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Go Back   DCSportbikes.net > Sportbike Operation > Test and Tune

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  (#1)
Warming up the tires
 
bike4fun's Avatar
 
Posts: 561
Join Date: October 18, 2004
Location: Ashburn, Va
August 1, 2005, 02:22 PM

While I understand the basics of what the suspension setting of a bike are for (sag, pre-load, rebound, dampening, etc.), what I don't understand is how each affects the handling of the bike.

Can anyone explain how changing each affects a given handling characteristic.

Such as pre-loading the front suspension. Does this cause the bike to dive more/less under hard braking? Also, what does more or less nose dive means on the road (straight braking, entering curves, etc.)?


naked blue 2003 SV1000
red 2014 Honda Interceptor - VFR 800

Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe. - Albert Einstein
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  (#2)
Has an idiot exemption
 
Triple X's Avatar
 
Posts: 8,501
Join Date: September 29, 2002
Location: Stephens City, VA
August 1, 2005, 03:40 PM

Damn...no way can I type an answer to that question.
I suck at typing
Give me a call and I'll talk you through it.
Or better yet, come to the Cornerspeed school and you can feel the differences as we change them...


Steve
2015 Yamaha R1
2011 Harley Electra Glide Limited
2009 Yamaha Zuma 125
2006 Honda CRF150F
2004 Honda CRF150F Monster
2003 Honda CRF 150F Mini-monster
www.cornerspeed.net
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  (#3)
Suddenly Superstitious!!!
 
MudDawg's Avatar
 
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Join Date: August 25, 2004
Location: Dulles
August 1, 2005, 04:24 PM

Yes...I can answer your questions....Not a suspension guru here...just know what works for me.

Static sag - the amount the suspension settles under just the bike's weight.

During riding you don't want to ride topped out on the suspension...otherwise dips in the road will cause you to come out of contact if the suspension can't push down further.

This is taken 2 ways Lift the end of the bike that you are measuring up...then let it settle slowly. Take the measurement.

Push down on the bike and let it rise. take the measurement.

Add the two measurements together and divide by 2. (To account for stiction...we'll get to that later) You will have your average static sag. Compare that to the topped out measurement.

figure 7-10 mm of static sag

Do the same measurements but add the rider.

You should end up around

Street riding - 30-35 mm
Race track - 25-30mm

That would put you around 70% of the suspension stroke.

Static sag...questions?


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  (#4)
Suddenly Superstitious!!!
 
MudDawg's Avatar
 
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Join Date: August 25, 2004
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August 1, 2005, 04:27 PM

Pre-load - adjusting the tension of the suspension (Front or rear) to set the sag correctly. This also means that you should determine the Spring Rate for your bike and weight. (See RaceTech suspension for help on this for your bike.)

Too little pre-load and you will bottom out quickly causing wheel poor handling. (Like front wheel lockups under hard braking, front diving too fast, Rear end coming off the ground under medium/hard braking, etc.)

Too much pre-load and you will be riding a proverbial pogo stick.


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  (#5)
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August 1, 2005, 04:30 PM

Rebound - This is where the suspension literally "rebounds" back from being compressed over a bump.

Too little rebound damping (too fast) and you are literally sitting on a pgog stick and can lose contact with the ground.

Too much rebound damping and the suspension can't return to it's original mid-line. It's in effect 'packing down' under repeated bumps. Would end up feeling very harsh in bumpy areas.

Common problem I've seen with rebound...mid-turn...fast ones. If the front is literally 'hopping' while you are at full lean...it's probably rebound. Slowing it down just a tad has always helped me in these cases.


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  (#6)
Suddenly Superstitious!!!
 
MudDawg's Avatar
 
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August 1, 2005, 04:38 PM

Quote:
"Such as pre-loading the front suspension. Does this cause the bike to dive more/less under hard braking? Also, what does more or less nose dive means on the road (straight braking, entering curves, etc.)?"
OK...usually you make single changes to your suspension at a time.

You would add pre-load to the front if you were bottoming out. (Use the tried and true ziptie measuring tool here.) OR...you could add some compression damping if yo thought that might be it. Depends on what you like for feel from the bike.

Pre-loading would make the front stiffer or possible more harsh on bumps. It would also keep the front from diving. But too much pre-load without countering rebound could cause a pogo effect.

If you are new at this....I would suggest ONE and only one input to the bike at a time. Braking, throttle, steering change....but not a combination of them. Trail braking is more of a passing skill IMHO. You shouldn't need it for the street.

Kevin Cameron (Or is it Keith?) Wrote a book about Performance Biking...or something like that. It's a good read and explains in more detail...with diagrams. Well worth picking up to get mroe of an idea.

If you really want suspension work...have it done for you. Very few newer generation bikes...can be done by relatively technical idiots. (My SV is one of them luckily!!!)

What kind of bike are we talkig about?


I want my baby back, baby back, baby back....Chileeeeee's bay back...
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  (#7)
Warming up the tires
 
bike4fun's Avatar
 
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Join Date: October 18, 2004
Location: Ashburn, Va
August 2, 2005, 08:07 AM

SteveZX9, I would like to go to a cornerspeed event, just need to get everything scheduled. It's probably not going to happen this year.

MudDawg, thanks for the info. I knew what most of the changes did, just wasn't sure what the handling result would be. The pogo analogy makes sense. My bike is a SV1000.


naked blue 2003 SV1000
red 2014 Honda Interceptor - VFR 800

Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe. - Albert Einstein
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  (#8)
Suddenly Superstitious!!!
 
MudDawg's Avatar
 
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August 2, 2005, 03:27 PM

OK...for your bike I believe that the front forks are NOT damper rod forks like it's smaller sibling. That means you'd have to haev a suspension guy re-do them for your intended application. (Street or track.) As for the rear....I'd go with a Penske twin clicker shock. Good bang for the buck.

Yes...the first upgrade to a bike should be suspension. Engine only works while going in a straight line. Once you start turning...somebody with better suspension will carry more corner speed. Don't believe me...come out to the Loudoun track day on the 8th.


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  (#9)
old fat and slow
 
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August 2, 2005, 09:22 PM

i believe that jon from ctr suspension will be at summit this weekend for the races. he comes very highly recomended. ask brooks and a few others. ask steve what he thinks of the forks on my bike after jon rebuilt them for my size. i think he charges like 45 for a basic set up. very reasonable. it will make a difference.


MissS:no now!!!

bambam nope you said i have a few hours

MissS: I changed my mind

bambam: see MissS: well, you have a few hours

MissS: I'm a female, allowed to do it
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