Hello, when riding +100km/h mij front becomes unstable, like a shake in the steering. I think the suspension needs adjustement, but i don't know where to start. Softer or harder front or rear?
Riding tkc front and rear at 30 psi on road only
Thanks

i found that my tkc`s on my xtx became unstable anyhting from 75MPH
upwards

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Yamaha xt660x 2009 blue/gold mods= iridium plug, stage1+2, removed snorkel, blocked ais, akrapovric pipes, power commander pc3usb (pre made map), adjusted tps, dynojet 02 optimiser 30amp aux relay, smoked puig screen, oxford heated grips and brembo carbon ceramic pads, rfx 30mm bar raisers, puig long adjustable leavers, plus much more and a cheep �30 alarm which stopped it been stolen

TKCs can indeed affect the steering feel at speed, but I've found it more of a wobble/weave than a shake though (on a 21" wheel). In my experience, a bit of fiddling with tyre pressures can alleviate this, or rather I should say, move the point at which the wobble starts further up or down the speed range.

When you say shake, do you mean a high pitch rapid twitching or vibration felt through the bars? (Rather than a weave.) Is this oscillation violent or gentle? How worn/old are the tyres?

Could be a multitude of other things, such as: knackered or incorrectly adjusted head race bearings, poor damping (front or rear), unbalanced front/rear ride height, damaged rim, wheel(s) out of balance, loose spokes etc...

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it is like Pleiades says, it's more like a wobble/weave. In June I am going for a 3000km road trip with other tires, maybe bettered

I'd probably be inclined in that case to suspect the tyres.

Have a search on here and elsewhere on the web for "TKC80 high speed wobble", and you'll find it's not uncommon...

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