Hotshoe

Anyone here have any first had experience with this?

http://www.kokeln.com/rear_suspension_kit.php

I'm getting back into my project car and this sparks my interest to go with the Motons.

MAGK944

I was always skeptical about this piece. If I remember correctly it was priced quite high, I don't even know if anyone stocks it anymore. Says it saves you 25#, but I cannot see where? Maybe from a stock set-up with t-bars fitted(those t-bars weigh a ton),but not from an already converted coil-over set-up, probably a little weight saved but it is low down in the chassis so will be negligible. The lowering the roll center also didn't make much sense to me. Simply lowering the car would lower the roll center, if anything this would make the roll center move towards the rear of the car, which is really not what you want to do. Would be interested in any real world experience though.
-Mike

schwank

From the looks of it, you lose the banana arm in the rear as it is no longer necessary. I assume the housing is also much lighter overall, in addition to the torsion bar delete itself. Together I bet that would be 25 lbs, though it is such low weight I can't see it changing the roll center.

M758

what that does is really two things.

1) get weight out by removing the heavy and now empty torsion bar carrier. There is the weight savings and 25 is alot of savings once you already have done the easy stuff and have the car in FG body panels.

2) improves the suspension geometry for lowered cars. One issue I have with a really low stock suspension is that getting the camber & toe settings were you want them can be hard. It is easy to max out one or more adjustments. I have always been able to get what I want, but it is harder than normal and thankfully they tend towards settings that I want inthe first place. Also I have never really determined how the suspension reacts at thise lowered angles. For my purposes the benefits of lowering over ride any issues with less than optimal geometry, but maybe with this thing you can get better geometery and be much lower and save 25lbs on top of it all.

944J

my guess is that you are lowering the start and end points of the spring travel so its got a 1" lower overall location than what is possible with a stock setup, hence you might have a lower stock setup, but you can go lower with this part than you can with the stock... does that make sense?

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1 is stock

2 is this part

M758

No it does not for the 944 rear suspension.

My rear is lowered consierably. I am limited not by springs (or t-bars since I still run them), but the distance of the trailing arm to the body. There have been a few times I have had the the trailing arm hit the body when going off track. I can tell from the marks. If I go any lower I could be bottoming all the time. This is purely a result of the clearance from the trailing arm to the body. This does not change relationship, but chaning the forward positin of the spring plate you keep it close to the stock angle. thus when it moves it may have a better camber curve and may improve the roll center.

so a car with this suspension is not going to be lower, but that rear suspension may allow it to work better in turns and over bumps creating a subtle handling advantage.

944J

its lowering the "comfortable" center of the spring without lowering the car is what i'm saying...

M758

There is no "comfortable center" of a t-bar. To lower you remove and re-index. When it comes rear coil overs the spring will compress based on its rate and the weight of the car. As such it always finds is center. to raise/lower you move one end of that spring up/down.

The only things that changes it center are the suspension arm angles and the shocks.

944J

i'm just learning about suspensions so don't take what i say as comming from someone knowledgeable...

they didnt state that they changed the tbar mount except to make it a solid mount... they just said that they raise the mount of the spring...

is the spring the same as the tbar? i dont think it is...

the only thing changed, according to them is the "pivot mounting points of the spring plates"

MAGK944

I am still not convinced about the weight claims on this piece. A stock t-bar housing without the bars and with the banana arms ground off (i.e: set-up for rear coil-overs) is 25#. The spring plates add another 10# for a total of 35# (see pics below). If this piece saves 25# that would mean it weighs only 10#.

The suspension geometry changes now make sense to me, thanks Joe P. Maybe that alone would be a good reason to get this piece. I have seen a few vendors list them but none actually stock it. The other factor would be the price.

M758

Yes the raised the front piviot point of the spring plate. I am pretty sure they would have also raised the forward piviot point in the trailing arm as well. Raising both of these will not allow you to run lower, but they will ensure the arms are closer to their normal angle to ground when the car is sitting at lowered ride height. This the geometry these arms swing though is close to stock and proably superior to a "slammed" regular suspension. However the GC of the car is still the same as is over all ride height. In fact CG may increase if you take away 25 lbs down low like this. So while overall weight will be down the CG may be higher. Even so I am sure this part will make a very light and well optimized race car faster. How much so depends on how well the driver/shop can take advantage of the these improvements.

For a street car it is all about bragging rights and for most track cars the same. I am not allowed to use something like this in my class, but if I did I would make the car faster, but only if I could tune the car to take advantage of it. My guess is just replacing and bolt it in I would see either no change or an increase in lap times. I would need to test and tweak to see any gains.

M758

Yeah thanks for the info on existing weights. Ha maybe they are adding the t-bars so the 25lbs is compared to a t-bar car.

In the end however 25lbs in this location on the car is actually very good. Low and to the rear so if you have a min weight in the class this is a good place for it. Now in a weight no object class even a 10lbs savings would be nice. I do think all the "performance" comes from suspension geometry. One reason tube frame race cars are fast is that their geometries is optimied for their low ride heights this the suspensions work better. Street cars are optimized to run a street car height and while most run better a lower the optimization of suspension goes out the window lowered. In some cases too low makes the car handle very poorly. For the 944 you pretty much can lower the car and only need to prevent bottoming and the car is still faster than raised up. However if you have the money and rules allow it re-optimizing the geomertry is really the way to go. Factor GT3 RSRs are faster in part to due better geometry as compared to street GT3's or even GT3 cups.

Hotshoe

A lot of great points here that reinforce my concerns as well.

Other than a geometry improvement for the suspension I don't see a great weight savings. I also have my tbars removed and as shown on the scale the housing isn't that heavy. Now if it greatly improves the suspension and setup that's a different story.

I'm not convinced it's worth all that coin yet.