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Discussion Starter #1
I've put 500 miles on my F4 since I got it on Thursday and I've locked up the rear wheel almost a half a dozen times already. Once by downshifting, the rest by jamming on the rear brake in hard braking situations. The bike has an almost new Pirelli Diablo 180 on the rear.

Usually I let off the brake and allow the rear wheel to grab again, and somehow I haven't even come close to a high side even though I'm breaking the rules by not coming to a complete stop.

Anyway, are these things just prone to rear wheel spin, especially since I think my suspension is set up too soft?

I used to be able to brake like a champ on my ZX-7R, but now I'm pretty nervous when braking hard because of the rear wheel spin and the front end diving from the soft setup (even after i set the suspension to "stiff" as per the manual).
 

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Please don't take this wrong, but what you describe is a sign of sloppy riding.

If I am too aggressive releasing the clutch on the track, the back wheel will begin to skid (this is also a legitimate technique used by some racers to "back it in" to a corner) around a bit. This can be remedied by being smoother with your clutch releases.

Using the rear brake during "hard braking" on a modern sportbike is like playing with a bag of rattlesnakes, eventually you are going to get bit. The front brakes are so strong, when coupled with the fairly radical geometry of a sportbike, hard braking with them will have the rear wheel skimming the ground, or actually in the air. Messing with the rear brake in this situation is not good.
 

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Discussion Starter #3
luvtolean said:
Please don't take this wrong, but what you describe is a sign of sloppy riding.

If I am too aggressive releasing the clutch on the track, the back wheel will begin to skid (this is also a legitimate technique used by some racers to "back it in" to a corner) around a bit. This can be remedied by being smoother with your clutch releases.

Using the rear brake during "hard braking" on a modern sportbike is like playing with a bag of rattlesnakes, eventually you are going to get bit. The front brakes are so strong, when coupled with the fairly radical geometry of a sportbike, hard braking with them will have the rear wheel skimming the ground, or actually in the air. Messing with the rear brake in this situation is not good.
I agree with you about the sloppy riding, but the front end really dives when braking hard with the front brake, making me lose a lot of confidence when grabbing a handful on the front brake. All the other bikes I've rode dove much less. Maybe I just need to get the forks recharged.
 

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psperl said:
I agree with you about the sloppy riding, but the front end really dives when braking hard with the front brake, making me lose a lot of confidence when grabbing a handful on the front brake. All the other bikes I've rode dove much less. Maybe I just need to get the forks recharged.
Luvtolean said it all already. Just be smooth.

As for front diving issue, check your sag and forks set up and if that doesn't do it tell the mechanic to change the fork oil.
 

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Discussion Starter #5
MV-999R said:
Luvtolean said it all already. Just be smooth.

As for front diving issue, check your sag and forks set up and if that doesn't do it tell the mechanic to change the fork oil.
The front forks were set up horribly when I bought the bike. The preload was all messed up. I followed the manual to set the forks to "normal", which didn't do much, so I then set them to "stiff", which didn't do much, so I think he forks are just low on oil, which is weird since the seals look 100%.
 

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psperl said:
I agree with you about the sloppy riding, but the front end really dives when braking hard with the front brake, making me lose a lot of confidence when grabbing a handful on the front brake. All the other bikes I've rode dove much less. Maybe I just need to get the forks recharged.
others have helped you already
but..... suffice it to say that.... the more your front end DIVES during extreme DEceleration, the more your rear is up in the air, rendering the rear brakes 110% USELESS.....
they skid because they are no longer contacting the ground... and just spinning freely in the air (almost)



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Discussion Starter #8
luvtolean said:
What is your sag set at?
I don't know what that means. I just set the preload , compression and rebound on the front forks to factory "stiff" and left the rear alone.
 

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my early 750 F4 was the same, the front was miles too soft and the rear had far too much sag in it (30 mm WITHOUT me on it!) take it to a suspension expert and get him to sort it for you :)
 

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Discussion Starter #11
MV-999R said:
Check out this file.
I think it's a good quick guide that makes it easier to understand. :)
Thank you very much. That document seems very informative.

And after reading some of that doc I can say that I am not certain about exactly how much sag I have on the rear, but it's not much. I'm pretty sure it's less than 30mm.
 

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psperl said:
Thank you very much. That document seems very informative.

And after reading some of that doc I can say that I am not certain about exactly how much sag I have on the rear, but it's not much. I'm pretty sure it's less than 30mm.
You're welcome. :)

Now ask some friends to help you out setting the sag first and if that doesn't work make sure the mechanic checks the fork oil or, even better, take it to a suspension expert like Mike said.

Ah and don't forget to report back :drummer:
 

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psperl said:
I don't know what that means. I just set the preload , compression and rebound on the front forks to factory "stiff" and left the rear alone.
Sorry if I put you on the spot with that question.

It is really LAME that shops don't set the sag with you the day you take delivery of a bike. Getting that sag set properly is far more important than anything else you can do to a bike. No matter what the bike is for, you should set your sag before touching any other "clicker" on it. Setting the sag is critical to maintaining the geometry designed by the engineers of the bike, the bike will not work as designed if your sag is off.

The majority of bikes do not have enough preload in the front, and with modern geometry, this often means the front rides low, making the bike less stable. Japanese bikes especially often come with fork springs WAY too soft. The MVs seem to be pretty good stock in the front with the rear springs being soft. This is actually much preferred as the bike is more stable this way and less likely to bite you.

I am quite sure that if more people had their sag set correctly, less dampers would be sold...
 

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TheCatWhisperer said:
I think this is the first time I've read of an F4 rear brake that actually works...:)

Si
Yeah but once he gets his back wheel back on the ground it won't :laughing:
 

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Discussion Starter #17
TheCatWhisperer said:
I think this is the first time I've read of an F4 rear brake that actually works...:)

Si
That's why I'm suprised the rear wheel locks up at all. The rear brake is so squishy and has so little stopping power that it practically does nothing. If I'm going 60 mph and jam on the rear brake it takes a LONG time to stop.
 

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psperl said:
That's why I'm suprised the rear wheel locks up at all. The rear brake is so squishy and has so little stopping power that it practically does nothing. If I'm going 60 mph and jam on the rear brake it takes a LONG time to stop.
Rear brake... What's a rear brake?:confused: We don't need no steenkeeng rear brake!
 
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