Handling and set up

[T0MMY]

What set up changes could you make to reduce the propensity of a car to oversteer off the throttle, without making it more understeery when balanced or on the throttle (i.e. not just adding more rear grip)? I'm hesitant to make changes to the geo as the handling's pretty good in general but I was wondering if the fact the car has (what seems to me) quite a lot of positive rake might be the reason it's so twitchy off the throttle or on the brakes?

Car in question is front mid-engined and RWD by the way.

[T0MMY]

I'd say most RWD cars that are reasonably sporty and "adjustable" are going to potentially oversteer when you're off the throttle, you want to be able to run the whole gamut from oversteer to neutral to understeer just by transferring the weight around.

The geo is set up as per the manufacturer's recommendations and as I say, it's far from terrible, just maybe a bit too pointy in slower corners.

[T0MMY]

Steve H said:

It would depend on the model and what adjustments you have available, options might include -

lose a bit of rake (drop the rear/raise front)

reduce rear toe out (if it has much)

damper changes (soften rear/firmer front)


Any of the above could alter how it feels on quicker turns as well but you'd have to try it to know......



How about driver options? Reduce trail braking into slow corners? More progressive steering?


TBH if it's stable into quicker turns and a bit lively into slower ones I'd mostly think that's a fun thing to drive, pretty ideal for trackdays .

I was playing with the damping at Rockingham on Sunday as I'd had the shocks rebuilt so they were quite a bit stiffer than they used to be. I have settled on a softer rear to dial out some oversteer in general but had got it about right for most situations so didn't want to go any further in that direction. I'll maybe try playing with the rear ride height at the next track day as like I said, it has quite a bit of rake.

In terms of driver options, I do already drive round it obviously but I feel it costs me time in some places. I was trying to find a good example in the videos from the day but it's quite subtle and hard to really see because obviously the car looks stable when you keep it stable! I noticed it most in the first left of Brooklands chicane where I can trail brake into the corner but then have to give the throttle the tiniest of tickles just to put some weight on the rear as otherwise it will slide at the back. Doing so then gives a smidge of understeer and I think I'd be quicker if I could come off the brakes and stay off the throttle before turning into the righthander. It's a very fine line between oversteer off the throttle and understeer on the throttle at those low speeds. If you've got sharp hearing you can just about hear the throttle blip at 4.49 in this video...

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

It's also a bit of a handful to turn into Yentwood and Tarzan where again you need to trail brake in to be quick but have to be very careful once you've got quite a bit of steering lock on and pretty much have to be very slightly back on the throttle before the apex which again induces slight understeer. On the other hand the "adjustability" on the throttle is perfect in faster corners like Gracelands so the aim would be to maintain that whilst dialling it out in slower corners (which obviously may not be physically possible to do!).

[T0MMY]

HustleRussell said:

I'd say your car is handling well. As said, try less rake.

Your lines are very symmetrical i.e. your entries are wide and swooping. It makes me wonder whether your front spring rates are too low.

ETA: Likewise, front roll stiffness

but try rake first, it's free.

Steve H said:

I'd agree with Russel about the entries, they do look pretty early although I'd expect going later and sharper to make turn-in-oversteer worse than the lines you were using there.

Just flicking through that video though I'm not seeing many issues on entry to the slower corners and more oversteer than understeer on the exits.

Thanks chaps, that's a good point about my lines, especially noticeable at Yentwood where I'm turning in well before the cone on the outside. Sounds odd to say but I genuinely can't quite decide if that was a deliberate (albeit unconscious) thing due to the way the car behaves on turn in or just due to poor technique/inexperience. I'll have to try to make a real conscious effort to turn in later on my next trackday and see how I get on. I'll also try dropping the rear progressively and see what effect it has.

E-bmw said:

OK, well we are going to have to disagree then as I have driven many "sporty" RWD cars & never experienced oversteer "off the throttle".

I don't think I'd want a trackcar that wouldn't oversteer when you lifted off the throttle, FWD or RWD, as that would suggest to me the balance was so far towards understeer that you don't have full control over how the car behaves in a corner. I haven't driven a huge array of cars but Elises, Caterhams and even MX5s will do this. The BMWs I've had (E30 and E36) were much more "stable" and would generally only oversteer under power or quite violent weight transfers so maybe that's what you're thinking of (just going by your name!)?

[T0MMY]

dunc_sx said:

A few questions/points for consideration from me are

1. How tight is the diff?

2. How evenly matched are the revs on your down shift? You could try revving higher during down shifts to see if that helps

3. Can you adjust the rear anti roll bar stiffness? Try softer?

Dunc.

1. Not sure what you mean by the tightness of the diff really...it's an LSD off a Sierra in not great condition.
2. it's a bike engined car so you can kind of take the piss with mid corner gear shifts as they're so smooth it doesn't really upset the car that much. I find it much harder to heel and toe smoothly than in my MX5 so don't generally do it on track any more as I found it was upsetting my braking more than it was benefitting my downshifts if you see what I mean. In my MX5, not doing so would massively affect corner entry but in this it doesn't seem to (watching the RGB series these cars race in it doesn't look like they rev match either for the most part).
3. I'd have to add a rear anti roll bar first!! No anti roll bars front or rear.

Kawasicki said:

Try some extra rear camber and both a little less and (obviously at another time!) a little more rear tyre pressure. What does your suspension look like? How far away are your spring aids at the rear?..if you have any! Are there any photos of your car from outside mid corner? Your car looks a bit too oversteery to be fast, so I think you could improve it a bit...i.e. you are not being daft!

I'd like to explore a bit more camber front and rear really but not sure much more is possible. This car is £4000 worth of very agricultural kitcar with sierra uprights etc., no rose joints in sight! I'll have a play with tyre pressures though. Suspension looks like 4 rather old and rusty Protech shocks and unknown springs (no aids), but the shocks were just rebuilt so have some damping these days There are some photos of the car from my last day at Rockingham here, although this was before the shocks were rebuilt:

http://www.motorsportinfocus.co.uk/2018-event-gall...

Edited by T0MMY on Wednesday 8th August 19:55

[T0MMY]

Steve H said:

Anything is possible but I can't see more rear camber reducing oversteer on turn-in when the car hasn't really had chance to lean over and benefit from some neg yet.

Might tame some of the exit oversteer I saw on the video.....

Not sure about the balance front and rear but looking around the paddock at other Caterhams and clones, I seem to have less camber than most at both ends. As I say though, I'll have to have a look and see how much more is possible.

[T0MMY]

Steve H said:

But again, the oversteer I saw was mostly at the exit.

Yeah, I've got to say, what you and others have said after seeing the video has got me thinking that as much as I enjoy the way the car handles, maybe it would be a quicker car if I dialled out some of the oversteer altogether so could get more power down. The other video I have on YT from that day was following an Elise Trophy car (an Exige S2) and what really struck me was how much better he was able to exit the corners, especially the hairpin. No way could I have got as much power down as he was able to and I don't think they use especially grippier tyres in that series than I use (595RSRs). Better lines/more skill too of course, and more weight over the rear wheels, but still.

Been a really useful discussion for me, so thanks for all the replies

EDIT: Actually, I'm going to upload the video of the first session of that day just to clarify what I mean about the turn in oversteer as the video you've seen is much later on when I was managing it and it does indeed look like the problem is all on exit.

Edited by T0MMY on Wednesday 8th August 21:34

[T0MMY]

Jesus, trying to cut and splice video on YT is a nightmare so I gave up and just pulled out 3 clips. These are all from the first 3 laps of the day when I was getting used to the car again, and the stiffer suspension. Even so, I wasn't taking the piss with the trail braking, just not managing the turn in quite as well as I was later in the day:

Yentwood:
https://www.youtube.com/watch?v=FEKZK8umoQo

Tarzan...you can just hear that although I feather the throttle to try to get some weight to the back of the car, it's not the throttle application that unsettles the rear:
https://www.youtube.com/watch?v=9LlLTfgv3kg

Brook chicane (to be fair, looks like I locked up the front left briefly so turned in a bit fast and a bit late):
https://www.youtube.com/watch?v=nRlx4axwIBU

As you can see, it isn't just an exit issue!

[T0MMY]

HustleRussell said:

How can you know that without knowing how much camber you have? You aren't complaining about mid corner grip and watching the video you don't have a wealth of traction on corner exit so more camber is not a logical conclusion.

The comment on more camber front and rear was just based on the fact that by eye, I clearly have less than most other 7s in the paddock on a trackday. I'm not complaining about the overall grip because I've nothing to compare it against; it has more grip than any other track car I've owned but I've never owned anything else comparable so that doesn't mean it couldn't be better!

HustleRussell said:

So the shocks weren't valved to the springs then?

You need to start at the beginning with this- spring rates, shocks, rake... Your front axle looks like it's too soft. Geometry and roll bars etc is just fiddling around the edges.

You should be able to take a more direct route to the apex, you are going the long way around- this tells me you're nervous of combining brakes and steering which makes me think the front axle is folding on you. The rear axle, stiff by comparison, is then letting go.

Well I'm starting off by looking at the things I can tinker with easily and for free (i.e. damping rates, ride height, tyre pressures). In a perfect world I'd send the car off to a specialist to get a full set up, corner weighting etc. but at the end of the day it's just a cheap track toy I drive a handful of times a year and trackdays, not racing, so there's a limit on how much money I'd spend on it. As for whether the shocks were valved for the springs, I've no idea as I didn't build the car but I assume they were bought from Protech with the shocks so were at least vagely matched to each other.

As Steve H pointed out, I maybe didn't explain this too well and the problem is more at the apex than earlier in the turn in phase. I can still trail brake quite far into the corner but once there's a fair bit of lock on and the car has slowed down, I tend to not only need to get off the brakes (as you'd expect) but also add a little bit of throttle (which I maybe wouldn't expect) to prevent oversteer. Interestingly, looking at that clip of Yentwood corner, I do turn in later before losing the back end....maybe I subconsciously changed my lines to reduce the steering angle after that little episode?

dunc_sx said:

Hi Tommy,

On point one, I was just trying to rule out a tightly locking diff (2-way for example).

On point two, I think that heel-toe is required on bike engined cars firstly to maintain good balance and secondly to protect the gearboxes, the bike gearboxes take a hammering in cars. I've owned and raced bike engined race cars for over ten years now and heel-toe on down shifts are a must, one caveat to that is if a slipper clutch is fitted which disengages the clutch on lift off to eliminate engine braking. In fact the radcial sportcars owner manual explicitly states that heel-toe technique must be done on downshifts on their cars.

I do understand your point on braking during heel toe, it does make accurate braking tricky.

Hope this is some help

Dunc.

Perhaps I should revisit that then. Ironically I do actually heel and toe this car on the road where you're rarely braking at 100%, just find it tricky on the track. With most road cars I've owned, heel and toeing seems easier to do smoothly on track when you are braking very hard as it's more of a stable platform to pivot your foot whereas in this car it's the opposite. I do put real effort into maximising braking on track though and get a fair few lock ups over a day on track so obviously that would be compounded as it's a pretty fine line between braking at the limit and locking up a wheel.

Edited by T0MMY on Thursday 9th August 16:26

[T0MMY]

Just to update this thread as I made a minor change and did another trackday at Rockingham. Basically where previously I had the rears on nearly maximum damping, this time I left them on the setting I use on the road (which was based on the principle of starting hard and winding them back until the ride is just about acceptable) but wound the fronts to their hardest setting as before. They're only single adjustable with a range of 0-10 clicks out from full damping so basically the fronts were on 0 and the rears were on 6. End result is the car was much less twitchy and I shaved 1.5 seconds off my best lap, however I also had new front tyres which would have accounted for a large part of that difference.

This was the fastest lap:
https://www.youtube.com/watch?v=C7X-x03uNOA

...but this one is more useful to see the difference in my inputs:
https://www.youtube.com/watch?v=-bRKfZRunao

The corner entry oversteer you see in a couple of places is now only because I'm able to trail brake further into the corner, rather than because the back doesn't have enough grip! The only place the car is perhaps worse is in the long fast left (Gracelands) where it's harder to get to the apex so I'm lifting off to get some oversteer (before it would tuck in nicely on the power as the slip angle on the rears increased).

Thanks for all the advice

Edited by T0MMY on Monday 3rd September 21:43

[T0MMY]

Jubal said:

Years ago I had an MK Indy which is almost the same car. Same shocks. It had a little bit more power than yours (R1 engine) and it only started behaving itself once I'd bitten the bullet and taken it to be set up properly. A nice guy round the corner from Oulton Park who was familiar with kits did a brilliant job and it transformed the handling, as far as the design limitations would allow. My reasoning was that even though the car was cheap and there's plenty to tinker with that's free, the trackdays themselves are expensive so I sacrificed the budget for a trackday which then paid for the setup. Good luck dialling it out, but to me your car appears far too tail happy given the lowish bhp.

You didn't read to the end of the thread! I don't blame you, it got quite long

I've got it much better now (see the last post before yours). Definitely quicker and I took Mike Epps (BTCC driver) out in it for a few laps and he thought it felt quite neutral, just would benefit from a tighter diff (which is way more money than I'd spend on it!).

I'm sure it would still benefit from a proper set up but it's not at all bad really and the lap times seem pretty good although it's hard to know what to compare it to as it miles off the spec of the ones that race in RGB. Caterham Academy cars coincidentally have the exact same power and weight and I'm 4 seconds quicker than their lap record but then I do have a bike engine which has some advantages.

[T0MMY]

dunc_sx said:

Not at all trying to pee on your bonfire as it's perfectly feasible that you are quicker but are you sure it's the exact same track layout? I've noticed Rockingham use a slightly longer layout with races sometimes.



The green bit is added on for the racing I've seen.

Glad your car is going better

Dunc.

Edited by dunc_sx on Thursday 6th September 12:33

My bonfire is still burning They have lap records for both the short and long layouts, 1:39.28 and 1:44.50 respectively with my best lap being a 1:35.27 on the short layout. Totally different car so doesn't necessarily mean that much, I was just using it as a yardstick due to the power:weight similarity as I can't find another kitcar series to compare to (the RGB cars are 100kg lighter than mine and have about 35% more power, plus full radical style bodywork so are much faster).

EDIT: Had a look at their regs and they use Avon CR322 tyres. No idea what they're like but to look at them they're not proper track tyres so my 595RSRs probably account for a chunk of time. The next level up (Roadsport) use Avon ZZS's which look more the part. Again, never tried them so can't comment on how good they are but they're 2.5 seconds quicker than the academy cars as a result (not sure what other differences there are between the classes).

Edited by T0MMY on Thursday 6th September 16:49

[T0MMY]

HustleRussell said:

Caterham Academy cars have had the same ditchfinder tyres for the past 20 years which would be easily surpassed in performance by most budget tyres on the market today. The minimum all up weight including driver is 615kg. The windscreen must be retained which acts as a parachute. The Sigma engine gives about 125bhp at under 7,000rpm and is coupled to an ‘H’-pattern gearbox with standard road car ratios which means that most of the time only 3rd and 4th gear are usable. They have an open diff and outboard narrow track suspension.

The Roadsport is the same car with trackday tyres, a rear anti-roll bar and a different brake master cylinder + bias valve.

Your car will be much lighter, have much less drag, a more powerful engine with a larger power band, a sequential gearbox with much more suitable ratios, a limited slip diff, a wider track etc etc...

This thread wasn't meant to devolve into a discussion about the relative merits of a BEC vs a Caterham, I wish I hadn't mentioned that now I was just looking for some way of seeing if the handling and therefore the laptimes were "decent".

That said, I think you're overstating the capabilities of my car. It isn't a "modern" MNR, it's the earliest RT, the 4th one that was ever made in fact and is all heavy sierra components and square tube and isn't capable of running the geometry of the RGB cars (it has outboard dampers too). It weighs 540kg so with me on board that's 625kg and the engine is a fairly tired early R1 with no proper airbox and only puts out 125bhp (dyno'd twice since built with identical results). Agree about the screen making a difference although that said, the academy cars are actually still pulling a higher top speed than I can get to at Rockingham (my top speed was 107mph from gps). The Tracksport cars are indeed a better comparison as they have proper track tyres and I believe they can ditch the windscreen, although I still have the sequential box advantage. They do have more power though I think?

Edited by T0MMY on Sunday 9th September 16:43