Thoughts on shock valving and winter
#1
Thoughts on shock valving and winter
Just came back from a short drive to make sure the car handles subzero temps. Yes friends, the mercury plunged down to -3 F (even more depressing if you think in Metric) in Cleveland. Fortunately, that's about as cold as it ever gets here.
The stock Mazda shocks are set up to be rebound-heavy. That is, the rebound (extension) damping is stiffer than the jounce (compression) damping. This has various benefits for handling purposes, which are beyond the scope of this post.
When it gets cold, the fluid in the shock thickens. It's just oil, after all.
When it gets down to -3, it apparently thickens to the point where it's a barely flowable jelly ooze.
It seems to move somewhat under compression. Not much. But the stiff rebound valving doesn't want to let fluid pass through at *all*.
Now picture a lone, salt-coated GSL driving down the lumpy Cleveland roads. Hobbyhorsing over every bump, since most of the suspension is now the tires, thanks to the gelled shock fluid. And with every bump, the car gets a little lower, since the shocks won't rebound. After about 1/4 mile the car was riding down on the bumpstops. Took 20 minutes for the fluid to heat up enough for the suspension to start moving.
Happy winter, y'all...
The stock Mazda shocks are set up to be rebound-heavy. That is, the rebound (extension) damping is stiffer than the jounce (compression) damping. This has various benefits for handling purposes, which are beyond the scope of this post.
When it gets cold, the fluid in the shock thickens. It's just oil, after all.
When it gets down to -3, it apparently thickens to the point where it's a barely flowable jelly ooze.
It seems to move somewhat under compression. Not much. But the stiff rebound valving doesn't want to let fluid pass through at *all*.
Now picture a lone, salt-coated GSL driving down the lumpy Cleveland roads. Hobbyhorsing over every bump, since most of the suspension is now the tires, thanks to the gelled shock fluid. And with every bump, the car gets a little lower, since the shocks won't rebound. After about 1/4 mile the car was riding down on the bumpstops. Took 20 minutes for the fluid to heat up enough for the suspension to start moving.
Happy winter, y'all...
#5
Yah I remember my autos teacher telling me about where it gets really cold, the gear oil in the rearend turns to stiff grease and it burns up the gears and bearings because they just ride in a trough dug through the sludge instead of having flowing liquid oil. Fun stuff, and a great argument for synthetics.
#7
That doesn't work when the tires are as grippy as cast iron, and the engine needs careful nursing when you apply throttle lest it run so lean it just *dies* (even at 3500rpm!) and you can't see out the windshield because the engine *still* isn't warm enough to generate any useful heat...
Ah, I love winter! I don't know how you guys in the warmer climes can deal with your winters.
- Pete (It's 50 degrees in my bedroom! Whee!)
Ah, I love winter! I don't know how you guys in the warmer climes can deal with your winters.
- Pete (It's 50 degrees in my bedroom! Whee!)
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#9
My wife bought me 2 RX-7s
Joined: Aug 2001
Posts: 2,328
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From: Saskatoon, Saskatchewan, Canada
You could be driving your seven in minus 40 Celsius weather...
Let's see, what stops working at that temp?
-Brakes: My brakes cease boosting at around -35 or so, all the booster does is make a 'SQUOOOO!' sound, followed closely by me panicking because I now have manual brakes.
-Suspension: My shocks get so cold that they simply cease working. My ride height doesn't alter rather it's simply like driving a buckboard.
-Heat: My heater stops putting out hot air and instead decides to blow cold or at best tepid air.
My car WILL start though, which is better than most.
Let's see, what stops working at that temp?
-Brakes: My brakes cease boosting at around -35 or so, all the booster does is make a 'SQUOOOO!' sound, followed closely by me panicking because I now have manual brakes.
-Suspension: My shocks get so cold that they simply cease working. My ride height doesn't alter rather it's simply like driving a buckboard.
-Heat: My heater stops putting out hot air and instead decides to blow cold or at best tepid air.
My car WILL start though, which is better than most.
#11
Yah. I am suprised the poor bugger runs at all, actually. THIS close to putting the MSD in, but that would require bumming heated garage space for a few hours.
Had the vacuum booster freeze up in my T-bird. Not even manual brakes, the brake pedal was just a footrest. Hit the retaining wall in the parking lot at work at about 10mph. Good times.
I told you guys about how I managed to freeze my cooling system, split the radiator, and not find out until AFTER overheating the engine, right? (This being on a day I interviewed for a job) Engine's fine, and there's a shroudless '80 radiator where the Mongoid '85 radiator used to be. I figured the smaller radiator and poorer shroud would enhance warmup time. Nope. I consistently start to get good heat after 9 1/2 miles of my 10 mile trip to work in the morning. Gotta drive with the windows open to keep the windshield from fogging up, too...
- Pete (Is that -40C or -40F? )
Had the vacuum booster freeze up in my T-bird. Not even manual brakes, the brake pedal was just a footrest. Hit the retaining wall in the parking lot at work at about 10mph. Good times.
I told you guys about how I managed to freeze my cooling system, split the radiator, and not find out until AFTER overheating the engine, right? (This being on a day I interviewed for a job) Engine's fine, and there's a shroudless '80 radiator where the Mongoid '85 radiator used to be. I figured the smaller radiator and poorer shroud would enhance warmup time. Nope. I consistently start to get good heat after 9 1/2 miles of my 10 mile trip to work in the morning. Gotta drive with the windows open to keep the windshield from fogging up, too...
- Pete (Is that -40C or -40F? )
#12
Yah I remember my autos teacher telling me about where it gets really cold, the gear oil in the rearend turns to stiff grease and it burns up the gears and bearings because they just ride in a trough dug through the sludge instead of having flowing liquid oil. Fun stuff, and a great argument for synthetics.
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