oversteer on a constant radius bend
Discussion
In the middle of last night, in the bone dry, I went to a deserted private business park and found a nice open roundabout with loads of room (3+ lanes wide) and nothing to hit. The purpose was to throw around my Merc 190E 2.5-16 and get a feel for how it handles, build confidence with it, and see how/if it oversteers and understeers and get used to it.
On normal roads I can provoke a little powerslide out of 2nd gear bends, which only need a little bit of opposite lock, but don't really require controlling as they sort of ride themselves out. It's very satisfying as the car fires out of a bend, with the back end faintly coming out but most of the power still being turned into forward motion.
Likewise in the wet, it's the back end I am very aware of and it will give a wiggle up to 70mph.
However, on this slightly off camber roundabout, I was very surprised to find that I had a very hard time getting it to do anything but understeer. It was dry and fairly grippy, and adding more power just brought some squeal and mild understeer. Adding more just brought on more understeer. Letting off would cause the car to tighten its line a lot and it always felt quite throttle adjustable, but never felt like it was going to break into oversteer. Rapidly adding power wouldn't get it to break traction, despite being in the power band in 2nd gear.
I kept everything quite smooth and didn't try flicking the car or anything tooo sudden.
Is this normal for a rear drive car? It has lots of traction, doesn't have much torque, has a long wheelbase, and an LSD. Is it just that I didn't have enough power to lose traction at the rear? Am I right to think the tight radius and long wheelbase mean the car would do nothing but understeer? Strangely, my 2.0 automatic 190E seems easier to unstick at the back, you slowly add power, at first spining an inside rear wheel and finally letting the back come round in slow motion, while the front maintains a grip on the road.
Russell
On normal roads I can provoke a little powerslide out of 2nd gear bends, which only need a little bit of opposite lock, but don't really require controlling as they sort of ride themselves out. It's very satisfying as the car fires out of a bend, with the back end faintly coming out but most of the power still being turned into forward motion.
Likewise in the wet, it's the back end I am very aware of and it will give a wiggle up to 70mph.
However, on this slightly off camber roundabout, I was very surprised to find that I had a very hard time getting it to do anything but understeer. It was dry and fairly grippy, and adding more power just brought some squeal and mild understeer. Adding more just brought on more understeer. Letting off would cause the car to tighten its line a lot and it always felt quite throttle adjustable, but never felt like it was going to break into oversteer. Rapidly adding power wouldn't get it to break traction, despite being in the power band in 2nd gear.
I kept everything quite smooth and didn't try flicking the car or anything tooo sudden.
Is this normal for a rear drive car? It has lots of traction, doesn't have much torque, has a long wheelbase, and an LSD. Is it just that I didn't have enough power to lose traction at the rear? Am I right to think the tight radius and long wheelbase mean the car would do nothing but understeer? Strangely, my 2.0 automatic 190E seems easier to unstick at the back, you slowly add power, at first spining an inside rear wheel and finally letting the back come round in slow motion, while the front maintains a grip on the road.
Russell
pentoman said:
.
However, on this slightly off camber roundabout, I was very surprised to find that I had a very hard time getting it to do anything but understeer. It was dry and fairly grippy, and adding more power just brought some squeal and mild understeer. Adding more just brought on more understeer. Letting off would cause the car to tighten its line a lot and it always felt quite throttle adjustable, but never felt like it was going to break into oversteer. Rapidly adding power wouldn't get it to break traction, despite being in the power band in 2nd gear.
I kept everything quite smooth and didn't try flicking the car or anything tooo sudden.
Is this normal for a rear drive car? It has lots of traction, doesn't have much torque, has a long wheelbase, and an LSD. Is it just that I didn't have enough power to lose traction at the rear? Am I right to think the tight radius and long wheelbase mean the car would do nothing but understeer? Strangely, my 2.0 automatic 190E seems easier to unstick at the back, you slowly add power, at first spining an inside rear wheel and finally letting the back come round in slow motion, while the front maintains a grip on the road.
Russell
However, on this slightly off camber roundabout, I was very surprised to find that I had a very hard time getting it to do anything but understeer. It was dry and fairly grippy, and adding more power just brought some squeal and mild understeer. Adding more just brought on more understeer. Letting off would cause the car to tighten its line a lot and it always felt quite throttle adjustable, but never felt like it was going to break into oversteer. Rapidly adding power wouldn't get it to break traction, despite being in the power band in 2nd gear.
I kept everything quite smooth and didn't try flicking the car or anything tooo sudden.
Is this normal for a rear drive car? It has lots of traction, doesn't have much torque, has a long wheelbase, and an LSD. Is it just that I didn't have enough power to lose traction at the rear? Am I right to think the tight radius and long wheelbase mean the car would do nothing but understeer? Strangely, my 2.0 automatic 190E seems easier to unstick at the back, you slowly add power, at first spining an inside rear wheel and finally letting the back come round in slow motion, while the front maintains a grip on the road.
Russell
Typical rwd behaviour esp in tighter radiuses - not enough power to break traction in the dry, just washes wide into understeer. You would need less overall grip (like in the wet) or more extremes of behaviour to unstick the back end.
Now the boy racer in me is annoyed with what the advanced driver in me is about to say...take care in your experiments as even wide open car parks have dangers and are subject to the law! Take double care in your sideways highway antics! Phew, really sorry, had to say it, it is the advanced driving forum after all!
I find airfield track days to be the best to test out levels of grip and car behaviours, especially wet winter ones!
Graham
Sounds like you might have needed a little more weight transfer over the front wheels to generate greater front end grip - perhaps a dab on the brakes before applying the throttle. 
I'm sure there will be some of the drifting boys along shortly to tell you all about dipping and then dumping the clutch to get the back to break free.
I'm sure there will be some of the drifting boys along shortly to tell you all about dipping and then dumping the clutch to get the back to break free.
gridgway said:
pentoman said:
.
However, on this slightly off camber roundabout, I was very surprised to find that I had a very hard time getting it to do anything but understeer. It was dry and fairly grippy, and adding more power just brought some squeal and mild understeer. Adding more just brought on more understeer. Letting off would cause the car to tighten its line a lot and it always felt quite throttle adjustable, but never felt like it was going to break into oversteer. Rapidly adding power wouldn't get it to break traction, despite being in the power band in 2nd gear.
I kept everything quite smooth and didn't try flicking the car or anything tooo sudden.
Is this normal for a rear drive car? It has lots of traction, doesn't have much torque, has a long wheelbase, and an LSD. Is it just that I didn't have enough power to lose traction at the rear? Am I right to think the tight radius and long wheelbase mean the car would do nothing but understeer? Strangely, my 2.0 automatic 190E seems easier to unstick at the back, you slowly add power, at first spining an inside rear wheel and finally letting the back come round in slow motion, while the front maintains a grip on the road.
Russell
However, on this slightly off camber roundabout, I was very surprised to find that I had a very hard time getting it to do anything but understeer. It was dry and fairly grippy, and adding more power just brought some squeal and mild understeer. Adding more just brought on more understeer. Letting off would cause the car to tighten its line a lot and it always felt quite throttle adjustable, but never felt like it was going to break into oversteer. Rapidly adding power wouldn't get it to break traction, despite being in the power band in 2nd gear.
I kept everything quite smooth and didn't try flicking the car or anything tooo sudden.
Is this normal for a rear drive car? It has lots of traction, doesn't have much torque, has a long wheelbase, and an LSD. Is it just that I didn't have enough power to lose traction at the rear? Am I right to think the tight radius and long wheelbase mean the car would do nothing but understeer? Strangely, my 2.0 automatic 190E seems easier to unstick at the back, you slowly add power, at first spining an inside rear wheel and finally letting the back come round in slow motion, while the front maintains a grip on the road.
Russell
Typical rwd behaviour esp in tighter radiuses - not enough power to break traction in the dry, just washes wide into understeer. You would need less overall grip (like in the wet) or more extremes of behaviour to unstick the back end.
Now the boy racer in me is annoyed with what the advanced driver in me is about to say...take care in your experiments as even wide open car parks have dangers and are subject to the law! Take double care in your sideways highway antics! Phew, really sorry, had to say it, it is the advanced driving forum after all!
I find airfield track days to be the best to test out levels of grip and car behaviours, especially wet winter ones!
Graham
Thanks, don't worry I'm careful by nature
. I figure a bit of danger in a deserted place like this to learn what the car will do is worth it, as it works to reduce the danger the rest of the time, on the road, as I will know how to control the car. I will be going on a track day soon too.
Amongst the various things that occured to be to get the back out, dipping and dumping the clutch half way round a corner was not one of them!! Probably won't use that one, sounds a bit harsh on the car!
Almost all production cars are set up to understeer at constant speed. Rwd cars also have an understeer 'hump' under gentle acceleration i.e. as you apply power the understeer gets more pronounced. If you have enough torque available, if you keep adding more and more power you can eventually get past the hump and into power-on oversteer, but watch out for the transition. The hump tends to be more pronounced in tighter corners, I suspect because the front geometry goes to pot when you have a lot of lock on.
If the car does have an LSD, then you are describing a typical behavior when pussyfooting around with the throttle.
My old Sunbeam-Lotus and Escort RS's exhibited similar characteristics, if trying to be all nice and girlie with it.
Take it by the scruff of the neck and use the diff properly, at turn in, dip the clutch to disengage the diff, bringing it back in sharply with power, then adjust as neccessary to keep the back end at the desired angle......
And yes, preferably not on a public highway.
Find a rally school that has a rwd car with lsd and book yourself a course to learn what you can about making best use of an LSD.
My old Sunbeam-Lotus and Escort RS's exhibited similar characteristics, if trying to be all nice and girlie with it.
Take it by the scruff of the neck and use the diff properly, at turn in, dip the clutch to disengage the diff, bringing it back in sharply with power, then adjust as neccessary to keep the back end at the desired angle......
And yes, preferably not on a public highway.
Find a rally school that has a rwd car with lsd and book yourself a course to learn what you can about making best use of an LSD.
If you are doing a track day, I would re-suggest an airfield. Tracks have lots of hard things to hit if things get out of hand and you want to push into oversteer territory. Cheaper too!
I spent a happy wet cold feb day a few years ago at Kemble (in the days when Easytrack and Bookatrack were one) trying to unstick a caterham with not great setup. It just would do nothing but understeer. Off/on throttle didn'd do it. The choices were:
too fast corner entry - it just span uncontrollably
off/on throttle in bend - nah
off throttle, big, big press of the brakes, on throttle - that did it
off throttle, depress clutch, revs, re-engage clutch - that did it but was horrible mechanically!
Graham
I spent a happy wet cold feb day a few years ago at Kemble (in the days when Easytrack and Bookatrack were one) trying to unstick a caterham with not great setup. It just would do nothing but understeer. Off/on throttle didn'd do it. The choices were:
too fast corner entry - it just span uncontrollably
off/on throttle in bend - nah
off throttle, big, big press of the brakes, on throttle - that did it
off throttle, depress clutch, revs, re-engage clutch - that did it but was horrible mechanically!
Graham
gridgway said:
If you are doing a track day, I would re-suggest an airfield. Tracks have lots of hard things to hit if things get out of hand and you want to push into oversteer territory. Cheaper too!
I spent a happy wet cold feb day a few years ago at Kemble (in the days when Easytrack and Bookatrack were one) trying to unstick a caterham with not great setup. It just would do nothing but understeer. Off/on throttle didn'd do it. The choices were:
too fast corner entry - it just span uncontrollably
off/on throttle in bend - nah
off throttle, big, big press of the brakes, on throttle - that did it
off throttle, depress clutch, revs, re-engage clutch - that did it but was horrible mechanically!
Graham
I spent a happy wet cold feb day a few years ago at Kemble (in the days when Easytrack and Bookatrack were one) trying to unstick a caterham with not great setup. It just would do nothing but understeer. Off/on throttle didn'd do it. The choices were:
too fast corner entry - it just span uncontrollably
off/on throttle in bend - nah
off throttle, big, big press of the brakes, on throttle - that did it
off throttle, depress clutch, revs, re-engage clutch - that did it but was horrible mechanically!
Graham
Interesting, I thought a Caterham would oversteer super easily with a bit of throttle!
For a bit I was worried Mercedes had set my car up to just boringly understeer... hopefully not.
I am very close to Kemble so will look into days there. It seems to make more and more sense for a bit of a play
.
You need to do a proper Drift Day. MrKipling43 said:
If you want to go to a track day to learn how to drift your car, be prepared to get yourself bollocked and thrown off the circuit.
Thankfully this is not necessarily true, I spent most of last Friday looking out the side window in the Z Coupe @ Bedford. The problems arise when your blatantly out of control, if you look like your in control when sideways you'll probably be OK.
Sounds like the car in question simply doesn't have enough torque to unstick the back end by conventional means (at least in the dry). LSD's quite often promote understeer as they lock the rears to the same rotational speed - result is the car resists turning. Popping the clutch would probably be enough to start a drift, but its a bit violent and you need to be very much on top of the car to control the result slide. I suspect you'd find the car much more oversteery in the wet, but its easier to lose control and requires more measured inputs, as many have already mentioned probably best trying this on an airfield day.
Here's my input into this.
Without putting too much strain on your car - Clutch dumping / shift locking (dropping a gear without match revs) there are two ways in which you can provoke a RWD and to some extent a FWD to brake traction at the rear.
From the original post it sounds like you are approaching things too quickly and as has been said already eventually you will brake traction but it will be sudden and harder to control. Also most islands require you to go left before you are going right so make sure you don't get on the power too soon and that the car is traveling right before you get on the power.
Method one: Go round the island at a steady speed in second, just quick enough for you to be able to feel some push towrds the outside of the island but get the car balanced so it isn't understeering. If it is you are going too fast. Aim for an exit as though you are going to come off the island (still on the power) turn sharply back towards the centre of the island and come completely off the power (whilst turning hard). Wait until you feel the back go light and bam, back on the power and get ready to catch it.
Method two: Treat your entry into the Island as though you we going round a bend. Come in at a reasonable speed, just a tad too fast (as in your passengers would wonder what the hurry was!) as you hit what would be the apex of the bend let the car settle then power hard.
That should see you on your way to getting the rear out in the dry. I'd avoid trying to use braking techniques as the front bias will make it very difficult.
A good place to practice is Curborough (spelling). It has a nice top corner and the surface is smooth. Trouble with airfields is they're made of concrete and distroy tyres - I only managed two hours at Bruntingthorpe in the dry before I had to retire. Brutners has lots of open space though! Personaly roundabouts are my favourite - I have lots of private ones honest.
Without putting too much strain on your car - Clutch dumping / shift locking (dropping a gear without match revs) there are two ways in which you can provoke a RWD and to some extent a FWD to brake traction at the rear.
From the original post it sounds like you are approaching things too quickly and as has been said already eventually you will brake traction but it will be sudden and harder to control. Also most islands require you to go left before you are going right so make sure you don't get on the power too soon and that the car is traveling right before you get on the power.
Method one: Go round the island at a steady speed in second, just quick enough for you to be able to feel some push towrds the outside of the island but get the car balanced so it isn't understeering. If it is you are going too fast. Aim for an exit as though you are going to come off the island (still on the power) turn sharply back towards the centre of the island and come completely off the power (whilst turning hard). Wait until you feel the back go light and bam, back on the power and get ready to catch it.
Method two: Treat your entry into the Island as though you we going round a bend. Come in at a reasonable speed, just a tad too fast (as in your passengers would wonder what the hurry was!) as you hit what would be the apex of the bend let the car settle then power hard.
That should see you on your way to getting the rear out in the dry. I'd avoid trying to use braking techniques as the front bias will make it very difficult.
A good place to practice is Curborough (spelling). It has a nice top corner and the surface is smooth. Trouble with airfields is they're made of concrete and distroy tyres - I only managed two hours at Bruntingthorpe in the dry before I had to retire. Brutners has lots of open space though! Personaly roundabouts are my favourite - I have lots of private ones honest.
A track day and a drift day are opposite ends of a scale. Don't get them mixed up.
On a track day, if you start sliding about too much you will be 'corrected' or shown the door. On a drift day, you won't be doing much other than sliding around, comparatively slowly and carefully.
With regard to your 190 understeering, I would suggest that you are travelling too fast and being too 'gentle'. To get the back to break away before the front does, you need to get the weight forward and have the car moving in an arc. You can figure out how to do that. If the car understeers, slow down, back off, try again.
The mechanical grip from the tyres will play an important role. Unfortunately, what you need for normal (safe) road driving is the opposite of what you for drifting/sliding about.
Contrary to what most people believe, a wet road is not going to help much because, although it reduces the grip at the rear wheels, it also reduces the grip of the front wheels, making understeer more likely.
As others have said, get yourself booked in on a drift day and you'll have plenty of practice getting the back out (and staying out).
On a track day, if you start sliding about too much you will be 'corrected' or shown the door. On a drift day, you won't be doing much other than sliding around, comparatively slowly and carefully.
With regard to your 190 understeering, I would suggest that you are travelling too fast and being too 'gentle'. To get the back to break away before the front does, you need to get the weight forward and have the car moving in an arc. You can figure out how to do that. If the car understeers, slow down, back off, try again.
The mechanical grip from the tyres will play an important role. Unfortunately, what you need for normal (safe) road driving is the opposite of what you for drifting/sliding about.
Contrary to what most people believe, a wet road is not going to help much because, although it reduces the grip at the rear wheels, it also reduces the grip of the front wheels, making understeer more likely.
As others have said, get yourself booked in on a drift day and you'll have plenty of practice getting the back out (and staying out).
GreenV8S said:
Almost all production cars are set up to understeer at constant speed. Rwd cars also have an understeer 'hump' under gentle acceleration i.e. as you apply power the understeer gets more pronounced. If you have enough torque available, if you keep adding more and more power you can eventually get past the hump and into power-on oversteer, but watch out for the transition. The hump tends to be more pronounced in tighter corners, I suspect because the front geometry goes to pot when you have a lot of lock on.
The strange transition point between the two is when you try to have a little innocent low speed fun on a mini island in the wet and get what appears to be understeer and oversteer at the same time.. most peculiar!
Gassing Station | Advanced Driving | Top of Page | What's New | My Stuff