Spherical bearings
 

Some coilover packages include upper mounts which use a spherical bearing to receive the shock rod, as opposed to a rubber bushing. Manufacturers commonly refer to these as "pillowball" mounts, and they can also be purchased as standalone items from certain vendors such as FM.

Various claims are made that these devices improve the response of the shock absorber, contribute to NVH, etc.

Discuss.

Do you want squishy rubber or not? On a street car, squishy rubber is a comfortable thing.

Yes.

Is it significant in a miata? Meh.

Having run fancy coilovers with rubber and pillow balls, I didn't really notice a significant degradation in the ride quality.

BUT
if you do swap out NB2 shocks, make sure you get the little clear plastic gaskets that go between the body and shock top to prevent the squeaks.

Yes. As the lower control arm cycles, the angle between the shock and the upper shock mount must change slightly. A spherical bearing allows this angle to change without applying any substantial side load to the shock shaft. A rubber bushing will apply a side load which increases stiction in the shock and thus reduces response.

The same metal bearing that allows ideal articulation of the shock will transmit more force to the chassis, which will increase NVH

Splitting hairs with you as I know you know; just want to let others know that may not know. The bearing itself means nothing if you don't isolate the spring from the pillow ball with a separate upper spring cup.



Bose noise cancelling earbuds. Its amazing what you don't feel when you don't hear it.:)

I love the word stiction.

I only have one direct comparison, meaning same car, same basic set-up, only the mount style was changed.

Had a guy running Ohlins on his NC for trackdays. Eventually his spherical bearings started making NVH noise over bumps that was pretty noticeable. Sounded like the struts were loose in their top mounts going over bumps. The bearings had some play in their races.

Ohlins sent us new spherical bearings, but they were even louder. Sent them back, tried the next set they sent us. Still loud. Ohlins said that's the best it was going to get, the bearings were within spec. It was weird, because the first set was quiet for a good while.

The owner still drove the car on the road, and didn't like the extra noise, so we adapted his original squishy rubber mounts.

Driving it around the back roads, I could tell no difference. Owner says he can feel no difference on track. I'm sure the difference is small, but demonstrable.

Race car = pillowball

Street car = personal preference of NVH vs. performance.

My car is still on nb mounts. Billet uppers is another one of those things where the theory guy in my head is yelling about it being better and the right way to go, but the guy who actually makes shit and does things is pretty sure that I have an enormous list of other stuff to spend that money and/or time on to make the car faster. If I was going to buy a new shock setup now would I drop he extra money on it? Probably. But I'm not going to go out of my way to put a set on my current xidas.

Sharky, you need to have your friend measure those sphericals and then buy the same size from NHBB. NHBB sells the only sphericals with actual thrust load testing done on them, aurora only gives you a rule of thumb based on the radial load rating, NHBB gives you an axial load rating on some of them.

I'd like to see numbers as to how much of an arc the shock travels in compression.

When I first got me NA it was running stock squishy upper mounts with lowering springs and stock bilsteins. I was shooting for a more race prep type setup and went with ebay coilover sleeves on the bilsteins with some 2.5" QA1 springs (450 front 350 rear). The stock mounts don't work well with this setup so I designed a top hat that would accept a 2.5" spring and a spherical on top of the damper. Below are some pictures. The tabs have two holes for ride height adjustment (untested bc lazy in winter) but this keeps the piston in the center of the damper for full range of travel. As far as NVH goes this setup is far more rigid than before and "response" is improved, but I actually notice a lot less noise. This could be from my lack of bottoming out over everything, but after this setup I will never go back to what I was running before. For those wondering I have put ~10,000 miles on these with no issues.
https://www.miataturbo.net/attachmen...ine=1438544388


https://www.miataturbo.net/attachmen...ine=1438544388


https://www.miataturbo.net/attachmen...ine=1438544388

Curious. Mustangs use caster/camber plates that have the top of the strut through the spherical bearing.

Example pic below, no strut installed, to show bearing clearly.

https://www.miataturbo.net/attachmen...ine=1438628093

FAWK.

It's not a hard (re)install. jack car, remove 2 nuts from each corner, let it hang loose, wipe off the top of the mount and underside of the body/frame, and jam your hand up in there with the gasket.

I don't know if i have them anymore. I'll have to check.

We had those mounts on our mustang. They were nice. Not sure but the steering felt less jerky after. Was under the idea that with the bearing we were not turning the shaft in the shock anymore.

I have been running without two of them for a year and a half with NA top hats, and now a few weeks with none and NB top hats. No noise from them.

Why would the shaft rotate inside the shock when the steering is turned? Do Mustangs have MacPherson strut front suspension?

Yup.

Interesting...

Given how enormous and expensive the Mustang has gotten over the years, I find it difficult to imagine that packaging constraints or cost dictated the change to strut suspension as opposed to the traditional double A-arm.

The Mustang chassis was based on the Ford Fairmont platform, introduced in 1978. The only SLA suspension ever available was expensive aftermarket kits.

Thanks for the info. Not sure what Ohlins uses standard, but I'm sure there's other options. Good to know for future reference, as I believe the car is sold. He's tracking an FRS now.

IIRC, that chassis has struts because it was intended to support FWD applications as well.

--Ian

as mentioned, its a "whore" platform, designed for many different layouts, etc.

https://en.wikipedia.org/wiki/Ford_Fox_platform#SN-95

As someone with a background in design and manufacturing, I still fail to comprehend the desire to share a common "platform" across vehicles with differing wheelbases and drivetrain configurations.

Different presses, different jigs, different molds... Where exactly is the commonality?

Some of the engineering caries over when platform sharing, which allows them to spend more time/money designing that platform well vs multiple platforms, ultimately saving them money.

I will say that the upper hat and spherical bearing made a very noticeable difference. We did only that mod at that time and without proper alignment (aka put it in a drove around) it made the steering far more precise. The 2000 Mustangs are built more like trucks. Like trucks with fail struts and fail 4 link rear.

It sounds good in theory, but I've participated in that mass hallucination on several projects. You wind up spending way more time in design revision and document control than if you'd just started with a clean sheet and a parts bin.

That's one thing Mazda did right on the NA. Threw it together out of discarded bits of other cars, but without deluding themselves into thinking that it'd be a good idea to start the chassis design by laying a sheet of translucency over the old F or H blueprints.

Perhaps. I'm a software guy, and if we threw out the source code and started over every time we built a new router, we wouldn't get very far. :)

The NA may be a clean-sheet, but the NB is barely changed at all from the NA, and the NC shared a lot of parts with the Rx-8. Dunno about the ND.

I suspect that platform sharing makes more sense for more "normal" cars, where you just want to crank about a few different sedans of different sizes and luxury levels in order to appeal to more buyers. Trying to apply it to sports cars leads to things like the 350Z weighing 400 pounds more than it really ought to have.

--Ian

I'm more so surprised that each manufacturer uses a different frame for each model. By now i would have expected 2-3 different types of sub frames and thats it. The only other difference being in the body mounts.

This. Some things are not worth starting over on. You said it better than I could have.

I agree with leafy, they're pretty far down on my list of things that will make a difference on the miata setup. Honestly the better value would be in the rod eye solution up thread. At least that gets you access to lots of good motorsports shocks.

The more parts that interchange between models, the smaller the inventory system has to be for both production and maintenance.

Shocks and struts function differently in terms of arc travel(AFAIK). What gains you'd find with a strut probably don't translate to a shock.

Bearings, effectively, don't have hysteresis that rubber bushings have. This eliminates a lot of undamped movement in the coilover.

Beyond that undamped movement, the rubber bushings bind and have their own spring rate. As the damper is compressed, the lower half travels through a shallow arc while the top is constrained. This swinging back and forth acts on the coil spring, leveraged against the shock seals. This lateral and twisting force adds a lot of seal drag and not in a linear curve.

Most "pillow ball" mounts just replace the rubber bushing with a bearing. Unfortunately, the greatest tangential loads imparted on the shock shaft are from the spring acting on the body mount off axis. That generate a lateral thrust load. Some higher end coilovers will have a separate, semi isolated "coaxial" upper perch just for the spring that is allowed to swing independent of the body mount. This coaxial perch mount is the inspiration for all the JDM style coilovers with "pillow ball" mounts but without the actual coaxial perch function. The coaxial perches takes up a few mm of space that has to be allowed for in the layout of the coilover to insure the correct bump/droop travel and stroke.

In a nutshell, it's friction we're reducing or eliminating by replacing bushings with bearings.

Teaser of the new SuperMiata coaxial billet mounts we just put into production. Coming around December (not taking pre-orders). These will be available as an option for Gen 1/2 Xidas for $299 for the set of four. We're adding options for 70mm (Tein) and 2.5" spring perches along with a simple adapter kit so any damper with a NB sized 12mm pin can run them. So Bilsteins, Koni's or whatever else you have.

We also reshaped them a bit for tire clearance. These are much narrower than an NB mount but still fully supported on the body.


http://949racing.com/supermiata/Supe...ock_mount.jpg?

hnnnnnnnnnnnnnnnngggggggggggggggggggggggggggggggg

<p>Thank you for the reasonable pricing (in my eyes) emilio. You're product will be selling for half as much as some others on the market and looks tits.</p>

I swear, I wasn't deliberately shilling for Emilio.



(where's my check?)

Damn that's cheap. Awesome.

Are these taller than stock NB?

Emilio, do you have any data on change in shock performance? I do believe that they work, I'm just not sure how much of an effect they'll have. They're pretty low on my list (pretty much after replacing every other bushing with sphericals) if I decide to keep my Miata, but I'm open to reconsidering.

How do they take up axial loads. Most spherical bearings either aren't rated for them, or aren't rated for very much. I trust with your name on them they work, I'm just curious.

Also, I think that the JDM style pillow ball mounts reflect the fact that a lot of these go on McPherson struts, where they do actually do something.

Joe's OP was in reference to spherical bearing mounts, not so much coaxial perches. The two are related though so I chimed in.

I don't have any handy infographics and can't articulate all the math. I've seen spring rate plots taken by indycar teams back in the 80's with and without coaxial perches. Can't find them on my machine. The difference in linearity is surprising. Any coil spring when compressed in a straight line has a small amount of nonlinearity. Coil springs also twist a bit, thus the reason for our Torrington bearings. If one or both perches are allowed to tilt off axis a smidge, rate linearity is improved a bit. Further when a coil spring is compressed between two planes not parallel with each other (all non-coaxial perch "pillow ball" miata mounts), rate deviations are increased as well as thrust loads being imparted on the shock shaft. All these ancillary forces adversely affect the suspension action. Imagine the shock compression smoothly at say 400in/lb then it hits a spike where extraneous loads cause the rate to jump to say 440 in/lbs, then 3/4" further into travel ease off to 380 in/lbs. Even our Club Sport setup is affected by this, despite having very low friction dampers. Our bushing, collar and hat assembly are engineered to allow as much tilt as possible with a minimum of vertical compliance to reduce side loads on the shock shaft. IOW, we try to make our bushing setup act like a bearing. It's as good as you'll get with NB mounts but the billet coaxials go the next two steps beyond in reducing or eliminating unwanted forces acting on the shock.

Google search comes up with some good results

http://webcache.googleusercontent.co...&ct=clnk&gl=us

We worked to bring the price down on the billet coaxial perches on and off for the last 4 years. Finally got everything nailed down. Very happy with the result. The idea is for everybody to be able to afford them for their project Miata.

I don't have numbers for you. Less friction and binding is better. Can I feel the difference? Yes, but I'm the guy that designed the shocks. Will you be able to? Maybe.

<p></p><p>And thats why we love you Emilio&nbsp;<img alt="love" src="https://www.miataturbo.net/images/smilies/love.gif" style="height:32px; width:40px" title="love" /></p>