Midtenn

iTrader: (15)

I've got a set of Koni's Sports I need to have rebuilt. I know I can send them Koni to have them rebuilt. I've also found a few other place (ProParts and TriPoint) also rebuild them. I just wanted to see if anyone knew of other companies that rebuilt them. Thanks.

Jfornachon

iTrader: (23)

Just an FYI pro partaking is the place to send them if you do have them rebuilt by them. As tri-point is in the service aspect of the cars. Call Jeff and let him know I referred you.

Have a great day,
Jared

curly

iTrader: (25)

Anyone have a guesstimate as to price per shock?

Midtenn

iTrader: (15)

ProParts lists $115 per damper + parts. I am just shopping around to save a little bottom line.

chpmnsws6

iTrader: (12)

Holy smokes, that getting to Bilstein territory

wannafbody

iTrader: (1)

That's almost the price of a new Koni sport.

Midtenn

iTrader: (15)

But much cheaper than a Koni Race damper.

Thucydides

Yeah, but the OP said he's got Sports, so I'm not seeing the economics of rebuilding them either. $115 + parts versus $128 new.

http://www.good-win-racing.com/Mazda...t/20-1104.html

It's also my understanding that most of the companies who rebuild Koni's don't have a way to pressurize them afterward. If they're not pressurized the shock fluid will cavitate, and the damping will be very inconsistent. If the re-builder says they handle this with a heavier fluid, shop somewhere else or bite the bullet and purchase a new set for a few bucks more.

hustler

iTrader: (6)

Who is servicing shocks without a nitrogen tank?

webby459

iTrader: (8)

Truechoice does them as well. I have ONE shock that was done by Truechoice, no endorsement either way.

I've gotta say I've spoken to lots of these guys and given the short chat I've had with TriPoint (or ProParts USA as Jared says), TriPoint seems to be a quality outfit. Also given the fact that Guy Ankeny uses their parts and recommends them for their pillow ball mounts and stuff, I trust them.

Koni themselves seem approachable and receptive to motorsports, but back in late Spring their lead time was like 10 weeks, ymmv.

C. Ludwig

Do a search for "degas" and you'll see why they're sometimes built this way.

If you're not having any custom work done to alter the shock I'd just buy new myself. By the time you pay two way shipping and wait a couple weeks, you're in no way ahead of the game.

I've had good luck with Truechoice for custom work. Pricing is lower than Koni-USA and turnaround is usually in the two week range. Wouldn't hesitate to use Tri-Point/Pro-Parts if I were on the west coast.

Thucydides

I did a search as you've suggested, and got zilch, here and on Google.

But I think I know why they're done this way. If you've ever seen twin tube shocks pressurized at the factory, it's done by injecting pressurized gas (probably nitrogen) with a tool that both introduces the gas and welds shut the hole the gas is injected through as the tool is withdrawn. Your typical race shop doesn't have this type of sophisticated and expensive machinery, and so they make do with a higher viscosity fluid to compensate in some measure for cavitation of the fluid. It may work to a degree, but it's not the optimum solution. If you've ever seen a dyno graph of a shock that's cavitating, you'll not want a "degased" shock. Here's a video that shows cavitation in a monotube shock:

http://www.roehrigengineering.com/Do...ear_shock1.wmv

The problem is the shock fluid becomes filled with tiny bubbles, and the properties change dramatically and not for the better. A pressurized shock minimizes cavitation by keeping the fluid above it's vapor pressure threshold, and so the shock remains consistent and predictable over a wide range of conditions.

Some more good reading:

http://www.roehrigengineering.com/Te...0Balancing.pdf

wannafbody

iTrader: (1)

Here's another one

http://www.youtube.com/watch?v=W4ZZYqRVzLc

Thucydides

And one final video from the TV series, "How It's Made":

Scroll to the bottom of page and you'll find the video showing the entire process of how a twin tube shock absorber is made, including how they pressurize it.

http://science.discovery.com/videos/how-its-made/

Besides being a mono-tube shock, Bilstein's differ by having their body tubes extruded rather than welded, resulting in a stronger and more precisely formed pressure tube.

C. Ludwig

Guess Youtube hasn't built all the de-gassed shocks that have won so many autocross and road race events.

chpmnsws6

iTrader: (12)

Bilsteins don't leak after 3 years and 8k miles of operation like these Koni's are :(

Thucydides

Great! I'm all ears. What autocross and road race events, and what's going on with de-gassed shocks that makes them work so well?

Actually, don't bother; I did find something about de-gased shocks. Here's what Dennis Grant has to say about it:

Degassing Shocks

Amongst some people, the hot ticket is to take gas-pressurized shocks, and degass them. The idea being that, with less gas pressure, the car sits a little lower and that lowers the CG height.

Well it does lower the CG height - but it also takes away the little bit of extra spring rate that the gas pressure adds, and worse, it exposes the shock to cavitation....

....Yes, you lowered the CG of the car - but the shock stopped working too.

NOT a good idea - especially on a Stock-class car. In a Stock car, you really should go the other way, and pressurize the shock as much as possible to get more spring in the car. (Interestingly, the NASCAR teams use the same trick on tracks that have spec springs).

.....

A degassed shock cavitates at a very slow speed, and once it starts cavitating, all kinds of crazy crap starts to happen. Cavitation is Bad. Cavitation is Not Your Friend. Cavitation must be avoided at all costs, damn the ride height and full speed ahead. A slightly taller car with functional shocks will be faster than a low car on cavitating shocks, all else being equal.

Of course, all else is rarely equal... which is where we go back to the "people who are fast in spite of their setups, not because of their setups.

Dennis Grant? You know him. Author of "Autocross to Win", 2004 ASN/FIA Canadian D Modified Champions, 2002 SCCA ProSolo Honda Street Challenge Series Champions, 2002 SCCA ProSolo Street Modified Series Champions, 2003, 2001, 2000 CENDIV Divisional Champions, etc.

stinkycheezmonky

1. Dennis Grant does know his stuff, mostly, but don't take everything he says as gospel. No idea about this degassing business, but some of what he claims is argued against by other experienced, intelligent, fast people.

2. Performance Shock out in California is a GREAT shock company. They are not cheap, but also are not overly expensive. Their work is fantastic and their customer service is without equal. As others have said, no reason to rebuild a Sport though, so whatev.

C. Ludwig

Awesome. I also have a couple divisional club racing titles, held track records at Mid-Ohio and IRP, and a decent amount of success autocrossing. But what do I know? Maybe I should write a book?

If you're at the pointy end of any field you're probably not using Koni yellows anyway. I was just pointing out that degassing is used, and despite Mr. Grant's own views, has been used with good success. I'll agree 100% it's not the best solution. But then again, as mentioned, the Koni yellow isn't the best performance solution to begin with.

Back on point? As has been said, buy new shocks.

Thucydides

Chris, we're in agreement on all points.

Jim