I was wondering if someone could shed some light on this.
The Koni Yellow shocks that are available for the RX-7 are considered one of the best for performance applications.
However, why are the Koni shocks only rebound adjustable out of the box, whereas shocks such as the KYB and Tokico are single adjustable with BOTH rebound and compression?

if anything i would think compression adjustability would be more important, but maybe i am mistaken.

 

That's just the way they are made?

It actually takes a more complex and expensive mechanism to adjust the rebound only while leaving compression alone. A single mechanism that changes both at the same time is actually simpler.

 

is there a reason why rebound adjustability is more favoured over compression?

i personally think that changing both at the same time is too much of a compromise, however i was always under the assumption that you usually don't need to play around with rebound too much, but compression is very dependent on spring rates. does this mean that the Koni shocks work best with a fairly specific spring rate?

 

Why do you need to adjust compression on the damper?
Unless you're do serious racing, it really doesn't matter.
If you've seen shock dyno graphs, the compression damping changes are very small compared to rebound.

There are shops that will convert the Koni yellows to double adjustable, but are you willing to pay like ~$500 per corner for this conversion?


-Ted

 

so you are saying that rebound adjustability is a much larger factor in suspension tuning?
i know you can convert the Konis to double adjustable, as well as get them revalved. i don't think my car is ever going to be more than a weekend racer, so i do not think i need that at this point.

my question was simply for knowledge sake, and maybe also to see why Koni designed ONLY rebound adjustability rather than only compression or both. from what i've heard so far, it is better to have seperate rebound and compression adjustability rather than both at the same time? is this one reason to choose the Koni shocks over others?

i've always thought of compression as controlling mainly the initial response of the suspension and things like steering response and other "handling" aspects, while rebound affects how the car reacts to the result of car/body movement.
it would seem that compression adjustment is a more performance oriented feature, while rebound could be said to be a greater factor in adjusting the car for various road conditions (i.e. ride comfort).

and does anyone have an idea on what spring rate works best with the Koni Yellow compression valving? since it's fixed i would imagine there is a certain range that works best.

 

The Konis are designed to work with the stock spring rates or close to it. IMO, they do not control stiffer springs well unless you have them set stiff enough to rattle your teeth.

The rebound being adjustable and the compression fixed leads to poorer ride quality IMO. My new Zeals with very stiff springs -- 600 lb-in up front -- ride just as well as my progressive-rate 400 lb-in springs with Konis did over most surfaces. On really bad bumps, the ride is worse, on some surfaces the ride is actually better! The ride control is excellent, even with the dampers set to the softest setting. The car felt great on the winding backroad this weekend -- until I hit a large rock...
Since every other adjustable damper on the market changes both compression and rebound, I think Koni should take a closer look at how they do things. Don't get me wrong, I think the Konis are great shocks for the money. It's just that I think you can do better with more money...

 

No, I didn't say that.
The damper's primary responsibility is to dampen the oscillation from the compression of the spring.
Thus, rebound is it's major responsibility.
The spring is the primary component to tune compression, thus, the majority of dampers are not designed to affect compression characteristics.
This was a tangent in another thread in the Race Car section.


-Ted

 

The point of adjustable dampers is to allow you to adjust how the chassis (the sprung weight) responds to inputs (from the driver or the surface) that make it transition. If all the shock needed to do was damp the spring and keep the car from floating like a boat we'd all be running $19.99 shocks from Autozone rather than highly specialized adjustable dampers on our performance cars. Yes shocks damp spring oscillations, but what they really do is allow you to tune the chassis.

A damper needs tremendously more rebound damping than bump (compression) damping. The reason is simple. In rebound the damper must control the entire sprung weight of the car because that's the part trying to heave around. In compression the damper merely needs to control the unsprung portion of the suspension. Why do Koni yellows only have rebound adjustment? Because the rebound is what controls the chassis and therefore has by far the largest influence on handling.

The problem is that shocks which change both compression and rebound at once (the Tokico for instance) adjust both the compression and rebound at the same time so the ratio between the two is fixed. In this case you can't get more rebound without also getting more compression. Once the compression is right you really don't need to monkey with it because all the compression does is control the unsprung weight of the car, what we'd really like to do is adjust rebound so we can tailor the way the chassis acts to a given track or driver. Too much compression causes the tire to patter and bounce over bumps. Our unsprung weight doesn't ever change but we want to be able to adjust how our sprung weight reacts to transition and this demands adjustable rebound damping. Unfortunately a shock that changed both at once forces us to be stuck with more compression we don't want or need when all we want is more rebound. The Koni on the other hand even though its compression damping is fixed allows us to adjust the ratio of compression vs rebound.

The Koni does not force you to live with the compromise of shocks which adjust both at the same time but they have to spend more money to give it to you.

 

I agree with most that is being stated here, I think that you guys are missing a critical point with shock tuning. When you pay to have Koni's made double adjustable, the compression and rebound are de-coupled and this allows you to tune the shock damping capability to suit the action you are expecting it to control.

On my car I have run 3 different types of shocks, Koni Yellows, Bilstein Competition and old style KYB Adjustables. They each have had advantages and disadvantages that may or may not relate to this discussion. The primary concern you should be considering is the anticipated usage. I have found that the Single adjustable Koni's (stock valved to dampen up to 500 lb springs) worked well in controlling the rear of the car as the stock compression damping allowed a fair amount of squat. At the front it was substantially too much dive under braking. I increased spring rate to control it, but it was really a sledgehammer approach and I needed better shock control. Secondary issues with the Koni's was as you increase rebound damping control the car has a tendancy to "jack down" through a series of high speed sweepers to the point that my exhaust would scrap the ground unless I backed off on the rebound damping. They also had a tendancy to fade after about 30 minutes and I did get some front strut shaft flex.

The Bilsteins worked great in the dry. No issues with porposing/ bobbing and they never ever faded. I could also increase spring rates up to 650 lbs and the shocks would handle it. Main concern was lack of adjustment to suit different track conditions, i.e. rain, cold, dust. No concerns at all and dead simple to run.

The KYB's were a good street shock with similar issues as the Koni's, just not as durable.

What you need to set up your car correctly is independent slow speed compression and rebound and separate high speed compression ( to allow pounding curbs without bouncing the car to the moon). I have run another car on Double Adjustable Koni's and the mega buck Penske's on the same weekend on the same track. The increased sophistication in wheel control with the Penske's and their ultra adjustability transformed the car. It went 2 seconds a lap faster with increased grip under acceleration and braking. There were no other changes.

So what am I running now? I run the Koni's on the rear for some adjustability, recognizing limitations with fade and jacking and the Bilsteins on the front again recognizing non-adjustability limitations. I am saving up for some really good shocks as I believe that I can gain another couple of seconds with better wheel control.

Most of you don't really have to worry about races that last 3 hours and bouncing over curbs at 50 mph and having to race in the rain at 45 degrees. I do and really really want the flexibility of control offered by the mega $$$$ shocks.

If It was me I would buy the yellow Koni's and run them until their limitations became apparent as they are very high quality and very durable. Then save up for some Motons/ JFZ's/ Penske's/ Full Race Koni's etc....

 

The idea of first finding the limitation has been key for me in every aspect of any car, but especially suspension. Too many people are oblivious to that step, they set about "improving" by spending money and swapping parts yet still have no understanding of what it is they are changing.

If I don't know the exact problem I want solved and I don't fully understand how the new part will alter or perhaps solve that problem than I haven't done anything but create an entirely new set of problems which I still don't understand. It doesn't get you anywhere. It's funny to me. People will spout all day long about how the car is "better" when in reality they don't sense "better" because they don't know what better is. They only sense "different". To me those are two completely dissimilar things.

To be sure this is true of any shock anytime you have too much rebound in it and is the classic sign of knowing you've got too much rebound

 

Damon, I know we agree about rebound damping and jacking down but it feels so much better when you get rid of the bobbing by increasing rebound damping.

Nothing upsets the driver (me) more than having the car nodding at the front and oscillating at the back pulling 1+g's in a 110 mph corner. You know you just don't feel confident enough to really lean on it.

 

^ You feel that's mostly from the fact that your mixing the Bilsteins and the Konis on the front and rear, or is that just the lesser of other evils as you setup the car?

 

I am using Bilsteins on the front and Koni's on the rear because that was the best solution after testing, the lesser of evils. It started bobbing only on the full set of Koni's due to lack of supple/ low speed damping. When I screwed down the rebound on the Koni's the car became too stiff and started pattering and nodding - a classic problem. It was too hard to hit the sweet spot for a whole circuit. I could improve things in one section but loose more overall in other sections.

The Bilsteins were more supple and dampened the spring rates better and thats why they went on. The problem with the Bilsteins is their lack of adjustment which prevents me from optimizing the car to different conditions and tracks.

On a clean dry and warm track the Bilsteins work great. I really need the multi function 4 ways to really get the car right and maximize performance. As an example you can see on the in-car that I need to lift going over the crest of the hill going into Turn 2 at Mosport. The people I am racing with do the same but can get on the gas at least 1 second faster while I wait for the car to settle down.

Just need some mucho $$$$ shocks. I am at the limit of what I have

 

lots of good info guys, thanks. i always like hearing from people who actually have real world experience.


close to stock spring rates work best? i have heard conflicting opinions that have said otherwise.
although it might make sense if the compression is not valved very agressive. 23Racer mentioned the Konis stock valving are good up to 500lb springs?

i definetly agree about fully understanding what you are doing before doing it. that's why i started this tread in the first place.
i will say, however, that i feel my driving skills are not yet at the point that i am being held back by the stock setup. i don't think i have yet found the "limit" of the stock suspension, but it's hard to say because as much as i still need to learn, an aftermarket setup may actually teach me more. i can definetly say that i've gone OVER the limits of the stock suspension . guess that's what happens when you mix r-comps with bad driving skills, heh.
anyways, i'll probably do a few more autocross sessions on the stock suspension, but at this point i really want to spend some money on suspension. is it wrong to do this even though i haven't "reached the limit" of the stock suspension? i don't think so.

another thing i was wondering about:
is it worth it to spend the money to get the Konis revalved? i assume you get compression revalved? i am thinking that, if you have a fairly specific spring rate and application then you can get a particular compression valving that could work quite well.

 

Depends. If you're already improving and beginning to understand yourself it's not too early. Konis were the first mod to my suspension and they actually made the car easier to drive IMO. Don't do too much at once though. Take the time to play with each mod and see how it changes the car. Also realize you as the driver have to change in order to take full advantage of the car as it evolves. I remember my first run with the Tripoint front bar when I pushed out in the first corner and damn near took out everything. My first thoughts were "What the hell is wrong? This is supposed to be better!" It was better, I just didn't know how to drive it to make it better. It took a little while.

You can make a change to the car and make the car potentially faster but often this also requires the driver adjusting himself as well. If the driver is too stubborn to change (you'd be surprised how often this is true) he finds no additional speed and doesn't benefit. That's the big bug-a-boo. You have to understand as you change the car what it does better and what it does worse and drive the car to its strengths. What the car's strengths are change everytime you change the car.


Tough question to say if it's worth it as opposed to buying something else that's more custom. At that point you're getting into very specific individual cases. IMO though you're a long ways away from even concerning yourself with what the valving is. Your goals right now should be drive, drive, drive.

 

Why? In a word? Pricepoint.

You can actually send your Koni Yellows back to Truchoice, and they'll make em double adjustable for you... but it'll cost you. Most all true double adjustable shocks cost more. Like Tokico, Koni was trying to offer the most needed features, while eliminating others and keeping them sited to the way most people will use them (as a stock replacement with either stock or aftermarket lowering springs), to keep 'em around $125/shock.

 

Absolutely right Damon. There is far more time in the driver than in mods at this point. Coldfire, I would take the $500 bucks that you are going to have to spend on revalving the shocks and spend it on AutoX and lapping days.

With my 20 years of experience on track, I have the ability to jump in most any car and drive it very very quickly.

In fact 2 years ago I jumped in a bone stock Miata and turned a 1:49 at Mosport with a passenger. Most fun I had experienced in a while, but backed it down after bunny hopping through 2 as the chassis started to flex. I have included a shot from that day. My buddy was driving my RX7 and struggling to keep up, while my crewchief was in the passenger seat with a stop watch. That is why he had his head down (he really wasn't about to throw up, honest).

Experience is key to going fast.

DamonB, it is too bad we are 3,000 miles apart as I really appreciate your approach and knowledge level and would love to bounce ideas off you. The closest I get to Dallas is Northern Cali, with the Cobra R (photo attached). The RX stays pretty close to home.

 

I appreciate the compliment. I've thought many times we need to organize an un-official invitation type meet with all the track dogs. Problem is anywhere we'd meet is probably a thousand miles from here

 

thanks for the comments guys, i appreciate it.
looks like i will be going with the stock valved Konis with some ground control coilovers in due time. seems the best way to spend my money for suspension considering my needs.

23Racer, you are totally right about taking that $500 and spending it on the fees, gas, etc. required for track days/auto-x.

Damon, you make a good point about not changing too much at one time, however sometimes it saves time and money to do things all at once. i was going to put in the Koni shocks first, then get the GC coilovers, then the GC camber/caster plates, then put in a larger front sway bar, then change all the bushings...but doing it all at once when is a lot less time. even though being able to experience what each component does is a big incentive...between work, engineering undergrad, and FSAE duties, i still want time to actualy drive the car.

 

That only applies to things you're adjusting and trying to come to grips with. If stuff is worn out by all means replace it all at once. My first rule is always to get the car in good stock shape first. If all the bushings are shot there's no reason to buy shocks until you've done that first. No sense in modding the car if you don't already have it in nice shape to start.

Which FSAE team? The UT Arlington team is local so I've got to watch them run their cars at local events for years.

 

koni yellow twintubes adjust rebound in the piston using orifice which can be accessed using the shaft, comrpession damping is adjusted through the footvalve located at the bottom of the shock, to adjust compression they have to modify it to allow access to the footvalve.

I think it's a bad idea to adjust comp and rebound together, sometimes you need to adjust the rebound and compression in the opposite direction. But the kyb and tokicos have so little adjustment range, it doesn't really matter anyhow.

 

my car doesn't seem to exhibit any issues related to worn bushings, at least none that i can notice. half of it is the performance aspect of replacing the stock ones with low compliance ones, but i only imagine that by now the stock bushings really should be replaced, regardless of condition.

i'm on the University of Ottawa FSAE team. it's the first year for this particular team and our school has actually never competed in an official FSAE event, so lots of work needs to be done. should be fun though once we start putting our designs to application.