Coilovers

I'd like to ask your advice on some coilovers I'm ordering next week. This is the only big budget item that's going on my car, at least this year, and I want to get it right the first time around.

The intended usage is a Daewoo Nubira that will see track time. Nubira's have four wheel strut suspension, so the motion ratio should be in the neighborhood of 1. The car will weigh about 2600 lbs with me in it when it hits the track this year. I'm running 195/55/15 street tires right now, but I'm looking to get some track cast off R compounds. I probably can't afford adjustable valving, but since Nubiras are weird, the company has to custom make them anyway.

Since the track I'm going to run is pretty bumpy all over and particularly bumpy on the fast sweeper leading to the front straight, I was thinking of asking for them to use the stiffer shock valving for something a little bigger, like a Sonata or Genesis Coupe, in conjunction with spring rates used on something lighter, like an Accent, like 350/250 lb inch. I don't plan to drop the car any more than an inch and a half. Is this a good plan?

I've never done this before, so please tell me if I'm being stupid. Thanks.

Sounds like the valving will likely be overdamped for the spring rates. The softer rates may help over the rough stuff, I'm not sure the stiffer valving is going to do the same.

I'd tell your coilover builders your intended track and your experience there and let them make an informed suggestion. IMHO, no matter what you decide, I'd expect to play around with the spring rates after-the-fact if you're really trying to be competitive. I can't imagine there's a common, proven setup for Nubiras, so you're in relative unknown territory. Even with well calculated spring rates, real-world testing usually changes the numbers by a bit.

What happens when a car is overdamped? I honestly don't know. The idea there actually came from fiddling on Forza III.

I don't want to entrust my suspension guys to recommend a setup because I've seen their racecars and they like to run really, really stiff and really low. Like almost skipping into the air on that bumpy sweeper stiff.

Mike K. from MotoIQ has a great 4-part series on suspension that I'd recommend:

http://www.motoiq.com/MagazineArticles/tabid/59/articleType/ArticleView/articleId/1424/The-Ultimate-guide-to-Suspension-and-Handling-Part-1-Wheels-and-Tires.aspx

http://www.motoiq.com/magazine_articles/articletype/articleview/articleid/1491/the-ultimate-guide-to-suspension-and-handling-part-2-controlling-body-motion.aspx

http://www.motoiq.com/magazine_articles/articletype/articleview/articleid/1595/the-ultimate-guide-to-suspension-and-handling-part-3-balance-the-chassis.aspx

http://www.motoiq.com/magazine_articles/articletype/articleview/articleid/1650/the-ultimate-guide-to-suspension-and-handling-part-4-reduce-weight-transfer.aspx

I actually just read those earlier today.

get Koni's, they custom valve their race shocks to your spring rates and the single adjustables are around $200. Adjusting is easy, just take a pocket screwdriver and turn the nob. If the car is FWD (?) make the front all the way soft, and the rear all the stiff.

Steve

overdamped valving will tend to render the springs less usefull as the strut wont compress fast enough for the spring to help much. My completely non-experienced gut is telling me this may be a case for progressive springs and a slightly taller ride height (which you already mentioned you werent interested in dumping the car so youre good there).

MrBenjamonkey wrote: Since the track I'm going to run is pretty bumpy all over and particularly bumpy on the fast sweeper leading to the front straight, I was thinking of asking for them to use the stiffer shock valving. Is this a good plan?

That's a terrible plan. You want the suspension to be compliant, especially over rough surfaces.

The shock handles all of the compliance, even with stiffer springs. Correct valving will accomodate this.

@ Steven Konis are hard to come by in Korea, or at least I haven't seen them. I'm looking at either super expensive Tiens or cheaper SuspensionTechnique parts.

@ 4cylfury Do you think it would be wise if I asked for a shock with softer bound and stiffer rebound?

I should probably also point out that I like to use curbs. I can change that, obviously, but I do like a car that's soft enough I can rotate it using the curbing.

MCarp22 wrote:

MrBenjamonkey wrote: Since the track I'm going to run is pretty bumpy all over and particularly bumpy on the fast sweeper leading to the front straight, I was thinking of asking for them to use the stiffer shock valving. Is this a good plan?

That's a terrible plan. You want the suspension to be compliant, especially over rough surfaces. The shock handles all of the compliance, even with stiffer springs. Correct valving will accomodate this.

So I should just tell them I want to be a little taller and softer than a normal race application?

Probably is nto a bad idea, but then again, I like the suggestion of just telling the shop where it is you are going to be running and see if they have a recommendation. Im not a professional, I just play one on the webs (I read a few books...Im faaaaar from proficient )

I know what you're saying. It's just that motorsports are relatively new in Korea and, well, watch this.

http://www.youtube.com/watch?v=etTqJAn-MAg&feature=related

The only racing shop in my city setup that car's suspension.

MrBenjamonkey wrote: Konis are hard to come by in Korea, or at least I haven't seen them. I'm looking at either super expensive Tiens or cheaper SuspensionTechnique parts.

Hmmm, I don't really know the situation with trying to source parts from Korea, or anywhere else in Asia for that matter. However, if you're already having a custom setup created for you it probably isn't cheap. I'm assuming at least custom housings must be built. What's your budget? What brand and type of damper internals are they proposing? Depending on how much you've set aside for this, you might be able to go with a more experienced overseas shop that can ship to you. Just a thought.

MrBenjamonkey wrote: Do you think it would be wise if I asked for a shock with softer bound and stiffer rebound?

A lot of modern dampers are already valved this way. IMHO perhaps too much. Having a relatively stiff rebound can make the car feel more controlled. However if overdone it can cause a jacking-down effect (especially over said bumps) reducing your travel, sometimes all the way down to the bumpstops. (can anyone say infinite spring rate?). In other words, for your situation I wouldn't make that your driving idea behind the valving.

MrBenjamonkey wrote: I should probably also point out that I like to use curbs. I can change that, obviously, but I do like a car that's soft enough I can rotate it using the curbing.

I think all the more reason to have your valving matched to your spring rates. This is a good example of when you don't want excessive rebound damping. After the suspension compresses to absorb that curb, you want the tire back on the ground asap.

If you're only option is this shop, I'd ask them for a relatively soft middle-of-the-road setup. Once you start making the adjustments to the extreme ends of the spectrum, any performance gained is usually lost somewhere else. It sounds like you need a forgiving setup that will see a lot of different surfaces and rough hits.

Personally, I'm a fan of the rear-stiff setup for most fwd cars. Minimal anti-rollbar up front and just enough out back to compliment the rear rates (although big ARBs on the back usually work pretty good).

disclaimer - I am also not a pro at this kind of thing. Just a bookworm, armchair physics hack, and amateur autocrosser.

If its bumpy, I'd like to say you'll need softer suspension and as much wheel travel as possible.

two thoughts with a question:

1) if it's that bumpy, have you looked into anyone doing any rally stuff in the area? a tarmac stage type setup or someone familiar with setting a car up for one could be another angle for research.

2) have you looked into adding a sleeve style coilover and higher end strut insert (hopefully something double adjustable) instead? the question part is if you trust a shop nearby to weld on new perches, you might be able to cut the strut housing down and gain some extra travel to work with. just some off the top of my head thoughts, i don't know if the design of your stock suspension lends itself to this.

<- also just an amateur autoxer and interdork so don't forget the salt.