"Turn in" and just plain annoying turning characteristics

Discussion in 'The Perfect Line and Other Riding Myths' started by Buster452, Apr 18, 2012.

  1. ibafran

    ibafran villagidiot

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    #3 It is hard to tell how much the bike is doing for itself compared to what the rider is making it do for himself. I note that in the wet, my corner lines get longer and I get very gentle with steering forces that I input to the contact patch.
    Seems correct to me except for #4.
    Once the lean has been stabilzed for the turn and for the constant throttle speed, the bike should not self-right without some rider input either more throttle, or steering, or both. Riders wishing to test this can take their bikes to a very large and safe parking lot. Ride the bike in a circle of choice lean and constant speed (using a throttle lock of some sort). Taking one's hands off the bars should show that the bike will maintain that line and neither fall in nor stand up. I don't think that "self righting" is apt terminology in this instance. The bike does not do much all by itself. Rider input for better and for worse is what makes the bike want to stand up on the exit line.
    Again, I defer to Tony Foal or his ilk.
    #21
  2. Bill_Z

    Bill_Z Dude! chill,...

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    You and I weigh about the same. However, I am 6'3" and I have lifted the rear of my Wee as high as I can with Soupy's adjustable links. That had the same affect of lowering the front by tipping the frame geometry and increasing the the turn-in for quicker steering. You may be able to lower the front end to achieve the same goal if you are shorter than I am, and be able to avoid the expense of the changing the links. I have noticed a quicker, more responsive steering, since I've made my changes and I like the results.

    I would agree with tpete on the above recommendation though; if you're looking for more sport bike handling, having your suspension tuned by someone that really knows what they're doing is much better than pokin' at it the way I have. Your results will prove better able to achieve your goals.

    Ride on!
    #22
  3. Buster452

    Buster452 Been here awhile

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    Ah, but this is the mythical "neutral steering" motorcycle. Everything I've read indicates that in only a limited speed range or even a set speed is this possible. All other speeds require some sort of input from the rider to maintain line.


    Can others perform tests? Get on your bikes, get setup in a long curve with steady speed maintained with throttle locked and stop touching the grips. Does your bike go back upright, stay in the lean/curve or does it start to lean in more?
    #23
  4. ibafran

    ibafran villagidiot

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    Good points. My 05' Sprint ST seems to stay set on line and at a stable lean angle with the throttle locked at speeds between 35-65mph. I ride 'hands-free' a lot and the bike turns ok. The 95 Trident that I had for 100k miles was easier to ride hands-free through corners although I can't say why.
    #24
  5. PT Rider

    PT Rider Been here awhile

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    Buster, a good point was made above about getting the shock modified by Jay at Sasquatch, or get an aftermarket shock. Even if you get the right spring for your loaded riding weight, you still have a mediocre damping Strom shock under you. Do raise the forks (lower the front) as described above.

    Preload is for raising or lowering the bike to get into about the middle of the suspension travel to give about equal chance of not topping out nor bottoming out.
    http://www.vstrom.info/Smf/index.php/topic,1539.0.html

    Part of the turn-in effect is caused by the top of the wheel flopping toward the inside due to gravity when the bike is leaned. With any bike stationary, lean it to one side and note how the front wheel flops inward.

    What tires are you running, and what inflation pressure? What wear pattern on them? Try different tire pressures, but no lower than the pressures on the sticker for the weight you're riding.

    Do you roll on the throttle as you exit the turn?...this does help straighten and stand the bike up, combined with steering to straighten it. Some prefer keep the outside arm relaxed all the way through the turn and push or pull with only the inside arm.

    Do you sit straight with the bike's axis as it leans in the turn, or lean your upper body down toward the pavement, or lean your body up and away from the pavement? This changes the shape of the tires' contact patch on the pavement and changes how the tires react.
    #25
  6. Buster452

    Buster452 Been here awhile

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    Most of the reason I started this discussion was to try to understand everything that's going on that affects how a bike turns.

    All during this thread I've been playing around with pre-load on on my forks. Started in the middle, where I had it.

    First thing to make note of. I have 1" RAISING links in rear. I've read the recommendations of raising the forks in the triple tree, but that'll be the last thing I'd do. I've already decreased trail/rake by lifting the rear a bit more. Then, a stronger spring and better damping will lift the rear even more. So, once all that is done I'd mess with moving the forks in the triple tree.

    I started reducing pre-load. In the morning I turned it up half and then rode to work. Turned up another half, rode home. After 1.5 turns, I didn't like it. The bike was a bit more unstable and was thrown around a bit more by traffic turbulence. It would get into slight wobbles that were easy to stop, but still uncomfortable. It had zero affect on how the bike acted mid-turn and how it came out of a turn. Setup of lean entering the turn was easier, but I still had to stop the lean and start the turn-in manually. Weird thing was lane changing wasn't as snappy as when I started.

    So, I went the other direction. Half turn more preload each way to/from work. I'm now maxed out on pre-load. Bike is more stable at speed, but it still needs pressure on the outside bar to keep it upright in the turn and still needs help turning the tire into the curve.

    I would have thought I would have seen a more dramatic change in turning with all of the changes in pre-load I did. The only noticeable affect was on straightline stability.

    Next up, I'm going to start lowering the back to see how it responds. It's at max pre-load front and rear, so I'll start lowering the back just to see what happens.

    There are so many factors here to play with. I'll go through the range of rear preload just to mess around. Once I've played with pre-load, I'll mess with tire pressures. Realistically though, once I'm done playing with setting I'll set the rear-preload back up until I can beef up the rear shock. I'm 280lbs and have a set of Jesse bags on sometimes, so I use up that rear spring quite a bit.

    Right now I'm running a Shinko 705 rear and tkc-80 front. I've had the same behaviour with my shinko front also. I don't remember much about the bike handling with stock tires. Once I wear out the rear, I might spoon on a Heidenau K60 just for kicks, but it's tough to beat the value of the Shinko on the rear.

    As far as pressures go, I do recall having some fun on some paved twisties between dirt sections when aired down. I always attributed that to getting used to a little sliding in dirt and having a ton of confidence on sticky pavement. I typically run 41/36 on pavement and 35/28 in the dirt.

    I realise I may never get the bike perfect. Much of this is just for learning and satisfying curiosity.
    #26
  7. rocker59

    rocker59 diplomatico di moto

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    I don't know anything about the particular tires you're running, but in my experience tires have a big influence on the phenomenon you're experiencing.

    Tire pressure. 41R/36F could be contributing. I'd consider dropping to 38R/34F and see if you can tell a difference. It makes a difference for me.

    Tire profile. Every tire has a slightly different profile and will cause different bikes to do different things. You have to learn what different tires do on your particular bike by trial and error.

    It's a subjective thing. I've tried tires that people raved about, only to find they sucked on my bike. The Dunlop RoadSmart being a recent example. They had weird turn-in and wanted to stand my bike up under braking.
    #27
  8. Buster452

    Buster452 Been here awhile

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    I can understand a tire's profile would have an affect on how easily the bike leans. A wider profile is like a wider base and thus more difficult to lean over.

    Turning the front end into the curve seems like it's more about where the front tire contacts the ground when leaned over.

    Whats the effect of a wider profile on the front?
    #28
  9. Alton

    Alton Been here awhile

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    When I bought my current Bandit the handling was bad at first, and I thought the tires had been in the OK sun too long and was prepping to order a new set for it. Then my brother pointed out that they looked low. I checked and found out that the bike came home from the dealership with 10 lbs in each tire..... :eek1
    #29
  10. wiseblood

    wiseblood Hall Monitor

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    Have you tried adding throttle to stand the bike up, rather than counter-steering out?
    #30
  11. David R

    David R I been called a Nut Job..

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    When I bought my versys it had 22 psi front and rear. I test drove it that way too.

    I thought turn in is how easy the bike lays down for a corner. My 250 super moto fell into the turns. My BMW 1100 has to be pulled into the corners.
    #31
  12. Buster452

    Buster452 Been here awhile

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    I've added throttle with little affect. Doesn't stand up in a curve. Some would consider that good.

    I'm surprised that drastic adjustments to preload have not yielded more drastic changes in handling. It's really interesting. I'm thinking about dropping the rear all the way for the ride home to see what that does.

    The only affect noticed so far has been straight line stability.
    #32
  13. High Country Herb

    High Country Herb Adventure Connoiseur

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    I'm leaning toward the tire explanation, because I recently had the opposite problem, which was accidentally solved by a new set of tires.

    My Dorsoduro used to steer too sharply in corners, forcing me to counter-steer all the way through the corner. It was a really wierd feeling I had never experienced before.

    I replaced the Dunlop Qualifiers with some Pirelli Scorpion Trails, and the problem vanished. The Qualifiers had a slightly sharper arch, while the Pirelli's are nearly perfectly round. Both were 180/55-17.
    #33
  14. ttpete

    ttpete Rectum Non Bustibus

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    At one time, Dunlop made triangular section race tires. They were downright scary. They'd just flop to full lean almost instantly, and you'd have to countersteer to get the bike back up out of the corner.
    #34
  15. Buster452

    Buster452 Been here awhile

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    Well, going to both ends of the the xtreme in rake/trail have little affect. I still need to push on the outside bar to get the front into the turn and once on my line I have to maintain that pressure to keep the bike from leaning more. I've had the front jacked all the way up with preload and the rear squated down with no preload. I've had the front down with little preload and the rear up with max preload.

    The only affect has been on the bikes willingness to lean left to right with input on the handlebars. This equates to more stability in a straight line and less of a willingness to lean.

    From my observations, rake/trail impact how quickly you can get the bike to lean only. Little do do with how the bike actually comes around the curve and starts turning itself.

    I'm resetting back to the preload settings I had before and I'm going to start messing with tire pressures.

    This is happening with either a front TKC or a front Shinko, so I'll start messing with the pressure in the back tire to see what happens.
    #35