Has anybody gone to any polyurethane bushings on the MINI? Any ideas on which ones would make the most difference in regards to handling? Any input would be great.

Thanks.

 

I really haven't felt the need to stiffen up my bushings yet with my lowering
springs and swaybar, wheel/tire upgrade...

 

so far, I've only put them on the rear anti-roll bar.
if figure it's needed more there than the front bar, and
the other locations are harder to install and would introduce
more harshness.

 

Yeah, I've got them on the rear swaybar as well since they came with the aftermarket bar I got. I'm moving to an aftermarket spring/shock setup in the next couple weeks and already have 11lb 15" wheels on 205/50 Falken Azenis tires.

I'm really not worried about the rough ride, I don't drive the car daily and I'm still a young buck, I can take a few bumps here and there. I'm just thinking that while I'm doing the spring/shock and camber plate install I may as well toss in a few poly bushings here and there since they're relatively cheap.

I've got a friend who works at a Powerflex dealer so I'll get together with him and see what we can toss on there when the car is apart. I'll report back in a few weeks.

 

I'll give you my first hand experience with poly as applied to other cars - a 99 civic Si for example. I'll try to keep this as short as possible, but this potentially, a huge subject.

Poly can dramatically alter the behavior of a car, for better, and, for worse. Poly, and Delrin, do not flex (ever) like stock soft rubber bushings. This in theory allows the suspension to follow intended arcs and lines. However, some suspension systems are designed specifically to flex at the bushings; some rubber bushing applications allow for more positive toe-in in the rear for example, to be gained as the suspension moves thru its arc. This in particular has a stabilizing effect, a good thing. In this application, poly is the wrong material as the pre-designed stabilizing effect is removed. A hard rubber bushing would be a better choice here because the suspension would still act as designed, but only begin to deform under much higher loads. Poly and or delrin are perfectly suited to sway bar applications.

Poly can also bind. As stated above, the geometry of some control arms, for example, cause loads to act on bushings in pre-determined directions. These loads DO affect poly; the poly will begin to literally wear away in response to these loads. As wear patterns develop, components either begin to bind, or under extreme conditions, the poly wears away and the suspension becomes loose and or sloppy.

Poly is also noisy; bushings require frequent lubrication to keep from sqeeking, and, working properly.

Poly is extremely unforgiving on the street. Every leaf run over will find its way to your butt and finger tips. This means that expansion joints will be felt in most un-sophisticated ways. The structural integrety of the car will not like poly very long if driven on the street. The track is a different story for sure, but then, refer to the above suspension geometry cautions.

Hard rubber bushings are much better, and much more comfortable. Hard rubber bushings are available for just about every application for Honda/Acura products thru Mugen. I do not know who manufactures hard rubber for the Mini...

If you were driving your mini on the street and spending a weekend or two on the track I would opt for hard rubber bushings in a few places, but not poly, ever. I would begin with the front control arms and then perhaps the rear suspension and that's it. Just be cautious; if you stiffen up the bushings in the front end and leave the back end stock, you may end up with a car that is a little out of balance, and balance is key. If you are racing the car, I would still suggest hard rubber; I feel these bushings will last longer, allow the suspension to move as design, and, they are more comfortable. Don't discount comfort while racing either. Getting beat up by the cometition is on occasion acceptable. Getting beat up by your own car is not!

I installed all poly in the 99 Si and it turned-in like snot and went around corners without any compliance. I also found that the rear trailing arms did not work well with poly. When I removed all the poly - except for sway bars - and installed hard rubber I found the car much more comfortable, had 90% of all the best characteristics of poly, and, allowed the back end to work properly - far less twitchy - and I was running 400lb linear rate Eibachs up front, 600lb linear rate Eibachs in back with Koni dampers modified for SST - Show Room Stock with a 25mm rear bar. I also drove 45K-55K commuting miles per year in this car and every mile with poly killed me.

Auto crossing is perhaps a place best suited to poly, but then, autoXing goals are very different from road racing and street driving. With front wheel drive, rotation (oversteer) and grip are king on the auto Xing circuit.

DO NOT replace rubber engine mounts with poly unless you have a good set of ear plugs.

Oh, complaince on bumpy B-roads for example is basically lost with poly. The car will hop and dart all over making for a rather involving ride.

This is a quick response, so excuse any grammer errors.

 

Ditto.

 

very well said, Meb....I had poly bushings in the front control arms,
front and rear sway bars, front engine mount, and shock tower bushings
in my old 82 VW Rabbit, and it was pretty harsh (no binding, however,
and no squeaks, they were teflon-impregnated). Much better after I
changed to hard rubber for the front engine mount and front shock
tower bearings (the control arms were too much of bear to re-do).
This is why I only changed the rear sway bar bushings on my MINI to poly
....(would have done the front's too, but that would have edged it a
little toward more understeer.)

 

Thanks Cristo, tomslick. I will tell you Cristo that the best feeling car I have owned to date was a 1988 VW Jetta GLI 16V. Despite a rather archaic rear suspension, this car had some great moves. It was not a slalom king nor a cornering moster. Just an awful lot of fun on unpredictable twisty roads. At the time, Car and Drvie described this VW as a "wicked accomplice" and it was. Steering feel was superb, much better than the Mini's in this driver's opinion. Steering feel is a lost art today. You can do a lot with a car that communicates well. I installed poly inserts in the rear most bushing in the front control arm on the VW and the improvement was very quick turn-in without adversly affecting anything else

Evenutally, at 170,000 miles, the tranny blew to pieces at 115-120mph or so; holes in the hood, holes in the windshield. Scared me! I had tranny fluid all over my face...very hot stuff.

 

oh, forgot....I also had poly steering rack bushings in the Rabbit.
by the way it was my daily drive for 21 years....had HOR lowered
progressive springs and Tokico Illumina shocks (thank god for the
"lifetime" warrantee...went through about a dozen over the years),
upper and lower stress bars, SS exhaust, bigger airflowmass sensor,
throttle body, a good stereo, good alloys/summer and winter tires,
and lots of other goodies...it now belongs to a service tech at
York VW who bought it from me and is his daily ride (although he
redid a bunch of stuff and I hardly recognize it now).
BUT the MINI is MUCH NICER!!!

 

The honda is sitting outside my office window waiting for a new owner. Sitting on the passenger seat are three hard rubber steering rack bushings. I could not find anyone to install these without first removing the entire steering wheel/airbag system first. This despite fairly easy access from below...to far under the car for my to try in my driveway. I would expect these to make a most profound difference. Someone else will feel the difference.

 

Rubber and hard rubber are the ticket until you decide to kill all comfort and go spherical bearings

 

Are the powerflex bushings that some have reported using with success hard rubber or poly? I couldn't find anything that describes the material that they're made out of.

TIA, Jeff

 

how much polyurethane deforms depends on the durometer. a low durometer poly will deform a surprising amount.

i had this concern when looking for mcs rear control arms. you can actually see the h sport poly bushings deflect under just a little off center load.

 

I can remember holding several bushings in my hand, noting that the sway bar bushings - curiously - were softer than all the others. Most of the poly bushings designed for my previous car's suspension were wraped in very thick steel jackets. A few also had very thick steel dowels running thru them allowing stock bolts to be used. So, in reality, there was very little poly material and what did exist, was shrouded in steel - very little flex. Measuring the stiffness of the poly is not enough; the total bushing, steel and poly must be measured.

The impression I wanted leave for everyone is that poly is indeed very stiff and the application will affect handling behavior for better and worse. A durometer will indeed measure how hard a poly bushing is. But also, highlighting how a bushing might work was also on my mind; poly is indifferent - relatively speaking - to the controlled, multi-directional designed-in movements, as noted in an example above, that allow for toe changes. For these applications, poly is wrong. For other applications poly may be too hard for the street, but if the suspension works, be my guest. Your kidneys will protest, however. Hard rubber just makes more sense for most applications unless the car is a track only car. Then, one might employ other suspension strategies that side-step poly too.

Let me point out one other underlying concern; cost. Removing and reinstalling bushings is very time concuming and costly, if done properly. I went the all poly route and decided to employ all hard rubber after some fairly bad experiences. It is your money folks, but be careful. Your car will not necessarily handle better...it may actually handle worse. It's not a black and white choice. Stiffer isn't always better. I'm simply trying to help you all avoid a costly mistake - be careful!

 

simplistically, you can think of polyurethane as a better version of rubber; it flexes and returns to its orignal shape, is incredibly tough and free from degradation due to ozone exposure. by choosing the durometer, you can make it the same stiffness as the original rubber or way stiffer (skateboard wheels are about 100 durometer, for example). Poly urethane has poor friction characteristics and is not suited for sliding or rotating bearings.


delrin is another thing altogether; very little flexibility but quite good friction characteristics.

 

I know that you (jlm) have commented that you felt that the powerflex bushings have worked out well for you. I've planned (for a while now) to get some added to get rid of the infamous wandering suspension (that's gotten progressively worse over the months.)

I'm at the point now where it's going back into the dealer not for them to fix it as much as to figure out if I just have spent bushings or another problem. If it's the bushings I'll replace with aftermarket and keep the car. If I'm essentially looking at a problem I have no easy solution to, however, it's going on the block.

Thanks for any feedback. It's very much appreciated.

Jeff

 

It has its place and I agree it is more durable in some ways than rubber. Poly is not the smoking gun fix for handling that some folks may believe. I may consider using poly in my Mini at some point. But I personally will balance that decision against potential handling gains and comfort.

As an aside Friedduck, wandering can be attributed to many things. Begin by looking at the least expensive potential. Unless you've driven your Mini over 100,000 miles, your stock bushings are probably okay...unless your driving style is super aggressive say 100% of the time. Tie rods, loose steering rack mounts, low tire psi, worn dampers, improper alignment, etc. are areas to look first. If you have a coilover system installed and the corner weighting is off by a lot, wandering will be a problem.

 

Actually, bmw control arm bushings will easily wear out in 50k miles. Mine have gotten completely out of control, but I'm not 100% on what to replace them with. I may give the power flex a go pretty soon.

meb, I think I chatted with you in another thread a while back about weird handling characteristics. Turns out my problem was the beginning of the end of my control arm bushings.

 

I ended up selling the MINI because no one could figure it out (the handling problems.) Even when I wrote down a list of the things that it could potentially be, offered to pay for a full alignment, and insisted that they treat it as a serious problem (my wife wouldn't drive it any more) I got condescending or just off-base responses from the dealer. (Their last stab at it was to suggest that the power steering needed to warm up before it would work correctly.)

It's someone else's problem now.

There was no one else in the city that I could find that could fix it, unfortunately, and I was looking to the dealer as a last resort. I may look to owning a MINI at some point in the future but it would only be a situation where I knew I had access to a decent wrench!

Jeff

(PS: I still get e-mail notification from this board when people respond, if you were wondering...)

 

...sorry to read this.

Did you modify your car in any way that may have caused the wondering? Was caster/camber equal both sides? Rear toe and camber settings, equal? I feel stability can be affected more-so by the back end. If your car had a toe out condition in the back end, I would certainly expect wondering...if not a little unexpected oversteer on occasion.


Michael

 

Well, 60,000 miles and about 60 track days and my front control arm bushings are failing. (Just replaced the wheel bearings and need belt tensioner assembly done, as well.)

From reading this thread and speaking with Eric at Helix, it seems as if polyurethane is not the way to go. Is there now a hard rubber bushing replacement available? Are there any other bushings that I should take care of while the control arm is out?

For reference, I have adjustable camber plates for the front, an adjustable sway bar and adjustable lower control arms for the rear. The car is also lowered on H & R Springs.

Thanks for any input.

 

I've searched the universe for harder rubber bushings for the lower control arm. Found nothing yet.

Also, and based upon experience with simialr control arm layouts, you - we - might be better served by keeping the front bushing stock and replacing only the rear one with hard rubber...or poly if you must have something different.

I experimented with poly front and rear, poly rear stock front, hard rubber front and rear, and hard rubber rear and stock front. I found the last combination the most comfortable and I would be splitting hairs if I wrote it performed worse.

Lots of work, however.

 

If I could get harder rubber bushings for the front control arms, I would accept the compromises as the car is already pretty stiff and uncomfortable on the street. As for polyurethane, it sounds as if it is so effective as to be a real pain to deal with.

 

From what I understand, the realy hard poly ( poly can be soft too) bushings available for say some of honda's products, do not allow the suspension to work properly. For example, if there is a certain amount of toe compliance required to keep the car safe as the suspension nears full compression, hard poly will not allow this to happen. In other applications it is great. But, I removed all my poly - except for swaybars.

 

So have you actually used the poly front control arm bushings? I ordered some about two weeks ago, but some mini tuners must have a different definition of "shipped" than I do . Although I would like a little more toe and caster control, my main concern is frequency of replacement of stock bushings.

These bushings seem to be a bit of a mystery. There are few comments about them, no how to's, even the photo's for them seem to be just a generic bushing shot. The picture shows them as being modular.

I'm very curious about these. How or do they need to be lubricrated? Are they modular? If they ever show up, I'll answer these questions and more (read that part with a newscaster's voice).