Dr650 speed wobble at 110km/h

[Monstaman]

So I lowered my bike on the rear spring bolt, reset my preload to my correct static sag with rider etc, and made it slightly firmer than the front for carrying shit, the shock bolt height dropped the bike 37 mm vertical from the wheel nut.

I dropped the forks through the clamps 20 mm to come closer to geometry however at 110 km/hr it does a little weave on the road, not bad but quite noticeable.

I put the forks back through the clamps level with the top triple again and this has settled it down a bit.

I am running full knobblies at present and wonder if this has a big influence, any input would be cool.

Signed Dr Jekyll or Hyde .... sure

[Squiggles]

*watches with interest*

[Monstaman]

*watches with interest*

...I usually charge for that

[Crisis management]

You've made a couple of erroneous supositions.
1. The suspension on a DR can be adjusted to make it work.
2. A DR will track straight on any surface.

Talk to Nordie or Bass if you want the suspension to actually work, the rest of us just assumed it was crap and carried on, by winding everything up tight mine worked ok but I'm only 70kgs....

[Bass]

I am running full knobblies at present and wonder if this has a big influence, any input would be cool.

Signed Dr Jekyll or Hyde .... sure

What tyres are you running and what pressures are you using?

What do you mean by "firmer" - damping or preload?

[GaZBur]

I also dropped the back and left the front standard when I put 17inch rims on the front. No handling issues re wobbles and have been up to 179Kph. I put the 21inch wheel with full knobs back on without altering the suspension back and found it surprisingly good up to about 130 Kph but not had it any higher as mostly on gravel. My preload is very high - not much adjustment left. I would guess it is tyres as knobs on tar are really bouncing from knob to knob rather that having constant traction. With knobs on it is more a case of point and hope rather than steering for me anyway! I find full knobs on the DR quite un-nerving in low- med speed corners and find it best to lean the bike in over the first set of knobs before leaning your body into the turn.
Perhaps higher pressures will help? I dont know what you are meant to run but for memory I am 24 and 26psi. The adventure boys would have a better idea of correct pressures for knobs on the road.

[Monstaman]

What tyres are you running and what pressures are you using?

What do you mean by "firmer" - damping or preload?

Set both front and rear to 30PSI just to road test, the rear is Trak Master M760, the front is BFG Crossengo.

Firmer, slightly less static sag than the front, I also firmed up the damping a bit as well, not far off the firmest, rebound is still very fast, faster than I thought it would be nearly all the way in.

I would guess it is tyres as knobs on tar are really bouncing from knob to knob rather that having constant traction.

I wondered about this too, I will drop the static sag in the rear to suit the front and start with that.

I went out fo a quick skid to Motutapu and yeap around the twisties I was sliding all over the place.

[Bass]

Set both front and rear to 30PSI just to road test, the rear is Trak Master M760, the front is BFG Crossengo.

Firmer, slightly less static sag than the front, I also firmed up the damping a bit as well, not far off the firmest, rebound is still very fast, faster than I thought it would be nearly all the way in.

OK.......
The only time that I have encountered the dreaded weave was when I put some really agressive knobs on. I suspect that Gaz is right about the tyres being the cause, but that the problem is the knobs flexing. I played around a lot with pressures and found that lower pressures seemed to help. No, I can't explain that, cos it makes no sense to me either, but the front was definitely more stable when I got the pressure down to about 18 psi, which is as far as I was game to go on rough stuff with no rimlocks. Have been down to 15 in soft sand.
The back doesn't seem to matter much and I don't notice a lot of difference from 20 to 38 psi, unless it's soft or slippery when the usual low pressures are the way to go.
I'm sorry, but I don't recognise either of the tyre brands that you have mentioned and so can't comment further.
As far as suspension settings go, my riding mate in Oz also lowered the back of his DR, as you have done and dropped the forks through the clamps an appropriate amount.
He hated the result. He said the handling was of real concern and pushed the forks back to full height. His concern was the tracking too.
I can't explain that either. I would have thought that lowering both ends the same amount would be the correct thing to do, but it's not.
The only thing I can suggest is that lowering the back alters the geometry so that it needs more rake and trail and so wants the forks at full length.
If you went out in the gravel with 30 in the front, I would expect her to slide around a bit.

[NordieBoy]

Technically dropping the rear with the boltand dropping the front 4cm is the same as doing it properly.

UNLESS you bottom out the suspension whereupon you will get launched over the bars as either wheel hits the guard and stops suddenly.

If you drop the back 4cm then to keep the exact same rake/trail you'd need to drop the front slightly more than 4cm through the clamps.

It should handle fine.

But....

[Taz]

Every bike moves around on K760's.

[Squiggles]

What pressures are you running? I've been at 28/32 with the trailwings on the road... interested to hear what others are at

[johannvr]

Every bike moves around on K760's.

I tend to concur. Those Kenda's look fairly "rough" for tarseal, even tho they are DOT approved.

I used to have as stable a ride as the DR could do on Pirelli MT21's - now less so on Michelin T-63's which have a similar-ish pattern & I have also noticed a slight weave on the front from a little above the legal limit, that was not there before.

Not sure exactly why either ... in the past with roadbikes we used to have a common belief that a weave in the front actually caused by something from the back wheel (ie not tracking true to frame, etc etc) - not sure if it was anything more than urban legend & if it applies equally to ADV bike or not ...

[Woodman]

not a Dr but a klr, but I think your problem is tyre combination. when I had
e09 front and rear she tracked true as, but when I replaced the rear only with a t63 the front now weaves and wobbles on the road.
My advice is to ride through it.

[junkmanjoe]

hey any other DR riders out there notice that the factory speedo runs at 10km slower than what its reading...

[johannvr]

Mine runs true according to GPS, at least to my memory. Can vouch that the odo is spot-on, but will have to confirm the speedo again just to be absolutely sure.