Tyres Again

I wasn't going to bother with this, but since I did the research, I might as well.

Prelude. My last bike was a 09 GSXR 750. I ran BT016s and Power Ones on that bike and really never had an handling problems with the bike. Steering was quite neutral and the front was always hooked up. If I tried hard, I could spin up the rear, but it was always intended and predictable.

Then I test rode a SD. For those So Cal denizens, I took my test ride on Decker Canyon from Westlake to to the top of the hill and back. For those who are unfamiliar with this road, you couldn't have a better test platform for the SD, IMO. Tight turns, fast chicanes, banked turns - its a Sumo paradise. I was sold. The SD was far easier to ride up up that road than the GSXR. I could basically put it anywhere in the lane that I wanted and it transitioned from side to side with amazing agility - just like a SD should. And I never had any question about what the front tyre was doing.

Within a year, I bought my SD. At first, it handled like a pig. It wouldn't turn. It ran wide. It wanted to stand up in the middle of a turn. The suspension was all fooked up. I got the suspension tuned and all was good again.

Then I replaced the stock Corsa IIIs with aftermarket Corsa IIIs and lost that lovin' feeling - especially in the cold. I switched to M5s and things got worse. On any given day, I could not feel the front. The only time I had any feel was on really warm days. Otherwise, it was numb.

I switched to Q2s and they are better. But, I still don't have the confidence and control I had with the original Q2s. (Oh, and when I changed to the M5s, I switched to Forged rims, so they are 2-3lbs lighter.

So, here's what I've been researching - tyre diameters:

Corsa III F: 601mm R: 639mm
M5 F: 600mm R: 630mm
Racetec F: 600mm R: 641mm
Q2 F: 604mm R: 634mm
BT016 F: 601mm R: 629mm
Power One F: 611mm R: 630-644mm (this was the only tyre to give min and max diameters)
Power 2CT F: 602mm R: 627mm
Pwr Pure F: 600mm R: 630mm

So, I ass u me, that KTM tuned the SD suspension for the Corsa IIIs. Now, I have no idea whether the OEM Corsa IIIs correspond to the data I found, but for sake of argument, lets assume that they do. Will dropping the rear 4.5mm (Corsa III versus M5) dramatically affect the front end feel? If so, would dropping the front a couple of

I've noticed that a lot of Brits swear by the Ractecs for track days and its interesting to note that the Racetec rear is closest in diameter to the Corsa III than all the others. The rear Q2 is closest in diameter to the Corsa III and it has given me the best performance besides the Corsa III.

Am I on to something here, or just FOS?

I'm runnin Q2's and not complaining at all. Warm up fairly well i thought within a few minutes it seems ( maybe 5 minutes ).
I don't track my bike but i ride as hard as i can in the twisties we have in the bay area and have NO chicken on the Q2's rear.

I'm not really tall at 5'8" so set sag at just about lowest settings but not quite. (Rider Sag) , and don't ask me i didn't write it down.

no matter what i did i couldn't get the front end of my bike to do what i wanted until i pushed the tubes into the triples deeper.
seems stock set up from factory is about 1/4" sticking out of top of triple - i set my down into triple about 1/4 inch and can't believe how much difference and confidence inspiring it's been.

i suppose you drop rear sag as low as you want and not do the same to the front but something tells me that's not the best way to go about getting handling.

i'd suggest pushing tubes down into triples if you haven't already. I'd do that after setting rider sag up first. You've got lighter rims on your bike ( wish i had those )
i hear they make a world of difference. So pushing tubes into triples for you shouldn't feel like you're slowing up the turn in - i sure don't feel like mines slow and i have stock rims.

other than that - that's about as far as what i know can help you with.

Regarding not turning in. Is the sag set properly on your bike? Mine was setup wrong when I got it and it handled like crap, once I sorted that out it turned in perfectly.
keep in mind that the rear spring is made for the average European and if you're ove 85 kg you do need a heavier spring.
Don't be scared about the bike getting twitchy, I believe all SD's are a bit twitchy when set up right (reason for damper on SDR) but it is never out of control unless you cramp on the bars.
Flat out over a crest mine waves a bit, I let it do its thing and it settles in no time without any input from me.

I run Diablo rosso corsa's and I find them hard to beat except maybe in very wet weather. I can't say this enough, this tyre rocks and it is completely different from a corsa III.
Unless someone comes up with something better, and can prove it, I will stick with these tyres.
I recommend anyone with an SD to try a set, thank me later!

Gotta remember though. The rear preload adjuster is not a ride height adjuster.

SC IIIs suck. But then, I assume you know this by now.

Never been a fan of BT-016s; either the OEM variants (as were on your 750), or the standard ones. Worst feedback/feel of any of the tyres you list IMO.

PowerPures and PowerOne "Commercial" (the street tyres) also suck. They suck on the street, and are a complete waste of money on track.

Pilot Power 2CTs, I keep coming back to. May try some Q2s next go-round.

I think all of you overlook an important factor regarding suspension effects from tyres: "squish" of the tyre (and when loaded with rider, temperature and pressure effects, rotation speed, slip, etc.). As these tyres are not constructed identically, they do not deform/deflect equally. Translation: Using circumferential data to determine trail (or other geometry and suspension effects) isn't necessarily going to give you what you think it will on paper. Then, just to inject more (and real) complexity to this, is how any given tyre behaves as a part of the suspension. Yes, that's right, a tyre has spring, compression, and rebound qualities; additional artifacts that affect things like "feedback" and "feel". And, if you're not totally bored with this yet, these qualities will change as a function of temperature, pressures (somewhat a function of temperature also), and tyre condition (age, wear, and how/where its worn).

Dude - did you try lowering some tyre pressure - especially up front? Couple PSI at a time ... Do you know how filled your forks are? Did you try removing any oil? Like maybe 10 mm worth?