just scaled a 20B fd
01-30-04, 01:08 PM
#26
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I actually have a friend with the RA's and they're rock hard. He seems to like it though. Sounds like it would ride like a Mustang GT over the bumps though :-) The secret may be in their better valving, but for the street, that's a bit extreme. If you live in Michigan, god help you with those shocks.
Ted, as you can see by the posted shock rates, the Flex has the same rate as the HA's. It's my opinion they simply annodized certain components for better rust resistance and rebadged them. Shock valving may have changed slightly. As per the "bouncy" feel, I have a certain section of road I test on that has undulating ripples of a consistency that when travelling over 60mph, they give you a true indicator of the shock's compression and rebound characteristics. Where the HA's fail is in the valving itself...The RE/RA's are much larger in diameter and use more precise, expensive valving. Sort of like the difference between your garden variety Showa suspension on a streetbike and Ohlins road forks for the same model (Aprilia comes to mind as they have the same model with both options as do Ducati). Most of the "cheaper shocks can't react quick enough to control the spring rate as it's being compressed over a relatively quick succession of bumps so you get this osciliation in the setup and the bouncy, jouncy feeling. If I switched to a set of say Aragosta's or Penske's, the car would not exhibit the same tendencies. Again, it's not that it doesn't have enough damping, the damping doesn't react quickly enough to control the spring's motion. If you look at most of the more expensive units, they're all monotube and anywhere from 45 to 50mm in diameter. I posted some time ago on the HA's diameter which I can't remember off hand, but they were larger than the Koni's which were 38mm's or thereabouts.
Howard, agreed on your road race stuff, I think we're essentially saying the same thing :-) I have a slight oversteer problem due to two factors. One, my rear swaybar is on it's stiffest setting. I need to reduce the setting or perhaps get a softer bar. Two, the F/R spring ratio on the Tein HA's is fairly high, the rears being harder than most road race rotary guys would recommend when taking the front spring rate into account. This will limit rear wheel grip especially in the wet and induce oversteer.
Agreed on the widebody stuff...the RE Amemiya kit (AD GT sides) is actually fairly efficient at managing airflow but again, I'm sure it increases drag. But that's what a 600hp three rotor is for!
On a side note, the 2001 Ferrari F1 car has a drag coeficient of around .6 and just by lifting off the throttle at 200mph, the car will be subject to about 1.06g's just from air resistance alone, no brakes needed!
Ted, as you can see by the posted shock rates, the Flex has the same rate as the HA's. It's my opinion they simply annodized certain components for better rust resistance and rebadged them. Shock valving may have changed slightly. As per the "bouncy" feel, I have a certain section of road I test on that has undulating ripples of a consistency that when travelling over 60mph, they give you a true indicator of the shock's compression and rebound characteristics. Where the HA's fail is in the valving itself...The RE/RA's are much larger in diameter and use more precise, expensive valving. Sort of like the difference between your garden variety Showa suspension on a streetbike and Ohlins road forks for the same model (Aprilia comes to mind as they have the same model with both options as do Ducati). Most of the "cheaper shocks can't react quick enough to control the spring rate as it's being compressed over a relatively quick succession of bumps so you get this osciliation in the setup and the bouncy, jouncy feeling. If I switched to a set of say Aragosta's or Penske's, the car would not exhibit the same tendencies. Again, it's not that it doesn't have enough damping, the damping doesn't react quickly enough to control the spring's motion. If you look at most of the more expensive units, they're all monotube and anywhere from 45 to 50mm in diameter. I posted some time ago on the HA's diameter which I can't remember off hand, but they were larger than the Koni's which were 38mm's or thereabouts.
Howard, agreed on your road race stuff, I think we're essentially saying the same thing :-) I have a slight oversteer problem due to two factors. One, my rear swaybar is on it's stiffest setting. I need to reduce the setting or perhaps get a softer bar. Two, the F/R spring ratio on the Tein HA's is fairly high, the rears being harder than most road race rotary guys would recommend when taking the front spring rate into account. This will limit rear wheel grip especially in the wet and induce oversteer.
Agreed on the widebody stuff...the RE Amemiya kit (AD GT sides) is actually fairly efficient at managing airflow but again, I'm sure it increases drag. But that's what a 600hp three rotor is for!
On a side note, the 2001 Ferrari F1 car has a drag coeficient of around .6 and just by lifting off the throttle at 200mph, the car will be subject to about 1.06g's just from air resistance alone, no brakes needed!
01-30-04, 01:32 PM
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so back to the HA v.s. FLEX issue, i see the spring rates are the same so (if you know this) how is the dampening diffrent? im trying to figure out which of these 2 coilovers would be best for me.
you said that your FD has 52% rear weight? what have you done to your car in the way of removing weight from the front? maybe the 3rotor wouldnt affect weight distrib. all that much. there is a shop close to me that will do corner weights... when i get the motor mounted in im planning on towing it in to get an idea of where all the weight sits, and then adjust the battery location and a few other things to try and compensate.
you mentioned keeping the stock centerline on the tire.... how do you find the stock centerline? is that offset? im shopping for wheels now so im glad this was brought up.
maxcooper uses 285's up front on the track, however the car im building will also need to be streetable so idont know if 285's up front are really an option. does offset matter in the rear?
widebody kits are not an option for me as i think they are ugly, and unfortunatly form comes before function in this situation... im not opposed to rolling the rear fenders a bit, but thats as far as id like to take it. only thing is i dont think 335's will fit in the rear w/out some major work.... im still debating what is best to do.
as per the nylon bushings, a forum member -> jimlab was making nylon bushings for a while... recently some talk came up about him doing another run but if the interest is not there he wont make them. food for thought.
PS I vote to have this thread stay here as well.... there are some 20b specific things that we are talking about.
you said that your FD has 52% rear weight? what have you done to your car in the way of removing weight from the front? maybe the 3rotor wouldnt affect weight distrib. all that much. there is a shop close to me that will do corner weights... when i get the motor mounted in im planning on towing it in to get an idea of where all the weight sits, and then adjust the battery location and a few other things to try and compensate.
you mentioned keeping the stock centerline on the tire.... how do you find the stock centerline? is that offset? im shopping for wheels now so im glad this was brought up.
maxcooper uses 285's up front on the track, however the car im building will also need to be streetable so idont know if 285's up front are really an option. does offset matter in the rear? widebody kits are not an option for me as i think they are ugly, and unfortunatly form comes before function in this situation... im not opposed to rolling the rear fenders a bit, but thats as far as id like to take it. only thing is i dont think 335's will fit in the rear w/out some major work.... im still debating what is best to do.
as per the nylon bushings, a forum member -> jimlab was making nylon bushings for a while... recently some talk came up about him doing another run but if the interest is not there he wont make them. food for thought.
PS I vote to have this thread stay here as well.... there are some 20b specific things that we are talking about.
Last edited by RotorMotor; 01-30-04 at 01:37 PM.
02-06-04, 09:45 PM
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Damping is determined by the valving inside the shock and what they're set at if adjustable. There are essentially two types of damping, compression and rebound. As the name suggests, they control the movement during shock compression and when it rebounds to it's "natural" state. Most shocks that are on the market are "single" adjustable, meaning there's one adjustment **** used to modify compression and rebound damping. It's set by the factory in terms of the ratio of change between the two. So, even though the Flex and HA's use the same springs/rates, their internal valving and thus damping can be different. Many a car has pulled over a G using the HA's. Look no further than the SCC's USCS where even Supras have pulled over a G using them :-) The sticky tires didn't hurt either :-) Hope that clears it up a bit.
02-07-04, 12:04 PM
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Well that's the big question...I don't know that it is actually valved any differently from the HA's. IMHO, I think it's the same shock with minor internal upgrades and anodizing for better ride on US roads and corosion resistance.
02-10-04, 09:06 AM
#31
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re: Flex/HA
i have no experience w the Tein Flex product other than noting that the spring rate is identical to the HA product. since the primary function of shock valving is to control spring oscillation i would assume that the shock valving is probably identical. as i mentioned i have a shock dyno. i have dynoed numerous shocks for the fd. there is nothing magic as to shocks. most shocks have 3 valves that work in bump and rebound. the high speed valve is for bumps, medium speed controls undulations and the low speed is for corners. the HA has 16 adjustments that effect bump and rebound and for high speed thru low speed. the valving is just a tick firmer than the stock fd shock on full soft and can be adjusted to the point where there is almost no wheel movement. it is highly effective. the HA is a monotube which allows for a larger piston and more sensitive valving. can you buy a better coil-over setup? you'd be getting far less additional performance than you might expect. sure, separately adj bump and rebound, or remote resevoirs blah blah blah. in 5 years at Brainerd Int'l i have not been beaten by anything. period. and my suspension is a factor and the HA's are central.
Michel, you mentioned some oversteer and that, among other things, your rear bar is full stiff. adj it full soft, make sure your rear tire pressure cold is at least 3 lbs less than the front..... 30/27 for starters. you need to use a pyrometer to check your camber too. you want a bit more tire temp (20 degrees approx) in the inside 1/3rd of the tire. i don't think it is your spring balance front to rear as you have 566 f and 422 rear making your rear spring rate 43% of the total. my RS*Rs are 432 front 378 rear making my rear springs 46% of the total and my car is right on the money... (though i do run a larger rear wheel and tire than front.) so i don't think your f/r spring rate is an issue. i think the bar setting, tire pressure and camber are where i would look first. do make sure you move your battery and get everything out of your engine compartment but the engine.
as to offset....
take a stock wheel. lay it on a level surface. lay a straightedge across the top. find the distance between the top of the section width of the tire and the mounting surface. then measure from the mounting surface thru a stud hole to the floor. you now have the data to determine the mounting surface offset from the centerline of the tire which is the offset. do not deviate from this offset. BTW, the car is very happy w 245s up front. i just read a review of the new Honda 2000. they did alot of work on the chassis and mounted larger tires on the rear than the front to balance the car. rear engine cars like wider rear wheels. especially 20bs...
howard coleman
i have no experience w the Tein Flex product other than noting that the spring rate is identical to the HA product. since the primary function of shock valving is to control spring oscillation i would assume that the shock valving is probably identical. as i mentioned i have a shock dyno. i have dynoed numerous shocks for the fd. there is nothing magic as to shocks. most shocks have 3 valves that work in bump and rebound. the high speed valve is for bumps, medium speed controls undulations and the low speed is for corners. the HA has 16 adjustments that effect bump and rebound and for high speed thru low speed. the valving is just a tick firmer than the stock fd shock on full soft and can be adjusted to the point where there is almost no wheel movement. it is highly effective. the HA is a monotube which allows for a larger piston and more sensitive valving. can you buy a better coil-over setup? you'd be getting far less additional performance than you might expect. sure, separately adj bump and rebound, or remote resevoirs blah blah blah. in 5 years at Brainerd Int'l i have not been beaten by anything. period. and my suspension is a factor and the HA's are central.
Michel, you mentioned some oversteer and that, among other things, your rear bar is full stiff. adj it full soft, make sure your rear tire pressure cold is at least 3 lbs less than the front..... 30/27 for starters. you need to use a pyrometer to check your camber too. you want a bit more tire temp (20 degrees approx) in the inside 1/3rd of the tire. i don't think it is your spring balance front to rear as you have 566 f and 422 rear making your rear spring rate 43% of the total. my RS*Rs are 432 front 378 rear making my rear springs 46% of the total and my car is right on the money... (though i do run a larger rear wheel and tire than front.) so i don't think your f/r spring rate is an issue. i think the bar setting, tire pressure and camber are where i would look first. do make sure you move your battery and get everything out of your engine compartment but the engine.
as to offset....
take a stock wheel. lay it on a level surface. lay a straightedge across the top. find the distance between the top of the section width of the tire and the mounting surface. then measure from the mounting surface thru a stud hole to the floor. you now have the data to determine the mounting surface offset from the centerline of the tire which is the offset. do not deviate from this offset. BTW, the car is very happy w 245s up front. i just read a review of the new Honda 2000. they did alot of work on the chassis and mounted larger tires on the rear than the front to balance the car. rear engine cars like wider rear wheels. especially 20bs...
howard coleman
02-25-04, 08:43 PM
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Good info :-) I do plan on adjusting the rear roll bar to full soft. Tire pressures have been identical, car is corner weighted and there's nothing in the engine bay that I don't need there. I use the N-Tech BMK in a special place behind the driver's seat (not in the bin but inside the walls that make the bin). I'll make a few changes and see what I come up with.
02-26-04, 06:56 PM
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hey howard... i have no idea if you check this thread anymore, or if anyone has this info..... but i was wondering if anyone with a 20b FD has gotten the corner weights weighed? im trying to find ways to get more weight in the back to rebalance the car... i have a set of rear seats on the way to replace the bins (should add some weight with the extra belts and pannels), and this forces me to put hte battery in the trunk which is actually even better cause it will be further back.... i just need one HEAVY sealed battery! is a red top my best bet?
if that doesnt do it i can always throw a sand bag under the spare tire i suppose?
if that doesnt do it i can always throw a sand bag under the spare tire i suppose?
02-27-04, 03:02 PM
#37
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corner weights:
95 fd 3 rotor w 8 gallons of gas no occupants...
703.5 (lf) 691.5(rf)
664.5 (lr) 690 (rr)
2749 w 7 gal gas 50.7% front weight
2694 dry
95 fd 2 rotor (lots of weight reduction w rx6 turbo)
630 (lf) 655 (rf)
648 (lr) 624 (rr)
2557 w 8 gals gas no occupants 50.2% Front weight
3 rotor had relocated battery, 2 rotor had miniturized battery front location.
as you can see the 3 rotor has pretty good front rear weight distibution... removing the power steering, a-c along w it's condensor and various other items and you will be in good shape. if you do relocate your battery to a spot other than the package bin make sure it is on the floor of the spare tire bin. the center of gravity of a stock fd is 17 inches. low is fast.
the snow is starting to melt and Dick is in Alabama for a couple of months and he left me the 3 rotor keys so i will be doing some E11 tuning and plotting the bumpsteer in the next 2-3 weeks.
oh, on the Tein Flex vs Tein ha's.......... i think the difference is that the Flex is electronically adj. the rate and shock valving should be identical.
howard coleman
95 fd 3 rotor w 8 gallons of gas no occupants...
703.5 (lf) 691.5(rf)
664.5 (lr) 690 (rr)
2749 w 7 gal gas 50.7% front weight
2694 dry
95 fd 2 rotor (lots of weight reduction w rx6 turbo)
630 (lf) 655 (rf)
648 (lr) 624 (rr)
2557 w 8 gals gas no occupants 50.2% Front weight
3 rotor had relocated battery, 2 rotor had miniturized battery front location.
as you can see the 3 rotor has pretty good front rear weight distibution... removing the power steering, a-c along w it's condensor and various other items and you will be in good shape. if you do relocate your battery to a spot other than the package bin make sure it is on the floor of the spare tire bin. the center of gravity of a stock fd is 17 inches. low is fast.
the snow is starting to melt and Dick is in Alabama for a couple of months and he left me the 3 rotor keys so i will be doing some E11 tuning and plotting the bumpsteer in the next 2-3 weeks.
oh, on the Tein Flex vs Tein ha's.......... i think the difference is that the Flex is electronically adj. the rate and shock valving should be identical.
howard coleman
03-02-04, 06:22 PM
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Tires
RotorMotor I know you're concerned the the width of the rear tires. Have you ever concidered Pettit Flares in the rear. According to Pettit you can get a 12" wide wheels underneath the car. I wouldn't know the offset and if your concerned about the look you could take them to a metal crafter and have them make metal copies they will also installed. Here's a link to varies metal shops.
http://www.metalshapers.org/pros/
http://www.metalshapers.org/pros/
03-02-04, 09:51 PM
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Re: Tires
Originally posted by am3210
RotorMotor I know you're concerned the the width of the rear tires. Have you ever concidered Pettit Flares in the rear. According to Pettit you can get a 12" wide wheels underneath the car. I wouldn't know the offset and if your concerned about the look you could take them to a metal crafter and have them make metal copies they will also installed. Here's a link to varies metal shops.
http://www.metalshapers.org/pros/
RotorMotor I know you're concerned the the width of the rear tires. Have you ever concidered Pettit Flares in the rear. According to Pettit you can get a 12" wide wheels underneath the car. I wouldn't know the offset and if your concerned about the look you could take them to a metal crafter and have them make metal copies they will also installed. Here's a link to varies metal shops.
http://www.metalshapers.org/pros/
i know this has been discussed before but i though id ask your opinion howard as you see to know EVERYTHING
.... so does tire width really affect traction? if so what is the explanation (because i have gotten so many confliction stories both ways). thanks very much if you have any input 
-heath
03-02-04, 10:42 PM
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Greater tire width = larger traction pad actually contacting the ground = More traction!!
Think of this....What is faster on a road course a Full race preped..Motorcycle with a traction pad as big as your first three fingers or a F1 car with 4 traction pads as big as the whole of your hand? Which procuces the fastes lap times? More area = More Traction!
But then I'm no expert...I'm only starting to learn this stuff....Please feel free to correct me if I'm way off!!
Think of this....What is faster on a road course a Full race preped..Motorcycle with a traction pad as big as your first three fingers or a F1 car with 4 traction pads as big as the whole of your hand? Which procuces the fastes lap times? More area = More Traction!
But then I'm no expert...I'm only starting to learn this stuff....Please feel free to correct me if I'm way off!!
03-03-04, 02:41 AM
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no i am told this is not true (according to multiple people...as well as physics)... i know the physics explanation (i wont go through the whole thing) but if it is true in real world racing applications,why do cars with tons of power run such wide tires if they could get away with narrower ones (and therefore cut down on rotational mass)?
03-03-04, 11:16 AM
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Friction
RotorMotor you're right the Friction coefficient doesn't change based on width of the tire only compound can change that, but there are things you might want to think about. One with a wider tire you get the larger contact patch. So if you decide not to go with wide tires up front you could choose to go with a braking system that you can control the bias and you move more braking power to the rear. This will change your driving style for sure. Unfortunately no one on the board can afford any wind tunnel testing, so we may never how much drag fender flares will add to a RX7.
03-03-04, 11:36 AM
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Friction
RotorMotor you're right the Friction coefficient doesn't change based on width of the tire only compound can change that, but there are things you might want to think about. One with a wider tire you get the larger contact patch. So if you decide not to go with wide tires up front you could choose to go with a braking system that you can control the bias and you move more braking power to the rear. This will change your driving style for sure. Unfortunately no one on the board can afford any wind tunnel testing, so we may never how much drag fender flares will add to a RX7.
03-03-04, 11:42 AM
#45
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Well... see. Two things in favor of bigger tires.
First off, yes, coefficient of friction isn't determined by surface area. The thing is, coefficient of friction is not all that good of a model to simulate tire forces; it assumes non-deforming surfaces and a lot of other things. And quite simply, it doesn't conform to how tires behave.
*ADHESION* is where the majority of grip comes from. Literal stickiness. And adhesion *does* depend on surface area. Other major ones are deformation (simply rubber getting pressed into irregularies; like gear teeth in a way) and wear. http://www.insideracingtechnology.com/tirebkexerpt1.htm is a good look at the way tire grip actually does work.
The second reason for bigger tires is heating and wear. For a given level of energy transferred to the ground, some of it is going to be wasted and converted to heat. The total amount of heat is going to remain pretty constant no matter what. If it's converted to heat over a large surface area though, the average temperature will be lower... and the advantage of *that* should be obvious.
First off, yes, coefficient of friction isn't determined by surface area. The thing is, coefficient of friction is not all that good of a model to simulate tire forces; it assumes non-deforming surfaces and a lot of other things. And quite simply, it doesn't conform to how tires behave.
*ADHESION* is where the majority of grip comes from. Literal stickiness. And adhesion *does* depend on surface area. Other major ones are deformation (simply rubber getting pressed into irregularies; like gear teeth in a way) and wear. http://www.insideracingtechnology.com/tirebkexerpt1.htm is a good look at the way tire grip actually does work.
The second reason for bigger tires is heating and wear. For a given level of energy transferred to the ground, some of it is going to be wasted and converted to heat. The total amount of heat is going to remain pretty constant no matter what. If it's converted to heat over a large surface area though, the average temperature will be lower... and the advantage of *that* should be obvious.
03-03-04, 06:29 PM
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The laws of physics state friction is independent of surface area EXCEPT under extreme conditions. Whether or not a 500RWHP 3 rotor is "extreme" or not can be debated I guess :-) Porsche went with a 19 inch in the rear of the new GT to add contact patch and increase traction. They were able to increase the patch more that way than by going with a wider wheel. I am sure aerodynamics and packaging were also a concern. So maybe wider, 19 inch wheels is the solution.
03-04-04, 10:49 PM
#47
spoon!
Originally posted by rx7tt95
The laws of physics state friction is independent of surface area EXCEPT under extreme conditions.
The laws of physics state friction is independent of surface area EXCEPT under extreme conditions.
03-26-04, 04:58 PM
#49
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kenku......... you are right on the money. end of story.
pip... i'll bite, why should someone have called you?
btw, i will be doing the bump steer on the car immediately upon return next week from picking up my new motor from judge ito.
i will report as to how the bump steer it checks out along w a driving report after a touch of haltech tuning.
howard coleman
pip... i'll bite, why should someone have called you?
btw, i will be doing the bump steer on the car immediately upon return next week from picking up my new motor from judge ito.
i will report as to how the bump steer it checks out along w a driving report after a touch of haltech tuning.
howard coleman
03-29-04, 09:57 PM
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I Knew that all those lapping days that I sat in the classroom would pay off.....I did actually know something!!! Hey Howard....Hurry and test that pesky bump steer already.....I'm dying to find out what your results show!!! LOL!