twitchy steering behaviour 2015 EC200

[hannesd]

HI,
i just got back to the gasser family with a 2015 ec200, having owened an older ec300 a few years back.

so my question is, can a bike be rather unstable at higher speeds due to too little sag and/or lesser quality tires?
i got the bike with a fresh set of tires of the reputable brand "RAZORBACK" feral 2 type. these feel as very soft studded tires, never touched such soft tires...
the tires do have some new BIB mousses mounted.
there's also a terrible imbalance in the rear wheel.
in the stand and on the street, from 50-60km/h and more the wheel starts to occilate up and down :-/
i'll take the tire off and inspect how heavy the tireclamp weighs.

on testride the bike felt very high in the back, after measuring, it only had about 75mm of race sag instead of the recommended +-105mm.
i set it at 95mm now and still feels less stable then i'd like.
will the extra 10mm make a noticeable difference in stability?

the bike is ok to ride, just not that confidence inspiring +60-70 km/h (over uneven surfaces)

curious for your toughts

cheers, Hannes.

[Doc Brown]

95mm sag is not enough, adjust it to 110 dynamic and see if you can be inside the range of 30 to 35mm static. Rear low = more stability, lazier steering.

The rim lock is indeed very heavy hence the wheels oscillate at higher speed and produce a humming noise. That's pretty common and most noticable on tarmac or public roads.

If the bike feels twitchy it can be the tires but I doubt it. For testing you can increase tire pressure front and rear to 1.1 bar and see if that changes anything. Another reason could be a defective shock or if the clickers are set incorrectly....

[hannesd]

ok, i'll increase the race sag.
tire pressure can't be altered since i have bib mouses.
the humming noise, i am familiar with,in my case this is just shaking the whole bike
clickers are set per manual.

[hannesd]

set the sag and it's all good now. the nervous steering is gone, with only 10mm more sag.
about the imbalance, there's about 300 grams of imbalance
i managed to temporarily fix some 200 grams counterweights to the spokes and that too is ok now.
it is very weird to have such a big weight difference though.
i'm guessing a big heavy rim lock along with the cheapest tires...
i'll just wear them out and then replace them with some quality ones.

[RBrider]

Originally Posted by hannesd

set the sag and it's all good now. the nervous steering is gone, with only 10mm more sag.
about the imbalance, there's about 300 grams of imbalance
i managed to temporarily fix some 200 grams counterweights to the spokes and that too is ok now.
it is very weird to have such a big weight difference though.
i'm guessing a big heavy rim lock along with the cheapest tires...
i'll just wear them out and then replace them with some quality ones.

I always balance the tires on my dirt bikes as well as the dual sport bikes.

Go to a street bike shop and buy an assortment of spoke weights like they use on Harley spoke wheels. Or, just drop off the wheel/tire assemblies and have them balance them for you.

Since you've set the rear sag correctly, why not check the front sag and make sure it's in the ballpark. Put a couple of electrical zip ties around the fork tubes up close to the seals. Take the bike off the stand and sit on the bike. Then put it back on the stand and measure the distance from the seals down to the zip tie. It should measure around 100 mm or 4 inches. It might not be perfect, but it'll be close.

RB

[Anders]

Originally Posted by RBrider

I always balance the tires on my dirt bikes as well as the dual sport bikes.

Go to a street bike shop and buy an assortment of spoke weights like they use on Harley spoke wheels. Or, just drop off the wheel/tire assemblies and have them balance them for you.

Since you've set the rear sag correctly, why not check the front sag and make sure it's in the ballpark. Put a couple of electrical zip ties around the fork tubes up close to the seals. Take the bike off the stand and sit on the bike. Then put it back on the stand and measure the distance from the seals down to the zip tie. It should measure around 100 mm or 4 inches. It might not be perfect, but it'll be close.

RB

I never balance my Gasgas' wheels. I don't go fast enough to notice any problems, even with mousses and traditionals rimlocks. On my most frequently used rims, I use T-Lock (an alternative to Tubliss), so there is no problem with imbalance there (apart from any imbalance from the tire itself).

On the issue of front sag, I always have an o-ring around one of the fork legs to keep an eye on the amount of travel I use. Dependinmg on the track, I tend to soften up the comression clicker to use most of the travel. I haven't measured the front sag in a while, but I seem to remember it being quite OK.

[hannesd]

100mm of sag in the front, you must be joking right? 50-60mm in the front seems more like it...

[Zman]

You can also compensate by raising the forks in the triple clamps.

[hannesd]

Originally Posted by Zman

You can also compensate by raising the forks in the triple clamps.

true, but i kept some left to raise if i ever get to a sandy track. easier to raise the forks then to alter rear sag ;-)

[Doc Brown]

Originally Posted by hannesd

set the sag and it's all good now. the nervous steering is gone, with only 10mm more sag.
about the imbalance, there's about 300 grams of imbalance
i managed to temporarily fix some 200 grams counterweights to the spokes and that too is ok now.
it is very weird to have such a big weight difference though.
i'm guessing a big heavy rim lock along with the cheapest tires...
i'll just wear them out and then replace them with some quality ones.

Glad you solved the main issue. Don't underestimate that 10mm is quite a lot.
Even if others will have a different opinion I would not change the forks sag (by using different springs and/or spacers) if it works good now.
9 out of 10 suspension problems come from the rear except a rider is far too heavy/light for the springs.

I had a huge imbalance shortly and I could not imagine what it was as I use good quality rim locks (still about 170 grams). Later I found out that the mousse was the case. Tried cheap Technomousse and it was the cause.

If you don't ride on public roads or a lot on tarmac balancing the wheels is nonsense in my opinion. From about 50 riders I know only one balances his wheels, but he is a dentist so I don't take him too serious

Considering what your nick name is, you are from Europe, right?