Ghia Road Course Setup

[Piledriver]

Bilstein part# system for racing shocks-- 2 "standards" at least.
("The nice thing about standards is that you have so many to choose from. "---Tannenbaum)

There also seems to be another 1-9 damping rating scheme used that translates to the newer part#
(is related to the 1-9==10-90 scheme used in the newer # designations, but with less granuarity,
(6530 would for example translate to 6.5/3 valving in some listings)

Here's SOMETHING pulled from ebay, data likely Bilstein sourced, for the ~$90 monotube Bilstein coil-over ready shocks I'm planning to use. I imagine the translation table could be derived from this:
Note Bilstein will custom valve these for $<15/shock. (has to be done when ordered, non-rebuildable)
There are 21 standard valvings off the shelf, not everyone lists them all

From Bilstein catalog:

sg Available in these standard valvings:
(Example: S6G-3060 or S7G-5555)
* Built with COB piston for strong “tie-down”
** High bleed valving designed for rear
1030 3060 5555
1090 3535 6020**
2020 4010 6035*
2040 4020 6565
3010 4040 7035*
3020 4545 8035*
3030 5030 9010

(From http://www.ebay.com/itm/NEW-BILSTEIN-6- ... 0366842980 )

Bilstein-newpartno-to-force-chart.png

These example are from Bilsteins Motorsport shocks catalog.

Damping force is in ref to "industry std # I have yet to find a force table for yet.

Bilstein-newpart#std.png

Old system, (still used) force in lbs, at 10"/second stroke
(there is also a metric equivalent used in some cases)

Bilstein-oldpart#std.png

[Piledriver]

Next question--

For street/AX/road racing, do you want the compression and rebound the ~same, or rebound less?

Anyone have any data?

[Piledriver]

Referring back to the "caster vs. trail" posts---
"Trail" is the whole point of caster, but caster is NOT the only way to get there.

Trail is what caster does, with a side dish of camber gain.
"trail" via moving the axle aft with ZERO caster accomplishes the same "goes straight" effect with no camber gain.
(assuming trail value is equivalent)

Many modern cars use tons of caster (10+ degrees) for better low speed-turning aid camber gain, and move the axle back vs. kingpin axis so the actual trail is still sane.

More trail, more steering feedback and more "goes straight" effect.

[ChadH]

^^^
Makes sense to me.

From what I understand though, more caster/trail is not always better. I know bikes/motorcycles can get "head shake" if there is excessive trail and at the right speed it'll s set up a left/right resonance...kinda like when you get a bad shopping cart and one of the wheels goes crazy.

I'm not sure how prevalent the phenomenon is with a heavier car, but it seems possible.

I guess you could set up a car with a bunch of caster (for camber gain) but pull back the actual trail by adjusting the axle center line ?

I'm just BS'ing on a bunch of theory I only partially understand, but It's Friday afternoon, so It's fun to think about.

[Piledriver]

^^^
Makes sense to me.

From what I understand though, more caster/trail is not always better. I know bikes/motorcycles can get "head shake" if there is excessive trail and at the right speed it'll s set up a left/right resonance...kinda like when you get a bad shopping cart and one of the wheels goes crazy.

I'm not sure how prevalent the phenomenon is with a heavier car, but it seems possible.

I guess you could set up a car with a bunch of caster (for camber gain) but pull back the actual trail by adjusting the axle center line ?

I'm just BS'ing on a bunch of theory I only partially understand, but It's Friday afternoon, so It's fun to think about.

Tank slapper effect has a lot to do with stiffness of the parts.
I suspect more trail would add damping, helping vs. make it worse.

I'm strongly considering fabbing my own drop spindles for my T3 (traditional T1 style weld-on-a-plate), and if I go there adding some trail is trivial.
Just another knob, but set things right I can use the upper eccentric ball joint to crank in more camber and not lose all my "trail". Adding caster is very hard, and would involve moving the core steering knuckle or extending the upper arm, which i absolutely don't want to cut and reweld.

Modern lower ball joints for T3 are all non-eccentric, so you get significantly less caster than factory spec even not lowered.
Lowered even a little using the springs you end up with ~zero caster. (upper arm is slightly shorter)

[cmaxcliff]

A few things are in the production stage for the Devin D race car.

frame being replicated in chrome moly with new Puma beam

3.50* link pin combi spindles being produced

Rancho close ratio swing transaxle ordered, 3.44 R&P, Quaife lsd, 2.90, 2.08, 1.56, 1.26

body at media blaster

custom Penske double adjustable shocks ordered

powered by a 1622cc Porsche 356 engine producing between 165 and 180hp

I haven't chosen the shifter/linkage yet but I like the Vintage Speed Classic- any opinions? opinions on couplers?

I have a 1960 VW steering box or I could buy a new one or I could find a Porsche ZF box...opinions?

[Steve Arndt]

Are you having Mikes Machine make the spindles? 3.5 degrees of extra camber built in?

[FJCamper]

Hi Cliff

Please tell us about your 1622 engine. It should be interesting to everybody.

FJC

[cmaxcliff]

Yes, Mike is making the spindles.

The Porsche 356s that are racing are allowed 1mm of overbore to 83.5mm and the stock 74mm stroke for a total displacement of 1622cc. the front runners are generally using the same formula of 40mm intakes, 312*(advertised) duration/.535" valve lift cam, 11.5 JE pistons, stepped Bursch race exhaust, and highly modified Solex twin 2 barrel carbs. The typical engine makes a realistic 165hp but some make a bit more. There are some additional modifications that I do such as smaller rod journals, 8mm titanium valves, nikasil cylinders, steel camshaft using non-typical profile, and custom stainless 4 into 1 with reverse megaphone. I have seen 180hp on a reputable local engine dyno but I suspect that is optimistic even though I do seem to have more power than other 356s. Dynos can't really be trusted unless it is of the precision level of the expensive OEM dynos.

The engines do break and common failures are cracked camshafts(iron), camshaft wear(steel), and broken rocker arms. Generally the redline is held to 7500rpm but I do go to 8000. The key to reliability and power is a well executed valve train as well as good gas-flow and combustion.

I don't know much about VW Type 1 engines other than what I read and a visit to Pauter Engineering with a friend that knows them well. I do read as much VW tech stuff as I can in case I learn something I can apply to the Porsches. I do get the feeling that the VW engine would be stronger and more powerful but don't really know. Because I can't get VW gear ratios that are as close as the Porsche ratios I may end up detuning the Porsche engine in the Devin to allow the power band to be wider unless the lower race weight solves that problem.

[Evil_Fiz]

FJCamper, thank you squared for this application specific how-to and what-to. I have a few questions for the experts. This will be on a street-only midlife crisis compensator (1970 Ghia Convertible.)

I apologize in advance for not being able to contribute more to this forum, I am still educating myself on how to build my car the right way.

I am looking to make the Ghia as responsive and predictable as possible. I have read through this thread at least five times and have consumed every bit of suspension tuning information available to me. I will be using the stock width beam with 2.5" lowered spindles but have yet to finalize my plans for the rear.

What is the prevailing opinion on full length Delrin vs Urethane for the front beam in a street application? I did not see mention of it in the front suspension section and all the information I find is for off-road use which points away from urethane due to durability issues. I am not terribly concerned about the possible NVH as a result of using Delrin but I want the right product for the job.

Is Delrin or Urethane the recommended material for IRS pivot bushings? (again, off-road info is what I am finding)

and finally,
Would I see any gains if I use a triangulated truss bar (Mendeola "Stiffy,") coil-over shocks, and Heim jointed, 2" drop spring plates. I suppose this setup would require some shock tower reinforcement beyond what the truss bar will offer.

Thanks,
Emil

[FJCamper]

Hi Emil,

All I've used is Urethane, and for the front beam axle it works if you take the time to ream it, sand it, and just generally make it fit. On assembly, use lots of silicone grease.

I am under the impression Delrin is harder than Urethane, and might come out of the pkg with a better shape and less friction as it rubs against metal.

I can tell you based on my Urethane experience for the track I favor stock roller bearing and Micarta bushings for the front axle. Less friction, less binding. The much greater surface area of the Urethane/Delrin is probably much stronger for offroad use.

But, for IRS pivot bushings If I had to do it over again, I'd go Derlin.

A kafer style truss bar is a good addition, and that is experience speaking. Your question about converting to a coilover rear suspension is one we've grappled with here, weighing cost and complexity against possible handling benefits.

We believe, theoretically, that a coilover rear end should be better, and of course is far more adjustable. But on the actual track, historic vintage racing in which we are competing against sports cars with all types of rear suspensions, we do not see any one design being clearly superior.

The IRS design as used by VW, on the early Porsche 911, and the 924-944, is excellent.

FJC

[CobraJet]

What about sway bars? How big are you running them front vs. back? Would you use the same sway bar on the street as on the track?

[FJCamper]

We run a 19mm front bar, nonadjustable. Depending on the track, we will either run a 19mm rear bar or no bar at all.

We do better on fast tight tracks with a rear bar. But on tracks with fast sweeping turns, no bar at all. With no rear bar, we have more understeer and that's what you want in 100 MPH+ sweepers.

FJC

[Evil_Fiz]

Thanks FJCamper for the feedback.
I also have a few questions about brakes. If I understand your contribution about brakes correctly, you are using drilled solid rotors front and back.

- Are you still using the Wilwood DynaLite calipers up front?
- What calipers would compliment the 4 pot front DynaLites out back?
- would the e-brake single pot Wilwood suffice or should I consider the Powerlite Handbrake Caliper (up to 750 kg car) sold in the UK and a proportioning valve?
- Am I overthinking this and should just stick with stock front calipers and drilled rotors and get a CB rear kit with drilled rotors?

I am aware that a master cylinder upgrade will be needed.

Thanks again,
Emil

[Piledriver]

A new master cylinder is not needed unless you use oversized caliper pistons: too big is not a feature.

I have 944T Brembos (4x 28mm) out back and Wilwood superlites up front with 4x 1.25" pistons and the pedal/balance is excellent, stock 19mm master cylinder. The F/R balance seems perfect, you might get away with 1.38 fronts on a Beetle due to somewhat higher CG, on a lower T3 or Ghia 1.25" IMHO is more correct. (per Brakepower.coms brake bias spreadsheet, too)

The common MK4 Jetta/Golf calper wit the integrated parking brake is a good match, I only ditched mine as the parking brake take up works in a stepwise fashion and gave a somewhat inconsistent pedal.