I've started getting into tweaking the default setups for my needs. Some things like springs and ARB seem easy. Change springs if you want softer or ARB if you are just adjusting tight / lose. But for things like dampening if you can increase the front rebound or decrease the back compession which do you do and how do you choose?
When there are multiple things you can tweak, how do you choose?
(14 posts, started )
When there are multiple things you can tweak, how do you choose?
Depends on what you want to do... The important thing to know is what you feel is wrong/off: If I want the front to decompress slower, I increase front rebound, if I feel the weight shifts too slow initially at the rear, I decrease rear bump... It all depends on the type of corners you do, if it's bumpy, if you're kerbing and so on...
Bob wrote an application where you can load your setups and see the effects of your changes statistically (and graphically): http://www.lfsforum.net/showthread.php?t=16961
Bob wrote an application where you can load your setups and see the effects of your changes statistically (and graphically): http://www.lfsforum.net/showthread.php?t=16961
Yeah I've played with it, its a bit over my head yet so usually what I do is make changes in the car until it feels better, then look at the old and new setup in the analyzer to see what the end result is.
The example I was talking about was that my car was lose under throttle at corner exit. The problem is the mass of the car is basically moving to the rear to fast when I got on the throttle. To solve the problem I could either decrease rebound damp on the front or increase compression damp in the rear. I decreased rebound damp instead of increasing compression and it worked but I just arbitrarily picked one since it seemed both would do the same thing. There's got to be a better way to choose than flipping a coin.
Decreasing rebound at the front will have slightly different side effects on other corners and at different points than increasing compression at the rear. Improving corner exit using the front might make turn in worse (for example - I've not thought about it), and ultimately make you slower, in which case adjusting the rear might have been better. But it might not.
Don't assume springs and ARB are easy. Understanding and visualising load transfer in a dynamic situation isn't easy, and ultimately you are trying to limit this load transfer without making the car harsh or sloppy at critical points.
Don't assume springs and ARB are easy. Understanding and visualising load transfer in a dynamic situation isn't easy, and ultimately you are trying to limit this load transfer without making the car harsh or sloppy at critical points.
So you basically dynamically lowered your car by not letting the front get up while the rear still compresses like before...
What it will affect for sure is turning into the second corner in a chicane or s-bends...
That's why I said it depends on what corners you'll be doing... You'd approach the twisty, swooping corners of Kyoto GP differently than the one-corner-at-a-time Aston National, wouldn't you?
Can you elaborate more on this? I'm having issues with the chicane at Blackwood GP. I was very loose going into the first turn into the chicane. That's fixed but I'm still not as fast as I think I should be through there.
When i'm comfortable with the grip levels one end of the car is giving me, i tend not to change it. For example if the front is gripping nicely but in faster corners the rear is getting loose on the throttle then i soften the rear bump rather than increase front rebound. i find that adjusting the rear has a bigger effect than adjusting the front though, so that might be something you could take into consideration?
It's more the experience I got from tweaking setups than knowledge about what happens, but I'll try to explain: as you steer through the hairpin and enter the chicane, all the load is on the left side... If you then turn in the opposite direction, the weight will stay longer on the left side as it'll take longer to decompress, giving you less load on the right side, thus the car will initially understeer... If you don't get that, don't worry, it's fine...
The understeer on the second part of the chicane is exactly what I am getting. So what would you think the best way to correct that is without causing entry problems. I'm really happy with the way the entry to the chicane feels.
Hard to say really, the main thing is that it feels right for you... From what you wrote, it seems something needs stiffening at the back: if it's really to much weight shifting to the back, you might want to stiffen the springs... If its shifting too much weight to one corner, adjust your ARB a bit... Springs and ARBs kind of set the limits, the dampers define how fast or slow the transition phase is...
That is of course as long as Bob or other setup gurus don't disagree with my statements...
That is of course as long as Bob or other setup gurus don't disagree with my statements...
During the second part of the chicane do you get a nice satisfying (or not) slide going through? I would agree, one of the worse things you can do is keep the car low, you're just gonna end up (because the weight will still shift, but suspension won't react) only having one side of grip.
Also, what sort of powerload does the understeer come in at? Remember your diff settings also affect the amount of grip when cornering. Ultimately, though, you want the compress slower than it decompresses to avoid grounding the car and losing grip completely down one side.
EDIT:
It's definately not a case of flipping a coin to work out what you need to do, possibly the best thing when dealing with suspension is to start with the default hard track setup (a nice place to start) on the skid pad/autocross/BL carpark and just tweak it while driving around testing different settings. Also, try and avoid using locked differentials when working out grip levels and suspension responses. A locked diff leads to understeer/oversteer in very bizarre places.
Also, what sort of powerload does the understeer come in at? Remember your diff settings also affect the amount of grip when cornering. Ultimately, though, you want the compress slower than it decompresses to avoid grounding the car and losing grip completely down one side.
EDIT:
It's definately not a case of flipping a coin to work out what you need to do, possibly the best thing when dealing with suspension is to start with the default hard track setup (a nice place to start) on the skid pad/autocross/BL carpark and just tweak it while driving around testing different settings. Also, try and avoid using locked differentials when working out grip levels and suspension responses. A locked diff leads to understeer/oversteer in very bizarre places.
With regards to the dampers and transient balance; I always try to start off setting this as neutral as possible. I find it's the best place to start as it means the car balance is nice and predictable throughout the whole corner. Bob's program is great for this as you can quickly tweak the dampers keeping a close eye on the displays that show the balance under various conditions. You can then adjust the dampers relative to each other to make sure damping is somewhere roughly in the range 50%-100%; for the spring rates you have chosen. These damping rates pretty much depend on your driving style and how bumpy the track is. The higher the damping the more responsive steering will feel but this will obviously mean that the car will bounce off bumps/curbs more and lose more grip over sudden dips
I might get onto your question now
This would depend on how over or under damped it already is. If the front rebound is already near 100% I'd rather not increase it more so I would reduce the rear compression. If the rear compression is near 50% then I would look at increasing the front rebound.
These changes would give you more oversteer on the corner exit, but it will also give you more understeer on corner entry. That's the compromise.
If you want to use the dampers to increase understeer on the corner exit then you will probably bring back the oversteer problem you had going into the corner. Maybe in your case it would be better to to change the roll stiffness balance between the front and rear. Alternatively, a little toe in on the rear wheels would have a significant effect to increase the rear stability.
I hope it helps
I might get onto your question now
This would depend on how over or under damped it already is. If the front rebound is already near 100% I'd rather not increase it more so I would reduce the rear compression. If the rear compression is near 50% then I would look at increasing the front rebound.
These changes would give you more oversteer on the corner exit, but it will also give you more understeer on corner entry. That's the compromise.
If you want to use the dampers to increase understeer on the corner exit then you will probably bring back the oversteer problem you had going into the corner. Maybe in your case it would be better to to change the roll stiffness balance between the front and rear. Alternatively, a little toe in on the rear wheels would have a significant effect to increase the rear stability.
I hope it helps
Wow, more good info and at the right time. Just tonight I was wondering what the Damp and bump percentages meant in Bob's tool. Now I know I want to keep them between 50 and 100%.
Should I make adjustments to start with them at about 75% or is having the fronts near 100% and the back closer to 50% ok?
Should I make adjustments to start with them at about 75% or is having the fronts near 100% and the back closer to 50% ok?
I personally don’t have an issue with running quite different damping rates on the front and rear if it means I can get closer to the neutral balance. Sometimes I go slightly above 100% if I’m willing to compromise the bump performance for the balance that I like.
As for where to start, I would suggest just trying out a few different levels of damping and see how it affects the car feel and your lap times. All the other suspension components including the tyres will have an effect on what level of damping will be best for your driving style, car and track combination.
As for where to start, I would suggest just trying out a few different levels of damping and see how it affects the car feel and your lap times. All the other suspension components including the tyres will have an effect on what level of damping will be best for your driving style, car and track combination.
When there are multiple things you can tweak, how do you choose?
(14 posts, started )
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