24 replies to this topic

[russ_1380]

HI all.


Considering a rear beam axle conversion for my Minus.

Reading a few past threads, I believe there is some confusion (certainly on my part!). There are a few products marketed as a 'beam axle' but these are not true beam axles, more like beam subframes.

Can someone please explain the difference to me between a true beam axle and a beam subframe like the Huddersfield type, I'm a tad confused.

I see Force off a tasty looking one but it is dear. Has anyone tried this item?

Cheers

Russ

[russ_1380]

any tips/suggestions?

[Ethel]

The Force one is also a subframe replacement. A true beam axle solidly connects bot wheels together, like a live axle you'd find on an old style wagon with leaf springs, but usually with more sophisticated multi link suspension. You'd most likely have to remove the boot floor on a Mini to make clearance so usually only found on track cars.

any tips/suggestions?

[MRA]

I have built a few over the years and they can be made to fit under the floor, but it isn't ideal and you lose a fair amount of ground clearance, as ETHEL (who is not a girl) says normally you lose the boot floor, but the handling improvements over trailing arm are amazing

[russ_1380]

Cheers guys and girls

I think I understand the difference now. So basically all the 'kits' available are beam subs rather than true beam axles where the wheels would be joined?

MRA, when you mentioned the handling improvements were you referring to the beam subframes or the full blown true beam axle conversions?

In your opinions, do the coilovers and beam subframes make much improvement over a well setup standard rear subframe with decent dampers and competition rubber springs?

thanks again

R

[russ_1380]

Just been researching suspension designs......

From what I have read, I think I'll stick to the standard rear mini setup for now.

One thing though......when Vizard made his true rear beam axle (wheels connected), from what I understand this has some advantages...however can someone please explain what advantages this had over using a standard mini rear (independent) suspension with an anti roll bar??

Surely they would acheive simialr results?

i.e why is it better to use a beam rather than independent system wi a roll bar? I understand roll bars lose some of the independentness but surely its very similar to a true beam axle in advantages/disadvantages? I'm confused!


http://i25.photobuck...c/IMAGE_007.jpg


Cheers

R

[Ethel]

A proper beam is a bit like having one extra wide wheel - wiv a very wide groove in the tyre!. Having both wheels on the same axis (give or take a bit of static camber) means pressing one hard into flat tarmac keeps the other square to the surface too. Radius arms would actually be the ideal suspension if you eliminated body roll.


It's all about compromise:

You can drive one wheel on a trailing arm over a bump without it changing it's camber and steering itself in the same way you steer a bicycle (ignoring body roll). Lift one end of a beam axle, with a bump, and you tilt the wheel on the other end.

However, go round a smooth bend and the beam will keep both wheels pretty much perpendicular to the road, whereas independent radius arms will stay perpendicular to the subframe they are bolted to, which rolls on the suspension springs.

[MRA]

Russ 1380, I was referring to FULL beam axle NOT beam frames.

The only advantages a beam frame have over a standard subby is a weight saving and the possibility of easier adjustable suspension.

A FULL beam axle gives much better turn in and a higher degree of stability at speed, and of course a lot more adjustability

[russ_1380]

Thanks MRA + Ethel, I understand now.

I see what you mean by the advantages of a beam frame; in reality all you are getting is a small weight saving over the std subframe plus the easier adjustment of coilovers.

Out of interest are coilovers heavier than the normal mini dampers? I'm thinking with regard to unsprung weight. I can't see any figures on the suppliers websites. If this is the case (say a coilover beam subframe system having a higher unsprung weight) then surely the std mini setup would be more responsive/react quicker?

Presumably the std mini rubber cones are not part of unsprung weight as they are fixed to the body via subframe or am i getting confused again?

Do you think most people go for this beam subframe and coilover conversion for simply the added bonus of easier ride height/firmness adjustment over a std mini setup, or do coilovers offer a significant ride/handling improvement over std rubber cones?

Apologies for banging on but I'm quite interested in this topic (as well as a tad confused lol)

[Ethel]

Yes they are heavier, but it would be difficult to work out how much of the spring is unspung weight! Weight saving is the biggest difference but because of the lever effect of the radius arm on the standard suspension it also reduces effective unsprung weight: coil overs compress as much as the wheel travels and share carrying the radius arm with the pin at the other end. The rubber cone gets the weight (& inertia) of the wheel multiplied 5 times by the radius arm which is hanging free on a pin at one end (ignoring the shock absorber - as coilovers have one of them also)

Thanks MRA + Ethel, I understand now.

I see what you mean by the advantages of a beam frame; in reality all you are getting is a small weight saving over the std subframe plus the easier adjustment of coilovers.

Out of interest are coilovers heavier than the normal mini dampers? I'm thinking with regard to unsprung weight. I can't see any figures on the suppliers websites. If this is the case (say a coilover beam subframe system having a higher unsprung weight) then surely the std mini setup would be more responsive/react quicker?

Presumably the std mini rubber cones are not part of unsprung weight as they are fixed to the body via subframe or am i getting confused again?

Do you think most people go for this beam subframe and coilover conversion for simply the added bonus of easier ride height/firmness adjustment over a std mini setup, or do coilovers offer a significant ride/handling improvement over std rubber cones?

Apologies for banging on but I'm quite interested in this topic (as well as a tad confused lol)

[mini-geek]

I don't think you would want to reduce the rear end weight in a minus any more it could become too light!

[Ethel]

Not really, the lighter it is the less inertia it has to control. Coilovers are often more use on lightweight cars because standard suspension becomes too stiff.

I don't think you would want to reduce the rear end weight in a minus any more it could become too light!

[russ_1380]

hahha, yes maybe!

I'm just toying with ideas, but will probs stick with std rubber cone set up.

Just searching on the forum now for coilover info. It seems that many people have mentioned its hard to setup the rear properly to make the slight oversteer more predictable. I'm assuming this is due to improper setup of the car or driving technique.



From my quick bit of research I think i've got the hang of the options for mini rear suspension now:

1.) Standard mini setup:

- Rubber cones/trumpets/dampers
-Independent setup
-Tried and tested
-Keep things simple, can't go wrong (he says.... lol)



2.) Standard mini setup wi conversion springs rather than original rubber springs:

-Independent setup
-Sounds good but maybe lose the fun mini ride


3.) Standard mini setup but with anti roll bar (for use with rubber cones or spring conversion):
-Independent setup
-This might look like an option for me
-I need to read more in to it though, not sure if i really need a roll bar


4.) Coilover kit with std mini rear subframe:

-Independent setup
-Easy adjustment of height/ride
-Might lose mini feel

5.) Coilover kit with beam subframe (alloy or steel):

-Independent setup
-Weight loss
-Easy adjustment of height/ride
-Might lose mini feel

6.) Full beam axle conversion (like Vizard picture):

- Non independent
-As ethel/mra mention would be a brillant setup
-No off shelf conversion kits about
-I wouldn't attempt to make one as I don't know what I'm doing lol
-Having one made could be £££
-Might alter the mini's handling nature significantly (probs more than my driving skill will allow me to cope with)
-Needs to run coilovers


Phew.....no wonder I was gettin confused!

Now i just need to pick one........

Again, reading all this stuff about reducing unsprung weight......do you guys think there is a noticeable difference on a road car?

From what i understand reducing teh unsprung weight helps by allowing the suspension components to react quicker.

[Ethel]

This excellent book will tell you more than you want to know about suspension & chassis design for amateur builders & modders. It even features quite a bit of Mini specific detail.

[russ_1380]

Cheers man, i appreiate it

i'll look for a used one, i'm cheap lol


Out of interest do you know anyone who offers a beam axle 'kit' or can fabricate them?

I'd quite like something different as I'm hoping to get m minus in the mags when its finished and from what mra mentioned, they make a huge difference to turn in