Powerflex Bushings

[Westfield 129]

I have the Powerflex bushings installed at the chassis end of the rear arms, and they are working well.
The axle end of the arms are using the standard bushings. So far, no clunking indicating that any of the bushings have ovaled out. They look good and are working as they should.

The problem is that the Powerflex bushings that I am have don't fit inside the rear axle mounts. The inner bush tube is too wide, and the bush is too wide to fit the thrust washers. Perhaps the bushings being supplied directly from Westfield will fit inside the rear axle brackets.

I will be inspecting the arms this weekend, again. The Powerflex bushigs seem to be doing well.

The rear suspension is hard on bushings in any case. It appears that when used on the chassis end of the rear suspension arms gives enough compliance to reduce the damage to the axle bushings.

The one thing that I would check is the width of the bushing tube Vs. the axle mount. The tube has to fit inside the rear axle bracket, and the front suspension brackets. If you can confirm the fit, get the Powerflex bushings.

If you can't... Then use then at the chassis ends of the rear control arms, and use the metalistics in the rear axle brackets.

[jonclancy]

Thanks very much, Jan.

I think I'll go with the standard bushes for the time being, but am seeing Splat in a couple of days for a pre LMC shakedown run. I think he's done his recently...

Cheers

Jon

[Splat]

I replaced the whole suite about a month before the poly-bushes appeared in the Westfield webshop. Typically, not a dickiebird was mentioned when I phoned to order 17 Metalastic items......

[erictharg]

Still sticking (no pun intended) with original rubber bushes!

[erictharg]

In fact I think the same people who dream up the marketing for polyurethane bushes do the same job for the waterless coolants on the market. Fixing a problem that doesn't exist. Just my opinion...

[Westfield 129]

The Powerflex bushings are a superior design, even if they were done in rubber. At least there is sufficient compliance so that the bushing wont tear itself apart at the first bump. However, the ones I have don't fit in all locations without modification.

I wonder if the Westfield supplied bushings actually fit the W11's rear axle brackets.

As for waterless coolant, there are advantages to a coolant that doesn't have to run underpressure, especially with high compression engines that run high temperatures.

Of course, if your engine works fine on conventional coolant under pressure and has no problems with corrosion, then there really is not much need for the waterless coolant. Especially when the price is considered.

[Splat]

Just to recap where we are:

Westfield offered a kit of 18 Powerflex bushes in its online shop, priced at about £180 for the set. They first appeared a couple of years ago, but disappeared shortly after.

At about the same time, Powerflex offered "Universal Kit Car/Westfield" bushes, part number PF99-116 at about £34 for a pair.

Jan has fitted the PF99-116 bushes to the chassis-end of his trailing arms. His early car doesn't have the double shear plates at the chassis. However, he has found that the PF99-116 bushes are too wide to fit between the welded plates on the axle.

I fitted a full suite of Metalastic bushes about a month before the Powerflex bushes appeared. But I've been toying with replacing them with polyurethane ever since. So I recently purchased a pair of new PF99-116 bushes on eBay for £25. At the same time I asked Westfield why they'd stopped offering them in their online shop. Had they experienced problems? No, they replied, they just couldn't make any profit from them. I wrote back, asking if they had any remaining stock that might cost me less than £34 per pair? I received no reply, but they are once again offering sets of 18 online for £145 plus P&P. So I bought a set and........

They are quite different to the PF99-116 units. Most importantly, I now know why Jan could only fit them to the chassis end of his trailing arms!

Photos below, but here are my observations and measurements:

Both types of Powerflex bushes (those from Powerflex and those from Westfield) consist of four parts; a stainless steel centre tube; a black PU sleeve with a knurled inner bore to slip over the aforementioned tube; and two plastic washers, one for either end of the bushing. The outside of the PU tube from the Powerflex pack is marked "POWERFLEX PF99-116". The outside of the PU tube supplied by Westfield is marked "WESTFIELD PFW92-1001S". However, the PFW92 (supplied loose, without packaging) is very clearly made by Powerflex (just from basic comparison with the Powerflex packaged PF99s).

For the measurements I shall use he following; M for Metalastic; P for PF99; W for PFW92:

The overall external diameter of the bush is; M 23.8mm; P 24.3mm; W 24.0mm. The Metalastic bush has a metal outer casing and is pressed into the suspension. The PU bushes have no hard outer case, hence the very slightly larger outside diameter.

The bore of the central steel tube of each bush is; M 11.1mm; P 12.2mm; W 11.0mm.

Most crucially, the overall length of the central steel tube is; M 38.1mm, P 38.9mm, W 38.0mm.

Which leads to some significant conclusions! Firstly, note the inner bore. 11mm is just right for the 7/16" bolts of an eleven. 12mm is for a modern M12 bolt. Secondly, the PF99 unit is 1mm longer than the Metalastic bush. The PFW92 is exactly the right length. So the "Universal Kit Car/Westfield" PF99-116 that is widely available, seems to be specified for a modern, metric chassis. The PFW92-1001S, not recognised on the Powerflex website, and only available from Westfield, is dimensionally identical to the original Metalastic bush.

There is only one fly in the ointment. Compliance! Compare the thickness of the PU sleeve of the two Powerflex offerings. The PF99's have 4.1mm of PU. The PFW92's are just 2.5mm thick! The photos speak for themselves.

In the following photographs the lineup remains constant: left to right; PFW92-1001S (W); PF99-116 (P); Metalastic (M).

[Westfield 129]

Nice to see all the parts together.

Here in the US, the price of the bushings is about $200 for the rear suspension alone... Around $400 a set for the entire car. Expensive... Especially when they dont really fit everywhere on every W11.

The PF 99-116 inner sleeves that I have are bored for a 7/16" bolt. This was the first thing I checked when they arrived, as I was advised after they shipped that theye were 12mm bolts. Fortunately, that was not the case, and the factory documentation on the parts is in error.

The fit is fine correct for the 716" (AN -7) bolts. The bore on the part that Powerflex USA sent me is identical to the metalistic's inner bore.

Also, I have built a few of the late chassis, and those cars still feature all fractional 7/16" suspension attachment bolts and the same old metalistic bushings. This is one of the reasons that I build the cars with all fractional chassis fasteners, eliminating the need to carry two sets of tools.

I did notice that the Westfield supplied bushings did have a very thick central tube, with little material for compliance. This would be ideal for the front end, but problematic for the rear with the equal length 4 link, especially in roll.

So,.. I am still using a set of the Powerflex "kit car" part numbers at the front attach point of the 4 link. This will work on both early and late chassis (the shear plates can be spread slightly to accommodate the slightly wider Powerflex parts.

So far, these compliance bushings have extended the life of the axle end metalistic bushings. It is certainly possible to get the PF 116 bushings to fit, shortening the tube and the bushing itself, along with a slight milling of bushing mount in the suspension arm to accommodate the thrust washers, if you choose to fit them.

Eventually, I will get to doing this, maybe... I may just shorten the tubes and install the bushigns in the axle mounts without the thrust washers. I have an extra set...

[jonclancy]

Has anyone contacted Powerflex to ask about a run of properly sized bushes?

If WF were able to specify a custom item, then maybe they might come in on a MK2 version that fits, improves life and handling, and is a fit and forget (for a while) for new builders and current owners?

I need to do my bushes. Car has 4500 miles on it now and still on the original bushes! Probably just go with the metalastics torqued lightly per Jan's recommendations...

[Splat]

The Westfield-supplied Powerflex bushes seem spot-on. Despite Jan's assertions, the 11mm bore is perfect for the 7/16" bolts used in the Eleven. The PF99 universal items, at 12mm bore, are definitely designed for the more modern Westfield chassis (SE, etc.) which uses metric bolts. Hence they're also a millimetre too long and won't fit between the lugs of the Eleven.

Westfield obviously gave a Metalastic bush to Powerflex and said, "Replicate this." Unfortunately, they took this literally and the PU compliant part is the same thickness as the rubber in the Metalastic bush, which is only as thin as it is because of the physical constraint of having to be sandwiched between the two metal tubes of the bush. Without this constraint, Westfield would surely have specified more compliance in the original Metalastic part.

So there's no more reason for the PFW92 part to bind than there is for the Metalastic bush to do the same. It would just have been nice to have the correct sizing of the PFW92 part combined with the greater thickness of PU given by the PF99 part, giving a more compliant, less noisy ride.

As the PU is not bonded to either the arm or the core, it shouldn't rip, unlike the bonded-in rubber of the Metalastic unit. The PU is lubricated within the assembly with PTFE-loaded silicone grease. Compliance should be the same and longevity hugely improved. Anyway, we'll have a better idea in the next couple of weeks when I've got around to replacing the five in my rear suspension......