Sam's build thread

[sambb]

yep so finished 3rd on day 1 Esses: 30.33 https://bathurstlightcarclub.com.au/uploads/downloads/Results_Esses_NSW_7-3-20_Amended.pdf

and 4th on Day 2 Mountain straight: 55.48 https://bathurstlightcarclub.com.au/uploads/downloads/Results_Mtn_St_NSW_8-3-20.pdf


weather ended up perfect and cool after the rain. Win Percy and Gricey were there!. Favourite car was a datto 1000 which was running 4th overall for a while up the esses!

My hero at Bathurst is the guy that drives this Busa' Kart. Motor cycle engine psycho-ness and permanent opposite lock across the top and zero safety. very big balls has he. My mates Clio getting more and more serious by the meet but he had a horrible time with handling.
My car at the end of Day 1. Third place trophy for the Esses run and third place trophy from the 2019 Championship year which was a nice surprise. I only ran half the championship last year so never really looked at the points, so pretty happy with that.

[Sydneykid]

Good job Sam, well done, don't tell your mate in the Clio the secrets of FWD race car set up
Has he broken a rear hub yet? Tell him to check them regularly.
Every track is different on every outing, especially part time tracks that have things on them like buses spilling diesel fuel.
BTW, Justin's first race win in the Civic at Wakefield weekend before. The standard bottom end survived
Times were horrible, for everyone (familiar story), I chased the set up all weekend, made at least one change for every session, still wasn't perfect but good enough for the win in the final.


Cheers
Gary

[sambb]

Ha ha we did more or less set it up similarly to mine - just a bit softer overall and not as rear stiff wheel rate as mine. He completely reworked the front end by repositioning the strut towers and now has masses of caster. 7kg fronts, 6kg rears, Bilstein B14 dampers, stock front bar, fat rear bar. We'd measured out his rear beam ratios and it came out as a 300lb wheel rate. He only has 1.5 degree neg at the rear though. 205 front mediums and 195 rear softs. He reckoned it was undriveably snap oversteering on corner entry/turn in. Seems that to fit the rear 6kg springs he actually raised the back to get them in so maybe a combination of too high geometric roll + stiffer springs? I didn't know he'd raised the rear to fit them in when I gave them to him otherwise I'd have told him to re lower it at the rear especially for mountain straight. I think he just now actually has a front end on it so its nice and pointy when perhaps he's used to bigger steering inputs, so a combination of all that has the thing turn in oversteering. I said maybe more front toe out to put a bit of delay into the initial turn in response to more progressively load the rear?and to put the rear pair of Bilstein B14 kit springs back in which are softer and lower just to get him going again. Hillclimbs are way too hard to tune for on the day. I think he just needs an open pit day and to try a few setup things and he'll come good. Given the oversteer he had though he said there's no way he'd ever toe it out - I loved mine though.

He does have a gusset kit from the UK so he's going to try to find a spare beam and brace up the hubs. Part of that kit is damper pick up points for a coil over rear spring that sets the spring/damper combo together basically in line with the wheel centre for a 1.0 motion/leverage ratio. He spec'd 300 lb springs which if it is 1:1 should be 300lb at the wheel like he already has on the stock beam, but now he's worried that that rear wheel rate is way too stiff. He was aware of the rear hub bending problem - are you thinking that might have already happened and that's why it was terrible?

Awesome result at Wakefield. What was his qualy time and where did he start on the grid?

edit: he'd gotten it aligned before we left and the rear was ok. slight total toe in, just the whole beam pointing a whisker to one side.

[Sydneykid]

We run progressive grids, so where you finish the previous race is where you start the next race, qualified 3rd (1.06.7), finished race 1 in 3rd (8 laps), finished race 2 in 3rd (10 laps), finished race 3 in 2nd (12 laps) and finished race 4 in 1st (14 laps). Track got progressively worse from about 0.75 (Saturday morning) to 1.25 secs (Sunday afternoon) slower for both U2L and O2L than normal. Sunday is always affected by the chain lube from the superkarts

On the Clio, my guess is the rear roll centre (CoR) is too high, they need a lot of negative rake (rear down). The CoR and centre of gravity (CoG) move together so lowering the CoR will also help as it lowers the CoG. The turn in oversteer is a sure sign of that being the problem. The spring rate isn't outrageous enough to cause that problem, plus springs don't have as much effect when the rear is unloaded (as occurs on turn in). Too high a spring rate usually manifests itself mid corner when the weight is coming back onto the rear as acceleration is applied. Since it rolls so much at the rear, the rear swaybar is having a larger effect as well. Plus it rolls so much that 1.5 degrees of rear neg isn't enough. Especially when the rear hubs bend under load. If he shops around he might be able to pick up a set of Clio Cup rear hubs, if not then there are aftermarket kits available that use billet stubs with the later generation (larger) bearings and rotors.




I'd lower it at the rear as much as possible and then check the effect, if it's not enough (still has turn in oversteer) then I'd try the softer springs. Which will also lessen the effectiveness of the rear swaybar. Once it stops then you can tune it via the ride height, 3 mm makes a difference, so learn the relationship between the turns of the spring seats and the ride height changes. Then at the track it's simply a matter of adjusting the spring seat height and counting the turns.

Hope that helps
Cheers
Gary

[sambb]

I passed what you said onto Clio boy and he said that yep it was definitely that immediate reaction upon turn in. With respect to mid corner characteristics he said he still had a bit of floatiness in the fast stuff but was fine in the slow stuff eg The Cutting, which would point towards insufficient rear camber too yeah?
Its positive raked so seems like a decent drop in rear ride height is the main thing. He cant drop it too much without tyres rubbing so he's going to have to get more rear neg camber into it at the same time too, so between lower CoG, CoR and more rear neg camber I'm sure it'll be better even retaining the current spring rate.

So what do you make of the effect of more front toe out on dulling the impact of the initial steering input - much merit in that? If that's not why we do it what is the main benefit of decent amounts of front toe out?

sam

[sambb]

Thanks for the input on my mates Clio Gary. The aim is to make him happy but not quick enough to beat me! ha ha

Here are the vids of some runs.

Esses fastest run 2 because I'd buggered up run 3 (see above) and the track was gone by run 4. Bogged the start, late pinning the throttle out of the Elbow and turned into the kink before the dipper a little early but otherwise pretty clean.

https://youtu.be/zbl9lfJL5r4?t=102


Mountain straight run 3. Was my quickest to that point. My mistake was not getting out to the tree on the left side so that when I turned in at Suliman Pk the car stepped out a bit. Then I wasn't carrying enough speed through to Macphillamy. Things like getting on the throttle earlier out of Griffins and the cutting and not buggering up the above are what I managed to do on the final run where I went half a sec quicker, but sorry this is the quickest one that I filmed.

https://youtu.be/d9kHNd1nUi0?t=73

[HaydEn]

Good stuff Sam!


Sent from my iPhone using Tapatalk

[Sydneykid]

I passed what you said onto Clio boy and he said that yep it was definitely that immediate reaction upon turn in. With respect to mid corner characteristics he said he still had a bit of floatiness in the fast stuff but was fine in the slow stuff eg The Cutting, which would point towards insufficient rear camber too yeah?
Its positive raked so seems like a decent drop in rear ride height is the main thing. He cant drop it too much without tyres rubbing so he's going to have to get more rear neg camber into it at the same time too, so between lower CoG, CoR and more rear neg camber I'm sure it'll be better even retaining the current spring rate.

So what do you make of the effect of more front toe out on dulling the impact of the initial steering input - much merit in that? If that's not why we do it what is the main benefit of decent amounts of front toe out?

sam

It's a daisy chain action and reaction, the too high CoR and CoG makes it roll too much as soon as the steering wheel is turned, instantaneous diagonal weight transfer, the rear swaybar lifts the inside wheel reducing the traction, the insufficient rear camber results in the outside tyre reducing contact patch and losing traction, the stub axle flexes and loses even more camber so the outside tyre gets even less contact patch and loses more traction. Also, with the stub axle flex the inside wheel gains camber, so reducing that tyres contact patch. Add it up and the result = turn in oversteer.

There's bandaids, smaller rear swaybar, lower spring rate, more camber, stiffer stubs etc. But they probably won't be necessary if the actual cause itself is fixed. Although I'd do the stiffer stubs and larger wheel bearings even if it's only for safety.

Slower speed, shorter corners means less roll, hence less need for neg camber. Higher speed, longer corners show up any lack of camber. Plus the higher lateral G means the CoR and CoG have more force acting on/through them so a larger effect.

In simple terms, toe out is destabilising, toe in is stabilising. So toe out on the front means more reaction to steering inputs, more sensitive. This applies to FWD, RWD and 4WD. What is different with FWD (and 4WD) is that the front wheels are providing acceleration, so if we have more steering angle on the inside wheel it tends to "drag" the front of the car more around the corner.

I always run toe out on the front of FWD and 4WD cars, I run toe in on the rear of RWD and 4WD cars and of course I run toe out on the rear of FWD cars. How much varies between cars, tracks and drivers (some drivers just don't like the nervousness at the rear, particularly under brakes).

Also we have the ackerman effect (toe out on steering) which is there because the inside wheel turns in a tighter circle than the outside wheel. By adding some toe out we increase the resulting ackerman. A long discussion for another day, but in general the less the ackerman the more stable the car, lazy, the more reluctant it is to change direction. Think 60's American Yank Tank that had ackerman many metres behind the car. To a more modern, nibble FWD car with the ackerman at the rear axle line or even shorter.

Sorry, that was a bit of a rant
Cheers
Gary

[sambb]

No not a rant at all. All good stuff. I'd known about toe out giving quicker steering in a corner and like you mentioned as a way to sort of exaggerate Ackerman, but the reason I asked about front toe out putting a bit of initial delay into the first steering input at turn in was after reading about the new DAS system that Mercedes F1 team has shocked everyone with this year.

https://www.youtube.com/watch?v=U_uKHNJLSQs

So they are obviously using it for many different things - use toe out down straights in the wet to get temp into tyres, dont use it in the dry to reduce scrub or like they say help the airflow into brake ducts or over the body etc etc but they always seem to say its going back to toe out before the corners. I only know from seeing lots of interviews and stories about this system during testing that apparently one of the reasons the teams run front toe out for corners is so that say in a right hander the outside left front has to first move through the straight ahead position before it is angled into the corner and loads. I've seen it described as the front toe out giving a delay before the initial steering angle change throws load changes at the rear of the car. But thereafter everything takes a set. I guess thats an open wheeler/Kart type thing but it did make sense to me that that very first moment of steering input at a corner would be more reactive with toe in because the outside front is already 'loaded' in the direction of the corner. Hope I'm making sense there. So yeah thats why I was wondering if toe out, while making for nicer steering response in a corner, might cause a delay in steering response just at the very first initial input? I'm guessing that brief mSec moment of delay (if there even is one) would be pronounced in an open wheeler but couldnt be felt in a road car so there's no drawback to road car front toe, but yeah just curious.

[sambb]

whoooah Gary I just watched the IPRA vids shot from the green Barina. Holy hell he and Justin were going for it. Man that's the most unbelievable racing. Where I'm scratching my head though is how the hell a 7AGE can be in a Barina?!!