I had the car racing today, it went real good too but I would like to reduce lift off oversteer a bit. While slowing through a chicane it had the tendency to oversteer, yes a FWD characteristic but I would like to work on reducing it.
I have the suspension set to soft all around. Fronts have 6kg/mm springs, rear has 4kg/mm. Front and rear sway bars are both standard current (24mm F, 12mm R). Tyres are toyo r888. Weight distribution is about 630kg front and 300kg rear. No aerodynamics. Brake bias is wound all the way front with adjustment and I dont seem to be getting the rear lock up under braking, certainly not under the amount of braking required to get this oversteer.
Its not dangerous oversteer but I feel I could go faster if I knew that it was unlikely to do so.
I'm not looking for a magic answer for fixing it, what I would like is some advice from those who know these sorts of setup and can recommend which way I start heading to find improvements with regards to sway bars, damper settings, fuel loading, aerodynamics etc.
snoopy221,
Oct 14, 6:57pm
Need your front and rear camber and castor and toe figures. And what tyre pressures/wheel ofset/inset profile diameter width. Bigger rear sway bar WILL help though-but initialy why not shove a tied down sack of sand up it's gunga! Ya moit be pleasantly suprised.
fordcrzy,
Oct 14, 6:59pm
6 kg is way too soft for a fwd. You need to fix the weight transfer.sways wont help. Go for some 10 or 12 kg front springs. Dont get a heavier rear bar, that will just make it worse
morrisman1,
Oct 14, 7:04pm
Front: Camber -2.23 Caster 2.28 Toe-in 3.2mm total
Rear: Camber -1.31 Toe-in 1.9mm total
We ran 32psi cold all around on 195/50r15 tyres. 6" rim with +38 offset. 15mm hub adapter/spacer on front to clear brakes.
snoopy221,
Oct 14, 7:11pm
Agree re light springs however with those figures. F F Seven it's but up with the same spacers as the front. Personaly i'd be on 14's about 45+ ofsett 195/60 and 0.1 neg camber front 0.00 rear 4.5 castor front 0.5 castor rear and front toe in 1.00 mm rear 0.5 Also 195/50 on a SIX INCH! no wonder ya 32 coldtyre flex and diferring tracks with spacers ain't gunna be fun.
flashgordon_nz,
Oct 14, 8:11pm
firstly, dont hook your thumb in like that around the inside of the steering wheel. if it does kick on you, you will bust your thumb. 2nd, i run a 205/50r15 on a 6 inch rim. the toyos and dunlops dont really flex too much in the sidewall, ideal is a 195 on a 6 1/2, and the 205 on a 7 inch rim, but its not a huge issue at our level of the sport. 32 psi is probably ok, with short sprints, they may increase to 34/35 and on a cold surface, that should still work. Im picking to riase the front up, maybe a bit, while trying to make it stiffer would be a direction to start in, but get used to a FWD rear having a mind of its own. or try a little bit of tow out on the rear. 2mm!
clark20,
Oct 14, 10:20pm
When I wanted the back to come out, I increased the rear rebound on the shocks, can you reduce it!
pollymay,
Oct 14, 10:36pm
Give it 300hp like my old prelude and turn it into understeer everywhere. Problem solved
snoopy221,
Oct 14, 10:38pm
When ya got a crab-ya got a crab. ALL understter/oversteer sway bar/tyre pressure etc. calcs. DO NOT DEAL WITH 15 MILL SPACERS ON FRONT ONLY.
bill-robinson,
Oct 15, 6:45am
what type of brake bias are you using! valveor pedal type!
morrisman1,
Oct 15, 7:36am
valve type, willwood screw adjustment one. Snoopy, cool ya jets mate, the rear hubs got moved out 10mm a side so at most there is 10mm total track difference between ends of the car.
The shocks are BC gold, I don't have rebound adjustment on them only compression.
In my experience that type of valve will only limit the amount of pressure getting to the rear brakes, not vary the fr/r balance. You need to change you master cylinder ratio IMO
morrisman1,
Oct 15, 7:49am
You are the first ive ever heard to tell me that camber is not good lol. even toyo say on the tyre specs to run between -3 and -5 degrees camber. If I put zero camber on the front Ill eat the tyres pronto and the contact patch will halve and only work off the outside edge. There is probably a good reason that ive never seen a race car which doesn't have negative camber. Caster is not adjustable front or rear. Kits are are available for front but I fail to see how caster would affect the rear but share some of your wisdom.
195 on a 6" rim is about right, the sidewalls are nice and straight and it doesn't look out of the ordinary.
Before I go swapping springs around Id like to try work with what I have and see if changing damper settings helps, the kitty is empty and there is no room for getting new bits at the moment so its a matter of tuning what i have.
supernova2,
Oct 15, 8:00am
I have a bit of experience with race car suspension design many years ago.I also think your front springs are too soft.
morrisman1,
Oct 15, 8:31am
Ok. Ill make some enquiries into what should be put on there.
kcf,
Oct 15, 5:03pm
If it's an N14 Gti lordy me they're heavy on the nose . though I do envy you as I could never get mine to oversteer other than by running semi's on the front and road rubber on the back.
morrisman1,
Oct 15, 5:22pm
Its an X1R sedan but with SR running gear. I've taken as much weight out of the front as I can but there is still some which could come out. Namely the bumper frame and the cast headers.
I had a measure up of the car today and it was sitting quite high at the rear, odd because the guard to wheel spacings were the same. So Ive dropped the rear by about 40mm and that has brought the sill panel back level front to back. I would assume that it was contributing to the oversteer. Ill see how that goes, along with the sway bar when it arrives.
It was a bit deceiving because I had set the ride height off the guard spacings rather than measuring the chassis.
mantagsi,
Oct 15, 5:30pm
I know nothing but the absolute basics about suspension, but I just wanted to say 'cool vid!' and wow that little sentra gets along well. Have fun and stay safe :D
chebry,
Oct 15, 5:37pm
Lifting and lowering the rear also adjusts the castor/kingpin inclination.
fordcrzy,
Oct 15, 6:30pm
you still need stiffer front springs
supernova2,
Oct 15, 8:54pm
Have you checked the corner weights by any chance!
flashgordon_nz,
Oct 15, 9:02pm
so, you have dropped the rear today. just try it. One change at a time. maybe a practice run where you can, but make one change at a time. The N14 are bugga's of things to get to behave, and there is little data out there of "what works", and what work for you, may not work for me.
flashgordon_nz,
Oct 15, 9:06pm
oh, and Bill-robinson has touched on something too. There is a ratio out there that works out what "actually' works. We have recently experienced similar on a car with bigger brakes, but turns out was running standard master cylinder. the brakes just never could perform how they were expected to. a quick tear-down 2 weeks ago to chase a seeping rear caliper revealed that the pressure applied to the piston merely moved it against the rotor, as opposed to clamping it tight in an effort to stop. putting the rears back to rebuilt standard, and a quick blat up the road proved a huge step forward in that fact we could get it to stop, quickly!
morrisman1,
Oct 15, 9:14pm
I havn't weighed it since the cage went in but before cage it was 630/300 with driver. I wanna head out there fairly shortly and do some more testing, see what its like and have a play with damper settings.
I gave chris a ring today and he reckoned I should sort out the rear sway bar and rear ride height first before worrying further. He said the front springs were not necessarily far off and to get the other stuff sorted first before worrying about them.
Brakes remember were all rebuilt, each corner done so they are working perfectly, no troubles with them
flashgordon_nz,
Oct 15, 9:40pm
the bias valve does merely cut pressure to the rears. however, how far do you go! tilton adjustable pedal box! the car isnt near that level. however, i would examine the calculations for the brakes. its not a biggy, but yes, we have found it causes problems down the line.
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