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I've done a bit of research on Urethane bushings it looks like they can have issues with pushing out the grease and binding up the joint. They can end up having more friction than stock rubber bushings unless they are constantly greased. Some stuff I've read say they need to be regreased every second event to maintain good movement which is crazy.

One option is delrin, but there are issues with the lower arm adjustments making them suitable only for a few joints. I was thinking of using the ISC offset delrin bushings for the upper arms and Urethane for the lower, but then I don't want to have to re-grease the Urethane constantly either.

The Mazdaspeed competition rubber bushes are another option, with a mix of delrin and rubber. It wouldn't be very cheap though.

What does everyone use?

I've got superpro polyurethane with offset bushes on the lower arms.

Pros:
- they're just quiet and comfortable enough for daily use
- they're very precise for track work
- mine have lasted very well (8 years)
Cons:
- you need to dismantle all the suspension and regrease them from the inside every few years, otherwise they bind and that does imapct suspension response. Grease nipples don't really work because you can rarely get the grease down to the sliding surfaces which are buried deep inside.
- the offset bushes can spin during wheel alignment and inexperienced operators really struggle to cope with that
- the offset bushes can occasionally slip in use and buggar up your alignment

If I had my time over I'd go with Mazdaspeeds and modify the control arms to get the camber I need.

Great feedback Manga_blue... pretty much is the same as what I've read, although the refresh frequency was higher for some track /autocross guys that were targeting very free arm movement. I think their issue was after a few events, the urethane ended up with a lot of resistance, in some cases more than the rubber was giving.

I'm fairly happy with my 26 year old rubber bushings but at some point I'm going to have to update them. I'm toying with the idea of going down an experimental path and trying out some exotic materials. Someone on MT.net used oil impregnated bronze bushings over machined inner sleeves to create a bearing for the Urethane to spin on. So instead of the Urethane sliding over the inner sleeve with grease, it basically sits dry on the outer bushing which in turn spins over the inner sleeve. I've found some low friction polymer bushings that could be used in the same way and would give very free motion and a low maintenance joint.

The question is, how much is a friction free joint worth to performance of a suspension arm? Is it really worth all the effort, or just stick with my old rubber ones. I haven't noticed indirectness in my car, but then I haven't dríven on upgraded bushings... I suspect the difference would be very noticeable.

I've now got Maruha http://www.maruhamotors.co.jp/miata/parts/pirobush.html

So far loving them, can give a more detail review after a few more events.

Energy bushings here. I have also used them on a roadie. They are awesome but suffer from the same issues as Phil identifies above.

I will say that as two piece bushings, they are a bit easier to install and remove for regreasing than the Superpros.

I have also had recurring issues with them binding in the front UCAs. These bushes need to be regreased more often still.

My long term plan is to go with heim bearings in all the control arms. It's a lot of work though to make them work without building custom control arms.

I am not a particular fan of polyurethane (PU) bushes. My MX5 is the only car I have owned that has none in it!

I have had PU bushes in all my Datsuns (culminating in every bush being PU except one pair in my last Stanza) and my Celica, where I tried a number of different bush replacements and selectively left only one pair of PUs in place.

I have found that for badly worn bushes new PU is better than old rubber, but I think new rubber is generally the best solution. Manga Blue and Zossy1 outlined some issues above, but I always ask myself "why doesn't a single vehicle manufacturer use PU bushes in any car, in any price segment?".

PU bushes act as a sliding bearing (if correctly lubed), not as a flexible bush the way rubber does. And as materials go, PU is not a particularly good one for bearing surfaces, as it is soft, grippy, and can gall if not lubed. The opposite of what one normally wants in a bearing. But the advantage of aftermarket (PU) bushes is that you can get different stiffnesses, reduce compliance at the joint, maintain suspension geometry under load and have a more responsive, better handling car. But by changing the stiffness it is also possible to upset the suspension geometry, and make the handling worse, which is what I am afraid I might do if I started adding PU bushes to my MX5. Like many aspects of car modification, it is a compromise.

And I should add that for some cars PU bushes can cause binding in the suspension, but this isn't an issue for double wishbone set ups like the MX5 has.

I have the ISC delrin offset bushes in my front upper arms and would recommended them if you don't want to modify arms. I can achieve -3.5 degrees of camber at the front, don't remember by hub to guard height is though.
I locked them in with metric grub screws as the grease nipples that were supposed to come with them were not in the package.
They were also super easy to install. They literally just went straight in the joints by hand, no press was required.
They have not moved at all after more than a year of use. I have completely knocked out my alignment in off-track excursions but these things don't budge with the grub screws locking them in, so its just a normal lower arm alignment each time.

However a negative I found was after about 3 weeks they started to squeak really bad. ISC told me that they would not do this.
The solution was just to loosen the long bolt and put some grease between the bushing and big washers as that was the culprit. I am actually just using Benidx Synthetic brake grease(the blue one) as it is reasonably thick. Oh and re-tighten the bolt.
Squeaking does occur again if I drive through a monsoon, which has only been twice for my usage.
I have more NVH issues than standard but I suspect that has more to do with coil overs I put in at the same time.

The rest of the bushes are standard rubber ones. What ever SE's came with.
I also avoided Poly bushes because of the need to re-grease and rotating issues for offset bushes.

StillIC wrote:And I should add that for some cars PU bushes can cause binding in the suspension, but this isn't an issue for double wishbone set ups like the MX5 has.

Explain, then, how after I grease my bushes and install them, it takes all my strength to slowly manipulate my control arms up or down? And how, after some time, I need a floor jack or a crowbar to do the same movement?

Binding IS an issue, and it artificially adds bump and rebound resistance to all four corners of the car. This resistance itself is not the problem as you can tune for it, but as the grease dissipates and the binding worsens, it makes setup a moving target.

EDIT: what can happen if bushes seize completely:

zossy1 wrote:Explain, then, how after I grease my bushes and install them, it takes all my strength to slowly manipulate my control arms up or down? And how, after some time, I need a floor jack or a crowbar to do the same movement?

Binding IS an issue, and it artificially adds bump and rebound resistance to all four corners of the car. This resistance itself is not the problem as you can tune for it, but as the grease dissipates and the binding worsens, it makes setup a moving target.

That’s an interesting point, in your experience how long would you estimate it would take to get to the point that the additional bump and rebound resistance would be high enough to significantly mess with the suspension setup?

Also if someone isn’t going to regrease their bushings more than say once every 10 track days would you say sticking with rubber bushings might be a good call?

That's what this discussion is all about. I know that it only takes a couple of track days for my Energy front UCA bushings to become very, very stiff, and this is a dedicated track car. The others take longer. I would guess that it would depend on your brand of bushings, type and effectiveness of grease used, and usage, including wet/dry, etc - it would all affect the result.

I have the ISC offset delrin bushings but I think the superpro kit might be a better complete solution.

zossy1 wrote:

StillIC wrote:And I should add that for some cars PU bushes can cause binding in the suspension, but this isn't an issue for double wishbone set ups like the MX5 has.

Explain, then, how after I grease my bushes and install them, it takes all my strength to slowly manipulate my control arms up or down? And how, after some time, I need a floor jack or a crowbar to do the same movement?

Please let me have another go at explaining what I meant when I said "binding in the suspension". I did not mean "binding at the joint" which is what you mean zossy1, and as you say this *is* an issue with any PU bush, which is why I don't like them. Nice picture, BTW.

Some suspension systems rely on the flexibility of the rubber suspension bushes to allow the wheels to travel up and down (bump and droop) separately. An example was the 4 link live axle on my Datsun Stanza. If I had replaced all 8 bushes with say, ball joints, then the only bump/rebound allowed by the geometry is when the entire axle moves as one and both wheel travel up and down in unison. To move one wheel in bump and not the other, with all ball joints installed, requires the axle to twist, or suspension members or chassis to flex, due to the suspension geometry. In normal operation with rubber bushes, the compliance of the bushes themselves allow the assymetric bump/droop movement of the suspension. Does that make sense?

If all the bushes of the MX5 suspension were replaced with ball joints, there would be no suspension binding (or joint binding) and it would all work just fine.

Sorry for the confusion.

No worries - I see the distinction, thanks for clearing that up.

I must be doing something wrong!!!!

2009 I fitted Energy bushes and have regreased twice. ( car has done 20,000ks, mostly Sunday drives @ the Lakeside)
The last time was 3 years ago after we had stripped out all the arms to modify the Koni shocks.
When I reinstalled all the arms I used a synthetic Mobil EP grease SHC220 and since then haven't had any issues. I know that I could go straight out and
jack up the car, remove the shock bolts and pull up any corner up and then let it fall on its own weight without any binding.

The Mobil grease I used is what we had to use in my Merc Buses as we were doing front wheel bearing every 160k, the grease is friggen expensive
but our wheel bearings are about $800 a side so in the long term its quite cheap ( for me)

This sh*t is slippppppppery, so maybe its more to do with what you use to lube them with than what brand of
bush you use.

• Mobilith SHC™ 220 is a multi-purpose, NLGI 2 extreme pressure grease recommended for heavy-duty automotive and industrial applications. It uses an ISO VG 220 synthetic base fluid. Mobilith SHC 220 has a recommended operating temperature range of -40º C* to 150º C.

Hope that helps
T

As StillIC says, you need some give in at least some of the joints for the suspension to twist. This movement is small but is the reason you can't run solid Delrin bushes in all arms.

The solution I'm making is going to work very well, which is a rotation bearing inside the urethane bushing. Check out my thread here: http://mx5cartalk.com/forum/viewtopic.php?f=57&t=68537&start=82

So the urethane doesn't have to slide over anything and basically needs no grease, it just has to flex slightly to allow for the suspension twist. The movement of the arm up and down is handled by the rotation bearing running on the sleeve. So far I've only made enough for one corner of my car, but I'm planning on getting the other side finished before the next event. Without the shock attached there is basically zero friction at each joint, just the weight of the arms and the hubs to move.

Subject to how long it lasts, I think it's the optimal solution other than sphericals.