Getting better rear tire grip

[bsavoie]

I have an SV, and race in the lightwieghts.  I find the bike is handling great, except when I drive out of corners.  I usually carry a lot of corner entry speed, and maintain it through the corner.  This will usually let me gain on the people in front of me.  The problem comes when exiting the corner, my rear end doesn't always want to hook up that well when on the gas, I see this every lap.  The guy in front of me always seems todrive out faster, while I am sliding.  I am not a suspension expert, but am thinking maybe not enough preload?  Any thoughts?  I use a fox twin clicker on the back of the SV.  Any help is appreciated. Thanks.

[Protein Filled]

I used to have a Fox twin clicker on my bike and swapped it for a Penske. Huge improvement! I am not saying that the reason why your bike is sliding, but the Penske is tons better.

You can get the Fox revalved with better internals if you wish. That may help quite a bit.

One more issue could be your riding style. The people in front of you that are getting a better drive may be setting up the corner just for that, so while you are going in there at a high rate of speed, you are sacrificing corner exit. You may want to try and enter the corner a bit slower and see if you gain more with the drive out. Corner exit is one of the most important things for getting around a racetrack faster.

[zoner]

Could be a number of things.  What's the rider sag and how much ride height in the rear?  Have you tried adding some ride height in the rear?  I would try that first unless your sag is way out of wack.  Maybe 2-3mm more on the ride height adjuster.

[motomadness]

zoner,

If the rear isn't hooking up, why would you tell him to add more ride height in the rear?  He may need to bring the front up for better weight transfer to the rear, or even lower the rear.

One thing:
Every track is different, so every setup will be different.  Expect that then be open to setup changes.

[H-man]

Bsavoie, I'm a newbie myself who has read and been taught far better than I can execute so with that....

Have you tried standing the bike up sooner as your exiting the corner?  You may be doing this already so you know that by doing so, you will have a bigger tire diameter (less spin) and contact patch with which to make your drive.  Start standing the bike even before you complete the turn and climb back aboard.

H-man

[Super Dave]

Bingo...

H-man wins.

Yeah, suspension can play a role.  Honestly, I doubt that anyone can tell you if your preload, spring rate, or dampening is correct via the internet.

I can usually ball park it in person...

But, honestly, most racers that don't have good dirt track experience focus too much on their corners with long radii that have high corner speed.  You can't put down any power 'cause, even with the SV, you've used up the traction.  You try to put small amounts of throttle down, and it doesn't hook up...you run out of space at the edge of the track.

Yeah, could be suspension, but execution is still a big player...

Here's a question...

Why would you think you need more preload?

Do you know what adding preload would accomplish?

[watsonx11]

Hey Dave,

  Why dont you explain what adding more preload will do.  I have been under the impression that if you pre-load is off then you could cause one of 2 thing.  To much preload and you eat your tire, not enough and your rear wheel will not hook up => cause rear wheel spin.  Now I am a newbie racer, and I am learning more all the time.  Please explain your question.

[Super Dave]

Well, ok, I teach schools to people that race...in addition to peopel that want to start racing.

So, I will restrict myself from just saying one thing or another.

If anyone wants to try answering questions I have, I'll make some statements.  

The flip side is one can go out and drop years of one's time, remain under employed with the aim to go out and race like I did and learn it all that way.

So....

To much preload and you eat your tire, not enough and your rear wheel will not hook up => cause rear wheel spin.

Why would those things happen?  Define "too much preload"?

But we're back to the original question....What does preload do?  

Anyone, anyone?

[tigerblade]

But we're back to the original question....What does preload do?  

Anyone, anyone?

I know but I spent some hard earned $$$ to find out, so I'm not tellin'.   ;D

[Super Dave]

so I'm not tellin'.   ;D

Bingo!  
 ;D ;D

[H-man]

I'll give 'er a shot :)  What have I got to lose except face and reputation ;D

"Preload", as we're using it here, is the force exerted on the spring while the bike is at rest.

I'm going to guess that many folk increase their preload thinking they'll create a stiffer spring (or at least have the allusion of a "stiffer" spring).  So under this presumtion, a rider will crank up the preload thinking it'll stop some rear wheel hopping or loss ot contact with the ground.

As to what is "too much preload", I'd say that's when you've increased the preload to the point that the bike's at, or beyond, the upper boundry of recommended free sag (5 mm I think.  We're talking about the rear wheel, right?).

The thing I can't figure out is why cranking up the preload doesn't give these folks a rough ride - less control - since I'd think they'd bottom out (or top out) easily.  Or more easily.

Then again, maybe they're thinking the increased preload will reduce the amount of squat when they accelerate, thus having most of the energy directed forward instead of forward and upward???

I'd better quit now. :-X

Cheers.
Your student   H-man

[Super Dave]

I'll give 'er a shot :)  What have I got to lose except face and reputation ;D

"Preload", as we're using it here, is the force exerted on the spring while the bike is at rest.

I'm going to guess that many folk increase their preload thinking they'll create a stiffer spring (or at least have the allusion of a "stiffer" spring).  So under this presumtion, a rider will crank up the preload thinking it'll stop some rear wheel hopping or loss ot contact with the ground.

 

Nice job, H-Man...

Good.

Look at it this way.  More preload will not increase the spring rate.  You CAN preload it to a point where it spring binds.  That would increase the rate...kind of like replacing the spring with a strut...LOL!  You get the picture.

So, preload really changes ride height.  It doesn't change the rate, unless it's spring bound.  Might help how the tire wears because of weight transfer, etc.

It can be over done where the shock is topped out.

Really, you've got to try and start out with the correct spring.

And a reasonable and correct geometry.

Most bikes have linkages, so that comes into the mix.

Throw in a rising rate spring like I use and then the sag numbers that I use get compared to a straight rate spring are completely different.

More thoughts?