Another good thread on the topic - http://www.m3post.com/forums/showthread.php?t=484793
This is an amazing 25 page guide on dampers. http://www.kaztechnologies.com/wp-content/uploads/2014/03/A-Guide-To-Your-Dampers-Chapter-from-FSAE-Book-by-Jim-Kasprzak.pdf
And a quick suspension tuning cheat sheet: http://www.ncrscca.com/autocross-tuning-tips
I caution the use of the 2nd sheet (the ncrscca page).
It doesn’t detail out whether the conditions are on entry, middle or exit of the corner.
It also doesn’t detail out whether the conditions are during braking, on power or off-throttle. Following those guidelines may confuse the user more than help. FWIW. It’s not as simple as those guides usually tend to make it out to be.
IE: they write:
[i]Understeer
Vehicle is understeering but has sufficient body roll
Decrease front ride height.
Increase rear ride height.
Stiffen front dampers by two or three clicks.
Decrease front tire pressure by 2 PSI.
Increase camber degree (if possible).[/i]
- If you are understeering + decrease front ride height, you can INCREASE understeer bc you have dropped your roll center!
- If you stiffen front dampers, you get less understeer on entry, but more understeer on exit
- If you decrease front tire pressure, you get less initial turn in response, more understeer on entry but more mid corner bite
So as you can see, without understanding and/or identifying how and when the understeer is caused, their tips aren’t actually going to help you.
I should have shock dyno results tomorrow evening, from the JRZ RS1. Sometime next month I’ll run the used factory dampers on the same dyno to see how crappy they were.
Could you explain why that is? I’d like to improve my understanding of suspension dynamics. Stiffening front dampers will cause the car to roll over onto the outside tires at corner entry slower, correct? (and obviously the same but in reverse on exit) How does this correlate with understeer with corner entry/exit?
Forgot to say, stiffening the front dampers also makes the weight shift faster onto the outside rear wheel producing less oversteer on entry which I guess means comparably more understeer?
wow nice west, wonder if you can drill through the shock tower into the engine bay so you can adjust them, i did that on my b5 when i had kwv3’s to get to the damper adjustment without having to remove it each time. The rears wont be that bad as there is only 3 bolts holding the strut on.
I kind of want to set it and forget it. Unless something is seriously unstable on track.
Sorry, didn’t see this until now.
Remember, there are multiple parts to a corner. At the most basic, it’s entry, middle, and exit. Each phase requires different driver inputs if you want to go through the corner as fast as possible. That said, if we are focused on addressing the entry phase, then you want more bump stiffness. There are a few reasons:
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When you turn your steering wheel, the suspension will react (read: roll), and roll is what slows down weight transfer. The slower the weight transfer takes to occur, the longer it takes for your car to change direction as a result of steering input. In other words, if the front end of the car is soft, then when you turn your wheel, the soft front end must roll slowly first…and then only after the roll has completed will the car change direction.
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Camber deflection. Factory cars all have rubber bushings. These deflect for the sake of nvh. But are no good for keeping a proper wheel alignment. As a result, when you begin cornering, your front outside wheel will gain some positive camber (that is, it isn’t necessarily becoming positive, but it is less negative than when it was going straight). This reduces outside front tire grip–which is the most important tire for cornering (as it takes the most load).
So when you have a firmer front end (more bump stiffness), your front end will not roll as deeply–meaning it takes less time for weight transfer to occur (read: faster). This will increase responsiveness of the front end…aka, make the car more pointy–greater initial steering response. Faster reaction time. This, combined with the fact that a firmer front end resists camber deflection more (if the suspension is less prone to rolling, there are less geometric forces acting on the suspension to influence camber), then your tire is in better contact with the ground. Thus, you have more front end grip + less roll = faster turn-in response.
You are correct in your next post in identifying that a firmer front end transitions more weight rearward, so you get more rear-end grip. You’ll find many rwd race cars prepared this way on purpose. It’s generally going to be the fastest setup for a front engine, rear drive car. With a firm front end, you have a pointy car that can get directed to the apex of a corner rapidly. Then, you have lots of rear-end weight transfer to weight the rear wheels (drive wheels!) so that you can get on the gas sooner and harder to blast out of the corner. This is why you see rwd cars lifting the front inside tire upon corner entry. Massive front end stiffness…
The suspension designer at PSi is chiding me for having a 650 spring rate at the rear. He personally feels 400 is the right number, citing the motion ratio of the B8. I cited much higher rates in the B7 RS4 rear like 1000 and he pointed out a different motion ratio. My dampers are valved such that I could go down to 550 without an issue. Will have more data soon.
Motion ratio of B8 is 0.6 rear. With a 650lb rear spring, it puts you at a wheel rate of only 234lb/in.
For the record, stock wheel rate at the back (based on S5 spring rate) is 158lb/in
It is less than 100lb/in increase. Not certain it is a huge deal. But also, depends on what you are looking to address from a handling perspective. Upping the rear rate this much may allow you to remove the rear sway all together. You get the same/similar effective wheel rate, but less mass, and more independant suspension action.
Also, according to stasis, “most audis are 0.8 in the rear” for motion ratio.
If that is true, B7 is even stiffer out back compared to the b8.
And for the record, an E36 M3 is 0.65 motion ratio in the back. And the PSS9 rear spring on the E36 is about 600lb/in.
Still not seeing the problem.
Running a big rear bar I’d be concerned, as you don’t want to pick up the inner rear wheel bc we have the sport diff! But stiffer rear springs? And being approx #230… is ok. You can play with alignment to compensate other areas.
What were your front rates again?
Quoting this for RS4nightmare incase he misses my response from the previous page 
I have some data. I suppose I’ll start with the adjustment in the middle (12/24) for lack of a better starting place. Any advice @boro?
Front JRZ RS1 (at 0, 4 and 22 clicks, out of 24 possible)
http://i58.tinypic.com/2v16alw.jpg
Rear JRZ RS1 (at 0, 4, and 23 clicks, out of 24 possible)
WOW those shocks are SO PROPER!
Those are by far the best dyno’s I’ve seen. They look doctored 
Really clear digressive curve, distinct rate changes with each adjustment and progressive jumps in the curve to correspond with the clicks. That almost never happens!
Also really nice to see that the max curve on both front and rears are similar.
Honestly though, not easy to say where to start without driving the car first.
I actually would not put the fronts in the middle as a start, as the difference between each adjustment is very distinctive with your JRZ’s. I would be tempted to start near the lowest and go up from there to get the rebound you require to suit the springs/pace of the car/corner(s) on the circuit.
Put the fronts at #4 and go from there.
For the rears, you’ll need more to go with your spring rate (more rebound–plus, it’ll address some of the chassis balance “issues”). Rears I’d start with #9 or so. It looks like the base curve is roughly 50% less than the fronts, that’s why I’m suggesting such a big jump in the back.
The best $60 I ever spent was getting your advice in exchange for the data. We won’t know how proper it truly is until I go back and put the OEM’s that I beat up on every apex curb of every track in California.
PSi is a big Ohlins shop so they pretended to be nonplussed by JRZ, or Moton, or TPC Racing. Completely dismissive of any mass market coilover like a Bilstein. I think JRZ is a good compromise.
Sorry to bomb this thread with charts from a different car, but could help but notice how similar the rear chart was to mine.
http://tapatalk.imageshack.com/v2/14/12/04/0243d64b3234cda7b52b2b4253585440.jpg
Ehh… Maybe not that similar.
Are there any B8 platform concerns with using a 2" hole saw to drill holes in the shock towers so I can access the adjustment knobs? Getting the JRZ installed today.
So it’s pretty simple to drill the front shock towers. For the rears it is not possible because it’s some double hulled construction. Instead in the rear you poke a 3" hole in the wheel lining and slice flaps into it. Technically you could wrap your hands up around there and make an adjustment. Although it only takes about 10 minutes to pull the whole shock assembly out.
I set it 8/24 front and 12/24 rear. EDIT: this is probably too aggressive. Will revert to 4/24 in front and 6/24 rear.
http://tapatalk.imageshack.com/v2/14/12/12/89c7ee81e83c888b86186ac3f721b943.jpg