Oh the shame, my 911 rides too stiff

Deschodt · 04:46 AM

Never thought I'd post something like that, but there you go, I think it is needlessly stiff... As in bone jarring yet not handling any better... The car's a backdated 83, so that opens a few possibilities for causes...

- the shocks are new bilstein HDs I believe, less than 5 months old.

- the torsion bars should be stock circa 1983, yet the car lost at least 200 lbs between fiberglass exterior bits and lighter interior - still it did not "go up" in stance as bits were removed, like Joe's car did. Is that a clue ?

- It is fairly low, but it has the bump steer kit (see exhibit 1)

I wonder if my mechanic may also have screwed up the last corner balancing - I'm losing faith in the guy of late...

- The real annoying thing, while it's really stiff and rough in terms of dealing with bumps and potholes, it still leans like the titanic on track... See exhibit 2.

That said it "feels" stiff but if it truly were, shouldn't it "fly" over bumps, instead of crashing roughly ? ( I think there is also too much nose dive under braking, I "rub" the tow hook at the front at particualr bumpy corner under braking, that's not right....)

Where do you advise I start ? I've given up on the idea of using this as a track car, it runs too hot and too slow anyway. My goals would be to have it corner a little flatter if possible - on general principle - without compromising the ride further, and have the suspension be more compliant over rough roads. I may start by raising the car a little, it may be too low for the shocks to "work"... So you think my torsion bars could be damaged or worn out ? Are there tests to help diagnose this issue ?

T77911S · 02-05-2009, 04:39 AM

mine is very harsh too. i assume it has been lowered to the bump stops even though it does not look that low, i need to check the ride height.

Deschodt · 02-05-2009, 04:47 AM

Could be, is there a measurement re:bump stops, something obvious I could check for ? Pictures would help, I'm a tool when it comes to suspension....

elpresidente · 02-05-2009, 04:55 AM

Stiff or not, that is a beautiful car!

RetroSC · 02-05-2009, 06:07 AM

Looks like it has quite a bit of roll, and if the torsion bars are stock I'd start looking at shocks. Poorly matched shocks and spring rates can make for some funny handling. i.e. really stiff shocks and weak springs would give a bone jarring ride but still let the car roll over in turns.

Deschodt · 02-05-2009, 06:28 AM

I thought Bilstein HDs were fairly "stock" for an SC... I'm thinking bump stops, height issues, that sort of things...Would worn out bushings contribute too ?

safe · safe's Garage

Quote:

Originally Posted by Deschodt

I thought Bilstein HDs were fairly "stock" for an SC...

It is. Your torsion bar / shock combination should not be the problem. Have you compared your cars ride with other 911s?

What profile tires do you have? What pressure?
Overinflated lowprofile tires are very unforgiving over pot holes etc.

What kind of bushings do you have.

Deschodt · 02-05-2009, 06:59 AM

Quote:

Originally Posted by safe

It is. Your torsion bar / shock combination should not be the problem. Have you compared your cars ride with other 911s?

What profile tires do you have? What pressure?
Overinflated lowprofile tires are very unforgiving over pot holes etc.

What kind of bushings do you have.

Everything's stock, the pictures show 16" superlites but the car is actually on 16" fuchs most of the time with stock 205/55/16 and 255/50/16s... Pressures are around 31/35 in general... It's substantially "rougher" riding than my neighbor's 79 targa (but maybe the targa flex provides some suspension give), also much rougher than my previous 73.5 911T but that may not be a correct comparison.

Like I said what gets me is how rough it is yet how loosely it leans. seems like a contradiction there...

schoward · 02-05-2009, 07:44 AM

I have fresh bilstein HD and newer stock t-bars on my SC and it is fine. Stock comfort you would expect.

I would experiment with tire pressures. Even just a few pounds (especially in the rear) make a noticable difference in my ride (stock fuchs and tire sizes). I actually prefer a little less than spec 34 lbd in my rear tires. Makes a noticable difference in ride comfort when putting around town.

Superman · 02-05-2009, 08:37 AM

Wonderful color!

My guess is bump stops. Your shocks and t=bars should not be causing a rough ride. Also, tire sidewall stiffness matters.

I prefer a stiff ride, but I also expect the leaning to be minimal.

Superman · 02-05-2009, 08:38 AM

One more thing. I think shocks are tuned to a ride height. That is.....they are somewhat compliant AT ride height, but when a wheel becomes compressed the shock gets stiffer. If you lower a car, the shock is stiff AT ride height.

MotoSook · 02-05-2009, 08:45 AM

Off the top of my head, I think your tire pressure cold for street running should be 28/34. But with 16" tires, your reported pressures shouldn't make the ride quality so bad.

Your ride height looks fine. Although you say your HD's are new, I would suspect they my be causing your jarring feel. What about the bushigs? Any work there? Even at your ride height, I wouldn't expect the bump stops to be an issue...unless you packed two sets in each shock....

Since you've done nothing to the spring rates (bigger t-bars) or sway bar why would you expect your body roll to be any better than stock? If you suspect something is not right, check the sway bar mounts. Those tend to tear from the chassis.

joe payne · joe payne's Garage

It doesn't sound like alot of crazy make the suspension super stiff upgrades like I read about, but you may want to upgrade to Carrera sway bars.

The sway bars need to come out of a 86 Carrera. I'm not sure where the cut off year is but at least from an 86. Have them installed with new rubber bushings, not the rock hard urethane ones.

Try reducing your tire pressures to 34 rear and 29 front and have the car corner balanced from a good reputable shop.

I have 30 year old Bilstiens in my car, stock torsion bars, and Carrera sways with 7 and 8 16 inch Fuchs, lowered, and missing 200-300 lbs. and it rides perfect.

Bye the way nice looking ride!

Dick Shift · Dick Shift's Garage

It's been my experience that bilstein HDs start off life very harsh and soften up after a few months.

Deschodt · 02-05-2009, 09:41 AM

Quote:

Originally Posted by Dick Shift

It's been my experience that bilstein HDs start off life very harsh and soften up after a few months.

Could be... I forgot to say that I've owned the car for 10 years or so, and it wasn't that stiff before the latest round of new shocks, ride height, corner balance... I hate the thought of raising it as it is not THAT low... I hope that's it, but I'll try playing with pressures first.

911pcars · 02-05-2009, 10:02 AM

Quote:

Originally Posted by Superman

One more thing. I think shocks are tuned to a ride height. That is.....they are somewhat compliant AT ride height, but when a wheel becomes compressed the shock gets stiffer. If you lower a car, the shock is stiff AT ride height.

You're describing a rising rate shock. I don't think so as long as the ride height isn't so low the shock is bottoming out.

If the shock rod sits an inch further in the housing, it should produce the same bounce/rebound rate as at regular height.

However, you could trim the bump stop just to give the shock some additional range, especially with stock torsion bars.

The Bilstein HDs are known to be stiff. In fact, many owners use HD's in the back and regulars up front. Check the archives to confirm. There should be tons of threads on Bilstein HD shocks.

As others have suggested, the front end should be upgraded as a unit so all parts are complimentary. Upgrade the torsion bars along with upgraded shocks. For more street use and less track duty conditions, around 21-27 frt/rear will give you a slightly firmer ride and less body lean without having to resort to large dia. sway bars. Large SBs will actually degrade ride characteristics as much as the HD Bilsteins on an otherwise stock front end.

Sherwood

vintage guy · 02-05-2009, 10:06 AM

I replaced the old worn out Boges on my '87 and with no other changes the ride and handling improved noticeably. I would not say my ride is stiff at all. It is comfortable and compliant for street driving but works well at speed. My car is lowered slightly. Sounds like there may be some problem.

vintage guy · 02-05-2009, 10:07 AM

Meant to include that I switched to Bilstein HD's.

RWebb · RWebb's Garage

check Ptire first,

but your symptoms point to old, hard rubber bushings, or the nasty polygraphite ones....

FPB111 · 02-05-2009, 10:32 AM

Measure the height of your fender lips. Measure on level ground from the ground through the wheel center to the fender lip. Much lower then 24 3/4"F - 25"R without raising your spindles will start to compromise your suspension travel.
Let us know what those numbers are. (OK guys I know this is not THE PROPER way but it will give us an idea where he is)

What diameter sway bars do you have? If you do not know take a metric open end wrench set, start at 22mm, fit around the sway bar and work down until you get to the tight one. Let us know what you have. Did you put adjustable arms on the sway bars? If so how far out from the center of the bar(s) are your drop links mounted?
Sway bars or very stiff torsion bars are the only things that will help stop the lean ( or dropping the suspension down until there is no travel)