924Board.org

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I'm finding my 924's handling a bit annoying.
Feels "unsettled" on rough roads / adverse camber corners.
Understeers and rolls a lot on tight low-speed bends.
Feels "bouncy" on uneven roads (and has done since I installed the new shocks).

Current setup:
Bilstein B6 shocks (Early 944 Type) less than 10k miles
23.5mm torsion bars
140 lbs stock springs
23mm early-style front roll bar
14mm rear roll bar
16" Tyres at 30 PSI all round.
Front ride height is slightly higher than rear, like 0.5".


I have an idea of what I should do, but I'm interested in the opinions of others. Let me know your thoughts?

[Mclaren924]

[morghen]

You need to do a proper geometry adjustment front AND rear.
Before that you should also make sure that all the bushings are fresh or at least in good condition. No perished/soft rubber.
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https://www.the924.com

[peterld]

+ 1 Morghen

You have just about the best shocks in the business; the sway bars are a good size, as are the torsion bars.
If you wanted the car to be a little more 'pointy' then upping the front spring rate to around 200-250 lbs and adjusting the rake to slightly nose down would help.
But as already stated, first check ALL mounting points: engine/shocks/sways/front suspension arms/rear suspension arms/gearbox mounts. Get a pry bar in there and check for movement.
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80/81 932/8 ROW

[Cedric]

I ran the same spring/anti roll bar setup on my n/a years ago and its very softly sprung, like door scraping soft in the corners if you push it fully on grippy tyres. less on shitty tyres of course, only way around it is upping the spring rate on the anti roll bars, springs/bars or both. However it should feel balanced.

I would also give the same advice as morghen, do a proper alignment, I wouldnt fully go by the book values. I would do neutral toe up front and add some negative camber, at least -1 degree to get the front en to grip up better in the corners. If you dont know how old they are you should probably at least change the front arm bushings(maybe upgrade), and check the rest of them aswell as the others said.

When you talk about ride height, where is it measured?
What tyres do you run on, same size all around?
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1980 924 Turbo
www.instagram.com/garagecedric/

[Raize]

Alignment settings (10k mi ago)
Camber:
0.75 degrees negative front
1.00 degrees negative rear
Toe:
0.15 degrees toe in front and rear

Bushings
All front bushings were replaced 10k miles ago (2 years). Rear torsion bar bushings were replaced but not the control arm bushings. They're all standard rubber bushings, no PU.

Ride height and corner balance
I measured ride height at the sills, it's about 150-160mm. The front control arms are level at this height.
I have not had it corner balanced and do not even know the corner weights.

Tyres and Wheels
Tyres are PilotSport 4 205/55/16 all round at 30 PSI, with 20mm spacers on the rear. Very very grippy, I don't even hear them chirp while I'm understeering.

I can't upgrade the front anti-roll bar because it's already the biggest available I'd have to go to the 944-style which I don't have mounting points for and would be difficult to add. I could install a thicker rear anti-roll bar though.

I don't want to change the torsion bars as it's too much work but I imagine any kind of stiffer front springs are not going to be appropriate with the standard torsion bars?

[/b]

[924RACR]

Doesn't sound like enough rear camber; from the book, seems like you want to be more like 1.5 degrees. Similarly, too much front camber, book says 0.25-0.5 degrees. Add that to nose up, instead of nose-down rake as mentioned, yeah, that's not going to help the car feel right.

Generally you don't want exactly zero toe in the front, you want a little in or out to take up slop in the chassis/bushings... but I prefer a hair of toe-out.

Yes, you could run more front camber, but on the street that'll hurt tire wear. The geometry of the rear needs/wants it, but the struts up front don't unless you're on the track.

Have you replaced strut mounts, ball joints and tie rod ends up front? I'd assume, based on what else was done, but best to not assume.

But that rear being too low is just huge in my book, that's really quite low, does really mess with the balance of the car; you really should get that back up where it belongs before redoing the alignment (because that will screw it up), anything else is just pissing in the wind.

If you don't want to raise the rear back up (as noted, maybe 1/4" rake, so the rear sills are 1/4" higher than the front, is ideal IMO) then you need to lower the front, either with lowering springs or adjustable race spring perches...
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[Cedric]

If it was my car i would have lowered it to sort out the rake, and just set more negative camber up front and see how it feels before doing any big changes. You wont notice any odd wear if you arent doing hundreds of miles on the motorway, ive done it on my daily gt86 aswell.

Are struts oem with bilstein inserts? Converting to an adjustment spring seat is fairly easy and very cheap. I did it on my previous setup, but lowering springs might be good enough. You can of course raise the rear, but the original off road ride height do look a bit funny

I don't remember the ride height numbers, my car is on jackstands atm. Around ca 33cm up front between the center of the wheel and fender edge works well, and a slight rake downwards. The rear is easily adjusted on the excenter, at least a bit, try adjusting it up and see how it feels.
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1980 924 Turbo
www.instagram.com/garagecedric/

[924RACR]

We run the racecar down at 5" at the sills up front(not including the pinch weld), 5.25" at the rear, by class rules... though I guess we could go even lower now that we've changed classes.

But that does put the front a-arms at unpleasant angles, so we just throw a ton of spring at it to keep things from moving.

For the street, not so desirable... I lowered the front of my 931 street car, but needed to keep stock spring rates because I live in the Detroit area, and our roads are worst than most of Europe (maybe excluding parts of the Ukraine? LOL)... definitely worse than the UK... cost a fair bit of coin to get those springs made to order from Moton/MCS, but worth it for a high quality product not from China!

So you could certainly get away with lowering with some higher rate race coilvers up front. Just a question of if you want to go that far with the chassis. But raising the rear would get you back into balance without spending anything but time...
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[Raize]

My car is 6 inches at the sill INCLUDING the pinch weld so possibly 6.5-7" ride height. Some of this is down to the big tyres I'm running which are around 0.7" larger diameter than the stock 924 tyres, notwithstanding that they are also stiffer and don't "squish" as much due to their lower profile I imagine a good 0.5" of my ride height could be down to the tyre change. Can't get decent road tyres in 14" any more though.


I think cutting the stock springs could be a pretty good solution as I'm looking for a little bit more spring rate to match my B6 dampers and a little bit lower and this would deliver both outcomes. But as I remember, the ends of the springs are specially formed and cut square to fit the spring seats. Anyone know if it's possible on 924?


Not going coil-over as I'd have to ditch my B6 dampers which are quite new still and were very expensive.

[Cedric]

Thats why i use the measurement from the wheel center to the fender edge, the only way to compare when different wheels comes into the equation.

Do you run complete bilstein struts or strut inserts? I converted my stock struts with these, cheap and fairly
easy.

https://www.rallydesign.co.uk/product_info.php?products_id=3450

Cutting should work, as long as they arent to soft and bottom out, which is a risk. Would give a slight increase in rate. Std springs arent exactly rare either.
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1980 924 Turbo
www.instagram.com/garagecedric/

[Raize]

I'm running the inserts so I could use something like that. Still would need to replace the torsion bars with bigger ones to match though. Dropping the rear suspension is not a task I fancy doing again.

I did some bouncing of my suspension. It's pretty much hard as a rock, very difficult to move it. Before the B6 shocks it was like a bouncy castle. The rear is easier to move than the front but still doesn't move much.

I feel like all I've achieved with these shocks is to have a terrible ride quality while still losing all my camber in the corners due to compression of my relatively soft springs (yay, mcpherson strut).

Speed bumps feel better at 20mph than at any speed below that.

Lots of clunking noises when I push/pull on the front wheels at 12:00 position. Wheel bearing?

Strut top mounts are visibly moving up and down by about half an inch when I bounce the car. Not good. Will I regret it forever if I go to a solid ball-joint type setup? I can't find any polyurethane version and the rubber hardness in top mounts you can buy varies wildly which is why I have this problem in the first place - these top mounts are only 10k miles old.

[Raize]

Also, why do we run more negative camber on the rear? The 924 rear suspension gains camber on compression whereas the front suspension mcpherson struts lose camber.


If the 924 is gaining camber in the rear, losing camber in the front, surely the best static setup would have a lot more front camber than rear camber.



Gain = negative, lose = positive, for clarity.

[Cedric]

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