981 GT4 at the beginning of each session at WGI on the first straight when it gets to speed had a very strong waggle during acceleration. . Has anyone else experienced this?

After an initial waggle, it's STOPS and is back to normal and I can drive the entire session without any trouble.

I first noticed this when it was wet and my tires were pretty worn. I switched to brand new tires and still had the issue, but only at the beginning of a session. My thought is that traction control might be wonky before it resolves, but welcome ideas.

I'm running Bridgeston Potenza RE71s tires. It was in sport mode, exhaust turned on and sport suspension (FYI - I tried once with sport suspension turned off and it still had the waggle).

 

If you have not already, be sure to check all of your rear suspension bolts.

 

The Cayman suspension is known to induce wiggle under hard braking on track. There are several threads on here (including the 718 forum) that talk about it.

I have experienced it too on my 981 GT4.

Some people change the alignment, others the suspension (e.g., add a DSC controller or change the suspension components), and some just adjust their driving style.

 

I typically ascribe any “first lap” oddities to tire pressure and tire temp. Since my tires gain anywhere from 3 to 5 psi as they heat up, I’ve noticed the first lap of a session always feels a little sloppy.

 

What pressure do you run when starting a session on cold tires?

A stock GT4 won't normally spin RE71S on dry pavement in a straight with a running start.

Have your mechanic put it on a lift to check all suspension fasteners and links.

 

I usually start the morning with pressures in mid 20’s, and then after a few laps I’m up in the 30s and then I try to bleed off to keep it around 32 or 33 when hot

 

Similar to my sessions. I take it slow while the tires are building pressure and heat at least for a full lap and then build. The car is loose and sloppy at the low starting pressure, feeling as if a tire could roll right off the rim.

 

Thank you for all the suggestions. To clarify, this happens under acceleration on the first straight at high speed. It does not happen under braking and only happens once. Cold tires seem like an unlikely suspect because it is fixed on the next straights in the rest of the first lap before the tires are warmed up. I had the suspension inspected by the folks at WGI's Little Speed Shop while up on a lift and nothing was loose or broken. I'm having it looked at more closely on Monday.

For some reason I suspect that it's computer-generated. The computer thinks it needs to fix something related to the limited slip or traction control, figures out that it's ok and doesn't do it again until it's reset on the next session.

 

Do you drive to the track on these wheels and tires? My wife's 982 GT4 is particularly sensitive to front:rear tire circumference ratios, and she'll experience a similar issue if she drives to the track on one set of wheels/tires and we put on a different set at the track. It seems the circumference learning will happen each time she goes out for a session where the car isn't too happy at first, but then it will figure things out by the 2nd lap. However, it won't remember the circumferences it learned on the previous session and thus this process gets repeated the next session out. If she drives to the track on the same wheels/tires, then the car seems to remember, and we don't have the same issue. FWIW, we never had this issue on her 981 GT4.

 

Very interesting. I'm running 19" wheels and maybe the car is trying to get used to them because the 20" is standard. I trailer it to the track. However, I've been running 19" wheels across 15+ track events and didn't have this issue until my last track event.

 

I'm running 19s and haven't had this issue. Drive to and from track. Since you aren't swapping, I would rule out this particular circumference issue, especially as it resolves itself right away.
My bet is something miscalibrated in the electric steering system, rack or otherwise. Check this thread: https://rennlist.com/forums/gt4-spyd...nd-idling.html

Try this next time out - tap the brakes when the wagging starts.
Else, try what is noted in the thread to recalibrate, drive a figure 8 lock to lock.
Elsewhere noted, if you have lots of camber, maybe reduce it a bit.