2008 front suspension softening?

[st1300b]

So I've got around 10,000 on the bike, and last year around 6 or 7,000 miles I started to notice that the front suspension was softening?

This is difficult for me to explain, but I'd describe it as instead of the tire coming up over bumps, it's feels like all the absorbtion is at the handlebars? It's not vibration, so much as it softness.

I asked about adjusting the fork settings, but apparently there aren't any mechanical adjustments?

Question 1 has anyone else experienced anything like this?
Question 2 Is this solved by simply adding or changing fork oil? I can't imagine 10,000 I need a spring replacement...

Looking for suggestions.......

 

[Mellow]

Any chance you had a tire change at that time and moved to different tires? Mine has 50k miles on it and I haven't noticed anything but I'm not sure I would ever notice.

 

[st1300b]

No, I've only had one change thus far and the same brand tires were installed...

 

[RaYzerman]

It isn't unusual for fork springs to sag from new after a few thousand miles, if only you knew the sag when new vs. now. The bike is also undersprung somewhat, nor are there any adjustments for preload or damping, and you would benefit from a fork spring upgrade. If you want to go on the cheap, you could add spacers depending on the sag desired for your particular weight, etc.. Damping is dependent on fork oil weight and amount.

If it were my bike, first thing I would do is upgrade the suspension on an ST. But that's a personal preference. It all depends on what kind of rider you are. I would start by measuring sag and reading up on suspension settings/upgrades. You could start by looking at the How To section in this site.
http://www.sportrider.com/motorcycle_suspension_guide/index.html

 

[billo]

It sounds like you're describing a stiction problem. Possibly the axle tightening procedure was not followed?

Bill

 

[dduelin]

Honda uses very good springs in the ST1300. I measure mine for spec each time I change the fork oil and the last check at 73,000 miles they had not shortened or sagged noticeably from new and were at the long end of spec. That said, the stock spring is not stiff enough for riders over 150-160 lbs and many owners upgrade to stiffer aftermarket springs. Although there are no built-in adjustments for preload or dampening one can change the preload with spacers and damping characteristics by changing the viscosity and level of fork oil. I don't think the springs are worn out at 10,000 miles but I don't really know what the problem is that you are describing.

Mechanical preload adjusters use stepped devices that increase or decrease pressure on the springs inside the fork when they are turned. I changed the spacer length to increase preload by 16 mm. I am 150-160 lbs and like the OEM spring rate preloaded like this. To speed up dampening I run a mixture of Honda fork oil to 6.7 wt. I like this combination very much.

 

[dduelin]

...........adding 3 oz of 15 weight fork oil. This will increase dampening just slightly, but it will reduce air space in the forks causing air pressure to rise more quickly adding more airspring for increased progressivity all through the suspenssion range. Don't try to put more than that though. Too much fork oil will cause hydrolic locking that will be hard on the fork seals. If this doesn't provide enough improvement for you then new springs or spacers are going to be needed.

I might be wrong but doesn't a higher oil level in the forks reduce progressiveness? Air space acts as a spring and less air space and more oil reduces this effect. More oil is less air space to compress - there is less spring effect from air compression and the suspension is less progressive. Less oil is more air space which softens or adds progression to the spring rate. That is my understanding anyway. I'll have to look it up tonight.

 

[FJRHank]

My experience was the OEM springs result in the ST being significantly undersrprung (in the front for sure).

I base this on my (mostly) emergency braking practice, which would always result in the forks bottoming out and the front wheel wallowing from side to side.

This is a picture showing the mark my fender extender was making (full compression of forks measured) when it was bottoming out:

Didn't have that many miles on the bike, maybe 5 to 10k, and only weighed about 150.

Now on the positive side, after installing sonic springs (the 1.2 version), the bike not only never bottomed out, it took bumps much better and rode through the twisties much better. It was almost like a different bike, it handled that differently.

 

[st1300b]

I really appreciate the feedback sofar. I am a larger guy, 6'2" and 270lbs so I'm making the suspension work! ha ha.

I'd like some conclusion on if more or less oil is recommended - and also if anyone else has any conclusions about the axel proposal mentioned above? I have had some issues (3 x back to the dealer for a front axel problem) since purchased 1 1/2 year ago. (it was new, old stock) Is it just coincidence, or could this be playing a part? Not sure...

 

[dduelin]

Hank,

If you measure the rider sag, then free sag, the numbers indicate the OEM springs are about right for riders of 150-160 lbs. This is subjective of course and there is room for preferences of riders. On your bike the fender extender was hitting the middle cowl - the stock fender does not do this.

I don't know for sure but the picture looks like there is 3.5" of distance between the bottom of the fender and the top of the scratch marks. That leaves .75" of travel left before bottoming? Also, a rear shock damping setting set too hard allows the ST's rear end to wiggle side to side under hard braking. I have experienced this at the track and occasionally on the street when practicing emergency braking. Too soft front springs wouldn't normally have anything to do with the side to side wobble of the front wheel you describe.

Before and after I changed preload I measured front suspension travel by placing a zip tie around a fork leg and sliding it down against the dust seal. Even under tire howling emergency stops the forks still had 9 or 10 mm of travel left with the stock set up. This "poor man's data acquistion device" works quite well. I also recorded short rides over the same bumpy pavement section ending with an emergency stop with a video camera aimed at the forks. They are on my YouTube page.

The ST needs more preload before it needs heavier springs if a light rider is involved. That is what a rider would do if the bike had adjustable suspension - try adding preload first. Adding preload does not change spring rate or make the spring stiffer but it does increase ride height and the force necessary to start compressing the fork. But since Honda did not give us this feature, spacers can be altered to suit.

 

[wjbertrand]

Your comments almost sound like the front got stiffer rather than softer. It's possible the springs have sagged to the point that you are riding exclusively on the stiffer part of the progressively wound spring I suppose. Besides the possibility of spring sag, the damping fluid will certainly degrade with time. Best bet would be to fit some aftermarket springs and fresh oil at the recommended level. Note that most aftermarket spring companies recommend lower levels of oil than Honda does. I think Honda sets the bike up for the 150-160Lb rider spring wise and then uses a combination of stiff compression damping and high oil level to reduce bottoming when heavier / more aggressive riders use the bike. A smaller air volume above the oil will act more progressive, i.e. its resistance to compression will be a steeper curve than a larger air volume. This can produce an extremely sharp rise in spring rate near the end of travel and make for a harsh ride. This is particularly true if your bike is already riding low with more than about 20% sag already.

 

[FJRHank]

Hank,

If you measure the rider sag, then free sag, the numbers indicate the OEM springs are about right for riders of 150-160 lbs. This is subjective of course and there is room for preferences of riders. On your bike the fender extender was hitting the middle cowl - the stock fender does not do this.

That's correct about the stock fender vs fenda extenda (mine anyway), but the point of the picture isn't to show that marks were made. It's that because mine did make marks (ironically and unintentionally), it's easy to see where the forks were bottoming out.

I did measure sag before installing the sonics and it was more then 2 inches.

I don't know for sure but the picture looks like there is 3.5" of distance between the bottom of the fender and the top of the scratch marks. That leaves .75" of travel left before bottoming? Also, a rear shock damping setting set too hard allows the ST's rear end to wiggle side to side under hard braking. I have experienced this at the track and occasionally on the street when practicing emergency braking. Too soft front springs wouldn't normally have anything to do with the side to side wobble of the front wheel you describe.

All I can say is that was my experience. And the marks (ironically again) show that. They all pretty much end at the same spot. Add in how it felt when emer braking, well it's difficult to misjudge that. There was no more compression by the forks, and the hard braking pressure had no where else to go... thus the wallowing back and forth feeling of the front tire.

Not sure of significance to this, but my bike was not ABS, so of course was only doing emer braking practice on very dry roads.

Before and after I changed preload I measured front suspension travel by placing a zip tie around a fork leg and sliding it down against the dust seal. Even under tire howling emergency stops the forks still had 9 or 10 mm of travel left with the stock set up. This "poor man's data acquistion device" works quite well. I also recorded short rides over the same bumpy pavement section ending with an emergency stop with a video camera aimed at the forks. They are on my YouTube page.

When I measured sag, had some friends standing on sides to balance, me on bike with full gear. And someone in front measuring high and low after helpers on side got bike fully compressed and fully extended. Can't remember where I found this procedure, it's somewhere on the web.

Myself anyway, if I'm going to that much trouble for a spacer (which one has to do on the ST re no adjustments), I'm installing Sonic 1.2kg. They really transformed the bike to ride a lot like my 03 VFR. It wasn't harsh, just firmer, and handled bumps, corners etc much better then before.

The ST needs more preload before it needs heavier springs if a light rider is involved. That is what a rider would do if the bike had adjustable suspension - try adding preload first. Adding preload does not change spring rate or make the spring stiffer but it does increase ride height and the force necessary to start compressing the fork. But since Honda did not give us this feature, spacers can be altered to suit.

One last thing I can mention re my experience, after installing the sonics, I put a piece of masking tape over those prior marks on the inner cowling. The intention was to see how far up the new marks went compared to the old. I covered about 3/4 of the marks, all the way to the top.

Guess what? Not one new mark showed up at all. None. Zero. I was honestly shocked. In addition, there was absolutely no feeling whatsoever of bottoming out. Nothing else suspension wise had changed.

Basically, I can't recommend the sonics 1.2kg for the ST enough. On their website it's evident it's the strongest spring they make, and it only seems to be recommended for the ST, about the heaviest sport touring bike going.

The only downside to add would be that the bike didn't really change much when passing semi's in "dirty air". Still had that twitchy feeling in the front. It *may* possibly have been worse then before, did not have a chance to test it that much.

 

[tlartist]

Install sonic 1.2 springs and redline fork oil either light or mix of med/light. Did this at around 10,000 and good to go. If you measure sag on the front you should see why you need to do this. Don't go by feel. Do the measurements. While you are at it get new spring on the back as well, or a whole new shock like I just did.

 

[SteveST1300]

+1 on the new springs and shock I replaced my stock springs with HyperPro fron and rear and it makes a huge difference no joke its like a different bike.

 

[dduelin]

If you just measure rider sag you find the stock fork setup gives too much sag, at least compared to popular convention, but not if the suspension can be tuned or adjusted to compensate. Rider sag is only half of the information needed for this. My rider sag was 47 mm or about 1 7/8". Road bikes should run about 30-35 mm or about 33% of available travel which would be 36 mm on an ST1300. Sag is simply the amount the suspension settles from completely unloaded and fully extended under the weight of the bike, rider, and cargo. In my case 47 mm was too much but Race Tech's spring calculator suggested the spring rate of the stock spring was about right for my weight. A check for this is to then measure sag of just the unladen bike. The difference between rider sag and static sag gives an indication whether or not the spring rate of the spring is correct for the weight of rider. Since the spring rate was OK for my weight and I generally liked the ride qualities of my bike but wanted to reduce dive under braking, increase available lean angle, reduce wallowing in fast sweepers & fast transitions the next step in tuning is to adjust preload and see if adding preload changes the sag numbers to the target values. If the ST had been given adjustable preload a turn of the adjusters would reduce sag, but would it be enough to reduce rider sag to 30-36 mm? Since we don't have preload adjusters we have to make changes in the spacers in the forks that sit on top of the springs. I made up several sets of progressively longer spacers from PVC pipe. In my case 16 extra mm of preload reduced rider sag to 36 mm.

If a spring is too soft it requires a large amount of preload so it does not sag under the weight of the rider and cargo compared to unladen bike. With the rider off the bike, too little sag indicates that it was excess preload than accommodated the rider weight. Too much sag without the rider (static sag) compared to sag with the rider on the bike indicates the spring is too stiff - not a problem with the ST except perhaps for riders under 130 lbs.

If I had not been able to reconcile rider sag to static sag the next step would have been to change the springs to higher rate, stiffer springs but for me the target values were achieved with stock. For heavier riders the stock springs would take too much preload to get sag right and aftermarket springs are in order right off the bat but if one is interested in knowing the details of their setup and really tuning for your weight and riding style you need both rider and static sag.

To the OP, a 270 rider is too much for the stock springs. If you wanted to get an aftermarket spring to accommodate you I suggest checking the Race Tech website and entering your weight into their spring calculator for the ST1300 and see what it suggests for you.

http://www.racetech.com/page.aspx?id=57&menuid=63

 

[tlartist]

I also had about 45 or 47 rider sag. Pretty much anyone should take proper sag measurements as described to see where you are at. I think for most Americans you will end up wanting to change/adjust, for the 1300 at least.

 

[ChucksKLRST]

+1 on the Sonic springs. My 03 ST1300 use to ride very choppy in the front end. Drove me crazy. The Sonic springs and new fork oil solved that that was about 50k miles ago. I now have 90k on the bike.

 

[st1300b]

Sounds like the Sonics come highly recommended, I will look into those further and appreciate all the input. Thanks all!