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Suspension Bounce?


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#1 Tornado99

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Posted 05 July 2020 - 12:40 AM

I've had my 1988 Mini for all of two weeks. Lots of things to learn. Riding it around town, I've noticed it tended to oscillate when I come to an otherwise smooth stop. I can feel an forward end up/down motion for maybe 2 or 3 cycles before it settles. Car has rubber cones and poly urethane bushings throughout which all seem to be fairly new (whole car restored maybe less than 5 yrs ago). Is this normal or could the shocks/dampers be needing renewal?



#2 MiniMadRacer

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Posted 05 July 2020 - 08:42 AM

As you suggest I would check the shocks... take them off the car and push / pull them up and down and see if there is any resistance



#3 cal844

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Posted 05 July 2020 - 01:44 PM

Ditch the front subframe polybush mounts. Fit either all solid or all rubber.

#4 mab01uk

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Posted 05 July 2020 - 06:10 PM

Worn Shocks/dampers are likely the problem.



#5 luismx123

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Posted 05 July 2020 - 07:00 PM

Had this issue when I set my rear shocks to the same setting as the front. Car would bounce alot. Check to see if you have adjustable shocks and set them lower/higher and keep trying

#6 Tornado99

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Posted 05 July 2020 - 07:28 PM

Ditch the front subframe polybush mounts. Fit either all solid or all rubber.


Please explain why drop the polyU bushings? They should firm things up and keep them that way far longer than stock rubber.

#7 Tornado99

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Posted 05 July 2020 - 09:07 PM

Had this issue when I set my rear shocks to the same setting as the front. Car would bounce alot. Check to see if you have adjustable shocks and set them lower/higher and keep trying

 

Appear to be non adjustable...maybe stock, unknown mileage on them.



#8 Clip

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Posted 05 July 2020 - 10:54 PM

I had same problem - classic worn out shock syndrome. I fitted KYB GasAJust all around, made a massive difference. 



#9 Cooperman

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Posted 05 July 2020 - 11:14 PM

 

Ditch the front subframe polybush mounts. Fit either all solid or all rubber.


Please explain why drop the polyU bushings? They should firm things up and keep them that way far longer than stock rubber.

 

Poly bushes for front sub-frame mounting as known to be very poor. For optimum steering response and driving 'feel' it is necessary to solid mount the front sub-frame. All early cars were solid mounted and the rubber mounts were only introduced for NHV improvement, although it is doubtful that anything was actually achieved.



#10 Tupers

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Posted 06 July 2020 - 11:28 AM

Please explain why drop the polyU bushings? They should firm things up and keep them that way far longer than stock rubber.


Sadly not in a Mini as the poly mounts have virtually no steel reinforcement compared to standard rubber mounts. They’re so soft that you can fold the rear poly mounts in half with very little effort.

#11 Spider

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Posted 06 July 2020 - 06:49 PM

 

Ditch the front subframe polybush mounts. Fit either all solid or all rubber.


Please explain why drop the polyU bushings? They should firm things up and keep them that way far longer than stock rubber.

 

 

I did some contract work with one of our Poly Bush manufacturers back in the 80's over a period of about a year or so to assist them in developing their range of bushes for Minis. This was done, but in doing so, I was able to trial all of these bushings and mounts, I was very enthusiastic about all this work and the product, however at the conclusion of the work, while they had a range of bushes they were able to market (and still offer to this day) I did come away from it well enlightened about the material and much as I didn't want to, I drew from that it is not at all a suitable material for suspension bushings when the bushing and mounts were originally designed for rubber. In some cases, had the arrangements been designed for Poly from the outset, they maybe successful, but to retro fit a Poly Bush where a Rubber once was ain't ever going to be any good.

 

Part of the problem is that when deformed, say the Tie Bar Bushes in a Mini, with Rubber they come back to shape, ie, they have a true elastic range, Poly Bushings here will come back a few times to a point, but after around 10 to 20 cycles, it will permanently deform. The other aspect I didn't like is that as Rubber Fails, it does so over a long time, usually one can feel the car is not right and for a good amount of time and even when well shagged out, there's inevitably still some rubber in there. When Poly fails, it cracks and more often than not, falls out wholesale, usually, with no warning.

 

Poly bushes because they don't flex properly, they do better sliding, eg, the Lower Suspension Arms. To do this, they need to be greased, otherwise they will grip the steel pins and rather than slide smoothly around the pin, they grip, let go, grip, let go and in doing so, make the suspension quite noisy in operation and also (in this case) wears the Lower Pin. Because the suspension joints weren't designed for these type of bushings in the first place, any grease applied soon comes out, needing more maintenance than the rubber ever did.

 

This also highlights some of these issues;-

 

zQedLBt.jpg

 



#12 cal844

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Posted 06 July 2020 - 09:38 PM

Thanks for the extended replies Cooperman and MokeSpider, some great information as always

#13 Tornado99

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Posted 07 July 2020 - 01:15 AM

Well thanks for the recommendations on the the bushings. I will be keeping the polyU's on there for the forseeable future but will consider returning to rubbers when they next need replacing. 



#14 Cooperman

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Posted 07 July 2020 - 11:25 AM

Well thanks for the recommendations on the the bushings. I will be keeping the polyU's on there for the forseeable future but will consider returning to rubbers when they next need replacing. 

When they need replacing you do well to fit the solid mounts. Then you will see just how good the steering response and hgeneral driving 'feel' is improved.






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