Tyres and handling, seeking an explanation!

[Bikebiz]

Ok very weird this. I'm just back from a 2 day 1300km trip on my FZ. Had a blast up through Thunderbolts and then the John Oxley for those of you in Oz, to Port Macquarie.

Here's the situation. I was previously running the stock tyres, the slippery BT020s, with FZ1 bars and lowered the front 1cm (by raising the forks) which sped up the steering. I felt that it turned in very well and was happy.

For this trip I decided not to risk it on the slippery impossible-to-warm-up 020s, and got some Pilot Pures. The improvement in traction was great, but to my surprise it didn't steer nearly as quickly. Ah well I thought, maybe they just need to be scrubbed in a little more.

400km into the trip and I was tearing my hair out. The bike was understeering like you wouldn't believe. I simply couldn't pull the bike into turns. It required so much effort. Then if I did manage a turn at half a decent pace, if I hit a bump it would just push it back out. What a joke. To add salt to the wound, I was getting tank slappers every other corner. Pulling myself back onto the seat from knee-out corners, the front end wouldn't have it and wagged about. Urgh I couldn't win.

It was so bad that I thought to myself that all I could do for the moment it bump the forks back down to the stock position so at least I could control the slappers a bit more.

I set out on the next set of twisties, and believe it or not the thing was steering as it did with the other tyres, ie really well. It turned without effort and held its line exceptionally well.

So I'm scratching my head here. Raising the front end, I thought, should have made the steering slower. So what's going on? Both tyres are a 120/70 17, so the profiles are the same (although the profile shape is obviously different).

I'd be interested to hear what others think of this.

PS the bumpy Buckett's Way road nearly killed me. What was tolerable suspension commuting, turned out to be a nightmare on the bumpy roads. I'm scared I'm going to need suspension work AND a damper to bring her up to speed - more $$!!

 

[tomari]

i think that not all tyres have the same response to suspension changes, 10mm raising might be a little for this tyre but too much for an other, i suggest you move slowly +2mm the time to find what suits your new tyres. personally im at +7mm right now on pirelli corsa 3 tyres having HUGE difference from stock settings. on bt020 i was +10 too. also check and recheck air pressure on new tyres as i found out they stretch somehow (or loose air) the first days
what is the production date of the tyre? theres a DOT something on them check it out

 

[Bikebiz]

Makes sense everything you said here. Interesting hey.

Tyres are a new model so can't imagine them being on the shelf for a while (but will check the manufacture date in any case). Running 35/38psi, anyone running anything significantly different on these?

 

[Wolfman]

I went as far as 20mm higher on my bike, when i was trying to compensate for not being able to get the right ride height at the rear, with my first ohlins shock, without ride height adjustment...

Also had massive issues with the bike, at first wanting to tip in too quickly on corner entry, but then, as soon as i got on the power, it wanted to push straight on! Result...zero confidence in the bike, and a real hesitance to push hard!!! Try and explain how it was under and oversteering in the one corner...too high at the front, rear end bogging down due to sitting too low???

I Put the forks back to stock, and got the shock with rear ride height adjustment, set the bike up properly, now she goes just where i point here!

I also find The Bridgestone BT003's turn a lot better than the super sticky, and very stable Michelin Pilot Power 2ct's, or Road 2ct's...

:thumbup:

 

[GConn]

Re-check your tire pressures. About the forks, I suppose that raising the front (i.e. to stock) decreases the rake if I am not mistaken. Less rake means higher sensitivity, lower stability/confidence in turns. I hope I didn't confuse everything in my mind and sharing wrong info

 

[Bikebiz]

Re-check your tire pressures. About the forks, I suppose that raising the front (i.e. to stock) decreases the rake if I am not mistaken. Less rake means higher sensitivity, lower stability/confidence in turns. I hope I didn't confuse everything in my mind and sharing wrong info

I'm pretty sure raising the front does the opposite to this, ie increases rake to give (what I thought) less sensitivity, better stability. I achieved more stability AND sensitivity. I really can't explain this one.

 

[deeptekkie]

I personally believe that there is no hard, fast, catch-all rule.
I also believe that getting a bike dialed-in, (when done right), takes a long time to accomplish and if you're learning, you WILL encounter some surprises.
Tires are everything when all else is said and done. There's the "sticky" factor, (which usually changes with heat), tire pressure, tread, size, gyro effect, flex, etc, etc, etc.
On the other side of the coin: I've had bikes that would stick like glue wearing nearly almost anything and I owned one bike that handled like a pig - no matter what you did to it.
I believe our chosen model, The Fazer, is extremely sensitive to "the love" that we put into our tires.
When you get your pressure and suspension dialed-in, I am still amazed at the stock version's handling, (even with a "fixed" front frork). -JMO
P.S. Really glad you survived the tank slappers man. (I HATE tank slappers!)

 

[RJ2112]

Bikebiz,

If you want to sort out what the profile of a particular tire does to the steering of the bike, you have to be able to isolate that effect to be able to gauge it.

If you have OEM springs in the fork and rear shock, all bets are off on what to expect with altering the forks in the triple clamps. Rake and trail numbers depend on chassis attitude. If you are heavy, and sit far back on the seat, the nose MIGHT be higher than designed. If you sit forward, the front will compress, and that will 'speed' the steering. The fork angle will become more vertical with respect to the ground.

The dual rate fork springs allow far too much compression on braking, in my view.

 

[Bikebiz]

I still like the Pures, they haven't skipped a beat in 1500km, and warm up very quickly. I'm only concerned about having to adjust the settings after installing them. So I'd still recommend them.

 

[OneTrack]

What I have discovered is that the "better" I become with my cornering skills, the more I discover the limitations of my wonderful FZ6. In hard, fast corners, my FZ6 will upset quite easily if I encounter an unexpected bump or hole in the road. It's not uncontrollable, but it does "spoil" the line that I'm taking. I haven't performed any suspension mods on my bike and am still running on the original Dunlop 252's at 7500 kilometers.
What is obvious is that the stock front suspension is too soft both ways, and will induce some serious wobble when upset on a corner. I find that 33psi front and 37psi rear in the tires is about as good as it gets...any higher pressure than that makes the suspension work even harder, with increased head bobbing by the front even worse.
This may sound obvious, but the gear that I'm in makes a HUGE difference to how my bike handles the bends. Low gear/high RPM makes it very, very twitchy. Higher gear/lower RPM's results in a much smoother journey through the corners.....and in reality, probably gets me around the bend just as quickly as the former....My Scorpion's just don't sound as nice, though.

 

[ozzieboy]

My two bits...Whack 'er back to stock and adjust in small tweaks (if you really need to). I just ran it stock on the FZ6 'cause it turned in just fine for me on any tires, and it was truly superb for direction changes in the zig-zaggy bits.

I did used to get a lot of head shaking on the 6 though, and it was always worse on bumpy roads. Had barely any at Mallala. The FZ1 aint so bad for it, 'cause the front is usually off the ground....The rear slipping and sliding is the problem now...lol. Chasing the Z thou, that Blue FZ6 I had would shake its head like a dog with a shoe...lol:rockon:. Just sort of ignored it, and even got to enjoy it a bit:spank::spank:

 

[OneTrack]

One can certainly explore the limits of a stock FZ6 chasing one of these....:rockon:

 

[RJ2112]

What I have discovered is that the "better" I become with my cornering skills, the more I discover the limitations of my wonderful FZ6. In hard, fast corners, my FZ6 will upset quite easily if I encounter an unexpected bump or hole in the road. It's not uncontrollable, but it does "spoil" the line that I'm taking. I haven't performed any suspension mods on my bike and am still running on the original Dunlop 252's at 7500 kilometers.
What is obvious is that the stock front suspension is too soft both ways, and will induce some serious wobble when upset on a corner. I find that 33psi front and 37psi rear in the tires is about as good as it gets...any higher pressure than that makes the suspension work even harder, with increased head bobbing by the front even worse.
This may sound obvious, but the gear that I'm in makes a HUGE difference to how my bike handles the bends. Low gear/high RPM makes it very, very twitchy. Higher gear/lower RPM's results in a much smoother journey through the corners.....and in reality, probably gets me around the bend just as quickly as the former....My Scorpion's just don't sound as nice, though.

The difference between high RPM/low gearing and lower RPM/higher gear is the amount of leverage the engine is exerting on the chassis.....

When you are in a longer gear, your throttle inputs are 'softer' to the driven wheel... it won't jack up or squat on the suspension as much. If you keep the chassis stable, the rake and trail are much more consistent, and the lines you make through the corners don't need as much correction.

The 'drive' out of the corner is not as hard, but you can have your cake and eat it too, if you can learn to be extremely smooth with your throttle inputs.

Chopping off the throttle, or stabbing the brakes, or whacking the steering around all upset the suspension. Smooth is key. Especially with the excessivley soft springs, and lackluster damping of the OEM FZ6.

 

[OneTrack]

Smooth is key. Especially with the excessivley soft springs, and lackluster damping of the OEM FZ6.

Precisely......as one magazine tester said of our bikes: "The FZ6 rewards the smooth rider" :thumbup:

Notwithstanding the realities of our FZ6's stock suspension and the physics of the cornering dynamics, when I'm diving into a corner in 2nd gear, engine starting to howl at 12000 rpm's, Scorpions wailing, I'm Mike Hailwood on his Honda 6 at the Isle of Man TT.

(An FZ6 probably handles better than Hailwood's Honda ever did, come to think of it)

My next serious mod is to upgrade the front fork springs.

 

[joe1971]

What I have discovered is that the "better" I become with my cornering skills, the more I discover the limitations of my wonderful FZ6. In hard, fast corners, my FZ6 will upset quite easily if I encounter an unexpected bump or hole in the road. It's not uncontrollable, but it does "spoil" the line that I'm taking. I haven't performed any suspension mods on my bike and am still running on the original Dunlop 252's at 7500 kilometers.
What is obvious is that the stock front suspension is too soft both ways, and will induce some serious wobble when upset on a corner. I find that 33psi front and 37psi rear in the tires is about as good as it gets...any higher pressure than that makes the suspension work even harder, with increased head bobbing by the front even worse.
This may sound obvious, but the gear that I'm in makes a HUGE difference to how my bike handles the bends. Low gear/high RPM makes it very, very twitchy. Higher gear/lower RPM's results in a much smoother journey through the corners.....and in reality, probably gets me around the bend just as quickly as the former....My Scorpion's just don't sound as nice, though.

Those crapastic tires have a lot to do with it. Mine used to do all sorts of weird stuff till I took the 252's off and put conti road attacks on, now its a completely different animal.

 

[OneTrack]

Those crapastic tires have a lot to do with it. Mine used to do all sorts of weird stuff till I took the 252's off and put conti road attacks on, now its a completely different animal.

Despite my Dunlop tires' limitations, I just can't bring myself to replace them before they are either worn out or too old.

 

[RJ2112]

Despite my Dunlop tires' limitations, I just can't bring myself to replace them before they are either worn out or too old.

There's got to be some Scot in you somewhere, LOL.

 

[OneTrack]

Welsh. The Scots spend money like drunken sailors compared to the Welsh.

 

[wolfe1down]

Those crapastic tires have a lot to do with it. Mine used to do all sorts of weird stuff till I took the 252's off...

x2

I replaced my Dunlop tires at 7300kms due to some weather cracks from storage (I'm in the military :canada: and deploy a lot more than I ride). I replaced them with Michelin Pilot Road 2 sport touring tires, and the difference is like black and white : color TV. Awesome handling, wet and dry grip, and road 'feel'.

Just my $0.02 worth.