23 replies to this topic

[Twodogs]

Hi:
Hopefully a simple question as the topic suggests does a coil suspension conversion need to be certified by an engineer " as in a certificate " .

Cheers:
Bill

[mini*mad]

Do you mean the donut replacement springs?

or coilover suspension?

donut replacement springs fine,
coilover suspension is a death trap as all the weight of the shell is on the top shock mounts,
as appose to being spread across a rear subframe and 6 different mounts

ok on the track but needs alot of fabrication to make safe on a normal weight mini OTR

and is this for insurance reasons?

[Twodogs]

Do you mean the donut replacement springs?

or coilover suspension?

donut replacement springs fine,
coilover suspension is a death trap as all the weight of the shell is on the top shock mounts,
as appose to being spread across a rear subframe and 6 different mounts

ok on the track but needs alot of fabrication to make safe on a normal weight mini OTR

and is this for insurance reasons?

Yeah the donut replacement springs ,

and is this for insurance reasons?

No just for getting it on the road .

Thanks for the repy

[mini*mad]

i have used springs for agesss, so much better than donuts

only problem is the rear ones can pop out if you have a mini on 10" wheels, tubbed rear arches and sitting an inch off the ground
other than that they are absolutely fine

[Twodogs]

i have used springs for agesss, so much better than donuts

only problem is the rear ones can pop out if you have a mini on 10" wheels, tubbed rear arches and sitting an inch off the ground
other than that they are absolutely fine

Thanks , yeah im running 10" wheels " more mini'ish " im glad your have a good run with them ...i got them as they are supposed to give a more comfortable ride , Still looking for an installation gutde as i didnt get one with them.

[tiger99]

I would expect that in Australia it will have to be certified by an engineer, as it is a major modification, and very problematic.

Springs have many problems, if indeed they do pop out they are completely unsafe, and in any case can never cope with having variable loads in the vehicle. The rising rate rubber springs are very necessary due to the short suspension travel, unless you only drive with approximately the same load in the vehicle all the time.

[firstforward]

I would expect that in Australia it will have to be certified by an engineer, as it is a major modification, and very problematic.

Springs have many problems, if indeed they do pop out they are completely unsafe, and in any case can never cope with having variable loads in the vehicle. The rising rate rubber springs are very necessary due to the short suspension travel, unless you only drive with approximately the same load in the vehicle all the time.

Can you explain why they are unsafe and what the many problems are?

[tiger99]

Both Cooperman and myself have explained so many times as to why they are unsuitable that I suggest you use the search facility.

As to why they are unsafe, mini*mad says that they pop out, which in itself is quite sufficient.

[firstforward]

So from that answer I assume you have never owned these as Cooperman has never, for me that says it all really, minimad also says he has his car 1 inch off the ground, again that says it all. For your information the ones I use are progressive rate. May I suggest you do not give out advice you are not qualified to, or if you do let it be know its just an opinion.

[Bungle]

you can't get around the fact that at least a quarter (and sometimes more ) of the minis weight is carried by one bolt not designed to carry that much weight

[and90cooper]

So from that answer I assume you have never owned these as Cooperman has never, for me that says it all really, minimad also says he has his car 1 inch off the ground, again that says it all. For your information the ones I use are progressive rate. May I suggest you do not give out advice you are not qualified to, or if you do let it be know its just an opinion.

can you tell me what the advantages are over the rubber donuts,as my car handles very well with donuts.just seems a pointless mod to me

[MRA]

So from that answer I assume you have never owned these as Cooperman has never, for me that says it all really, minimad also says he has his car 1 inch off the ground, again that says it all. For your information the ones I use are progressive rate. May I suggest you do not give out advice you are not qualified to, or if you do let it be know its just an opinion.

You can get rising rate coil springs, there are a few ways to achieve this, that where not readily available 50 years ago.

However once a coil spring bottoms out it will do so with a massive shock loading that the rest of the car would not take kindly too, I appreciate this is going to be fairly rare, just that the chance is increasing as the roads are deteriorating. Compared to rubber suspension medium, i.e. the standard system, which as it is compressed it rises in it's ability to support that load and changes to suit, anyone who has bottomed a standard mini's suspension will also know that the shock can be quite severe, just not as severe as coil spring suspension.

you can't get around the fact that at least a quarter (and sometimes more ) of the minis weight is carried by one bolt not designed to carry that much weight

Bungle are you confusing this topic with "coil over" type suspension which although similar is quite different.

[Cooperman]

For a racing application the advantages are that a much higher initial rate can be achieved which on a totally smooth track can be very good as it removes the initial softness and removes the need to set the dampers quite so hard. Race suspension is a completely different requirement from road suspension.
On the road not only are rising rate springs required, but the rate at which the rate rises must itself rise in order to prevent 'bottoming out'. As the Mini has such a short suspension travel, even at standard ride height it is very important to prevent bottoming out. With coil springs the springs must not be allowed to 'coil-bind' and this can happen unless the springs emulate the rate of the rubber cone springs.
It is hard to see how, on a road Mini, a coil spring can ever be better than a rubber cone.

[adam_93rio]

It is hard to see how, on a road Mini, a coil spring can ever be better than a rubber cone.

That they will probably outlast the car and not cost hundreds to replace every few years?

[MRA]

It is hard to see how, on a road Mini, a coil spring can ever be better than a rubber cone.

That they will probably outlast the car and not cost hundreds to replace every few years?

They may outlast the car, but like all parts springs have a life, irrespective of the material they are made from and the design they are made to.

A coil spring is simply a bar that is being loaded in torsion, twist if you prefer, it will only have so many cycles before failure occurs, and replacement will be necessary, the life of these parts will be determined by the quality of steel used, the surface finish, smoother the better, the usage they are put to, however this is no different than the original rubber suspension, if you fit genuine Dunlop donuts then you shouldn't be changing them every couple of years as they tended to last a lot longer, there are cheaper alternatives that are not as good, and in some cases have been found to be totally unsafe.