[glamcem]

Originally Posted by TrackClub

Of course he does, as he sends me a fat cheque every month for my presidential duties and membership is by invitation only

Btw you could mount a 325 on a stock 11 rim as that is still within specs. But you shouldnt mount a 305 on a 10 so 295 max, which would likely result in a bit of push, unless increased rake compensated for the change in balance.

But since you got a set of 19s (11/12 i presume?) those would be much better for dedicated track rubber anyway.

Cheers!

I wouldn't mind praise anyone for a fat check too..

I really considered getting ZLE size wheels since they are bit easier to work with and stretch the tires beautifully but other than the OEM 3R tires there are no good tire options to pick from :/ something like 305/325 or 315/335 like the 18" sizes .. I think 345s would still be beneficial for the ZLE but not so sure about the SS 1LE.. that being said a friend has been using 315/345 on both R888Rs and RRs and his lap times much improved with the extra rubber..of course it may be because on our cars with enough weight in the rear put enough traction even on the 325 tires whereas Corvette can break loose more easily

This is his PB with 325/345 RRs..1:46 is flying at the Ridge .. about the same lap time with Vipers, GT3 cup cars or Time Attack cars .. R888Rs are about 2-2.5 seconds slower. It's stock GS except forged wheels and ST43 pads and RRs of course

[TrackClub]

Originally Posted by glamcem

I wouldn't mind praise anyone for a fat check too..

I really considered getting ZLE size wheels since they are bit easier to work with and stretch the tires beautifully but other than the OEM 3R tires there are no good tire options to pick from :/ something like 305/325 or 315/335 like the 18" sizes .. I think 345s would still be beneficial for the ZLE but not so sure about the SS 1LE.. that being said a friend has been using 315/345 on both R888Rs and RRs and his lap times much improved with the extra rubber..of course it may be because on our cars with enough weight in the rear put enough traction even on the 325 tires whereas Corvette can break loose more easily

This is his PB with 325/345 RRs..1:46 is flying at the Ridge .. about the same lap time with Vipers, GT3 cup cars or Time Attack cars .. R888Rs are about 2-2.5 seconds slower. It's stock GS except forged wheels and ST43 pads and RRs of course

Well, the proviso is: one must be at the top of the laptime leader board to qualify (for praise)

Your friend knows how to wheel and how to get the most out of his equipment and that includes tires of course. The car is on the limit, yet well balanced and under control (due to his proactive corrections) and hence fast. A lesser driver would be in the weeds pdq. Obviously dot slicks will help him gain pace, as he knows how to get it out of the car.
I also suspect he is fast regardless. Just a hunch, as a GS- no matter on what tires - is no match for a well driven Cup car. That's for damn sure. Eagerly awaiting your laptimes once you get your new car and put RRs on it. I am sure it will be bags of fun

[seanblurr]

I just finished my second track day with 315/30/18 Nakang AR-1 tires. The car is SUPER loose. It was so hard to get the power down on corner exit. The tires seem pretty good, but the size is wrong for this car. I'm not sure square is the way to go...

[TrackClub]

Originally Posted by seanblurr

I just finished my second track day with 315/30/18 Nakang AR-1 tires. The car is SUPER loose. It was so hard to get the power down on corner exit. The tires seem pretty good, but the size is wrong for this car. I'm not sure square is the way to go...

I think you're the only zle owner trying to make a square set up work? It seems all models have different track widths, likely sway rates, maybe even rake and for sure ediff programs designed for incredibly well balanced cars out of the box. Changing things up will likely change handing handling characteristics especially if one pushes the car hard and visits its limit often. It is possible that those become more acute on one model vs another.

I recall Ryephile changing up sways for his ZLE rims with G3R set up to bring it back to neutral on his SS 1le?

When i ran square 295s on my car, they did well on a slower, twisty venue, but the rear would SKIP in mid corner phase when loads were much, much higher at Mosport. Not a pleasant feeling given speeds involved and something that had my attention in a big hurry. In comparison, with stock tire set up the car is very predictable, it can still cross the limit quickly, but it does so in a progressive fashion.

Cem, thinking about your C7 GS friend...it is hard to believe he runs a truly stock car with 325/345 tires, given a GS is already rather nervous with stock 285/335s. So increasing F tire width by a whopping 4 sizes from stock and R just by 1 size, should produce tons more oversteer.
Heck, it may even reverse the rake into a negative territory...Anyhow, whatever it is, i am glad it works for your buddy.

Cheers!

[Norm Peterson]

Originally Posted by TrackClub

Cem, thinking about your C7 GS friend...it is hard to believe he runs a truly stock car with 325/345 tires, given a GS is already rather nervous with stock 285/335s. So increasing F tire width by a whopping 4 sizes from stock and R just by 1 size, should produce tons more oversteer.

His hands did seem to be pretty busy much of the time . . .


Norm

[TrackClub]

Originally Posted by Norm Peterson

His hands did seem to be pretty busy much of the time . . .


Norm

Ha! Agree! But i think it was a result of him pushing the car pretty hard and making corrections to stay balanced vs the car being out of whack balance wise per se.
Just imo and obviously i am being an armchair expert here Cheers!

[glamcem]

Originally Posted by TrackClub

Well, the proviso is: one must be at the top of the laptime leader board to qualify (for praise)

Your friend knows how to wheel and how to get the most out of his equipment and that includes tires of course. The car is on the limit, yet well balanced and under control (due to his proactive corrections) and hence fast. A lesser driver would be in the weeds pdq. Obviously dot slicks will help him gain pace, as he knows how to get it out of the car.
I also suspect he is fast regardless. Just a hunch, as a GS- no matter on what tires - is no match for a well driven Cup car. That's for damn sure. Eagerly awaiting your laptimes once you get your new car and put RRs on it. I am sure it will be bags of fun

I was thinking the same until very recently after comparing my friend's Z06 lap time to brand new GT2RS that's driven with Australian Stig they used cheater tires when they hit those below 7 mins lap times at Nurburgring (with both GT2/GT3RS) when a regular Cup 2 tires used..

For the reference my other friend (not in the video) did 1:48 with 315/345 RRs and GT2RS did 1:45 with Cup2s (driven by pro, race winner driver I mentioned above) I will find and add his video.

GT3cup car (previous gen) with another pro deiver was doing 1:45 something at the Ridge and as you can see it's almost neck to neck..that GT3cup car was a race winner car also..but maybe the driver factor I don't know

Originally Posted by TrackClub

Cem, thinking about your C7 GS friend...it is hard to believe he runs a truly stock car with 325/345 tires, given a GS is already rather nervous with stock 285/335s. So increasing F tire width by a whopping 4 sizes from stock and R just by 1 size, should produce tons more oversteer.
Heck, it may even reverse the rake into a negative territory...Anyhow, whatever it is, i am glad it works for your buddy.

Cheers!

Sorry for the typo, I meant to say 315/345

For the reference they both (GS and Z06 guy) run the same size wheels 18x11 F/ 19x13" R. Speaking of oversteer, since most factory cars come with a slight understeer (for liability purposes I believe bc it's safer for general audience) the rule of thumb is slightly increase the front track to make it neutral.. I was trying to do that with my previous 1LE but my rear balance was most likely out of whack because of the weird offsets (18mm outward) luckily we now have better offsets for rear so I will see how it goes this time. I will be technically holding the rear but slightly adding more track to the front this time. Once I am sure about the 18" fitments, I think I will just order a custom 18" wheels perfect fitment.

[GunMetalGrey]

Originally Posted by glamcem

My pleasure
Are you guys coming to the ORP this year? I have tons of data points (from many different tires and cars with rather consistent and experienced drivers in similar conditions) at there as it's our home track and can gladly share and talk more in detail if/when you come.

They have 20" OEM sizes for RR just so you know.
Our first scheduled is a month from now but it will give me enough time for sway bar install, wheel studs, knuckle grinding etc...

we might go to ORP, however it’s my brothers first year tracking his newly acquired 2017 mustang GT 350 R with a Pro charger supercharger on it, so I think he will have his hands full just learning the local track, it will also be my first track season using R compound tires. I have a feeling that once this track season is over we will be looking to start experiencing some different tracks.

Originally Posted by TrackClub

Btw you could mount a 325 on a stock 11 rim as that is still within specs. But you shouldnt mount a 305 on a 10 so 295 max, which would likely result in a bit of push, unless increased rake compensated for the change in balance.

But since you got a set of 19s (11/12 i presume?) those would be much better for dedicated track rubber anyway.

Cheers!

Yes I do have a set of 19x11 and 19x12’s coming in April!

The only OEM 20 inch size I can see at TireRack in the Toyo RR is the 285/30/20 so I’m not sure if it would good to pair that up with a 325/30/20 in the rear ( I wonder if that 1 inch difference in tire diameter would be an issue not to mention the potential understeer?) or if it would be better to go with a 285/35/20 front tire which would be close in diameter to the rear but 1” off the original diameter of the front?

Originally Posted by glamcem

:
This is his PB with 325/345 RRs..1:46 is flying at the Ridge .. about the same lap time with Vipers, GT3 cup cars or Time Attack cars .. R888Rs are about 2-2.5 seconds slower. It's stock GS except forged wheels and ST43 pads and RRs of course

That’s a very significant improvement over the R888R’s!
I’m officially interested in getting a size combo that works and trying these tires out myself.

[TrackClub]

Cem, i am aware that most production cars come with a slight understeer, but frankly so do race cars and an oversteering pig will be much harder to push and hence slower. These are not my words btw, but GT world champion's, who wrote an excellent book on performance driving. And these are not just his words either, but also other top tier pros. Not suggesting an understeering pig is fast, but a very slight balance to understeer is better vs the other way around.
That aside, i have a few friends with C7s and those cars are rather nervous at the limit. Something that has been confirmed by Randy Pobst each time he tested one. At the same time each time he drove a gen6 Camaro, he marveled about thier balance. And let's face it the dood knows his cars
Now 315/345 combo your friends run, would up the F rubber by 3 sizes, while upping the R size by just 1 size.
That in itself would further increase oversteering tendencies by a lot.* But that's not all, as thier 18/19 wheel combos would also increase the stock rake from 0.9 to a whopping 1.7, which would also add much oversteer in itself.
So, none of that makes sense to me, unless they made changes to suspension components to neutralize the balance.

GT2RS (991) is almost 5 secs faster vs C7 Z06 and over 8 secs vs C7 GS at Laguna. And just less than half a sec slower than McLaren Senna and less than half a second faster vs Viper ACR...Different days, but the same driver (Randy). These are 1:30s laps, so shorter vs your track. I suspect slicks would reduce this gap by say 2-3 seconds, but no tire would produce an 8 second gain on such a lap. Miracles don't happen. Speaking of which, i passed a McLaren 600LT last year (had to work hard for it), but we all know that an SS 1LE stock aint even remotely close to that car's capabilities. And i know that, as when Scott Goodyear drives one, he passes me like i am standing still. Quite literally!
Ive also equaled a famous Porsche factory driver's time in my C5Z at a local venue a few years ago. He was in a new GT3. But it wasn't his car, he was no doubt learning the venue as he went and i am sure he wasn't pushing 10/10ths. All i am saying, the fact that some dood in a GT2RS posts a YouTube vid does not mean this is what the car can really do. Ditto Cup race cars that weigh 2600lb and have a weight to power ratio of 5.7. Whoever drives these, if all they can do is equal a stock GS on DOT slicks (not even full slicks!) is not pushing the car to its limits. I routinely play with local club racers on Hoosiers, not because my car is faster, but because they dont push the tires far enough and i actually catch up under braking and in corners. On street G3s.
All this is not to take away from your friends fine driving ability, or the fact that sticking slicks on a car won't make it faster. And obviously the formula is working well for them, which is great! But a GS aint a match for a GT2RS no matter the tires.

GMG, a GT500R with a blower...wow! Yep, this will be a handful for a novice. And costly on gas.Tell him to watch oil level. Some of these cars consume tons of it based on my bud's experience.

I would not run 285/325 on stock rims as it would jack up the rake and possibly make electronics unhappy. Just a quess. I would not run 285 square with a taller tire in the rear either. Running 295 true square is ok (except i dont like it in high speed sweepers, but you dont really have any at your track) as that lowers the rake and hence brings the balance more towards neutral. Less rake = more stability everywhere. More rake = more oversteer, especially on entry and mid corner (as the higher the rear sits wrt the front, the faster it wants to rotate). Track width F vs R also plays a role here balance wise. Something to be aware of re your 19 rims depending what offsets you got. FYI: R888R are not in the same league as DOT slicks. They are much closer to our G3 than the latter. Also, not much love for them where i run. Basically previous old compound with a stiffer sidewall and less wet capability. I know of only 1 person who runs them and he is sponsored by Toyo (read: free tires). A friend ran them on his ZL1 for a bit, but has since switched to G3Rs (and proly tripled his tire budget lol!).

Cheers!

Ps This is what i call a pre spring silly season lol!
And btw dont forget to also have a plan to mod the nut behind the steering wheel. The most reliable, fastest, cheapest and most fun way to cut seconds off your laptimes

[Norm Peterson]

On the matter of 'rake' . . . I suspect that it's not the rake per se that's affecting the understeer-oversteer handling balance, but changes in the front vs rear geometric roll center heights that necessarily accompany any changes in rake (or just ride height, for that matter). A higher geo-RC will transfer more load than a lower one, and RC load transfer happens much more quickly than load transfer developed through chassis roll. The roll moment would remain the same because no adjustment is being made between the geo-RCs and the chassis/its CG, and with an increase in rake caused by taller tires you're getting a little more rear LLT from the unsprung mass effect.

Rake would be a visual indication of sorts regarding what might have been done to the Geo-RCs.


Norm

[glamcem]

Originally Posted by GunMetalGrey

The only OEM 20 inch size I can see at TireRack in the Toyo RR is the 285/30/20 so I’m not sure if it would good to pair that up with a 325/30/20 in the rear ( I wonder if that 1 inch difference in tire diameter would be an issue not to mention the potential understeer?) or if it would be better to go with a 285/35/20 front tire which would be close in diameter to the rear but 1” off the original diameter of the front?

I should've looked again and told you the exact sizes, my bad

Toyo RRs have 285-315-325/30/20 sizes so I would consider 285 front and 315 in the rear, if you want to be able to use them on OEM wheels. It's only marginally taller than the OEM tires (27.2" vs 27.5") ..I personally wouldn't mind adding a slight bit of rake as our cars are prone to understeer and as I'd be already adding more rubber in the rear it would definitely take care of that slight oversteer concerns because of that marginal addition of a rake (if any)

https://trackdaytire.com/product/toyo-proxes-rr/

My friends and I have been using RRs on summer/track season (April to October) here in PNW to drive around town and go to and come back from track. They don't HC out with street/highway driving and that's the beauty of them. My friend who used in his GS says he was able to get 4-5 events and 4-5k miles street driving. For track use we typically get 20-25 HCs and then the performance degrades and we retire tires. So they don't cord before they HC out.

[glamcem]

Originally Posted by TrackClub

Cem, i am aware that most production cars come with a slight understeer, but frankly so do race cars and an oversteering pig will be much harder to push and hence slower. These are not my words btw, but GT world champion's, who wrote an excellent book on performance driving. And these are not just his words either, but also other top tier pros. Not suggesting an understeering pig is fast, but a very slight balance to understeer is better vs the other way around.


That aside, i have a few friends with C7s and those cars are rather nervous at the limit. Something that has been confirmed by Randy Pobst each time he tested one. At the same time each time he drove a gen6 Camaro, he marveled about thier balance. And let's face it the dood knows his cars
Now 315/345 combo your friends run, would up the F rubber by 3 sizes, while upping the R size by just 1 size.

That in itself would further increase oversteering tendencies by a lot.* But that's not all, as thier 18/19 wheel combos would also increase the stock rake from 0.9 to a whopping 1.7, which would also add much oversteer in itself.
So, none of that makes sense to me, unless they made changes to suspension components to neutralize the balance.

Man that's a lot of reading, I thought I was too descriptive

Edit: I noticed that I didn't pay attention to the rake numbers, when calculating rake, we don't compare the overall diameters of say 18 vs 19" tires, for the actual ride height difference we use radius, in other words half the difference so the rake itself would be affected about .4 not .8"..that's very negligible in you think about in grand scheme of things, after a few sessions the weight in the gas tank would also affect some ride height difference too for instance

Keep in mind there are two things that are important if we're speaking Corvettes:
1- They're front and rear height adjustable and I have no doubt they neglected the consider all these factors and adjust the rake if it causes any issue. The guy in the video below (C7 Z07) is OCD about those details and would probably spend much more time than any of us, trust me
2- 345 RR tires in the back especially on a 13" wide wheels is quite a bit of tire. They swear their cars are very balanced not "piggy oversteer" or anything, adding some rake to a factory car wouldn't add tons of oversteer but maybe light oversteer which can be addressed with some alignment, height, tire pressure adjustments. For the reference, OEM C7 Z07 wheels and tires are 19x10 and 20x12 (vs 19x11 and 19x13" on their cars).


The guy in the first video (C7 GS) is the fastest among all of us, he's the local go kart champ, races with Miata and many other cars and has been tracking with his Lotus and Corvettes for years... They race with a Miata and shared stints with Randy Pobst too ..and guess what, they're lap times were identical at the Ridge.. that's not to say, they're in the same league with one and only Randy Pobst of course, just to give you an idea how much time they spent on that track and experience on different cars

GT2RS (991) is almost 5 secs faster vs C7 Z06 and over 8 secs vs C7 GS at Laguna. And just less than half a sec slower than McLaren Senna and less than half a second faster vs Viper ACR...Different days, but the same driver (Randy). These are 1:30s laps, so shorter vs your track. I suspect slicks would reduce this gap by say 2-3 seconds, but no tire would produce an 8 second gain on such a lap. Miracles don't happen. Speaking of which, i passed a McLaren 600LT last year (had to work hard for it), but we all know that an SS 1LE stock aint even remotely close to that car's capabilities. And i know that, as when Scott Goodyear drives one, he passes me like i am standing still. Quite literally!
Ive also equaled a famous Porsche factory driver's time in my C5Z at a local venue a few years ago. He was in a new GT3. But it wasn't his car, he was no doubt learning the venue as he went and i am sure he wasn't pushing 10/10ths. All i am saying, the fact that some dood in a GT2RS posts a YouTube vid does not mean this is what the car can really do. Ditto Cup race cars that weigh 2600lb and have a weight to power ratio of 5.7. Whoever drives these, if all they can do is equal a stock GS on DOT slicks (not even full slicks!) is not pushing the car to its limits. I routinely play with local club racers on Hoosiers, not because my car is faster, but because they dont push the tires far enough and i actually catch up under braking and in corners. On street G3s.
All this is not to take away from your friends fine driving ability, or the fact that sticking slicks on a car won't make it faster. And obviously the formula is working well for them, which is great! But a GS aint a match for a GT2RS no matter the tires.

Yes, I am aware of those lap times too but like I said above. In those tests GT2RS had Michelin Pilot Sport Cup 2 R N0 tires. However, when they use same Cup2 tires that lap time difference is smaller (so 5 seconds of difference would be maybe 2-3 seconds which also aligns with his data) . Of course GT2RS will always be faster but I think you missed the part when I said the guy who drove the GT2RS was a pro racer (they say Aussie Stig IIRC) not just some random dude on youtube and more importantly was on regular Cup2s not on those cheater tires I know, achieving the car's full or (9/10ths of potential) takes a lot of time for drivers like us but for a pro racer it only takes half a day maybe.

My friend was still 3 seconds behind that GT2RS. That wouldn't make him a pro driver but since this is our home track and he's also an instructor with tons of seat time on this track (including races), I think they're lap times would be pretty consistent. Lap times prove that too.

This is him doing the 1:48 at the ORP with RRs. The pro racer who did the 1:45 in a GT2RS was driving in 43F Ambient temps which is very close to his conditions (45F)

I would not run 285/325 on stock rims as it would jack up the rake and possibly make electronics unhappy. Just a quess. I would not run 285 square with a taller tire in the rear either. Running 295 true square is ok (except i dont like it in high speed sweepers, but you dont really have any at your track) as that lowers the rake and hence brings the balance more towards neutral. Less rake = more stability everywhere. More rake = more oversteer, especially on entry and mid corner (as the higher the rear sits wrt the front, the faster it wants to rotate). Track width F vs R also plays a role here balance wise. Something to be aware of re your 19 rims depending what offsets you got. FYI: R888R are not in the same league as DOT slicks. They are much closer to our G3 than the latter. Also, not much love for them where i run. Basically previous old compound with a stiffer sidewall and less wet capability. I know of only 1 person who runs them and he is sponsored by Toyo (read: free tires). A friend ran them on his ZL1 for a bit, but has since switched to G3Rs (and proly tripled his tire budget lol!).

Cheers!

Please see above post for my correction of the tire sizes, 285/315.. not 325..it's still is also available but I agree it would be a bit too tall for being 20" I guess

Ps This is what i call a pre spring silly season lol!
And btw dont forget to also have a plan to mod the nut behind the steering wheel. The most reliable, fastest, cheapest and most fun way to cut seconds off your laptimes

You know, it's a never ending process

[GunMetalGrey]

Originally Posted by Mountain

That would be them.

https://www.bmrsuspension.com/?page=...1686&desktop=1

I think I’m going to order those BMR spherical bushings and try them out at the start of the track season and report back here after some events in March.
While I’ve never used the SC3Rs before, my SC3’s corded on the inside well before the outside shoulder had been significantly worn, though my alignment had gone to hell from either poor alignment shop work or 8 track days without realigning the car.

I’m a bit confused still though, if this “dynamic toe change” is what causes the insides of the Goodyear SC3 and SC3R tires to cord prematurely, shouldn’t this happen with other R compound tires as well? Does it?

I only seem to recall the outside edges of R7 cording prematurely without sufficient camber but don’t recall the inside edges being an issue and Id think this problem would effect all tires, perhaps not equally, but to some degree..

Granted I never really used to pay a lot of attention to where the cording was happening on the tires I was reading about, only how long it would take for them to cord.

[GunMetalGrey]

Originally Posted by TrackClub

GMG, a GT500R with a blower...wow! Yep, this will be a handful for a novice. And costly on gas.Tell him to watch oil level. Some of these cars consume tons of it based on my bud's experience.

I would not run 285/325 on stock rims as it would jack up the rake and possibly make electronics unhappy. Just a quess. I would not run 285 square with a taller tire in the rear either. Running 295 true square is ok (except i dont like it in high speed sweepers, but you dont really have any at your track) as that lowers the rake and hence brings the balance more towards neutral. Less rake = more stability everywhere. More rake = more oversteer, especially on entry and mid corner (as the higher the rear sits wrt the front, the faster it wants to rotate). Track width F vs R also plays a role here balance wise. Something to be aware of re your 19 rims depending what offsets you got. FYI: R888R are not in the same league as DOT slicks. They are much closer to our G3 than the latter. Also, not much love for them where i run. Basically previous old compound with a stiffer sidewall and less wet capability. I know of only 1 person who runs them and he is sponsored by Toyo (read: free tires). A friend ran them on his ZL1 for a bit, but has since switched to G3Rs (and proly tripled his tire budget lol!).

Cheers!
)

It’s a GT350R so he’s also got to get used to tracking in a manual (Though he did buy an auto blip for it) and yes it’s going through gas like crazy!

Yeah I know R888Rs are not great for the track and are similar to the SC3 and that’s why I’ve never considered using them (just like I no longer want to use the SC3 anymore despite your high praise for it when it is usually referred to as a street tire including Randy Probst) but 2.5 seconds faster per lap for the RR is significant considering they are cheaper and in the context of seeming to also have a compound that is easy to warm up, which made me question their ultimate grip when up to temp.
perhaps it simply gave me low expectations for those RR’s which then turned to being pleasantly surprised to hear they were 2 to 2.5 seconds faster per lap.

What Do you think about running a 285/35 front and a 325/30 rear?