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Join Date: May 1999
Location: goleta, ca, usa
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Front suspension

I am running a pretty competitive 914/6 with a stock 3.0. The long windy courses I hold my own, but on a bumpy one I have fallen on my face. My front suspension pogos up and down and I have to back off the pedal. I am running 23mm torsion bars, 23mm sway bars and stock non-adjustable Bilstein 911 shocks.

I have been cornered balanced and my toe in and all are done right. More than a few say it is the sway bar doing me in. I think it is the torsion bars.

Earlier in the year, I changed both the torsion bars and replaced the front bushings at the same time. The bushings and torsion bars were original. The bushings and sway bar, are now Welmiesters. I know, I should only change one thing at a time...

Does anyone think I should try to go back the stock torsion bars? Or are the shocks my problem or torsion bars....I hate throwings parts at a problem.

Any suggestions or insight are welcomed.

Regards

Mike
Old 05-16-1999, 03:46 PM
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Are you sure its the front suspension and not the chassis. If one goes with big tires, springs, horsepower, etc. one reaches the point that the 914 chassis is overwhelmed.
I noticed some cowl shake on my car prior to puting in the six. I haven't worked it hard on a bumpy road lately, but I'm sure it has not gotten better.
My solution is an 8 point roll cage(which I have yet to install).
The best suspension in the world is useless without a stiff chassis (love to talk dirty).

J P(junior wannabe) Stein

[This message has been edited by J P Stein (edited 05-16-99).]
Old 05-16-1999, 06:13 PM
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The phrase "pogos" suggests that the shocks may be to blame. Possibly worn out, possibly too stiff.

The 911 shocks were specified/designed for a differnt car, and may not be quite appropriate for yours.

I'm not sure how the swaybars would make you "pogo". However, a stiffer front end *would* make the car push, and that would make you have to back off the throttle.

Do you feel the car is balanced? Perhaps stiffer rear springs would help.

--DD
Old 05-16-1999, 08:20 PM
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I read somewhere that putting rear sway bars on a 914 negates the gain from putting them on the front, unless you go with a much fatter rear tire. Makes sense to me. With that much power I would definately go with the roll cage. I installed chassis repairs and the GT stiffening kit and still had a bit of door sag. A roll bar eliminated the slight amount of door sag, a cage would be even better. From the handbook, Porsche High-Performance Driving, by Vic Elford: "Remember that Porsches, most other performance cars, and virtually all competition cars have antisway bars at both front and rear. Doing something to one of them does the opposite to the other one. If therefore, you are trying to adjust the car to have more understeer, you could increase the stiffeness of the front antisway bar. But you could also decrease the stiffness of the rear antisway bar. Or you could do a combination of the two!"

[This message has been edited by halbl (edited 05-17-99).]
Old 05-17-1999, 09:00 AM
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The rear sway bar will not negate the effect of the front bar.

A swaybar reduces body roll, but transfers more load to the outside tire. Reducing body roll is a good thing, but putting extra load on a tire is not. The overall effect is that a stiffer sway bar will tend to make the whole car stick better, but the end the sway bar is on will gain less than the other end. Also, bumps that one tire hits will affect the other tire more than with a softer sway bar (or none).

So a rear bar will *tend* to make the car stick a bit better overall, but will make the car more tail-happy. Stiffer rear springs have a similar effect.

The two worst things about (most) rear swaybar installations are that 1) the inside rear wheel can be lifted to the point where applying power will make it spin (hello, oversteer!!!), and 2) the bar can "bottom out", resulting in a loud "Thwock!" sound and a VERY stiff rear suspension.

The suspension really should be considered as a whole system, though. Any single part can be overdone, and that can result in an unbalanced car and odd effects.

Please see Carroll Smith's "Tune To Win", and Fred Puhn's "How to Make Your Car Handle" for more info. Both books are old, but not too out-of-date from what I hear.

--DD
Old 05-17-1999, 12:06 PM
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Thanks for the suggestions, I might want to emphasize that the pogo effect was AFTER the 23mm torsion bars and bushings were added. I had already been running the shocks with no real ill effect.

As to the rear sway bar in the garage, but want to get the front end problem fixed before I add any more variables. BTW-I also have been using a Quaife limited slip rear end.

DD-I will try Amazon.com for those publications.
Old 05-17-1999, 09:59 PM
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It sounds like your car is too stiff for the bumpy courses. On a bumpy course you need to soften the torsion bars/springs as well as soften the sway bar. Try soften the sway bar and see how that works. Since you can not easily change the front torsion bars between track events, you may find that you need to decide which is worse - backing off on the bumpy courses and staying with the current torsion bars, or not being optimum on the smooth courses and going to smaller torsion bars.

Don't assume that just because the shocks worked with the other torsion bars, they are good for the new ones. By changing the torsion bars, you have changed the frequency that the car will bounce, therefore changing the valving required in the shocks. As Dave said, the shocks were incorrect before since they were valved for a 911, but maybe close enough to be ok. Now that you have done further mods, they might not be acceptable any more.

BTW - The Carroll Smith books are awesome. You need the first two at a minimum - Prepare to Win and Tune to Win. You won't find a professional race team without at least one copy of those.
Old 05-18-1999, 05:54 AM
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I have ordered the books and the adjusatable Konis for the front, I will post the results. Thanks again for the advice, sometimes when the answer stares you in the face a good slap wakes you up.
Old 05-18-1999, 10:32 AM
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mikyz. While you are at it perhaps you should consider some of the "bump stear" posts, an issue for 14's with lowered front suspension.
Old 05-20-1999, 02:55 AM
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Installed the new sport adjustable Konis today. That has the problem solved. The original Boge inserts had leaked and all the oil was in the strut body. What a mess!!

Thanks to everyone for the suggestions. The Koni adjustment at firm, is very firm. Too firm for the street. I backed it down to the minimal setting and then turned it back up twice. The max firm is five turns. Max firm will more than adequate for the track.
Old 05-22-1999, 09:15 AM
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Sometimes oil or antifreeze is put inside the front struts to help conduct heat out of the inserts (shock absorbers). When the shocks "do work", they generate heat. Too much heat, and the damping goes away. It is usually not an issue for street cars.

Check with other local 914 racer-types to see if they are putting fluid in the struts, or if they are experiencing a loss of dampning. If not, you probably don't have to bother with it.

--DD
Old 05-22-1999, 04:03 PM
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Old 05-22-1999, 04:03 PM
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