[TrackClub]

Originally Posted by TheRealJA105

I get what you are saying, but I'll stick with tires being the easiest way to greatly affect handling. Also i'd wager to say tires are also the cheapest way for a Manufacturer to improve handling. They are only putting tires on once and don't really care about the consumable price. Compare the price difference in up sizing 2 front tires 20mm vs a couple hours in GM Engineering time and they are saving money immediately.

This math would only work if a manufacturer produced and sold a single car vs 10s of thousands per year

Retail difference between 245 and 265 4S is about $50 per tire. So $100 for 2 fronts. Let's say a manufacturer wholesale cost is half of if. So $50 for 2. Dont forget a manufacturer doesnt get tires for free eh?

Multiply it by a number for a given model sold over say a 6 year period and you're into millions of dollars of extra INCREMENTAL cost to a manufacturer. In comparison, an engineer's time would cost GM a couple of hundred bucks. But, as GM would use an engineer already on a payroll, the incremental cost to them would be ZERO.

I obviously agree that changing tire sizes will have an effect on handling. But i disagree that this is a cheapest way. Most definitely NOT for a manufacturer. And not even for any of us frankly. Want less understeer? Put a spacer up front and increase front track width. Or, stiffen rear bar. One change. One cost. Done. Compare it to buying bigger rims and bigger tires and the latter is by far much more expensive over the life time of a track going car. Unless one does it to run tires that wear like iron and reduce consumables costs this way. The reason Provoste did it to run RS4s, which made perfect sense.
Note he didnt do it to "fix" anything, or to get faster per se. And of course another reason is to go faster on stickier tires and Provoste also had a set of rims for slicks. And that has worked for him too, for pace. But note he didnt upsize anything and the slicks were 275 or 285 square i believe? Yet they were good for an amazing 2:04 pace at the Glen in otherwise STOCK 1le.

Looping back to the C8: that 2 time NASA guy (vid) wheels it pretty good and says no understeer. And even Randy says understeer is largely fixed with more camber and what he REALLY focuses his feedback on is off throttle mid corner OVERSTEER in fast sweepers. You dont solve it with increasing F tire sizes for damn sure! You solve it best with ediff calibration, as he has wisely noted.

And since i am on a roll here With several noted exceptions (you are one of them) most folks are nowhere close to being able to push their cars to the limit, as far as skill is concerned. And while playing with set up and tires may yield some improvement (including placebo effect), by and large they would be much better served spending money on seat time and coaching.

Cheers!

[TheRealJA105]

You def got me on my math, i didn't think that one through before i posted it.

However, tires will make a way more drastic change than anything you listed (spacers, swaybars, rake) though all are effective.

I didn't watch the videos, maybe i need to before I make anymore dumb comments






I should have just said... APRIL FOOLS!

[TrackClub]

Originally Posted by TheRealJA105

You def got me on my math, i didn't think that one through before i posted it.

However, tires will make a way more drastic change than anything you listed (spacers, swaybars, rake) though all are effective.

I didn't watch the videos, maybe i need to before I make anymore dumb comments






I should have just said... APRIL FOOLS!

Haha! Good deal!

[glamcem]

Originally Posted by TrackClub

This will be one expensive experiment Cem
Thanks for reminding me about your build thread. Cheers!

oh this is nothing compared to my last Miata "project", lesson learned. I sold the OEM Wheels and tires so only have two sets of wheels and tires (and the 18*10" that I will list for sale soon) I'm not too worried about consumable costs since 18" tires are typically much cheaper and I will need to get tires every 3-4 events anyways (assuming I can get 16-18 HCs out of SC3Rs like people say)

[glamcem]

Speaking of wider wheels and tires cost, manufacturers already add at least $4-5k for GS cars and additional
$7-8k for Z07 package on top of that.

Speaking of adding -3.0 camber to C8, it sounds more like a band aid solution as in almost all the magazine tests use street and performance alignment with about -2 degree camber, -3.0 drastically higher than those numbers so I'm not surprised it alleviates some of that issue .

Let's wait and see what the new C8 GS car will offer and how much of a difference it can make. I say it may be huge like it was on C7.

[TrackClub]

Originally Posted by glamcem

oh this is nothing compared to my last Miata "project", lesson learned. I sold the OEM Wheels and tires so only have two sets of wheels and tires (and the 18*10" that I will list for sale soon) I'm not too worried about consumable costs since 18" tires are typically much cheaper and I will need to get tires every 3-4 events anyways (assuming I can get 16-18 HCs out of SC3Rs like people say)

Haha! I can well imagine what your Miata project was like As far as tires: so have you given up on RRs?

[TheRealJA105]

I think he's given up on the 295 RRs. He's going to run 315 square with his new 10.5 front rims.

[TrackClub]

Originally Posted by TheRealJA105

I think he's given up on the 295 RRs. He's going to run 315 square with his new 10.5 front rims.

I am confused, as Cem talks about G3Rs not RRs.
And i dont think G3R is made in 315/18?
I thought the whole point was to test out RRs, given the G3R is a very well known tire by now incl rim set ups.
Oh well, i am sure Cem will chime in here shortly...

[glamcem]

Sorry for the confusion, I have just updated my build thread. I didn't give up on RRs, I just want to see how the 315 SQ RRs would stack up against to 305 SC3Rs. SC3Rs might still be slightly faster but I have some other tires in the list after RRs and it looks like some additional grinding helped and I can fit 315s up front too

With the last car I wasn't able to run 18x10.5" +22 wheels even with 8mm spacer, it was slightly rubbing to the knuckle when I test fitted. Thanks to additional grinding/welding, I can now fit with only 5mm spacer. In the old car I had -3.0 camber though, currently have -2.8 , that should help a bit too.

Since I couldn't drive the RRs more than one session, I think the difference should be still less than 2 seconds, if I could get used the car (since I am no robot lol). I hope next time I can do another test to see how the 315 SQ will be against 305 SC3Rs. I think it would be a better test since 305 SC3Rs already run wider than 315 Toyo RRs.

[TrackClub]

Originally Posted by glamcem

Sorry for the confusion, I have just updated my build thread. I didn't give up on RRs, I just want to see how the 315 SQ RRs would stack up against to 305 SC3Rs. SC3Rs might still be slightly faster but I have some other tires in the list after RRs and it looks like some additional grinding helped and I can fit 315s up front too

With the last car I wasn't able to run 18x10.5" +22 wheels even with 8mm spacer, it was slightly rubbing to the knuckle when I test fitted. Thanks to additional grinding/welding, I can now fit with only 5mm spacer. In the old car I had -3.0 camber though, currently have -2.8 , that should help a bit too.

Since I couldn't drive the RRs more than one session, I think the difference should be still less than 2 seconds, if I could get used the car (since I am no robot lol). I hope next time I can do another test to see how the 315 SQ will be against 305 SC3Rs. I think it would be a better test since 305 SC3Rs already run wider than 315 Toyo RRs.

So you did test RRs on your original staggered rim set up, but only one session? What happened? Then you switched to 305 square G3Rs? Now you will test 315 square RR? You're going for a big trophy payday? Lol

[glamcem]

Originally Posted by TrackClub

So you did test RRs on your original staggered rim set up, but only one session? What happened? Then you switched to 305 square G3Rs? Now you will test 315 square RR? You're going for a big trophy payday? Lol

I tried to describe all that in my build thread. You didn't read the link that I've shared with you, did you?

I think the staggered setup would be great for the OEM suspension/ARB rates but with the sway bars, it felt like I can benefit from even more tire after trying the 305 SC3Rs. I don't think it was just the tire because I noticed that at the very first lap with the SC3Rs at the first couple of turns. Turn in was much quicker and car was easier to rotate. The sway bars were like "give me more rubber I can handle it" That's the reason why I want to try SQ setup (well not exactly since fronts will be 10.5" and rears 11" but almost SQ) on 18" set. I love RRs they're amazing tires maybe not as quick as SC3Rs but I feel with SQ setup it will be very close.

[TrackClub]

Originally Posted by glamcem

I tried to describe all that in my build thread. You didn't read the link that I've shared with you, did you?

I think the staggered setup would be great for the OEM suspension/ARB rates but with the sway bars, it felt like I can benefit from even more tire after trying the 305 SC3Rs. I don't think it was just the tire because I noticed that at the very first lap with the SC3Rs at the first couple of turns. Turn in was much quicker and car was easier to rotate. The sway bars were like "give me more rubber I can handle it" That's the reason why I want to try SQ setup (well not exactly since fronts will be 10.5" and rears 11" but almost SQ) on 18" set. I love RRs they're amazing tires maybe not as quick as SC3Rs but I feel with SQ setup it will be very close.

Cem, you're right, i didn't read your offered link until now. Apologies!

Very interested in your tire tests regarding longevity, especially RRs.

As far as pace comparisons, a single session after a long winter, with a fastest time being on a first lap, seems a bit "unfinished" imo. Too bad you didn't put RRs back on after testing the G3Rs having had a bit of seat time to shake the cobwebs out and get used to a new car again. Nevertheless, interested to see how 315s do for ya.

Regarding your "previous car" suffering from "horrible understeer", the Miata was that bad, eh?

Do you have a PDR? I hope so! Your current overlay provides extremely limited data* regarding driver inputs.
Speaking of data, i would not automatically discount the optimum laptime as a software error. It may not be exactly accurate, but it may be damn close! And if you dont find an error, well, then you got something to aspire to!

Anyhow, big thanks for posting all the info, nice pix and the vids. Always fun to watch and especially nowadays. Btw what's with those hand shuffles? To borrow a quote "this may get you into trouble one day"

Here's to 1:49s next time out!

Cheers and stay safe.

[glamcem]

Originally Posted by TrackClub

Cem, you're right, i didn't read your offered link until now. Apologies!

Very interested in your tire tests regarding longevity, especially RRs.

As far as pace comparisons, a single session after a long winter, with a fastest time being on a first lap, seems a bit "unfinished" imo. Too bad you didn't put RRs back on after testing the G3Rs having had a bit of seat time to shake the cobwebs out and get used to a new car again. Nevertheless, interested to see how 315s do for ya.

Regarding your "previous car" suffering from "horrible understeer", the Miata was that bad, eh?

Do you have a PDR? I hope so! Your current overlay provides extremely limited data* regarding driver inputs.
Speaking of data, i would not automatically discount the optimum laptime as a software error. It may not be exactly accurate, but it may be damn close! And if you dont find an error, well, then you got something to aspire to!

Anyhow, big thanks for posting all the info, nice pix and the vids. Always fun to watch and especially nowadays. Btw what's with those hand shuffles? To borrow a quote "this may get you into trouble one day"

Here's to 1:49s next time out!

Cheers and stay safe.

Let me clarify, best lap didn't happen in the first lap when I had the RRs. It was in the afternoon session with the SC3Rs.

I was referring to previous 1LE, sorry should've been more clear 1LE with sticky Trofeo Rs had pretty noticeable understeer (caused by body roll) and thankfully sway bars seem to take care of that. Miata didn't have turn in or body roll issues after all those suspension and chassis mods but it was a twitchy with snap oversteer at times. I think the combination of shorter wheelbase and lack of a good LSD (like eLSD) had to do with that. 3,600lbs Camaro gives me more confidence

I don't have PDR, there were 2 1LEs in my area when I am looking in 500 mile radius and both of them didn't have that. Although, it was nice to be able to record with an integrated system video quality was pretty bad for today's standards and very dark. I actually have no issue with the current layout as I already have all the information I have and I can see the steering input as the camera shows the interior.

If I want to move the camera to the windshield, I think I can add that information (steering input) in OBD2 channels. Optimum lap time on the RaceChrono app is definitely a glitch. It uses the best sectors from different laps but since my external GPS didn't work for a while it's possible that it merged or neglected some information. I have seen this happening in the past.

Speaking of 1:49s, I think that's a bit hard to reach since my PB was 1:54.5 at the same place and I already improved that about 2 seconds I am hoping I can shave another second or two but anything below 1:50 is Z06, GT3, Viper territory (or a heavily modded track car)

Are you referring to my hands not being on 9:15 at all times? if so, it happens... you may as well see that in some GM nurburgring tests, Randy Pobst's videos or Time attacks too, on cars with shorter steering racks like an S2000 or Evo I didn't need to move my hands as much of course

[TrackClub]

Originally Posted by glamcem

Let me clarify, best lap didn't happen in the first lap when I had the RRs. It was in the afternoon session with the SC3Rs.

I was referring to previous 1LE, sorry should've been more clear 1LE with sticky Trofeo Rs had pretty noticeable understeer (caused by body roll) and thankfully sway bars seem to take care of that. Miata didn't have turn in or body roll issues after all those suspension and chassis mods but it was a twitchy with snap oversteer at times. I think the combination of shorter wheelbase and lack of a good LSD (like eLSD) had to do with that. 3,600lbs Camaro gives me more confidence

I don't have PDR, there were 2 1LEs in my area when I am looking in 500 mile radius and both of them didn't have that. Although, it was nice to be able to record with an integrated system video quality was pretty bad for today's standards and very dark. I actually have no issue with the current layout as I already have all the information I have and I can see the steering input as the camera shows the interior.

If I want to move the camera to the windshield, I think I can add that information (steering input) in OBD2 channels. Optimum lap time on the RaceChrono app is definitely a glitch. It uses the best sectors from different laps but since my external GPS didn't work for a while it's possible that it merged or neglected some information. I have seen this happening in the past.

Speaking of 1:49s, I think that's a bit hard to reach since my PB was 1:54.5 at the same place and I already improved that about 2 seconds I am hoping I can shave another second or two but anything below 1:50 is Z06, GT3, Viper territory (or a heavily modded track car)

Are you referring to my hands not being on 9:15 at all times? if so, it happens... you may as well see that in some GM nurburgring tests, Randy Pobst's videos or Time attacks too, on cars with shorter steering racks like an S2000 or Evo I didn't need to move my hands as much of course

Yeah i know the new PB was on G3Rs, but i was actually referring to your best lap on RRs. But, i agree a better comparo between them will be with RR square in 315.

Very surprised you found your previous 1LE understeering severely on Trofeo Rs, as many run stock suspension on other sticky tires with no such issues.
So this is a bit of a mystery to me. But, be it as it may.

Got ya re the PDR. One crucial trace that's missing from the vid is brake input. At least i cannot see it anywhere
And without it, it is impossible to ascertain how a driver manages weight transfer on entry.

You are correct: i dont know how your laptimer works. I was drawing an optimistic conclusion recalling your C7 GS buddy doing a 1:46? But quite possibly maybe i got venues mixed up here. Still, first track day of the season, new (to you) tires, more pace is in the bank so keep pushing and wishing ya best of success

As far as 9-3 hand position: i know Randy doesnt keep them fixed all the time (and that's not ideal by any means, yet he can drift a car with one hand lol!) and Jim Mero used to be rather sloppy in his Ring vids (but not the Camaro guys). Bottom line if one pushes a car real hard and needs to execute a full lock correction, that can be a difference between success vs weeds. Anyway, sometimes folks do it without being aware of it, so i thought I'd mention it. But, no worries!

Next, a new C8 vid and going back on topic lol!