A Trivia Question
10-24-03, 10:59 AM
#26
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I drive a Legacy GT as my everyday car, I'm very familar with this "drill"---ah the beauty of AWD
Originally posted by peejay
WRX is work to drive?
My interest is piqued. I hope Subaru's handling hasn't gone downhill.
Here's how mine was like to drive: Never ever needed more than 1/8, maybe 1/4 lock to the steering wheel. Brake, flick wheel in, control car's attitude (and therefore turning radius) with the throttle position, sometimes 3 or 4 times in the same corner (Understeer... Oversteer... Understeer... Oversteer...) then when the road looks like it's going to be straight soon, bolt the throttle down to the floor and go to the next corner.
WRX is work to drive?
My interest is piqued. I hope Subaru's handling hasn't gone downhill.Here's how mine was like to drive: Never ever needed more than 1/8, maybe 1/4 lock to the steering wheel. Brake, flick wheel in, control car's attitude (and therefore turning radius) with the throttle position, sometimes 3 or 4 times in the same corner (Understeer... Oversteer... Understeer... Oversteer...) then when the road looks like it's going to be straight soon, bolt the throttle down to the floor and go to the next corner.
10-24-03, 11:34 AM
#28
Old [Sch|F]ool
The rear suspension sucks rocks even in stock trim, lowering just amplifies its flaws.
Mainly the rear roll center is too damned high. But Mazda wanted to go with the Watts because they could easily position it ahead of the rear axle. Putting a Panhard ahead of the axle would require something with lots of odd bends, so it'd have to be fairly heavy to have any strength, and it would pose clearance problems with the body or the ground at full suspension travel. Putting the Panhard behind the rear axle would have impinged on fuel tank room. The Watts was simply the best compromise for packaging, and since it had lots of neat looking linkage they could also call it a technical advantage.
Aftermarket Panhard rod setups mount the rod behind the axle, however the aftermarket doesn't have the same concerns that the OEMs do. Like ease of assembly, rear-collision safety, etc.
Those upper links... man those are a nuisance. But they are a byproduct of Mazda trying to get the rear springs as far outboard as possible. Even 1/4" larger diameter springs will rub on the upper links, I found this out the hard way when I tried some "different" springs in the back in an effort to get more ride height to change the CG/roll center relationship.
Mainly the rear roll center is too damned high. But Mazda wanted to go with the Watts because they could easily position it ahead of the rear axle. Putting a Panhard ahead of the axle would require something with lots of odd bends, so it'd have to be fairly heavy to have any strength, and it would pose clearance problems with the body or the ground at full suspension travel. Putting the Panhard behind the rear axle would have impinged on fuel tank room. The Watts was simply the best compromise for packaging, and since it had lots of neat looking linkage they could also call it a technical advantage.
Aftermarket Panhard rod setups mount the rod behind the axle, however the aftermarket doesn't have the same concerns that the OEMs do. Like ease of assembly, rear-collision safety, etc.
Those upper links... man those are a nuisance. But they are a byproduct of Mazda trying to get the rear springs as far outboard as possible. Even 1/4" larger diameter springs will rub on the upper links, I found this out the hard way when I tried some "different" springs in the back in an effort to get more ride height to change the CG/roll center relationship.
10-24-03, 12:00 PM
#29
purple: I'll admit the roll center comment was a little off. I typed it at 4 am. The roll center on that car just moves around in space pretty drastically with suspension movement. When you lower the car everything gets worse. When the car is lowered enough, the roll center may actually be at a point below ground level when best is much above. Isn't the suspension travel after a big bump the equivalent of lowering for just a split second? It has to go somewhere. When the suspension moves up, or the car down depending on how you look at it, the rear suspension binds. It does this at any height due to poor suspension geometry. It only gets worse when one wheel goes up and the other doesn't. As far as your response to the second comment, you said what I was trying to say. You just did it better and simpler. In regards to the last comment, crap is crap no matter where you put it or how tall it is. The stock suspension just sucks and it doesn't matter where the car is. If it were good the car wouldn't be so tail happy but I explained why that is. The car is very tail happy at any height and binding occurs at every height as well. They just get dramatically worse when the suspension is depressed whether it be from cornering or lowering.
The Watt's linkage system isn't too bad if both sides of it are equal lengths. Look under your car, they aren't. They are only compounded by the stock 4 link setup. 2 really long lower arms, 2 really short upper arms, and then they didn't even line them up with each other or in a way that would move with the Watt's links. Binding, binding, binding.
The Watt's linkage system isn't too bad if both sides of it are equal lengths. Look under your car, they aren't. They are only compounded by the stock 4 link setup. 2 really long lower arms, 2 really short upper arms, and then they didn't even line them up with each other or in a way that would move with the Watt's links. Binding, binding, binding.
10-24-03, 01:04 PM
#30
spoon!
All righty; here's my question. How do you fix the 1st gen suspension problems? I'm aware of them already; we moved to a tri-link / panhard bar on our ITA car this season. Wondering if there's a better way. Is the 4-link workable with different link lengths top and bottom as long as the links are in the same plane, given spherical bearings if needed? If not is there any place to put longer upper arms, or shorter lower ones? My memory of exactly where everything is is imperfect. 
And also, any benefit given by moving the shocks/springs farther inboards, aside from minor things like possibly redoing the wheel wells for a bit more rubber? Or penalties for that matter.
(I can run the numbers on my own after a bit of work when I get home, but I wanted someone else's opinion)
Also, what if you did something like put a cell where the storage bins are stock instead of having the tank out in the ***? Would fix some of the weight distribution issues, no?
Just throwing out ideas.
And also, any benefit given by moving the shocks/springs farther inboards, aside from minor things like possibly redoing the wheel wells for a bit more rubber? Or penalties for that matter.(I can run the numbers on my own after a bit of work when I get home, but I wanted someone else's opinion)
Also, what if you did something like put a cell where the storage bins are stock instead of having the tank out in the ***? Would fix some of the weight distribution issues, no?
Just throwing out ideas.
10-24-03, 01:37 PM
#31
Absolute Power is Awesome
Originally posted by rotarygod
The Watt's linkage system isn't too bad if both sides of it are equal lengths. Look under your car, they aren't. They are only compounded by the stock 4 link setup. 2 really long lower arms, 2 really short upper arms, and then they didn't even line them up with each other or in a way that would move with the Watt's links. Binding, binding, binding.
The Watt's linkage system isn't too bad if both sides of it are equal lengths. Look under your car, they aren't. They are only compounded by the stock 4 link setup. 2 really long lower arms, 2 really short upper arms, and then they didn't even line them up with each other or in a way that would move with the Watt's links. Binding, binding, binding.
10-24-03, 02:51 PM
#32
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Would someone please explain to me how a panhard rod is an improvement over a Watts link? A panhard rod definitely moves the axle side-to-side, something the Watts link won't do. I can't imagine how the Watts link binds in any way that the panhard rod wouldn't (i.e. fore-aft movement of the axle). Maybe I'm just biased by three years of SS racing, but these things are a blast to drive in stock config. Mazda engineers knew what they were doing.
10-24-03, 05:27 PM
#33
Old [Sch|F]ool
Nicki:
The stock Watts link sucks rocks. The roll center is too high. In addition, since the suspension is trying to rotate around the center of the axle. The four link suspension doesn't want to move that way due to the upper links being in strange and contradictory ways.
A Panhard rod does move the axle side to side, but really it is NOT SIGNIFICANT. Let's say your Panhard rod is 36" long and your total suspension travel is 8". Say 4" up and 4" down. (This is a bit excessive) Grab a yardstick and a big piece of paper, draw a line 36" long and draw a line perpendicular to one end 8" long, 4 inches up and 4" down just like our theoretical suspension. Now anchor the yardstick at one end of the line and at the other end draw a line, holding the pen on the end of the yardstick, and sraw an arc of the same length as your 8" line. You have now drawn the arc your 36" long Panhard rod would describe, and you can see how much it deviates from a straight line.
Actually, I can do the math for you. Pythegorean theorem = x^2 plus y^2 is z^2. Z (hypoteneuse) is 36", y (vertical movement) is 4", solve for X.
x^2 plus 4^2 equals 36^2.
x^2 plus 16 is 1296.
x^2 is 1280.
square root of 1280 is 35.777.
So the axle is moving a maximum of less than 1/4 inch over the entire travel of the suspension. *This is less than the amount of bushing flex there is in the suspension*.
Why is the Panhard more advantageous? You can get the roll center lower, IE farther away from the center of gravity, so that when the suspension moves up and down the distance doesn't change much as a percentage of the whole. This makes for more consistent handling over bumps, braking, and accelerating.
Still hasn't done anything about the poor position of the upper links, though, which also will cause binding. Solution for that is to throw away the upper links and go with a single centrally mounted upper link. Now there's no more binding.
The stock Watts link sucks rocks. The roll center is too high. In addition, since the suspension is trying to rotate around the center of the axle. The four link suspension doesn't want to move that way due to the upper links being in strange and contradictory ways.
A Panhard rod does move the axle side to side, but really it is NOT SIGNIFICANT. Let's say your Panhard rod is 36" long and your total suspension travel is 8". Say 4" up and 4" down. (This is a bit excessive) Grab a yardstick and a big piece of paper, draw a line 36" long and draw a line perpendicular to one end 8" long, 4 inches up and 4" down just like our theoretical suspension. Now anchor the yardstick at one end of the line and at the other end draw a line, holding the pen on the end of the yardstick, and sraw an arc of the same length as your 8" line. You have now drawn the arc your 36" long Panhard rod would describe, and you can see how much it deviates from a straight line.
Actually, I can do the math for you. Pythegorean theorem = x^2 plus y^2 is z^2. Z (hypoteneuse) is 36", y (vertical movement) is 4", solve for X.
x^2 plus 4^2 equals 36^2.
x^2 plus 16 is 1296.
x^2 is 1280.
square root of 1280 is 35.777.
So the axle is moving a maximum of less than 1/4 inch over the entire travel of the suspension. *This is less than the amount of bushing flex there is in the suspension*.
Why is the Panhard more advantageous? You can get the roll center lower, IE farther away from the center of gravity, so that when the suspension moves up and down the distance doesn't change much as a percentage of the whole. This makes for more consistent handling over bumps, braking, and accelerating.
Still hasn't done anything about the poor position of the upper links, though, which also will cause binding. Solution for that is to throw away the upper links and go with a single centrally mounted upper link. Now there's no more binding.
10-24-03, 06:03 PM
#34
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Originally posted by rotarygod
Hopefully this helped shed some light on the big problems with this "true sports car". The rear suspension design is borrowed from the early '70s RX-3 so it isn't a new technological breakthrough for the RX-7. It is old transplanted technology.
Hopefully this helped shed some light on the big problems with this "true sports car". The rear suspension design is borrowed from the early '70s RX-3 so it isn't a new technological breakthrough for the RX-7. It is old transplanted technology.
mike
10-25-03, 01:58 AM
#35
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well, i think you guys lost me at the roll center thing. all i know is that i enjoy driving the my 1st gen(1500 miles in 2 weeks) and would love to own an RX-8, 190 or 250hp, doesnt matter...
) and would love to own an RX-8, 190 or 250hp, doesnt matter...
10-25-03, 09:35 AM
#36
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ok, then rotarygod, or peejay, what would need to be done to fix all these errors. i noticed that watts link a while ago while working on my car and i was like wtf is that. im not even worried about making it top notch just fix some of this mess up. (sorry no grammer, quick post)
10-25-03, 11:29 AM
#38
Old [Sch|F]ool
Already working on it. I'd like to swap the front end as well. First I need to find a junkyard Miata and take lots of measurements.
What can be done to fix? Simple, dig out $500 or so and call up G-Force Racing in Findlay, Ohio and pick up their Panhard rod setup ($269) and their tri-link setup (eliminates the upper control arms, requires Panhard rod, $269) OR, if you're like me and you're long on fabrication and short on funds, you can work up something of your own. Which is another reason I want to find a Miata in the junkyard... I have constant visions of getting a '94-up pumpkin, which bolts right in to the RX-7 rearend, and turning the PPF into a torque arm. Then making my own Panhard, and presto, a torque arm rear suspension, just like all the Mustang guys spend big $$$ to convert to and the Camaro guys already have and is one of the few things Chevy ever did right.
I'd like to swap the front end as well. First I need to find a junkyard Miata and take lots of measurements.What can be done to fix? Simple, dig out $500 or so and call up G-Force Racing in Findlay, Ohio and pick up their Panhard rod setup ($269) and their tri-link setup (eliminates the upper control arms, requires Panhard rod, $269) OR, if you're like me and you're long on fabrication and short on funds, you can work up something of your own. Which is another reason I want to find a Miata in the junkyard... I have constant visions of getting a '94-up pumpkin, which bolts right in to the RX-7 rearend, and turning the PPF into a torque arm. Then making my own Panhard, and presto, a torque arm rear suspension, just like all the Mustang guys spend big $$$ to convert to and the Camaro guys already have and is one of the few things Chevy ever did right.
10-25-03, 12:24 PM
#39
Absolute Power is Awesome
There's often Miata parts on ebay.
http://cgi.ebay.com/ebaymotors/ws/eB...tem=2438956844
http://cgi.ebay.com/ebaymotors/ws/eB...tem=2439098534
http://cgi.ebay.com/ebaymotors/ws/eB...tem=2438956844
http://cgi.ebay.com/ebaymotors/ws/eB...tem=2439098534
11-04-03, 10:36 PM
#41
Absolute Power is Awesome
By the way, none of this is to say that the 1st gen isn't a hell of a blast to drive. Once you're used to expecting the back end to swing a bit, you miss it in other cars. There are very few cars in my experience that can match the 1st gen in every day entertainment.
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