Your sizes are wrong and you’ll fry the ETS unit.


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Tire height is only off .1 (764 rev vs 761). I always understood that difference was acceptable.

 

Tire pressures?

ambient temps?

were lap times slower?

 

Tire height is only off .1 (764 rev vs 761). I always understood that difference was acceptable.

Yes, that is what a read and it was supposed to be an acceptable setup, since the difference between front and rear tires is still under 1%.

Tire pressure: 2.3 (heated)
Ambient temperature: 20'C
Lap times: did not measure it, but pace was similar.
VDC: R mode

 

Problem resolved - it was the Cup2 tires being too soft on the sidewalls, therefore - shaking the car too much over bumpy parts of the track. I did increase the tire pressure and it got a lot better, but the issue still remained. I then switched back to my previous 285 NR1 square setup and the problem disappeared.

Hope my experience would be of help to someone else...

 

If the sidewalls compress due to being soft you are compromising your “fixed” measurements and circumferences while compressed are substantially different then your 1% - that’s what is throwing you off. As Doug said you will fry ETS.

 

Yes, the non runflats need more pressure. I run 38psi hot (2.62bar).

also, the narrow fronts aren't helping any either; the car needs a square setup for road course work.

 

Your sizes are wrong and you'll fry the ETS unit. Sent from my iPhone using Tapatalk

Can you clarify what is wrong? The overall OD are pretty close. Not saying that is definitely not an issue but the general consensus on this forum is these are "within range".

I personally have not or will never try these combo sizes due to the fact that I need more front grip than rear grip, so I will try the widest tire I can fit on the front before even doing anything to the rear. Also, for the sake of safety, I'd rather run square sizes all around or stick to the OEM sizes.

 

Tire pressure: 2.3 (heated)

2.3bar is about 34psi, that is not all that low. I have been running 34/32 on my car all these years on non-run-flats. Cup 2 should have very stiff sidewalls compared to many street tires, so I doubt tire pressure is the issue.

The only thing that I suspect (and this is just my own theory) is while your overall diameter are in check, you are increasing relative rear grip by a whole lot more than the front. It IS entirely possible that Nissan built in their VDC program to the relative grip level front/rear, so you are getting these warning as a result of changing relative grip. However, I would imagine a sway bar change will do this kind of thing as well, so this reason may be very remote.

Have you tried turning VDC off and see if the car let you drive without intervention? Are these new Cup2 tires you put on or used tires?

 

Note that for Pilot Sport Cup 2 there are many variants of this tire model and while many are XL load rated, the N0 Porsche model is SL rated with a softer sidewall vs XL rated tires. Something to consider.

Yes, air pressures can be higher to help stiffen up tire under hard use. Tire diameter in those sizes is not much so that isn't the problem. More front tire width would be helpful to allow less stress on the narrow front tire.

 

Your sizes are wrong and you'll fry the ETS unit. Sent from my iPhone using Tapatalk

Stock 255/285 tire sizes are off by 0.6%, where the Cup2 265/305 setup is off by 0.4%. As far as I am aware, being within 1% should be fine.

If the sidewalls compress due to being soft you are compromising your "fixed" measurements and circumferences while compressed are substantially different then your 1% - that's what is throwing you off. As Doug said you will fry ETS.

My thoughts exactly, especially combined with the reduced tire radius, therefore more slippage when applying heavy trottle.

The only thing that I suspect (and this is just my own theory) is while your overall diameter are in check, you are increasing relative rear grip by a whole lot more than the front. It IS entirely possible that Nissan built in their VDC program to the relative grip level front/rear, so you are getting these warning as a result of changing relative grip. However, I would imagine a sway bar change will do this kind of thing as well, so this reason may be very remote.

Also considered it, but as you gave an example, there are plenty of mods that could lead to different grip levels between the front and the rear end.

Have you tried turning VDC off and see if the car let you drive without intervention? Are these new Cup2 tires you put on or used tires?

No, didn't try it and I guess it should probably work, but it won't really answer my question. The tires were brand new, produced in 2019.

Note that for Pilot Sport Cup 2 there are many variants of this tire model and while many are XL load rated, the N0 Porsche model is SL rated with a softer sidewall vs XL rated tires. Something to consider.

The Cups are XL rated, I was especially careful about that.

Yes, air pressures can be higher to help stiffen up tire under hard use. Tire diameter in those sizes is not much so that isn't the problem. More front tire width would be helpful to allow less stress on the narrow front tire.

That was the bottom line - when I rose the pressure to 2.6 the TC was engaging much less, but still had a significant presence. After switching back to my 285 square setup (used tires that I drove to the track with) the problem was gone.

Here I will add that on the Cup2s, the car was very bouncy/shaky. Although hard to belive, I actually started to think that the track surface might have changed here and there. With the 285 square this "almost leading to sea sickness" effect dissappeared again.

also, the narrow fronts aren't helping any either; the car needs a square setup for road course work.

I also believe the car requires more front grip as it tends to understeer on track and I have done many laps on the 285 square setup without an issue. That being said, what I do not like about the 285 setup was that the front end somehow feels very heavy.

So I just decided to try something different and this 265/35 + 305/30 Cup2 combo was the next most advisable "satisfying" setup on OEM rims.

By the way, these last days I did talk to other GTR owners, who drive on the Nurburgring and they told me that Cup2 are very good track tires indeed, but on any other F1 track, except the Nurburgring, as the last one being too bumpy. Without having tested it by myself on other tracks, I seem to agree...

 

No, didn't try it and I guess it should probably work, but it won't really answer my question. The tires were brand new, produced in 2019.

Well, if you want to know if the tires are causing issues or just the TC doing its thing, then turning VDC off will tell you. If the car drives fine without any interference or warning lights, then you know the TC is just working for you.

 

Well, if you want to know if the tires are causing issues or just the TC doing its thing, then turning VDC off will tell you. If the car drives fine without any interference or warning lights, then you know the TC is just working for you.

Agree. I suppose it will behave normally with the VDC off, except that I will carry the risk of the TC not being on-line in case truely needed. That's why I did revert to the 285 square setup again for testing and that basically answered the question.