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excessive tire spin at %50 throttle

4K views 22 replies 7 participants last post by  stumoores 
#1 ·
hi, I have lack of rear tire grip since I bought the '14 daytona 675r 2nd hand with 3.000 miles on it. it spins the rear when the engine hits to powerband with near wot at higher speeds or near %50 throttle at very low speeds. I was relating this to 2 y/o oem supercorsa sp tires. recently changed to michelin ss evo tires with big hopes but I have same spin if not more. squared off sp tires were not getting that much heat but grip wasn't any different. this is not road surface related, I power wheelie other bikes at exact same parts of the road.

I have trs linear link with one step softer (95) spring. front fork caps flush with triples... rider 180 lbs ready to ride. front spring was near ok when the bike at road trim with around 45mm front sag, 4-5 turn in with preload adjuster got me there. it is around 40mm now with all preload backed up. bike in race trim so around 20lbs lighter.

trs links raised the rear by 6mm. I tought this gave me too much swingarm angle, oem shock shim is 8mm, so I tried with 2.5mm, 5mm and 7.5mm to see differences. I rode exactly same place every time.

this is my first 600 class and I can say I never had that much spin on liter bikes. even with no grip I enjoy riding it so much so that everyday I try different settings, trying to improve it while enjoying those controlable spins :))) I can drift out the curves with control, can drift all the straights through all gears if I keep the steam. it brings out the holigan in me. but my main purpose is racing with it. so I must find that grip...


I have measured the swingarm angle with both methods. 1: suspensions extended and tires just touching to the ground, 2: bikes sits on its weight... it is almost 13 degrees when the bike sits on its own weight, near 14 degrees with the first method (which I know correct way to measure) I have used trigonometry as well as clinometer apps on smart phone, similar results.


I adjusted the rear sag between 35mm and 40mm with 3 different rear height (static sag 15mm-20mm). no luck. grip is always same. I rode different bikes at same place, most of them wheelie where my daytona just spins the rear. some of them gave me the feeling of rear tire is biting the ground and pushing the seat up, which I want to feel.

I also measured antisquat at stop with 3 height level until the tire spins. highest sa angle gave the most antisquat.


when I lovered the rear and softened for more sag, I got front wobble, it want to tankslap from smallest bumps at very slight turns with maintenance throttle. raising the rear reducing this issue but not make it go away.


when I look at these symptoms reasons should be; stiff spring, not enough weight transfer to rear or not enough antisquat seems have to be reason, but I don't understand why I have these issues.


Who goes to track or racing, what are your set up? how did you resolve if you had similar problems?



please help !


thanks for reading :)
 
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#3 ·
This bike has power but not that much power..... you have to have something on your tires causing the slip or something or some seriously modified sprocket setup to cause it to just constantly keep slipping at 50% throttle. I open mine up all the time and I have to try to break traction on purpose.
 
#5 ·
I tried between 28-34 psi cold at rear. didn't make any difference. this michelins supersport evo tires has too much flex in them so more contact surface to the road compare to oem sp. it is %50 road %50 track tire.

it can be harder on the mid section for more mileage but still I don't remember that much slip with higher performance machines.

sprockets are oem and chain is a little more slack than required. I found chain is rubbing the guide on the swingarm I think when the shock extends so I am around max limit of swingarm angle.
 
#21 ·
thanks for sharing. grip was much better today with 35mm sag and 7.5mm spacer with trs link. but weather has got much warmer since I tested with same set up.


anyone using offset swingarm pivots? if so is it to reduce or increase swingarm angle?
 
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