Bimota Forum

[Ekku]

I had the first trackday of the year yesterday and the first one with SB6 in years.

The suspension seems to work propely now when fixed, but the bike seems to be reluctant to turn in the curves and I can't get enough weight to front wheel.

I lowered the front end and it seemed to make thing a little better, but I think that the only way to make the bike handle like I want is to raise the backside of the bike too.

The adjustement of the rear end of shock absorber is already in the use and now i need to figure out the proper way for future improvements:

Should I have to buy the longer adjustement part to the rear Öhlins or to have different linkage made?

Opinions and tips much appreciated, Please

PS. easiest way is obiviously to buy R1 or similar, but that is like giving up...
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Older i get, faster I was

[Pompey]

Ok, I dont rebuild linkages just yet, it would be very odd if you had to go that far. I had the same experience when i started trackdays on mine. You can do a number of things to counter the back end but how you ride is very important...

The bike:

1. Is the rear shock fully extended to max ride height? ( Mine ended up that way to get it right)
2. Is it the original spring, if so, how heavy are you? It could be that 30 pounds spent on a heavier rated spring would.
3. How far down the forks have you dropped the yoke? I dropped 35 mm and went for heavier fork oil as a cheaper option then new springs and valves though worth the thought .
4. when you adjusted the sag you need to be on the bike in a crouched race position so did a friend help you?
5. What tyres and pressures did you use?

You:

1. When you approach a corner what actions do you go through?

a. stay in a straight line, brake hard shift down THEN release brake turn to apex and feather the throttle til past apex and accelerate as the bike lifts under power towards exit?

or

b. reach braking point late, drop gears, turn into apex with brakes STILL on releasing them as the bike settles into apex and then only accelerate hard once past apex again?

or

c. stay in a straight line, brake, then accelerate again to turn in point to the apex?

or

d. Do you use back brake?
or
e. Something else?
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Pomps
Bimota's Db2, Db5 ,Ducati's 851' 92, 888' 93, Honda blade' 93, Triumph speed triple' 07, kawasaki zxr 750 k1

[Ekku]

Thanks for the info.

1. The rear shock is fully extended.

2. I do not know if it is the original spring, but i suppose so. The suspension itself has been rebuilded in the last year and the front end internals has been modified. now it is actually respondind the adjustement. I am surely way much heavier than the regular italia test driver, so the different spring might be usefull.

3. I did drop the same 35 mm and then the bike turned much more easily, but I backed up to the 25mm after I scratched the right side fairing on the slow chicane.

4. Actually not done that as it should yet.

5. Tires are Pirelli Rosso II and the pressures were approx. 2.4 in the front and 2.25 in the rear.

In this time and this bike I did use cornering method a.

It is quite hard for me to find the proper riding position on this bike and maybe that is the reason why I felt the bike handled so bad.

The other bikes I use as regular tools for the track days, the Motoguzzi "classic racer" and my Bmw never gives me any surprises on the handling matter.
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Older i get, faster I was

[Pompey]

OK. Thats all good. So at 35 mm drop you felt confident enough to put enough down force through the front to compress the fairing into tarmac. Might be a clue to increase damping compression in the front but you may get chatter.

"a" and "b" are two different styles and not right and wrong. Most two stroke racers are used to B and it was also favoured and taught be Freddie Spencer and many USA riders. In your case with a weaker back spring it would feel better because you are carrying more corner speed, keeping the weight over the front and the exchange to drive after the apex means the bikes rear compression is less of a problem as the front end is coming up and wide any way.

If you prefer method A ( which most track dayers do ) then I would look into a heavier weight spring rather then over damping a weak one. Did the guys who over hauled the shocks do it before you bought it or were they aware of your size and weight?

A heavier spring would help to reduce compression rates without strangling it to much. If that still is not enough then I would consider increasing the swing arm length rather then alter the pivot point. It would tip the bike further forward and down at the front and give a greater leverage for the stock shock. It would also increase stability . I know a shorter wheel base helps to corner but not if the back end sits in under acceleration from the turn in point using method A.

Another slight change you can make is use the back brake just before the front to bed the bike into the corner and trail the rear off through to the apex. Doohan used this method and adapted a thumb brake once he knackered his right foot. I also considered a thumb brake just because its easier to feel it and use it at speed.

So, I would go back to 35mm drop. Get a heavier weight rear spring and re set your preload and sag with a friend measuring, you should be in the saddle in race tuck in your full leathers and helmet to get accurate weight. Set the front rebound damping so when you push down and release it springs back up once and back down without another bounce back up at all.

Set the rear rebound the same.

Finally, when you get set for the braking point set your body position early and only hang off half a bum cheek. Take the brake force through your inner thigh on the tank rather then through your arms which should stay bent and relaxed. It will help keep the bike settled for the initial turn in. Counter steer far more aggressively then normal under gas ( for Option A ). If that doesn't work, stick to road riding and get a super sport 600 for the track!

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Pomps
Bimota's Db2, Db5 ,Ducati's 851' 92, 888' 93, Honda blade' 93, Triumph speed triple' 07, kawasaki zxr 750 k1

[Pompey]

PS, you understand the expression " Counter steer" ?
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Pomps
Bimota's Db2, Db5 ,Ducati's 851' 92, 888' 93, Honda blade' 93, Triumph speed triple' 07, kawasaki zxr 750 k1

[vort28]

[Ekku]

[Pompey]

No worries. Its always a compromise ... even when you get it set perfectly what happens? You go quicker, so the geometry changes because of greater down forces, greater centrifugal effects etc etc.. and it starts all over again. Now where's that screwdriver
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Pomps
Bimota's Db2, Db5 ,Ducati's 851' 92, 888' 93, Honda blade' 93, Triumph speed triple' 07, kawasaki zxr 750 k1