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Tracking / Autocross / HPDE / Drifting What these cars were built for!


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Old 11-05-2019, 04:41 PM   #4915
Takumi788
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Originally Posted by Icecreamtruk View Post
I havent mess with 17" vs 18" on wheel size, but I have tried 235/40, 235/45, 245/40, 245/45 and 255/40 tires on 17x9 wheels.
Now this this the type of discussion I was hoping to open up.

Did you record speed via GPS or Wheel speed?

255/40/17 are a lot cheaper than 265/35/18 so I would like to keep using them but the question has me curious.

The 17x10 idea is interesting too.
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Old 11-05-2019, 04:43 PM   #4916
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I think this is very dependent on the track(s) that are being driven as well. I don't run brake cooling ducts at all and haven't overheated the brakes. With that being said, I do have the PP Brembo's, so that likely helps with better thermal capacity than the stock brakes.

The Verus kit is great though and not very expensive.
True, it depends on the track but it also depends heavily on the driver. To be fair, I have evolved as a driver and use my brakes better now than I did 3 - 4 years ago. Most likely I was using my brakes too much when I first got the car.

The last time I boiled the fluid was at Sebring 3 years ago, top speed was 120 but I was over 100 in several areas. That was DTC-60 pads and Motul 660 fluid.

This year I went to Daytona with 2 heavy baking zones back to back, 125 MPH and 140 MPH. DTC-60 pads, Motul 660 AND Verus cooling ducts, no issues.
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Old 11-05-2019, 04:54 PM   #4917
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Originally Posted by Takumi788 View Post
Now this this the type of discussion I was hoping to open up.

Did you record speed via GPS or Wheel speed?

255/40/17 are a lot cheaper than 265/35/18 so I would like to keep using them but the question has me curious.

The 17x10 idea is interesting too.
I've had lower lap times on a 235/45/17 vs a 245/40/17 on 17x9 wheels, same track (PBIR) 2 months apart. My laptop crashed and I lost all my data so I can't help you there.

A proper analysis to determine if a 10mm wider tire will significantly lower lap times is doable but complex and requires lots of data management and reference points. You also have to optimize tire temps and alignment to truly know the benefit of the extra width. I'd be a fun experiment if you can afford it.
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Old 11-05-2019, 04:57 PM   #4918
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Verus cooling ducts, no issues.
Did you have to eliminate the windshield washer reservoir with that kit?
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Old 11-05-2019, 05:29 PM   #4919
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Did you have to eliminate the windshield washer reservoir with that kit?
Not that I know of, no

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Old 11-05-2019, 05:32 PM   #4920
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Not that I know of, no

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ok great. The Verus site said yes but that seemed odd
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Old 11-05-2019, 05:39 PM   #4921
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I've had lower lap times on a 235/45/17 vs a 245/40/17 on 17x9 wheels, same track (PBIR) 2 months apart. My laptop crashed and I lost all my data so I can't help you there.

A proper analysis to determine if a 10mm wider tire will significantly lower lap times is doable but complex and requires lots of data management and reference points. You also have to optimize tire temps and alignment to truly know the benefit of the extra width. I'd be a fun experiment if you can afford it.
Track temps alone could be the difference here. Not to mention driver consistency and other obvious variables.
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Old 11-05-2019, 05:47 PM   #4922
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ok great. The Verus site said yes but that seemed odd
I'm incorrect. 100% on me. It does need to be "eliminated", but could likely be relocated with a little work.

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Old 11-05-2019, 05:52 PM   #4923
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Did you have to eliminate the windshield washer reservoir with that kit?
Either removed, relocated or replaced. I had a reservoir from PTuning, sold it when I installed the supercharger (I removed the cooling ducts and installed a BBK).
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Old 11-06-2019, 02:31 AM   #4924
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Originally Posted by Takumi788 View Post
I am in the market of a new set of wheels so I have been thinking about switching from 255/40/17 to 265/35/18 for the increased contact patch on my track only FRS.

Is the extra weight (23 lbs more total), extra height (+.3" dia.) & cost ($389 more per set of tires) worth the extra 10 mm of tire when considering ultimate grip and lap times?
It depends on the track, as well as your car. At the minimum, you'll gain steering response and heat capacity.
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Old 11-06-2019, 02:32 AM   #4925
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OK good to know. My fronts just get so damn hot on track days. Smoking if I dont do some cool down time
You should always cool down. Use temp paint on rotors and temp strips on calipers to track peak heat.

You can also run pads that inherently run cooler.

Avoid ABS use if possible.
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Old 11-06-2019, 02:46 AM   #4926
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Originally Posted by Takumi788 View Post
Now this this the type of discussion I was hoping to open up.

Did you record speed via GPS or Wheel speed?

255/40/17 are a lot cheaper than 265/35/18 so I would like to keep using them but the question has me curious.

The 17x10 idea is interesting too.
Two laps for you. For this purpose, compare corner exit speed, vs speed at end of straight.

My video is a 100% stock engine with 18x9.5 TE37Saga with 255/35/18.

Sonny's video is on Ace/E85, with 255/40/17 on 17x9.

For example
Phil Hill apex speed
Me: 78
Sonny: 74
Vmax before Sweeper (corner after straight post phil hill)
Me: 101
Sonny: 106
Sweeper exit apex speed:
Me: 70
Sonny: 66
Vmax before Sunset (esses after sweeper are WOT, then straight to Sunset)
Me: 106
Sonny: 113
Sunset apex speed:
Me: 67
Sonny: 62
Vmax before Sunrise (sunset -> front straight -> Sunrise)
Me: 102
Sonny: 109

Obviously part of this vmax difference is the power and weight difference of the cars, but it does partially illustrate cornering speed gains vs straightline speed gains. Sonny's overall lap is 1.2 seconds faster.

[ame]https://www.youtube.com/watch?v=ax09vTphw3c[/ame]

[ame]https://www.youtube.com/watch?v=-zgIvxVT4ok[/ame]
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Old 11-06-2019, 09:23 AM   #4927
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Originally Posted by CSG Mike View Post
Two laps for you. For this purpose, compare corner exit speed, vs speed at end of straight.

Obviously part of this vmax difference is the power and weight difference of the cars, but it does partially illustrate cornering speed gains vs straightline speed gains. Sonny's overall lap is 1.2 seconds faster.
Thanks for the comparo. Super interesting stuff.

I'd also like to add that Apex has confirmed they are working on a 17x9.5 set in GT86/BRZ specific fitment to add to the confusion of wheel choices Maybe this will bridge the gap between the 17's and 18's.
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Old 11-06-2019, 10:02 AM   #4928
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Thanks for the comparo. Super interesting stuff.

I'd also like to add that Apex has confirmed they are working on a 17x9.5 set in GT86/BRZ specific fitment to add to the confusion of wheel choices Maybe this will bridge the gap between the 17's and 18's.
Yes, im waiting on this for now since I broke two of my wheels I'd rather get a wider 17" set and compare back to back with that as well.

@Takumi788 Speed was measured by GPS on a datalogger (cant trust speedo with different diameters).
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