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
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!
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. Thanks all for the comments. I have since returned to the same place armed with what you have said (with a lookout to ensure area is clear!). I am now thinking more about the balance of the car and this line it is taking, and not just assuming that raw power will automatically bring the back out in any situation. It is actually quite nice to learn that it isn't trying to swap ends every time you put your foot on the accelerator!
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