[pure&simple]

I recently purchased a new 968 for my daily driver and am having it built into a drivers ed car. The suspension is shot (107,000 miles on it), so that has to be replaced prior to my first track event in October. I've asked around and gotten a number of different opinions on how to build the suspension...



Since I'll most likely go with coilovers, what do you guys think of removing the torsion bar, rather than just re-indexing it? As I understand it, the pros are:

1. if you remove it, you never have to mess with it again (potentially saving future labor cost)

2. makes the car a bit easier to setup since the rear is no longer half linear (regular springs) and half progressive (torsion bar)

3. is there a weight savings too?



The cons are:

1. Searching the forums turned up a post by flash that said you have to go to a spherical bearing in the rear when doing this, which would decrease the ride quality for a street-driven car



Thoughts anyone?

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[flash]

well, first off, yes, it can be done



yes, it is a lot easier to dial in to your preference



yes, there is a marginal weight savings, but barely worth a consideration



no, it isn't cheap - you're could be looking at $1200 in parts to do it right - we almost have the kit ready, but haven't proceeded because of the cost prohibited marketability - we are trying to find ways to cut the costs down - there are less expensive setups out there, but they are all gas, and that is exactly the wrong direction for street quality ride - this is one where you get what you pay for



i didn't lose any ride quality, and in fact improved it - the car is very smooth in the rear, but nicely responsive - no jittery bouncy nonsense like with konis, or M030, or something like that



however, unlike merely adding coilovers, there are things you have to do if you delete torsion bars:



the rubber bushings in the torsion tubes have to be replaced with solid ones - the rubber cannot hold the control arm still without the torsion bar



you must run spherical bearings top and bottom on the shocks - again, rubber or polyurethane will not support the entire load



hope that helps

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[coloradocab]

[quote name='pure&simple' post='57359' date='Aug 5 2008, 07:19 AM']I recently purchased a new 968 for my daily driver and am having it built into a drivers ed car. The suspension is shot (107,000 miles on it), so that has to be replaced prior to my first track event in October. I've asked around and gotten a number of different opinions on how to build the suspension...



Since I'll most likely go with coilovers, what do you guys think of removing the torsion bar, rather than just re-indexing it? As I understand it, the pros are:

1. if you remove it, you never have to mess with it again (potentially saving future labor cost)

2. makes the car a bit easier to setup since the rear is no longer half linear (regular springs) and half progressive (torsion bar)

3. is there a weight savings too?



The cons are:

1. Searching the forums turned up a post by flash that said you have to go to a spherical bearing in the rear when doing this, which would decrease the ride quality for a street-driven car



Thoughts anyone?[/quote]



You shuold also consult the rule book for classifications of cars if you plan on competing with it on the track. In my area, removing the torsion bars bumps me up to the next level. Partially for that reason, I just put coilovers on the car last week, but left the torsion bars there.

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[josephsc]

[quote name='coloradocab' post='57387' date='Aug 5 2008, 12:20 PM']You shuold also consult the rule book for classifications of cars if you plan on competing with it on the track. In my area, removing the torsion bars bumps me up to the next level. Partially for that reason, I just put coilovers on the car last week, but left the torsion bars there.[/quote]I've also heard of people sanding down the splines (making it useless) and putting the torsion bars back in -- just to comply with the rules.

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[IaAaron]

at that point you would have to run the bearings that flash was talking about, thus proving to the tech inspector that your torsion bars are useless. Therefore might as well not have them at all. Unless they just dock you because of the marginal weight savings?

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[wjk_glynn]

[quote name='flash' post='57362' date='Aug 5 2008, 06:39 AM']...there are things you have to do if you delete torsion bars:



the rubber bushings in the torsion tubes have to be replaced with solid ones - the rubber cannot hold the control arm still without the torsion bar



you must run spherical bearings top and bottom on the shocks - again, rubber or polyurethane will not support the entire load



hope that helps[/quote]



Hi Flash,



Do you know sources for:



* Solid torsion tube bushings

* Top and bottom spherical bearings



The reason I'm askind is that GC sells a reasonably priced Koni based strut/rear-coilover kit ($1,900), which they say can be run without rear torsion bars -- and I'm kinda interested...



Photos of the GC product:







Karl.

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[flash]

i'm familiar with the ground control stuff - i've done business with them - certainly the more affordable setup - like most of what is out there, i don't like them because they are gas, and have the inherent jittery ride issues, but they do fit - i much prefer hydraulic stuff - not so sure about the rears being up to the job of full support - i am pretty sure those are limited to additional load bearing and not full load bearing - i've spoken to them before about this stuff, and i'll look into whether or not any changes have been made since then



elephant racing makes the torsion tube bushings that i prefer - i've tried the delrin ones, and they make noise and don't move as smoothly - rs barn sells both



the spherical bearings are an issue - they are not available in metric sizes - this requires either a modification to the car, or a custom part, which would be part of the kit we are looking into producing - i have to look into the bushing ground control is using on the top of the shock to see if that is up to the task

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[wjk_glynn]

[quote name='flash' post='57631' date='Aug 9 2008, 09:41 AM']i'm familiar with the ground control stuff - i've done business with them - certainly the more affordable setup - like most of what is out there, i don't like them because they are gas, and have the inherent jittery ride issues, but they do fit - i much prefer hydraulic stuff - not so sure about the rears being up to the job of full support - i am pretty sure those are limited to additional load bearing and not full load bearing - i've spoken to them before about this stuff, and i'll look into whether or not any changes have been made since then



elephant racing makes the torsion tube bushings that i prefer - i've tried the delrin ones, and they make noise and don't move as smoothly - rs barn sells both



the spherical bearings are an issue - they are not available in metric sizes - this requires either a modification to the car, or a custom part, which would be part of the kit we are looking into producing - i have to look into the bushing ground control is using on the top of the shock to see if that is up to the task[/quote]



Thanks for the info. I'd forgotten about Elephant Racing... and they're only 3-miles from my house. So I'll give them a call.



I'll double check again with GC regarding the ability of the rears to do full support. When I spoke with them on Friday, they specifically recommended ditching the torsion bars, which reduced labor costs, though you pay extra for the bushings/bearings.



And if I don't go with GC, I'll spend the extra and get the KW V3 (roughly $1,200 extra when you factor in the increased parts and re-indexing the torsion bars).



Karl.

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[wjk_glynn]

I just gave Elephant Racing a quick call and they also do installation work.



I'll give them a visit during the week.



Karl.

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[flash]

yeah - i like chuck's stuff, though i am still having a problem with a persistent squeak on one of the torsion bushings - not nearly as bad as on the delrin ones though - i've taken it apart and refitted it twice with no success - i've had an article in the works for a long time on the conversion, but have wanted to nail down the cause of this squeak first - everything else of his has been flawless and a very nice improvement



do a lot of homework on this though before jumping in - it's hard to go back



i seriously recommend staying away from anything gas in the rear - you would be amazed at the difference and improvement of hydraulic over gas - having now done the conversion on 2 cars, using 2 variations of the hydraulic shocks, i would never consider gas back there on anything, coil helper, complete conversion, or even just a shock - it's that big of an improvement in feel and control



if you are stuck on this setup, and i know the price tag makes it hard not to be, check out a few things first:



i'm not sure that the shock they are using can handle any decent spring rate without getting bumpy - check into the max spring rate - also realize the the effective rate desired requires a much larger spring (i.e. to get 250 you need 400) - they may or may not be able to handle what you want



it absolutely must have independent compression and rebound adjustments to attempt to quell the nasty problems of gas shocks, (problems like the koni yellow sport shocks have, even on stock spring rates)



both ends of the shock must be solid bearings - no polyurethane, rubber, or anything else will hold up under the increased loads of torsion bar deletion - it looks like they sleeved solid bearings, but check to be sure



i'm also not sure if the threaded collars rest on a welded stop or not - i don't see any, and without them, or some other way of permanently holding the collar still, the collars won't hold full the load of the car, especially with a stiff spring



there is also no offset assigned to the upper mount of those shocks - that is a necessary component of such a conversion for appropriate geometry and clearance, especially if you plan to lower the car a lot - bilstein and koni both did this on their setups for a very good reason - you can get away without it, but it lines things up better with it



food for thought - good luck

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[wjk_glynn]

You mentioned installing hydraulic versions on two cars. Which brands/models did you use?



Thanks.



Karl.

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[flash]

i've used 2 different models, in different setup applications - but, they won't work though without our kit, and i'm not sure we are going to produce it or not - depends on demand



huge improvement though - much smoother absorbing of spring deflection, due to the lack of the gas preload - about a 600lb absolute spring max though on a car with torsion delete, and about 350 absolute max with stock torsions - after that the compression is unable to keep up and they start feeling like koni yellow sports, bounding and jarring you all over the place

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