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Ohlins DFV Driving Impressions (Street/Touge)

Old 01-27-2014, 03:27 PM
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Originally Posted by thomsbrain View Post
Let us know what you think of them on track. I've been looking at these as a possible compromise coilover. My custom-valved Bilsteins feel great on the track but are very rough in the mountains. Mac and I got them to where they have excellent body control and good balance but they aren't very compliant on the street. I want something that can be comfortable on the street but am not willing to give up any performance on track. I'm concerned the DFV's will be too soft on track.

I wonder if the rears can handle 14k springs without a re-valve? I want to try a 12k Front / 14k Rear non-staggered setup with a soft rear sway (or no rear sway) and stiff front sway.
Better to just run a rear spring rate that gives you the balance you want while keeping the rear sway bar or get a stiffer front sway bar instead. Or adjust your alignment to suit the spring rate rather than go for softer or no sway. Even when running massively stiff springs the sway bar will still have an effect. My setup I find to be extremely neutral now, but I am sure some would describe it as a bit loose. It all comes down to how you drive the car though. Definitely a huge factor in how my car is balanced and drives is the alignment, as the spring rate bias front to rear hasn't changed dramatically from my stock 06 AP2 springs.

I would argue that too soft for the track is a bit misleading way of looking at things too. Matt is using HKS Hypermax IIIs that use 13kg 10kg with excellent results on street tires. Mac uses 750lb/in (13.4k) 650lb/in (11.6k) with his Ohlins TTX with great results as well. I think as Mac had told me once, more compression is better than more spring in many cases. I think 12kg/10kg would be great on the track with a square setup. That is what I plan to try when I move to square initially I think. It seems like +2kg in the front is a good common option for S2000s with square setup and no aero. While 16kg all around is the most common option for cars with full aero setups.
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Old 01-27-2014, 03:34 PM
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Originally Posted by Redline S2K View Post
How you compare these to KW Variant 3's? I'm looking into one of the two as my next set of coils.
I have never tried or ridden in a car with V3's. Dual Flow Valve is the truth though, I can definitely say that much. The adjustment setup on the V3s looks kind of annoying as well, but I have never used it in practice.
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Old 01-27-2014, 04:55 PM
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Originally Posted by andrewhake View Post
Originally Posted by thomsbrain' timestamp='1390846565' post='22985443
Let us know what you think of them on track. I've been looking at these as a possible compromise coilover. My custom-valved Bilsteins feel great on the track but are very rough in the mountains. Mac and I got them to where they have excellent body control and good balance but they aren't very compliant on the street. I want something that can be comfortable on the street but am not willing to give up any performance on track. I'm concerned the DFV's will be too soft on track.

I wonder if the rears can handle 14k springs without a re-valve? I want to try a 12k Front / 14k Rear non-staggered setup with a soft rear sway (or no rear sway) and stiff front sway.
Better to just run a rear spring rate that gives you the balance you want while keeping the rear sway bar or get a stiffer front sway bar instead. Or adjust your alignment to suit the spring rate rather than go for softer or no sway. Even when running massively stiff springs the sway bar will still have an effect. My setup I find to be extremely neutral now, but I am sure some would describe it as a bit loose. It all comes down to how you drive the car though. Definitely a huge factor in how my car is balanced and drives is the alignment, as the spring rate bias front to rear hasn't changed dramatically from my stock 06 AP2 springs.

I would argue that too soft for the track is a bit misleading way of looking at things too. Matt is using HKS Hypermax IIIs that use 13kg 10kg with excellent results on street tires. Mac uses 750lb/in (13.4k) 650lb/in (11.6k) with his Ohlins TTX with great results as well. I think as Mac had told me once, more compression is better than more spring in many cases. I think 12kg/10kg would be great on the track with a square setup. That is what I plan to try when I move to square initially I think. It seems like +2kg in the front is a good common option for S2000s with square setup and no aero. While 16kg all around is the most common option for cars with full aero setups.
Excuse the following if it is hard to follow as I'm not always the best at explaining my thoughts:

I know it is really common for people to run stiffer springs up front than the rear, but I suspect this is a coilover manufacturer band-aid to maintain grip balance that would be better solved using sway bars. But since they don't sell tuned sway bars WITH coilovers as a unified package, coilover manufacturers have no choice but to tune balance using springs, whether that is the right tool for the job or not.

Meanwhile, there's a lot of independent documentation out there to support the importance of having the natural frequency of the rear suspension be HIGHER than the NF of the front suspension. I know it's an over-simplification as motion ratios and geometry play a big factor in NF, but all things being equal, with a 50-50 weight distribution like the S2000 you would need stiffer springs in the rear than in the front in order to have a higher NF in the rear. The point of having rear NF higher than front NF is it allows the car to react to bumps in a unified motion and reduce out-of-sync squat and dive motions. When the car reacts in a single motion, it can maintain grip better over bumps than when the front and rear are out of sync.

Now we've tuned the motion of the car over bumps using spring rates and we've ended up needing stiffer rear springs. Given those stiffer springs in the rear, the car will tend to be loose during steady-state cornering on non-staggered tires, so now you tune the grip balance back to neutral using sway bars (stiff up front, less in the rear).

It seems obvious to me that you should tune the car to react to bumps in a neutral way with springs, then tune balance using bars. If you try to tune balance using springs and match valving front to rear, the car will have a pogo-ing rear end because the rear will be undersprung and react to bumps too slowly. Then you are stuck trying to band-aid the car's NF over bumps using only the shock, which is going to result in unpredictable behavior based on bump speed, valving, and car motion. Because you used the wrong tool for the job, you sacrificed grip. I think Mac and I saw this on my Bilsteins. With 12k front and 10k rear springs, we kept having to add stiffer and stiffer rear valving to try to get the rear to move in line with the front. So I have these rock-hard rear shocks over bumps but the rear still moves too much in low-speed motions and steady state cornering, so I still have to use a massive rear sway bar to keep the balance neutral.

Now if someone can point me to the data that shows using higher spring rates in the front is actually what is required to achieve an ideal NF ratio front-to-rear in the S2000 because of the geometry, I will be all ears and chalk my 12k/10k difficulties up to inexperienced shock valving. But I think it is worth noting that every stock S2000 except the CR has shipped with higher spring rates in the rear than the front. And it is the AP2s, with their somewhat reduced rear spring bias that are notorious for having pogo-ing rear ends.

And since coilover companies sell coilovers as a package that needs to feel "balanced" out of the box, they have no choice but to run higher front spring rates. They can't count on you changing your bars to balance the car. Look at Mac, who ended up going back to OEM bars in order to balance his car on the Ohlins. Ohlins chose rates that would balance using OEM bars because they had no other choice. It's either that or they have to sell the coilovers and bars together in a single package. Yet maximum grip may actually be achieved by running higher REAR rates combined with changing the bars to balance that.

What I want to try when I get the money is a nice adjustable damper with 10k/12k or 12k/14k springs with a Gendron front bar and the AP2 rear bar.

Please feel free to set me straight on anything above as I want to learn more than I want to be right. I especially would love to see the NF's calculated for the S2000.
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Old 01-27-2014, 06:09 PM
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Springs ARE the right tool for the job in my opinion. But even more so alignment is the greatest tool in tuning how a car is balanced with springs mainly accounting for the car's weight balance and suspension design.

Here is the stupid non-engineering way too look at things: The car has essentially 50-50 weight distribution and similar front and rear suspension design. Therefore let's use the same spring rate front to rear and similar sway bar rates front and rear. This car now has the beautiful slight oversteer on corner entry but we don't think it is safe for normal driving. Add 1 more degree of negative camber to the rear compared to the front and some rear toe-in. Problem solved. Car is still fun but not scary for the novice driver. So the idea behind my setup is essentially removing the safety factor that Honda seems to have added to the stock car. Minimal rear toe-in and more camber in front than in rear, with spring rates that are similarly balanced to stock.

Of course it is more complicated than that but it the end I got exactly the result I was after. All of the OEM sway bar rates are very close to being even front and rear. It would be awesome to be able to talk to the Honda engineers and know exactly why they chose the rates they did though.

I think once you start into the world of relying on the sway bars to keep the car from drastically understeering or oversteering you are already up against the ropes and are going to start heading down the rabbit hole. In the future I would love to get a setup like the 3-way adjustable ASM bars to have some options when dealing with different tracks and different track conditions, but still having the option of running similar rates to stock.
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Old 01-28-2014, 06:06 AM
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Originally Posted by andrewhake View Post
Here is the stupid non-engineering way too look at things: The car has essentially 50-50 weight distribution and similar front and rear suspension design. Therefore let's use the same spring rate front to rear
This is why there are engineers! Spring rate is not what's important, WHEEL rate is. The motion ratios are different, front vs. rear, so same spring rate all around means you will have differing front/rear WHEEL rates.

Should be checked, but quick search gives 0.70 for front motion ratio, and 0.67 for rear.
If that's right then the front WHEEL rate is spring rate * (0.70)^2, and rear WHEEL rate is spring rate * (0.67)^2.
Same spring rate all around would give you front wheel rates that are (.70/.67)^2 or 1.09x stiffer vs. rear. Not huge, but definitely should be taken into account.

Can anyone confirm or correct .70 and .67 as the S2000 motion ratio?
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Old 01-28-2014, 06:30 AM
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I mentioned this in another thread last night, but it (almost) completely depends on tire capability, aero package and driver preference. Wider or stickier (R-compound) tires will give you more grip as you load them more. To take advantage of the grip, stiffer springs are necessary. If you add aero load, even stiffer springs are necessary. I'm not saying that considering the natural frequency is wrong, but with more adjustability (damping no longer fixed at stock rates) you can control the springs and almost any harmonics that come along with it. When setting up race cars, the set up for each track has been different - and that includes spring rate, damping curves, alignment and ratio between front and rear. Just consider that there may not be a hard and fast rule for the optimum set up and ratio of front to rear springs.

Also, when thinking about the CR, it's important to think of the all additions to that car. It really was a tuned package. The tire package was stickier Bridgestones and suspension was set up for aero loading, so the springs were stiffer so the damping rates and bars were tuned to match. Also, the rear tires were wider, the steering rack was sped up and stiffeners were added. The tires had more available grip, so the suspension, steering and aero were tuned to make the most of it and still not chatter your teeth unbearably when going over bumps. The tuning of the CR by Honda is a good mentality to follow when improving our cars.
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Old 01-28-2014, 10:03 AM
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Originally Posted by ZDan View Post
Originally Posted by andrewhake' timestamp='1390878594' post='22986367
Here is the stupid non-engineering way too look at things: The car has essentially 50-50 weight distribution and similar front and rear suspension design. Therefore let's use the same spring rate front to rear
This is why there are engineers! Spring rate is not what's important, WHEEL rate is. The motion ratios are different, front vs. rear, so same spring rate all around means you will have differing front/rear WHEEL rates.

Should be checked, but quick search gives 0.70 for front motion ratio, and 0.67 for rear.
If that's right then the front WHEEL rate is spring rate * (0.70)^2, and rear WHEEL rate is spring rate * (0.67)^2.
Same spring rate all around would give you front wheel rates that are (.70/.67)^2 or 1.09x stiffer vs. rear. Not huge, but definitely should be taken into account.

Can anyone confirm or correct .70 and .67 as the S2000 motion ratio?
Absolutely right! I am aware of all of this. I believe those are the correct motion ratios for the AP2 and the motion ratios differ for the AP1 slightly. That's why I called it the stupid method and said similar suspension design, not identical. This is almost certainly why Honda chose the spring rates they did for all models but the CR, as well as accounting for ride height and many other things. I was considering running 550 F and 600 R for this reason (which would give even wheel rates F and R) but was interested to see if I might get less brake dive with the slight front bias that I get from running 550 all around and then adjusting the balance by adding some more negative camber up front. The additional camber up front doesn't seem to have effected my braking grip much. If anything I find myself braking much later now because the car responds to inputs faster and there is less dive.

Thanks for bringing it up though. I don't mean to discredit any engineers. Luckily for us this car has great suspension design front and rear so suspension setup is quite a bit less complicated than most other cars.
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Old 01-28-2014, 10:04 AM
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Originally Posted by ZDan View Post
Should be checked, but quick search gives 0.70 for front motion ratio, and 0.67 for rear.
If that's right then the front WHEEL rate is spring rate * (0.70)^2, and rear WHEEL rate is spring rate * (0.67)^2.
Same spring rate all around would give you front wheel rates that are (.70/.67)^2 or 1.09x stiffer vs. rear. Not huge, but definitely should be taken into account.

Can anyone confirm or correct .70 and .67 as the S2000 motion ratio?
If that's accurate, then we definitely would want stiffer rear springs to achieve an optimal NF ratio. Even with equal springs, you would still have net front bias on the wheel rates.

OEM rates ranged from 2% stiffer in the rear to 32% stiffer in the rear. Always stiffer in the rear, though. Stock bar rates ranged from 12$ stiffer in front to 32% stiffer in rear.

Andrew, I think it's worth noting your current 10k/10k setup has far more negative front camber than any stock setup, which probably helps to make up for the fact that your current suspension setup would otherwise favor understeer at the limit based on tire size and tire loading. So you may have achieved neutrality in spite of your spring choices rather than because of them.

If you choose to tune tire loading using springs, you are choosing to throw away the option to tune how the car reacts to bumps with anything other than the shock, and I think that's not the right way to do it. Why waste spring tuning on tire loading when sway bars exist for NO OTHER REASON than to tune tire loading? Sway bars are the tool for the job.

The way I see it:

1. Tune car motion using springs, taking into account weight, wheel rate, tire's potential for grip (compound and size), and downforce.
2. Control those chosen springs with appropriate shock valving.
3. Fine-tune desired tire loading balance with sway bars as necessary.
4. Fine-tune tire contact patch with alignment.

If you skip any of those steps or do them in the wrong order, you're likely to be sacrificing grip.

I'm really enjoying the discussion so please feel free to continue to educate me or point out errors in my logic. With limited time and money to play with these things in the real world, I'm kinda arm-chair racing here.
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Old 01-28-2014, 10:09 AM
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Originally Posted by Gottabfast View Post
I mentioned this in another thread last night, but it (almost) completely depends on tire capability, aero package and driver preference. Wider or stickier (R-compound) tires will give you more grip as you load them more. To take advantage of the grip, stiffer springs are necessary. If you add aero load, even stiffer springs are necessary. I'm not saying that considering the natural frequency is wrong, but with more adjustability (damping no longer fixed at stock rates) you can control the springs and almost any harmonics that come along with it. When setting up race cars, the set up for each track has been different - and that includes spring rate, damping curves, alignment and ratio between front and rear. Just consider that there may not be a hard and fast rule for the optimum set up and ratio of front to rear springs.

Also, when thinking about the CR, it's important to think of the all additions to that car. It really was a tuned package. The tire package was stickier Bridgestones and suspension was set up for aero loading, so the springs were stiffer so the damping rates and bars were tuned to match. Also, the rear tires were wider, the steering rack was sped up and stiffeners were added. The tires had more available grip, so the suspension, steering and aero were tuned to make the most of it and still not chatter your teeth unbearably when going over bumps. The tuning of the CR by Honda is a good mentality to follow when improving our cars.
I think your absolutely correct except when it comes to the spring rates they chose for the car. It really seems like they were chosen to account for people running square setups with 255 all around and not the 215/255 setup it came with. Having driven a car with the full CR setup I think the spring rate bias they chose was way too conservative, but I suppose they don't want to sell a car to the public that has that nice slight oversteer on corner entry that you get from a well tuned setup.

Also the CR aero doesn't create net downforce just reduces lift I believe. Even the average rear Voltex wing is only creating a small amount of net downforce according to wind tunnel testing Voltex posted up. So it definitely has to be taken into account but it starts to get much more important when significant downforce is being created.
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Old 01-28-2014, 10:16 AM
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Originally Posted by thomsbrain View Post
Originally Posted by ZDan' timestamp='1390921594' post='22986935
Should be checked, but quick search gives 0.70 for front motion ratio, and 0.67 for rear.
If that's right then the front WHEEL rate is spring rate * (0.70)^2, and rear WHEEL rate is spring rate * (0.67)^2.
Same spring rate all around would give you front wheel rates that are (.70/.67)^2 or 1.09x stiffer vs. rear. Not huge, but definitely should be taken into account.

Can anyone confirm or correct .70 and .67 as the S2000 motion ratio?
If that's accurate, then we definitely would want stiffer rear springs to achieve an optimal NF ratio. Even with equal springs, you would still have net front bias on the wheel rates.

OEM rates ranged from 2% stiffer in the rear to 32% stiffer in the rear. Always stiffer in the rear, though. Stock bar rates ranged from 12$ stiffer in front to 32% stiffer in rear.

Andrew, I think it's worth noting your current 10k/10k setup has far more negative front camber than any stock setup, which probably helps to make up for the fact that your current suspension setup would otherwise favor understeer at the limit based on tire size and tire loading. So you may have achieved neutrality in spite of your spring choices rather than because of them.

If you choose to tune tire loading using springs, you are choosing to throw away the option to tune how the car reacts to bumps with anything other than the shock, and I think that's not the right way to do it. Why waste spring tuning on tire loading when sway bars exist for NO OTHER REASON than to tune tire loading? Sway bars are the tool for the job.

The way I see it:

1. Tune car motion using springs, taking into account weight, wheel rate, tire's potential for grip (compound and size), and downforce.
2. Control those chosen springs with appropriate shock valving.
3. Fine-tune desired tire loading balance with sway bars as necessary.
4. Fine-tune tire contact patch with alignment.

If you skip any of those steps or do them in the wrong order, you're likely to be sacrificing grip.

I'm really enjoying the discussion so please feel free to continue to educate me or point out errors in my logic. With limited time and money to play with these things in the real world, I'm kinda arm-chair racing here.
Enjoying the discussion as well! I am definitely no engineer but I have spent a lot of time learning and thinking about this stuff from a pretty young age and pretty specifically from the standpoint of S2000s. I am always revising my own ideas when good discussions like this come up.

Yeah I think you are correct for the most part. With #1 the ride height also should be part of that list as well I think. But again as I mentioned in my post I was also interested in trying to reduce brake dive slightly, which can be done with spring rate or ride height differences from front to rear I believe. I also saw that my front tires were showing pretty different wear patterns compared to my rears, and wanted to try to correct for that as well. Alignment should be much higher on the list I think in terms of tuning. Because alignment is much easier to change than spring rate it can be used as a pretty simple and powerful way of tuning the balance. I agree that it should mainly be used to get the optimal contact patch if possible and the spring rate should control the balance, but there are so many things that have to be taken into account unless the car is driven in a single perfect scenario.

One thing that is important to remember here. The OEM alignment is in NO way tuned for optimal contact patch when driven hard, even with everything completely stock, including the tire sizes. On all my my RE11's I have gotten noticeably more front shoulder wear, on the OEM alignment, going to -1.6 F -2.0 R helped a little bit but still very far from optimal. I haven't been to the track yet, but have been driving the car pretty hard, and my wear patterns are much more even so far. I am guessing at the track I will be getting just a bit more wear close to the outer shoulders but with my old setup I would have already been wearing the tire out to the little triangles that indicate where the wear bars are on the tire. On the set of tires I just took off those little triangles are long gone. Of course wear isn't the best indicator, but it does provide some data.
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