20 replies to this topic

[Spider]

I'm no expert in how the suspension loads up the lower bushes, but does the bush stay static to the arm and the pivot is on the metal sleeve?

 

With the lower arm bushes (that we seem to be discussing here), the steel sleeves are slightly longer then the Shank of the Pin, so when done up, the steel sleeves are pinched and shouldn't rotate on the Pin.

All the same, I do put a very light lick of grease on the Pins, not to allow the to rotate here, but stop them rusting.
 

[1984mini25]

I recently replaced my bottom arm buses with the poly ones the same as timmy850. I did also try the same on the tie bars, but the poly ones were noticeably thinner than the rubber ones so still allowed the ties bars to move about (wandering under braking). So did try half poly and half rubber (had to buy 2 full kits of each as I wanted black), before eventually swapping to rubber on both sides.

 

The problem I’ve had with the lower bushes though is I’ve found the lower arm nut (I used a new split washer and nuts both sides on the original lower pins) have somehow loosened themselves, which showed up a wearing under braking. I’ve since torqued them back up and marked them so I know if the loosen again. The only thing I can think of is with the bushes being thicker that even though the nut was torqued up, maybe the pin hadn’t been pulled all the way through.

[KTS]

 

 

 

 

 

 

out of interest, when does that article date from Spider ?

 

some of the polyurethane products on the market now use materials that have very different characteristics to what we've been used to - whether they better than the old types, or are better than the current rubber equivalents on the market remains to be seen

[Spider]

The problem I’ve had with the lower bushes though is I’ve found the lower arm nut (I used a new split washer and nuts both sides on the original lower pins) have somehow loosened themselves, which showed up a wearing under braking. I’ve since torqued them back up and marked them so I know if the loosen again. The only thing I can think of is with the bushes being thicker that even though the nut was torqued up, maybe the pin hadn’t been pulled all the way through.

 

Can I suggest here, firstly, use a clamp or something else to pull / push the Pin home, then for a Nut & Washer, I have gone to a 'tensile' Flat Washer and a Cone Lock type nut, though a decent Nyloc would likely be OK too. I don't use a Torque wrench here (and with any type of self locking nut is useless anyway), but do them up by feel. You're tightening down the Pin to it's Shoulder (or in reality, the tubes in the rubbers - if they have them) and so you'll feel when 'it's there', then just a small nip after that is all they need.

 

 

out of interest, when does that article date from Spider ?

 

some of the polyurethane products on the market now use materials that have very different characteristics to what we've been used to - whether they better than the old types, or are better than the current rubber equivalents on the market remains to be seen

 

Granted, that is a few years old now and yes it's possible that some of the various synthetic products out there may - or may not - behave closer to the rubber products for which they were designed for. But how do we know what's what in the zoo ?   For me, I've been down that road of finding what I was after, found good rubber products and happily sticking with those.

I get there's some people here how are looking for that change in some way, but I don't think jumping to Poly Bushes because we maybe unable to find quality rubber is necessarily the direction to head in. Definitely an option for sure, for without bushes, we'd all be parking up our Minis and Mokes !  If nothing else was available, perhaps then I'd move to them, but likely only while I would be having my own rubber bushes made.

I'll add that I did work (granted too, some time ago) with a local firm to help them develop their range of Poly Bushes for the Mini, they did end up with a range that they still sell to this day. I have to say, while I have free access to have them make what ever I wanted / needed (and they could do some pretty impressive things), I came away from it all fitting rubber in my own cars.
 

[nicklouse]

out of interest, when does that article date from Spider ?
 
some of the polyurethane products on the market now use materials that have very different characteristics to what we've been used to - whether they better than the old types, or are better than the current rubber equivalents on the market remains to be seen

Not sure that the date matters. In that I have not seen any poly parts that are bonded to the metal sleeve. They tend to have separate metal parts so there is no flexing of the polly just sliding. Last Polly bits I fitted were Metro suspension parts. No rubber parts out there.

[bluedragon]

The primary reason why polyurethane bushings predominate in the specialty aftermarket is much lower cost to set up manufacturing.

 

Note I'm not saying the materials are less expensive - probably on a per unit basis polyurethane mixes are considerably more expensive than rubber - but making rubber parts requires expensive, bulky machinery and a lot of heat for the vulcanization process.

 

Polyurethane mixes, by contrast, are largely room temperature compounds poured into simple molds, no pressure or heat. In many cases, depending on the size of the production run, they can even be hand poured. 

 

If you are manufacturing 100,000 bushings, it pays to invest the capital cost to set up the machines for rubber bushings then pay a small amount per bushing for the rubber material. If you're manufacturing 100 bushings, you'll never recoup the cost overhead of setting up the machinery, so better to use small scale production techniques and polyurethane is the most suitable material available. And you can produce on demand in a small shop.

 

But only in some cases is polyurethane a better choice. To be fair, some aftermarket manufacturers use shoddy quality rubber as has been documented here. One can't just use any old type of rubber compound, and some are either taking shortcuts with cheaper rubber or don't know the material spec and use the wrong type.

 

 

Dave