My 2012 XT660R has suddenly developed a wobble tendency at highway speeds (100-120 km/h actual), and I am somewhat puzzled. I bought the bike new, it now has 8500km (5300-ish miles) on it, never been jumped, wheelied or crashed. The tyres are still the stock ones (Metzeler Tourance), with the rear clearly squared off due to highway commute, but the front looks fairly smooth. There is still at least 3 mm tread left on both tyres.
The front end feels OK in other respects, no imbalance, bearing noise, dragging or pulsing brakes etc. However, the suspension is defintely softer now than when it was new, and I suspect the front has sagged a bit.

Is it possible that the rear tyre is the culprit? It has been getting gradually more squared off, but the wobble has appeared more recently.

All advice is welcome, as I have not encountered such a problem before on my other bikes.

It could well be the squared off rear. The condition/shape of the rear tyre can do funny things to the front end. Probably worth replacing anyway - see if it makes a difference.

Double check your headrace bearings aren't loose, tight or notchy. This is quite a common cause for wobbliness at speed.

Once you've ruled out the rear tyre and headraces, then have a look at fiddling with tyre pressures and also check the suspension sag/ride height is correct.

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Thanks - much appreciated!

hi
did you resolve the issue?

Hi my tenere with the standard tourances started to wobble at speed at exactly the same mileage, one of the reasons i changed to TKC80s. However they wobbled more at speed 75 ish mph indicated! have now changed the rear to Heidenau k60 scout 130/80 and retained the KTC80 front and its now fine no wobbles.

this is very strange. I have and XTR and on the original Tourance, nowobble at all although once past 85, cross winds would unsettle the handle bar otherwise rock steady into triple digits (not on public highway of course).
this was right through the wear for over 8000 miles.
Once past 6000 miles, the rear started tracking the groves on the road which at high motorway speeds sometimes caused a little tank slapper (nothing worrying once you got used to it)
I changed mine before the legal limit because the chunky rear handling became strange when leaning the bike and also I got fed up locking the rear when braking and changing down quickly.

It's the little tank slapper that I am talking about , passing Trucks at speed also set it off. In my case rear tyre wear was the root cause.

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XTz 660 tenere, adventure spec bash plate, main stand, skid marks tall screen, Oxford tail pack 36 litre. Kobra hand guards, Bigger cast footpegs, Zen overland luggage plate, USB power point, iridium spark plug, TKC80 f k60 R tyres, o2 and fuel Kev mods, DNA stage 2 filter. bark buster bar wieghts, Touratec side stand base and GPS mount. Led spot lights