Light front end / head wobble at speed

[cjdad76]

I have an '08 F800GS with 4000 miles on her which I have owned for 3 months now and recently had new tyres on her and asked for the head bearings to be checked. Tyres I went for are TKC80 front and Heidenau K60 Scout Rear (selected from good past experience with both on my KTM690 Enduro) and the reason for asking for the head bearings to be checked was not because of any issues, but because many people on here have complained about them being made out of toffee, so wanted them checked before a trip I have planned in a few weeks.

That's the background, now to the problem. Bike went in on road tyres feeling solid at all speeds, came out with the new tyres on and with head bearings checked with an awfully light front end at any speeds over 70mph. I'm talking dangerously light with a feeling of the front end floating and the bars wobbling - exagerated by higher speeds or turbulance from other traffic. At 80mph it felt like I could end up in a tank slapper at any time.

Nothing else on the bike has changed and I have good experience with the TKC80 21" fronts on other bikes and have never had anything like this.
- Tyres are balanced and alignment checked.
- Tyre pressures checked
- Tyres checked and no obvious deformaties, spun true when free standing
- Rear preload checked and as before
- Head bearings torque checked and ok

By process of elimination, I can only assume that it is the tyres causing it. This issue coupled with low speed vibes from the TKC on the front has dented my confidence somewhat, so I am going to replace both with Metzeler Tourances this weekend and see whether this gets rid of the problem. Guess I won't be offorading on this bike as much as planned. Hard packed stuff only!

Any thoughts / shared experiences would be appreciated.

 

[swissrob]

Friend with same bike and same tyre combo (scouts are crap offroad BTW) has the same issue its the tyres.

 

[cjdad76]

Changed the tyres to Tourances and the issue has disappeared. Very frustrating...........
Whether this was a poorly moulded tyre or whether it is just accepted that with these tyres on, some high speed wobble is likely to happen, I don't know. I used TKC's for years on my KTM's and never had an issue like this before. It's disappointing to think that this will dictate my tyre choice on this bike from now on - and potentially limit my riding to certain conditions using the less off road biased tourances.

Guess if I'm going to do any serious off roading again, I have to put up with high speed wobble or change back to KTM!

 

[sijohnston]

I had it up until 2 weeks ago. It doesn't matter if your head bearings are torqued to 10 if the bearings are shot. I replaced both of mine and it sorted the issue out. It's not an easy job though. But, it cost me £60 as opposed to the £300+ a dealer would charge. If it's in warranty, get it done on that.

 

[Bury_Dave]

I've had TKC80's on my F800 both last summer and now and I have no such problems. (Bike approaching 13,000 miles now).

On Saturday i was trying my best to keep up with a much more experienced mate on his Aprillia 1000 nutter bike on some seriously twisty roads and was hitting well in excess of the sort of speeds you're on about on the straighter bits in an effort to play catch up and still no serious worries. Thank feck he kept slowing down for me !!

In fact i find more road weave if i'm caught behind an artic' at 55mph !

I normally use Tourances and have no problems with them up to 110 but don't do that osrt of speed often (nor on a public road officer )

However, if you do put the power down hard, you can tell you're on nobblies !

They also don't last long if you go hooning it about. Saturday will turn out to be a very expensive day