06 YZ450 Front Wheel Push


25 replies to this topic
  • ben_suhard

Posted September 24, 2006 - 01:10 AM

#21

Motorcycle steering geometry is always a balancing act, and Yamaha has, IMO, done the best thing they could have possibly done to improve the situation. They moved as much weight as they could as close to the center of gravity as they could, and that makes the bike easier to pitch, roll, and, importantly, turn. That, in turn reduces the loads placed on the front tire as it tries to change the direction of the bike, and makes it less likely to slip.:thumbsup:

Umm, Gray, I'm not looking for a fight here, but how could they move as much weight as they could to the centre of gravity? The centre of gravity could be anywhere on the bike, not necessarily the centre of the bike, it could be high or low, forward or rearward. They actually put the engine as far forward and as low as they can. Handling is also affected by the internal movements of the engine. Also, the more load you put on the front tyre, the better it will grip and turn. 4strokes(because of the engine breaking) put more load on the front than 2strokes(not including use of the front brake), which increases front tyre grip and also steepens the head angle for sharper turning.

  • Satch0922

Posted September 24, 2006 - 03:40 AM

#22

between tire choice, raising or lowering the forks, setting the correct sag and most importantly ......SETTING UP YOUR SUSPENSION PROPERLY you can make this bike do whatever you want.

  • Ga426owner

Posted September 24, 2006 - 05:53 AM

#23

between tire choice, raising or lowering the forks, setting the correct sag and most importantly ......SETTING UP YOUR SUSPENSION PROPERLY you can make this bike do whatever you want.


Totally agree it looks like a lot of folks here do not have their bikes set up correctly. I just finished fork and shock revalve/resprung and up to 105mm sag testing and my bike absolutely is the best cornering bike I have ever had...absolutely no front end push.....and this is with stock offset, MS3's and forktubes raised. So yes the push can be alleviated :thumbsup:

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  • cowboyona426

Posted September 27, 2006 - 07:37 PM

#24

gray- I really value your input, and the fact that you remembered that I had lived in ID and have now relocated also amazed me somewhat... anyway back to the subject matter. My 06 has a Maxxis MaxxCross SI front tire, and no other changes made (yet). I have some clicker settings that I am going to try (can't remember them currently) and have plans to send my forks/shock out to a fellow TT'er to get them worked over some. I have played with the idea of a different set of clamps, but can't really justify the cost if they won't get me the results I would like. I wasn't supremely thrilled with my tire choice for helping the problem, but I'm hoping that with some clicker changes and lowering the tubes hopefully I can get the results I'm hoping for. I don't know why, but for some reason I have this notion in my brain that raising the fork tubes is a "band-aid" fix and I'm hesitant to try that until I've tried to correct the problem other ways. Also, in the places I usually ride most of the dirt is hard packed and rocky, with the occasional muddy or sandy spot but 95% hard pack/rocks/roots.

  • grayracer513

Posted September 27, 2006 - 09:05 PM

#25

how could they move as much weight as they could to the centre of gravity? The centre of gravity could be anywhere on the bike, not necessarily the centre of the bike,

That's true. But wherever the CG is, those components that can be moved should be moved as close to that as possible. An example of how they did that is the relocation of the oil supply from the steering head to the crankcase. It's probably not at the CG, but it's certainly closer.

They actually put the engine as far forward and as low as they can.

That is actually not true. They did lower it, and they did lower the internal mass within the engine, but in fact, one of the changes made to the engine does the exact opposite of what you suggest, that being the change in the cylinder angle to be more vertical. That places more weight rearward. The effect of centralizing mass is easy to understand. Assume you are carrying a 12 foot 2x4 on your shoulder, and you have to turn 90 degrees quickly and stop turning without over-swinging. Not easy. Now visualize a piece of the same wood weighing the same amount, but this time it's a 6x6 block that's only 32 inches long. The 90 degree pivot is a lot easier.

You do the same thing when you ride. Anything that you do to change the attitude of the bike rotates it at the CG on one of 3 axis, vertical, lengthwise, or crosswise. The more weight is moved away from the ends of the bike, the easier these changes of attitude become, and the less load they place on the tires to accomplish the change in direction. When turning, weight on the front both helps and hinders. It adds to the force that pushes the tire into the surface, but also to the force trying to get the tire to slide across it instead of following its track, much like trying to walk along a slippery side hill. In cornering a motorcycle, there is not only a downward force, but an outward force as well. Considering that the outward force is the result of trying to rotate the motorcycle so that it points in a new direction (lateral acceleration), it makes sense to make that rotation as easy as possible to accomplish.

In the Honda CRF, the '06 YZF, and the first YZ450's you have 3 motorcycles whose weight is within 4 pounds of identical. Two of them handle much better than the other one, and it's because their mass is better centralized. They turn and lean far more easily, and are less top heavy because of it.

:thumbsup:

  • grayracer513

Posted September 27, 2006 - 09:17 PM

#26

... in the places I usually ride most of the dirt is hard packed and rocky, with the occasional muddy or sandy spot but 95% hard pack/rocks/roots.

Sounds hauntingly familiar. Give a Bridgestone M401 a try. If not that, a Dunlop 952.





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