11 replies to this topic

[prosper ysbeer]

Hello all,
there are 2 kind of front subframes : those fixed with 4 bolts and those fixed with 2 (very thick) bolts

 

in the case of 4 bolts - or so called dry mount-  no rubbers are mounted between the fforward bulkhead and the top of the subframe and between the subframe tail and the bottom of the footwell. 

in case of the 2 bolts - the so called  rubber mount - there are rubber in those places 

in french those rubbers are called "silencers"

 

Is there a technica reason why I cannot apply rubbers between those fixation points ( I'm not talking about the standard onces but "homemade" rubberor plastic)  in order to reduce noise levels in the passenger area. 

 

I have a terrribly noisy mini on the inside  while on the outside it  "zooms"  like a bumble bee  I would definitely come last in loudest exhaust competition  even a full revs ... but i cannot drive an listen to the radio ...

 

I'm working on the soundproofing of the firewall and footwell

all suggestions wellcome 

 

prosper

[Carlos W]

Cars with rubber mounted subframes are said to lose a lot of their handling feel (I've never compared them so this isn't first hand experience)

[Cooperman]

The rubber mounted sub-frames were introduced to help to sell Minis to older age-group by, in theory, making the car smoother in terms of NHV. However, the rubber reduces the old 'precise' feel of the steering and is regarded as a detrimental modification by most Mini enthusiasts.

Solid mounting, however, makes little difference in practice and is the best way to treat a Mini. At all costs avoid the 'poly' mountings as they are very far from ideal.

You cannot rubber mount a 4-tower-bolt front sub-frame, nor should anyone want to.

[CityEPete]

The poly mounts should be removed from all stockists imo, they are junk.

[Cooperman]

The poly mounts should be removed from all stockists imo, they are junk.

+1. They are total c**p.

 

I have been thinking about some different solid mounts for rubber mounted frames.

The issue with solid rear mounts is the state of the toe-board onto which they attack.

I am thinking of a mount with a longer mounting which could go right down to floor level then be curled under to take 2 extra 5/16" bolts through the floor and maybe 2 more right at the bottom of the toe-board.

Then it would be fitted in a similar way to the early cars where the sub-frame loads went into the floor to toe-board joint area.

[prosper ysbeer]

The rubber mounted sub-frames were introduced to help to sell Minis to older age-group by, in theory, making the car smoother in terms of NHV. However, the rubber reduces the old 'precise' feel of the steering and is regarded as a detrimental modification by most Mini enthusiasts.

Solid mounting, however, makes little difference in practice and is the best way to treat a Mini. At all costs avoid the 'poly' mountings as they are very far from ideal.

You cannot rubber mount a 4-tower-bolt front sub-frame, nor should anyone want to.

Thanks all for contributing

 

Hi Cooperman,

 

I would like to discuss your statement further,  from an engineering point of view whether you put rubber cones as suspension, spring coils or you use the hydrolastic you would indeed feel a difference in handling of the car , becuase you put rubbers in place where they actually link up with moving parts that make them function as part of the suspension and that  is clearly documented and shown in the adverts for different types of replacement suspension parts .

However when you put a flat rubber between the bulkhead and the top of the subframe the pressure would be exerted for 90% by the bolts that hold the subframe in place not by the weight of the car, there are no moving suspension related parts ther  and therefore  the pressure on such rubber pad wouldnt (significantly) change during cornering or on uneven roads, yes in the latter case there might be a slight change in pressure but never less then the pressure exerted by the bolts keeping the subframe in place . 

 

Actually the point of the exercise is to dampen the transfer of vibrations from the subframe to the body work, that is why the french call the rubber "silentblocs" (block-silencers) , and the use of a rubber or a sminlar polymer would indeed have that effect .  

 

I was told - much like you did-  there are no rubbers that I can use between a solid mount subframe, often this statement is made that it cannot be done (based on teh assumption there are no parts available) ; however to conclude  from the unavailability that therefore it cannot be done is engineeringwise cutting corners. 

 

Now what is the issue at hand here : what I want to know is why i cannot be done ? 

a) is it because there are no parts , in other words if I make from scratch a rubber or polymer pad and insert i between the top of the subfame and the bulkhead, that would actually be a workable solution ?  what would be the result ?  and what would be the issues
b) can someone  form first hand experience tell me  that it actually does influence the handling (suspension)  or has anybody has experimented with solid mounting  a rubber mounted subframe, and what were the results ?
c) is there a problem with the length of the mounting bolts ( either the double or single bold ) ie that they are too short and cannot bridge the extra few millimeters. 

 

thanks for further suggestions        

[Cooperman]

Personally I can see no advantage in trying to re-engineer the original sub-frame mounting method. The pity is that the Austin-Rover designers ever tried it. It has proved to be a very poor decision as the on-going need to revert back to an all-solid mounting system has proved.

Putting some, say, 1 mm thick rubber pads under the main sub-frame mounts and between the front mounts and the front panel would do nothing in terms of NHV and would be a waste of time. Thicker would change the installation geometry for no advantage.

Of course, any engineering change such as this is possible if enough time and effort is allocated to it, but one must ask 'for what purpose'? The beauty of the classic Mini is in its simplicity, road-holding and overall performance.

Whenever I get a Mini with a rubber mounted sub-frame I always fit the solid mount kit. It does not increase NHV in any discernible way, but it improves steering and consequently in overall 'feel' on the road. It also removes the constant failure of the rubber mountings in service and makes the entire structure stronger.

The Mini was originally designed to have the front sub-frame mounted solidly.

[CityEPete]

Many people have fitted solid mount kits to cars that came with rubber mounts and confirmed the results to be much better, I wish I had done it to mine now instead of the poly ones I had to change after a week to factory rubber ones, next time the frame comes out it will be solid mounted after.

[prosper ysbeer]

Many people have fitted solid mount kits to cars that came with rubber mounts and confirmed the results to be much better, I wish I had done it to mine now instead of the poly ones I had to change after a week to factory rubber ones, next time the frame comes out it will be solid mounted after.

So the more rigid solid mount kit improves the handling of rubbermounted subframes,  can somebody with expierence of such a change tell me what/how precisely the handling improved ?   

[Cooperman]

It's not so much the handling, which is the way the car responds to inputs of steering braking and power application, it is the accuracy and more precise 'feel' of the car on the road, so yes, it is peripherally involved in the handling but more importantly it is the steering response which is the biggest advantage..

The Mini was designed by Sir Alec to have the sub-frame mounted solidly to the monocoque body-shell. That's the way it was during the first half of its production. Then the idiot engineers at Austin-Rover made changes in various areas which didn't improve the car at all. The rubber mounted sub-frame is a prime example. That brought in less precise steering, a reduction in reliability due to constant mounting failures and some odd loading on the structure when, say, one mounting had failed and all the dynamic loads were then transmitted via the remaining mounts.

They did other stupid things too such as mixing imperial and metric threads on the safety-critical braking system and allowed the corrosion resistance to become even worse.

In terms of absolute handling, the early cars with solid mounted front sub-frames, 3.5" wheels and narrow tyres were the very best.

[prosper ysbeer]

It's not so much the handling, which is the way the car responds to inputs of steering braking and power application, it is the accuracy and more precise 'feel' of the car on the road, ..engineers at Austin-Rover made changes in various areas which didn't improve the car at all ... mounting failures and some odd loading on the structure

They did other stupid things too such as mixing imperial and metric threads ..

the early cars with solid mounted front sub-frames, 3.5" wheels and narrow tyres were the very best.

 

Tell me about imperial and metric threads B-(    ( as a matter of fact i did measure some bolts and I think they even had imperial size 6 faced heads on bolts with metric diametre and threading   ...

the 3.5" wheels I have them in my garage , but I have to disagree with you on the fact that they are better :  the 5"wide wheels and tyres are much better with good tyres (compound wise)   they have more lateral resistance then the narrow tyres  and the modern compounds allow for less roll-resistance  while allowing more water to be evacuated from underneath the tyre in rainy conditions,  

Actually afa the inverse rubbermount -> solidmount  is concerned it does indicate a positive influence, the wear of rubbermounts does seem to indicate there is enough change in the pressure to influence handling and eventually suspension  and geometry ... and that is soemthin I didn't expect 

[Cooperman]

 

It's not so much the handling, which is the way the car responds to inputs of steering braking and power application, it is the accuracy and more precise 'feel' of the car on the road, ..engineers at Austin-Rover made changes in various areas which didn't improve the car at all ... mounting failures and some odd loading on the structure

They did other stupid things too such as mixing imperial and metric threads ..

the early cars with solid mounted front sub-frames, 3.5" wheels and narrow tyres were the very best.

 

Tell me about imperial and metric threads B-(    ( as a matter of fact i did measure some bolts and I think they even had imperial size 6 faced heads on bolts with metric diametre and threading   ...

the 3.5" wheels I have them in my garage , but I have to disagree with you on the fact that they are better :  the 5"wide wheels and tyres are much better with good tyres (compound wise)   they have more lateral resistance then the narrow tyres  and the modern compounds allow for less roll-resistance  while allowing more water to be evacuated from underneath the tyre in rainy conditions,  

Actually afa the inverse rubbermount -> solidmount  is concerned it does indicate a positive influence, the wear of rubbermounts does seem to indicate there is enough change in the pressure to influence handling and eventually suspension  and geometry ... and that is soemthin I didn't expect 

 

I believe you are not defining between 'road-holding' and 'handling.They are completely different. To define them:

 

Road-holding is the direct measurement of centripetal force which can be generated when driving in a constant radius circle on a given surface. This is dependent on the tyre size & compound, the suspension settings, the roll resistance, the road surface and some other less critical factors.

 

Handling is the way the car responds to the steering, braking and power application. It is more subjective and depends on different factors.

 

For example, a rally car with forest tyres will have very poor road-holding on a firm tarmac surface, but with its compliant suspension and well-set-up suspension settings it will be a much better handling car than a race car with huge wide slick tyres, low C of G and a rear anti-roll bar.

 

With 3.5" wheels and the narrow tyres the handling is fantastic. The way in which such a car responds to the steering input and the predictably when braking are about the ideal. Of course a car with better and softer tyres will stop better in the wet (and probably in the dry), it will achieve a higher cornering force, but it will not 'handle' as well. The finest handling car I think I've ever tested was a Mk.1 Escort Twin-Cam with forest tyres. The road-holding was not good, but it would hold a sideways stance through a long corner with power on and a small amount of negative (opposite) lock with ease and it gave the driver great confidence. Now that is handling.

 

One of the worst handling cars I've driven was a Porsche 911 Carrera on full racing tyres. The road-holding was incredible, but it felt unpredictable and that it would 'bite me in the bum' if I got it wrong. It turned out that it had the wrong rear anti-roll bar, one for forest rallying, and once changed it was super in both areas.

 

With regard to the metric threads, the wonderful ARG engineers, in order to save money, decided to fit the front/rear pressure valve (the one on the bulkhead) with a unit having 10 mm fine metric threads. However, the other ends of those pipes have 3/8" UNF threads and it is possible to fit them the wrong way around (with a bit of 'graunching') and have a system which leaks brake fluid. This on a safety critical system. You couldn't make it up. It is typical of the reasons why Rover went under - sheer incompetence!