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Solid or Rubber Subframe Mounts

 
Old 06-26-2018, 11:23 AM
  #1  
nothingbutgt3
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Default Solid or Rubber Subframe Mounts

In order to update as much as possible my M.Y. 96 993 Carrera, I would like to update to:
- RS OEM monoball top mounts front and rear
- RS/EVO OEM front tie rods
- RS OEM uprights
- Elephant Racing Front Control Arm Sport Bushings
- Elephant Racing Front Control Arm Sport Bushings
- E.R. Rear Control Arm Sport Bushing kit
- E.R. Rear Toe Control Arm Eccentric Bushing
- Rennline Rear Spring Hat for PSS10 System

Then I would also like to consider changing the subframe mounts, either with solid or with rubber Mounts: pro & cons? I use most of the time my car for fun, i.e. trackdays (not races) or nice rides around tuscan hills and mountains, and surroundings regions.
What I do I to soften the PSS10 to 2/3 position front and rear when driving on the roads and put them on 9 when driving the car on the track: so far this way of setting the car is giving me enough comfort for the road and less roll on the track.
I am also considering to change the M030 Sway bars and Bushings with the RS adjustable ones.
This will have to be for me a late autumn/winter as much as possible D.I.Y. Job, so I know I have time, but I am starting to make considerations about what is better to do: my goal is to have hardware and set up as much as possible exactly the same as an original 993 RS, in order to create a clone.
Where possible, to have a better chassis hability, but without a big loss in drivability on the road.

The harder rubber I don't think will represent any loss in comfort, and furthermore, considering the bushings have already 22 years of life, replacing them with OEM would represent already an imporvement compared to now.
I already changed the motor mounts with the RS ones and I was one of the biggest improvements with any loss of comfort I have done so far, together with PSS10.

Now I am at a drive height approximately of 135mm front and I would like to go for OEM RS ride height 124+-10mm front and 107+-10 mm rear: better 114 and 100 or 124 107, any advices?

P.S. every time I see the car in picture it always seems too high: I think it's a sort of bodybuilder syndrome that always thinks to be smaller than he is while looking himself in the mirror.

Concerning ride height, I think it is a matter of compromise, because setting the car too low has its limits due to slow bumps and ramps: otherwise I wouldn't have any doubt.

P.




@Mugello Circuit

Last edited by nothingbutgt3; 06-26-2018 at 11:40 AM.
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Old 06-26-2018, 12:53 PM
  #2  
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From your list of upgrades done or to do, you are looking for a more performance oriented ride. My 993 has many of the items you list in addition to TRG swaybars (with delrin bushings), JRZ shocks front and rear, solid rear sub-frame bushings, hard transmission supports. For me what made a huge difference is 'Pinning' the front tie rods that takes out steering slop.

The car rides very nice, but taut, precise steering. Love it!!!!!
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Old 06-26-2018, 03:37 PM
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Bill Verburg
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Originally Posted by nothingbutgt3 View Post
In order to update as much as possible my M.Y. 96 993 Carrera, I would like to update to:
- RS OEM monoball top mounts front and rear
- RS/EVO OEM front tie rods
- RS OEM uprights
- Elephant Racing Front Control Arm Sport Bushings
- Elephant Racing Front Control Arm Sport Bushings
- E.R. Rear Control Arm Sport Bushing kit
- E.R. Rear Toe Control Arm Eccentric Bushing
- Rennline Rear Spring Hat for PSS10 System

Then I would also like to consider changing the subframe mounts, either with solid or with rubber Mounts: pro & cons? I use most of the time my car for fun, i.e. trackdays (not races) or nice rides around tuscan hills and mountains, and surroundings regions.
What I do I to soften the PSS10 to 2/3 position front and rear when driving on the roads and put them on 9 when driving the car on the track: so far this way of setting the car is giving me enough comfort for the road and less roll on the track.
I am also considering to change the M030 Sway bars and Bushings with the RS adjustable ones.
This will have to be for me a late autumn/winter as much as possible D.I.Y. Job, so I know I have time, but I am starting to make considerations about what is better to do: my goal is to have hardware and set up as much as possible exactly the same as an original 993 RS, in order to create a clone.
Where possible, to have a better chassis hability, but without a big loss in drivability on the road.

The harder rubber I don't think will represent any loss in comfort, and furthermore, considering the bushings have already 22 years of life, replacing them with OEM would represent already an imporvement compared to now.
I already changed the motor mounts with the RS ones and I was one of the biggest improvements with any loss of comfort I have done so far, together with PSS10.

Now I am at a drive height approximately of 135mm front and I would like to go for OEM RS ride height 124+-10mm front and 107+-10 mm rear: better 114 and 100 or 124 107, any advices?

P.S. every time I see the car in picture it always seems too high: I think it's a sort of bodybuilder syndrome that always thinks to be smaller than he is while looking himself in the mirror.

Concerning ride height, I think it is a matter of compromise, because setting the car too low has its limits due to slow bumps and ramps: otherwise I wouldn't have any doubt.

P.




@Mugello Circuit
Whether or not to use solid side mounts isn't a comfort issue, but rather more a ride height issue.

solid will be fine as far as comfort goes.

what the solids do is move the rear suspension up into the chassis helping to keep geometry on a very low car where you want it to be. I wouldn't use solids unless the car is below RS height
ie blow ~120mm front and 105mm rear

They do add precision to handling but it's very minor compared to what changing the horizontal bushes does.
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Old 06-26-2018, 04:03 PM
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pp000830
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For "rides around Tuscan hills and mountains, and surroundings regions."
I would replace worn rubber parts with stock stuff or street specified aftermarket stuff, avoid solid or stiff mounts on any points.
A street coil-over kit will improve handling while not making the ride annoying. Something like the H&R sport kit.
Replacing the stock brake hoses with DOT braided aftermarket lines will substantially improve the brake feel.
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Old 06-28-2018, 11:08 AM
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Tlaloc75
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You might find this thread useful: https://rennlist.com/forums/993-foru...monoballs.html
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Old 06-28-2018, 12:49 PM
  #6  
Knight
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Not sure if longevity is any concern, however the rubber will tend to last longer too. I replaced mine quite some time ago and went with RS rubber route.
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Old 06-28-2018, 02:41 PM
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il pirata
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If your going to use the RS top mount with PSS10's you will need a custom made shoulder nut for the front. I see you are already planning on sourcing the Rennline rear spring hat which is also required.

https://rennlist.com/forums/showthre...ferrerid=93689

You didn't mention how many miles are on your 933 or if you have already inspected the spherical ends of the control arms, these wear out as well. You might want to consider new arms .
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Old 06-28-2018, 04:53 PM
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Paul M
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Originally Posted by nothingbutgt3 View Post
In order to update as much as possible my M.Y. 96 993 Carrera, I would like to update to:

- RS OEM uprights
RS OEM uprights have been on backorder for over two years, you may have to consider an alternative aftermarket item such as 9M or BBi.
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Old 06-28-2018, 06:12 PM
  #9  
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I went for Rennline solid subframe mounts relatively easy to fit. The car is RS ride height with the front RS uprights ( had them a while). I had the nuts made fror the PSS10s with RS monoballs, the Rennline kit would have been easier. NVH is increased and the PSS10s do not like slow speed road imperfections.
This site is well worth a look. http://www.jackals-forge.com/lotus/
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Old 06-29-2018, 09:28 AM
  #10  
Bill Verburg
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Originally Posted by Knight View Post
Not sure if longevity is any concern, however the rubber will tend to last longer too. I replaced mine quite some time ago and went with RS rubber route.
How do you figure that these


will last longer than these
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Old 07-02-2018, 10:54 AM
  #11  
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You might find this thread useful: https://rennlist.com/forums/993-foru...monoballs.html
I read it all in one go ...

However, the Mugello is a real circuit, it has very different curves, uphill, downhill, parabolic, counterattend, fast, medium-fast, slow and was really useful to understand where to improve the car.
Now the car has M030 anti-roll bars: my intention is to make it a more track oriented car, but still with an acceptable comfort on the road.

I chose to improve aerodynamics with the RS aerokit, mainly for two reasons: because I think it is beautifully integrated with the 993 shape and because it gives some more downforce front and rear, without increasing the drag.
Putting the RS Clubsport Aerokit would be for a really only track oriented car, compleately naked inside, and necessairly with engine and gearbox upgrade, because the drag would definitely make the car faster in corners, but slower on straight.
So I chose the standard Aerokit as a compromise, just a little bit better downforce, but no loss in acceleration.

I am planning to put the car lower, which should improve a little bit the aerodynamics as well: now it is probalby around 135mm height, I plan to set it at 115/120mm.

RS OEM uprights have been on backorder for over two years, you may have to consider an alternative aftermarket item such as 9M or BBi.
I placed the order at a Local Porsche dealer and the ETA of the uprights is October 2018.

If your going to use the RS top mount with PSS10's you will need a custom made shoulder nut for the front. I see you are already planning on sourcing the Rennline rear spring hat which is also required.

https://rennlist.com/forums/showthre...ferrerid=93689

You didn't mention how many miles are on your 933 or if you have already inspected the spherical ends of the control arms, these wear out as well. You might want to consider new arms .
My 993 is a m.y. 96, unfortunately with G50.20 gearbox, even though the production should have been February '96: it has 117.000 kms, I already changed the front Control arms once 15.000kms ago.

Doesn't really exist a place where to buy the nuts for mating them to the front PSS10 and RS monoballs? I have a friend who can machine them, but is there any more precise detail on sizing?

I noticed that both the subframe and the rear bushings have gaps inside them, this probably to allow greater movement in a certain direction, a movement that the solid supports will obviously not allow.
Can it be a limit or is it an improvement?

The thing that pushes me to change the elastic elements at rear axle is that they are 22 years old and so they are definitely not definable "as brand new" anymore and the fact that when I push on the track I feel while cornering something like a moving engine effect, with a sort of step that changes the geometry at the rear all in a sudden, making, at least this is the feeling I have, to do the curve rounder, like if the rear axle is having a counter-rotation. (but for sure destabilizing the cornering, while cornering!).
And I must say that in slow corners maybe this effect can also be appreciated, because it helps to aim the nose towards the rope faster (without using the gas), but on the fast corners absolutely not...

I also sent an email to Elephant Racing already a week ago, asking for details, because I really don't know what to buy from their site and being based in Italy I don't want to experience a return from Europe to USA because of a mistake while placing the order, but so far I didn't recieve any answer. (maybe I wrote to the wrong email: [email protected] is correct?)

This is what I wrote them, so that you are aware of my doubts about it:
Good afternoon,
I am considering to upgrade the bushings of my M.Y. 96 Porsche 993 with RS bushings and I am having doubt about the stuff I need to place in order.
Please see the 2 attached images: while for the front the exchange parts are in the right number, for the rear the arm ends are 5, so I must change 5 bushings each side, but in the kit there are 6 (3 for each side) and than there is the eccentric bushing, so the amount is 8, not 10: am I missing someething?

Thank you in advance
Paolo




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Old 07-02-2018, 11:08 AM
  #12  
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When you replace all these bushings you will feel a huge positive difference. BillV has said it many times but for a primarily street-driven car, the RS hardness bushings are probably the best way to go. For a primarily track driven car, the monoballs are best. Either way, you will gain a huge amount of precision compared to where you are now. The movement you are feeling is probably primarily the KT effect that is getting a little sloppy due to old, worn bushings in the control arms. The toe arm takes a lot of abuse and is probably pretty loose, a-arm is probably not far behind.

I really like the feeling of rs sport hardness in all these bushings (along with new ball joints) but have to admit the monoballs felt really good too. Better than I expected when street driven. That was my point when sharing the thread, both choices are good. The road we drove is remote, with very few cars and some corners that allow near the limit cornering in third gear on re71r tires, in some of the corners. So its a good test. Not as good as a track by a long shot, but pretty good for a road.

As for solid vs bushings in the subframe, I think it comes down to how low you want to go. As Bill mentioned, the big difference is that the solid mounts pull the subframe up closer to the chassis. The bushings mount it lower. Either RS hardness or solid give a very stable platform, so the geometry differences may be the biggest deciding factor. The solids also have the benefit of never wearing out.



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Old 07-02-2018, 11:22 AM
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The difference in drag between RS and RS/CS @125mph(200kph) is dependant on the wing angle, 0░ it's 11# of drag9░ it's 14# of drag

As to the suspension if staying ~RS height ie ~124/107 +/- stick w/ the stock subframe mounts, if going lower use solids RS suspension is a fantastic setup for sporting street and some track. in back only the KT arm(#4 above) and trailing A-arm(#6 above) need the stiffer RS bushes. For more track use add a a mono-ball toe arm(#3).

in front only the trailing leg of an RS has stiffer rubber bushes but most add them to the leading leg too.
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Old 07-02-2018, 11:55 AM
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Originally Posted by nothingbutgt3 View Post
Doesn't really exist a place where to buy the nuts for mating them to the front PSS10 and RS monoballs? I have a friend who can machine them, but is there any more precise detail on sizing?
I am not aware of anyone who is making the nuts. As noted in my previous post with the link to ToSi's thread, the measurements are approx. and you will need to take the parts to the machinist to be exact.
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Old 07-02-2018, 01:46 PM
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in back only the KT arm(#4 above) and trailing A-arm(#6 above) need the stiffer RS bushes. For more track use add a a mono-ball toe arm(#3).

in front only the trailing leg of an RS has stiffer rubber bushes but most add them to the leading leg too.
So, making a summary, not to go wrong, I could buy and install the following parts:

- Rennline Solid Rear Subframe Kit and Tilt Kit

- 2 front Control Arm Front Bushing (sp. Hardness)
- 2 Front Control Arm Bushing (sp. Hardness

- 1 ER Sport Hardness Rear Control Arm Bushing kit (6 pieces, 3 each side), but the rubber attachment points to change are 5 for each side and in order to refurbish all the elastic parts (front and rear) I should also change the #5 and #3 bushing (above exploded parts): are the dimensions of each arm-end the same?

Because in this case I could have probably at least 2 possibilities, using the 3 bushings in the ER kit for the #6 and #5 (is this the camber control arm?), and then:

- either add ER rear Toe control Arm (#3) Eccentric Bushing together with Rennline Rear Kinematic Control Arm (#4) with Eccentric Locks

- or add Rennline rear toe control arm (#3) with eccentric locks together with Rennline Rear Kinematic Control Arm (#4) with Eccentric Locks

What do you think is best?

really have no idea: in the ER kit there are 3 sport hardness bushings for each side, so even if I add the ER Toe Control Arm eccentric bushings or the RENNLINE monoball toe arm, there is still one bushing missing.
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