paging F430GT, need ur expertise on scud tires and pressures again....

Those tires are stock on the Viper ACR: they have excellent traction but believe you are running the PSI too high. They heat up quickly so try 32 PSI.

 

John, the tires you got are old-spec Michelin PSC for the 2007 GT3 (N0). Michelin is now at N1 spec and N2 spec for these tires.

The MPSC N-spec is not the race-spec MPSC. The N-spec has lower grip, but it is still has more dry grip than most street tires.

For pressures, use 32 psi hot front and rear. They like low pressures.

I run the race-spec 265/30R19 and 345/30R19 MPSC, but they require much wider wheels. The race-spec sticks more, but it doesn't last with street use, as it was built as a track tire. I only drive on them to go back and forth the track.

The front tire, despite of being a 235, has too many grooves, and it induces understeer. Very likely you will notice less grip in the front axle.

Tire pressures depend on each tire brand/model. The 40/44 pressures are for RE11 (Bridgestone).

In my opinion, the following DOT-R tires are garbage:

MPSC N-Spec
Yoko A048
Toyo R888
Pirelli Corsa System

 

I'm tracking the CS on its new RE-11s this week. I was planning on starting with cold temps of 30 all around...yes, no?

 

Yes, you can use the 305/30R19 RE11 on the rear, and a 255/35R19 in the front on RE-11 and stock wheels.

If you go with 255/35R19 and 305/30R19 RE11, drop the front of the car by doing 3 full turns down on the spring perches, and raise the rear by doing 3 full turns up on the spring perches. The front and rear ride height need to be adjusted. This will also change the toe settings, so set it to stock toe, I prefer a little toe-out in the front axle (live steering wheel and fast reacting) and factory toe-in at the rear (0.25 degrees per corner, 0.50 degrees total, same as 4mm total toe-in).

I currently run 255/35R19 RE11 front and 285/35R19 rear. The front 255 is too wide for my rear, so the car is on the oversteer side, not recommended. The 245/35R19 and 285/35R19 are the perfect combination for the Scuderia (no need to change anything). If you want to supersize, 255/35R19 and 305/30R19 will work on the stock wheels, but a minor ride adjustment and toe reset is required, but these wider sizes would offer plenty of more grip.

Once my rear tires wear out, I'm going to 305/30R19. Problem with RE11 is that they just don't want to wear out. My rear tires are 2 years old, they have done Sebring, Homestead, Daytona, autocrosses, drag races, and they are still thick and grippy. The front ones are just 1 year old, because I had a flat tire at Sebring, and decided to try the next bigger size (the flat was cause by a loose tire valve, not a tire failure).

 

Last time I was at the track with the Scuderia, I did a full day at Sebring on RE-11. Hot Florida day. I started at 30 psi front and 34 psi rear cold, pressure went up out of proportion, with rear tires reaching 50 psi.

Target hot pressures, 40 psi front and 44 psi rear, cold pressures, start at 32f/36r, but be sure to check tire pressures and bleed them if they get too high, most likely they will.

In my case, I gained 16 psi from cold to hot, but starting at 40-16: 24 psi on street tires will damage the sidewalls and reduce tires longevity.

 

Ok, thanks! (its 90s today, but supposed to be down to 70s on thur/fri, so they shouldn't spike up as much as you saw...)

 

How about 235/35R19 front and 305/30R19 rear on stock challenge style wheels on F430 coupe?

I'm worried that on these sizes, tire side walls might looked "clamped" with stockers.

If these fit I'm going to lower the front 3/4" and rear 1/2" and align 4 corners.

I think these setup will at least help fill the enormous fender gaps and improve stance and appearance that I'm trying to achieve, without resorting to aftermarket wheels. Also with just a modest drop, car will not scrape all over the place, as my car is street/highway use only.

F430GT, and others please, your thoughts...sorry for being slightly OT.

 

The only problem with 235 front and 305 rear, is adding understeer to a car that already understeers. 235/285 is a better combination for the F430.

If you want to fill in the fender gaps, add 15mm H&R spacers front and rear (they come with longer lug bolts), and drop the car 20mm front and rear (11 turns on the spring perches), the F430 will get on the Scuderia ride height.

Stock U.S. F430 ride height: Front: 139mm (+/-5mm), Rear: 161mm (+/-5mm)
Stock ROW F430 ride height: Front: 129mm (+/-5mm), Rear: 151mm (+/-5mm)
Scuderia Ride Height: Front: 114mm (+/-5mm), Rear: 136mm (+/-5mm)

 

Rad, thanks for all the info, you just saved me 6K $$ in wheels for the sake of wider tires.

I found these sizes in PSS, which combination would you recommend assuming PSS's will fit:

255/30ZR19 (Tire diameter is 25.1")
305/30ZR19

or

255/35ZR19 (Tire diameter is 26.0")
305/30ZR19

The first option seems closer to stock ride height, Thanks again.

 

The first option is the best.

255/30R19 and 305/30R19. No need to adjust ride heights, as the rake will stay within factory tolerance (the car will drop 5mm at the front and 10mm at the rear).

 

Yesterday I started with cold 34/34 and after 20 minute session the tires were at 40/40. Air Temps were in the 70s and even though I "thought" I did around 10 pretty hot laps, they only spiiked up 6 pounds of pressure due to heat...

Question: What is the "difference" in handling if I had put the rears at 44 hot? I want to learn/understand what higher or lower pressure does to handling.

Thanks in advance!

 

In general, higher tire pressures will make the tire "feel" stiffer as there will be less sidewall flex. This can also help if you have a lot of tire rollover (typically higher-profile, mushy tires), especially if you are camber challenged. You will notice this effect a lot more on the front tires in terms of steering response.

Also, I've seen on a lot of forums and the web, that higher pressure = more grip. That is not true, although manufacturers tend to run front tires under-inflated for a softer ride and added understeer. In general, tires have a need for the RIGHT pressure. Too low or too high, and they will not perform to their optimum. Also, each make/model of tire seems to have it's own favorite range of inflation pressures that it operates at best.

I like to use treadwear as well as an IR temp gauge to set correct tire pressure (especially the latter). IR temp gauges are cheap, and while the purists will insist on a tire pyrometer, I find that the IR gets me 90% there for 10% of the effort. Perhaps beyond the scope of this thread, if the tire's tread temps are higher in the middle than towards the sidewalls, then you are running the tire overinflated. If the center is running colder than the towards the sidewalls, then the tire is underinflated. If the inside is running hotter than the outside, then you are running too much camber, etc., etc. Make sense? You can pick up the IR gauges for pretty cheap. I find them very useful. Differences in treadwear will only show up over time, whereas the tire temps are right now. In general, you want even tire temps across the tread which indicates the load is evenly distributed. Now, when you measure (under what conditions) is another tangent depending on whether you are optimizing the numbers for street or track and what tradeoffs you want.

 

Thank you Sir.

 

Thanks F430GT.
I'm also looking at BFgoodrich Gforce T/A KDW it has 1 upsize pairing of 235/35R19 F and 295/35R19 R. but the thread design is too radical for my taste and you don't recommend them so I'm stiil searching for other options.

 

The KDW (2) is a good tire, but an old tire. Years ago, I put them on our family sedan and on my wife's SUV, for example I wouldn't recommend them either on your Ferrari.

Tire technology changes. The newer formulations are often superior. Stick with F430GT's recommendations unless you know better* and there is something very specific/different that you are trying to achieve. * Rad = Tire God

 

For those looking to up-size for more grip without any issues, here are the calculations using all possible MPSS combinations on the stock wheels (7.5" & 10"), most experts will recommend maintaining a variance of less than 4% from stock to keep the ABS system and suspension working properly.

Tire Size : Variance:
225/35-19 : Stock Front
235/35-19 : + 1.1%
245/35-19 : + 2.2%
255/30-19 : - 0.7% (Recommended)
255/35-19 : + 3.3%

Tire Size : Variance:
285/35-19 : Stock Rear
295/30-19 : - 3.3%
305/30-19 : - 2.4% (Recommended)

As per Rad's recommendations, 255/30-19 and 305/30-19 seem to be the best tires with the least variance from stock, I quickly gave up on the idea of upgrading to 20" wheels since matters are even worse on that scale.

As I recall from previous threads, the weight distribution on the F430 is 45:55 front to back. Fortunate enough, 255 and 305 are exactly 45:55 !!!

Thanks again everyone for all your input, can't wait for the new rubber.

 

Don't use 255/305 on 7.5/10 x19 wheels, these sizes are intended for the the Scuderia (the Scuderia uses a 8" front wheel).

On a 7.5" wheel I would not use anything larger than a 235, which means the rear tire cannot exceed 285 (to keep the balance).

So, for standard F430 or 360CS on stock wheels, MPSS: 235/35R19 and 285/35R19.

 

As already said it's very important anyway to take a close look to every tyre sheet,the new Pzero Trofeo R for example has the same circomference in 295/30/19 and in 305/30/19 (2090 mm).. the only difference being the width.. and in this case the tyre is quite smaller compared to the stock 285/35/19 (2155 mm)

 

Thanks for the correction Rad, too bad this setup will only work on the Scuderia wheels. I can't find a better combo on the stock F430 wheels, our options are very limited.

 

So for MSSP which one would you consider the best option on 16m wheels for track use? 235/35 front and 305/30 rear? or 245/35 front and 305/30 rear? Fede

 

MPSS 255/30R19 and 305/30R19 for Scuderia and 16M.

 

Hi Rad.....you always provide amazing info over and over again. I've researched your threads and am very appreciative for your help.

I have a CS and am looking at replacements for the Rossos and was sold on the RE-11's due to the availability of 235 35 19 fronts and 285 35 19 rears. You mention PSS in those sized but I cannot find 285 35 19's. Do you have a source for the MPSS's in that size?

cheers!
Jim