R400 turn in and understeer
Discussion
Why do you immediately point the finger to the arbs ? Maybe there's a reason you suspect them but its not necessarily the first thing to look at when addressing handling. Remember that you have many parameters that can introduce understeer or oversteer so in order to track down the inbalance you need to ensure that the basics of the car are correct first and rule them out. That way you won't get into an endless 'sawing the legs off the table routine'.
I'd start with the basics by looking at relative ride heights/rake (at least 1.5cm rake) and tyre pressures when hot. Make sure you have balanced spring rates front and rear as well.. running stiff on the front (without uprating the rears) is a common infallible "road" setup but is quite simply, understeer city. You should also be toeing out a little on the front for the cct and also check the camber for your tyres. If you haven't had it done then really its best to get all this sorted in one go with a specialist like racecardoctor.com who will come to the cct and flat floor and set the car up exactly as you like it. Once its done its done.... certainly dont do what i did and thats run for a whoel years trackdays without a proper setup, its just wasting your time and halving your fun and speed.
I'd start with the basics by looking at relative ride heights/rake (at least 1.5cm rake) and tyre pressures when hot. Make sure you have balanced spring rates front and rear as well.. running stiff on the front (without uprating the rears) is a common infallible "road" setup but is quite simply, understeer city. You should also be toeing out a little on the front for the cct and also check the camber for your tyres. If you haven't had it done then really its best to get all this sorted in one go with a specialist like racecardoctor.com who will come to the cct and flat floor and set the car up exactly as you like it. Once its done its done.... certainly dont do what i did and thats run for a whoel years trackdays without a proper setup, its just wasting your time and halving your fun and speed.
There are clearly loads of variables, but my thoughts would be try a thicker bar on tghe back not a thin bar or no bar on the front - I found the latter made the car liable to quite sudden roll-induced oversteer sometimes, and that's not nice. Also, from a driving style perspective, Caterhams require you to trail-brake quite heavily into the corner to get them to turn in, then jump to the throttle smoothly for the mid corner/exit phase. If you brake in a straight line, come off the brakes, turn in harshly, then power on harshly they will understeer for britain. I found it best to rotate the car on the brakes with very little steering lock. This requires brakes with excellent feel and a lot of practice, but if done smoothly you can balance the grip front to rear very effectively with the pedal pressure.
jwyatt said:
I found it best to rotate the car on the brakes with very little steering lock. This requires brakes with excellent feel and a lot of practice, but if done smoothly you can balance the grip front to rear very effectively with the pedal pressure.
Can you tell me more about this technique?
I'm getting a caterham in the acadamy - never driven one do they have other traits - like mini's have lift off over steer - which if used to good effect can get the car to turn with out even steering!
jwyatt said:
There are clearly loads of variables, but my thoughts would be try a thicker bar on tghe back not a thin bar or no bar on the front - I found the latter made the car liable to quite sudden roll-induced oversteer sometimes, and that's not nice. Also, from a driving style perspective, Caterhams require you to trail-brake quite heavily into the corner to get them to turn in, then jump to the throttle smoothly for the mid corner/exit phase. If you brake in a straight line, come off the brakes, turn in harshly, then power on harshly they will understeer for britain. I found it best to rotate the car on the brakes with very little steering lock. This requires brakes with excellent feel and a lot of practice, but if done smoothly you can balance the grip front to rear very effectively with the pedal pressure.
Thanks James, that could be useful. My technique has been very much braking in a straight line and then turning in with throttle.My Academy car was not one of the earliest delivered, so I borrowed a grads car for a couple of trackdays - my first ever track time (and my first times driving a RWD car) the winter before my Academy season started. As per my general approach to things I read a lot of theory (can recommend some good starter books) as well, and had some initial instruction.
Beyond feeling out of my depth and cacking myself for those first two, mostly wet, trackdays the first things I noticed were a) I kept spinning with no real control over the car from the start to end of the spin (this didn't happen for long - after a few months I went to about 1 or 2 spins a year/3k track miles - just don't lift off when the back steps out!) and b) the car just did not want to turn in after coming off the brakes. I kept staying on the brakes to the apex, before moving swiftly to the throttle to balance the car mid-corner then apply power and exit. At first I worried that this was "wrong" but guys who knew a lot more than me just grinned and said "trail braking is a standard Caterham race technique. Keep doing it".
From that point on I tried to smoothly use the brakes to help the car turn in - not hard, decelerative braking, but enough to transfer weight to the front end and help it turn in. I always noticed that most of us at the front end of the grid did this to a varying extent - though most used more lock than me and applied it quicker - and the guys mid-grid were turning in off the brakes and understeering like a bastard. Hitting the throttle just made it worse for them, as weight transferred rearwards. They were at the limit - for their style - but that limit was less than ours was. The guys at the back of the grid are just not at the limit, whatever their lines/technique.
Also, if you get the car pointing in the right direction by the apex, using the brakes to help rotate the car, you can apply power hard, as you should - this is the most critical area to a good lap time - apply the power early, keep it applied, and hold that speed all down the next straight. In my first year my braking was poor in terms of how late/hard, it was an issue for me in the first few races, yet in pure lap times I was pretty much always top 3. Brake technique, to help with turn in and thus exit, meant more than just braking late and sailing past the apex in a squeal of understeer.
Part of this is natural technique and even physiology - I have a very sensitive inner ear and often feel I have had "big slides" that passengers and spectators never noticed (and I get motion sick doing aerobatics in planes) - but you can work on it. You need the sensitivity to feel you are balancing the grip from the front to rear of the car. On the road I often use a little lift or brake to help turn in or change direction, and even in a FWD car (albeit a stiff, sporty one) I can adjust the handling balance to slight oversteer on entry with the brakes if I want. Practice! Slaloms are great for learning about weight transfer.
Being able to feel when the tyres are at a slight slip angle (their grippiest) in a corner is a valuable skill also, and this takes a lot of sensitivity again. Too little slip, and you are slow, too much and you destroy tyres faster for no benefit. The only time I deliberately went for big slip angles, taking advice from Ross Bentley in "Speed Secrets" (a good starter book) was in the wet where sliding early gives you a better feel for the grip available. Worked for me, I won my only wet race.
At a far more exalted level F1 drivers use the same sort of thing but far more skillfully - techniques differ from the extreme trail brakers like Ralf and MS to the more traditional drivers like JPM - but most single seat racers use the brakes quite heavily right up to the apex - partly to slow the car as late as possible, and partly to help it turn in. The guys doing this more take an earlier, less violent turn-in and thus a shallower entry line. Turning in with less brakes requires a later, harsher turn-in and a car with a more oversteery setup.
Anyway, probably bored you all to tears, but you asked! My average qualy/finish was something between 2nd and 3rd in Academy, Roadpsorts B and 750MC class C sevens, having never tracked a car before a few months before my Academy year, karted, or even driven RWD on road, so it's probably not all total drivel!
Beyond feeling out of my depth and cacking myself for those first two, mostly wet, trackdays the first things I noticed were a) I kept spinning with no real control over the car from the start to end of the spin (this didn't happen for long - after a few months I went to about 1 or 2 spins a year/3k track miles - just don't lift off when the back steps out!) and b) the car just did not want to turn in after coming off the brakes. I kept staying on the brakes to the apex, before moving swiftly to the throttle to balance the car mid-corner then apply power and exit. At first I worried that this was "wrong" but guys who knew a lot more than me just grinned and said "trail braking is a standard Caterham race technique. Keep doing it".
From that point on I tried to smoothly use the brakes to help the car turn in - not hard, decelerative braking, but enough to transfer weight to the front end and help it turn in. I always noticed that most of us at the front end of the grid did this to a varying extent - though most used more lock than me and applied it quicker - and the guys mid-grid were turning in off the brakes and understeering like a bastard. Hitting the throttle just made it worse for them, as weight transferred rearwards. They were at the limit - for their style - but that limit was less than ours was. The guys at the back of the grid are just not at the limit, whatever their lines/technique.
Also, if you get the car pointing in the right direction by the apex, using the brakes to help rotate the car, you can apply power hard, as you should - this is the most critical area to a good lap time - apply the power early, keep it applied, and hold that speed all down the next straight. In my first year my braking was poor in terms of how late/hard, it was an issue for me in the first few races, yet in pure lap times I was pretty much always top 3. Brake technique, to help with turn in and thus exit, meant more than just braking late and sailing past the apex in a squeal of understeer.
Part of this is natural technique and even physiology - I have a very sensitive inner ear and often feel I have had "big slides" that passengers and spectators never noticed (and I get motion sick doing aerobatics in planes) - but you can work on it. You need the sensitivity to feel you are balancing the grip from the front to rear of the car. On the road I often use a little lift or brake to help turn in or change direction, and even in a FWD car (albeit a stiff, sporty one) I can adjust the handling balance to slight oversteer on entry with the brakes if I want. Practice! Slaloms are great for learning about weight transfer.
Being able to feel when the tyres are at a slight slip angle (their grippiest) in a corner is a valuable skill also, and this takes a lot of sensitivity again. Too little slip, and you are slow, too much and you destroy tyres faster for no benefit. The only time I deliberately went for big slip angles, taking advice from Ross Bentley in "Speed Secrets" (a good starter book) was in the wet where sliding early gives you a better feel for the grip available. Worked for me, I won my only wet race.
At a far more exalted level F1 drivers use the same sort of thing but far more skillfully - techniques differ from the extreme trail brakers like Ralf and MS to the more traditional drivers like JPM - but most single seat racers use the brakes quite heavily right up to the apex - partly to slow the car as late as possible, and partly to help it turn in. The guys doing this more take an earlier, less violent turn-in and thus a shallower entry line. Turning in with less brakes requires a later, harsher turn-in and a car with a more oversteery setup.
Anyway, probably bored you all to tears, but you asked! My average qualy/finish was something between 2nd and 3rd in Academy, Roadpsorts B and 750MC class C sevens, having never tracked a car before a few months before my Academy year, karted, or even driven RWD on road, so it's probably not all total drivel!
Edited by jwyatt on Friday 11th August 15:11
nice post james. On entry as more lateral grip is required, the maximum braking/forward grip is gradually reduced from entry to apex.... so it makes sense that you really should be coming off the brakes slowly from entry to apex in order to fully utilise the tyres maximum grip throughout. If you brake in a straight line then the moment you come off the brakes and turn in you are effectively wasting the tyres grip. I found its pretty much manadatory for some corners or you simply will not get round (riches, parabolique, redgate etc..)
Of course, to the original poster, have a think about the rake of the car too - the difference in ride height front to rear. If the rear is not a bit higher you could suffer understeer even if the car is cornerweighted, the spring rates/damper settings are good, tyres are OK and ARB's are appropriate. Some toe-out often helps too, and of course you need some neg camber.
It's never easy!
It's never easy!
Books - "Speed Secrets" and "Speed Secrets 2" by Ross Bentley are great starters. Yes the english may be basic but the points are very, very valid and the discussion about lines and how they vary according to what comes before/after a corner is excellent.
Drive to Win by Carroll Smith is pretty good - it goes into the turn-in thing mentioned above (though in extreme style - more suited to single seaters but the points are valid) and also has some technical discussions about different types of LSD that won't make you go faster but might make you win some pointless pub arguments.
And there is a book called "Going Faster" by Skip Barber which is quite a good all rounder, again more advanced than the Ross Bentley ones.
Besides that, my advice to beginners who need to learn to push hard quite quickly, to compete, would be to first do some airfield days and really push - spin a lot if that's what it takes - until you learn about understeer and oversteer and how to balance the car with weight transfer. Slaloms help. After a few airfield days and a few trackdays do more trackdays on the tracks you'll be racing at, and get instruction, it doesn't need to be someone super expensive just someone that knows enough about technique to help out. Then work on increasing your pace smoothly, working on corner exit and high speed corners first, then working back through apex to braking and entry. You don't need to be the last of the late brakers initially, just get the exits right every time and hold that speed. You will always be the limiting factor in the car so don't worry too much about setup to start with - before the season starts get the weights right, cornerweight it and get all the gemoetry correct, but always focus on yourself. That other bloke isn't a second a lap faster than you because he's got 2mm more rake and half a degree more neg camber, he's faster because he's driving better. Accept it and improve. That's the beauty of one-make racing and why I'll do it again, it's 99% about the driver.
I was keen to become an ARDS instructor before we had our daughter, I might do so one day, I enjoy teaching almost as much as doing stuff as long as it's with people that want to learn.
Drive to Win by Carroll Smith is pretty good - it goes into the turn-in thing mentioned above (though in extreme style - more suited to single seaters but the points are valid) and also has some technical discussions about different types of LSD that won't make you go faster but might make you win some pointless pub arguments.
And there is a book called "Going Faster" by Skip Barber which is quite a good all rounder, again more advanced than the Ross Bentley ones.
Besides that, my advice to beginners who need to learn to push hard quite quickly, to compete, would be to first do some airfield days and really push - spin a lot if that's what it takes - until you learn about understeer and oversteer and how to balance the car with weight transfer. Slaloms help. After a few airfield days and a few trackdays do more trackdays on the tracks you'll be racing at, and get instruction, it doesn't need to be someone super expensive just someone that knows enough about technique to help out. Then work on increasing your pace smoothly, working on corner exit and high speed corners first, then working back through apex to braking and entry. You don't need to be the last of the late brakers initially, just get the exits right every time and hold that speed. You will always be the limiting factor in the car so don't worry too much about setup to start with - before the season starts get the weights right, cornerweight it and get all the gemoetry correct, but always focus on yourself. That other bloke isn't a second a lap faster than you because he's got 2mm more rake and half a degree more neg camber, he's faster because he's driving better. Accept it and improve. That's the beauty of one-make racing and why I'll do it again, it's 99% about the driver.
I was keen to become an ARDS instructor before we had our daughter, I might do so one day, I enjoy teaching almost as much as doing stuff as long as it's with people that want to learn.
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