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roll, plenty of it
rodgling - 15/4/15 at 01:35 PM

Me at Bedford, halfway through a fairly quick corner:



That can't be a normal/desirable amount of roll surely? Car is on R888s, no ARB.

[Edited on 15/4/15 by rodgling]

daveb666 - 15/4/15 at 01:36 PM

what is "fairly quick" ?

rodgling - 15/4/15 at 01:40 PM

Hmm, I reckon that one is around 70 mph. (For those that know Bedford, the left hander in the distance is the tightest hairpin on the GT circuit).

coozer - 15/4/15 at 01:41 PM

You need to see a similar pic at the same corner and speed without the passenger.

Putting someone in the passenger seat in my Striker really upset the handling.

mark chandler - 15/4/15 at 04:08 PM

That's road springs v track springs

Although scratch built I have progressed from 200lb springs up to 400lb on the front and 350lb on the rear, it now sits very flat on hard bends, damping is relatively light.

JimSpencer - 15/4/15 at 04:58 PM

Hi

Spent several years developing a Striker into a fairly successful hillclimb & sprint car - while remaining road legal.

I'd suggest you firstly fix the problem you identified in Post One.

"No ARB"

fixing Roll with stiffer springs is fundamentally the wrong solution - spring rate is determined by wheel frequency, an ARB is what it says on the tin - get one nailed on (an adjustable one at that).

Now - the next bit assumes you've got the setup right, corner weights in roughly the right place etc etc

Try it, preferably on a track you know well - DO adjust it - and see what happens to the way the car behaves.

Get a couple of pairs of springs and have a play - you can change them between sessions at most trackdays - again see what happens, don't forget to adjust the damper settings in line with the spring rate changes.

It's only be working your way through setup changes that you'll find the balance to suit your car and the way you drive it and like it to feel.

HTH

perksy - 15/4/15 at 08:38 PM

ARB


It would be different again without a passenger in.

Plus if you start making suspension changes in the future make sure you keep a book with the settings in, That way you know what you have done and will know what to do if you need to go back to an original setting etc.

Oddified - 16/4/15 at 09:00 AM

Every thing's a compromise depending on what you want to do with the car. I use my car on the road, track days and rwyb drag racing and they all require quite different set-ups to be 'right' (which of course is subjective any way!). Not wanting to crawl around underneath all the time changing things i just aim for reasonable at them all.

As said above, fit an arb 1st before going stiffer on the springs.

Ian

joneh - 16/4/15 at 10:13 AM

Easier method would be to get your passenger to lean in a bit more.

adithorp - 16/4/15 at 12:16 PM

quote:
Originally posted by joneh
Easier method would be to get your passenger to lean in a bit more.


In or out? to corner or car... all subjective.

jeffw - 16/4/15 at 12:49 PM

As a coincidence this turned up this morning from the US. Something similar to what Adi has fitted

From a Dallara Indycar it is an adjustable, blade ARB. Very cool




[Edited on 16/4/15 by jeffw]

Brian R - 16/4/15 at 12:52 PM

Also when fiddling with set up stuff do one adjustment at a time and try it.

Don't do a bunch of adjustments all at once. It may improve/worsen the handling but you won't know which alteration had the desired effect.

loggyboy - 16/4/15 at 12:59 PM

quote:
Originally posted by JimSpencer
fixing Roll with stiffer springs is fundamentally the wrong solution - spring rate is determined by wheel frequency, an ARB is what it says on the tin - get one nailed on (an adjustable one at that).

Thats assuming the spring rate has been set correctly, and not for comfort over performance, or just plain wrong!.
Before adding the weight/expense of an ARB, springs rates should be checked/corrected.

rodgling - 16/4/15 at 01:31 PM

quote:
Originally posted by loggyboy
quote:
Originally posted by JimSpencer
fixing Roll with stiffer springs is fundamentally the wrong solution - spring rate is determined by wheel frequency, an ARB is what it says on the tin - get one nailed on (an adjustable one at that).

Thats assuming the spring rate has been set correctly, and not for comfort over performance, or just plain wrong!.
Before adding the weight/expense of an ARB, springs rates should be checked/corrected.


This is my thinking - firstly get the springs in the right ballpark (because this is easy and cheap to do), clearly more is needed at the back. Then, if I find that the rear is too stiff for good traction (I suspect I will) then look at softening the springs and adding an ARB to get back to the right level of roll resistance.

Also once I know what springs/ARB are right for my car/usage I will look at getting some decent dampers which are valved appropriately, but I'm not there yet I think.

rodgling - 16/4/15 at 01:38 PM

Jeff: those are pretty smart. Not entirely sure what I'm looking at, or how they attach but they look shiny :-)

jeffw - 16/4/15 at 02:00 PM

Very shiny...lol

bi22le - 16/4/15 at 02:37 PM

I take they are going to be hacked apart to fit your car Jeff?

Also is that one of a pair that will be either end of a torsion bar? I cant see how that works other wise.

JimSpencer - 16/4/15 at 03:08 PM

quote:
Originally posted by loggyboy
quote:
Originally posted by JimSpencer
fixing Roll with stiffer springs is fundamentally the wrong solution - spring rate is determined by wheel frequency, an ARB is what it says on the tin - get one nailed on (an adjustable one at that).

Thats assuming the spring rate has been set correctly, and not for comfort over performance, or just plain wrong!.
Before adding the weight/expense of an ARB, springs rates should be checked/corrected.


I think you're correcting something I've not said is right

If you've calculated the wheel frequency - that will give you a 'rough' starting point for the springs - Yes?
I've not said the springs are right, obviously the basics must be done.

You then sort out your ARB - and away we go..

'Assuming' the rear's too soft because it's rolling is however a brave stab - could be, but could also be that the springs are about right and it's rolling across the front - and the chassis itself is stiff enough to transmit that though the car..

They're called Anti Roll Bars for a very good reason

jeffw - 16/4/15 at 03:14 PM

quote:
Originally posted by bi22le
I take they are going to be hacked apart to fit your car Jeff?

Also is that one of a pair that will be either end of a torsion bar? I cant see how that works other wise.


Just the one. Doesn't really make sense unless you see it in the flesh. Effectively the left hand bracket will be attached to each end of the inner suspenion rocker arm via rose joints/rods, one rocker on each end. The right hand side is bolted to the lower chassis. This means which suspension movement is transmitted vertically to the left hand mount. The whole assembly can pivot freely on the mount which attaches to the chassis so it only restricts roll and not suspension movement.

The blade is offset vertically to the left hand bracket which allows it to resists the roll of the car. The blade rotates through 90 deg so you can adjust the amount of roll resistance.

[Edited on 16/4/15 by jeffw]

Sam_68 - 16/4/15 at 05:45 PM

quote:
Originally posted by JimSpencer
If you've calculated the wheel frequency - that will give you a 'rough' starting point for the springs - Yes?


Ah, but what is the 'right' wheel frequency?


quote:
Originally posted by JimSpencer
They're called Anti Roll Bars for a very good reason


Like the roll centre is called the roll centre for a very good reason, you mean... despite the fact that it's not the point around which the car rolls?

You need to remember that conventional ARB's reduce grip, and because the ARB connects one side to the other, a bump at one wheel will try to pick the other up, degrading the contact between the wheel and the ground.

I would argue that, for these reasons, you're best off getting as much roll resistance as you can tolerate from the main road springs, and keeping ARB size to an absolute minimum.

In an ideal world, ARB's should be used to balance the diagonal weight transfer, more than to limit the body roll.

JimSpencer - 16/4/15 at 06:44 PM

Hi Sam

Yes, know and understand what you're saying - but we're also both aware of what we know works - we've been there done it and got that T shirt.
I would still say that for a road going, but track useable car, ARB's are the way to go.

However I''ll let folk find out for themselves - take the advice of somebody who's already made the mistake or not..

Sam_68 - 16/4/15 at 07:22 PM

quote:
Originally posted by JimSpencer...we're also both aware of what we know works


These days on the Hills it seems to be monoshock at the front (which works exactly the opposite way round to a conventional ARB for roll stiffness - a bump at one wheel pushes the other wheel down instead of trying to pick it up) and naff all roll stiffness at the rear?

Also worth mentioning is that if your road springs are soft enough to need ARB's to prop them up in corners, then there's a good chance that they're soft enough to be giving you too much dive and squat, too - and ARB's won't help you, there.

JimSpencer - 16/4/15 at 07:33 PM

Hi

There's advocates of both - quick but twitchy, or a tad slower but safer and hence you drive it harder..

rodgling - 17/4/15 at 08:30 AM

quote:
Originally posted by Sam_68
quote:
Originally posted by JimSpencer...we're also both aware of what we know works

Also worth mentioning is that if your road springs are soft enough to need ARB's to prop them up in corners, then there's a good chance that they're soft enough to be giving you too much dive and squat, too - and ARB's won't help you, there.


There is indeed quite a bit of movement under braking / acceleration which makes me think that spring rates are too low, regardless of whether an ARB is used.

My assumption is that the rear is too soft because it's rolling a lot more than the front (which is rolling a bit too much, but not quite so bad)... complicated business this.

Pretty sure the final outcome will be to take it to someone who knows what they are doing to pick spring rates and fit an ARB if needed, but thought I would take a stab at getting the springs closer to the ideal before I do that. If nothing else it's another data point to guide the final choice of springs etc.

Sam_68 - 17/4/15 at 02:14 PM

quote:
Originally posted by rodgling
My assumption is that the rear is too soft because it's rolling a lot more than the front ....


Unless you have a very floppy chassis, the opposite ends of the car don't roll independently of each other, as such. But the combination of inclined roll axis and different front:rear roll stiffnesses dictate the posture that the car adopts in a corner, which will be a combination of roll around the geometric roll axis and pitch.

This can do very odd things to the human inner ear, and it's not always easy to diagnose what's going on by 'feel' alone: it can depend, for instance, on how far your head is from the yaw axis of the car, which will certainly vary dramatically on a 'Seven' when you put someone in the passenger seat.

As an example, I used to run an old Mini, which most of the year had a reclined bucket seat that put my head well back beyond the yaw axis. Once a year, I used to refit the standard seat for the MOT (because the bucket lacked a locking mechanism), and the resultant move forward for my head made the car feel instantly and completely different, even though the real change in the car's balance would have been quite small.

... so you need to allow for the fact that whilst, certainly, a passenger will increase sprung mass and raise the CoG height (increasing roll), the longitudinal shift in CoG may also be doing strange things to your perception of how it's handling, because it's pivoting around a different vertical axis.

Which just comes back to what others have said about Sevens feeling a lot different with a passenger, of course, but I guess what I'm trying to say is that the change in feel isn't always for the obvious reasons.

scutter - 17/4/15 at 05:37 PM

A quick question, If you hadn't had seen the picture. Would you have been happy with the way the car handled and performed?

If it isn't broken and you a comfortable why change? or do you need to tinker

ATB Dan.

rodgling - 17/4/15 at 07:58 PM

quote:
Originally posted by scutter
A quick question, If you hadn't had seen the picture. Would you have been happy with the way the car handled and performed?

If it isn't broken and you a comfortable why change? or do you need to tinker

ATB Dan.


No, I wouldn't - it does have loads of grip but it does feel a bit wallow-y in the corners, and not super-responsive to turn-in. Also the rears rub the arches in bump - don't think this is actually upsetting the car but it's not doing the arches any good :-)

scutter - 18/4/15 at 08:57 AM

quote:
Originally posted by rodgling
quote:
Originally posted by scutter
A quick question, If you hadn't had seen the picture. Would you have been happy with the way the car handled and performed?

If it isn't broken and you a comfortable why change? or do you need to tinker

ATB Dan.


No, I wouldn't - it does have loads of grip but it does feel a bit wallow-y in the corners, and not super-responsive to turn-in. Also the rears rub the arches in bump - don't think this is actually upsetting the car but it's not doing the arches any good :-)


Then I'd have to agree with the proevious comments. Check your spring rates and once cahnge at a time increase the springs first to limit the roll, before an anti rollbar.

ATB Dan.