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Discussion Starter #1
"Commonly manufactured from closed-cell foam, the jounce bumper absorbs impact and dampens noise, vibration and harshness (NVH) by preventing the articulated suspension components from fully compacting during shock impacts caused by heavy loads, potholes, curbs or objects in the road."

OK. This seems to be what a lot of our Smarts are most beholden to. This is what our Smarts need tuned to our needs for our vehicle application. This is the point of control of the bump stop or bottoming out noise. To find a Jounce Bumper that is tailored to our Smart car issues is the goal.

Now having said that, I have no idea about this thing, so I am about to read up on it. But any Shock Engineers chime right in and get us pointed in the right direction.
 

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Darn, twcom's on a mission to change the status quo on the fortwo suspension. Count me in on watching this!

To anyone confused, a jounce bumper is more commonly known as a bump stop. I never thought about how changing the car's bump stops could change suspension behaviour.
 

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Discussion Starter #3
Darn, twcom's on a mission to change the status quo on the fortwo suspension. Count me in on watching this!

To anyone confused, a jounce bumper is more commonly known as a bump stop. I never thought about how changing the car's bump stops could change suspension behaviour.
LOL I am trying to learn about Bumpstops.

It does appear that strut bump stops may be something that can be "tuned" to a specific need or vehicle application. Here is a video that shows just how variable a bump stop set up can be. So I think I am looking for a bump stop for My smart that allows more suspension Travel when I hit a hard bump by springing the sprung weight up just a bit at the point the bump stock is engaged. By giving just a bit it will allow my tire to retract up away from the bump and at the same time the wheel well (part of the sprung weight) also retracts up just a bit due to the action of Bump Stop so the tire and the wheel well don't make contact.

Back to reading so I can understand what I think I just typed. Mean time here is the video that shows how much Bump Stop variation shock tuners may use.

Could this be our demon?

https://youtu.be/iIYdjerfFPg
 

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Discussion Starter #5
If you are serious you can contact these guys- Automotive Suspension Experts | Fat Cat Motorsports, Inc. | Bump stop technical information and application guide

They are the end all be all of bump stop tuning for the Mazda community and will consult on any project for a fee.
I contacted them and will see how their process works. I filled out the pre consult inquiry and also registered for their form. Mean time by keeping the chassis lubed on my Smart all initial harshness has been removed from my suspension. Suspension travel is fine on most road irregularities but on hard bumps and pot holes could use bump stop improvement. I have driven 2500 miles in last 2weeks. Car is doing great. Thanks for this company heads up.
 

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Discussion Starter #6
https://www.thetruthaboutcars.com/2012/10/supension-truth-4-once-upon-a-bump/

Decent Read. Remember at this point with stock Smart suspension and heavily Lubed Chassis, which translates into very minimum money spent, My Smart has been tamed a made very suitable upon the rugged Streets of New York City and the more rugged Streets of Detroit. on the smooth highways and smoother Watkins Glen Race Track my stock Smart is a perfect little beast. If all roads were smooth I would be done and would not change a thing just keep it lubed. But they are not so the High Speed Bump is what has to be sorted out. Money is an extreme object so the fix must be reasonable.
 

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Ohh! This looks like it's gonna be an interesting topic as it develops! I've only ever thought about the tuning aspect of the shock absorber itself, but never the bump stop. It does make sense though...it's almost as if you'd be supplementing the springs with more progression.
 

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Using the bumpstops as an active piece of the suspension is **not** the way to go. Having participated in high performance track driving for over 30 years, and having owned a Miata for five years where the bumpstop is unfortunately active a vast majority of the time with stock springs, I can tell you that the rapid ramp up in spring rate from being on the bumpstops creates handling issues as it vastly alters grip at one end or the other over a small amount of suspension travel, and there is no way you are going to get a shock that can handle both the low spring rate when not on the stop, along with the high rate when the stop is compressed.

Bumpstops should mainly be used to protect the shock and suspension components from over-excursion, and springs should be used in conjunction with shocks to limit travel for all but the most severe compressive events.

There's just no way around the fact that good suspension costs money, and in the case of the Miata a good suspension package is a couple thousand dollars. I mean, if it were as easy as just using bumpstops to tune a suspension well, all of the high end suspension manufacturers would be out of business. They're not, and there is a reason for that.
 

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And here I am with a custom lowering suspension trying to achieve a stiffer ride and lower ride height for better cornering and no bouncing during gear shifts or squatting with hard take offs lol
 

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And here I am with a custom lowering suspension trying to achieve a stiffer ride and lower ride height for better cornering and no bouncing during gear shifts or squatting with hard take offs lol
Then reading a lot of Miata information, especially regarding the first generation (NA chassis, 1990-1997), would be really instructional, since the Miata weighs roughly around the same, has roughly the same weight distribution, and comes from the factory with soft springs. Where the Miata has an advantage is that the center of gravity is much lower, it has a longer wheelbase and wider track, the alignment settings are adjustable front and rear, it has an independent rear suspension, and it has no stability control system to overcome. That and a huge high performance following and the parts availability that comes with it. But a lot of the information that applies to a Miata also applies to a smart. And for performance suspension, Fat Cat Motorsports and SuperMiata are two of the best when it comes to engineering solutions used in both spec Miata racing and in the Super Miata series.

After five years immersed in the Miata world, I think the common refrain from new owners is how surprised they are when they get their first ride in a properly suspended Miata using something like the Xida coilover kit from SuperMiata. They can't believe how a setup with springs three times the rate of the factory springs can ride so plush, yet provide such accurate chassis and wheel control. It works because the springs keep the suspension off the bumpstops, and the shocks are valved to handle the spring rate and provide maximum grip, not just make a ride that feels sporty but isn't optimal.
 

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For sure thank you. I have the car lowered quite a bit actually that my fenders in front and rear have been trimmed. To achieve a better base I have gone a bit wider from stock with wheels at 8 inches not including the low offset and 1.75 inch spacers and width of the adapters since im using 5x112 wheels. I’m just trying to go lower because of that center of gravity. My traction control is almost always off as I find it intrusive.
 

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It’s a shame major things to upgrade the car is so expensive from certain factories. I’ve just gone custom for a few things and it’s working out well. The front is going in again for its future suspension work to be dropped even lower as the 16 inch wheels with larger tires are still the equivalent to my last set up using 18 inch wheels. Once it goes in and they shave the fenders even more I’ll be fine. But I’ve considered some coilover kits but reviews tell me that they just don’t do it justice for what I like to do
 

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Discussion Starter #13
Using the bumpstops as an active piece of the suspension is **not** the way to go. Having participated in high performance track driving for over 30 years, and having owned a Miata for five years where the bumpstop is unfortunately active a vast majority of the time with stock springs,..............

Bumpstops should mainly be used to protect the shock and suspension components from over-excursion, and springs should be used in conjunction with shocks to limit travel for all but the most severe compressive events.

There's just no way around the fact that good suspension costs money, and in the case of the Miata a good suspension package is a couple thousand dollars. I mean, if it were as easy as just using bumpstops to tune a suspension well, all of the high end suspension manufacturers would be out of business. They're not, and there is a reason for that.
If you do not consider the stock Smart bumpstops an "active piece of the suspension" Then the bumpstock replacement I am looking for will also
not be an "active piece of the suspension" but a more effective replacement of the stock piece.

In that the replacement bumpstop would be doing exactly what it was designed and intended to do just better tuned for the terrain my Smart has to navigate on a daily basis.

I believe the Smart has a good suspension and on smooth roads its excellent. I believe for my driving, the bumpstops could feel better. What this "feel better" will cost remains to be seen.

There are many reasons that the Smart may have been Manufactured with the Suspension components its has. The aftermarket parts business also thrives. Automotive tuners will never threaten the "Off the rack" sales of the manufacturers but remember, Brabus is a tuner which improves on a manufactured product.

Last point... I ran my stock smart suspension on a smooth race track at 85 mph. I drive faster on interstate high ways at times, but make no mistake I am not in any way trying to develop a high performance race suspension. I just want to hit a bump and not have to curse for the next three minutes to calm down. I'm looking for a bumpstop to help with that.
 

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Drive a smart, hit a pothole and call the Dentist to have your fillings tightened.

smart has been supporting that Dentist since 2008, he’s happy and so am I - thanks Eibach!
 

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Discussion Starter #15
And here I am with a custom lowering suspension trying to achieve a stiffer ride and lower ride height for better cornering and no bouncing during gear shifts or squatting with hard take offs lol
I intend to stick with stock springs and ride height. The 17 inch 195/40 low profile Yokohama tires give some serious cornering grip. I feel once the chassis was properly lubed the suspension stopped being bouncy as the unsprung weight is allowed to move without making the springs react to everything. Also as I am not even close to hard core racing (I am just quicker and more maneuverable than most drivers sitting next to me at a stop light. And I do mean drivers not cars as no matter what you are sitting in you still gotta be able to drive it, so even a better car with a worst driver is still gonna see my tail lights) I feel no Squat, I do think a front motor mount in the spring time will be done. That's do to coming to a slow stop I feel something sometimes that may be motor mount related.
 

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Discussion Starter #16
Lets read into what the response is saying.

(Howdy,

I appreciate your inquiry. From my research, there aren't any rebuildable Bilstein HD or Sport available for your car. The B4 'OE' Bilsteins are twin tube and not serviceable. So unless you find someone to the contrary, the best you can do is bump stop tuning or see if a Bilstein from another vehicle might fit (which is doubtful since your Smart is a very unique vehicle).

For bump stop tuning, you can utilize the 47mm 'strut' style bump stop available at 5Xracing.com, or a 58mm 'red' bump stop for the rear shocks. That's my free advice. Wish I had better news but other than a custom-designed front strut or rear shock (which could run $2,000+) I don't see a way to improve the damping on your vehicle. Also, I only work on front AND rear dampers, never just one end of the car. It's called symmetry, and it matters.

Good luck,)


So this is the the "free" advise bumpstop recommendation for front.

https://5xracing.com/i-21093011-5x-racing-47mm-bump-stops.html?ref=category:1105233
 

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Lets read into what the response is saying.

(Howdy,

I appreciate your inquiry. From my research, there aren't any rebuildable Bilstein HD or Sport available for your car. The B4 'OE' Bilsteins are twin tube and not serviceable. So unless you find someone to the contrary, the best you can do is bump stop tuning or see if a Bilstein from another vehicle might fit (which is doubtful since your Smart is a very unique vehicle).

For bump stop tuning, you can utilize the 47mm 'strut' style bump stop available at 5Xracing.com, or a 58mm 'red' bump stop for the rear shocks. That's my free advice. Wish I had better news but other than a custom-designed front strut or rear shock (which could run $2,000+) I don't see a way to improve the damping on your vehicle. Also, I only work on front AND rear dampers, never just one end of the car. It's called symmetry, and it matters.

Good luck,)


So this is the the "free" advise bumpstop recommendation for front.

https://5xracing.com/i-21093011-5x-racing-47mm-bump-stops.html?ref=category:1105233
What they are recommending is that you should use the longer bumpstop in the rear. The reason for this is that any time the bumpstop comes into play, the spring rate increases. When that happens, grip is transferred **away** from that end of the car. Longer bumpstops are usually manufacturered to be either smaller in diameter/volume or of a lower durometer material, and typically designed to be compressed over a greater relative percentage of its overall length. This means it provides a more gradual ramp up in spring rate. The longer length means it is in contact sooner, so you don't all of a sudden get this unexpected increase in spring rate when the spring is more highly compressed, such as if you were cornering moderately or hard already. This longer bumpstop is designed to come into play much sooner so you don't get that surprise when you're already cornering hard.

The shorter front bumpstop is probably recommended because they're trying to keep you off the bumpstops as long as possible, and also because there are more situations the front bumpstops can be engaged, like under heavy braking. Also, if the bumpstops come into play and grip is transferred to the rear, you're more likely to survive loss of front grip rather than loss of rear grip.

Just a couple of other things. You said in another post that you said:

I feel once the chassis was properly lubed the suspension stopped being bouncy as the unsprung weight is allowed to move without making the springs react to everything.

The springs have to react to everything, because you do not have suspension movement without the springs either compressing or extending. The reason a car feels bouncy is either because something like the shocks are seized and the suspension is unable to move, thus transferring all pavement undulations through to the chassis, or that the shocks are unable to dampen the movement caused by pavement undulations. Either case is like those people who lower their cars without changing shocks - they bounce their way down the road. Shocks are usually the answer, but good shocks cost lots of money. There's really no way around that.

Lastly, a bumpstop should definitely not be in play when you hit a pothole. The wheel entering the pothole extends the suspension, so unless the car is sitting heavily on the bumpstops at rest, the bumpstop is not in play when the extended wheel hits the backside of the pothole and you get that severe jolt. That jolt is due to the shock not having good high speed compression ability. It's expensive to make a shock dampening slow motions well, yet also not be too rigid when asked to compress quickly.

If you're talking about driving along and hitting something like a speedbump, then yes, a good bumpstop will make a ton of difference. I ran the Fat Cat Motorsports bumpstops in my Miata and the transformation in behavior over the stock bumpstops was significant. Very plush when compressed, with a bit of hysteresis upon decompression so it didn't totally overwhelm the shock.
 

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It’s a shame major things to upgrade the car is so expensive from certain factories. I’ve just gone custom for a few things and it’s working out well. The front is going in again for its future suspension work to be dropped even lower as the 16 inch wheels with larger tires are still the equivalent to my last set up using 18 inch wheels. Once it goes in and they shave the fenders even more I’ll be fine. But I’ve considered some coilover kits but reviews tell me that they just don’t do it justice for what I like to do
I don't know how much suspension travel is built into a smart suspension. It feels like it isn't much - maybe 3-4 inches up front and maybe an inch or so more in the rear, at least on our electric drive. I don't know what your ultimate goals are but if you're looking to still have usable suspension travel and want to do something custom, possibly one of the cheaper way is to raise the perch that the suspension mounts on. This is likely more applicable to the front than the rear, but the front is where you need the travel more than the rear anyway. In the Miata world, these pieces are known as "extended tophats", but I've seem them used in other vehicles as well.
 

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Discussion Starter #19
In my case the Shocks were decent but all the bushings and chassis pivot points were rigid stiff and not pivoting at all. After the lube loosened everything up the ride became significantly better. I will continue learning, with this bump stop recommendation as the new starting point. Looking at the prices of the recommended Bumpstops, the price point is right on target. I would not change my struts and rear shocks yet but a friend is doing a strut and shock replacement and based on his review of ride difference I may go ahead with new ones with the recommended bumpstops. I also my entertain the next level of "non free" advice.. lol
 

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One thing that sticks out to me that is a poor design on these cars is the rear suspension linkage. If it wasn't for the flex in the rubber at the end of the linkages it would bind and not move at all. The linkage arms move through an arc but the axle moves straight up and down. Also since there are two arms with a center mount The distance between the end of the arms gets longer and shorter as the suspension moves up and down. The distance between the mount points on the axle stays the same. This causes resistance to the suspension cycling freely.

In this image I've drawn out the movement of the arm relative to the axle-


I'm not sure why they didn't just us a regular panhard arm design here. I've been thinking about it for awhile and haven't come up with any good reason. Here's an image of a typical panhard arm-
 
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