rear wheel steering fix?
05-10-06, 01:54 AM
#1
rear wheel steering fix?
As I hear the original rear wheel steering bushings on the rx-7 are usually worn out by now. The only solution short of replacing the entire rear end is to get rear-wheel steering disabling replacement bushings. No more Porsche-beating rear wheel steering? What a loss.
I'd like to try a more ambitious solution. CNC machining new bushings to stock dimensions. Problem is I don't even know what the original bushings look like. From the small pictures I barely even know what the replacement bushings look like. So if anyway has stock dimensions, sketches, photos, etc., etc. it would be a big help.
I can design it and get a company to CNC it for ~$50 per unique part, plus about $5 per repeat (e.g., $55 per pair, etc.). For double the cost I could make ~10 sets and sell the rest. If there are too many parts I might use the milling or CNC machine here at Berkeley.
Lastly, what's a good material? I assume sticking with rubber or whatever is stock will just make the bushing fail again. Polypropylene then?
I'd like to try a more ambitious solution. CNC machining new bushings to stock dimensions. Problem is I don't even know what the original bushings look like. From the small pictures I barely even know what the replacement bushings look like. So if anyway has stock dimensions, sketches, photos, etc., etc. it would be a big help.
I can design it and get a company to CNC it for ~$50 per unique part, plus about $5 per repeat (e.g., $55 per pair, etc.). For double the cost I could make ~10 sets and sell the rest. If there are too many parts I might use the milling or CNC machine here at Berkeley.
Lastly, what's a good material? I assume sticking with rubber or whatever is stock will just make the bushing fail again. Polypropylene then?
Last edited by ericgrau; 05-10-06 at 02:00 AM.
05-10-06, 05:56 AM
#3
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Originally Posted by ericgrau
I'd like to try a more ambitious solution. CNC machining new bushings to stock dimensions. Problem is I don't even know what the original bushings look like. From the small pictures I barely even know what the replacement bushings look like. So if anyway has stock dimensions, sketches, photos, etc., etc. it would be a big help.
I can design it and get a company to CNC it for ~$50 per unique part, plus about $5 per repeat (e.g., $55 per pair, etc.). For double the cost I could make ~10 sets and sell the rest. If there are too many parts I might use the milling or CNC machine here at Berkeley.
Lastly, what's a good material? I assume sticking with rubber or whatever is stock will just make the bushing fail again. Polypropylene then?
I can design it and get a company to CNC it for ~$50 per unique part, plus about $5 per repeat (e.g., $55 per pair, etc.). For double the cost I could make ~10 sets and sell the rest. If there are too many parts I might use the milling or CNC machine here at Berkeley.
Lastly, what's a good material? I assume sticking with rubber or whatever is stock will just make the bushing fail again. Polypropylene then?
The material is a special durometer rubber that's specifically design with elastic / compressive characteristics to deflect under a certain G-load to the rear wheels.
Mazda went through a lot of trouble to figure this out.
I don't think you can CNC "low" durometer rubber?
-Ted
05-10-06, 10:54 AM
#4
You probably could CNC that rubber. Maybe not on the CNC milling machine, but on some CNC machine. The problem is obtaining the rubber. So are the dimensions the same as the eliminator bushing?
Do you know what durometer (number) the rubber is? What kind of rubber is it? I mean there's urethane, hypalon, natural, neoprene, nitrile, silicon, styrene butadiene, synthetic (EPDM), vinyl, viton and more.
From what I know from my materials class, rubber is a kind of soft plastic. The only major characteristics are stiffness, creep and strength. I'll need to match the stiffness with equal or lower creep and equal or higher strength. The problem is the manufacturer can vary these characteristics depending on how much filler he uses, so an exact match may be hard to find.
Does anyone know why else this hasn't been done before? Because Mazda blended their own rubber? Because serious drivers don't need it and everyone else doesn't know about it?
Do you know what durometer (number) the rubber is? What kind of rubber is it? I mean there's urethane, hypalon, natural, neoprene, nitrile, silicon, styrene butadiene, synthetic (EPDM), vinyl, viton and more.
From what I know from my materials class, rubber is a kind of soft plastic. The only major characteristics are stiffness, creep and strength. I'll need to match the stiffness with equal or lower creep and equal or higher strength. The problem is the manufacturer can vary these characteristics depending on how much filler he uses, so an exact match may be hard to find.
Does anyone know why else this hasn't been done before? Because Mazda blended their own rubber? Because serious drivers don't need it and everyone else doesn't know about it?
Last edited by ericgrau; 05-10-06 at 11:15 AM.
05-10-06, 11:29 AM
#5
Originally Posted by ericgrau
Does anyone know why else this hasn't been done before? Because Mazda blended their own rubber? Because serious drivers don't need it and everyone else doesn't know about it?
Mazdatrix has the eliminators
Mazda has the originals
Now I have never priced the factory ones out, but I can't imagine that they are worth more than the R&D and mfr'ing costs of making your own.
05-10-06, 11:49 AM
#7
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Well, it'd be nice to replace with factory parts, except it costs $300 a part since they only sell the assembly, not the individual bushings.
If you figure it out, I'll buy a pair and guinea pig with you. Good luck, though. If it could be done effectively I bet Mazdatrix or elsewhere would've already gotten it working.
If you figure it out, I'll buy a pair and guinea pig with you. Good luck, though. If it could be done effectively I bet Mazdatrix or elsewhere would've already gotten it working.
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05-10-06, 12:40 PM
#8
$300 per side or for both wheels? That's actually not too bad, and would explain why this hasn't been done before. I mean, I'm tempted to skip the machining and shell out the $300. $600, on the other hand, would make me try to tackle this.
Last edited by ericgrau; 05-10-06 at 12:48 PM.
05-10-06, 02:40 PM
#9
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$300 per side. Eliminators are $40 a set. I don't see how you could consider even $300 to be a economically feasible versus $40 when Icemark brings up the good point of it requiring decades of dedicated track experience to properly utilize the original DTSS system.
(MazdaPartsCheap.com has the 929 spindle listed instead of the RX-7, but it's still $330 each. I don't know if the 929 is interchangeable or if they just screwed up, but I can't imagine the RX-7 spindle being any cheaper.)
(MazdaPartsCheap.com has the 929 spindle listed instead of the RX-7, but it's still $330 each. I don't know if the 929 is interchangeable or if they just screwed up, but I can't imagine the RX-7 spindle being any cheaper.)
05-10-06, 10:19 PM
#14
Originally Posted by classicauto
fcfdrifter owns this thread
Thanks fcfdrifter. Sorry Goofy, I'm going to a Mazda dealer. If I can find some buyers I may reverse engineer the bushing after I get it. Don't count on it, though.
One question remains. Got any links to an installation guide? Is it bolt-on or do I need something hydraulic? If I need a $100+ tool or several hours of labor with cheaper tools, I'll pay a mechanic to do it.
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