mdrums

Thanks Bob, This is why I run 245-40-18 and 305-35-18's they are right at the same diameter as my stock 19's. However I want to possibly use 255-35-18 and 315-30-18 and each tire will be .5-.8" smaller in diameter than stock but the ratio between front and rear will be in the 3% rule.

However I had some guys tell me that this could cause issues with PSM and ABS because the smaller diameter and speedo reading to the computer and so forth. I used the 255/315 size for almost 1 track day a few years ago but felt that braking was different and was not sure it was the pads glazing or the brakes/ABS Ice mode thing.

screech66

My stock wheels are 19" and tires are Pirelli but for the track I use 18" Fikse Profil 13 wheels and Hoosier R6's. I assume there would be some difference in diameter between the two. I can sort of see how the difference could confuse the ABS sensors, but would that show up as the ABS not activating at all? I have never once felt the ABS activate in this car, and there has been several times I have had to put a scary amount of pressure on the brake pedal to get slowed down. A couple of people have told me about a pocket of gas getting between the pads and the rotor. I believe as a result of over heating the pads, causing some gas to be emitted from the pads themselves. The Porsche technicians have not seen any indications of a problem with the ABS when they hook up with the computer. I should probably just put a new set of Pagid yellow's on and make sure to bed them properly and see if the problem goes away. Maybe I just glazed them.

obsessedone

I agree with Bob's logic that would seem F to R ratio would be the key. More importantly, actual experience seems to demonstrate this. After getting similar input from others, I switched to 18's this season with Hoosier 245-35 F and 315-30 R. In over 30 track days so far have had no ABS issues - only triggered ABS once, when I crunched the brakes suddenly to avoid a spin in front of me.

One caution when talking tire sizes - be aware not all manufacturers measure the same way based on actual tire comparisons. For example, a few weeks ago the fellow next to me on the paddock asked if I had considered going wider in front - he was running 255's. But later when we both happened to be changing tires we put them side by side and my "narrower" Hoosiers were virtually identical in width to his 255s. So I am not sure wider Hoosiers would fit - not really an issue for me as a like the current balance of my car but interesting. I thought the measurements were truly standardized, but side by side comparison shows they are not.

mdrums

Thanks!
I did run Toyo R888 255/35 and 315/35 18's no rubbing issue on my car and see a lot of GT3 997.1 cars at the track with this size.

obsessedone

Two other things about the 35 series F, 30 series R combo;
1- keeps ride level, but slightly lower than stock 19s
2- gives slightly lower gear ratio for a bit more acceleration - great trade off giving up a little top end speed, never been to a track that I could get anywhere near the cited top speed anyway - the acceleration is more valuable on the track

mdrums

Yep exactly why I tried this size a few years ago but only had 1 day on them and sold the wheels. Also this is why I am thinking of going back to this size.

I like the Toyo RA1's in 245-40-18 and 305-35-18 but they are not available in the 255-35-18 and 315-30-18 size, so I'd have to go with Toyo R888's and I am not sure I want to go back to R888's. I like the R888 stiffer sidewall but I do not like how they heat cycle out faster than the RA1's.

TRAKCAR

Toyo RA1 245F and 335R, no problem, but it looks like the rear like -2 Camber at most, at -2.5 rear I only use the inside 70% of the tire.

FWIW: With Hoosiers R6 they wore very even, corded the middle when they were done.
I will try less rear camber -2 / -1.8 to try and get wear even and take temp measurements next time. The fronts wear perfect at -2.5.

Pagid pads last 8-10 days if you flip the fronts after 4-5 days. I have 6 days on them now and will have 8-9 days after the next event. I will measure and report.

TrackDays247.com

El tippo:

Chamfer the LEADING edge of each pad - just the ONE edge of each where the rotor first "goes in to" as it rotates. Each particular corner of the car will be differently oriented.

10mm wide, 45 degree angle, using medium file, then round it off.

Made a HUGE difference on my cars with Pagids and is approved by Pagid.

marc a

I recently purchased a set of the 6 piston GT3 calipers and they arrived with a used set of the 29s. Thicknesswise they are almost new, however the face of each pad has some spider cracking and is shiny. I assume this is what the post above referred to as glazed. I have never used Pagid products so I am not familiar with this glazing issue.

Is there nothing that can be done to bring the pads back to life?

Thanks in advance.

Marc

_____________________
'00 Audi TT
'99 996 (Wife's ride)
'86 951 LS1 (C-2)
'77 911 3.2 (C-1) Gone but not forgotten.
3.2 Conversion and 915 Rebuild Home Page
The 958 Conversion
958 Track Video
PCA National Registry of Instructors

TrackDays247.com

Be really careful with the whole 'glazing' phrase...it is often overused. Chances are the Yellows need nothing done to them, whatsoever.

marc a

Craig,

Thanks, you are right, I used glazing because of the appearance of the pad surface. Here are pics of the pads. No flash was used. Any thoughts would be appreciated.

Marc
_____________________
'00 Audi TT
'99 996 (Wife's ride)
'86 951 LS1 (C-2)
'77 911 3.2 (C-1) Gone but not forgotten.
3.2 Conversion and 915 Rebuild Home Page
The 958 Conversion
958 Track Video
PCA National Registry of Instructors

TrackDays247.com

Looks pretty good. Edges aren't white, they must not have been used too hard quite yet -

mdrums

Pretty much what mine have always looked like

marc a

Thank you both . . . great news . . . . now my caliper purchase just went down by the cost of a set of pads.

Marc

_____________________
'00 Audi TT
'99 996 (Wife's ride)
'86 951 LS1 (C-2)
'77 911 3.2 (C-1) Gone but not forgotten.
3.2 Conversion and 915 Rebuild Home Page
The 958 Conversion
958 Track Video
PCA National Registry of Instructors