J Chen

Hi Skip,
Let me rephrase my question.
1. On the Derlin outer spring plate bushings, one side
is flat edge & the other side is concave. When installing
the bushing onto the spring plate, which side should be
facing outwards.

2. What's is the proper way to align the front suspension on
steel arms with Welt poly bushings ? Yes , in your tech
article you mentioned to mark the position of the castor
blocks before removal. What if I forgot to mark it ?

keith

OK Skip, I'm confused again - I have 29.4mm diameter Hollow Torsion Bars in the rear. Is this an effective rate of 292# or 250#?

I am running 350# up front, but am understeering compared to the stock turbo S setup I replaced with this new setup. What SHOULD I be running up front to maintain the previous balance? 325#? 300#? 275#? I don't want to buy multiple sets of springs to get this dialed in...

I guess I need to know for certain what the effective wheel rate of the 29.4mm Hollow bars is.

Skip

Concave to the outside - sorry for the confusion. If you didn't mark the caster blocks on removal, there should still be some road grime marking their spot (unless you cleaned it too well, etc). Either way, if you are replacing bushings and doing a major suspension overhaul, now is the very best time to take it in for a proper alignment. Marking where they were can only transfer what was there before - right or wrong. That said, many folks prefer max caster - toward the outside of the car as far as it'll go.

Skip

Keith, the 29.4mm (measured OD) tubular/hollow torsion bar is actually 28mm effective - so, for calculations use this (254#). With this, I would start at a 300# front spring and work the tires and sway bars from there. Since you already have a setup, how about adjusting/adding something to counteract the overly sprung front (not really major, but since you're not happy with it...). Add more rear sway, add more rear tire, reduce front sway, etc. For more on the basics of handling adjustments, check out our tech-session article here:

http://www.tech-session.com/kb/index...x_v2&id=106&c=

FYI, I realize how the holllow bar rates can be confusing, so I just updated the tech-session article to reflect how the real hollow OD's match up with the effective solid OD's:

http://www.tech-session.com/kb/index...x_v2&id=22&c=4

Good Luck!

TonyG

As a point of referrence... I have no torsion bars. And there is no flex/play caused by the deletion of the bars. This has proven to be the case on 2 different 951's now.

And as for the increased unsprung weight... well that's splittin' hairs as the difference in unsprung weight between a coil over and a non coil over would be only a "portion" of the springs actual weight (which isn't much) and the bottom lightweight aluminum perches (trivial).

I can tell you one thing for sure.... a stock weight 951 (and we're talking a car with nothing but the spare tire and power steering pump removed.. but with a roll bar added) with 250lbs front and 350lbs rear with no torsion bars, and front/rear weltmeister sway bars (both set to full stiff) can quite easily run 1:32 or faster at Willow Springs Raceway (on the Big Track) with 275 rear & 245 front Hoosiers (also Big Reds/993TT front brakes), and Bilstein Escort shocks/struts, stock bushings throughout with no camber plates or strut tower brace.

There's a tiny bit of push at the limit that could easily be dialed out with an adustment of the front sway bar.

That's a proven setup that rides good on the street and is damn fast on the track.

And if you drove my car you would know for sure that the rear suspension of rock solid both on and off the track.

TonyG

Skip

If that's an invitation, I'll keep this archived

J Chen

Thanks Skip

TonyG

Skip


>>>If that's an invitation, I'll keep this archived <<<


Yes it it. I've let about 10 Rennlisters drive the car. If anybody knows how to drive these cars... it's a Rennlister that owns one!

The invitation is open.

TonyG

Zu_langsam

Some great info in this thread!.... Do you guys think that If I were to use a 400lb front spring I could balance out most of the associated understeer with a big rear sway? Car will have koni adjustables all around. Everything else is stock.

TonyG

Zu_langsam

No way.

The 86 951 has 23.5mm torsion bars that have an effective wheel spring rate of approximately 125lb.

There's no way you're going to balance out a 400 wheel spring rate against a 125lbs spring rate.


TonyG

Skip

Completely agree - you need to be thinking 30mm t-bars or equivalent in coil-overs... or, less front spring.

joster86turbo

quick question: is it possible to put 88 turbo S koni adjustable shocks and struts on a 86 turbo?