Ground clearance

[gizmo]

Hi,

Yesterday my Murena was parked next to my MR2 and I couldn't help but notice how much higher the Murena was off the ground. I have taken some measurments: the lower edge of the front spoiler is 22cm off the ground and the flat bottom of the sill panels (normal 2.2 items) 17cm off the ground at both the front and the back. How does this compare with your cars? Is mine to high? Please get out with the tape measure and let me know.

[krede]

Sounds just about right to me.. think the clearance of a 2.2 should be 15cm.. but i can check, have it on a drawing somewhere.
But the appearance of the Murena deceive quite a bit.
At first glance it seems low, hugging the ground, but in reality it has excellent ground clearance for a car of this type.
The original front spoiler is a very nice design if you ask me..as it lets the nose clear the curbs as you park a feature I soooo would have liked on my old Hoda crx.

That aside I find that the underside of the car is somewhat low to the ground, especially the front suspension assembly.
Building a racer I suspect you want it as low as possibly, but remember that the camber of the rear wheels will also change (quite a bit) if you alter the ride hight..
I did so on my car when i fitted the new springs/dampers, and the difference in camber front and rear is OBVIOUS! now.
Ofcause a bit more camber will increase roadholding in corners... at the expense of tires and bearings.. but my bet is that you know more about that sort of stuff then me

[gizmo]

Thanks for that Krede, however for the record I'm not building a racer just a fast road car which can be used for track days (on the limit with no risk to other road users). The car will probably do 1500 - 2000 km during any year.

Yes, i've done a few calculations and not only does the camber change but so does the toe in of the rear wheels and the roll centers start dancing all over the place. Basically if you lower the car without any other modifications you will increase the initial understeer and make the transition to oversteer more sudden. It is of course one of the Murena's delights the way it gently and controlable slides when it's close to the limit. My aim is to retain the essential character of the car but to make it grip more. It was interesting to note that you are using 'wobble bolts' to fit 4x100 wheels, what size are you using and did you alter the offset? how does it affect the handling?

I am also interested to know what tyre options people are using and how changing the pressures affects the sharpness of the car?

I am guessing that stiffer shock absorbers will work well on the Murena as they will help to contain the roll axis within reasonable limits, any comments on this?

[krede]

Well... as for the "wobble Bolts" and new rims , I haven't gotten to actually fitting them yet. The reason for this is that the center hole in the rims are 70mm ,wheres the hub is 58mm , thus I have a mate at work making me some nylon adapters to get the wheels centered just right (Especially important when using wobble bolts)... but the git is taking his time !! 
So I'm using the original rims witch i rather like.. though they could use some care by now.
The rims I am switching to, are something in the line of "wolf race" of the of the 70'ies and 80'ies. I'm sticking to 14" and original tire size, as I'm not too keen on huge alloys on older cars, and I want the cushioning that the higher tire walls offer, as opposed to low profile ones.
I've test fitted a rim just to check  how they looked/fitted, and they don't seem to stray much from standard, so i reckon offset can only be off 5mm or so .. witch nearly makes no difference.

We discussed the topic of dampers and tires about a month ago, so maybe you want to check that out?
Anyway, Bridgestone potenza re720 are considered by many to be the best 14" tire available. Many Alfa romeo drivers reccomend them, and these are the ones I will going for.

Springs and dampers..(there are also a few topics about this in the forum)
Well.. If you are building a fast road car (NOT A RACER!!! ) Of cause you want  fully adjustable suspension front and rear.
Spax makes a kit ready off the shelf , but many consider this to be overpriced..
I agree, so I wrote "gaz" as I've used their dampers before and liked them, and they build me a set in about 3 weeks, at about 1/3 less then the spax kit.
At the moment I'm only using the rear units though, as I went for the setup with "helper springs" in the front... and now have second thoughts, after seeing the rating of those springs...I told the guys at "Gaz" that I wanted to retain the torsion bar, and they said "no problems".. Turns out the "helper springs" are perfectly capable of handling the front all by themselves.. 275 lbs a piece if I'm not mistaken (will have to check)   
I started out with the  rear dampers set at about half "stiffness" and must admit that I couldn't feel much difference in the way the rear behaved and felt in corners and on the road.
However after turning the adjuster nob to "KILL" , the rear is much firmer, and the car is much more stable at higher speeds, as the rear no longer "settles in" as much allowing the nose to rise and thus air to pass under it making the steering feel disturbingly light

Thus my bet is that stiffer dampers are a much better way to improve handling and roll, then harder springs.
But if you are gonna invest in new springs (and mine were 25 years old) , spend a little more and get the adjustable ones.   

   

[roy4matra]

Yesterday my Murena was parked next to my MR2 and I couldn't help but notice how much higher the Murena was off the ground. I have taken some measurments: the lower edge of the front spoiler is 22cm off the ground

That is too high.  The original drawings show a figure of 158mm but it appears to be wrong and I think they got the figures transposed, so 185mm is more like correct.

The reason I say that 158mm is wrong is that if you try to lower a standard Murena so that the front spoiler is only 158mm from the ground you will see it is much too low and the standard tyres would be buried up in the wheel arches!  Mine was not far above the 185mm I suspect is correct, when it was new, and since it was not level from one side to the other, I took the opportunity to adjust my front torsion bars to give that 185mm as well as level the car side to side.  At 185mm it looks fine.

There is another reason why manufacturers of road cars don't make the front spoiler too low.  It will ground and become damaged, or if the front is driven up to a pavement you want it to clear it, not smash into it!

Roy

[Anders Dinsen]

Yesterday my Murena was parked next to my MR2 and I couldn't help but notice how much higher the Murena was off the ground. I have taken some measurments: the lower edge of the front spoiler is 22cm off the ground

That is too high.  The original drawings show a figure of 158mm but it appears to be wrong and I think they got the figures transposed, so 185mm is more like correct.

The 158 mm number is probably the ground clearance overall, and the front spoiler underlip is clearly further off the ground than the lowest point of the car (which to me indicates that despite the aerodynamic styling, the front spoiler is not a downforce device, but a design element - in fact, since the underbody air flow is used to cool the engine and feed air to the carburettor(s), I think the engineers and the designer were careful not to set it too low).

The workshop manual states 122 mm as the ground clearance of the fully loaded Murena.

- Anders