Need 951 Suspension Advice... autocross/street setup
#31
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Originally Posted by ninefiveone
Are you alright? Lots of rage and anger. I know the history of the 917 very well. Actually I know the history of Porsche really well, too. I can talk all day about any of those guys if you like. Do some research on the 917 and it's development. It's a really interesting story and while Andial has a place in that story, there's a pretty specific scope to it. If you want, I'd be happy to talk about it but not if you're going to have that kind of attitude. It's also completely irrelevant to this thread.
I've been doing this for years. owain, 333pg333, and porschefile are on target.
I've been doing this for years. owain, 333pg333, and porschefile are on target.
So you know about the 917 development therefore will know all about Ike Westerhausen then. He was one of the factory development test drivers back then. He now lives in Derbyshire in UK and campaigns a Lister Jaguar replica that nobody can keep up with. He must be way into his 60's but on short course, very little even modern exotics can keep anywhere near him. He is one of the most amazing development drivers I have come across. Just from a short drive in a car he can tell you exactly what is needed to make the car fast, more importantly he is always right down to quite fine tolerences too.
#32
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Originally Posted by 333pg333
It seems that many of us are forgetting the shocks and more importantly how they're valved. You can run high rate springs that will make life a lot of fun on the track but aren't teeth rattling on the road. It's just a matter of finding something that is more advanced than 20-30 year old Mo30 technology or similar to it. The days of stiffening up your suspension to go racing, but impossible to drive anywhere else are a thing of the past. Just do a bit of research and you'll find that some of us have their cake and they eat it too with lots of Ice cream! Or should that be Gelato, Rob? lol ![bigbye](https://rennlist.com/forums/graemlins/xyxwave.gif)
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#36
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Originally Posted by owain
I have 250# springs on height adjustable coil-overs on the front and 28 mm tbars in the rear with 968 M030 swaybars both. With 225 tires on the front and 245 tires on the rear and the rear swaybar set at the middle position I get very neutral handling bordering on slight oversteer. Very good for autox. It's also not at all harsh on the street. A good compromise, in my opinion.
Another setup I'd like to try is with ~300# springs on the front and the same size tires all around. A bit more front-end grip and hopefully similarly neutral handling. I have no experience with that, though.
As was pointed out you might want some lighter wheels for autocrossing. You can probably pick up some 8x16" sewer lids pretty cheap and they're a good strong light forged wheel. They're not very expensive 'cause they're ugly and no one wants them
. Unfortunately 8" is as wide as they come, but maybe you can find a couple of sets of club sports for a decent price which came with 9" wide rears and are essentially the same design of wheel. Set them aside until you can afford some r-compounds to put on them, then watch your times come down.
It might seem obvious, but sometimes it helps to put these things into words: a heavy wheel takes more energy to accelerate, and that's in all directions and states. More energy from the engine to speed it up and more force from your brakes to slow it down, but just as importantly more energy from your springs and shocks to arrest and deal with upward movement due to bumps in the road surface. All else being equal, the lighter the wheel (actually, the lighter the sum of the unsprung components) the suppler the ride and the more control over irregularities.
Good luck!![thumbup](https://rennlist.com/forums/graemlins/thumbup.gif)
Another setup I'd like to try is with ~300# springs on the front and the same size tires all around. A bit more front-end grip and hopefully similarly neutral handling. I have no experience with that, though.
As was pointed out you might want some lighter wheels for autocrossing. You can probably pick up some 8x16" sewer lids pretty cheap and they're a good strong light forged wheel. They're not very expensive 'cause they're ugly and no one wants them
![ooops](https://rennlist.com/forums/graemlins/icon501.gif)
It might seem obvious, but sometimes it helps to put these things into words: a heavy wheel takes more energy to accelerate, and that's in all directions and states. More energy from the engine to speed it up and more force from your brakes to slow it down, but just as importantly more energy from your springs and shocks to arrest and deal with upward movement due to bumps in the road surface. All else being equal, the lighter the wheel (actually, the lighter the sum of the unsprung components) the suppler the ride and the more control over irregularities.
Good luck!
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Sounds like you already have a similar setup to what I'm thinking of going with, but you'd like yours to be a little bit firmer in the front. Everyone seems to be saying that 300 lb springs won't be too harsh. I think I'm probably leaning that way now.
As far as the wheels go... I have early offset hubs, so the "sewer lids" won't work (unless I use spacers). As I said in any earlier post, I'll probably eventually use my stock 16" phone dials and put some good autocross rubber on them.
#37
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Originally Posted by SimonK
And i got to wondering what stock 951S springs are in lb?
There's a fairly complete table on www.clarks-garage.com with the stock suspension specs for all years, all types of 924/944/968. Click on the Garage Shop Manual link, and then the Suspsension Upgrades link, and it's about half-way down the page. Sorry, there's no direct link to this page.
Anyone know how to convert from N to lb, spring rate? Spring rate for 951 front springs is listed as 3286 N. I think it should be somewhere in the neighborhood of 160 lb, but not sure.
#39
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Originally Posted by cincy944
Anyone know how to convert from N to lb, spring rate? Spring rate for 951 front springs is listed as 3286 N. I think it should be somewhere in the neighborhood of 160 lb, but not sure.
Lbf/in = N/mm x 5.71,
So, 32.86 N/mm x 5.71 = 188 lb/in.
#41
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The info on Clark's page is incorrect (related to spring rates).
The factory info page listed above shows groupings/ratings for the tolerance groups - which are then paired and marked (the number of colored dots on the springs). Those are not the spring rates. The factory is listing the force it takes to compress the spring to a length of L1 (i.e. 251mm).
For the first part number shown, the first tolerance group (single yellow dot) is in the range of 3034-3150 Newtons to compress the spring from 396mm to 251mm long. So it takes between 3034-3150N to compress the spring 145mm. 3034/145 to 3150/145 = 20.92 to 21.7 Newtons/mm = 119 to 124 lb/in. I recall the nominal rate for N/A, S, and Turbo springs (non-M030) is 21.8N/mm which equals approx 124 lb/in.
The M030/Turbo S Springs are nominally rated at 28.0 N/mm, which is approx 160 lb/in. The actual tolerance groups shown are 27.9 to 28.9N/mm (160-165 lb/in) and 28.9 to 29.8 (165-170 lb/in).
The factory info page listed above shows groupings/ratings for the tolerance groups - which are then paired and marked (the number of colored dots on the springs). Those are not the spring rates. The factory is listing the force it takes to compress the spring to a length of L1 (i.e. 251mm).
For the first part number shown, the first tolerance group (single yellow dot) is in the range of 3034-3150 Newtons to compress the spring from 396mm to 251mm long. So it takes between 3034-3150N to compress the spring 145mm. 3034/145 to 3150/145 = 20.92 to 21.7 Newtons/mm = 119 to 124 lb/in. I recall the nominal rate for N/A, S, and Turbo springs (non-M030) is 21.8N/mm which equals approx 124 lb/in.
The M030/Turbo S Springs are nominally rated at 28.0 N/mm, which is approx 160 lb/in. The actual tolerance groups shown are 27.9 to 28.9N/mm (160-165 lb/in) and 28.9 to 29.8 (165-170 lb/in).
#42
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Originally Posted by SimonK
Thanks 4 the conversion Trucho-951. But 4 anyone who wants to know precisely... here is the confusion...
Lbf/in = 3286 N /(396mm – 251mm) x 5.71
= 3286 N/145mm x 5.71
= 22.66 N/mm x 5.71
= 130 lbf/in
Simon in your case:
Lbf/in = 3330 * 5.71/(356 – 241)
= 165 lbf/in
#43
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Nice... thanks for making sense of that. Sorry for posting a link to misinformation everyone.
Originally Posted by Oddjob
The info on Clark's page is incorrect (related to spring rates).
The factory info page listed above shows groupings/ratings for the tolerance groups - which are then paired and marked (the number of colored dots on the springs). Those are not the spring rates. The factory is listing the force it takes to compress the spring to a length of L1 (i.e. 251mm).
For the first part number shown, the first tolerance group (single yellow dot) is in the range of 3034-3150 Newtons to compress the spring from 396mm to 251mm long. So it takes between 3034-3150N to compress the spring 145mm. 3034/145 to 3150/145 = 20.92 to 21.7 Newtons/mm = 119 to 124 lb/in. I recall the nominal rate for N/A, S, and Turbo springs (non-M030) is 21.8N/mm which equals approx 124 lb/in.
The M030/Turbo S Springs are nominally rated at 28.0 N/mm, which is approx 160 lb/in. The actual tolerance groups shown are 27.9 to 28.9N/mm (160-165 lb/in) and 28.9 to 29.8 (165-170 lb/in).
The factory info page listed above shows groupings/ratings for the tolerance groups - which are then paired and marked (the number of colored dots on the springs). Those are not the spring rates. The factory is listing the force it takes to compress the spring to a length of L1 (i.e. 251mm).
For the first part number shown, the first tolerance group (single yellow dot) is in the range of 3034-3150 Newtons to compress the spring from 396mm to 251mm long. So it takes between 3034-3150N to compress the spring 145mm. 3034/145 to 3150/145 = 20.92 to 21.7 Newtons/mm = 119 to 124 lb/in. I recall the nominal rate for N/A, S, and Turbo springs (non-M030) is 21.8N/mm which equals approx 124 lb/in.
The M030/Turbo S Springs are nominally rated at 28.0 N/mm, which is approx 160 lb/in. The actual tolerance groups shown are 27.9 to 28.9N/mm (160-165 lb/in) and 28.9 to 29.8 (165-170 lb/in).
#44
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Also don't forget that the rear rates are not just the spring and the t-bar added together. There is a formula to use that will figure it out at the wheels. I have posted that before so I wouldn't want to upset the posting police, but with my rear springs being 50N and the t-bar 25.5mm, my rate comes out to 708lb/in. I'll let one of the other guys post why.
PS Rob, I love Italy, it's food and especially the Gelato.
PS Rob, I love Italy, it's food and especially the Gelato.
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#45
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Anyone know what this is about? Below is a note listed on the performance products website about the Weltmeister springs. Do I need spring spacers in order to put these springs in my '86 951? I will also be installing koni's in the front. Don't know if that makes a difference...
Tech Tip: * A note On 944 Springs. Because There Are Various 944 Front Struts, Some 944s Require Spacer Adapters To Install In The Bottom Spring Perth Along With Weltmeister Springs. 944s That Require coil spring spacers are all 1986 944 Turbo, and all 1987-91 944, 944S **Springs do Not Fit 944S2, 944 Turbo S Or Any 944 With Adjustable Spring Perches
Thanks again for all your advice!
Tech Tip: * A note On 944 Springs. Because There Are Various 944 Front Struts, Some 944s Require Spacer Adapters To Install In The Bottom Spring Perth Along With Weltmeister Springs. 944s That Require coil spring spacers are all 1986 944 Turbo, and all 1987-91 944, 944S **Springs do Not Fit 944S2, 944 Turbo S Or Any 944 With Adjustable Spring Perches
Thanks again for all your advice!