The Better Bilstein Ebay Coilover Thread
#1322
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There's a lot written here, didn't follow all of it. I'll just add my 2 cents.
With adjustable spring perches (assuming perch height is infinitely adjustable, ie: able to cut new circlip grooves lower than stock perch), the only thing that matters about spring length is stack height. A 6" spring of 300 lb/in will be the exact same as a 7" spring of 300 lb/in with the spring perch moved 1" lower. Your long calculations on page 66 are valid if spring perches are fixed, but if you can move the lower perch, just get a spring that's the right rate and has enough travel, then adjust perch for ride height.
Preload doesn't directly matter for ride height. With equal perch heights (distance from lower perch, to lower eye), two springs of same length and same rate will have the same ride height, regardless of pre-load (disregarding slight ride height changes from nitrogen pre-charge and different piston locations at ride height). As you set the car down, the spring with preload will not move until preload is overcome (preload distance times spring rate) and then once full vehicle load is applied, it'll be at the same height as the non-preloaded spring. But, if these two examples had the same top hat design, then pre-load would directly correlate to perch position and ride height would be affected.
My theory for choosing perch heights/preload/etc on my car: run basic calcs or use baselines (stock, other peoples setups, etc) to get desired spring length and rate (make sure spring has enough travel for shock travel, you for sure want bump rubber before coil bind). Install and set ride heights with adjustable perch. Measure lower eye to perch length, perch to top hat (spring seat) length, and top hat to shock mount (the raised part of the top hat). Decide on a bump/droop ratio, perform heavy calculus, take the raw data and analyze it, make sure bump travel seems reasonable (because it's sometimes advantageous to have more droop than bump, unless it causes you to bottom out, bottom out equals unpredictable handling). These calculations will lead you to the "ideal" top hat height to get your bump/droop ratio, and you'll also be able to recalculate (or just assemble and test) if you need helper springs. If you do, lower spring perch for helper spring stack height. Now your ride heights may be a bit different, because your shock piston is in a new location which can affect total spring rate, so reset ride height and corner balance.
With adjustable spring perches (assuming perch height is infinitely adjustable, ie: able to cut new circlip grooves lower than stock perch), the only thing that matters about spring length is stack height. A 6" spring of 300 lb/in will be the exact same as a 7" spring of 300 lb/in with the spring perch moved 1" lower. Your long calculations on page 66 are valid if spring perches are fixed, but if you can move the lower perch, just get a spring that's the right rate and has enough travel, then adjust perch for ride height.
Preload doesn't directly matter for ride height. With equal perch heights (distance from lower perch, to lower eye), two springs of same length and same rate will have the same ride height, regardless of pre-load (disregarding slight ride height changes from nitrogen pre-charge and different piston locations at ride height). As you set the car down, the spring with preload will not move until preload is overcome (preload distance times spring rate) and then once full vehicle load is applied, it'll be at the same height as the non-preloaded spring. But, if these two examples had the same top hat design, then pre-load would directly correlate to perch position and ride height would be affected.
My theory for choosing perch heights/preload/etc on my car: run basic calcs or use baselines (stock, other peoples setups, etc) to get desired spring length and rate (make sure spring has enough travel for shock travel, you for sure want bump rubber before coil bind). Install and set ride heights with adjustable perch. Measure lower eye to perch length, perch to top hat (spring seat) length, and top hat to shock mount (the raised part of the top hat). Decide on a bump/droop ratio, perform heavy calculus, take the raw data and analyze it, make sure bump travel seems reasonable (because it's sometimes advantageous to have more droop than bump, unless it causes you to bottom out, bottom out equals unpredictable handling). These calculations will lead you to the "ideal" top hat height to get your bump/droop ratio, and you'll also be able to recalculate (or just assemble and test) if you need helper springs. If you do, lower spring perch for helper spring stack height. Now your ride heights may be a bit different, because your shock piston is in a new location which can affect total spring rate, so reset ride height and corner balance.
#1323
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Bilsteins with 6" springs on left. Xidas on right. Both have pretty close to oem droop travel (in fact, the Bilstein is oem droop travel, because well... it's the shocks that you purchased). Both require bump stops to avoid jamming the tire into the body of the cars. The Bilstein setup is EASILY capable of reaching your desired right heights. It is NOT capable of swallowing 12-14" springs without compressing them 2-4" for the sole purpose of being able to bolt on the top hats.
Spring length and shock shaft travel are not related and shock travel is not at all required to answer to spring travel.
#1325
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Originally Posted by Thucydides
I guess my first question is whether or not you believe in the concept of spring rate, or is that not a real world phenomena? For the sake of argument, let's say you do.
If the weight of the corner of your car supported by your spring is 702 lbs, and your OEM rear spring rate is 97 lbs/in (1994-1995), your spring is going to compress 702 / 97 = 7.2" Your formally 11.7" OEM spring is now 4.5" long. Not sure how to make this any simpler.
If the weight of the corner of your car supported by your spring is 702 lbs, and your OEM rear spring rate is 97 lbs/in (1994-1995), your spring is going to compress 702 / 97 = 7.2" Your formally 11.7" OEM spring is now 4.5" long. Not sure how to make this any simpler.
Your words: Not sure how to make this any simpler. 11.7-6.3 = 5.4. Now you are also not accounting for gas charge in the shock, which will resist compression nearly exponentially as it compresses as well as bushing stiction and/or torsional resistance of the bushing itself (depending on the bushing style). You would be surprised how hard bushings resist twisting motion.
What can I say. There's always the iterative approach.
Originally Posted by Thucydides
Bingo! Stiff springs require helpers, soft springs require preload.
Originally Posted by Thucydides
I'll be compressing them a good deal more than that!
Not correct. Spring preload is a byproduct of low spring rates, just like helper springs are a byproduct of high spring rates.
Not correct. Spring preload is a byproduct of low spring rates, just like helper springs are a byproduct of high spring rates.
Originally Posted by Thucydides
Droop is a function of the shock and the shock shaft limitations, and is not dictated by the spring. You need bump stops to avoid jamming the tire into the body of the car because the shock isn't designed, in this case, to limit bump travel to prevent putting your tire into fender. That's your bump stop's job. Preload, preload, preload....
Originally Posted by Thucydides
Spring length and shock shaft travel are not related and shock travel is not at all required to answer to spring travel.
Last edited by vteckiller2000; 02-16-2018 at 08:21 PM.
#1326
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The issue here is that in your theoretical setup, and my real world setup, there is/will be near as makes no difference the same amount of total travel. Your scenario is going to put your car at static height, at near top of its range. Especially at the higher height that you're talking. This will allow you next to no, if not zero droop travel. This is muchly bigly bad for the type of driving that you're talking about doing. As you succinctly said prior, you want to aim for the middle. You're doing everything in your power to not do that.
Spring travel is not measured in a vacuum. Shock travel has to be taken into play. When your shock runs out of downward travel, that's it. You're done, no matter what spring you have packed onto that thing. I think you've drastically overestimated the amount of adjustability you're going to have with these springs. As in you're not likely to be able to hit your lower ride height goals. And that's bad.
Another member of the 800lb (actually 850, thank you very much) and not using helper springs club checking in.
I hope this works out for you. I really do. Just in my experiences (and i've built a fair number of these setups, and developed these setups), you're going at this soooo far from how anyone else who has ever built one of these setups would, it makes my head spin. Bringing spring rates that a 1st gen rally Escort used into the discussion is completely irrelevant and has no bearing on these cars. These cars are absolutely horrendous on low rates like that. They generate way too much grip for low rates like that. And will even do that on crap roads like you're talking about. Absolutely not suggesting you run anything like the track day rates we all run, but if it were my car, i'd be looking at 350-400 in the front, 250-275 in the rear. And probably 7-8" springs at most, because those will give you your desired ride heights, not dislodge, and still have enough coil travel to match the shock.
The math is great. I don't understand it, nor do i really care to. There's hundreds of us that have done this "our way." And have logged thousands and thousands and thousands of miles on them. Expect to get some flak if you come in here (and my extensive write-up on the other forum) and start telling us we're all wrong because a piece of paper says so, with a setup you have no hands-on experience with.
Spring travel is not measured in a vacuum. Shock travel has to be taken into play. When your shock runs out of downward travel, that's it. You're done, no matter what spring you have packed onto that thing. I think you've drastically overestimated the amount of adjustability you're going to have with these springs. As in you're not likely to be able to hit your lower ride height goals. And that's bad.
Another member of the 800lb (actually 850, thank you very much) and not using helper springs club checking in.
I hope this works out for you. I really do. Just in my experiences (and i've built a fair number of these setups, and developed these setups), you're going at this soooo far from how anyone else who has ever built one of these setups would, it makes my head spin. Bringing spring rates that a 1st gen rally Escort used into the discussion is completely irrelevant and has no bearing on these cars. These cars are absolutely horrendous on low rates like that. They generate way too much grip for low rates like that. And will even do that on crap roads like you're talking about. Absolutely not suggesting you run anything like the track day rates we all run, but if it were my car, i'd be looking at 350-400 in the front, 250-275 in the rear. And probably 7-8" springs at most, because those will give you your desired ride heights, not dislodge, and still have enough coil travel to match the shock.
The math is great. I don't understand it, nor do i really care to. There's hundreds of us that have done this "our way." And have logged thousands and thousands and thousands of miles on them. Expect to get some flak if you come in here (and my extensive write-up on the other forum) and start telling us we're all wrong because a piece of paper says so, with a setup you have no hands-on experience with.
#1327
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The issue here is that in your theoretical setup, and my real world setup, there is/will be near as makes no difference the same amount of total travel. Your scenario is going to put your car at static height, at near top of its range. Especially at the higher height that you're talking. This will allow you next to no, if not zero droop travel. This is muchly bigly bad for the type of driving that you're talking about doing. As you succinctly said prior, you want to aim for the middle. You're doing everything in your power to not do that.
Spring travel is not measured in a vacuum. Shock travel has to be taken into play. When your shock runs out of downward travel, that's it. You're done, no matter what spring you have packed onto that thing. I think you've drastically overestimated the amount of adjustability you're going to have with these springs. As in you're not likely to be able to hit your lower ride height goals. And that's bad.
Another member of the 800lb (actually 850, thank you very much) and not using helper springs club checking in.
I hope this works out for you. I really do. Just in my experiences (and i've built a fair number of these setups, and developed these setups), you're going at this soooo far from how anyone else who has ever built one of these setups would, it makes my head spin. Bringing spring rates that a 1st gen rally Escort used into the discussion is completely irrelevant and has no bearing on these cars. These cars are absolutely horrendous on low rates like that. They generate way too much grip for low rates like that. And will even do that on crap roads like you're talking about. Absolutely not suggesting you run anything like the track day rates we all run, but if it were my car, i'd be looking at 350-400 in the front, 250-275 in the rear. And probably 7-8" springs at most, because those will give you your desired ride heights, not dislodge, and still have enough coil travel to match the shock.
The math is great. I don't understand it, nor do i really care to. There's hundreds of us that have done this "our way." And have logged thousands and thousands and thousands of miles on them. Expect to get some flak if you come in here (and my extensive write-up on the other forum) and start telling us we're all wrong because a piece of paper says so, with a setup you have no hands-on experience with.
Spring travel is not measured in a vacuum. Shock travel has to be taken into play. When your shock runs out of downward travel, that's it. You're done, no matter what spring you have packed onto that thing. I think you've drastically overestimated the amount of adjustability you're going to have with these springs. As in you're not likely to be able to hit your lower ride height goals. And that's bad.
Another member of the 800lb (actually 850, thank you very much) and not using helper springs club checking in.
I hope this works out for you. I really do. Just in my experiences (and i've built a fair number of these setups, and developed these setups), you're going at this soooo far from how anyone else who has ever built one of these setups would, it makes my head spin. Bringing spring rates that a 1st gen rally Escort used into the discussion is completely irrelevant and has no bearing on these cars. These cars are absolutely horrendous on low rates like that. They generate way too much grip for low rates like that. And will even do that on crap roads like you're talking about. Absolutely not suggesting you run anything like the track day rates we all run, but if it were my car, i'd be looking at 350-400 in the front, 250-275 in the rear. And probably 7-8" springs at most, because those will give you your desired ride heights, not dislodge, and still have enough coil travel to match the shock.
The math is great. I don't understand it, nor do i really care to. There's hundreds of us that have done this "our way." And have logged thousands and thousands and thousands of miles on them. Expect to get some flak if you come in here (and my extensive write-up on the other forum) and start telling us we're all wrong because a piece of paper says so, with a setup you have no hands-on experience with.
The car you drove home in, the airplane you flew in to visit Hawaii, the computer or iPad or cell phone you're reading this on, not to mention the Falcon Heavy that launched the Tesla into interplanetary orbit, were all designed using mathematical models. None of these things, nor any other complicated device we take for granted, would be possible without mathematical models. Let's think how a mathematical model works for a moment. Someone observes something, let's take a spring for example, and discovers, or think he discovers, that when the load on the spring is doubled it compresses twice as far. y=Cx and Bob's your uncle, spring rate. Now some nube has a problem with a hydraulic system and ask's some office type engineers how to spec a gauge to monitor the hydraulic system, and because they don't understand the full range of parameters of that particular hydraulic system, **** things up by an order of magnitude. Happened yesterday afternoon and everyone involved enjoyed roasting the nube responsible. The point is a that a mathematical model is a virtual representation of reality, and is only as useful if it accurately represents that reality. You have to have confidence in your model, and confidence comes from experience. I'm confident in my very simple model, and I believe I have an adequate understanding of its limitations. If I'm wrong, and everything goes to hell, I'll do what every good engineer does and ferret out the flaws in the model, readjust, and reapply. Landing rocket crashes onto floating barge, fix model, try again.
Anyway, all's I'm trying to do is put modify a completely unsuitable car to take me where I have no business going, and doing it in a manner that everyone says can't possible work. What could possibly go wrong?
I'm moving on to GRM because I think I've gotten all of the help I can possibly take over here
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Jim
#1329
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Doing another suspension swap at the moment and am taking the opportunity to measure bump/droop travel and sort out bump stop lengths and optimal extended tophat lengths. Car is a JDM NB1 - doing fronts first, will measure rear next. Pics:
![](https://i.imgur.com/atcBnmX.jpg)
![](https://i.imgur.com/XX5q1QX.jpg)
Notes:
- fender liner removed
- wheel is 205/45/16 - this is about 7mm taller than a 225/45/15.
- with this tire fully compressed with a stock length NB Bilstein shock the tire is just making contact with the chassis before the shock bottoms out. With the 15" tire i'm not sure if shock or tire would bottom first, either way it's so close we're at max compression without a bumpstop that it's within what I can easily measure.
Conclusion: Optimal tophat extension for using stock length nb bilsteins on a bilstein chassis is about the block-height of your bumpstops in the front. After that you're losing droop travel with no gain of compression travel possible (as you're tire's into the tub at that point).
![](https://i.imgur.com/atcBnmX.jpg)
![](https://i.imgur.com/XX5q1QX.jpg)
Notes:
- fender liner removed
- wheel is 205/45/16 - this is about 7mm taller than a 225/45/15.
- with this tire fully compressed with a stock length NB Bilstein shock the tire is just making contact with the chassis before the shock bottoms out. With the 15" tire i'm not sure if shock or tire would bottom first, either way it's so close we're at max compression without a bumpstop that it's within what I can easily measure.
Conclusion: Optimal tophat extension for using stock length nb bilsteins on a bilstein chassis is about the block-height of your bumpstops in the front. After that you're losing droop travel with no gain of compression travel possible (as you're tire's into the tub at that point).
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Had to stop for the night but will measure with extended tophats (have 1" and 1.5" to try) to see how much compression travel is available for the shock before the wheel bottoms on something.
#1330
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With a narrow tire it's pretty rediculous how much bump travel is available. A wider tire will of course find something to hit sooner. In the front it's usually the top hat/shock tower.
As a data point I found with a 245 mounted on a 9" 6ul I ended up with a 1" front bump stop. On the rear I had the same 1" bump stop but with a 1" extended top hat.
As a data point I found with a 245 mounted on a 9" 6ul I ended up with a 1" front bump stop. On the rear I had the same 1" bump stop but with a 1" extended top hat.
#1331
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With a narrow tire it's pretty rediculous how much bump travel is available. A wider tire will of course find something to hit sooner. In the front it's usually the top hat/shock tower.
As a data point I found with a 245 mounted on a 9" 6ul I ended up with a 1" front bump stop. On the rear I had the same 1" bump stop but with a 1" extended top hat.
As a data point I found with a 245 mounted on a 9" 6ul I ended up with a 1" front bump stop. On the rear I had the same 1" bump stop but with a 1" extended top hat.
#1332
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EDIT: Full disclosure, my calcs are all correct for the spring and shock parameter example, but I have not accounted for the proportionally higher force at the coil-over assembly vs the approx. corner weight measured at the tire. That force must be increased by the motion ratio of the suspension, the shock and spring see the corner weight (lets say 600 lbf) x the motion ratio (1.52, the proportion of moment arm length; think LEVER) = 912 lbf...so the spring length and preload requirements for the same "weight" should be higher. But again, provided measured loads at the shock, the math below checks out, but would only technically apply to a much lighter Miata...like a Lotus 7 replica or something, lol.
Leave a negcat if you want...I deserve it.
Not to beat this horse too much more, just breaking this down a bit, even though you may have permanently left this thread - so this could be for the benefit of others.
I ran some of your proposed numbers (14.5"-15" ride height, 200 lb/in front spring, 150 lb/in rear springs, 60:40 bump ratio) through my spreadsheet and found that an 8" or 9" front spring and 10" rear spring will easily accomplish the task on OEM NB Bilstein shock geometry, advanced autosports/allstar sleeves (at stock circlip height), and stock NB top hats in front and MAYBE a slightly deeper top hat at back.
Caveats:
1. My spreadsheet is still in development and I am verifying the measurements against my NA, but should be close enough.
2. You ordered the B6 shocks, which I think have slightly different body length than the OEM NB bilsteins, but likely almost the same stroke length? Close enough for quick verification and I just assumed a simple 5" stroke for the example below.
3. None of this considers the very real effect of control arm bushings on the spring loads and settled ride height.
You said this in reference to the suggestion that you would need to preload long, low-rate springs at least 3"-4" for some spring lengths you proposed. However, since you clearly defined desired spring rates of ~200 lb/in front and ~150 lb/in rear, and considering even conservative estimates of corner weights as 600 lbf front and 500 lbf rear, just 3" (600 lbf) front preload and 3.33" (500 lbf) rear preload would result in complete negation of the corner weight...keeping your shocks in full droop (fully extended) at rest under the weight of the car. As you surely agree that this would be BAD, and you defined a desired bump ratio of 60:40, you simply will not preload springs at these rates by even 3", let alone "a good deal more than that!"
Because you defined your desired bump ratio and we know the shock stroke length, we can immediately calculate the amount of preload you would want. I will pull up my spreadsheet once home tonight to verify numbers, but even assuming just 5" (actually, I think the OEM NB bilstein fronts are only 4.5") of total available stroke length on many of these shocks, and assuming bump travel WITHOUT a bump stop, your prescribed aim (not that I am advocating for or against) is 3" bump, 2" droop (60:40 ratio). Meaning, after preload and install, your coil-over assembly should compress 2 more inches from the corner weight when you lower it off the jack. As we already defined your desired spring rates as 200f/150r, the amount of spring load NOT due to preload should be 400 lbf front and 300 lbf rear (200lb/in x 2in and 150lb/in x 2in). Considering the assumed, conservative 600 lbf front corner weight and 500 lbf rear, the springs should be preloaded 200 lbf front (600-400) and 200 lbf rear (500-300), or 1" and 1.33" of SPRING preload compression, respectively. If each shock has 5" of stroke, the minimum required spring travel (for use when sourcing spring lengths) is the preload (1"f/1.33"r) plus the stroke, or 6" front and 6.33" rear total spring travel. Now...this should be more than enough, because it is not even accounting for the bump stop block (compressed) height. When I calculated this in my spreadsheet I actually subtracted the bump stop block height from the total available stroke, then determined the bump:droop travel from that...in the above case, assuming a 1" bump stop block height (for simplicity), the available stroke becomes 4" total, or 2.4" bump, 1.6" droop for a 60:40 ratio. If you want to look at it that way, then the "resting" spring load, after preload, in the above example, should be 320f/240r, increasing the spring preloads to 280f/260r, or 1.4" and 1.73" at their respective rates.
This is completely true IF you plan to use all of the available stroke with spring preload. But that truth is what limits YOU to a very specific, quickly-calculable suspension setup, because your droop travel is already set by the shock geometry and your desire for a roughly 60:40 bump ratio. For most of the setups in this thread, using much stiffer springs and desiring lower ride heights than you are, we end up with zero preload, reducing shock stroke by the gap between the spring and mount when the shock is fully extended. The usable droop travel is then only corner weight divided by spring rate, but with much-reduced bump travel, due to suspension geometry and the low ride height. Extending the top hats by the length of the aforementioned gap would allow for utilizing the same droop travel, but increased bump travel - still requiring even longer bumpstops to prevent tire-chassis contact. You can make a case for helper springs, but they are not going to do much more unless they are a high enough rate to overcome the combination of unsprung weight inertia and CA bushing preload. I would rather extend the top hats for longer, more-progressive bumpstop engagement, but there is a limit to that game.
They are not related, but this is why you have adjustment collars for height. However, adjusting the spring perch will vary your bump ratio, unless you change out the bumpstops (which is basically scaling the overall available travel) or adjust the top hat depth...maybe a competent welder can produce adjustable top hats out of some spare adjustment sleeves?? haha, that would be ideal, but slightly crazy.
I hope to hear back about your setup and wish you success with it, but I still think you could pull this off with mostly-stock components and slight adjustments, such as spring spacers, though you would lose the ability to adjust height.
![facepalm](https://www.miataturbo.net/images/smilies/facepalm.gif)
Not to beat this horse too much more, just breaking this down a bit, even though you may have permanently left this thread - so this could be for the benefit of others.
I ran some of your proposed numbers (14.5"-15" ride height, 200 lb/in front spring, 150 lb/in rear springs, 60:40 bump ratio) through my spreadsheet and found that an 8" or 9" front spring and 10" rear spring will easily accomplish the task on OEM NB Bilstein shock geometry, advanced autosports/allstar sleeves (at stock circlip height), and stock NB top hats in front and MAYBE a slightly deeper top hat at back.
Caveats:
1. My spreadsheet is still in development and I am verifying the measurements against my NA, but should be close enough.
2. You ordered the B6 shocks, which I think have slightly different body length than the OEM NB bilsteins, but likely almost the same stroke length? Close enough for quick verification and I just assumed a simple 5" stroke for the example below.
3. None of this considers the very real effect of control arm bushings on the spring loads and settled ride height.
You said this in reference to the suggestion that you would need to preload long, low-rate springs at least 3"-4" for some spring lengths you proposed. However, since you clearly defined desired spring rates of ~200 lb/in front and ~150 lb/in rear, and considering even conservative estimates of corner weights as 600 lbf front and 500 lbf rear, just 3" (600 lbf) front preload and 3.33" (500 lbf) rear preload would result in complete negation of the corner weight...keeping your shocks in full droop (fully extended) at rest under the weight of the car. As you surely agree that this would be BAD, and you defined a desired bump ratio of 60:40, you simply will not preload springs at these rates by even 3", let alone "a good deal more than that!"
Keep this in mind - the preload is less than the vehicle weight, so even a preloaded spring will compress further to take whatever vehicle weight is not accounted for by preload. From that point on, like I said earlier, any adjustment up or down will move the vehicle up or down.
I hope to hear back about your setup and wish you success with it, but I still think you could pull this off with mostly-stock components and slight adjustments, such as spring spacers, though you would lose the ability to adjust height.
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Last edited by JoeTheZoe; 02-21-2018 at 09:17 AM. Reason: Missed the motion ratio for spring calcs
#1333
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Ok. Wow. What a thread. I read all 67 pages. I understand most of the information it not all. The one thing I did not find a definitive answer for was extended top hats for 1999-2005 cars. Are they needed or not. Doward in post 777 indicates he uses the stock nb mounts with great success. Others have stated they needed extended hats on the NB cars. Here is my proposed setup.
1999 Miata
MSM Bilsteins (have them already)
500/350 7” springs
eneegy suspension spring isolators on top
Oem NB Tophats with new oem rubber parts
bumpstops trimmed for setup
delrin thrust washer under springs
All Star sleeve kit
Car will be on 15x8 6uls with aggressive street tires, not race tires. Sway bars are factory base model for 1999 but will be upgrading the front bar and plan on leaving the rear bar stock. Engine is stock and will be replaced with a high compression 1.8 build eventually.
Thanks for the help.
1999 Miata
MSM Bilsteins (have them already)
500/350 7” springs
eneegy suspension spring isolators on top
Oem NB Tophats with new oem rubber parts
bumpstops trimmed for setup
delrin thrust washer under springs
All Star sleeve kit
Car will be on 15x8 6uls with aggressive street tires, not race tires. Sway bars are factory base model for 1999 but will be upgrading the front bar and plan on leaving the rear bar stock. Engine is stock and will be replaced with a high compression 1.8 build eventually.
Thanks for the help.
#1334
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It depends on your desired ride height and how progressively you want to engage the bumpstops. With the mega-long-bodied Hard-S or MSM Bilsteins and an aggressively-low ride height, your bump stops will have to be pretty damn short to allow for any free bump travel before hitting the stops - but if the stops are that short and stiff, that transition will be more harsh. The trade-off would be to go with extended top hats and longer bumpstops, but still need to ensure you don't make tire-body contact when that bumpstop gets compressed to its limit. If you are sitting at a more moderate height, you can certainly stick with the stock top hats. So still a fairly subjective answer.
This is why everyone in the thread recommends just doing the job with the minimum required parts and then making adjustments once you sort out any deficiencies.
Last edited by JoeTheZoe; 02-20-2018 at 03:12 PM. Reason: Added last line.
#1335
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Thanks for the response. For ride height I’m looking to be at around 12.5” in the rear and 12.75” in the front. The extended tophats I guess could wait and I could set the car up and see what I measure for fravel before engaging the stops. Is there a minimum amount of travel one should aim for before the bump stops are engaged?
#1336
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I've seen a few figures thrown around in this thread, maybe like 1" or something, but don't quote me. I think there is more focus on maintaining at least a minimum bumpstop thickness, to control how harsh their engagement is. But someone with more experience and expertise should chime in on that. I know that controlling which bumpstop engages first (front vs rear) while cornering or hitting a bump mid-corner will greatly affect handling balance, such as if you engage the rear bumpstops well before the fronts from lateral acceleration, you are rapidly increasing effective rear spring rate and, therefore, reducing the FRC toward oversteer. Likewise, if you hit a bump mid-corner and the rear shock slams up into a short, stiff bumpstop, the potential to snap into a spin increases. But your spring rates, sway bars, and alignment all affect that, so it gets way more complex.
#1337
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Thanks for the response. For ride height I’m looking to be at around 12.5” in the rear and 12.75” in the front. The extended tophats I guess could wait and I could set the car up and see what I measure for fravel before engaging the stops. Is there a minimum amount of travel one should aim for before the bump stops are engaged?
#1338
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If you can get me more details about the tophat length you used when you have time that would help. Thanks y’all. Looking forward to gettig this all ironed out.
And yes yes I saw the 1” figure thrown around for travel as well. From what I gathered in this thread 1” was a good amount and anything less started looking like it was time to add extended tophats if you wanted the configuration to work well. I guess it would be better to say 1” or > of travel and bumpstop length >x.
And yes yes I saw the 1” figure thrown around for travel as well. From what I gathered in this thread 1” was a good amount and anything less started looking like it was time to add extended tophats if you wanted the configuration to work well. I guess it would be better to say 1” or > of travel and bumpstop length >x.
Last edited by mrmonk7663; 02-20-2018 at 04:27 PM.
#1339
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Ok. Wow. What a thread. I read all 67 pages. I understand most of the information it not all. The one thing I did not find a definitive answer for was extended top hats for 1999-2005 cars. Are they needed or not. Doward in post 777 indicates he uses the stock nb mounts with great success. Others have stated they needed extended hats on the NB cars. Here is my proposed setup.
1999 Miata
MSM Bilsteins (have them already)
500/350 7” springs
eneegy suspension spring isolators on top
Oem NB Tophats with new oem rubber parts
bumpstops trimmed for setup
delrin thrust washer under springs
All Star sleeve kit
Car will be on 15x8 6uls with aggressive street tires, not race tires. Sway bars are factory base model for 1999 but will be upgrading the front bar and plan on leaving the rear bar stock. Engine is stock and will be replaced with a high compression 1.8 build eventually.
Thanks for the help.
1999 Miata
MSM Bilsteins (have them already)
500/350 7” springs
eneegy suspension spring isolators on top
Oem NB Tophats with new oem rubber parts
bumpstops trimmed for setup
delrin thrust washer under springs
All Star sleeve kit
Car will be on 15x8 6uls with aggressive street tires, not race tires. Sway bars are factory base model for 1999 but will be upgrading the front bar and plan on leaving the rear bar stock. Engine is stock and will be replaced with a high compression 1.8 build eventually.
Thanks for the help.
See my posts literally a few above yours where I measure the need for extended tophats on a 99-05
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Short answers:
Fronts- if you have fender liners, you're probably close to maxing travel within a few mm's with OEM NB tophats. If you want to really max available travel, remove the fender liners, use short (3/4" or 1") extended tophats, longer bumpstops (as you don't need all 3/4" of an inch) and measure carefully your bumpstop block height so you don't put your tire too heavily into your chassis if there is some contact. There's not a lot to gain here though.
Rears- there's extra travel available for the wheel to move with an extended tophat. 1" to 1.5" is probably all you need though as with that you'll be able to bottom the tire on the tub. Again it depends on your bumpstop length and other things. 1" Extended with a decent bumpstop ~1.5" or longer is probably close to maxing travel.
Caveats- this is all approximate; everyone's setup differs so really you need to check yourself. Tire width matters (as will affect where the tires make contact first so how much travel there is), tire profile/total circumference also will change the available travel. Bushing /washer stack height/tophat details of where you're positioning the top of the shock shaft relative to everything else also makes a difference.