x=3&y=2

I always set the air gap by measuring the oil height, as I found setting the oil level by volume = mm never equals the correct air gap height.

Excellent advice - thanks for that. I've never played around with forks much before (haven't really needed to on my dirt bikes as the adjusters generally seem to do the trick) so looks like I'm in for a bit of a steep learning curve - not a bad thing!

ohlins ??
 

Hello, im UK based, were would i get some ohlins springs for my xt660r 2010?

found some but there �110 plus !!

any ideas.

Give FTR Suspension a call.

01284 752102

Always bought mine from Harris as they are the importers makes life easy.

Tried ftr said they didn't do them,

Found another bloke cant remember. But said he'd find out about stock.



Found motorsport race prep firm who say they can get them made bespoke for �80. They just need the exact size of spring.....



Who new its be so hard, rang loads of places




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A few thoughts about progressive fork springs...
 

FYI - You can get Ohlins springs for the X from Off The Road in Germany. They are about �80 plus delivery, which is about �8 if I recall.

Hi, if I get the time planning to fit Hyperpro progressive springs front and rear to my Z this wkd

Anyone got any top tips or lessons learnt that are not in the instructions??

Also has anyone got any associated settings they have used. I am 15 and half stone.

Cheers

Phil

I checked off the road, they said ohlins arnt recommended for 90+ kill rider n recommended the hyperpro ?

Reading around seems to me ohlins are a better option, but ....



Confused.......com




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That's just plain bizarre? :sad1:

If they don't recommend them, then why sell them? If they're that dangerous why do Ohlins, the world's premier suspension brand, even make them?

Maybe there's just more profit margin in the Hyperpro...

I have read that the hyper pro is thicker and stronger.

A few thoughts about progressive fork springs...
 

They (progressive springs) are only made of larger diameter windings so they can achieve their maximum (end) rate, which is higher than that of a comparable linear spring. The "strength" of the spring steel is more related to its quality, much less so its thickness, unlike mild steel. Thickness is just one of several factors involved in achieving the desired spring rate in a coil (coil spacing being the other major factor). A spring's "strength" (that at which it will break) and its "rate" or not directly related; you can have a weak spring with a high rate and a strong spring with a low rate.

So should i believe them n buy the hyper pro ?



Being a tall 90+ kill rider that wants 80/20 off road,

I am hating the std suspension :( lovin the bike.....


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Now that's a decision only you can make!

Both the springs mentioned will, without question, improve your front end. The only way to find out which is best on the X (and suits your riding style) is to do what I did and try both! ;)

Haha i wish icould afford that,

Reading ur post ohlins sound like the one

Reading off road Germany, theyre saying no?



What u say makes sense to.me



Unless there ohlins are in someway different to yours,,,,,



****** :(


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Would it be ok to just change suspension on the back instead of change the OEM in a aftermarket system? Is it worth it? I want once i have my xt change first the springs front-back or springs front and system back....

Anything as an improvement of the OEM setup!

There are a good few riders who have changed just the springs (front and rear) and been very happy with the results. It will be better than stock.

All I'd add is that changing the rear shock spring is only going to be any good if the damper is still in good condition and even when new the OE damping was never that great!

I think that there isn't much rebound with the front and rear standard suspension. On continual rough sections, the springs seem to compress up and get harsh and are unable to rebound quick enough.

I suspect that a stiffer spring might help this by increasing the rebound action a bit? Also the suspension will sit further 'up' giving you more suspension travel. The standard suspension is so soft that when sitting on the bike, the travel has already sagged to half the total travel.

Luckily I use mine mainly for pretty smooth roads at the moment, is at least $1100 to do a proper job on the front and rear suspensions in Oz. This is with new springs, valving, actuator (emulator) included. Extra adjustments etc = more $.
I will have to do it eventually.

Have a chat to Nic at TecknikMotorsport as he runs deals on the Tenere where he re-valves the standards Sachs rear shock and does the complete job, springs, emulators and oil etc on the fronts... All for $750.
I got mine done only I elected to just get him to replace the rear shock with a Yacugar...$1080 from memory.
Awesome, different bike on and off road!!
Matt

That certainly sounds like a good price.

A little after the event, but I overhauled my forks on my XTR with Racetech springs/emulators supplied by Shock Treatment. $370 delivered and the satisfaction that goes with doing it yourself. I bought Racetech's suspension bible a year ago to get my head around the front end on the WR. Well worth the money. Only problem now is that the front end highlights just how poor the rear end really is offroad.

The following link may also be useful?

http://www.xt660.com/showthread.php?...light=emulator

Just picked up no this very interesting thread, thought it might be worth adding to the above statement that for those of us in Oz that may go the TecknicMotorsport route that according to there website they will also do the Double Bearing Mod for you to the sprocket carrier.

Just to update things (since I began this thread a while back) I also added Teknik V4s valves to my forks last year. So to sum up, I am now running Ohlins 60N springs, SAE10 oil and cartridge emulators, which I would suggest (IMHO) is probably about as good as it gets without going USD.

As others have mentioned, gold valves/emulators/intiminators/terminators (or whatever you want to call them!) do make a big difference to the damping. It is so much easier to set up and tune the damping characteristics to match your chosen spring rate (whatever that happens to be). Without the valves you are totally reliant on the rather hit and miss practice of experimenting with different oil viscosities.

Cost of suspension upgrades
 

I saw on some U tube show here, a test on a new 660 with upgrades & quoting an upgrade to technik suspension, all round for $990Au ?
I'd be interested for that amount of cash outlay.
Last year, I spent about $350Au having an Ohlins rear shock from my parts DR 650 reconditioned & fitted to the running DR. Heaps better to ride :045:

This seems the way to go.
To confirm - the std fork springs are linear in rate? I kinda thought they were progressive as standard being an adventure bike.
Years ago, when I raced off-road while living in Zimbabwe, I cut my fork & shock springs on my race bike to the rate I worked out I wanted then made spacers to bring the spring length back to where I wanted the preload & the difference was phenomenal! Has anyone done that to these springs? Big leap of faith as there's no going back but back then parts weren't too easy to get so we did it ourselves.

Where would you say the best place to get the emulators for the forks from?
Thanks

2008-2012 XTZs have Paioli internals linear springs and short spacers. 2012> XTZs have KYB internals and progressive springs/longer spacers. They way to spot the difference externally is to look at the fork preload adjusters; the linear sprung bikes have recessed hex key adjusters and the progressively sprung models have raised screw and locknut adjusters. AFAIK the X/R models continued with linear springs from 2004>.

The only place I know of the makes them specifically for the XT is Teknik Motorsport in Australia (which is where I got mine from). Others from Racetech etc. can be made to fit, or it isn't beyond the realms of man to make your own.

Many thanks for your help again 👍🏼

One of my sportsbikes came with dual rate springs. The thing rode really well on ordinary bitumen and I couldn't see why my mates with the same bike had taken it off to a specialist for reworking.
Until I had to brake deep into a corner with corrugated bitumen. What happened then was 'packing' I was told. The softer spring section allowed compression momentum to build up, to reach full compression with compromised grip the result.
Another problem with progressive or dual rate springs is in setting static sag and trying to get the optimal compromise between ordinary load and touring-with-luggage load. When you add luggage (or a pillion) the forks more readily compress beyond the best sag setting.

Following this thread with interest. ..I have been told that my Tenere has progressive fork springs as standard. ....not sure. .? Steve

It will have. Somewhere mid-way through 2012 the internals switched to KYB and with it came short progressive springs and much longer spacers than before. It's easy to tell the bikes with KYB internals as they have the raised adjusters on the fork tops.

Thanks Pleiades. ...do you think they are reasonabley good springs....I'm finding them ok so far. Would it be better to upgrade the rear shock first..? Steve

I don't have any experience of riding a post 2012 Tenere, so I'm not really in a position to comment. However, if you're happy enough with they way the front end works, then I shouldn't worry about changing anything.

TBH, I've heard a lot less in the way of negative comments made about the forks from the owners of later bikes compared with what owners have said of the pre-2012 ones. This would indicate that the KYB forks maybe better behaved? There are though, several forum members (with post-2012 XTZs) that have gone the Ohlins linear route and noted an improvement in ride and handling, and a few who have done the re-valve/emulators modification with decent results too.

As for the shock... Again, I wouldn't necessarily change it for the sake of it (unless you really properly don't like it). It will start to die at some point, anywhere between 10 and 20K miles usually (mine lasted just over ten), and it makes sense to change it then. You may as well get your money's worth out of it! However, an aftermarket shock does make a huge difference to the bike though and is well worth the outlay IMO.