jimbo or someone help please

[vpulsar]

I'm not expert with things susp related I'll leave that to Jimbo he's the kiddy but it sounds to me like the unloaded front wheel is some how changing its angle when you make this particular maneuver so it starts squealing away like a bastard can't help with a fix because I don't really understand the in's and outs of susp its a black art.

good luck bobby.


Rob

 

[pulsarboby]

yeah cheers rob, if the diff dont work then il measure the steering acremen or whatever its called as that seems like the only other logical thing it could be.

btw
thanks for the other replies and help guys, ive already checked all bearings, driveshafts etc and they are fine, i dont know why but ive a sneaky suspicion its the front diff so will know later today and post up results just incase someone else ever has this kind of problem

 

[vpulsar]

I don't understand how the diff would make the wheel squeal/scrub but like I said I'm an idiot when it comes to the real technical stuff give me some spanners and point me the direction and I'll change it but diagnostic stuff is beyond my tiny brain lol. I could see how the diff would effect the wheels rotation but not the angle it is at any given moment. Its one of the kind of problems that really gets you scratching your head doesn't it lol.


Rob

 

[campbellju]

There might be an issue with the centring of your steering rack but if you are feeling the same problem on circuit at 100mph then it is likely a different issue. At 100mph I expect you only have a 1deg of steering angle. Your total toe is probably -0.1degs and the ackermann effect will be in a similar range of difference between left and right wheels. On a 30mph roundabout (10m radius) the effect will be more like 1deg so could give you squealing tyres etc. If you've changed you're front track too then the fixed ackermann angle would be incorrect anyway.

Corner weighting is good to establish a baseline but when you turn a corner you'll find 80% of your load (not weight) goes to the outside wheel. Load transfer when cornering by playing with springs, ARB's and dampers will have a much greater effect.

You'll know this but the more extreme your track setup, the worse the car will feel at normal speeds on the road. Comparing your camber to a standardish car, you're running the right amount for a 100mph corner but too much for very tight roundabouts and corners. But if you're running -2degs camber and less than -0.1deg toe then I would look elsewhere.

I have found that whenever I've made major changes to my setup, the dampers, ARB and geometry needs to be fine tuned to get the balance back again. Ultimately I've ended up with a better compromise but at first it is often worse.

The dampers have normally been the key for me.

It would help though to know what your alignment and ride height settings are. It might be that there is a mismatch in castor or KPI that isn't normally adjusted but would point towards a chassis misalignment?

 

[pulsarboby]

yeah too right.
the diff i have fitted and had fitted before were just stock viscous diffs
now from my understanding of how these work (probably wrong) is by the thickening of the viscous fluid when cornering so when one wheel starts to slip the fluid then aids traction to the slipping wheel hence the 4wd when needed.

so if the fluids cooked in the diff the wheels could both end up either freewheeling or not locking up at the correct time as they should do and the o/s wheel 'say on a roundabout' should be turning faster than the n/s 'outer' wheel
so in a nutshell if theres a diff prob the inner wheel could possibly be dragging its way round and turning at incorrect speed

im about to test drive it in a minute but its pissing down here so not really gonna be able to test it properly untill its dry

ive now checked the steering geometry 'ackremen or whatever lol' and even though done in a crude manner it appears to be spot on at different points throughout the steering lock so looks like im gonna have to rule that out

need some dry roundabouts now!

 

[pulsarboby]

yep is very true jim what your saying but surely the car should go round right handers equally s wel as lefthanders on the setting that it has got now:?
if it was squealing round lefthanders the same then i would not think there was a problem
i took the car on a fast right drawn out bend that i know of on the road and i needed both lanes to allow for understeer/and squeal coming off the apex (almost clumping the n/s kerb:shock
now if that same bend would have been on track it would have been taken a lot quicker still which no doubt would have seen me kissing an armco barrier


ive not got a printout jim just what hes wrote on the invoice
being
2 degree neg camber on front (from 3 neg)
adjust front tracking to 2mm toe out (from parallel)
zero preload at normal ride height

rear track and camber measured and set to 2mm toe in
rear camber 1.5 deg neg

cross weight r-f / l-r 51.0%
l-f =370 r-f =419
l-r =221 r-r =244


after having just read what he has done, is it normal to have toe in on rear yet toe out on the front?
would this not cause a confliction between front and rear alignment?

sorry to be a pain in the ass jimbo but dont know anyone else other than you who understands steering geometry like you do

 

[campbellju]

cross weights I have from another owner ages ago are:

with driver
lf 395 rf 417
lr 209 rr 238

without driver
lf 382 rf 390
lr 188 rr 210

These aren't a huge difference from yours assuming yours also include the driver.

Do the spring perches look in similar locations on each side? Count the number of turns on the spring perch.

2mm toe out on the front doesn't surprise me for a track car, 2mm toe in on the rear is more like a rwd setup where you want to improve stability under power. It depends what you want. On the "kochmobile" I vary between 1mm and 4mm rear toe in, 1mm gives could turn in, 4mm enables easy drifting. For the R I've been in the range +1 to -1mm toe to get the balance I want.

As a more extreme comparison, if you've seen Ev's hill climbs, after much head scratching he ended up with around 3mm toe out at the rear to get the car to turn in the tight hairpins.

Your rear toe might be causing handling issues but wouldn't easily explain the squealing and the fact its only on left handers.

Don't touch your toe yet, what suspension are your running and what are your damper settings.

Just ruling things out as all this could be barking up the wrong tree.

 

[warpspeed]

might be a silly question Bob, but are the tyres the same? and what about the pressures? If you remember when I checked your rear tyres at Mallory your hot pressures were 27psi on the slicks and that was causing you issues with oversteer, I know the toe was wrong and all that but still worth double checking

 

[pulsarboby]

ok first of all guys the diff swapping has not worked its still exactly the same

so ive now changed every mechanical part of the car that could remotely be the cause.

the coilovers are a brand new set of bc's as i was having the same issue with the teins previously.
spring perches are even jim and cars been corner weighted to my weight but it still does this even if theres a passenger in the car

so do you think it should be toe out as opposed to to in on the rear?

ive kind of run out of ideas now as to why its doing this so im gonna take it back tomorrow and take the guy out in it so i can show him that its not in my head lol, hes agreed to try a few different settings out on a trial and error basis as i think even hes a bit stumped by this.
i just wanted to try get rid of any possible mechanical problems first rather than try mask them with incorrect settings

scott......ive swapped the wheels altogether in favour of 16s and all the tyres are yoko paradas and running 28psi on road.
at blyon i was instigating the oversteer to try eradicate the understeer problem which did work for a bit of fun but it doesnt make for quick lap times, hich is why im now trying to get to the root of the problem

 

[warpspeed]

could it possibly be something that's moving about in the engine bay rubbing up against a belt or something? I know these are stupid questions, but you never know and it's hard without hearing the noise, could you get a passenger to make a video?

 

[pulsarboby]

definately tyre squeal scott and you can feel the front going away from you too as soon as it starts
il try get a vid if i get time tomorrow then you can see that im not actually going that fast when this starts to occur

 

[AFDanHef]

il get to the bottom of this if i have to pull the thing apart piece by piece, i wont be beaten by a shitty little nissan grrrrr!

Damn Bob ... an endless sea of Pulsar parts at your finger tips and still can't get this sorted out. I've definitely felt this way about mine before. I don't know what to tell you though. All I know about suspension setups is what I learned from Gran Turismo 5. :doh:

Good luck to you bro!! If anyone can beat that "shitty little nissan" it's got to be you!! :-D

 

[warpspeed]

is the rear diff working properly?

 

[pulsarboby]

cheers dan but have to admitt its kinda getting the better of me now, very very frustrating indeed:frusty:


rear diffs been swapped too scott and thats all working a ok

would be good if i could install a camera under the car pointing to the wheels to see exactly what they were doing under loaded conditions whilst at different increments of lock

 

[pulsarboby]

right just got back from the setup place and basically after taking him for a runout he said it feels like a corner weight issue.

so whilst i was there hes adjusted the corner weights so the o/s front effectively has a 120lb extra loading, i took the car out to test it and its very hard to say whether its worked or not as it started hissing down with rain again which doesnt make for good test weather on busy roundabouts but one thing i did notice which has changed is the cars now much more inclined to oversteer as the rear whooped its ass end out.

after going back to see him weve decided to leave as is and see how she fares at cadwell on the 11th as you cant safely check it at speed on the public roads.
he also doesnt want to take the corner weight any further on it as he said it will compramise left hand cornering stability which i can understand.

one thing is, ive learnt a lot about steering geometry in the last few days which i never knew before lol
for example i always thought that stiffening front damping reduced understeer but actually its the rear stiffened and front softer which reduces understeer so seems ive been doing everything wrong
i must have just got lucky with my 1st widebody pulsar as that thing handled superbly compared to everything else ive driven and the underside was bent to boogery on it, perhaps i should attack this one with my biggest bestest hammer:lol:

thanks for all the help and input though guys, much appreciated

 

[fubar andy]

i always thought that stiffening front damping reduced understeer but actually its the rear stiffened and front softer which reduces understeer so seems ive been doing everything wrong

You see that's how I run my car (front hard rear soft), however I find that to work better for me that being softer at the front.
I've had a few raised eye brows when I mention my setup, but in the dry it works brilliantly and although I've tried it the other way around its never given me the confidence to turn in has fast as if it was softer on the front.

However in wet conditions I can do run the other way around and I find better grip in the wet.

Most people who say I should run softer on the front that the rear drive FWD, which says to me that sometimes FWD setups might not always work on other cars such as 4WD.

Again it's down the same old comments. "It depends on how you drive and how it feels best for you"

 

[pulsarboby]

yep totally agree with what youve just said really
ive always had a stiffun up front yet a soft assound:

but this cars really knocked my confidence so im willing to try everything if it helps keep it on track.

in theory i get what hes saying by having the rears stiffer it wont allow rear to squat when your on the power from an apex so therefore the front should not lighten/lift as much, but downside is your far more likely for the rear to break away as the gtir although 4wd is predominently a fwd car and has same sort of characteristics with understeer etc

il just have to go back to the drawing board and alter things and try them so i can see what works best for me so like you i can come up with the best setting for my style of driving

 

[vpulsar]

How about a crack in the chassis that only rears its ugly head under load that could change the geometry just a thought seeing as you've run out of ideas lol, I thought I'd chuck a silly one into the debate.



Rob

 

[pulsarboby]

yeah i thought the same rob and have gone over the chassis and turrets with a fine tooth comb and not a crack or defect in sight

something silly ive just thought of though, which ive not thought of yet.....im gonna try removing the front upper strutbrace as that could possibly be putting either too little or to much loading on the front as ive adjusted it so it pushes down/outwards on both turrets so in theory should push wheels into tarmac when one becomes light but it may well be having the opposite effect
same with the rear as the rear goes across turret sides as opposed to the tops

 

[warpspeed]

best way to prove how front and rear roll stiffness affects balance front/rear is to disconnect one arb drive car then reconnect that one and disconnect the other and go for a drive