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Single Seater Ride Heights
scootz - 20/2/13 at 11:57 AM

The normal ride height on a single seater is 40mm. Not much use on our roads.

I can get another 20mm ride height through choosing the right tyres. Alas, 60mm is still a little short of where I want to be.

So, my question to anyone who has dabbled with modern single-seaters is... how much (sensible) height adjustment would there be in the front end of a monoshock equipped car? Could I sneak another 20mm without completely destroying the handlng?

ceebmoj - 20/2/13 at 12:18 PM

Is this for the trike?

scootz - 20/2/13 at 12:23 PM

Yup

designer - 20/2/13 at 12:47 PM

For a monoshock the easiest way is to lengthen the push/pull rods.

Benzo - 20/2/13 at 12:55 PM

quote:
Originally posted by designer
For a monoshock the easiest way is to lengthen the push/pull rods.


when we had our Judd Pilbeam with inboard suspension, all height adjustments where done through the pushrods, not the platforms.

Talon Motorsport - 20/2/13 at 01:06 PM

If you can not fit landrover tyres and you come to the point that the suspension angles are getting silly why not make some Z shaped wishbones? Then you can get as much ride as you want then with in reason.

scootz - 20/2/13 at 01:06 PM

Cheers guys. That makes sense!

russbost - 20/2/13 at 01:25 PM

You can obviously gain some movement by lengthening the pushrods, but you may find that the suspension joints themselves run out of movement - this was certainly the problem I had when doing something similar, finished up having to modify wishbones to ensure everything worked at sensible angles

Theshed - 20/2/13 at 03:16 PM

Unless you move the pick up points any alteration in ride height will alter the geometry. I discovered that when I tried to gain ride height by changing tyres. Extending the pushrods to give an extra 20mm is a big adjustment and the wishbones would be on a very different arc.

scootz - 20/2/13 at 04:10 PM

quote:
Originally posted by Theshed
Unless you move the pick up points any alteration in ride height will alter the geometry. I discovered that when I tried to gain ride height by changing tyres.


Surely using larger diameter tyres wouldn't affect the geometry???

v8kid - 20/2/13 at 05:02 PM

quote:
Originally posted by scootz
quote:
Originally posted by Theshed
Unless you move the pick up points any alteration in ride height will alter the geometry. I discovered that when I tried to gain ride height by changing tyres.


Surely using larger diameter tyres wouldn't affect the geometry???


Think it would.

Think of the geometry when you construct the roll center diagram. The point where they intersect the road has just been shifted 20mm downwards.

Anyhow you have altered the balance by converting to a trike and I presume you will be upping the front roll stiffness since there will be no help from the rear so it should not move much anyhow.

Was it Chapman who said you could make any suspension geometry great as long as the springs were so stiff it never moved?

Cheers!

Sam_68 - 20/2/13 at 05:03 PM

quote:
Originally posted by scootz
quote:
Originally posted by Theshed
Unless you move the pick up points any alteration in ride height will alter the geometry. I discovered that when I tried to gain ride height by changing tyres.


Surely using larger diameter tyres wouldn't affect the geometry???


It will potentially alter the roll centres (the RC is defined by projecting lines from the wishbones until they intersect, then drawing a line back to the tyre contact patch... with bigger tyres, the wishbone angles remain the same, but the tyre contact patch moves downward relative to the wishbones).

It will also change the king pin offset (scrub radius) and caster trail dimension on the ground.

Since you're also going to be using completely different tyre construction, weight distribution and dynamics (3 vs. 4 wheels for a start!) from those the geometry was designed for, these may or may not be catastrophic.

Sam_68 - 20/2/13 at 05:06 PM

quote:
Originally posted by v8kid
Was it Chapman who said you could make any suspension geometry great as long as the springs were so stiff it never moved?


He's OK on that score, at least - it's a monoshock set-up, so the total roll compliance will be measured in millimetres!

phelpsa - 20/2/13 at 05:08 PM

The problem will be that single seater suspension is designed to operate within very small adjustment ranges. So you'll find problems like massively non-linear motion ratios and binding bearings start to come into play.

Sam_68 - 20/2/13 at 05:25 PM

quote:
Originally posted by phelpsa
The problem will be that single seater suspension is designed to operate within very small adjustment ranges. So you'll find problems like massively non-linear motion ratios and binding bearings start to come into play.


As I understand it, the suggestion at the moment is simply to increase the rolling diameter of the tyres, so the motion ratios should not be affected?

You will certainly need to ensure that the total range of suspension movement is not substantially increased, otherwise, yes, not only will the motion ratios move out of their designed envelope, but you'll almost certainly find that the suspension will run out of movement somewhere or other and bind. Joking aside, you'll find that the Dallara monoshock has very limited roll compliance, whatever you do. I assume you have a copy of the Dallara manual for the car, which gives the damper open and closed dimensions (which in turn control maximum bump and droop movement, of course)?

Slightly different problem, but I know from the bitter experience of being asked to design an all-pushrod actuated suspension for a road car because it was 'sexy' that what works well for a single seater with a total suspension movement of 30mm doesn't work out quite so easily for a road car with a total range of 120mm movement, particularly if you want to maintain sensible motion ratios on your dampers!

Sam_68 - 20/2/13 at 05:43 PM

quote:
Originally posted by Benzo
quote:
Originally posted by designer
For a monoshock the easiest way is to lengthen the push/pull rods.


when we had our Judd Pilbeam with inboard suspension, all height adjustments where done through the pushrods, not the platforms.


Another quirk of monoshock suspension is that standard practice is to adjust the ride height on the spring platform, not the pushrods, the reasons for which will hopefully be obvious - you need to keep the pushrod lengths exactly equal, otherwise the roll shuttle will be off-centre and you'll end up with asymmetric roll compliance.

scootz - 20/2/13 at 06:36 PM

Thanks for the replies.

I think I've said it elsewhere... I'm not looking for razor sharp handling. I just want the trike to look right, have Gucci components and to not try and kill me on every bend!

Just an interesting concepty-typy-thingy!

scootz - 20/2/13 at 06:37 PM

PS - yes, I downloaded a copy of the Dallara manual.

phelpsa - 20/2/13 at 08:37 PM

quote:
Originally posted by Sam_68
quote:
Originally posted by phelpsa
The problem will be that single seater suspension is designed to operate within very small adjustment ranges. So you'll find problems like massively non-linear motion ratios and binding bearings start to come into play.


As I understand it, the suggestion at the moment is simply to increase the rolling diameter of the tyres, so the motion ratios should not be affected?


I believe scootz is asking how to gain more, even after changing the tyre diameter.