John's CS BRZ progression

[Biggins]

I'm glad to hear I'm not the only one who likes the Perrin bar.

I really like my Yokohamas and did not want to make a switch, but do you think the 245/40 set-up feels okay? I know your results were better, but the feel too (if that makes sense)? With the splicing I'm getting on the Yokohamas, I'm tempted to pick up some RS3s since it's hotter now and I have a co-driver.

Also, did you or your tire shop have any issues mounting the 245 RS3s on the skinny rim? I assume no fitment issues up front? I have the Kosei +50 with a 5mm spacer currently.

[AustinTX]

I felt like the car drove great on the wider tires. Coming from the 235 Z2's, I would say the tire squirm is about the same. In the end, I would run the tire/size that makes the most grip before I would make a tradeoff for feel or precision. Not sure I'm there yet based on a sample size of only 2 sets of tires, but the pace is closer to where it needs to be now.

I've got plenty of shock clearance with the RPF1's at +42. Tire fitment onto the wheel is the tire guy's concern

[piknockout]

Glad to hear the car is feeling/doing better. Hope to see you stick with it and not jump ship to the 370Z. Of course, you guys could bring both cars and decide which one to drive after looking at the courses. Just saying.

[AustinTX]

Originally Posted by piknockout

Glad to hear the car is feeling/doing better. Hope to see you stick with it and not jump ship to the 370Z. Of course, you guys could bring both cars and decide which one to drive after looking at the courses. Just saying.

Both cars will be there almost certainly - he's signed up already with #99

[Kido1986]

So he's the reason I had to borrow my codrivers magnets for Nats lol. 99 went quickly.

[AustinTX]

Had another good day yesterday. No changes from last week aside from trying out lower front tire pressure. I ran 39lbs up front for the first 2 runs and went down to 35lbs for the last 2. I did not notice a difference, but the last times were better. Probably just normal progression. I ended up 4th in X class and 5th in PAX. I coned away half a second on the last run (below), which would have moved me up to 3rd. I didn't know I hit the cone until I saw the results. The car is good and fun to drive now

Pax results:
https://axwaresystems.com/axorm/file...event6_pax.htm

Video of coned run, just clipped the final cone on course exiting the box:
[ame="https://www.youtube.com/watch?v=r1B5OYULcHQ"]CS BRZ at Spokes 06/29/14 - YouTube[/ame]

[automatic]

Do you envision that the front shoulder wear will be an issue in the long run? Specifically with shoulder wearing before the tire heat cycles out or tread is used?

[AustinTX]

I fully expect that any strut based street class car on street tires being used for autocross will wear the outside shoulder significantly faster than the center of the tire. I usually change tires long before they get below 4/32nds anyway

With that said, my 75 run 235 Z2's had VERY even tread wear when I sold them at 5-6/32nds. I expect the RS3's will wear the shoulder much faster due to the flatter tread profile. Either way, I will buy the tire that makes the car the fastest.

[bimmer635csi]

Originally Posted by AustinTX

Either way, I will buy the tire that makes the car the fastest.

How do you test for this? I barely have enough time to swap out a driver and bleed off air in between runs.

[7thgear]

Originally Posted by bimmer635csi

How do you test for this? I barely have enough time to swap out a driver and bleed off air in between runs.

your placement on the totem pole is generally a good indicator of your car setup, especially if you have other experienced competitors always coming out, so the difference between your time and theirs could be an indicator of improvement.

[bimmer635csi]

Originally Posted by 7thgear

your placement on the totem pole is generally a good indicator of your car setup, especially if you have other experienced competitors always coming out, so the difference between your time and theirs could be an indicator of improvement.

I agree. John does very well in autocross, especially compared to a scrub like me.


I was just curious how he was doing tire tests to find the fastest tire. Maybe I'm being too "engineer", but to run the same car on different tires 6 months apart doesn't make for a very direct comparison.

[7thgear]

Originally Posted by bimmer635csi

I agree. John does very well in autocross, especially compared to a scrub like me.


I was just curious how he was doing tire tests to find the fastest tire. Maybe I'm being too "engineer", but to run the same car on different tires 6 months apart doesn't make for a very direct comparison.

you misunderstood


when I was on stock tires, I was roughly 2-2.5 seconds behind my target competitor


after I upgraded my tires, I started to get the same times and sometimes faster.


Since the rest of my car didn't change, one could safely assume that the tires provided the decrease in times.


If I buy a different set of tires, and I start to be 1 or 1.5 seconds faster than my target competitor, then that means this tire is even faster than the other tire.


etc.


so the point is to have your targets and measure yourself off them, it's not super accurate (since they could have a bad day) but in general it's the best that you can do without testing equipment.


There is one competitor in my series that I know if I'm within half a second of him then I'm scoring in top 10, I don't even need to look at the results, just keep track of his

[TrqlessWonder]

Originally Posted by bimmer635csi

I agree. John does very well in autocross, especially compared to a scrub like me.


I was just curious how he was doing tire tests to find the fastest tire. Maybe I'm being too "engineer", but to run the same car on different tires 6 months apart doesn't make for a very direct comparison.

Relative pax position changes is a valid way to indicate. I'd be looking for a stronger signal under that scenario to prove it to me, though, as things do change (whether we made a change or not. I re-align my car twice a year mostly for this reason) and the competitor list and skill level is not the same from event to event. That is, if I only picked up one spot in Pax, I don't think I can confidently conclude that one was better than the other.

As for testing tires on the same day, some of those people just put in the extra effort. Not unusual for serious people at nationals to swap tires between drivers for every run. It can be done in 5 minutes if you have grid help. So, there's that possibility. Maybe make the change in between morning/afternoon run sessions?

You can also attend an actual test and tune event, where pulling out of grid for 15-20 minutes for a tire swap is no big deal. Or, you can sort of fake a TnT on your own at the end of the day if the club you're with usually does fun runs. That does require some extra money to have multiple sets of wheels and tires all ready to go, though.

Both relative pax and actual back-to-back times are reasonable ways to try to judge that. Back-to-back is just a little more direct where you are measuring on the same course, and same day, on different tires, whereas pax position is comparing your performance against a group of competitors versus your performance against a hopefully similar group of competitors.

[AustinTX]

Originally Posted by bimmer635csi

How do you test for this? I barely have enough time to swap out a driver and bleed off air in between runs.

Like others have said, I am comparing to known fast guys within my region. I'd also like to say that having a codriver at local events doesn't always work out in your favor for the reason you stated. Hard to focus on your own development when you are busy supporting someone else's efforts between runs. That, plus street tires don't really like the extra heat generated by double driving. Best to drive alone unless your codriver is providing good course feedback, good driving feedback, or the car