The Strut thread - Koni / Illumina / Tokico / Carrera / Bilstein / Ground Control

[JMortensen]

I've been running 200/250 for 8 years on Illuminas, daily driver, about 5 years autox and some track days. I blew one front, but that was on the big track after repeatedly driving over one of the curbs. Oops. Other than that one the rest have held up fine.

 

I'm really looking to go much heavier on the springs since I'll finally be trailering to events, so thanks for all that Bilstein info Katman.

[katman]

Katman you are tough on shocks and I respect that. However, I know of EP racers that placed well at the runoffs and national level FP autocrossers that run the GC's and speak highly of them. Although they did recommend a rebuild each season and admit price was factor in buying them. I suspect "junk" to you would still satisfy a strong regional competitor?

 

Hey, we won an ARRC in ITS with shocks that didn't cost us $200, for all four! Talk about junk! So yeah, you can be competitive with all sorts of shocks. I call everything that isn't on my race car junk.

 

My biggest problem with GC's was in a BMW app. I wanted them to work, everybody else in the class (ITS) was using them, and I love Jay's hardware. I was willing to write off our bad experience with them on the 240 as "we were just spoiled with the ShockTek's and didn't spend enough time with the GC's to get them to work". However, after 2 seasons of changing every possible thing ('cept GC's Advanced Design shock) on the BMW's and having both driver's always claim that the only way you could tell you were losing the back end was if you were looking out the side window, and the only way you could tell you were understeering was if you ran out of steering lock, I made a wholesale swap to Bilstein and proceeded to win the last 2 ARRC's. Went from scary cars with no feel to what a Bimmer should feel like- a blast to drive. I actually have two cars set up with radically different spring rates and two different Bilstein shocks and they both rock.

 

All my former Koni friends always complained about the upper bushing wearing out prematurely, and Truechoice hammers you on the rebuilds. Otherwise I like them.

 

We used to race Tokico but they don't really support racing so eventually our spring rates on the Z's outgrew their off-the-shelf parts, but I'd use them again on a street car. Bilsteins just seem to last, they're rebuildable and revalveable, and don't cost as much as Koni's.

[clarkspeed]

Good stuff here. Thanks guys. This explains a lot. I tend to view shock tuning as one of the last things to optimize when setting up. Trouble is too many other things get in the way of focusing on that aspect. I am getting better though. I am trying to focus more on what the car is doing and how it feels rather than just getting through the turn. You never stop learning.

[260DET]

No doubt Bilsteins are very durable, a mate of mine does targa events in his 240, which involve several days high speed driving over temporarily closed often rough sealed public roads. In that sort of use Bilsteins will outlast and probably outperform Konis.

 

But the problem with Bilsteins for road and circuit work is that they can't be adjusted to take account of different conditions or changes to the car.

[heavy85]

Ditto what others have already said - this is great info. I think I'm going to stay with the Illuminas based on the conversation here. I already have the BZ3038s on every corner and from what I can guess they were probably installed around 1991 by a previous owner. When I got the car it had 500 lb/in springs (scary on the street 'cause it tended to skip around) and NO bumpstops. I put on the 225/250 springs and bumpstops at which time I noticed the rods on all the struts were blued in a small range of travel. jmortensen has said this discoloring is normal so how do I tell if the struts are good or not? The spherical bearings in the camber plated were also all siezed to the top of the struts. I ended up having to cut the bearings off after trying several other methods (gear puller, hammer, larger hammer, etc) - so my point is the threaded top end of the struts are no longer the straightest anymore but I can still tighten down the nut. Dont know if this matters but it bugs me. The rears have a fairly long spacer under them, maybe a couple inches long, and the fronts only have a single washer as a spacer. Anyone know the part numbers of the struts to use when I section the housings? Finally, I assume you use shorter ones on the front or due you use shorter ones all around and keep the longer spacers in the rear?

 

Thanks again

Cameron

[JMortensen]

BZ3099 is what I used in the front. That is a rear 88 MR2 strut. Then I used the 240 front strut in the back, but I don't have the number for that one.

 

When my strut blew it looked like someone took a squirt gun full of shock oil and sprayed it all over the inside of the fenderwell. If you have the struts out the way to check them is to compress them and extend them and feel for "dead spots" on my Tokico that blew you could compress it all the way then pull on the strut when it was compressed and it would pull up about an inch and a half with NO resistance, then it felt normal again. The bluing on the shaft is not an indication of a bad strut, but the ones that were blued on my car also had the paint bubbling off, so they did get HOT.

 

Some people bend the top of the strut for camber. Sounds like yours might have been bent on purpose. I have a friend who had a local suspension shop do that for her, so I don't think it's uncommon at all. I honestly don't know how they do it with anything like accuracy, but it might be that this is the reason why your struts are all bent at the top.

 

EDIT--You can get all the same struts and then put a spacer in the back if you want.

[johnc]

Keith,

 

You guys really ran 500 lb. in. front springs on the EP cars? Really? Bumps were not a problem?

[mom'sZ]

Katman: How did it come to light that the Konis had worn out their upper bushings? Did their performance drop off noticably on the track or were they removed from the car and inspected and found to be bad? In other words, how could you tell they were bad? I think I remember you saying it wasn't just one strut or one set, that you tried several and they went bad. Elaberate please

 

thank you

[katman]

Katman: How did it come to light that the Konis had worn out their upper bushings? Did their performance drop off noticably on the track or were they removed from the car and inspected and found to be bad? In other words' date=' how could you tell they were bad? I think I remember you saying it wasn't just one strut or one set, that you tried several and they went bad. Elaberate please

 

thank you[/quote']

The shaft gets wobbly in the body so camber and toe were not controlled.

[katman]

Keith' date='

 

You guys really ran 500 lb. in. front springs on the EP cars? Really? Bumps were not a problem?[/quote']

I'll recheck my notes...

[Pop N Wood]

Maybe he was using those double secret drop tube dampers.....

[Mikelly]

There is so much good info and part numbers, that this thread qualifies for a "sticky".

 

Keep the tech info coming guys... This one will be around for some time.

Mike

[Guest nitr0]

katman did you try a polyurethane upper bushing kit or solid strut top with the Koni? I've got Koni's (not in yet) F + R and will probably only run soft springs in a coilover, but they will get alot of abuse on the street. I trust the Koni name but every car works different and i'm open to suggestions.

[Mikelly]

I believe the bushing Katman is refering to is the one inside the strut tube insert housing. Not the bushings on the tophat assembly you would traditionally associate with "bushing" kits for the street.

 

In road course "stuff", the energy transfer and heat are significant enough in most applications that is isn't uncommon to heatsoak shocks and struts, which is why any series that allows external dampers (Ohlins and Penskys) does just that.

 

This is also the same reason you read here that we tell people not to run cross drilled rotors, then go to ALMS or other professional racing series and see... Cross drilling on the rotors. Big budgets and special treatments allowed for in professional (And more and more amature) racing does not translate well to the street.

 

You'll be fine with Konis or Tokicos on the street. You'll never abuse them the way 30 minute road course session will... Nothing hurts suspension and brake parts like doing road course laps.

 

Mike

[Guest nitr0]

Thats actually what i first thought but dismissed it because - its a Koni, they shouldnt do that..... Another question, what condition were the valves in? and were the Koni's gas charged?

 

The stock Koni's for the 240/260 (86-1811 -F and 86-1812-R i think) are not gas charged so will heat up quicker, and are designed to work at the cars standard height, they are part of the classic range. At 25-35mm (1 to 1-1/4 inch) lowered, the struts are working at their lowest safe range, any more than 35mm even in a street application the travel is too much and the shock will bottom out...

 

People here in Australia are using Z31 300zx inserts Front and Rear with great results on the track, they are gas charged and externally adjustable, and are also about 35mm (1-1/4 inch?) shorter than the 240/260z inserts so will work properly with lowered cars.

[tube80z]

All my former Koni friends always complained about the upper bushing wearing out prematurely, and Truechoice hammers you on the rebuilds. Otherwise I like them.

 

Is it possible to install a linear bearing instead of a bushing?

 

Cary

[katman]

Like MKelly said it's the shaft bushing inside the shock body. I don't know what Koni might be able to substitute. It is possible they no longer have that problem, its been several years since I knew anybody intimately familiar with them on a Z. I agree with everything else he said as well.

[johnc]

Koni (and other) shock bushing failure is almost always cased by only a couple things:

 

1. Bent shock shaft.

2. Binding in the normal articulation of the strut.

 

For this discussion we'll ignore number 1.

 

The strut/shock combination is designed to primarly take vertical loads. Inherent in the design of a strut are some lateral or bending loads but they are not as great as most people think. ANY lateral or bending load increases the bind in the movment of the shock shaft and is a bad thing.

 

Because the length of the strut/shock assembly and the angles of the strut in relation to the vehicle and the LCAs change as load changes, the front and rear strut installations on the 240Z need to have free movement at the top and bottom of the strut. The freer the better because these are the places when most of the suspension bind occurs. If this articulation is restricted then the side loads on the shock bushing increase dramatically.

 

If shock bushings are wearing out prematurely then I would check for binding in the ball joint/steering arm (or the spindle pin at the rear) and at the upper strut mount. A classic failure example was (is?) the Polyurethane OEM upper spring isolator that MSA sold (sells?). The stiffness of the poly restricted articulation at the upper strut mount and it would destroy shocks very quickly. A lot of Tokico Illuminas were killed with this "performance" part. Another example was GC's camber plates from about 10 years ago. They used monoballs without much articulation and these would bottom out near maximum compression, causing bind.

 

Other contributing factors can be (very, very vehicle specific):

 

1. Rear toe-in beyond about 1/8".

2. Really big caster numbers in front (8+).

3. Shortened TC rods (TC rod pivot moved forward).

4. Excessively shortened steering arms that bind up the tie rod end.

[johnc]

A friend reminded me of trait of the Koni 8610 (and I think 8611) inserts that I had forgotten about. The upper bushing/seal is crimped in place with three tabs off the housing itself. The bushing/seal is not a tight fit and can feel loose/sloppy. Its designed that way by Koni and everything tightens up fine when the gland nut is torqued to spec. If the gland nut loosens at all then the bushing/seal gets a little bit sloppy. Also, the Koni shock oil is only good for 2 years of monthly racing. Upgrading to Silkolene will give 4 years of racing before the oil needs replacing.

[260DET]

'Bump steer' spacers increase cornering force leverage exerted by the wheel on the strut, the bigger the spacer the more leverage. Don't know if that makes an appreciable difference to shock shaft wear and binding but it could.