Suspension Upgrade Time: KW or Ohlins or FCM?
02-24-2017, 02:30 PM
#126
The main incoherent part of the journey had to do with spring rates. If my Bilstein information is correct, I increased front rates by a net of about 105lbs by installing Ohlins. That should induce some understeer, which should mean I would need a little less front bar or a little more rear bar. The opposite occurred, however. When set up "correctly," I experienced massive oversteer everywhere. From there, I did all the normal incremental adjustments: ride height, tire pressures, sway bars, rebound, alignment. Things got marginally better, but never "right" like it had been before.
One day, while frustrated at the track, I crawled under the car and just disconnected the rear OEM bar on one side. That resulted in manageable understeer, and that was the epiphany. With a tiny little MX-5 rear bar, the car is mostly neutral, but it still has a tendency toward snap oversteer when pushing it really hard. As mentioned before, there is really no rhyme or reason to why it happens, so there is no obvious fix. I could probably sort it out if I had a toolbox at the track and all day to try random things, but I never have that opportunity.
One day, while frustrated at the track, I crawled under the car and just disconnected the rear OEM bar on one side. That resulted in manageable understeer, and that was the epiphany. With a tiny little MX-5 rear bar, the car is mostly neutral, but it still has a tendency toward snap oversteer when pushing it really hard. As mentioned before, there is really no rhyme or reason to why it happens, so there is no obvious fix. I could probably sort it out if I had a toolbox at the track and all day to try random things, but I never have that opportunity.
I wish I knew enough about suspension to even speculate on why that happened.
It could be something in the magic valving acting up at the extremes. I, too, have wondered that. I have heard the same thing about Koni FSD shocks. Maybe the rebound falls off and allows a spring to launch one or more corners of the car just enough to cause it to lose grip, but not enough for me to feel it from the factory seat?
So as far as I know, both the Koni FSD and Ohlins DFV use valves that open with high frequency movements to greatly reduce damping forces in those circumstances. Theoretically, if the valves don't react quickly enough or otherwise don't always open/close at the right time, there could indeed be moments where you end up with way less damping than would be optimal. I'd imagine the effect would be transient enough that it'd be hard to detect.
Have you spoken with Ohlins or SBG or anyone else about this? Seems really strange.
Noooooo! This thread is pretty much the only thing on RX8Club that's living up to what I had hoped for when I bought the car, lol...
02-25-2017, 08:09 AM
#127
Water Foul
Thread Starter
Short of spending a bunch more money, it seems there isn't much left to do. Here are the options as I see them:
1. Buy the GWR adapter and other hardware needed to bump the rear springs to 280 lbs. That buys me more rear bump travel and a F/R ratio of 1.6 A side benefit is the ability to use any spring rates going forward, assuming I am willing to pay for re-valving. I have not actually priced this, but let's call it the $500 option. Tein (Blech!) makes a tapered spring in 280, but it is 250mm high, which is too tall for the shock body, which leads us to...
2. Buy a set of Tein (blech!) 336 lbs tapered (70-100x200) springs for the rear, and bump the fronts up 1K to 504 lbs. F/R ratio would be 1.5. If I use all Tein (blech!) springs, the cost would be $275 for the springs. Swift fronts would bump the price about $60. Ohlins told me I can increase spring rates 35% before a re-valve is required. The rears would exceed that. Re-valving costs $250 each plus shipping both ways. This option looks like at least $800.
3. Do nothing, drive the car for joy instead of speed, and put the money into the kitty for the Miata's turbo.
.
Last edited by Steve Dallas; 02-25-2017 at 08:12 AM.
02-25-2017, 10:58 AM
#128
Registered
If you increased your grip by adding tire and you are snap under/oversteering, it is likely caused by suspension travel being maxed out. Do the zip-tie test (zip-tie around shock rod and against the shock body, drive, then see where it's at).
Sway bars add a lot of roll stiffness. To achieve the same effect with springs, you have to go much higher than you think on spring rates.
Note that this has nothing to do with the shock. Dampers react to shock body velocity (considering a static shock rod). They don't add stiffness. They might make you think they do while you are in a transient state (i.e. before the car settles). The way to test this is in the middle of a long sweeper turn.
Sway bars add a lot of roll stiffness. To achieve the same effect with springs, you have to go much higher than you think on spring rates.
Note that this has nothing to do with the shock. Dampers react to shock body velocity (considering a static shock rod). They don't add stiffness. They might make you think they do while you are in a transient state (i.e. before the car settles). The way to test this is in the middle of a long sweeper turn.
Last edited by etzilon; 02-25-2017 at 11:54 PM.
02-26-2017, 10:29 AM
#129
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Interesting comments, Steve.
Like you, I run the Öhlins street version from GWR (actually based on your initial reviews) and I've also found my car a little more dorifto spec than I like. I originally suspected that I was overheating the tires (RS-3), but your experience suggests that it's probably springs.
Time to play with swaybars and maybe rear spring rates then...
Like you, I run the Öhlins street version from GWR (actually based on your initial reviews) and I've also found my car a little more dorifto spec than I like. I originally suspected that I was overheating the tires (RS-3), but your experience suggests that it's probably springs.
Time to play with swaybars and maybe rear spring rates then...
02-27-2017, 08:24 AM
#130
don't know if this is re-post but ran across this site and found it very insightful and educational about all aspects of setting up the car to perform/handle optimally.
he also talked in detail about how useless (inaccurate - non linear, etc) are the damping adjusters on the most but most expensive systems(Penske). Also importance of having matched shocks and how most of the self shocks are not very consistent....
"The single most important part of the whole suspension system is THE TIRE. Tires are absolutely, positively, hey-Joe-no-foolin THE most dominant part of the suspension. Being on the right tire for the job at hand will buy you more time than any single other suspension improvement, and in terms of autocrossing (and road racing, to a point) tires buy you more time than anything outside of more seat time - PERIOD."
Autocross to Win (DGs Autocross Secrets) - ATW Home Page
he also talked in detail about how useless (inaccurate - non linear, etc) are the damping adjusters on the most but most expensive systems(Penske). Also importance of having matched shocks and how most of the self shocks are not very consistent....
"The single most important part of the whole suspension system is THE TIRE. Tires are absolutely, positively, hey-Joe-no-foolin THE most dominant part of the suspension. Being on the right tire for the job at hand will buy you more time than any single other suspension improvement, and in terms of autocrossing (and road racing, to a point) tires buy you more time than anything outside of more seat time - PERIOD."
Autocross to Win (DGs Autocross Secrets) - ATW Home Page
Last edited by Nadrealista; 02-27-2017 at 08:27 AM.
02-28-2017, 11:10 AM
#133
Water Foul
Thread Starter
^ Why do you assume I haven't? I'm pretty sure I covered beating all the Taiwanese and Japanese junk on page 1. And what does the type of engine have to do with suspension tuning?
02-28-2017, 03:12 PM
#135
I am running 8/6 on my FD. one thing I had to do to stay off the bump stops is add spring preload.
How much spring preload do you have on the rear of your ohlins dfv? You may need to better center your shock travel droop/bump with spring preload.
I would try that first and see what happens.
How much spring preload do you have on the rear of your ohlins dfv? You may need to better center your shock travel droop/bump with spring preload.
I would try that first and see what happens.
03-01-2017, 10:07 AM
#136
Water Foul
Thread Starter
Ohlins preload is independent of ride height. I am running about 2mm, as recommended in the instructions.
I may be running too low for these spring rates. Ride height is limited by the rear lower threaded cup. I have it on the list to set the rear as high as possible, which won't be terribly high, and raise the front to match. That will give me some additional bump travel. The penalty for raising it up is less negative camber, and I need all of that I can get.
There is also a bump stop spacer I could remove to gain another 5mm or so. Removing that may cause rubbing when bottoming out without more spring.
.
I may be running too low for these spring rates. Ride height is limited by the rear lower threaded cup. I have it on the list to set the rear as high as possible, which won't be terribly high, and raise the front to match. That will give me some additional bump travel. The penalty for raising it up is less negative camber, and I need all of that I can get.
There is also a bump stop spacer I could remove to gain another 5mm or so. Removing that may cause rubbing when bottoming out without more spring.
.
Last edited by Steve Dallas; 03-01-2017 at 10:23 AM.
03-01-2017, 12:12 PM
#137
Ohlins preload is independent of ride height. I am running about 2mm, as recommended in the instructions.
I may be running too low for these spring rates. Ride height is limited by the rear lower threaded cup. I have it on the list to set the rear as high as possible, which won't be terribly high, and raise the front to match. That will give me some additional bump travel. The penalty for raising it up is less negative camber, and I need all of that I can get.
There is also a bump stop spacer I could remove to gain another 5mm or so. Removing that may cause rubbing when bottoming out without more spring.
.
I may be running too low for these spring rates. Ride height is limited by the rear lower threaded cup. I have it on the list to set the rear as high as possible, which won't be terribly high, and raise the front to match. That will give me some additional bump travel. The penalty for raising it up is less negative camber, and I need all of that I can get.
There is also a bump stop spacer I could remove to gain another 5mm or so. Removing that may cause rubbing when bottoming out without more spring.
.
exactly. it is independent. Just for an easy math sake for argument since I don't know the exacts of the rear of the rx8 since I have not measured them.
if the rear suspension has 3" of travel, with a 1 inch bump stop. you have 2" of free travel in the suspension.
If your car weighs around 2800lbs with a person in it at a 50/50 weight distribution, I already took out all of the unsprung mass, so say each corner is roughly 670lbs on it.
the spring rate is 228lbs/in.
If no preload is placed on the spring (2mm is effectively that), your cars weight will naturally compress the spring 2.93" without any prelude. so effectively in this scenario you are riding on the bumpstops.
Now if you put 1.5" of spring preload on the spring, now you have 342lbs already on the spring. so now the spring compresses 1.44" when you place the car down.and you have .56" of free travel before the bump stop even engages.
I can't remember the exact numbers but I think I compressed my rear spring .75" or 250lbs of force for my rx7. the rear on the car with me in it has like 650lbs on each corner, so I compress the rear of my ohlins about 1.2" when the car comes off the stands under natural weight, then I have another 1" or so of free travel and then I contact the bump stop and have so much compression there. I haven't had any weird snap oversteer events in the car so far.
I would definitely try this first. however much you compress the spring is how much you need to go down in your lower perch to keep your alignment and ride height the same.
03-01-2017, 03:41 PM
#138
All that Bilstein stuff is indeed confusing. So, I called Bilstein tech support about 3 years ago and asked for the straight dope. The effective rates, which are the ones that matter in practical application, and should take helpers and progressive springs (how does one do that?) into account as much as possible, were given to me as:
PSS
370F 240R = 1.54
PSS9
340F 240R = 1.42
.
front is 65 N/mm or 371 lb/in
rear is 40 N/mm or 228 lb/in
he did not give me helper spring rate that is also used in both. emailed them back about that. let's see what they say.
03-02-2017, 01:53 PM
#139
Water Foul
Thread Starter
exactly. it is independent. Just for an easy math sake for argument since I don't know the exacts of the rear of the rx8 since I have not measured them.
if the rear suspension has 3" of travel, with a 1 inch bump stop. you have 2" of free travel in the suspension.
If your car weighs around 2800lbs with a person in it at a 50/50 weight distribution, I already took out all of the unsprung mass, so say each corner is roughly 670lbs on it.
the spring rate is 228lbs/in.
If no preload is placed on the spring (2mm is effectively that), your cars weight will naturally compress the spring 2.93" without any prelude. so effectively in this scenario you are riding on the bumpstops.
Now if you put 1.5" of spring preload on the spring, now you have 342lbs already on the spring. so now the spring compresses 1.44" when you place the car down.and you have .56" of free travel before the bump stop even engages.
I can't remember the exact numbers but I think I compressed my rear spring .75" or 250lbs of force for my rx7. the rear on the car with me in it has like 650lbs on each corner, so I compress the rear of my ohlins about 1.2" when the car comes off the stands under natural weight, then I have another 1" or so of free travel and then I contact the bump stop and have so much compression there. I haven't had any weird snap oversteer events in the car so far.
I would definitely try this first. however much you compress the spring is how much you need to go down in your lower perch to keep your alignment and ride height the same.
if the rear suspension has 3" of travel, with a 1 inch bump stop. you have 2" of free travel in the suspension.
If your car weighs around 2800lbs with a person in it at a 50/50 weight distribution, I already took out all of the unsprung mass, so say each corner is roughly 670lbs on it.
the spring rate is 228lbs/in.
If no preload is placed on the spring (2mm is effectively that), your cars weight will naturally compress the spring 2.93" without any prelude. so effectively in this scenario you are riding on the bumpstops.
Now if you put 1.5" of spring preload on the spring, now you have 342lbs already on the spring. so now the spring compresses 1.44" when you place the car down.and you have .56" of free travel before the bump stop even engages.
I can't remember the exact numbers but I think I compressed my rear spring .75" or 250lbs of force for my rx7. the rear on the car with me in it has like 650lbs on each corner, so I compress the rear of my ohlins about 1.2" when the car comes off the stands under natural weight, then I have another 1" or so of free travel and then I contact the bump stop and have so much compression there. I haven't had any weird snap oversteer events in the car so far.
I would definitely try this first. however much you compress the spring is how much you need to go down in your lower perch to keep your alignment and ride height the same.
Just got email back from Bilstein about the spring rates for springs used in their b14 and b16:
front is 65 N/mm or 371 lb/in
rear is 40 N/mm or 228 lb/in
he did not give me helper spring rate that is also used in both. emailed them back about that. let's see what they say.
front is 65 N/mm or 371 lb/in
rear is 40 N/mm or 228 lb/in
he did not give me helper spring rate that is also used in both. emailed them back about that. let's see what they say.
Interesting that 3 or more people can ask Bilstein about spring rates for a single product and receive different answers all around. My memory is a bit fuzzy, but I vaguely remember the helpers being near 0 rate and fully compressed under droop, so they should have minimal impact on spring rates.
03-03-2017, 08:53 AM
#140
Just got email back from Bilstein about the spring rates for springs used in their b14 and b16:
front is 65 N/mm or 371 lb/in
rear is 40 N/mm or 228 lb/in
he did not give me helper spring rate that is also used in both. emailed them back about that. let's see what they say.
front is 65 N/mm or 371 lb/in
rear is 40 N/mm or 228 lb/in
he did not give me helper spring rate that is also used in both. emailed them back about that. let's see what they say.
that would make total front spring rate of 451 lb/in on the b14 and b16 coilover
is that correct?
Can you just add the main spring to helper spring rate to get the total?
03-03-2017, 10:26 AM
#141
I guess you cant add helper spring rate to main spring rate to get the total rate:
From SwiftSprings:
"Helper Springs
Helper springs prevent dismounting of springs from perch on coilover without changing spring rate.
Unlike our assist springs, our helper springs are specifically designed to have a minimal effect on the spring rate of the main coilover spring. Helper springs allow the spring to stay on mounted on the coilover perch when the shock is under negative or zero load, also known as droop travel. It is ideal to run helper springs on setups where you cannot preload the main spring due to height issues or when experiencing springs coming loose from the coilover perch."
From SwiftSprings:
"Helper Springs
Helper springs prevent dismounting of springs from perch on coilover without changing spring rate.
Unlike our assist springs, our helper springs are specifically designed to have a minimal effect on the spring rate of the main coilover spring. Helper springs allow the spring to stay on mounted on the coilover perch when the shock is under negative or zero load, also known as droop travel. It is ideal to run helper springs on setups where you cannot preload the main spring due to height issues or when experiencing springs coming loose from the coilover perch."
03-03-2017, 11:16 AM
#142
Water Foul
Thread Starter
The words "helper" and "tender" have different meanings. Unfortunately, they are used interchangeably. In my mind, a tender is a near zero rate spring that only serves to hold the main spring in place under droop. A helper (aka assist) is a spring with enough rate to add rate (or effective preload) to the suspension in its corner under load.
In the RX-8 suspension, I would think an 80lb spring would be enough to contribute to the suspension and qualify it as a helper. But, I don't think the information they gave you is correct. I remember being able to easily compress that spring more than 1" with one hand, when assembling my coilovers. I could not do that with an 80lb spring. I would have to lean on it. That leads me to believe it is under 20lbs and is more of a tender than a helper. I could be wrong, though.
Anecdotally, I can tell you I have 460lb springs now, and my PSS9 springs were NOT 451lbs.
.
In the RX-8 suspension, I would think an 80lb spring would be enough to contribute to the suspension and qualify it as a helper. But, I don't think the information they gave you is correct. I remember being able to easily compress that spring more than 1" with one hand, when assembling my coilovers. I could not do that with an 80lb spring. I would have to lean on it. That leads me to believe it is under 20lbs and is more of a tender than a helper. I could be wrong, though.
Anecdotally, I can tell you I have 460lb springs now, and my PSS9 springs were NOT 451lbs.
.
Last edited by Steve Dallas; 03-03-2017 at 11:18 AM.
03-04-2017, 09:45 AM
#143
If you have height adjustment and spring preload adjustments you do not want a helper spring. a helper springs sole purpose is to take up the slack when the suspension droops. A spring that have an 80in/lbs spring rate will be completely collapsed with the cars weight on it. if each corner has around 650-700lbs, it means that the helper spring will be completely collapsed and the main spring will compress 650-700lbs.
putting preload on a spring means that you are essentially eliminating spring compression when the car drops on the ground. you preload 200lbs and the car only compresses the spring 450-500lbs, 200lbs is already preloaded into the spring so the spring compresses less getting you a different bump/droop ratio.
putting preload on a spring means that you are essentially eliminating spring compression when the car drops on the ground. you preload 200lbs and the car only compresses the spring 450-500lbs, 200lbs is already preloaded into the spring so the spring compresses less getting you a different bump/droop ratio.
03-04-2017, 11:47 AM
#144
If you have height adjustment and spring preload adjustments you do not want a helper spring. a helper springs sole purpose is to take up the slack when the suspension droops. A spring that have an 80in/lbs spring rate will be completely collapsed with the cars weight on it. if each corner has around 650-700lbs, it means that the helper spring will be completely collapsed and the main spring will compress 650-700lbs.
putting preload on a spring means that you are essentially eliminating spring compression when the car drops on the ground. you preload 200lbs and the car only compresses the spring 450-500lbs, 200lbs is already preloaded into the spring so the spring compresses less getting you a different bump/droop ratio.
putting preload on a spring means that you are essentially eliminating spring compression when the car drops on the ground. you preload 200lbs and the car only compresses the spring 450-500lbs, 200lbs is already preloaded into the spring so the spring compresses less getting you a different bump/droop ratio.
03-04-2017, 12:00 PM
#145
exactly. it is independent. Just for an easy math sake for argument since I don't know the exacts of the rear of the rx8 since I have not measured them.
if the rear suspension has 3" of travel, with a 1 inch bump stop. you have 2" of free travel in the suspension.
If your car weighs around 2800lbs with a person in it at a 50/50 weight distribution, I already took out all of the unsprung mass, so say each corner is roughly 670lbs on it.
the spring rate is 228lbs/in.
If no preload is placed on the spring (2mm is effectively that), your cars weight will naturally compress the spring 2.93" without any prelude. so effectively in this scenario you are riding on the bumpstops.
Now if you put 1.5" of spring preload on the spring, now you have 342lbs already on the spring. so now the spring compresses 1.44" when you place the car down.and you have .56" of free travel before the bump stop even engages.
I can't remember the exact numbers but I think I compressed my rear spring .75" or 250lbs of force for my rx7. the rear on the car with me in it has like 650lbs on each corner, so I compress the rear of my ohlins about 1.2" when the car comes off the stands under natural weight, then I have another 1" or so of free travel and then I contact the bump stop and have so much compression there. I haven't had any weird snap oversteer events in the car so far.
I would definitely try this first. however much you compress the spring is how much you need to go down in your lower perch to keep your alignment and ride height the same.
if the rear suspension has 3" of travel, with a 1 inch bump stop. you have 2" of free travel in the suspension.
If your car weighs around 2800lbs with a person in it at a 50/50 weight distribution, I already took out all of the unsprung mass, so say each corner is roughly 670lbs on it.
the spring rate is 228lbs/in.
If no preload is placed on the spring (2mm is effectively that), your cars weight will naturally compress the spring 2.93" without any prelude. so effectively in this scenario you are riding on the bumpstops.
Now if you put 1.5" of spring preload on the spring, now you have 342lbs already on the spring. so now the spring compresses 1.44" when you place the car down.and you have .56" of free travel before the bump stop even engages.
I can't remember the exact numbers but I think I compressed my rear spring .75" or 250lbs of force for my rx7. the rear on the car with me in it has like 650lbs on each corner, so I compress the rear of my ohlins about 1.2" when the car comes off the stands under natural weight, then I have another 1" or so of free travel and then I contact the bump stop and have so much compression there. I haven't had any weird snap oversteer events in the car so far.
I would definitely try this first. however much you compress the spring is how much you need to go down in your lower perch to keep your alignment and ride height the same.
From the various comments, it does seem like the bump stops are having a significant effect on front-to-rear spring ratios with the ohlins. My own experience is that bump stops will come into play even with fairly stiff springs (~425/375 or higher) when the car is at a reasonable ride height for the track (~13.5in from hub to wheel arch). If the bump stops engage at different rates, and grip does not change, then using sway bars, or different spring rates, can effectively compensate.
Things get harder if you want something that works well across different levels of grip, as then you need to make sure the front and rear bump stops are adding spring rate at the same rate (so the balance of the car does not change as the bump stops are engaged). I think the effect of bump stop compression changing car balance is part of the reason why my setup would understeer more as grip increased, but then be very tail happy in the wet. Disconnecting the rear sway bar would fix my wet handling, but I have since started tuning by changing the bump stops, and am now ready to add (or remove) packers that change the engagement height of the bump stop...
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sharingan 19 (07-18-2021)
03-04-2017, 10:36 PM
#146
I'm slightly confused... Can you adjust shock body length and spring perch height? Otherwise, are you simply adjusting spring perch height to raise the car, which will have the effect of keeping it further from the bump stops?
From the various comments, it does seem like the bump stops are having a significant effect on front-to-rear spring ratios with the ohlins. My own experience is that bump stops will come into play even with fairly stiff springs (~425/375 or higher) when the car is at a reasonable ride height for the track (~13.5in from hub to wheel arch). If the bump stops engage at different rates, and grip does not change, then using sway bars, or different spring rates, can effectively compensate.
Things get harder if you want something that works well across different levels of grip, as then you need to make sure the front and rear bump stops are adding spring rate at the same rate (so the balance of the car does not change as the bump stops are engaged). I think the effect of bump stop compression changing car balance is part of the reason why my setup would understeer more as grip increased, but then be very tail happy in the wet. Disconnecting the rear sway bar would fix my wet handling, but I have since started tuning by changing the bump stops, and am now ready to add (or remove) packers that change the engagement height of the bump stop...
From the various comments, it does seem like the bump stops are having a significant effect on front-to-rear spring ratios with the ohlins. My own experience is that bump stops will come into play even with fairly stiff springs (~425/375 or higher) when the car is at a reasonable ride height for the track (~13.5in from hub to wheel arch). If the bump stops engage at different rates, and grip does not change, then using sway bars, or different spring rates, can effectively compensate.
Things get harder if you want something that works well across different levels of grip, as then you need to make sure the front and rear bump stops are adding spring rate at the same rate (so the balance of the car does not change as the bump stops are engaged). I think the effect of bump stop compression changing car balance is part of the reason why my setup would understeer more as grip increased, but then be very tail happy in the wet. Disconnecting the rear sway bar would fix my wet handling, but I have since started tuning by changing the bump stops, and am now ready to add (or remove) packers that change the engagement height of the bump stop...
I am speaking with experience with Ohlins DFV from an rx7, the RX8 will be the same way except I have taken no measurements from the RX8.
The DFV on the rx7 came with spring rates of 11/11 stock. I installed those rates and when driven on the street (canyon roads) the car was difficult to drive and uncomfortable. It was literally jumping all over the place and doing weird jacking up and down motions over bumps. I also was darting across the road at high speeds.
I dropped the spring rates to 8/6 on the car from 11/11. I would drive the car on the same road and I honestly couldn't even feel the bumps anymore that were giving me problems. the tires and myself were much happier. I could lay down 4th gear at WOT up to 140mph (it doesn't take long to get there in a 400WHP car) and the car was planted and stable. I am running high damping ratio's with soft spring rates for the driving I do.
Anyway to the point, I used the stock settings when I did the 11/11 spring rates 1mm preload or so. The 8/6 I have to better balance the bump and droop of the suspension since there isn't much stroke in the rear of the rx7 so I added preload to balance that droop and bump ratio. I left the ohlins bump stops there obviously. I don't have any weird oversteer situations or understeer with .25" preload on the front and about .75" to 1" in the rear.
With as soft a spring rate as the rear of the ohlins dfv on the rx8, I wonder if you need to add some preload to the rear springs to get off the bump stops.
I think a better approach to tuning the suspension is adding preload to the springs and running more off the spring rate and less off the bump stops. Bump stops work great on stock suspensions where you have rules, but if you can add some preload go for it. the spring will be compressed the same amount when the car is on the ground, preloaded or not, the only difference is you have a bunch more bump travel.
I am willing to bet if you preload the spring 1" or so it will take care of your problems if its a 228lbsish spring rate, you will have plenty of droop travel.
and to disclose, I am a big fan of soft spring rates. I am running stock shocks and swift springs on my rx8. it could use a little more rate but its fun and cheap. spring rates are 207lbs front and 129lbs rear, 13.5 to 13.75" hub to fender measurements.
Last edited by lOOkatme; 03-04-2017 at 10:41 PM.
03-17-2017, 02:13 PM
#147
The words "helper" and "tender" have different meanings. Unfortunately, they are used interchangeably. In my mind, a tender is a near zero rate spring that only serves to hold the main spring in place under droop. A helper (aka assist) is a spring with enough rate to add rate (or effective preload) to the suspension in its corner under load.
In the RX-8 suspension, I would think an 80lb spring would be enough to contribute to the suspension and qualify it as a helper. But, I don't think the information they gave you is correct. I remember being able to easily compress that spring more than 1" with one hand, when assembling my coilovers. I could not do that with an 80lb spring. I would have to lean on it. That leads me to believe it is under 20lbs and is more of a tender than a helper. I could be wrong, though.
Anecdotally, I can tell you I have 460lb springs now, and my PSS9 springs were NOT 451lbs.
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In the RX-8 suspension, I would think an 80lb spring would be enough to contribute to the suspension and qualify it as a helper. But, I don't think the information they gave you is correct. I remember being able to easily compress that spring more than 1" with one hand, when assembling my coilovers. I could not do that with an 80lb spring. I would have to lean on it. That leads me to believe it is under 20lbs and is more of a tender than a helper. I could be wrong, though.
Anecdotally, I can tell you I have 460lb springs now, and my PSS9 springs were NOT 451lbs.
.
06-10-2017, 10:29 AM
#148
Water Foul
Thread Starter
I had some time this morning, so I raised the rear 1/4", without relieving any preload. The car is essentially level with 170lbs in the driver seat and a full tank of gas. That will introduce some positive rake as the tank drops in level. I should see a bit more bump travel from the added height and preload. I'll see how it works and report back. It might be a while, as I am taking the Miata to the track pretty much every time.
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