GT4 autocross
09-20-2015, 11:15 PM
#46
Rennlist Member
FWIW she found that having the tire pressures closer felt better to her. About +1-2 in the rear.
I had a lot of understeer problems in my GT3 today until I dropped my fronts down to 29-30 range from 31-32. Night/day difference, even my student riding passenger was surprised. I suspect the GT4 may be at home in the 29f/30r range.
Her tire temps at stock were about even in the back but +2C on the inside of the front (even middle/outside) after coming back to the paddock. I think the front could do with a lot more negative camber.
I had a lot of understeer problems in my GT3 today until I dropped my fronts down to 29-30 range from 31-32. Night/day difference, even my student riding passenger was surprised. I suspect the GT4 may be at home in the 29f/30r range.
Her tire temps at stock were about even in the back but +2C on the inside of the front (even middle/outside) after coming back to the paddock. I think the front could do with a lot more negative camber.
09-23-2015, 04:33 AM
#47
Three Wheelin'
I don't view 3psi as a small difference.
This may be surafce dependant, but what do you shoot for in terms of hot pressures having had some time to digest ?
This may be surafce dependant, but what do you shoot for in terms of hot pressures having had some time to digest ?
12-08-2015, 05:43 PM
#48
Subscribed! Will be autocrossing when I get mine in June. I will run in SS for SCCA, so locally I can run the stock tires,
or 200tw alternatives. Does anyone have feedback on how the stock tires would compare to the recent crop of sticky
extreme '200tw' tires? I also considered lowering the gearing by going to 19" wheels with other tires...
or 200tw alternatives. Does anyone have feedback on how the stock tires would compare to the recent crop of sticky
extreme '200tw' tires? I also considered lowering the gearing by going to 19" wheels with other tires...
12-08-2015, 10:56 PM
#49
19" is probably a good idea. The rear is the hard part, because clearing the toe link in the rear while staying with an 11" wheel and 1/4" offset is tough.
12-09-2015, 01:52 AM
#50
Rennlist Member
Joe -- I think the Bridgestone RE-71R is about 1 second faster on a 60 second course than the Michelin Pilot Sport Cup2s on the car.
19" is probably a good idea. The rear is the hard part, because clearing the toe link in the rear while staying with an 11" wheel and 1/4" offset is tough.
19" is probably a good idea. The rear is the hard part, because clearing the toe link in the rear while staying with an 11" wheel and 1/4" offset is tough.
12-09-2015, 03:06 AM
#51
Good report, thanks! Nice driving as well!
That's def a faster layout than im used to. The layouts I've run have lots of hairpins and lots of off-camber sections as well.
I can't wait to get my GT4 and see for myself how it performs in AutoX.
That's def a faster layout than im used to. The layouts I've run have lots of hairpins and lots of off-camber sections as well.
I can't wait to get my GT4 and see for myself how it performs in AutoX.
12-09-2015, 12:14 PM
#52
Quite possible for autocross. I've heard more than one tire tech insider say
that they have the ability to make tires do whatever they want just about,
and pass/claim whatever treadwear ratings needed for the moment. In the
80's they would underrate the wear for the competition-favored tires to
attract customers who thought low-wear-numbers meant better stick.
And the stock Porsche tires, however better they are for track work, have
to be 'colder' than an autocross tire so they don't overheat and get greasy
on track. Autocrossers want a tire that will come to the best heat/stick in
15 seconds and hold it for 10 minutes at 60 degrees outside for the next
run. Folks would rather have sticky hot tires they have to spray down between
40-second runs, rather than not-yet reaching full stick.
that they have the ability to make tires do whatever they want just about,
and pass/claim whatever treadwear ratings needed for the moment. In the
80's they would underrate the wear for the competition-favored tires to
attract customers who thought low-wear-numbers meant better stick.
And the stock Porsche tires, however better they are for track work, have
to be 'colder' than an autocross tire so they don't overheat and get greasy
on track. Autocrossers want a tire that will come to the best heat/stick in
15 seconds and hold it for 10 minutes at 60 degrees outside for the next
run. Folks would rather have sticky hot tires they have to spray down between
40-second runs, rather than not-yet reaching full stick.
12-09-2015, 12:38 PM
#53
SportCup2 have a 180 tread wear rating, and they last a long time. Tread wear ratings are pretty much open to the manufacturer.
Take the Kumo Ecsta V720. They have a 200 tread wear rating, yet the Viper ACR Extreme just set 13 track records on them.
Take the Kumo Ecsta V720. They have a 200 tread wear rating, yet the Viper ACR Extreme just set 13 track records on them.
12-09-2015, 03:38 PM
#54
Is there some sort of group approach we can take toward asking Bridgestone when/if/how soon
they plan to make the perfect RE-71R tires for our 8.5"x20" and 11"x20" wheels? There seems to
be exactly zero 20" stock-competitive autocross tires...
they plan to make the perfect RE-71R tires for our 8.5"x20" and 11"x20" wheels? There seems to
be exactly zero 20" stock-competitive autocross tires...
12-09-2015, 10:09 PM
#56
12-09-2015, 11:36 PM
#57
Burning Brakes
What ExMB is trying to say is that they're actually adaptive transmission mounts. These are standard on all GT4s, regardless of whether you tick the SC option box or not.
12-11-2015, 04:21 PM
#58
Addict
Rennlist
Lifetime Member
Rennlist
Lifetime Member
http://www.bridgestonetire.com/customer-care/contact-us
I talked to them a month or two ago about GT3 sizes and they said they had plans to introduce 20 more sizes in the RE-71R over the next 6 months.
If you like Nitto NT01 for the track, call them too: Nitto Consumer Relations, 888-529-8200 Monday-Friday 8:00 am - 5:00 pm (Pacific Time) or use their online size request form: http://www.nittotire.com/find-a-tire...t-a-tire-size/ They have only three 20" sizes available, one of which might work for rear tires, but nothing for the front of the GT3/GT4. They need a shorter 255/35 or a 245 in about a 27" diameter.
TT
12-11-2015, 04:30 PM
#59
Rennlist Member
Call them and ask. The more people requesting 20" sizes the better.
http://www.bridgestonetire.com/customer-care/contact-us
I talked to them a month or two ago about GT3 sizes and they said they had plans to introduce 20 more sizes in the RE-71R over the next 6 months.
If you like Nitto NT01 for the track, call them too: Nitto Consumer Relations, 888-529-8200 Monday-Friday 8:00 am - 5:00 pm (Pacific Time) or use their online size request form: http://www.nittotire.com/find-a-tire...t-a-tire-size/ They have only three 20" sizes available, one of which might work for rear tires, but nothing for the front of the GT3/GT4. They need a shorter 255/35 or a 245 in about a 27" diameter.
TT
http://www.bridgestonetire.com/customer-care/contact-us
I talked to them a month or two ago about GT3 sizes and they said they had plans to introduce 20 more sizes in the RE-71R over the next 6 months.
If you like Nitto NT01 for the track, call them too: Nitto Consumer Relations, 888-529-8200 Monday-Friday 8:00 am - 5:00 pm (Pacific Time) or use their online size request form: http://www.nittotire.com/find-a-tire...t-a-tire-size/ They have only three 20" sizes available, one of which might work for rear tires, but nothing for the front of the GT3/GT4. They need a shorter 255/35 or a 245 in about a 27" diameter.
TT
Sorry new to this game( GT4 ) i.e some say wider wheel in front, smaller width in the rear, vs stock to help with understeer