Need help buying my first coilovers

[uberchris]

After several years of doing autocross, I am shifting more towards doing track days. Since I am no longer building the car to a rulebook, I'd like to improve the suspension. The current setup is pretty typical of SCCA FS class:

• Tires: whatever super 200s are hot each year
• Suspension: Koni yellows with stock springs, TMS front bar, all bushings OE but refreshed
• Brakes: DTC60 pads on stock calipers/rotors

My #1 priority is lap times per dollar. Specifically, I would like to be able to dial in more front camber and increase the stability during high speed transitions. The car only gets driven on the street when I drive to and from the track.

Before I order, I intend to educate myself on flat ride so I can order the right spring rates. But in the meantime, I could use some help picking out an approach so I can know how much to budget. Here are the options I am currently weighing, but of course I am interested in anything I might have missed:

1. Ground Control Coilover Conversion + Ground Control Camber Plate $570 + $440
   This seems like the most cost effective route, by reusing my existing shocks. But am I going to be under-dampened? Also, I assume this will reduce bump travel? Maybe other bad side effects?
2. TCKline Single Adjustable kit $2500
   This kit seems like the best deal on a quality all-in-one kit, but I'm not sure how much I would truly gain over option 1?
3. Ohlins Road and Track + camber plates $2400+$440
   Similar to option 2 but a bit more expensive. Including because so many reviews seem to like this kit.

[S54330Ci]

Let me describe what I have on my S54-powered 330Ci which is a track-only car and only driven on the street to get to the track and back. Like you, I used a racing class specification as a baseline (in my case SPEC E46) and built from there. My configuration may be more than you are wanting to spend and I respect that. I've had great track experiences at Portland International with this configuration. The suspension is fast, controlled and stable. I am not going to comment on your list only because this is much like a motor oil discussion where everyone has their preferred brand, or their own reasons for using a specific brand.

Suspension = MCS 2WNR with coilover rear (For a more cost-effective option do a divorced rear and 1WNR dampers)
Springs = Eibach 2.25" 650# front, 500# rear (my car has no aero enhancements beyond what the stock body delivers)
Swaybars = Hotchkis SPEC E46
Front end links = SPL
Rear lower control arms = SPL
Camber plates = Ground Control Race (-3.8 degrees camber)
Bushes = all solid (aluminum or Power Flex)
Brake pads = Colbalt Friction (XR2 front and XR4 rear)
Tires = Hankook R-S4
Wheels = Bimmerworld TA16 17x9 square

I also have the usual F / R suspension reinforcements that are necessary for any track car.

I honestly don't know what "flat ride" is but have never heard it mentioned in the SPEC E46 paddock. I doubt it is a setup compatible with fast lap times.

Good luck with your suspension build.

[uberchris]

Thanks for sharing your setup! I bet that MCS setup is sweet.

As you expected, I'm looking to spend a little less than that. Too much seat time to be had for that price 😉

[s54brendan]

I doubt it is a setup compatible with fast lap times.

crazy statement to make especially when Porsches all have flat ride in OE specifications and in many of their aftermarket/racing setups

[9kracing]

Porsches all have flat ride in OE specifications and in many of their aftermarket/racing setups

Where did you get this info?

[9kracing]

have never heard it mentioned in the SPEC E46 paddock.

That's because it's made up by the guy who owns Fat Cat Racing. It's not a real thing.

[nextlvel]

That's because it's made up by the guy who owns Fat Cat Racing. It's not a real thing.

So is there no benefit to it ? I've heard it thrown around here and I'm curious if it is something I should be considering in dialing in my suspension. (80% street 20% mountain/autocross driving)

[heinzboehmer]

The process of picking spring rates based on ride frequencies is very much real science and is how basically all OEMs do it. Found this short paper that gives a pretty good overview of the science and math behind this concept: https://www.ijera.com/papers/vol9no3...3036064%20.pdf

The comment about a loer frequency providing more grip is especially interesting and I think is what usually confuses most people when first introduced to this (it's definitely was what least intuitive to me).

There's also a lot of formal textbooks that go into more detail concerning suspension design if anyone is interested in learning more.

[oceansize]

Before heinzboehmer posted I was about to type there is going to be a lot of comments from people who aren't engineers, don't know math, and haven't researched (and read the paper he posted). This is not something that's made up.

Whether or not you want to partake is optional of course but there is enough members here including Obioban running flat ride that it is a "real" possibility and worthy of some consideration.

[9kracing]

Straight from the article.

"However, the determination of the ride frequency is largely based on assumptions and is done by choosing a figure in the ball park range and hence, requires in depth study and analysis."

There are so many factors that go into ride frequency... ride height, swaybars, end links, suspension travel, spring rate, damper, etc. You can't just look at a spreadsheet and decide what frequency your shocks will be at.

People are free to do what they want, but the only time I've heard the term "flat ride" is from FCM. This isn't a widely talked about term in any automotive circle but here. Most people refer to unwanted oscillations as "the pogo effect"

[oceansize]

Straight from the article.

"However, the determination of the ride frequency is largely based on assumptions and is done by choosing a figure in the ball park range and hence, requires in depth study and analysis."

There are so many factors that go into ride frequency... ride height, swaybars, end links, suspension travel, spring rate, damper, etc. You can't just look at a spreadsheet and decide what frequency your shocks will be at.

People are free to do what they want, but the only time I've heard the term "flat ride" is from FCM. This isn't a widely talked about term in any automotive circle but here. Most people refer to unwanted oscillations as "the pogo effect"

Good adjustment, you said "That's because it's made up by the guy who owns Fat Cat Racing. It's not a real thing." which is completely incorrect. He didn't make it up, it isn't new, and there is theory behind it. It is correct that you must make a set of assumptions which I assume is the basis for his company i.e. lets get a ball park, then do real world testing and refine. Sounds like a good science to me.

[Kdubski]

Personally, I am thinking of KW V2 or KW V3 as an upgrade from stock as I become a better driver with ~5 track days a year.

[heinzboehmer]

Straight from the article.

"However, the determination of the ride frequency is largely based on assumptions and is done by choosing a figure in the ball park range and hence, requires in depth study and analysis."

There are so many factors that go into ride frequency... ride height, swaybars, end links, suspension travel, spring rate, damper, etc. You can't just look at a spreadsheet and decide what frequency your shocks will be at.

People are free to do what they want, but the only time I've heard the term "flat ride" is from FCM. This isn't a widely talked about term in any automotive circle but here. Most people refer to unwanted oscillations as "the pogo effect"

Pretty much any scientific process starts with a set of assumptions and builds on them. All I'm saying is that this should not be dismissed outright. It's based on real stuff and allows you to make an informed decision based on data, which is not the case for a set of coilovers picked out at random.

Also, that paper does mention the term "flat ride"

[cobra]

crazy statement to make especially when Porsches all have flat ride in OE specifications and in many of their aftermarket/racing setups

Porsches are often referenced as the holy grail and justification for why flat ride is good. I think we need to consider the entire vehicle, application, suspension geometries, and all the other compromises/requirements Porsche is taking into account and not just cherry pick the spring rates. At the most basic level, an E46 is not a rear engine vehicle with lots of aerodynamics and 325/255 stagger tires like a 911.
You could also say a pickup truck has flat ride because it's sprung more stiffly in the rear relative to the front. I don't think anyone has ever said a pickup truck rides particularly good.

That's because it's made up by the guy who owns Fat Cat Racing. It's not a real thing.

It's definitely not made up, the concept goes way back to early vehicles. The term "flat ride" is a marketing term you're right.

The process of picking spring rates based on ride frequencies is very much real science and is how basically all OEMs do it. Found this short paper that gives a pretty good overview of the science and math behind this concept: https://www.ijera.com/papers/vol9no3...3036064%20.pdf

The comment about a loer frequency providing more grip is especially interesting and I think is what usually confuses most people when first introduced to this (it's definitely was what least intuitive to me).

There's also a lot of formal textbooks that go into more detail concerning suspension design if anyone is interested in learning more.

If you consider the extreme cases - go stiff enough on your springs and you have a rigid vehicle, which relies 100% on the tires and chassis for compliance. The goal from a grip standpoint is to reduce tire load variation. Too soft on springs, and you lose the handling response which is more of a driver confidence thing. So it becomes a compromise that depends on the driver.

[Obioban]

Everyone single OE vehicle I know of comes stock with “flat ride”— term used or not. From luxury cruisers to pickup trucks to hardcore sports cars, I haven’t seen nothing that doesn’t come with it stock.

... if you wanted to find something that doesn't have it stock, I'd look to heavy aero cars, where they can't. I would actually be shocked if there is a car that doesn't have it, stock, without aero forcing them off of it.

Straight from the article.

"However, the determination of the ride frequency is largely based on assumptions and is done by choosing a figure in the ball park range and hence, requires in depth study and analysis."

There are so many factors that go into ride frequency... ride height, swaybars, end links, suspension travel, spring rate, damper, etc. You can't just look at a spreadsheet and decide what frequency your shocks will be at.

People are free to do what they want, but the only time I've heard the term "flat ride" is from FCM. This isn't a widely talked about term in any automotive circle but here. Most people refer to unwanted oscillations as "the pogo effect"

Frequency is a factor of:
spring rate
motion ratios
corner weights

That's it. Super easy to plug into a spread sheet and determine.

I don't know what you mean by "You can't just look at a spreadsheet and decide what frequency your shocks will be at"-- never heard of a shock frequency.