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Hi Lo's - Adjustability Question
https://www.ausmini.com/forums/viewtopic.php?f=2&t=38941		 Page 1 of 2
Author:  Boyracer [ Thu Dec 20, 2007 10:51 pm ]
Post subject:  Hi Lo's - Adjustability Question
Just a few questions regarding adjustable suspension.

Can anyone tell me if it's adjusted low, does the car ride harder and sit flatter through corners? And conversely, if you raise it up a bit, does the ride become a little softer and does it start to get sloppy in corners?

Can a Mini get sloppy in corners?
Author:  m1n1 [ Thu Dec 20, 2007 11:03 pm ]
Post subject: 
Yeah, you've got the idea.

But a Mini thats "sloppy in corners" will still out corner most things on the road.

A lot of the difference in cornering ability of different minis comes down to tyre choice and wheel size.

Cheers,
Ray.
Author:  Mini Mad [ Thu Dec 20, 2007 11:15 pm ]
Post subject: 
I disagree - you are not changing the 'spring rate' of the rubber cone when you raise or lower the car, it should not become harder or softer. You ARE raising or lowering the roll center which will affect handling - if TOO low it will ride harsh not because you stiffened the suspension up but because it is so low that there is no travel before the top arm reaches the bump stops. You still need suspension travel to handle well and safe, it's not good to be riding along on the bumps stops...for your car, handling and your teeth.

It may feel like it's less sloppy but really you are just limiting the travel, which may be better or worse depending on what you started with though..
Author:  m1n1 [ Thu Dec 20, 2007 11:33 pm ]
Post subject: 
You are changing the ratio between suspension movement and cone compression (because you are changing the trumpet length), so effectively the spring rate is changed.

Yes, the roll centre is being changed also.

Good point, Mini Mad, re the lowering to the bumpstops.

Boyracer, for a daily driver you don't want the suspension too low and stiff.

With a Rover Mini used as a daily, which is what you were asking about in a previous thread http://www.ausmini.com/forums/viewtopic.php?t=38793 , I would suggest a Moulton Smootharide kit which includes new cones which give a better ride quality (approaching that of Hydrolastic).

Perhaps I should say that a Mini with lowered suspension, grippy tyres etc will give you outstanding cornering ability, but a standard Mini will corner very well anyway. I would suggest that a Mini with standard suspension and average tyres will be great fun on the road, because you can "play" with it a bit. You can drift into corners and around roundabouts. Whereas a "maxed out" Mini will hang on until much higher speeds before it will drift - not a good idea on public roads.

Cheers,
Ray.
Author:  smac [ Fri Dec 21, 2007 4:57 am ]
Post subject: 
In what way has the suspension 'ratio' changed? :roll:
Author:  spraycanmansam [ Fri Dec 21, 2007 5:31 am ]
Post subject: 
smac wrote:
In what way has the suspension 'ratio' changed? :roll:


m1n1 wrote:
the ratio between suspension movement and cone compression (because you are changing the trumpet length), so effectively the spring rate is changed.


:roll:
Author:  gafmo [ Fri Dec 21, 2007 5:45 am ]
Post subject: 
Minimad has it rite in my book. the rubber cone rate of compression is only changed if you are riding on the bumper stops which will limit the amount the rubber cone is compressed sa you are useing the stops
Author:  spraycanmansam [ Fri Dec 21, 2007 5:59 am ]
Post subject: 
gafmo wrote:
Minimad has it rite in my book. the rubber cone rate of compression is only changed if you are riding on the bumper stops which will limit the amount the rubber cone is compressed sa you are useing the stops


I dunno who's right! :lol: Just clarifying m1n1's statement for smac :wink: Don't worry, I'm staying outta this one as suspension's not my thing :evil:

From what I gather, I think m1n1's talking about when you lower the car from standard the cone's are already pre-loaded, which affects how they ride. Much the same as ricers who dump their cars with only lowered springs which preloads the shockies which makes for a crap ride and wears them out a lot faster. That's all I'm saying! honest... :wink:

I could be wrong, it's 6 am... 8) :wink:
Author:  drmini in aust [ Fri Dec 21, 2007 6:00 am ]
Post subject: 
I agree with Gafmo. There is hardly any angularity change in the suspension (ie ratio change) with the normal amount you would adjust Hi-Los. Ratio is still about 3:1 in front and 5:1 in back.
Note if using comp hydro rear bumpstops it's permissible to ride on them- they are aeon springs and have a progessive rate. :wink:
Author:  smac [ Fri Dec 21, 2007 7:21 am ]
Post subject: 
Ya I saw the statement, and that's the bit I wanted clarified (cause it's bollocks :lol: )
Author:  gafmo [ Fri Dec 21, 2007 11:20 am ]
Post subject: 
once you are on the Bumper Stop..the Cone rubber is not doing its job..the Buumper stop is
Author:  Anto [ Fri Dec 21, 2007 11:59 am ]
Post subject: 
I don't know how you change the spring rate without changing the spring (or rubber cone in this case). You can have an effect on it by altering the preload but the spring rate is still the same.

In the case of hi-los, raising the car will have little effect on the actual rubber cone, and the handling difference would be more down to the points stated - hitting the bump stops, raising the centre of gravity or altering the geometry of the suspension (camber for eg).
Author:  m1n1 [ Fri Dec 21, 2007 10:33 pm ]
Post subject: 
The real reason that a mini corners better when it has been lowered, apart from the lower centre of gravity, is because the camber angle has changed.

A normal mini will have between 0.5 and 1.5 degrees of POSITIVE camber. As the car is lowered the camber angle becomes more and more negative. On cars lowered to their maximum (just off the bump stops) it will have become around 0.5 degrees NEGATIVE camber.

This is something that needs to be taken into consideration when fitting things like negative camber bottom arms. Too much negative camber (more than 1.5 degrees negative) can result when putting these arms onto a lowered car.


Let me clarify wat I said earlier about lowering and a stiffer ride.

As a suspension trumpet is progressively shortened, the angle between the top arm and the trumpet changes, ie lowering by only 1.5 inches the suspension ratio changes from 1/3 to 9/30 ( a 10% change), so the rate at which the cone is compressed as the wheel moves up into the arch is increased.

The trick with rubber cone suspension is that, unlike most coil springs, the "spring rate" changes as the cone is compressed. It is not constant.

The more the rubber cone is compressed, the higher the spring rate becomes.

So put these two things together and lowering a mini results in a stiffer ride, even before you get close to the bump stops.

This small increase in stiffness over the new lowered range of suspension travel will do little to improve handling, but it explains the "jiggliness" of the ride quality of a lowered mini.

Of course, if its lowered enough for the top arms to hit the bumpstops the "jiggliness" will become horrible suspension "crashiness".


Anyway, feel free to take whatever I say with a grain of salt - I'm only another bloody mechanical engineer :roll: :wink:
Cheers,
Ray.
Author:  Boyracer [ Fri Dec 21, 2007 10:38 pm ]
Post subject: 
Thanks for all the replies, guys.

I've just gotten home in the green car that is/was on the NSW Club's Trader section! :P :P :P

From what everyone's written above, I can see I have a fair bit to learn. I don't even know what the setup is, so the first step will be to get myself a workshop manual. It's probably a bit late now to ask Santa for it. :roll:

Ray, you mentioned tyres. That was going to be my next question. Is there a general consensus on this or is everyone everywhere on this?
Author:  Morris 1100 [ Fri Dec 21, 2007 10:40 pm ]
Post subject: 
Boyracer wrote:
Ray, you mentioned tyres. That was going to be my next question. Is there a general consensus on this or is everyone everywhere on this?
The general consensus is that you need tyres. :lol:
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