More dumb questions... 17s on Track?

[Lennym1984]

Hi,

 

Has anybody used 17s on track? I have 18s on my 987 (2.7) and on track they perform very well with plenty of grip and good "progressiveness" (even with an aggresive geo). I also have a set of 17s in the shed which I used to use when tracking my old Boxster (they're 986 wheels but fit the 987 with a 5mm spacer on the rear). I've tried them quite a few times on the Cayman and on public roads they are great (they make the 18s feel like the car is wearing lead boots), they're also significantly lighter (no idea how much but it is very noticeable just when moving them about). The issue is that - even at road speeds - they don't offer the same levels of grip as the wide 18s do. This is not an issue on the a40 but it may get frustrating on track.

 

Rather than shelling out on lightweight 18s, I was wondering about just running wider tyres on the 17s. I was thinking 255s on the rear (986 size) and 225s on the front. This will almost be as wide as the 18s and will retain a similar front to rear balance. Obviously the side walls will need to be larger but I don't think this will be a huge issue.

 

So before I order some new tyres, I thought I would see if anybody had any first hand experience of using the 17s on track days?

 

 

 

 

[Lennym1984]

I've current got a decent set of 235 rears on the 17s (PS2s i think) so changing the fronts only is a good shout. The geo on mine is fairly aggressive and feels well balanced on track but as you say, I can't see a 2.7 overwhelming 235 tyres

 

The weight saving between 17s and 18s is quite amazing and the larger sidewalls certainly help with the ride

[Joe Spicer]

I've done two trackdays this year in my 2.9 with 17's on (205/235). PS2's on the front and Conti Sport Contacts on the back. It's worth bearing in mind these were my first trackdays so have nothing to compare it to, and they were both quite wet days!

 

There was hardly any grip regardless because of the weather. Once the racing line dried out a bit though, I was impressed by how hard I could push them. I was running them at 30/31 hot pressures. I put tipex on the sidewalls to keep an eye on how much tyre roll I was getting, and it was fine- not leaning over too much at all even while driving the car harder than I've ever driven before! I was doing approx 1 minute lap times at Brands Hatch Indy.

 

I left TC on as it was still horrible and greasy if you strayed off the racing line at all, but was only getting the occasional rear wheel slip.

 

Not sure how helpful that is, but rest assured you can still give the car a good hooning.

On a related note, I went for a drive on the weekend after a service and I think the garage has inflated the tyres more than I would (specs are 30/31 psi on 17's) and the garage says he'd normally run around 37psi. I unintentionally got very sideways very quickly, so pressure seems to make a huge difference.

[Lennym1984]

2 hours ago, Joe Spicer said:

Not sure how helpful that is, but rest assured you can still give the car a good hooning.

On a related note, I went for a drive on the weekend after a service and I think the garage has inflated the tyres more than I would (specs are 30/31 psi on 17's) and the garage says he'd normally run around 37psi. I unintentionally got very sideways very quickly, so pressure seems to make a huge difference.

 

Are you sure about those tyre pressures? I'm fairly sure that the OEM specs for 17s and 18s are 37 on the rear and 30 on the front

[Joe Spicer]

20 hours ago, Lennym1984 said:

 

Are you sure about those tyre pressures? I'm fairly sure that the OEM specs for 17s and 18s are 37 on the rear and 30 on the front

Yep- thats straight off the plaque in the door with the tyre pressures on. See pic. 

I see everyone quoting higher pressures online and I'm a bit confused where this info comes from... I've tried them at higher pressure and it was terrible; the car felt skittish and the back end was skipping out everywhere, it just had no grip. The car feels much more planted and comfortable at 30/31, and can corner much harder (with no issues with tyre roll/wearing hard on the shoulders, or uneven tyre wear.

Edited January 19, 2021 by Joe Spicer

[Lennym1984]

42 minutes ago, Joe Spicer said:

Yep- thats straight off the plaque in the door with the tyre pressures on. See pic. 

I see everyone quoting higher pressures online and I'm a bit confused where this info comes from... I've tried them at higher pressure and it was terrible; the car felt skittish and the back end was skipping out everywhere, it just had no grip. The car feels much more planted and comfortable at 30/31, and can corner much harder (with no issues with tyre roll/wearing hard on the shoulders, or uneven tyre wear.

 

I see that you have a 987.2 - perhaps they changed the tyre pressures? My 987.1 definitely has 37 PSI for the rear on the door sticker.

 

ETA: A bit of Googling tells me that they changed the tyre pressure recommendations between 987.1 and 987.2. I might give the 987.2 tyre pressures a go.

Edited January 19, 2021 by Lennym1984

[Joe Spicer]

22 minutes ago, Lennym1984 said:

 

I see that you have a 987.2 - perhaps they changed the tyre pressures? My 987.1 definitely has 37 PSI for the rear on the door sticker.

 

 

Ah maybe. Although I'm not sure what difference that would make for this- unless the suspension and geometry is different?

[Lennym1984]

11 minutes ago, Joe Spicer said:

Ah maybe. Although I'm not sure what difference that would make for this- unless the suspension and geometry is different?

 

The geo is the same (same subframe, same arms etc) so I suspect that it may just be to improve/change handling. I'll give them a go but on track I find the stock pressuresfairly neutral.

Edited January 19, 2021 by Lennym1984