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rear coilovers,..i know i know,..but i have questions

ok, i have had coilovers on my last three cars, along with all poly bushings, larger sways, strut bars, top to bottom, spring rates ranged from 400f to 800r, the cars were a sti, gti, integra

anyway,...i have played around with this whole torsion bar setup numerous times, i just dont like it, period,...i want to switch to coils front and rear with 935 spring plates in the rear and do away with torsion bars all together

i am only looking at about a 300-325 spring rate in the rear, i think stock torsion bars are around 160? if i did my math right

i have talked to numerous shops, and people on this forum about the bracing of the rear shock towers, some say you need it, some say you dont,...i have looked at my shock towers and i see NO signs of wear what so ever, or cracking, still factory paint and in great condition, the car has 67k original miles, never seen a track...yet anyway

my question is with such a low spring rate, and no track time,..maybe 1-2 a year, is this something that i really need?

BIG QUESTION
i have seen some 964s and their suspension set ups, i know its completely different, BUT the rear shock towers look almost the same as the 930, why is it ok that the 964 guys all run coils without bracing,..? im sorry for the newbie question, but just looking at pictures the shock towers appear to be almost the same?

is there anyone out there running rear coils without bracing?

Old 10-16-2010, 07:25 AM
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subscribed..... I am interested in coil overs too, but for other reasons.
Old 10-16-2010, 09:54 AM
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Max Sluiter
 
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914s were not known for being particularly stiff, durable, or having high spring plates. 964 chassis is designed differently and is stiffer with better welding. It might even have thicker metal.

If you run helper springs with your torsion bars, then you do not need the bracing. If you go full coil-overs, the bracing is highly recommended. I have it on my torsion bar car.

Coil-overs are really not necessary with your intended driving style. What problems are you having with the torsion bars? I would just have a good shop set it up once to how you like it- corner balance and alignment, then forget about it. Coil-overs main advantage is being able to change ride height easily.

If you are still set on coil-overs, I recommend talking to Clint at Rebel Racing: Suspension1 He can go as far with the 935 setup as you want. If you cannot get ahold of him, email me. maxsluiter@earthlink.net
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Last edited by Flieger; 10-16-2010 at 10:30 AM..
Old 10-16-2010, 09:56 AM
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Quote:
Originally Posted by Flieger View Post
914s were not known for being particularly stiff, durable, or having high spring plates. 964 chassis is designed differently and is stiffer with better welding. It might even have thicker metal.

If you run helper springs with your torsion bars, then you do not need the bracing. If you go full coil-overs, the bracing is highly recommended. I have it on my torsion bar car.

Coil-overs are really not necessary with your intended driving style. What problems are you having with the torsion bars? I would just have a good shop set it up once to how you like it- corner balance and alignment, then forget about it. Coil-overs main advantage is being able to change ride height easily.

If you are still set on coil-overs, I recommend talking to Clint at Rebel Racing: Suspension1 He can go as far with the 935 setup as you want. If you cannot get ahold of him, email me. maxsluiter@earthlink.net
i like the flexability of coils, and being able to make the minor adjustments and dial in a height

i have had the 930 corner balanced, and aligned, and i just dont like the ride, i also replaced spring plate bushings and rear shocks, and just not happy
Old 10-17-2010, 04:31 AM
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Maybe check our the Elephant Racing rear spring plates. This might give you the rear adjustyou seek.

I believe it makes it almost as easy to adjust as the front. Maybe easer than rear coils.

See here: ELEPHANT RACING QuickChange Spring Plate, 911 Series
Old 10-17-2010, 06:15 AM
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don't know what year your 930 is, but starting in late 1987 for the 1988 models the factory welded in small bracing gussets on the top outer sides of the shock towers making them stronger.

could be (just a guess) they knew they were going to go to coil overs in a couple years and they were tooling up and installing them in advance.
Old 10-17-2010, 07:03 AM
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yes i had planned on ordering everything from elephant racing, its a 1980, there is no bracing backed there, trust me i looked,...

yes it has ALOT to do with adjustability, but i just dont like the "responsive-ness" and the ride of the torsion bars, i dont know how to really word it...

i really want to "update" the ride, if that makes sense

i recently put coils front and rear on a 66 mustang, and it was the greatest thing i did, i know you cant compare a mustang and a porsche, but i just like the "modern" feel of coils
Old 10-17-2010, 07:36 AM
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A spring is a spring.
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1971 chassis, 2.7RS spec MFI engine, suspension mods, lightened

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Old 10-17-2010, 08:14 AM
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Quote:
Originally Posted by jimtweet View Post
yes i had planned on ordering everything from elephant racing, its a 1980, there is no bracing backed there, trust me i looked,...

yes it has ALOT to do with adjustability, but i just dont like the "responsive-ness" and the ride of the torsion bars, i dont know how to really word it...

i really want to "update" the ride, if that makes sense

i recently put coils front and rear on a 66 mustang, and it was the greatest thing i did, i know you cant compare a mustang and a porsche, but i just like the "modern" feel of coils
60's technology vs 90's technology, there WILL be a difference. I am going the coil over route for different reasons than you. I have looked into bracing and I will be building a cage.

Quote:
Originally Posted by Flieger View Post
A spring is a spring.
incorrect, a coil will react differently than a torsion bar, there are variable rate springs etc....
Old 10-17-2010, 09:17 AM
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A spring is a spring but for some reason it is a reoccurring conclusion from those that have changed from torsion bars to coil over's on a 911 that the ride is different.

I can see that if one chose a progressive spring why this might be but most do not.

Effective spring rate is a combination of a lot of things including the tires, bushings, suspension design, etc.

On a torsion bar car the spring has to work via an arm of some type that may or may not act as a spring its self. In the front this might be more the case than the rear but the rear still has to act through about an 18" lever which may impart some level of its own spring rate. The rear rubber bushings will become part of this spring rate to a small degree even if they are not in a direct path to the ground.

On a rear coil over, if the shock ends are rubber, they become part of the spring rate. Thus the spring becomes isolated by about 1 combined inch of rubber bushing under compression and rebound that it did not have before. I wonder if this is not the most significant reason.

Or that maybe moving the spring to the shock also changes the spring rate to a less than linear rate as the angle of the spring relative to the arm changes with compression.

Not sure about this but I wonder if there is something to what the coil over crowd seems to believe is different.

There are other points as to coil over’s.

Yes, they can be more easily adjusted in the rear.

One of the biggest advantages to the change was access to higher spring rates. Now we can get up to 35mm rear torsion bars for the 4 speed cars that are probably more than anyone would probably run on the street.

Coil over's on the front may restrict front tire width and or access to neg camber with their increased width.

Most coil over conversions rarely shorten the strut or shock so that should the suspension become unloaded the travel of the shock may be more than the spring. Helper springs may be added as a short cut and even then shock travel may exceed the length of the springs. It just seems like it would not be a great idea if the springs can come unseated from there base over a bump or when jacking up the car.

Last edited by 911st; 10-17-2010 at 10:01 AM.. Reason: spelling
Old 10-17-2010, 09:53 AM
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Clint at Rebel Racing has all you need for coil overs. He modifies struts, has custom damper setups, 935 spring plates, I think he can get the 935 front suspension, or he has his signature A-arm bearings. He uses an early 911 with coil-overs for street and track.
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Old 10-17-2010, 12:08 PM
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Quote:
my question is with such a low spring rate, and no track time,..maybe 1-2 a year, is this something that i really need?
No...

replace the bushings with some with less friction, and you will be pleasantly surprised.. This will cost you a lot less than 935 spring plates/coils/hats/chassis/reinforcements...

If you were building a track car... that is another story...
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Old 10-17-2010, 12:40 PM
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Quote:
Originally Posted by 911st View Post
Most coil over conversions rarely shorten the strut or shock so that should the suspension become unloaded the travel of the shock may be more than the spring. Helper springs may be added as a short cut and even then shock travel may exceed the length of the springs. It just seems like it would not be a great idea if the springs can come unseated from there base over a bump or when jacking up the car.
There is a real simple solution for this and we use it in race cars to get the tires off the ground quicker in pit stops, you just have limit straps that will limit the droop of the suspension.
Old 10-17-2010, 03:01 PM
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Quote:
Originally Posted by TimT View Post
No...

replace the bushings with some with less friction, and you will be pleasantly surprised.. This will cost you a lot less than 935 spring plates/coils/hats/chassis/reinforcements...

If you were building a track car... that is another story...
i thank you for your response, but i was asking if i really need bracing, not if i need coils, i know many people think coils are overkill for the street, but i never had a issue with them in the past on any street car i have owned, i am just trying to update the feel of the car,...
Old 10-17-2010, 03:31 PM
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what? me worry?
 
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Quote:
i have owned, i am just trying to update the feel of the car,...
You will be pleasantly surprised, and your wallet will be happier if you put in some quality bushings.... reduce the friction in the joints, and let the t-bars work..

Granted you can follow the path you outline, you will have a fine set up suspension, or you can go another route and save yourself a bunch of dinero,
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Old 10-17-2010, 03:45 PM
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i am still leaning towards the coil route, i do plan to pull the trans and engine for a trans rebuild in the next year or so,..so that is probably a great time to do some bracing,...
Old 10-18-2010, 02:19 PM
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If I go the coil over route for my project, I will fill you in on my process.
Old 10-18-2010, 03:51 PM
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I think I can do something better than this and incorporate it into the cage.

http://www.tarett.com/items/911-series-products/911-suspension/rsr-style-rear-shock-tower-reinforcements-rsrstr-detail.htm
Old 10-18-2010, 04:00 PM
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jim i just finished doing helper springs on my 87 930 i used clints set up with 250# springs ran it this weekend at vir and it was great i did change front to 22 mm torsions and used clints rsr a arm bearings
Old 10-18-2010, 05:15 PM
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Quote:
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jim i just finished doing helper springs on my 87 930 i used clints set up with 250# springs ran it this weekend at vir and it was great i did change front to 22 mm torsions and used clints rsr a arm bearings
that is the thing, i want to do away with torsion bars all together, and i am being told that with such a low spring rate and no track time, the bracing isnt something i need to worry about

Old 10-18-2010, 05:34 PM
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