Maintaining balance whilst upgrading ARB(s)
08-15-2013, 12:16 AM
#12
Thread Starter
Aha, replies from the people I was hoping to see (and I won't even start asking Si2k about oil)! Thanks guys, all appreciated. One thing I probably should have added to my 'influences' list is that I'm not too worried about laptime (driver improvement is definitely the way to go for that!). I do, however, enjoy getting the best out of the car for my given skill level, and being an engineer, I like tweaking the car and seeing the results (although clearly I still try and consider which tweaks to make very carefully!). It's all part of the hobby for me. I'm the same on my mountain bike, but I'm a better rider than driver! My car is also no longer a daily drive, I tend to do approx 5k miles per year in it, so it doesn't have to be quite so road focussed as it used to be (hence the uprated coilovers).
Should have included that info really. I have hardrace solid rear toe arms, so rear toe is lower than you might expect. Front: Camber -1°20', Castor max (virtually 7°), Toe 0°. Rear: Camber -2°10', Toe 0°20' (total). I seem to generate pretty even tyre wear at those values, with a mix of track and road driving. i wouldn't want to go much higher camber at the rear because I already notice that slides begin there when I'm on a more slippery surface. Maybe added camber at the front would counteract a stiffer ARB and balance out the breakaway when the conditions don't allow the tyre to get properly loaded up (low grip), thus making it more neutral/understeery in the wet? Or is my analysis totally wrong on that thought?!
I was unsure about going for such high spring rates (although most aftermarket coilovers seem to be up at those levels), but I'm pleasantly surprised that the springs/damping do not make the car unduly harsh (small, square edged impacts are handled better than stock, in fact), but 'road ripples' are felt more easily. I think the rebound must be fairly slow because the harshest 'bumps' are potholes, so i think the car is following the wheels into them rather than staying level as the wheel extends on its suspension. From a comfort point of view, I'd like to go a touch softer at the rear, but this would only add to the understeer bias that a stiffer front ARB would bring.
I looked at the Whiteline, but thought perhaps that big a change at one end of the car would upset the balance. Did it not induce some understeer?
I've been looking at the Eibach for front or both ARBs. I like the fact they're adjustable (something to fiddle with and reduces likelihood of buying the wrong rate!). The rear seems pretty stiff though, even on the minimum setting. I'd be very interested to hear how you find it. It does seem to be the US guys that are transfixed by rear articulation. Maybe it's a red herring for us in the UK. I've never had a problem (that I know of) with rear wheel lifting, and only the occasional skip of the inside wheel under power on hairpin exits. Likely to happen with a Torsen diff though, I'd expect? Without giving your settings away, MB, have you ever encountered such problems induced by an overly-stiff rear ARB? Is it something I'm unduly worrying about?
Edit: Just seen your post further down! Maybe I'll reduce the priority of that influence. Thinking more on it, I can understand why the Yanks seem to favour a stiffer rear coil if they're aiming to minimise ARB stiffness whilst maintaining balance. Creating my spreadsheet has helped me understand the interelation between these factors.
My other 'worry' (having suffered a large tank slapper at Oulton a couple of years ago) is increasing the undamped element of the overall spring at the rear that a stiffer rear ARB would inevitably bring.
I'm not interested (at this stage) in sticky tyres. Part of the fun of trackdays (for me) is progressively getting to the point of sliding and being able to control it. With sticky tyres, this woud just happen at a higher speed! I am becoming more comfortable with oversteer and I have tuition every time I visit a track. there's always something to be learned. Regarding geo, see comments above, I have kept my geo in check regularly. Sadly, this year has been low on trackdays due to having to spend on other things (I've just bought a garage round the corner. The S has a home!! 
), but next year I'll be doing multiple, I've promised myself. I've also bought this book to read! Ultimate Speed Secrets: The Complete Guide to High-Performance and Race Driving
I know. I'm just trying to minimise the changes I make and, more importantly, the number of parts I buy! A 00/01 front ARB is very much in my thinking as a 'first step'. New springs aren't too expensive (circa £150 for a full set IIRC), although I'm wondering if progressive springs are available (ones that aren't Spoon springs made for standard dampers and aren't lowering springs), as they might give a better comfort/stiffness balance.
Haha, this is the problem, trying to understand the practical world with so much subjectiveness and theory! Still, all good fun, and the discussion will stave off the spending for now!
Stiffer front anti roll bar transformed my 2006 S2000. It made a much bigger difference than the coilovers did to the handling of the car. I opted for the whiteline as its one of the stiffest bars you get before upgrading to one of the top of the line adjustable ARBS.
It weighs a ton thou which isn't ideal but i love it on track, i feel very little in the way of downsides on the road but on the track it pays dividends.
It weighs a ton thou which isn't ideal but i love it on track, i feel very little in the way of downsides on the road but on the track it pays dividends.
Yesterday after 7 weeks of waiting my Eibach adjustable rear anti bar arrived. I plan to put it on the softest setting so that i keep the front a fair bit stiffer than the rear. In hindsight i probably shouldn't of ordered it but i wanted to keep some balance. I will see how i get on with it and go from there.
In terms of what ive read on here all the racers in the US run very thick very strong front bars and little or no rear bar. The main reason being they are worried about the rear wheel lifting when cornering.
In terms of what ive read on here all the racers in the US run very thick very strong front bars and little or no rear bar. The main reason being they are worried about the rear wheel lifting when cornering.
Edit: Just seen your post further down! Maybe I'll reduce the priority of that influence. Thinking more on it, I can understand why the Yanks seem to favour a stiffer rear coil if they're aiming to minimise ARB stiffness whilst maintaining balance. Creating my spreadsheet has helped me understand the interelation between these factors.
My other 'worry' (having suffered a large tank slapper at Oulton a couple of years ago) is increasing the undamped element of the overall spring at the rear that a stiffer rear ARB would inevitably bring.
), but next year I'll be doing multiple, I've promised myself. I've also bought this book to read! Ultimate Speed Secrets: The Complete Guide to High-Performance and Race Driving The trouble is, the only way to find what works for you is to change one set of variables at a time. That's what the engineers end up doing in the final testing stage.
A s/h 00-01 front ARB would be a cheap and easy change; a CR rear might be more expensive. New springs more so...
A s/h 00-01 front ARB would be a cheap and easy change; a CR rear might be more expensive. New springs more so...
Haha, this is the problem, trying to understand the practical world with so much subjectiveness and theory! Still, all good fun, and the discussion will stave off the spending for now!
08-15-2013, 12:18 AM
#13
Member
That is probably the setup i'd go for on a road car, Lofty. 8kg (springs should alway be expressed in lbs/in imo!) which is about 550-600 lbs/in in probably as much as you would want on the road, but with a decent set of ARBs you will reduce roll, and with a decent damping range you should be able to make it compliant enough on the road, but stiff enough on track to prevent roll and dive.
I certainly wouldn't have a higher spring rate at the rear. Keep it even or slightly higher at the front.
Actually I posted a while ago all the S2000 arb stiffnesses, and you can get all you would need for road and track by mixing and matching OEM ones.
What you ahve to be careful with all this though, is tyres. All the more stiffening you do creates more load / work for the tyres. Most people use road tyres on track, and unless you are at least using a semi slick at the least, you may find you start ending up with a very drifty car.
Chassis stifness is often quite individual too - i've softened mine of loads over the last 2 years (car is very light though) and use very different rates to say Dixon, who likes his mega stiff and kart like.
I certainly wouldn't have a higher spring rate at the rear. Keep it even or slightly higher at the front.
Actually I posted a while ago all the S2000 arb stiffnesses, and you can get all you would need for road and track by mixing and matching OEM ones.
What you ahve to be careful with all this though, is tyres. All the more stiffening you do creates more load / work for the tyres. Most people use road tyres on track, and unless you are at least using a semi slick at the least, you may find you start ending up with a very drifty car.
Chassis stifness is often quite individual too - i've softened mine of loads over the last 2 years (car is very light though) and use very different rates to say Dixon, who likes his mega stiff and kart like.
08-15-2013, 12:24 AM
#14
Member
Originally Posted by MB' timestamp='1376516971' post='22724772
[quote name='markforrester99' timestamp='1376516374' post='22724748']
In terms of what ive read on here all the racers in the US run very thick very strong front bars and little or no rear bar. The main reason being they are worried about the rear wheel lifting when cornering.
In terms of what ive read on here all the racers in the US run very thick very strong front bars and little or no rear bar. The main reason being they are worried about the rear wheel lifting when cornering.
I assume you run both Rear and Front ARBS with no problems Mark? Do you mind if i ask what brand you use? Once ive fitted my rear one i wont be doing anything other than realignment and then keep the car as it is.
[/quote]
I can get front wheel lift on some track due to the ARB, but if the rear is cocking a wheel something isn't quite right with the setup.
I use a stiff adjustable front and an uprated rear. Not easy to compare though as my car is very light. I'd only uprate the rear ARB in the same ratio as the front. Do you know what stiffness your front one is and what the rear one is you plan to get?
08-15-2013, 01:35 AM
#17
Registered User
Toe deals with turn in not camber
The more camber you have, the less contact patch you have when under zero cornering load meaning less response than having a flat wheel.
Toe out will leap you into a corner and toe in will provide stability under braking
The more camber you have, the less contact patch you have when under zero cornering load meaning less response than having a flat wheel.
Toe out will leap you into a corner and toe in will provide stability under braking
08-15-2013, 01:43 AM
#18
Thread Starter
That is probably the setup i'd go for on a road car, Lofty. 8kg (springs should alway be expressed in lbs/in imo!) which is about 550-600 lbs/in in probably as much as you would want on the road, but with a decent set of ARBs you will reduce roll, and with a decent damping range you should be able to make it compliant enough on the road, but stiff enough on track to prevent roll and dive.I certainly wouldn't have a higher spring rate at the rear. Keep it even or slightly higher at the front.
Actually I posted a while ago all the S2000 arb stiffnesses, and you can get all you would need for road and track by mixing and matching OEM ones.What you ahve to be careful with all this though, is tyres. All the more stiffening you do creates more load / work for the tyres. Most people use road tyres on track, and unless you are at least using a semi slick at the least, you may find you start ending up with a very drifty car.
Chassis stifness is often quite individual too - i've softened mine of loads over the last 2 years (car is very light though) and use very different rates to say Dixon, who likes his mega stiff and kart like.
Actually I posted a while ago all the S2000 arb stiffnesses, and you can get all you would need for road and track by mixing and matching OEM ones.What you ahve to be careful with all this though, is tyres. All the more stiffening you do creates more load / work for the tyres. Most people use road tyres on track, and unless you are at least using a semi slick at the least, you may find you start ending up with a very drifty car.
Chassis stifness is often quite individual too - i've softened mine of loads over the last 2 years (car is very light though) and use very different rates to say Dixon, who likes his mega stiff and kart like.
My current fron ARB (according to the data from the US thread) is 300lb/in, with the rear at 311. Given the bang per buck, I'm erring towards a 00-01 front ARB (393lb/in) to start with, maybe a reduction to 8kg/mm rear springs (yeh, i'm comfortable with metric and imperial!
) and if I find it too understeery, a CR, 02-03 or Eibach rear ARB. Interestingly, due to the different motion ratios between front and rear suspension, softening the spring rates evenly all round actually shifts the balance to be stiffer at the front. so a 10kg/10kg car will be more oversteery than an 8kg/8kg car. So a softer sprung car will need a stiffer rear ARB (compared to the front) to maintain the same balance, theoretically. So I
reckon my changes should be made in 3 stages:
- 00-01 front ARB (393 instead of 300lb/in) - Overall stiffness balance changes from 54.6% Front, 45.5% Rear to 56.4/43.6 (more understeer).
- If balance feels ok after step 1, and I'm able to wind the damping off a decent amount on track, reduce springs from 10kg to 8kg - Overall stiffness balance to 57/43 (more understeer). If understeery after step 1, or I can't wind off the damping without too much roll, skip straight to 3.
- If understeery after step 1 or 2, add 02-03 rear ARB (396 instead of 311lb/in) - Overall stiffness balance to 55.2/44.8 (10kg springs) 55.5/45.5 (8kg
springs).
2000-2001 - 52/48
2002-2003 - 50.1/49.9
2004-2005 - 54.8/45.2
2006-2007 - 55.4/44.6
2008-2009 - 56.5/43.5
CR - 58.4/41.6
So, based on these values, I seem to playing around in an area of balance akin to 04-09 OEM values, but with overall stiffness exceeding the CR values. I just remembered that rear tyre size on the CR is 255, so should make it even more understeery. Yet reviews say it handles better?!
Thoughts?
08-15-2013, 01:48 AM
#20
Thread Starter
Having just seen the discussion on geometry, that is another thing to add to the equation. If step one feels good but is only a touch understeery, added camber could be a good way to go. This might also provide 'safety' in the wet, when the tyre can't generate enough load to get a big enough contact patch to generate grip (I notice this on the rear end in the wet, doing it at the front might even it out).