Tarret Engineering, Cool stuff Options

[PeeGreen 914]

Just browsing his site and noticed these:
(IMG:style_emoticons/default/idea.gif)

Front Coil Over Conversion Kit

[ConeDodger]

Push...

Neat idea though. I wonder if you remove the torsion bar when you put it in. I like using the sway bar with stock spring rate over huge torsion bars or stuff like this.

[enderw88]

Just browsing his site and noticed these:
(IMG:style_emoticons/default/idea.gif)

Front Coil Over Conversion Kit

Still a newb WRT Porsche stuff but these seem like a ghetto solution. Not just cheap, but bad:

1. Adding a sleeve around the existing shock body will reduce the shocks ability to dissipate heat (all that energy it is damping has to go somewhere). Seems like this would dramatically shorten shock life. This means saving now, spending more later...
2. Are you supposed to "disable" the torsion bars somehow or use them in conjunction with the additional coil springs? Does the structure of the car support shifting full suspension loads to the top shock mount?
3. Are the shocks that this is supposed to surround structurally able to handle the full load through their joints? That load is normally taken through the torsion bar and only a fraction of the weight of the cars is applied to the shock mounts.

[Dave_Darling]

I don't specifically know about the Tarrett stuff, but Ira is not known for under-engineering his stuff. That said:

1) It is very rare for shocks to overheat. Most of the coil-over conversions for the rear of the 914 (and for many other cars!) use a threaded sleeve, and we do not hear about heat issues with them. Not even in race cars, which I would think would have the majority of the issues. An off-roader might well have problems, though.

2) Most coil-over conversions are designed to replace the torsion bars, not to supplement them. That said, I bet you can set it up like the 944 rear (?) where the coil and torsion bar work together. But the A-arm can be replaced with something much less beefy if you aren't transmitting the spring forces through it.

3) The shocks should be OK for that; almost all cars besides our 914s and their VW and Porsche kindred use coil springs and the same design of shock absorbers.

However, we have heard that the upper mounting points should be reinforced if you do switch to coil-overs in the front. Some have noted no problems after a while, but others have talked of problems in the area. So the mounts and the chassis may need to be beefed up to run that kind of setup over the long haul.

--DD

[jjackson]

(IMG:style_emoticons/default/agree.gif) We ran a similar setup to this for about 8 seasons.Never experienced any of the above mentioned concerns.We did not run as a supplement to torsion bars-we removed torsion bars completely.This setup is the reason that we could do so much testing in the front end.Lots of reasonable sources for springs.We ran 2.5 inch springs on konis.JJackson

I don't specifically know about the Tarrett stuff, but Ira is not known for under-engineering his stuff. That said:

1) It is very rare for shocks to overheat. Most of the coil-over conversions for the rear of the 914 (and for many other cars!) use a threaded sleeve, and we do not hear about heat issues with them. Not even in race cars, which I would think would have the majority of the issues. An off-roader might well have problems, though.

2) Most coil-over conversions are designed to replace the torsion bars, not to supplement them. That said, I bet you can set it up like the 944 rear (?) where the coil and torsion bar work together. But the A-arm can be replaced with something much less beefy if you aren't transmitting the spring forces through it.

3) The shocks should be OK for that; almost all cars besides our 914s and their VW and Porsche kindred use coil springs and the same design of shock absorbers.

However, we have heard that the upper mounting points should be reinforced if you do switch to coil-overs in the front. Some have noted no problems after a while, but others have talked of problems in the area. So the mounts and the chassis may need to be beefed up to run that kind of setup over the long haul.

--DD

[J P Stein]

I have never used coil overs up front but I made good use of the room freed up by their not being there. No strut dust covers either. I wanted the canti slicks inboard as far as they would go.....it's a scrub radius thing.

BTW, torsion bars have 0 unsprung weight....but 0 bling.

[brant]

coil overs on the front would be good if you needed to change to higher spring rates or experiment alot

lets be honest..
99.99 of the people on this board will never change their front spring rate for a particular track or outing.

coil overs are easier to change when you go to each different track.. pro teams try 3-4 spring rates a day

914 guys use one spring rate a decade.

[sww914]

You should change to oil overs when you and your car have advanced to the point that you need spring rates that aren't available with torsion bars. Not because they're pretty.

[jjackson]

You should change to oil overs when you and your car have advanced to the point that you need spring rates that aren't available with torsion bars. Not because they're pretty.

We tested in 50lb increments,with and without sway bars, and multiple sway bar adjustments.I guesss were in the .01% bracket.Never ran a part for bling or pretty so would not understand the concept.When we ran the radials A6s and slicks , the room that the coilovers took up-based on the camber the tires required-became a problem without good camber plates.With the bias plys-never been an issue.Running a slightly wider track in front than JP was.His point on scrub radius is absolutely correct.Tires need to be inset as much as possible in the front.Dedicated autox car-bling is on the clock.JJackson

[jjackson]

With all of the previous being said-Proper valving and tuning on struts in relation to springs -ride height-rake-sway bars etc-is extremely critical for most (some -very few, are the exceptions to this) national level autox competition.We worked with the wrong guy on our single adjustable konis.Bilstein guys on the left coast seem very reasonable and competent-we never went that route.JJackson

[FourBlades]

Loving this thread.

Lots of good information here.

John

[sean_v8_914]

our canti slicks run very close to the strut. we woujld need to space the wheel out to fit coil overs.

what do you think about the advantage/disadvantages of scrub radius vs increased track width?

[J P Stein]

our canti slicks run very close to the strut. we woujld need to space the wheel out to fit coil overs.

what do you think about the advantage/disadvantages of scrub radius vs increased track width?

No contest (IMO) if you're an AXer.....unless you like understeer in the tight stuff.

That said, it's really the center line of the wheel that you need to keep inboard. 7 or 8 inch wide wheel with no spacers (5 inch backspace) is as wide as I will go.
The 8 inch ia pushing it some but provides better sidewall sitffness for the cantis.

For the track (wider radius corners) the issue is not critical.

[sean_v8_914]

we were wondering about the cantis on 7" vs 8". thats like a bonus answer

I'll measure that JP and report back. we do have to space them out some to clear the strut in front

we did not think it was pushing but I tend to compensate and drive "around" an issue. Herb has better feel for such things and he liked it. I just change my technique. this is probably why Im teh tuner and Herb is the real driver. (faster than me)

[sean_v8_914]

PS. we like our Tarett bar set to med/soft w 21mm torsions and 225 rear w rear bar

[PeeGreen 914]

PS. we like our Tarett bar set to med/soft w 21mm torsions and 225 rear w rear bar

Sounds similar to my set up on the 6 with exception to a TB diff and 275lb rear springs and no rear bar.

[sean_v8_914]

lsd would be nice but right now its a waste of time with a stock d jet 2.0. I better build something else before that ole 2.0 tells us to pound sand