Learning to tune my suspension. Guidance welcome.

[standfast]

I went out with a buddy and got some vid today. We did a race with this setup and I new it needed work. After each clip I slowed it half speed to see what is going on. It looks like the rear is close but not perfect. The front looks like it slaps the front face of the whoop and just floats. The settings are at the start of the vid. I did notice my rear C/O's were getting hotter than the BP's for some reason? Is this normal? I thought it would be the other way around. The front end of the car is pretty light so I am sure that is gonna make it harder to dial in.

Where do I go from here?

[ame="http://www.youtube.com/watch?v=6N7PoDa_px0"]YouTube - Susp1[/ame]

 

[Random Thoughts Racing]

The front end is currently to stiff and it is pushing the rear end around. Open compression bypass, if that dosent fix it reduce initial spring rate or reduce coilover compression valving.

 

[standfast]

I pulled the rubber stops up on the BP's before making these runs and noticed at some point in there I completely compress the suspension and push them all the way down. I don't feel it bottom the front there at anytime but at some point it uses all of it. Now if I soften the compression damping even more this could make me start to bottom much easier right? I already have the C/O valve about as light as it will get. Time to open another bleed hole in the compression side of the piston?

The rebound doesn't seem right in the front to me either. Should I do anything to that or is the compression too far off to see if the rebound is OK? It seems like it isn't even trying to push the tire back down off alot of the bumps.

Also, is it normal for the rear C/O's to get that much hotter than the BP's?

 

[Random Thoughts Racing]

I pulled the rubber stops up on the BP's before making these runs and noticed at some point in there I completely compress the suspension and push them all the way down. I don't feel it bottom the front there at anytime but at some point it uses all of it. Now if I soften the compression damping even more this could make me start to bottom much easier right? I already have the C/O valve about as light as it will get. Time to open another bleed hole in the compression side of the piston?

The rebound doesn't seem right in the front to me either. Should I do anything to that or is the compression too far off to see if the rebound is OK? It seems like it isn't even trying to push the tire back down off alot of the bumps.

Also, is it normal for the rear C/O's to get that much hotter than the BP's?

You want to maximize the position sensitivity of the front end. If you remove compression from the coil and it bottoms out put more compression in the bypass instead to control bottoming. If you reduce spring rate a bit add more compression into the bypass or lower the secondary spring stop position.

Do the front before worying about heat in the rear coil. The rear is being overworked because of the non compliant front end.

 

[standfast]

Well, what about the rebound in the front end? Should I make a change there as well?

As far as lightening C/O compression, is opening up the second bleed hole a good idea?

This is on a 2.0 C/O BTW.

My current front C/O valving that I have gotten to to attempt to soften up the front end:

Comp
______________________ 1.600" .008
______________ 1.100" .008
___________________ 1.425" .008
_________________ 1.350" .008
______________ 1.100" .008
___________ 0.950" .008
________ 0.800" .008

Reb

___________________ 1.425" .008
______________ 1.100" .008
_________________ 1.350" .008
______________ 1.100" .008
___________ 0.950" .008
________ 0.800" .008

 

[partybarge_pilot]

Change out the 1.1 second shim for 2 .800's .

 

[standfast]

Change out the 1.1 second shim for 2 .800's .

I am running out of .008 shims. Can I just throw in a .800" x .020"?

You mean to try this on compression and rebound? or just the compression? It seems like it could use less rebound damping to me but I haven't been doing this long enough to know.

 

[Random Thoughts Racing]

I am running out of .008 shims. Can I just throw in a .800" x .020"?

You mean to try this on compression and rebound? or just the compression? It seems like it could use less rebound damping to me but I haven't been doing this long enough to know.

If you need additional .80x .008's you have them on either end of your valve stack. Since this shim is against the washers you can use a .80 x.20 in those positions instead. Only the OD of this last plate matters.

 

[partybarge_pilot]

What he said ^^^^^^ An .020 X .800 would be WAY stiffer than 2 .008's. It would make the face shim want to crack. What your really fighting here is the high ratio of unsprung weight. It's times like these that I go back to thinking about a highspeed blow off set-up similar to what some MX forks have in them as they are fighting similar weight ratio problems.

Double stack both comp and rebound.

 

[baja booie]

you might also want your co dog in with you to make the weight the same as in a race

 

[standfast]

I think the changes I make on the C/O's on the front don't have as much of an effect as the changes I have made on the BP's thus far because the motion ratio difference with the C/O's being inside of the BP's. I figured the motion ratio on the C/O wouldn't be a big deal when I built it that way since the car is so light in the front. I figured it would make it easier to get the car soft enough so I think the C/O changes are not having as big of an effect because of that.

OK. I have enough parts to do this. (Need to order more thin shims, no use for all these heavy ones in my kit) Will this accomplish the same thing more or less? How big of a difference is this than what I had before?

Comp
______________________ 1.600" .008
________ 0.800" .008
________ 0.800" .010
___________________ 1.425" .008
_________________ 1.350" .008
______________ 1.100" .008
___________ 0.950" .008
________ 0.800" .020

Reb

___________________ 1.425" .008
________ 0.800" .008
________ 0.800" .010
_________________ 1.350" .008
______________ 1.100" .008
___________ 0.950" .008
________ 0.800" .020

 

[partybarge_pilot]

That will work, should be a fairly large difference. Problem is, it's all going to be low speed. High speed will be about the same, but I'm not seeing an easy way around that right now.

 

[standfast]

What about opening a bleed hole? Is that high speed or low speed? I am guessing low speed since I am sure you would have thought about that. If it ends up still too far off should I move to revalving bypass' at that point?

 

[partybarge_pilot]

Bleed holes are all low speed.

 

[standfast]

Well what controls high speed valving?

 

[partybarge_pilot]

Yes, the shims and how they are arraigned. There are some newer MX designs for forks out there that have a coil spring pre-loading the shim pack. The shims give good control at low speed and the coil spring provides a high speed blow off. Something like this could be really beneficial on something with a high unsprung weight ratio like the front of your car.

Barrow some center lines and put them on the front........

 

[standfast]

I guess I can try moving the battery to the front and lighter wheels up front. I will go that way if I can get this front end to act reasonable with what I already have. Gonna revalve again before the weekend and have some more vid by monday hopefully. People should start figuring out how to mount the spare tire up front in there buggy designs.

 

[Random Thoughts Racing]

Im off to baja but will check back in next week to see how you are coming along. Hopefully the valving Partybarge suggests will get the coil out of the way compression wise (you can always add some back in later if needed). You should compensate with more bypass valving as needed and to keep the bypass tubes as open as possible on compression. For front rebound start wide open, get the front end moving better and then come back to adjust the front rebound at the end. Definately get a co-driver in the car. You can simulate moving the battery up front with some kind of balast (be safe here you dont want something coming loose and hitting you). Good luck!

 

[bajaxp]

And test it at least 2/3rd's full of fuel.

 

[standfast]

I am testing with fuel levels high. I race with a co-driver but he got out to film this video. I guess I need another person out there to help.