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I wonder if anyone has tried 295/680/19 in the front on 10" wide wheels. w/ the 305/690-19s in the rear on 12" wide wheels.

The ODs go from from 25.8" to 27.1654" so it's a 5.29% change? Still within the Bosch 6% of OD limit but cutting it quite close. I'm not sure how the Traction Control & ABS would hold up. Has anyone tried that? @AWH I'm curious what you think as well, since I believe you are the only person I know of to ask Bosch about the limit.

-I read that most people are running 9.5" wide wheels in the front, so maybe that is why nobody has tried it. I ordered 10" fronts so it appears it should work & be within the Bosch limits slightly.

Also, @Arizona, are you using the DH compound? You still see a 3+ second lap difference at your local track using the harder compound vs the Hoosier R7s ? I was thinking of trying DM or DS, but I see the 255/650-19 appears to only come in DH.

Thanks again for your help. I'm a slicks newbie.
 

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Discussion Starter #22 (Edited)
680 is too tall, and anyway too tall for 690s rears. Maybe 650-660 front slicks with 690-705 Rears would work. Keep the ratio somewhere 1.04-1.06 from what I understood. 295/680/19 is a wide tire, I think it requires even a wider rim than 10 inch.

hoosiers are no good for my 911, I can do trofeo times, and slicks are like 2-3 sec faster than trofeo
I have now pzero, corsa, nankang, trofeo and hoosiers(rears left from my 911 and bought fronts only). Asap I gather info will post them here
 

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If you can fit the 10" do it. Wider is always better, your contact patch will be a lot bigger. On my Viper's I run a 300 front on a 12" wide wheel, the contact patch is huge.
 

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I wonder if anyone has tried 295/680/19 in the front on 10" wide wheels. w/ the 305/690-19s in the rear on 12" wide wheels.

The ODs go from from 25.8" to 27.1654" so it's a 5.29% change? Still within the Bosch 6% of OD limit but cutting it quite close. I'm not sure how the Traction Control & ABS would hold up. Has anyone tried that? @AWH I'm curious what you think as well, since I believe you are the only person I know of to ask Bosch about the limit.
1) I've never tried to cut it that close on the stagger ratio, so you are in uncharted territory. Theoretically should be fine. But...

2) Watch out for the rear part of the inner fender liner just in front of the doors when you use 10's and wide/tall tires. I can say that a 265/35-19 on a 10 will just barely graze the fender liner in both RE-71R and GY SC3. A 260/30-19 Sport Cup 2-240 or even a 275/30-19 PS4S will not.
 

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Discussion Starter #28
2) Watch out for the rear part of the inner fender liner just in front of the doors when you use 10's and wide/tall tires. I can say that a 265/35-19 on a 10 will just barely graze the fender liner in both RE-71R and GY SC3. A 260/30-19 Sport Cup 2-240 or even a 275/30-19 PS4S will not.
Is your car lowered or stock? I was looking for 265/35/19, and that is why I am asking
 

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Is your car lowered or stock? I was looking for 265/35/19, and that is why I am asking
I can confirm that Goodyear Eagle Supercar 3Rs 245/35/19 & Hoosier R7s 265/35/19 don't rub on the OEM 9" wheels w/ the OEM suspension. Both are similar lap times for me (within 1 second or so) but the r7s can handle a full 30 minute track session without overheating. I get maybe 4 laps out of the goodyears before they are too hot & start to scare me. The Trofeo's seemed to overheat at about the same time, but they lost all grip forever after the first heat cycle. Letting those cool down didn't help. The goodyears last me multiple track days while setting great lap times so long as I let them cool down 1/5 time attack laps or so.

So far those R7s 265/35/19 (front), 305 rear are the quickest & most consistent tires I've found for the OEM wheels. I also tried Toyo R888Rs, p Zero, Trofeos, etc... in most sizes. The only tires I'm waiting to try are the 265/35ZR19 Goodyear 3rs up front. I have a set ordered for the front & will report back.

I'm also waiting for my 10" finspeed front wheels w/ pirelli slicks. From what others have said, that should by far be the fastest setup. I'll post lap times & hopefully videos comparing them all for me at Big Willow.
 

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Discussion Starter #31
Thanks AWH

Guys quick question, I am going to participate to a track event, I have done -2.2 camber on all four wheels, light toe out in the front (0.02 or so), 8 degrees caster and 0.16 toe in in the rear.

I can add spacers 11/15mm if needed and installed kw/novitec springs with same rake as 765LT, -5mm in the front. Going to test everything, suspension feels a bit better than OEM in my opinion, have to check the weight transfer at the track, but I guess it will be ok. Also added girodisc rotors and pads.

I have 2 sets of OEM wheels, and asking which combo should I use:

Nankang 235/305 brand new - already installed on a spare lightweight set of rims
Trofeo 245/305 OEM MC1
Hoosiers 235/305, but rears have already 1.5days with my 991.2 TurbosS

On my primary set of wheels having PZero Corsas now, but I might put Trofeo or Hoosiers, considering more to use Hoosiers, but maybe you can help me out with your opinion

Which is the order of laptimes in your opinion? I would take the Nankang and Hoosiers, but not 100% sure...

Also what is cold/hot pressures you are running at the track with 720S using these tires?
 

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Discussion Starter #32
So to cut the story short, here are my lap times:

Corsa - 1:27.x
Nankang 1:24.6
Hoosiers 1:24.1

Hoosiers are more predictive and stable,with AR1s the car oversteers more as the ODs are a bit off and the rake is more to the front. I feel the car still need more front tire, 265-275 would be a great option. As far as AR1s are 2.5x cheaper than Hoosiers, they are the best choice for trackdays. They have released 325/30/21 for GT2RS/GT3RS/AMG GTR PRO etc... so maybe they will do 325/30/20 and we will pair them with 265/35/19 in the front for the best Rcompound combo.

Nankangs were feeling best at about 2.0bar and 45-55C temps.
Girodisc setup felt great, I would say much better than OEM as brake feeling and modulation.

Now looking for slicks setup R19, considering at least 260mm and 315-320mm F/R, as far as I have found Hankook and Avon might be good options. Pirelli seem a bit to narrow, and wondering if 255/650/19 paired with 315/705/19 would be a good choice.

I am also lowered on KW springs.
 

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Update...

Did some more tire testing for the magazine this week. Can't spill the whole story until it sees print, but here's a few hints:

1) 265/35-19 fits up front on a 10" wide wheel with just an occasional fender liner touch at the back of the arch to the very outer shoulder of the tire. Should be a non-issue with stock 9" or a 9.5". 305/30-20 on 12's for the rear fits free and clear. Wheels are Finspeed.

2) Goodyear SC3R is magic. Mega-grip, super-responsive, consistent.

3) Trofeo R just as quick, but only for a single flyer once warmed up...and then falls off a bit for rest of session (tried to kill me when that happened...). Imagine you are an F1 driver having to get the tires perfect for that one qualifier.

If budget/availability were no object, I'd run SC3R on the 720 all day, every day.


There's also a 200tw test I did recently that should be in the next issue of Grassroots Motorsports Magazine.

GY Supercar 3 vs Bridgestone RE-71R vs Michelin Sport Cup2 -240. Look for it.
 

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Discussion Starter #34
So you were able to run 265/35/19 & 305/30/30 combo without any issues from ABC, TC, ESP etc?
Maybe if you know the diameters of each tire,that would help a lot.
 

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So you were able to run 265/35/19 & 305/30/30 combo without any issues from ABC, TC, ESP etc?
Maybe if you know the diameters of each tire,that would help a lot.
Yes, no issues. I've run six different brand/model tires in those sizes in the past two magazine tests I did.

As I've stated before, friends at Bosch have told me that the allowable deviation for the ABS/ESC is 6% from the OE stagger. I have spreadsheets to calculate that variance. Nothing fancy. Dimensional data comes from TireRack.com and has proven to be accurate.
 

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Discussion Starter #36
265 front wheel can be a game changer, I am so happy that it worked well for you.
So the OEM ratio is 27.2/25.8=1.054

1.054+6%...hmmm I think that would be too much of a difference, so will calculare 6% as +3% till -3%

so 1.054+3%=1.085
and 1.054-3%=1.023

In my opinion even with these sizes, it will be risky....I have done 25.5 paired with 27.2 tall tire and it worked well (1.0666 ratio)

Lets say 26-26.3 fronts paired with 27.1-27.2 rears will give us 1.03 ratio, so for me at the moment I would stay in this interval 1.03 till 1.07

Maybe some others might have other expericences to share with us. I would try also soon 265/315 Trofeo on OEM wheels, it seems like a fast combo and the ratio is really close to OEM, only downside is their price.

But if this is ok, we might use as-well 265/35/19 and 305/30/20 Nankang AR1s for the ones who want to save some bucks and still have a very potent tire (1.34 ratio)
 

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But if this is ok, we might use as-well 265/35/19 and 305/30/20 Nankang AR1s for the ones who want to save some bucks and still have a very potent tire (1.34 ratio)
I have a set of these that I'd be willing to let go for a great deal with very little wear on them, if anyone is interested. I just have two many tires right now (tested six sets).
 

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Discussion Starter #40
So I have ordered a set of Finspeeds F10 black gloss 10" fronts and 12" rears.

As for slicks I consider the following options, in this order:

1. Michelin 24/65-19 and 29/67-19. Ratio is 1.035. Fronts are 249mm and rears are 322mm. 25.5" and 26.4"
2. Hankook 260/650-19 and 300/650-19, ratio is 1.047. Fronts are 264mm and rears are 320mm. 25.5" and 26.7"
3. Pirelli 255/650-19 and 305/690-19, ratio is 1.035. Fronts are 251mm and rears are 305mm. 26.1" and 27"

I put Pirelli on the 3rd place because they are really narrow, and should fit stretched on a 12 rear wheel.
For me Michelin is the best brand out there, they are in Europe like 2250 Euros for this set, the Hankooks are 1850 Eur and Pirelli the most expensive at about 2400 Eur.

Michelin recommended for 10" and 11.5", still the rears are 322mm and they should fit ok on a 12 wheel
Hankook recommended for 10" and 12" (my sizes exactly)
Pirelli recommended for 9.5" and 11.5"

For me the next season the tire choices will be:

Nankang AR1 265/305 - I will try to put 265 in the front
OEM Pirelli TrofeoR MC1 - 245/305 and if I am going to like this tire on the 720S, I will try 265/315
I will skip on hoosiers r7 as they are almost as fast as AR1s but double the price.
Slicks Michelin and Hankook as first choices. it seems also Avon has some good options for our cars.
 
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