cornering suspention setup questions
04-30-09 | 08:21 AM
#102
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From: Grand Rapids Michigan
I don't see any mention of swaybars in your sig? But judging by your spring rates you may need to go stiffer on the rear, or lighter on the front, to cure your understeer. Or, put on a stiffer rear swaybar if that's an option...
04-30-09 | 10:20 PM
#103
fixed sig. re-speed front bar, stock rear bar with urathane bushings.
as far as the spring rates I am tring something new on the advice of a friend, who suggested the bigger front bar and adding the rear bar. he also likes to see a 200# front to back spring rate diff. he is an team engineer in the Grand-Am ST class on an RX8. so he doesn't usually do autox cars. but his philosophy is to have softer spring rates to absorb bumps to keep the tire on the ground and stiffer sway bars to increase the spring rate in corners and have the car corner flatter. this was the first weekend on the set up so I will be tweeking the car over most of the season, I am thinking about a larger rear bar later in the season, we will see how it works out.
as far as the spring rates I am tring something new on the advice of a friend, who suggested the bigger front bar and adding the rear bar. he also likes to see a 200# front to back spring rate diff. he is an team engineer in the Grand-Am ST class on an RX8. so he doesn't usually do autox cars. but his philosophy is to have softer spring rates to absorb bumps to keep the tire on the ground and stiffer sway bars to increase the spring rate in corners and have the car corner flatter. this was the first weekend on the set up so I will be tweeking the car over most of the season, I am thinking about a larger rear bar later in the season, we will see how it works out.
05-01-09 | 10:17 AM
#104
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From: Grand Rapids Michigan
Well, your freind shares my views then as far as the relationship of spring rates and swaybars. 
My car is handling like an absolute dream right now. I took it down to the Tail of the Dragon for DGRR and could not have been happier with her performance. I'm running 275/150 for spring rates, I also have the Respeed front bar, but I'm using an aftermarket rear bar that has three holes for adjustment (I've always used the stiffest setting).
So a better rear bar might improve the understeer for you. The only other major difference I see is the shocks, where I'm using Illuminas on the front (setting of 4) and Bilsteins on the back (which might be stiffer, they're pretty harsh).
Other than that, maybe try a touch more toe out? Good luck.
My car is handling like an absolute dream right now. I took it down to the Tail of the Dragon for DGRR and could not have been happier with her performance. I'm running 275/150 for spring rates, I also have the Respeed front bar, but I'm using an aftermarket rear bar that has three holes for adjustment (I've always used the stiffest setting).
So a better rear bar might improve the understeer for you. The only other major difference I see is the shocks, where I'm using Illuminas on the front (setting of 4) and Bilsteins on the back (which might be stiffer, they're pretty harsh).
Other than that, maybe try a touch more toe out? Good luck.
07-20-09 | 11:20 AM
#108
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From: Puerto Rico
Call a professional. Nothing against the advice here but there are really talented racers and builders that have been there - done that and can help. Charlie Clark for example - 4 time Solo II National Champion, many time Divisional Champion in ITA and E Production in a first gen RX7. www.kcraceware.com
As others have mentioned and a few seconded - buy the Jim Susko book. Well worth what he charges and the help he will give you as a part of the purchase price. For some background on Susko he is an accomplished Soloist (National Champion in a DSP X19) and Roadracer - ITA/IT7 RX7.
As far as the rear suspension goes....setting up a car with heavy springs and or a sway bar to avoid TOO much movement is like slapping a band-aid on a gun shot wound. The fact is that the four link rear suspension that came in our cars has geometry problem that is made worse by decreasing the compliance of the bushing material. Racers like Dave Lemon (www.Mazdatrix.com) that race in classes where the stock suspension is required (Pro 7) use new stock control arms not control arms with urethane bushings. From the Mazdatrix web site:
"We have found that the rear suspension on these cars needs to have soft rubber bushings in order to move properly. Replacing the bushings in these links with urethane or heim joints is not functional. In addition, as the rubber in these stock links ages, it becomes harder. If you are trying to make the car handle consistently, we recommend replacing all four links with new Mazda links.
The other problem area, especially on race cars, is the watts link pivot bracket. The studs welded into the bracket have a tendency to break off. We have developed a bracket that puts the studs in double shear and greatly reduces this type of failure."
Absolutly everything he is stating here is true and Lemon has the Pro 7 racing record to back it up. In fact KC Raceware owner Charlie Clark developed heim joint kits for all four rear links on his first ITA RX7 in the middle 90's - I know beacuse I installed them on his car. The result was a series of broken lower control arms. This was caused by suspension bind. Also - I have seen the watts link pivot failure first hand...This is not BS.
Okay, so what is the cure? A Tri-Link, Pan Hard bar and Hiems in the lower control arms. With a setup like this, guys like Jim Susko and Charlie Clark have won allot of races....me too. Both gforceengineering.net (Susko) and kcraceware.com (Clark) sell tri link kits. KC Raceware has also developed a successful watts link and 4 link setup for their E Production car.
If you don't want to mess with Heims on the street or are in a class where they are not allows then use urethane bushings in the lower arms or better yet call Clark or Susko and ask. Also there is a very successful 1st Gen CSP car called Captain America - I saw this car run at Solo II Nats many times, check out how it was setup http://clemsonscc.com/Forum/viewtopic.php?p=91703
Finally....and sorry for the looooong rant.....I am not picking on anyone here. I see some well intentioned advice from guys that are trying stuff and competing with some success. The deal is that the names I have dropped in this post are race winners driving cars that are very well prepared. The cool thing is that their knowledge and experience is available to you and it does work. Hell, I am a no-talent driver but with the input from these guys some days I am fast too.
As others have mentioned and a few seconded - buy the Jim Susko book. Well worth what he charges and the help he will give you as a part of the purchase price. For some background on Susko he is an accomplished Soloist (National Champion in a DSP X19) and Roadracer - ITA/IT7 RX7.
As far as the rear suspension goes....setting up a car with heavy springs and or a sway bar to avoid TOO much movement is like slapping a band-aid on a gun shot wound. The fact is that the four link rear suspension that came in our cars has geometry problem that is made worse by decreasing the compliance of the bushing material. Racers like Dave Lemon (www.Mazdatrix.com) that race in classes where the stock suspension is required (Pro 7) use new stock control arms not control arms with urethane bushings. From the Mazdatrix web site:
"We have found that the rear suspension on these cars needs to have soft rubber bushings in order to move properly. Replacing the bushings in these links with urethane or heim joints is not functional. In addition, as the rubber in these stock links ages, it becomes harder. If you are trying to make the car handle consistently, we recommend replacing all four links with new Mazda links.
The other problem area, especially on race cars, is the watts link pivot bracket. The studs welded into the bracket have a tendency to break off. We have developed a bracket that puts the studs in double shear and greatly reduces this type of failure."
Absolutly everything he is stating here is true and Lemon has the Pro 7 racing record to back it up. In fact KC Raceware owner Charlie Clark developed heim joint kits for all four rear links on his first ITA RX7 in the middle 90's - I know beacuse I installed them on his car. The result was a series of broken lower control arms. This was caused by suspension bind. Also - I have seen the watts link pivot failure first hand...This is not BS.
Okay, so what is the cure? A Tri-Link, Pan Hard bar and Hiems in the lower control arms. With a setup like this, guys like Jim Susko and Charlie Clark have won allot of races....me too. Both gforceengineering.net (Susko) and kcraceware.com (Clark) sell tri link kits. KC Raceware has also developed a successful watts link and 4 link setup for their E Production car.
If you don't want to mess with Heims on the street or are in a class where they are not allows then use urethane bushings in the lower arms or better yet call Clark or Susko and ask. Also there is a very successful 1st Gen CSP car called Captain America - I saw this car run at Solo II Nats many times, check out how it was setup http://clemsonscc.com/Forum/viewtopic.php?p=91703
Finally....and sorry for the looooong rant.....I am not picking on anyone here. I see some well intentioned advice from guys that are trying stuff and competing with some success. The deal is that the names I have dropped in this post are race winners driving cars that are very well prepared. The cool thing is that their knowledge and experience is available to you and it does work. Hell, I am a no-talent driver but with the input from these guys some days I am fast too.
Interisting topic. I just went to a local track day yesterday. We have upgraded our 12a 84 rx-7 suspension in every way. We have the Racing beat bea suspension package. All busings in urethane. And the car is loose on the back. tending to oversteer in every corner. The car doesn't have almost any boby roll. And even the rear tire goes to the air in tight corners. In this cases when the tire hits the road again tends to spin. So I loose time in that.
Now I'm doing the correct research. I will try to set back the rear sway bar (it's ajustable) and see what's happens. If that don't make it I will need to replace the rear springs with a softer ones.
Also I'm running with a 48 Dellorto and it seems like it floored when existing the corners. Never happens on the street only on the track.
07-20-09 | 01:13 PM
#109
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From: Grand Rapids Michigan
You could try upgrading to true coilovers to get the adjustability you need to correct these issues. Or, try removing the rear bar completely and see if that solves the oversteer issues.
It could be that you have too much movement in the rear end, which allows it to move to the point of binding. Going stiffer on both ends will limit that movement and keep you out of the binding zone.
Good luck...
It could be that you have too much movement in the rear end, which allows it to move to the point of binding. Going stiffer on both ends will limit that movement and keep you out of the binding zone.
Good luck...
07-20-09 | 01:33 PM
#110
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From: Puerto Rico
You could try upgrading to true coilovers to get the adjustability you need to correct these issues. Or, try removing the rear bar completely and see if that solves the oversteer issues.
It could be that you have too much movement in the rear end, which allows it to move to the point of binding. Going stiffer on both ends will limit that movement and keep you out of the binding zone.
Good luck...
It could be that you have too much movement in the rear end, which allows it to move to the point of binding. Going stiffer on both ends will limit that movement and keep you out of the binding zone.
Good luck...
07-20-09 | 01:54 PM
#111
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From: London, Ontario, Canada
Your tire is raising into the air because your cornering hard and as the body rolls to the forward outside corner, the rear inside corner raises. The rear anti-roll bar would be limiting the amount of vertical movement that side of the axle has, so once the axle reaches its furthest point in its plane of movement it has no choice but to lift with the rest of the car. You didn't mention what type of shocks your using. Have you replaced the stock shocks? If so with what? Shocks are very important for suspension tuning. Changing to an adjustable shock will allow you to dial in the suspension and remove any over/understeer issues your having.
07-20-09 | 03:04 PM
#112
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From: Grand Rapids Michigan
Soft in front + aftermarket swaybar set to stiff setting in back = rear wheel lift. What swaybar are you using on the front of the car?
It must be pretty severe on your car, because I've never seen a 7 three-wheel before. That is usually the realm of front wheel drive cars.
It must be pretty severe on your car, because I've never seen a 7 three-wheel before. That is usually the realm of front wheel drive cars.
07-20-09 | 03:16 PM
#113
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From: Puerto Rico
Tokico Illuminas all around. The sway bars are front racing beat. And the rear is set to the stiffest (newbbie here, I have learned more about suspenstion today in this page, than during building the car). Iwill set the sway bar to less stiff to see what happens.
07-20-09 | 03:44 PM
#114
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From: Grand Rapids Michigan
Okay, hang on a minute..... There's no way I can picture the car actually going up on 3 wheels with a heavy swaybar on front too. So, I'm going to assume that you might be overstating the problem just a bit (correct me if I'm wrong). I'm guessing that what you meant was that when you are coming out of a corner, getting on the gas again, the inside rear wheel is spinning and not getting any traction. Does that sound about right? Or are people literally standing around screaming "oh my god, he's up on three wheels!!!"?
If you're just dealing with spinning, like I'm guessing, then you're going to have a tough time getting away from that without either upgrading your suspension or by getting a limited slip differential....
If you're just dealing with spinning, like I'm guessing, then you're going to have a tough time getting away from that without either upgrading your suspension or by getting a limited slip differential....
07-20-09 | 06:54 PM
#118
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From: Puerto Rico
Also Have been read the stearling page with the 'Left Hand Stumble'. Need to do somthing about these. I'm running with a Dellorto. It there is a way to fix this on them. Or I will be force to buy the stearling?
07-20-09 | 07:32 PM
#119
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From: Grand Rapids Michigan
Sorry, I don't know anything about dellorto carbs, but the Sterling carbs are top notch.
If I were you, I'd simply disconnect one of the end links for the rear bar and then try it again, see how you like it. Good luck..
If I were you, I'd simply disconnect one of the end links for the rear bar and then try it again, see how you like it. Good luck..
07-26-09 | 01:08 PM
#120
Joined: Feb 2006
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From: London, Ontario, Canada
OK well from the sounds of things your running the EXACT same suspension I am and I have never had any lift issues. My rear bar is also set to full stiff, and I have to say my car corners fairly flat. Not as flat as Kentetsu's but pretty good. A lot of road racers actually prefer to remove the rear bar all together. For autocross it's necessary but road racers seem to have better control without it. Try what Kentetsu said, disconnect one of the end links and go for a few laps, and see how you like it. If it's a huge improvement, try reconnecting it and adjusting the bar to full soft. Go for a couple more test laps and decide between the two which you prefer. If you like it better with the bar disconnected, remove it.
The issue mentioned on the Sterling Metal Works website is referring to a problem with Nikki carbs. When going through a left hand corner all the fuel in the fuel bowls sloshes over to the right side of the carb, allowing the float to drop and more fuel to enter the bowl. When the car settles and you put your foot back in it, there is too much fuel in the bowl and the carb bogs down. This particular reason for the problem may not apply to your carb. I have no experience with Dellortos either, so I won't hazard a guess about your problem. Your better off asking a 2bbl carb guy.
The issue mentioned on the Sterling Metal Works website is referring to a problem with Nikki carbs. When going through a left hand corner all the fuel in the fuel bowls sloshes over to the right side of the carb, allowing the float to drop and more fuel to enter the bowl. When the car settles and you put your foot back in it, there is too much fuel in the bowl and the carb bogs down. This particular reason for the problem may not apply to your carb. I have no experience with Dellortos either, so I won't hazard a guess about your problem. Your better off asking a 2bbl carb guy.
07-26-09 | 04:11 PM
#122
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From: https://www2.mazda.com/en/100th/
the bind in the rear suspension is proprotional to g force, the harder you corner the bigger the problem....
for instance on the track (in the honda) we're pulling 1.5G's in the corners, on the street its probably closer to .5 MAX
so the binding, and spring rate (and tires) depend on the application..
for instance on the track (in the honda) we're pulling 1.5G's in the corners, on the street its probably closer to .5 MAX
so the binding, and spring rate (and tires) depend on the application..
07-28-09 | 04:04 AM
#125
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Ok so I haven't got to do my susp yet, due to me now DDing the seven. I cant afford to have it out of commission, but I'm about to get a T2 soon, and then I can get the susp taken care of. But I have a question. I'm running 2-1/2" under axle and its hung low. I can fix it to mount in the stock position, but I really don't want to. I have a few slight bends, mostly strait, and I'm happy with the exhaust except when I have a passenger, especially a larger passenger. then It drags on dips and steep inclines. Can I get stiffer springs and leave it of do I have to make another bend?