I have found drilling poly from an established hole is the only way I can machine it. Whenever I try to turn it or face it, it just deflects. When you force it enough to finally bite, the surface finish is absolutely horrible. And even worse, its so unpredictable, i could hardly hold a +/- 0.020" tolerance.

The people that do machine it have special setups with spindle speeds beyond my capabilities, and very sharp honed HSS cutting tools. Aidan has also mentioned freezing it before machining, which should help.

Thank you all for explaining. I didn't realize polyurethane was difficult to machine, but apparently it is more of a grab-and-tear than a machining process. It appears freezing, liquid nitrogen, dry ice, and other methods make this a bit easier, but this is all complexity that also contributes to cost.

I also appreciate the explanation that the new sleeves are a known quantity/material, whereas the Energy Suspension/Prothane sleeves are unknown as far as material. Going to a slightly smaller sleeve isn't a loss of strength as well as better tolerances to put everything together.

And yes, one of my base assumptions was doing this all at once, and not a retrofit situation.

I await the off-the-shelf bronze bearing kit with new sleeves.

Wait no longer.

Ooo, can I retrofit the extended fittings, as long as I get the same size threads?
It would make the annual greasing easier.

Yep, shouldn't be a problem. I need the longer ones too, been using a needle to get mine.

Absolutely.

1 4 28 x 1" Taper Straight Grease Zerk Nipple Fitting 10 Pcs | eBay

I endorse this thread. I also suggest you switch to making your bushings from 1144 stress proof if you can. Its monumentally easier to machine than 4130 and a bit stronger, thats what we used to make mine.

That is a very attractive option. Having reviewed the data sheets, the only downside to 1144 is its slightly softer hardness rating compared to 4130. But its really almost negligible, Brinell 200 vs 260. I wish I'd have known this earlier, 4130 is a bitch to drill, that's where most of the labor goes.

Its half the price of 4130 and has a machinability of 83%! That better than 1018, and definitely better than 4130 at 72%. So kit cost will go down! Tensile is rated at 100k yield! holy fuk. That compares to 60-70k for low carbon and moly.

Unless someone can come up with a convincing reason not to, I think I'm going to switch over to 1144SP.

Im going to redo some of the pricing based on this. Those of you who have already contacted me, I will try to have a new quote for you soon.

Further research- 1144 doesn't come in tubing. 4130 tubing is very common. The hardest part of drilling these out is making the pilot hole in a solid piece of bar stock. So I use tubing whenever I can to save on labor. It doesn't make sense to save $10/ft. on the material if I have to do a "full drill" on it and raise labor $20/ft for example. There are a few locations, like the FUCA that uses a 10mm bolt, that I still have to use solid for since tubing doesn't come in standard size in certain ODs with a small enough ID for a 10mm bolt.

So I need to play with some numbers and Ill probably end up using a combo of 4130 and 1144 where it make the most sense.

Stupid questions/observations:

Wouldn't freezing poly affect the material composition? Something tells me this stuff is still like rubber or any other plastic that really doesn't like temperature changes.

On the long bushings that go from one side of the bore to the other, how does the grease make it to the sleeve? And even on the split bushings, will the grease push through the joint to make it to the sleeve? Or did I miss the part where you guys machined a hole for this?

And not that it matters to most of you guys but machining the bushing inner diameter to accept a larger sleeve is not technically to the rules for anyone in Street Prepared autocross classes. While you can change the bushing material to any non-metal material, you cannot increase the amount of metal in the bushing. Its a minimal amount of people that would be impacted by this but the fact that the bronze bushing retrofit kit doesn't affect the bushing size at least meets the rules criteria for SP autox'ers.

Freezing: Poly bushings have been frozen millions of times all over the world. Because cars are in freezing temperatures sometimes.

Grease: it pushes through the crack.

Parking lot racing: sounds like these aren't a viable option. For some classes

NASA: if you race NASA you don't want the rear spherical. It's worth a ton of points. I ordered some ruca outer polys specifically for NASA racers.

Regarding the freezing that is kinda my point: I live in a tempered climate and my poly bushings have not cracked or disintegrated in over three years of service. I read lots of claims of the opposite and mainly from people that live in cold weather.

Ok, so grease pushes through the crack. What about the bushings that are solid all the way through the control arm bore? Like in the FUCA?

And you misunderstood about the rules for auto-x SP. These bushings are good to go for SP. They do not increase the amount of metal in the bushing. Only on the FUCA which you can just put the Delrin into. Your solution/kit is absolutely perfect for cars like mine in CSP.

Ok good to know about the freezing I hadn't heard that.

I'll let Sean take the grease question.

Maybe we will offer a SP package. With poly everywhere and a delrin FUCA.

Yeah, I'm not saying that freezing does affect the life of a poly bushing. I'm a high school drop out with a GED and not an engineer. I'm just putting two and two together and it somehow is adding up. Total conjecture on my part.

I'll be contacting you guys shortly about what to get for my car. It seems that I would want Delrin everywhere other than bind positions. So as Sean mentioned, the poly/bronze on the RUCA-O and RLCA either front or rear? Then the FLCA front or rear?

We run the poly in the lower control arm rear position. And poly can be included in your kit.

Looking forward to hearing from you.

At a certain point, like those experiments with liquid nitrogen, yes they can crack. No idea at what temp that happens, but I would just be sticking them in your ordinary household freezer, and cant see it being too much problem.

I explained it in the grease fitting section of the OP, but its easy to miss, so I quoted it for you.

For the the split bushings, grease will go between the "crack"

I think you already clarified, but the stock miata sleeve is ~0.905", we use 7/8" (0.875"), so its perfect for class rules for every location except the RLCA-O which is ~0.826", or 21mm, stock. What about the FUCA?


as mentioned, rear/rear

Also, 1144 savings turns out to be negligible since I cant get it in tubing. So im going to use it for the parts of the kit that im already using solid on, and depending on how it machines, I might be able to knock a few $$ off, but it wont be much. I plan to get a pricing structure done up soon.

McMaster has a ton of long and/or angled fittings for cheap.

My control arms, after I get my delrin and bronze kit:

https://www.miataturbo.net/attachmen...ine=1454779071

:bowrofl:

We are also putting a full spherical kit in the works, but that is going to be ridiculously expensive.

If you have :burncash: hit us up