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Need help determining ride height- Please help...

 
Old 10-25-2001, 12:06 PM
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Robby
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Post Need help determining ride height- Please help...

Hello everyone!

I'm trying to find out several things:
1) Ride height for a stock US 951, and various Rennlister's modified ride heights?
2) Clearance of chin spoiler at LOWEST point of stock 951 (stock-?/modified-?)?
3) The difference in ride height for the Euro 951 (if any), and how it LOOKS?

I'm planning to upgrade my suspension soon and am having several problems. First off, I know it's a lot to ask, but can any of you guys out there take a couple of minutes and measure the ride height your cars (either stock or modified)? To keep everything consistent, please measure through the center of the rim, from the ground to the wheel well arch (this should basically be the apex). Mine are:
LF- 25 1/4"
RF- 25 1/2"
LR- 25 5/8"
RR- 25 3/4"

If you've gone through this much trouble already, please take a quick look at the front spoiler, and see where the LOWEST point is (height). Mine's ~4 1/4" off the ground at it's lowest point, and I scrape lot's of things- I'm afraid that bringing my car down 1" would be WAY TOO LOW. Anyone know if it's possible to raise the rear edge of the spoiler a tiny bit? I'd like to lower the front about 1/2", and the rear about 1", while getting the rear edge of the spoiler off the ground about 1 more inch...

Thanks for any help anyone out there can provide, and thanks a million to anyone who takes the few minutes to actually measure their wheel wells & spoiler... I REALLY APPRECIATE IT!!!

Thanks,
Robby
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Old 10-26-2001, 04:03 AM
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Hans
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mine is '86, stock condition

L-F: 645 mm (25,39 inch)
L-R: 658 mm (25,91 inch)
Tire size front 205/55R16 - rear 225/50R16
Car is "mothballed" at the moment, cant get to the right side or at the front spoiler at the moment
hope this helps
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Old 10-26-2001, 08:49 AM
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Robby
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Yes, thank you Hans. I appreciate anyone going through the trouble of measuring for me- even though it's not really that difficult, but, it still takes a few minutes to do. I've received one other measurement- your's is about 1/10" taller than mine, and the other's about 1" lower. I'd love to get the spoiler measurements at the lowest points, so if you get a chance to check it, please do

I'd love to here from someone who's lowered theirs a lot (1" or more) so I could get some specific measurements, AND find out how much spoiler clearance they have... The Euro's rear's were supposed to be 1" lower than the US rears. I'd like to find out what the front to rear relationship was there when they were new, and see how they looked, so I could decide how to set mine- I'm thinking prefectly even- flat... B/t your's, mine, and the other, the rears are about 1/2" to 3/4" taller than the front's...

Thanks again,
Robby
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Old 10-26-2001, 12:09 PM
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Rob
Mine is Euro spec.

I'll see if I can get under it for the front height in the weekend.
Front shows some "battle scars" but we'll see.
Let you know on Monday.
Have a nice weekend.
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Old 10-27-2001, 01:03 AM
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Cool

Here's my 2cents on ride heights.
Note that since I wrote this the rear seems to have settled another 3/8 or so. It's really too low. I scrape the black trim piece in front of the rear wheel every time I drop a wheel into the gutter. Also, my camber is about 2degrees neg. If I was doing a lot of autocrosses as intended, I would be fine, but too much home remodeling has about ended this season. So, all I get is a lot of tire wear. Anyway, here is my web site on my torsion bar and height adjustments.

Dans ride heights fun

DanD
Looking for M030 or helper springs so I don't have to reindex again.
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Old 10-27-2001, 06:15 AM
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Robby
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Dan,

What type of spring rates are you runnig? 25.5 t-bars just sound kind of small(?)... From what you're saying then, it sounds like the rear is definately too low, but I still haven't been able to confirm the Euro's ride height. Hans' heights are the same proportion as everyone else's I've heard about in the US (even my own), and I've always read that the Euro's were supposed to be 1" lower than the US- this would put the rear about 1/2" lower than the fron if it compared to the way everyone elses's are showing, PLUS, everyone's car seems to be pretty far off side to side like mine... I'm sick of this stuff... I want to add some 27mm or 28mm hollow t-bars and some 250lb LINEAR springs, and all the misc bushings, and be done w/it. I would do sways later... As for the t-bars, I think I'm going to adjust the external setting down pretty far, so that when I index them, if it drops a little like Dans, I can just dial the external back up- HOPEFULLY!!!

Does that sound like it would work???

Thanks, Robby
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Old 10-27-2001, 11:36 AM
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Robby, be careful in measuring to the wheel arches. Not unusual for the body work to go on a little different from side to side since the main objective of the builder at that point is fit and finish, not holding to some true dimension. Ever tried putting in cabinets in a house? Nothing is ever square or straight.

I have been told that the door sill is supposed to be level. Put a level on that to check front to rear height and I think you will see the rake of your car. Also, the real measurement point for rear ride height is from a suspension/frame point to axle center, not the fender to ground. Everyone uses fender because it is much easier. And of course it matters what sort of tires you are running and front to back differences, which also could explain some of these hight measurements people are reporting. I think PCA allows a minimum for fender to ground of 24 3/4". Or 13" from fender to wheel center.

And this story about raising the rear for US bumper laws is so wide spread and accepted there must be some truth to it. But maybe in actual build the tolerances were such that for some vehicles there wasn't much difference. And after US tests were originally passed, no one probably cared about keeping the rear high. It is a worthless bumper anyway with so many high bumpered vehicles on North American roads.
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Old 10-27-2001, 02:09 PM
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Hello again Sharkman...

EXACTLY....

What you said....

The tolerance differences etc, along w/stress causing differences in unibody structure, dif size & brand tires, worn out tires, etc, etc, etc...

I'm using the wheel arches for simplicity, and, most people should be running the same size tire. Rolling diameter's (RD) are
225/50/16= 24.86" **Stock Turbo**
245/45/16= 24.68" **Stock Turbo S**
245/40/17= 24.72"
255/40/17= 25.03"
These are all w/in ~3/10"- the only real difference should be when someone runs a completely different size, like a 255/55/16 or 255/45/17, or get's into the 18" range where the RD is harder to match... I'm more concerned w/what people's proportions are like front to back, and, especially side to side... I'd really like to know what the Euro height was SUPPOSED to be NEW. If I can just get a few people to take the time to measure their's, I can at least get an idea as to where mine should be...

The level idea sounds like a good one- I'll have to try that out. I think my rear should probably come down ~1/4" or so, but I'd still LOVE to find a way to get that spoiler up a tiny bit (maybe 1"), then, I could lower the front ~1/2", the rear ~3/4", and still have ~1/2" more clearance than I have now- NICE...

One other thing- the under body panels- how many should there be? The R&T test for the original 951 said that's how they lowered the drag from the 944 (.35) to the .33 of the 951- by adding an underbody pan closer to the rear. It said they added a "fanny pan" and kept the front one. Since this helped that much, reducing Cx by .02, even though the 951 got wider tires which hurt the Cx, I'm wondering if it would be worth it to find a way to make a larger section to cover up the whole underside of the car, or at least a little more of it. Maybe a light-weight panel of carbon fibre(?). I wonder if this could be bad in any way, other than being one more thing to remove when working under the car(?). I believe Nascars have underbody panels, and they seem to work fine, but it could depend on how it's designed(?). I know that's one of the reason's for the C5 Vette's ultra-low Cx (.29)- they designed the underbody stuff to be almost perfectly flat- it's kind of cool looking too. I wonder if anyone's tried this on a 924, 944, etc(?)...

Thanks,
Robby
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Old 10-27-2001, 03:29 PM
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Robby, I would just call Porsche and see if you can get someone to dig up original ride height and ground clearance dimensions. Maybe a frame straightening/wheel alignment shop may have the height specs.

I don't know if all this really matters though because it is ground clearance for your street driven car and what sort of roads and driveways you have to live with that will call the shots.

You do want a slight forward rake to the car, BTW.

Your car should have 3 belly pans which would include the short chin one that you have apparently chewed up. Now this is off the cuff, but the chin pan is the one that suffers on a sharp slope change, however, I'm not so sure it is the low point on the underside - you have your oil pan down there, remember. It would be a bitch to hit something with that.

And if you are going to try and reform the chin pan to ride higher you may still have the transition angle problem for your driveways. And you need to keep the air flow correct for the open space where it meets pan #2.

As far as this "Fanny Pan", I think you must be talking about the rear 2 piece fairing under the car by rear bumper - I know that reduced resistance. I would say forget it about adding additional pans, who knows how much drag cut you will get without a wind tunnel and you have to keep things like the exhaust and transmission cool.

So I would find out original ride height specs, crawl under the car and measure clearance heights, then make your decision about how low you want to go and forget all these crazy ideas about refairing the underside.
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Old 10-27-2001, 06:56 PM
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Robby
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Jaws,

Thanks for the info about the pans- what you're saying means the chin spoiler counts as one- this is the absolute lowest hanging part of the car which dictates clearance. The furthest back point, in the center of it, is the lowest part of all. I'll have to look for the rear peice you referred too...

As for making larger underbody panels- I'd have to get the car off the ground to really get a look, but I'm sure that more of it could be covered up- you're right about having to use a wind tunnel to maximize it and/or find out the resulting Cx, though. I wasn't really seriously considering it- yet. I hit a re-tread a year ago, and it banged up the underside- Garrity helped me out by fixing many of the parts, and replacing many w/used- I told you about the situation. The panels are still all bent up- I'd eventually like to replace them, but I'm also putting my car on a diet (951's are heavy), and would like to make the panels out of carbon fibre or something to save weight. I'm sure this could be done as easily, or maybe moreso than making body panels out of the stuff. I'd like to learn to work w/it myself... If I could get the panels re-made (do it myself?) I was thinking- "how much harder could it be to close up a little more of the underbody area?" But, it's not going to happen any time soon, if ever. For now, I have WAY TOO MANY other projects to finish...
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Old 10-27-2001, 09:22 PM
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My LR is at 24 3/4". The LF is at 25 1/2". I always thought mine looked low in the rear - so much so that I've been looking for a way to raise the back. I have all the records from the PO's, but I can't find any references to lowering the ride height. Personally, I think the cars look better with a slight rake to them (higher in the back) - but it's all in what you like. Might be that early 70's upbringing trying to sneak back in - Hijackers and such.
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Old 10-28-2001, 07:02 AM
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Robby
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Keith,

thanks, and I have to agree that when the rears start to sag, they look kind of funny. That's one reason why I'd like to know about the ORIGINAL Euro height- these cars have defintely changed a lot over the years. I plan to call some dealers tomorrow (MON)... Do you know if the other side's off by the same amount though? It's possible that the right side rear is the same, or even lower than the RF, and is causing it to rake in a funny way(?). Evidently, there is more to this than the wheel well arch measurements, as people have pointed out. I knew this from the beginning, but didn't realize it would make as much difference as it might be...
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Old 10-28-2001, 11:00 AM
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Right sides a bit more difficult to get at right now. I've have the intake pulled to replace the gaskets (MAJOR vaccuum leak point). Anyway, I think I can pull the numbers if I stand on my head and hold my tounge just right...
I'll let you know later today.
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Old 10-28-2001, 11:16 AM
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I see...

I wondered why you only mentioned one side... It's not that big of deal, so don't hurt yourself trying to get to it Thanks for your efforts...

Robby
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Old 10-28-2001, 11:45 AM
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Robby, I went and measured mine, discovered that the tires were low on air, went and got air and wound up measuring my arches 3 times on slightly different slanted concrete at the gas station. The measurements on the same wheel varied up to 1/2"! First time I measured all were 25 3/4 except for RF which came in at 26" even. With retests the wide measurements came in with a low of 25 1/2 and high of 26 1/4.

All were basically 25 3/4". I have larger and wider tires than OE which have a rolling radius which is higher by 0.2" in front and 0.5" in rear. My current static load radius with 5/8ths tank of gas is 11.5" front and 11.7" rear. (I think what Bridgestone is putting out is the loaded radius, squish if tire on ground, which is different than just the diameter of the tire divided by 2.)

What does this all mean? My rear ('88TS) isn't raised if you go by wheel arches. And it makes a difference if you are not on a flat surface. With a tire that is nearly 11" wide (275mm) the inside can stand on a higher spot than the outside. Plus it was about 32F so things may have been a bit stiff and sticky. Then there is weight shift due to vector angles.

I'm probably about an inch high all around and if I decide to lower I'm sure going to bounce things around and take miltiple measurements to see where things shake out.
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