I have the suspension in the Pink Panther working really good but some of the shock settings have me wondering if it could be better. The front shocks are at full soft on compression and almost full hard on rebound, and the rear shocks are almost at full hard on compression and full soft on rebound. What does this mean? Should I get them revalved? Are my spring rates good?
My first thought is that you're trying to use shocks as springs.
How does the car behave?
In reply to Keith Tanner :
The handling is amazing but I agree with you that maybe the final settings tell me something about my spring rates. What if my front spring rate was slightly softer? Would my compression settings be closer to the middle of the range? Maybe the rear springs need to be stiffer?
Well, why did you set the shocks where you did? Was it for corner entry? Corner exit? How does the car handle in steady state cornering?
My only experience with playing with different shocks and springs is through video games, so take whatever I say with a large grain of salt.
I think of the spring rates F/R affecting how much weight is transferred fore and aft under acceleration and braking and the shocks just change how fast that weight transfer takes place. So, my take on this is that you currently have things set up so that weight transfers quickly forward, but slower rearward. This will tend to shift the handling balance towards oversteer under braking and acceleration.
If you wanted to get your shocks to more of the middle of their ranges without changing shocks, I would think trying softer front springs or stiffer rear springs may help. The other way would be to get different shocks than you have now. This type of problem is fun (and free) to work on in a game, but costs real money and time in real life.
I would think that is the compression and rebound rates differ by too much, you are going to get a ratchet effect in one direction.
Pete
Have you tried altering your tire pressures? This is free to try unlike changing spring rates.
Maybe increase the fronts or lower the rear pressure a bit and see how that changes things. If the car gets too oversteery during braking/turn in, then adjust your front compression and rear rebound shock settings towards the middle of their ranges. If too oversteery under accleration out of corners, then adjust front rebound and rear compression towards the middle of their ranges.
Keith Tanner said:Well, why did you set the shocks where you did? Was it for corner entry? Corner exit? How does the car handle in steady state cornering?
We started with the shocks in the middle of their range, drove a lap, checked tire temps across the tread and adjusted shocks until a perfect balance was achieved. The car is beautifully balanced in corner entry and exit and I can't even think of how the balance could be improved. I just wonder if the final shock settings are an indicator of something else that could improve overall grip.
T.J. said:Have you tried altering your tire pressures? This is free to try unlike changing spring rates.
Maybe increase the fronts or lower the rear pressure a bit and see how that changes things. If the car gets too oversteery during braking/turn in, then adjust your front compression and rear rebound shock settings towards the middle of their ranges. If too oversteery under accleration out of corners, then adjust front rebound and rear compression towards the middle of their ranges.
Tire temps across the tread differ by only 2 degrees after a run so I assume they are perfect and tires are at maximum traction
Based on what you just said, are you not "there" with your suspension. Unless you are lifting tires off the ground, it sounds like you've got it dialed in. Edit, How is the braking and acceleration?
NermalSnert said:Based on what you just said, are you not "there" with your suspension. Unless you are lifting tires off the ground, it sounds like you've got it dialed in. Edit, How is the braking and acceleration?
I kinda think the suspension is pretty dialed in because it is easy to drive fast at the limit no matter what kind of surface. It accelerates and brakes very well but only posed the question because the final shock settings seem strange.
I just went by what you posted. I have a very limited knowledge of suspensions. That car is awesome BTW.
In reply to NermalSnert :
Thanks, I'm pretty happy with it (finally, after spending every spare dime I have on it) and am stoked about the article in GRM. I should just enjoy driving the car now and stop asking these questions ;)
This may be a strange answer, but have you had anyone else drive the car and give you their input? Someone who has experience with a similar type vehicle?Someone with suspension set-up experience who knows what changes to spring rates, dampening, anti-roll bar adjustments, alignment, ride height and tire pressure changes will do.
Sometimes its a huge advantage getting another opinion.
Just a thought since you you are having reservations about the current set-up.
loosecannon said:Keith Tanner said:Well, why did you set the shocks where you did? Was it for corner entry? Corner exit? How does the car handle in steady state cornering?
We started with the shocks in the middle of their range, drove a lap, checked tire temps across the tread and adjusted shocks until a perfect balance was achieved. The car is beautifully balanced in corner entry and exit and I can't even think of how the balance could be improved. I just wonder if the final shock settings are an indicator of something else that could improve overall grip.
You set the shocks by tire temps? I've not tried that. What were you checking and what were you looking for?
How's the steady state cornering balance?
loosecannon said:I have the suspension in the Pink Panther working really good but some of the shock settings have me wondering if it could be better. The front shocks are at full soft on compression and almost full hard on rebound, and the rear shocks are almost at full hard on compression and full soft on rebound. What does this mean? Should I get them revalved? Are my spring rates good?
So I may be reading this wrong, but what I see is that you want to car to take a set quickly (as quickly as the springs will let you), but you want it to say there, and not bounce.
Soft shock = allow the movement to happen quickly on compression, stiff = not bounce, and come out of that stance quickly.
Which suggests that you have your geometry really where you are comfortable with it. Nice job on the chassis design.
The only reason you'd want to revalve the shocks is to go even further soft in compression and stiff in rebound, just to see how it becomes. But I'd totally wait for two seasons before you do that- learn to drive the car better, since you are happy with it. Kind of means that you will have a slow off season, as there are no major things that need tackled, like weight or stiffness or something else. In terms of development, this last 10% is going to take a long time to find all of it.
In reply to lotusseven7 :
I am signed up for the Evolution Performance Driving school in Lincoln and Mike Johnson said he will drive my car and give feedback
In reply to Keith Tanner :
You don't want to fix car balance with tire pressures if you don't have to. My suspension guy took tire temps after each run and kept adjusting them until tire temps were even across the tread. We kept checking temps and adjusting tire pressure after adjusting shocks/roll centre/track width because these changes affected tire temps, too. You can fix a balance issue with tire pressure but ideally you want perfect tire pressures and adjust balance with shock/roll centre/track width/sway bar settings. It's crazy what you can tell from tire temps. If you told me your temps, I could tell you what the balance of your car is.
In reply to alfadriver :
If I send my shocks back to Penske, I'll request a move up or down on the settings so my current settings are at the middle of the range instead of at the extreme
loosecannon said:In reply to alfadriver :
If I send my shocks back to Penske, I'll request a move up or down on the settings so my current settings are at the middle of the range instead of at the extreme
So it sounds like you want the compression softer and rebound stiffer, right? Extend the limits past where you have them at the ends.
And the shock tuning with the tire temps is really interesting- I'm assuming that he took 3 or 5 tire temps across the tire. Based on that, how did he adjust the shocks? I assume before you started it, you found a good baseline tire pressure, right? Most tuning things I've read suggested going over bumps, but the method you used is far more applicable. I'm quite sure if your suspension guy can share some basics on how to change the shocks, that would be very appreciated by this group.
My suspension guy is Ron_Sutton on this forum. You can ask him directly but I think he'll tell you that you have to find optimum tire pressure and you do that by measuring temps across the tread. he recommends no more than 2 degree variance across the tread. I always measured inside-middle-outside and initially the car had much higher rear temps than front because it was oversteery but as we got shocks adjusted and roll centre lowered, the front and rear temps got closer and closer together
loosecannon said:My suspension guy is Ron_Sutton on this forum. You can ask him directly but I think he'll tell you that you have to find optimum tire pressure and you do that by measuring temps across the tread. he recommends no more than 2 degree variance across the tread. I always measured inside-middle-outside and initially the car had much higher rear temps than front because it was oversteery but as we got shocks adjusted and roll centre lowered, the front and rear temps got closer and closer together
That's how I used to do tire pressure, but it's interesting to see tuning like that. I think for most people, the big knob they have is just shock rates. Very few can adjust the suspension geometry other than caster, camber and toe, no way to actually mess with roll center.
When's the next event that's on a good surface?
In reply to loosecannon :
After you get a second opinion, maybe as suggested by TJ, adding and lowering your tire pressures slightly might allow further adjustment of your dampners. And not change the temps across the tire. Or improve that relationship more. And by slightly I mean 1/2, 1/4, or less even. Also, are you using nitrogen or compressed air? Your probably at a point of splitting hairs with this setup. At the use of a set of tires could the information gained get you a win?
In reply to alfadriver :
My next event on a good surface is Nationals in September. I think my car is competitive with Kiesel but my driving is way off. I just can't get enough seat time to drive to the level he is driving. For some reason, I'm really good in the rain so my best chance for a jacket is 2 days of really wet conditions.
I never suggested adjusting balance by tire pressure, but I haven't heard of using temps to adjust shock settings. I wonder how the "same temps front and rear" philosophy works on a car that has a high power/weight or a static weight balance that's far off 50/50.
I've asked a couple of times about the steady state balance and I don't think it's been answered, so I'll assume that's okay. My thought is that you start with getting the basic balance right with springs and/or sway bars, then you use shocks to adjust the transitions. The shocks being at the limits of their adjustments could mean that the basic roll couple is of out of whack, or it could be that the shock valving ranges are just crazy. Thus the back to the fundamentals questions.
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