Points for converting to coil-overs on a coil spring car?

[TurboShortBus]

This question applies to converting to coil-over spring/shock assemblies on cars that were originally equipped with coil springs that were located separately from the shocks or struts (for example, front and rear on 1979-2004 Mustangs, rear on 2005-up Mustangs, rear on late model F-bodies, etc.). The conversions that I'm referring to are the typical threaded sleeve and spring style kits that slide over the OEM-style shock or strut (available from several manufacturers for $500-$800 for a set of 4, or average $125-$200 each).

 

From reading the 2009 TTA-TTF Classification Form v6.1, one of the following items would apply if the OEM shocks/struts/dampers are not reused (this will vary based on what the driver uses; my comments are in italics):

 

1) Non-OEM shocks/struts/dampers with an external reservoir or more than two ranges of adjustment +10 (but only if you use something this fancy)

 

2) Non-OEM shocks/struts/dampers with a retail price of greater than $600 per unit ($2400 total) or $750 each if sold only as a coilover with spring included ($3000 total). Also "Piggyback" external reservoir shocks/coilovers/dampers with a retail price of less than $1050 per unit ($4200 total)--must still take additional points for the springs below +7 (but only if you use something this fancy)

 

3) Non-OEM or modified/re-valved shocks/struts/dampers +3 (all others)(springs not included) (note that a single-adjustable set of 4 for a 1979-2004 Mustang is commonly available for $500-$800, or average $125-$200 each)

 

The following would definitely apply, no questions asked:

 

4) Non-OEM or modified coil springs, leaf springs/spacers/brackets, or torsion bars +2

 

From my interpretation, only the items above would apply to something like this, as long as no other modifications are performed (no inverting of shocks, no modification of front or rear arms, etc.). However, please advise if the following points would apply:

 

Relocation of front suspension mounting points +6

 

9) Relocation of rear suspension mounting points +6

 

Please note that I would like to request an official determination on this, not just random speculation (although I normally appreciate a productive discussion). I figure that anybody else who is considering the same setup could use this thread for reference and avoid a possible "surprise" if they hadn't planned for it; if it doesn't apply, then the issue will be eliminated.

 

Thanks,

Mark

[soundguydave]

You know it's dangerous for the two of us to even TRY to interpret the rules, but here's my take on it...

 

Assuming the stock setup, SN95 has weight-jacker control arms, and the S197 mounts the springs on the axles, both independent of the shocks. Both have MacPhereson struts up front, which means that the spring rests on a perch mounted to the strut body at the bottom, and on a strut bushing at the top. Converting the front to coil-overs (which a McStrut technically is) would cost you points for non-OE struts, and non-OE springs. The lower perch simply adjusts ride-height (and thus corner-weighting), there is no mechanical or competitive advantage to having the lower spring perch moved up or down relative to the stock location, all other things being equal.

 

In the back, using a true coil-over, I could see the points assessed for rear suspension mounting point relocation, since you HAVE moved the spring mount to a non-OE location. Don't know about the SN95 chassis, but on the S197, you have to reinforce the shock tower to support the weight of the car. A lot of the S197 "coilover" kits include a threaded spring perch that mounts in the STOCK, OE location, so again no relocation has taken place, so there should be no points assessed.

 

Bottom line: take the points for dampers and springs (same as if you just did Eibach springs and Koni dampers, the cheap ones), and only take the relocation points on the rear if you convert to a true coilover. If you do, however, since you're spending the points, you might as well go all the way and relocate the whole kit, since you've spent the points anyway!

 

Just my two cents, and I'm almost positive we'll be in another "control arm vs. trailing link" discussion soon!

[kbrew8991]

you're modifying (ie relocating) the spring, not moving any point where a control arm (or even a de-facto control arm ie shock) bolts to, thus no relocation points, thus only getting the +3 and +2 from the simple shock & modify spring lines

 

same deal for the front, rear, or both ends of the car

[TurboShortBus]

Good deal, Ken. Thanks for your reply!

 

Mark

[Shawn M.]

Please note that I would like to request an official determination on this, not just random speculation (although I normally appreciate a productive discussion). I figure that anybody else who is considering the same setup could use this thread for reference and avoid a possible "surprise" if they hadn't planned for it; if it doesn't apply, then the issue will be eliminated.

 

Thanks,

Mark

 

 

Mr. McKay, for future reference the only true way (and sometimes much faster) to get an official determination is to e-mail Greg directly. Hes one of these guys who has really odd work schedule/hours so he sometimes replies right away, sometimes takes a while. Im not saying (I think it can make for good discussion and open eyes to different perspectives by posting here) you cant ask here. Im just saying the proccess is faster going directly to Greg via E-mail.

 

FYI, I agree with Ken.

[TurboShortBus]

Thanks for the info, Senor Meze. But, on this particular subject, I'm not in a rush for a ruling, and I'm not even 100% sure that it will apply to my car yet. Plus, I'm sure that I'm probably not the only person who might have these questions, so at least others can search and read these threads down the road, since not everything is mentioned in the Rule Addendums and Clarifications link on the TT rules webpage.

 

I agree with Ken as well, but I wanted to compare my interpretation with that of the TT rules staff.

 

I'll wait to see what Greg has to say.

 

Mark

[RodeoFlyer]

Both have MacPhereson struts up front, which means that the spring rests on a perch mounted to the strut body at the bottom, and on a strut bushing at the top.

 

Hi Dave -

 

Fox/SN95 cars have MODIFIED Mac strut front suspensions. The springs rest on the control arm, inboard of the strut. Switching to coilovers DOES relocate the spring, unlike the S197, which has a true Mac strut setup.

 

Relocating the springs isn't changing any suspension geometry.

 

My money is on +3 for dampers, +2 for springs, and ride height adjustment is free.

[soundguydave]

Both have MacPhereson struts up front, which means that the spring rests on a perch mounted to the strut body at the bottom, and on a strut bushing at the top.

 

Hi Dave -

 

Fox/SN95 cars have MODIFIED Mac strut front suspensions. The springs rest on the control arm, inboard of the strut. Switching to coilovers DOES relocate the spring, unlike the S197, which has a true Mac strut setup.

 

Relocating the springs isn't changing any suspension geometry.

 

My money is on +3 for dampers, +2 for springs, and ride height adjustment is free.

 

 

Gotcha! The last Mustang that I owned was a '68, so that's info to file away for me... Personally, I'm just glad that there appear to be no additional points for converting to a coilover than there are for the damper/spring swap.

[TurboShortBus]

Hey Dave,

 

Here's a typical OEM-style Fox/SN95 front setup (non-OEM springs and struts, though):

 

 

 

Mark

Edited April 14, 2009 by Guest

[kbrew8991]

considering that you can relocate the top of the strut (a defacto control arm with mac struts) points free with a caster/camber plate - not alot - but some... I can't see any justification whatsoever for moving a spring from one location to another being worth any extra points over the +2 from modifiying the spring in the first place

[Greg G.]

Mark,

 

As long as the only modification is to move the spring to the "coilover" position on the shock, then the points would just be the +3 for the shocks (unless one of the higher categories applies) and +2 for the springs. However, if there is also movement of arms, arm bracket mounting points, numbers of arms, etc, then the +6 relocation assessment would apply.

[TurboShortBus]

Greg,

 

Thank you for the reply. You are correct; the only part that is changing location is the spring itself. All arm, spindle, and axle mounting points and quantities will be unchanged.

 

Mark

[Joshua]

Good news for you!