Suspension set up - R1 Fury

[Ian Kelly]

Hi Gents,

Can you advise on suspension set up? Had an entertaining high speed (80-90mph?) power understeer 'moment' at Llandow whilst accelerating out of a corner in 3rd.

Info -

R1 Fury, c460kg, plus me at c65kg. Front 45%, rear 55% with me in.
185/60 A048's on 13" CXR's, medium fronts, soft rears, 16psi front, 16.5psi rear. All ready for replacement.
1.2 degrees negative camber front, 0.7 negative rear camber.
Some toe in at the front, but not measured it accurately since doing camber and it changing. Slight toe in at rear.
110mm ride height front, 125mm rear.
180lb front springs, 130lb rears, AVO shocks, set fairly soft (3 clicks front, 4 rear). Didn't feel like it was rolling on track, despite the relatively soft springs.
Corner weighted (at home) the front end with me in the car, got the weights equal at c120kg. Didn't do the rear, scales don't go up far enough.

Is there anyting there that stands out as likely to wash the front end out under power? Obviously the tyres are, erm, tired, but that goes for front and rear. My thoughts are -

Medium compound on the front, soft on the rear?
Toe or camber?

I'm thinking of taking the car somewhere to have the geometry set up, so any suggestions as a baseline would be welcome. Or even better, if someone has the time and ability to assist, I'll put the money your way.

Thanks, Ian

[jeffw]

Having followed your car it does move around and roll more than mine felt like it was.

Rob Farley advised me to run 25mm difference front to back (obviously depends on where you measure from). 130 rear & 180 front is the standard CEC Fury road going setting, I was running 200 rear & 250 front with a front ARB. 250 on the front will be too much for a BEC but I would think you need more than 130 at the back.

[adithorp]

Just doing the weights on the front won't help much as it's the diagonal balance that matters more from the reading I did on it. I found the understeer (and bump-steer) much better after I took out most of the toe-in.

Not sure about the different compound tyres; aren't the stickier rears trying to push the fronts steight on? Your "moment" was towards the end of a session and I find my tyres start to go off (graining?) after about 20mins at that pace. It makes the car squirm about. Maybe your front suffer more than the backs.

I can't make up my mind on springs; I'm on 210F and 190R and think softer might be better but not sure. I think Jeffs ARB makes a big difference and he was on the power sooner than both of us. Think that might be added to the Modification list (it should get shorter but seems to be going the other way).

There's also a theory about the fury bonnet giving lift and causing high speed understeer as well as making the front feel light at speed. I also found plenty of stuff that says the Fury is prone to understeer.

If you fancy a run over Sat morning, I've nothing on at work and we could have a play with the tracking and corner weights.

adrian

[jeffw]

I think the biggest difference will be the spring rates...210R & 190F sounds much more like it than 130R & 180F. The understeer will come from the soft springing at the back (in the first instance). I would certainly invest in a new set of springs Ian.

[Ian Kelly]

Thanks guys,

Adrian - I'll call you later in the week to arrange, but I'd be up for coming over Saturday am, thanks a lot.

I was going to swap the 180's to the rear and try 225's up front, but I think I'll leave that until next year now. I'll not be getting much use out of the car once September is over I'd imagine. Unless we have a tropical winter...

Ian

[jeffw]

180R 200F would probable be about right. Set of springs wouldn't cost much and you change them over in a hour or so. Certainly make a big difference to your car.

[timhoverd]

180R 200F would probable be about right. Set of springs wouldn't cost much and you change them over in a hour or so. Certainly make a big difference to your car.

There seems to be a lot of guessing going on here. For reference, I use between 170 and 250 on the front of my CBR1000 powered RGB race car, depending on the circuit, and usually stick with 225s on the rear. That's got an ARB front and rear too which helps for easy adjustability. A front ARB usually makes a huge difference; I'd fit one.

However, just guessing the spring rate is not very useful. I'd strongly suggest you:

• Calculate the suspension frequencies. There's lots of books, such as Allan Staniforth's publications, that tell you how to do this. You do need to know the sprung weights at each corner though. if you know the corner weights you can guess the unsprung weights at 20kg a corner and work from there. If you calculate this you will at least know vaguely if you're in the right place.
• Measure how much of the suspension travel you're using. Do this by putting tiewrap around the damper rod and looking to see where it is after a lap or two. If it's buried in the bump stop then you're running out of travel anyway. if you are, then you should think about investing in some progressive rate bump stops which could well do the job all round.
• Perform a complete sweep of damper settings. To a rough approximation you should make the dampers stiffer and stiffer until you stop going faster
• Adjust the rake in the chassis. This is by far and away the most important adjustment you can make to a Fury chassis. You can change a car that understeers like a car with skids at the front to something that goes around corners on rails by getting the rake right. I'm amazed that no-one as mentioned this. Start by putting about 25mm of rake into the chassis (rear higher than front) and work from there. Just one turn on the rear spring platforms can transform a race car, although a predominantly road car will be harder to dislodge.
• Set the corner weights properly. Don't just try and get the fronts equal; set the cross-weights. (Again, see Staniforth.)
• Drive the car differently. There's always the chance that you've just got your foot buried too hard on the throttle. Any RWD car will understeer like a pig if you go into corners too fast. If the rear end's working very well you'll also get corner exit understeer with too much loud pedal. My race car's set up too be looser so at the rear so I can kill understeer with the throttle. However, on certain corners (Paddock Hill Bend at Brands, Luffield at Silverstone) then you just have to be gentle and wait for the chassis to catch up with you.

HTH. Note the italic bits: don't just guess, measure things..

Tim

[jeffw]

There seems to be a lot of guessing going on here

Always But we wait to be visited by those who know...

I did actually mention 25mm rake in my first post Tim...

[Ian Kelly]

Thanks Tim, very helpful. I'll do some googling tonight over a glass of wine!

I was able to provoke corner entry, mid corner, and corner exit under and oversteer almost at will. It was a real hoot, but instructive too, I was deliberately doing so just to learn how the car responded when 'provoked'!

However, it was whilst aiming to drive quickly but 'properly' that the corner exit understeer (then oversteer, then over correction!!) moment happened, and I didn't get any warning. Or rather, I wasn't able to detect any warning (still humbly admit to being a bit of a novice, hence the sticker on the back!).

One thing that did surprise me was how stable the car was when braking going into a bend, I had always imagined that it was a total no-no if you wanted to make decent progress, but I was able to brake hard, shift down, and start cornering whilst still coming off the brakes. Again, as a novice, if this is totally wrong, please point it out, but it felt quite good at the time!

Plenty of food for thought there Tim, thanks again. Will double check the rake first.

Ian

[adithorp]

Yes, we're all taught to brake in a strieght line and then turn in. We're also taught to brake in plenty of time. Nice and safe under normal circumstances.
Do it at full tilt and as you come off the brakes, the front end is going light as the load comes off. This reduces the grip on the front just as you try to turn in and you tend towards understeer.

What you discovered is trail braking . You brake later, stay on them as you turn in and feather off as you turn and then feed the power in from the apex. Faster, but come off the brakes or get on the power, too quick/suddenly and you'll get oversteer and spin out. It's particularly effective with cars that understeer.

Feel free to correct me if I'm wrong but I've had 2 different instuctors tell me the same thing.

adrian