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16 Nov 2014, 11:08 (Ref:3475392) | #1 | |
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Join Date: Apr 2012
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FWD set-up
Hi,
I've started helping a friend who races a FWD saloon, he bought the car mid-season and doesn't feel he's got to grips with it (we both come from a RWD background). The car:- 800kg, 205 section slicks, front and rear anti roll bars, 600 lb springs front and rear, 2.5 deg front camber, 7 deg castor, parallel toe front and rear, front and rear shocks are a bit of an unknown (strut inserts at the front). Tyres 28F 24R. The observation is that is generally not very responsive, turn-in being a little vague. Being light, the rears take a few laps to warm up so it oversteers on cold tyres but not so much when up to temperature. It sounds to me like it's a 'feel' thing. Thoughts would be: A few mm of toe out to help the turn in? A little stiffer all round? (seems a little low on springs perhaps?) Look into the dampers over the winter Any thoughts please? Also, does anyone know the sort of set up touring cars run? Thanks for reading! |
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16 Nov 2014, 19:46 (Ref:3475528) | #2 | |
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Join Date: May 2009
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I would start by adding a little more bar on the rear, or bumping up the spring rate in the rear. I wouldn't go too high immediately, but perhaps up to 700 or 800 lb and see how the car responds.
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17 Nov 2014, 00:08 (Ref:3475612) | #3 | ||
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Join Date: Nov 2006
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Set the front track to toe out, hopefully it has adjustable shocks and ARBs !
Do a track/test day and only adjust one thing at a time but make big changes so you can feel the difference straight away. It's always easier to "unstick" one end of a car than make it stick so it's always a compromise. Try and find out what others in similar cars are using if they are quicker ! Basically if you want it to oversteer tighten the rear or slacken the front by the above {and spring rates} if you want understeer slacken the rear and tighten the front. It all depends on the driver as not everybody likes the way that some cars handle for others and yet can put in the same lap times, also its difficult to make a car handle perfectly on slow and fast corners without having a sophisticated suspension set up so it's best to make it better for the faster ones ! |
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Balls of steel (knob of butter) They're Asking For Larkins. ( Proper beer) not you're Eurofizz crap. Hace más calor en España. Me han conocido a hablar un montón cojones! Send any cheques and cash to PO box 1 Lagos Nigeria Africa ! |
20 Nov 2014, 11:31 (Ref:3476890) | #4 | |
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Been there done that . After umpteen years competing in RWD , I went to a FWD [ in International tarmac rallies ] . It was a culture shock , & took a long time before I could get it to do anything near what I wanted .
So a few thoughts . With what you have , it would usually want a lot softer compound tyres on the rear than on the front . As Gordon said , testing , & only changing 1 thing at a time is very important . A tyre pyrometer is a very good idea for checking across the tyre surface to see if it working correctly , that will give a good idea on correct pressures , camber & if the suspension is set anywhere near correct . From your settings I would personally go in the direction of trying [ 1 thing at a time ] softening [ disconnecting ] the front sway bar to see if helps for more positive steering . Checking front tyre temps across the width of the tread to check front camber , [ 2 1/2 deg might be too much ] . Reducing the castor , 7 deg does sound a lot & might be the reason the front feels vague . Those & trying slight changes to toe in - toe out etc will all take a lot of testing , but it could make things feel nicer & give more confidence in the handling . |
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21 Nov 2014, 21:46 (Ref:3477389) | #5 | ||
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Join Date: Apr 2006
Posts: 1,920
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You need to tell us about your diff set up
Done a lot of FWD racing over 25 years, where you are starting isn't actually that bad, castor is in the ball park, most people don't have enough, but keeping the tyre upright in brake and acceleration is important for your lap time, then getting camber gain while turning, hopefully you are not losing it on bump... I think you probably have too much front spring relative to the rear, although I am presuming we are talking wheel rate (or Mac strut = 1:1 or close to it) Exactly like everyone else here go for more rear roll stiffness than front. Front toe is always going to be out... but rear can go either way One little pearl I can give you: With FWD: Rear spring is more important than the front and the front shock is more important than the rear |
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25 Nov 2014, 22:53 (Ref:3478715) | #6 | ||
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I always found it best to start off with a fair bit of castor on a new project and slowly decrease it when you feel you could go faster (and your arms start to ache too much) !
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Balls of steel (knob of butter) They're Asking For Larkins. ( Proper beer) not you're Eurofizz crap. Hace más calor en España. Me han conocido a hablar un montón cojones! Send any cheques and cash to PO box 1 Lagos Nigeria Africa ! |
26 Nov 2014, 17:45 (Ref:3478962) | #7 | ||
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Front springs sound too hard to me, try 400 or 450. Bit of toe out on the front helps turn in.
I believe the general idea it to make the rear of the car slightly "loose" and to get it to "rotate" through the corner, this will reduce understeer. You can get to the point that once the car is rotating you can take off all steering lock and simply floor it through the car using all the available traction for acceleration rather than acceleration and steering. You can fine tune this affect as well by increasing rear tyre pressures, try 30 rear and 22 front. Some FWD racers run 40+ on the rear! As before change one thing at a time, but above all make sure the driver slowly adapts to the handling required. A nervous car which wants to step out at the rear at 100 mph through the craner curves can be "exciting" to say the least! If you are taking out the edges of the front tyres go for even more negative camber! As said by others, tyre temps are key to understanding how much camber your car needs |
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CSCC TinTops #7 |
30 Nov 2014, 19:09 (Ref:3480377) | #8 | ||
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1or 2 mm tow out on back 1' neg
More spring and roll bar and on rear will help |
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So long and thanks for all the fish. |
9 Dec 2014, 03:35 (Ref:3483308) | #9 | ||
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Join Date: Jun 1999
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As above, change one thing at a time is good advice.
Front spring rate seems a little high, perhaps 400lb or 500lb? I see your rear cold pressures are 4lb lower than the front. I don't think that's a very good idea, they should be at least as high as the front. Run as much caster as your arms can manage. Be careful with toe, too much is too much! |
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10 Dec 2014, 19:46 (Ref:3483792) | #10 | ||
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Join Date: Jun 2007
Posts: 419
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The FWD concept of tracking is as the wheels transfer power, they are trying to drag themselves forwards; and thus from Toe Out, move towards Neutral to Toe In, under power. We always used to set very grunty Cooper S race cars to More Toe Out than standard; even with beefed up radius arms and almost solid mountings. Ergo: set up the car to toe in and traction torque will induce even greater Toe In and scrub the tyres and reduce the effective contact patch. And, BTW: Feliz Navidad y Feliz Año Nuevo ! |
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12 Dec 2014, 10:35 (Ref:3484349) | #11 | |
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I see everyone saying change one thing at a time, he will be an old age pensioner before he finishes.
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12 Dec 2014, 20:37 (Ref:3484497) | #12 | ||
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Provided he is in the ball park first
Mind you, doesn't it get a bit annoying when some one asks on question then never comes back to comment or acknowledge, and even report on haow they went |
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Contrary to popular opinion, I do have mechanical sympathy, I always feel sorry for the cars I drive. |
14 Dec 2014, 19:21 (Ref:3485005) | #13 | |
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Join Date: Apr 2012
Posts: 6
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Apologies Notso Swift, I've been away for the last two weeks without adequate internet access.
Thanks everyone for the responses, I'll have a wade through them and see how many of the suggestions we can try during the closed season. The owner doesn't live too far away from Blyton so there are at least opportunities for trying some of the set up changes suggested. From what I've seen of the car, there is a fair amount of adjustability there with anti roll bars and coilovers, though the dampers themselves have no adjustability (rear) and are probably in need of a re-build (front and rear). I will feed back when we next run the car. I mentioned the touring car set up as a matter of interest, just wondering if anyone had an insight as to what sort of set up they run? |
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21 Dec 2014, 21:43 (Ref:3486987) | #14 | ||
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Join Date: Jan 2014
Posts: 54
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Sooo, this a cold running scenario mainly? I've just finished a season of Hill Climbing in a Proton Satria GTi and I had your problems. I raised the front psi, stayed the same on the front shocks and disconnected the rear bar which made the inner rear stay on the ground rather hike a wheel. Disconnecting the rear bar made the biggest change. Corners where I had spun I now go thru flat and I change up a gear (3rd to 4th) just before the corner and make sure the car is well balanced before Entry. You do run a Splitter? Big help in FWD having a Splitter and Canards. Oh and I finished 4th in Class with only Track cars ahead (19 car field) and I was on Road Tyres, Michelin PS3 (2nd twice in the wet). Rear wheel Alignment is exactly the same as a WRX = ACES....... Sorted the handling and driving over two meetings and went 9 seconds faster from start of season to final meet.
Last edited by Trikes; 21 Dec 2014 at 21:49. |
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21 Dec 2014, 21:55 (Ref:3486991) | #15 | ||
Rookie
Join Date: Jan 2014
Posts: 54
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And where are your Corner weights at? Mine is 48& front and 52% rear. Nice balance (Factory) which gets even better when the tyres come up to temp - yes PS3 need temp in them to get their best but their better than most semi's in the wet and cold.
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