sumpcracker
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Posts: 1,751
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I have a 1986 944 with standard 944 turbo gas shocks. I just cant believe how different it sits some days compared with others. I was thinking it was being parked on uneven ground, but this is not the case, ive checked and moved the car. It literaly sits 30-40mm higher some days than others?? Am I right to assume this is down to heat and gas shocks? or is there some other possible reason? Its doing my head in, whenever somone takes a tasty pic its sky high, I don't want to drop it more as it will be too much on a low day. Never come accross this problem before, bloody weird. There is also a noticable difference in handleing from day to day. 2 exmaples, and it gets worse!   |
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sumpcracker
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Another, all hot days too  I realise somthing could be moving, ive just noticed the rear camber difference in the pics! |
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stealthstylz
Club Retro Rides Member
Posts: 14,960
Club RR Member Number: 174
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Jun 29, 2011 10:31:19 GMT
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The shocks shouldn't be raising and lowering the car. Gas shocks are still mostly oil filled, they just have compressed nitrogen in the bottom. Rear shocks might just be knackered and not moving freely.
Matt
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RobinJI
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"Driven by the irony that only being shackled to the road could ever I be free"
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Jun 29, 2011 11:16:57 GMT
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That's a weird issue, and something I've never heard of before. I'm not sure I'd say it's down to the shocks. Personally I can't actually see much of a difference in the pictures. The profile view looks marginally lower, but then it's hard to tell due to how the light falls on arch's. Was the 30-40mm height change you mention measured, or just observed?
Racing cars have their ride heights set, and regularly checked to the millimetre in order to pass scrutineering, and I've never heard of the heights wandering without good reason.
As Matt says, the gas in the dampers is compressed nitrogen used to pressurise the damping oil in order to prevent cavitation and generally keep it in a more stable state. It only provides a slight assist to the spring rate because when the damper is compressed the rod takes up space within the body, compressing the gas slightly more, they're not really designed to add to the spring rate, it's just a minimal side effect. Nitrogen is known to be very stable in volume under temperature change, it's why people fill tyres with the stuff, to reduce pressure increase when they heat up. Bearing in mind your average Joe can fully compress a gas damper by hand, it would take a pretty serious pressure increase in the nitrogen to lift a car 30mm.
It may be worth looking at the bush's. A lot of OEM bush's rely on twist in the rubber they're made from in order to let the suspension move. If the last time they were torqued up the suspension was at stock height, and it's since been lowered considerably, then they'll be constantly trying to fight their way back to stock height, trying to lift the car, and rubbers elasticity is really quite sensitive to temperature.
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stealthstylz
Club Retro Rides Member
Posts: 14,960
Club RR Member Number: 174
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Jun 29, 2011 12:10:18 GMT
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Thats another good shout. I was thinking more that the damper rod on the rear shocks could be slightly bent, making a tight spot in it's movement.
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bortaf
Posted a lot
Posts: 4,549
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Jun 29, 2011 12:20:12 GMT
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I think your confusing gas shocks with air suspension? as said the gas is in the shocks to basicly stop them overheating when worked hard and loosing damping, that's why most "cooking" spec cars of a particular model have gas shocks over just oil, or did back in 80/90s. I recon theres a bearing or bush inner sleave seized or ripped out of a bush going on posssably? stumped TBH never ever seen a shock raise a car by ni on 2 inches before  not even an adjustable when re set to rockhard has that mutch effect ? weird |
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Last Edit: Jun 29, 2011 12:21:17 GMT by bortaf
R.I.P photobucket
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sumpcracker
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Jun 29, 2011 13:13:36 GMT
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It is weird and yes I did mesure it, at the time the alteration was 25mm.
I'm aware of the workings of suspension, I just couldnt see any other reason for it apart from the gas shocks.
Ive never come across a problem I cant sort before, and ive never seen this.
I have just stripped it with the intention of changing rear bushes, shocks, and maybe the whole beam, on stripping it I found the eccentric bolts on both rear arms not tight, I think the forces of driving may have been turning the adjustment, seems a logical explination - until you wonder how its moved both sides equaly - then again they can be used to adjust the ride height,camber and caster and they also attach the roll ber links so it could be the roll bar is turning them and resetting them each time, this also explains my premature tyre wear, fingers crossed problem solved.
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not even an adjustable when re set to rockhard has that mutch effect ? weird