The 911 front end "bob"

[RWD cossie wil]

I was lucky enough to drive a mates 996 turbo around castle coombe the other day, and I have to say it was great fun!

One thing I did notice is that coming out of camp corner, you are hard on the power for a long extended gradual right hander/ straight until you brake for Avon rise. As I was on the power, the front end feels very light & you get a bobbing sensation, with the car feeling like it wants to understeer, is this common to GT2s as well, or does the uprated suspension sort this out?

It only really seemed to stand out on fast bumpy corners, apart from that the car was amazingly good for a bog standard bar a remap road car

[Jibberingloon]

4WD + Track Days = fail..... Nuffffff Saiddd....

Also good Geo can sort out crappy handling

[Geneve]

Can't say. Combe is a bit 'bobbly' in places and most cars go light as you come up over Avon Rise.

Few years ago there was a very nasty accident where a GT2 clipped a Morgan at that point and went airborn, somersaulting along the Armco. Driver ok, just, but GT2 very squashed.

[mollytherocker]

It's a 911 trait. You find ways around it. Try a little trail braking for example.

[RWD cossie wil]

mollytherocker said:

It's a 911 trait. You find ways around it. Try a little trail braking for example.

Even 3-4 seconds after you are out of the corner?

[Perec]

mollytherocker said:

It's a 911 trait. You find ways around it. Try a little trail braking for example.

I bought a 991 with PDCC and the problem has gone away. Maybe trail braking would have been less expensive.

[mollytherocker]

RWD cossie wil said:

Even 3-4 seconds after you are out of the corner?

No, it was just an example. Keeping the tank full helps a bit, as does having a passenger.

After that, you are into geo settings.

[DallaraV8]

I would have thought it was all about weight transfer - so how would geometry changes make a difference?

[mollytherocker]

DallaraV8 said:

I would have thought it was all about weight transfer - so how would geometry changes make a difference?

I am certainly not qualified to answer that but I believe it can be reduced. Rear toe maybe?

[NJH]

If you're talking about the false right hand corner referred to as Folly corner its mega bumpy. My race car (944) will skip half way across the track there and to be honest I am grateful for a bit of understeer over those bumps.

[RWD cossie wil]

NJH said:

If you're talking about the false right hand corner referred to as Folly corner its mega bumpy. My race car (944) will skip half way across the track there and to be honest I am grateful for a bit of understeer over those bumps.

Yeah I think that's the one, just off the start finish straight. As said, it's probably a combination of neatly 500bhp lifting the front up, the 4x4 pulling the front wheels, having steering angle on & the car being unweighted through the corner, but it was quite disconcerting the first few times! Not really having driven a turbo in anger on the roads, I was just wondering if it's a common occurrence really?

[nxi20]

I think I know the feeling you're getting. I experienced it years ago on exactly the same corner at Combe in my (new to me then) GT3. I had an instructor with me that day & he couldn't work out (from the passenger seat) what I was doing to make the car feel so unsettled; it felt like the car was rocking between n/s/f & o/s/r - a most odd sensation that could only be felt from the passenger seat. It was only after we swapped places that he declared that there was something wrong with the setup of the car.

It turned out to be the left rear toe was way off & the wheel was effectively steering the rear of the car left on right handers. Oddly it never really showed up in a noticeable way anywhere else on the track or the road.

[Perec]

RWD cossie wil said:

NJH said:

If you're talking about the false right hand corner referred to as Folly corner its mega bumpy. My race car (944) will skip half way across the track there and to be honest I am grateful for a bit of understeer over those bumps.

Yeah I think that's the one, just off the start finish straight. As said, it's probably a combination of neatly 500bhp lifting the front up, the 4x4 pulling the front wheels, having steering angle on & the car being unweighted through the corner, but it was quite disconcerting the first few times! Not really having driven a turbo in anger on the roads, I was just wondering if it's a common occurrence really?

911s have traditionally tempted to bob out of corners. My assumption has always been that the cause was unweighting of the front exacerbating any unevenness in the surface at exit. The 991 seems to do it less than previous iterations and the PDCC not at all, as far as I have discovered yet.

[anonymous-user]

It was flat out through Folly in my 996 GT3 and car felt great - made you grip the wheel a bit though as very fast!
No bobbing.

[Perec]

Here are what appear to be a 997 and PDCC test mule. If you watch the yellow (non-PDCC car) you'll see it bobbing. http://www.youtube.com/watch?v=UcHGxEj18Q0

Though the surface appears flat, which suggests that it must be about something other than the levelness of the track.