Tmax handling; lightbulb moment needed...

[Greyerbeard]

My Mk4 has recently started to feel 'squirelly' on bumpy corners; wriggling around as though the front wheel is only vaguely connected to the road.
Tyres are fairly new Michelin PR4SCs, at the correct pressures with an accurate gauge. Front has done about 3k miles, rear about 2k, both look barely worn.
No detectable play in wheel, swingarm or steering head bearings.
All wheel spindle nuts and fork leg clamp nuts are tight.

Only clues I can come up with are
a) I lost about 15kg since last winter, down to 70kg now (11 stone); the bike feels fine with a pillion. But the handling has only gone off recently.
b) There's VERY slight cupping on the right side of the front tyre, just like there was with the OE Bridgestones.
c) A couple of hundred of my most recent miles have been on motorways.

Any bright ideas would be welcome, apart from starting to eat saturated fat again!

[smeghead]

Eat lard

[MrGrumpy]

You may recall that I had something along the same lines with my Tmax mk4, which was diagnosed as the Bridgestone SC Eco tyres wearing in a strange fashion - effectively the opposite of squaring off, if that's the same thing you describe as 'cupping'.
The Symptoms I had were an increasingly harsh ride and severely decreasing confidence and feel in the corners, especially from the front - twisty roads went from being fun to nervewracking even if going 25% slower then previously.
It all sounds somewhat like your issues...in my case swopping the Bridgestones for Michelins cured the problem. I had no problem with the Power Pures until they were worn out, neither with the PR4s until I sold the scoot. The fact that you are having similar issues with PR4s as I did with B.stones is intriguing. Perhaps there is some odd facet of the mk4's suspension that causes weird patterns of wear in the tyres in some circumstances?
I guess the upside is that if this is the issue, then there is no underlying problem to fix, just throw away a completely functional pair of expensive tyres and fit a new pair....

[2wheelover51]

How odd. I can understand squaring off but surely only underinflation should cause it's opposite. How very strange.
My Dunlop GPR100's were down as an advisory this morning when "Mr T" flew through his MOT, but they'll be replaced with more of the same, since I've never had a bad moment, wet or dry with them despite some very spirited riding, and the rear is now slightly squared off but still no handling issues at all. They're great tyres but seem largely ignored in favour of Pirellis, Michellins etc.

[Ferret]

I have had exactly the same feeling ( lack of ) with various brands of tyres on bikes and scoots . I have had to put it down to my riding style and the way it wears the tyres profile . I remember the worst tyre for doing it for me was the Dunlop roadsmarts of about 9 years ago ,they turned off like a light switch ,replaced tyres with the same and fine again was the same on two differant styles of bike .I believe it's the fact I tend to opposite steer a lot ,that said those new pirellis I have just tip in without the need for the same amount of input previously used .

[Ferret]

I nearly forgot with all this heat the fork oil especially if over a year old is probably got the viscosity of p water and therefore effecting your damping which could well be contributing to the lack of feel .

[Greyerbeard]

Thanks for the input folks.

Sorry, but more lard is not an option!

With this odd front tyre wear, you have to wonder if the recommended pressure is perhaps too low..?
Or maybe it's just these new dual compound, 'hard in the middle, soft on the outside', tyres? Can't afford to throw away perfectly good tyres, I'm afraid...may try the Dunlops next time.

Its always struck me as odd that fork oil is nowhere listed in the service schedule - although there are full instructions in the workshop manual.

[MrGrumpy]

With this odd front tyre wear, you have to wonder if the recommended pressure is perhaps too low..?
Or maybe it's just these new dual compound, 'hard in the middle, soft on the outside', tyres? Can't afford to throw away perfectly good tyres, I'm afraid...may try the Dunlops next time.

Don't think its dual compound tyres - I had my issues on the single compound Bridgestones but had no problems with the dual compound Michelins - but you have had the problem with the Michelins. which suggests the issue is elsewhere.
Higher tyre pressures on the B.stones would have made the ride even worse!

[Greyerbeard]

Hmmmm....made a noticeable improvement today by.....
moving the seat backrest forward a notch!
Reasoning was that less flab around my backside meant that I was sitting further back on the seat; hence less weight over the front wheel; backrest further forward means weight further forward.
Or maybe it's all in my mind...?

[MrGrumpy]

Or maybe it's all in my mind...?

Not necessarily! I moved the backrest back once on a previous Tmax and whilst it felt much more roomy, I felt that I'd completely lost touch with the front end! Of course the difference is only a cm or so, so the actual weight difference can't be big, but everything is about feel, and its amazing how tiny differences can feel so different. A problem cheaply solved?

btw - I don't think the backrest is moveable on the new TMax! Or at least there's nothing in the manual, though there was no mention of it in the mk4 manual either - though the mk6 seat / backrest is a completely different design.