SCCA Solo C Street Discussion

[ButteR]

In the world of autocross, how much does offset affect performance on our cars. The RPF1 has an offset of +42, OEM wheels +48 and the other popular aftermarkrt light weight wheel (I forget the name) +50.

A few years ago, the +/- 6 wheel offset was illegal in street classes, so I'm assuming that there must be some advantage to wheel offset.

I was reading about scrub radius, but it didn't seen to me that increasing or decreasing it would have a significant impact on performance with the +/-6 wheel offset limitation that were restricted to in street class

[veloscaraptor]

Originally Posted by SeanRTR

The BEST place to get an alignment is here:


V2 Motorsports


He's a small race only shop, does tremendous work, probably not the cheapest, probably not the closest.


http://v2motorsports.com/index.html

Thanks! I'll check them out. An hour and a half drive isn't ridiculous for good work.

[markw]

Originally Posted by veloscaraptor

Hi all. Super noob question, sorry in advance.

I just got my fr-s, and am planning a return to autocross (been away for ~4 years) in CS. I'm currently looking at wheels; does it make sense to grab a small (5mm) spacer for a +50 offset wheel? Or should I just run them as is? Or should I just run stock wheels until i can find rpf1s (or similar) in stock?

Thanks!

Do it right, order a set of RPF1's and RE71R's in 225/45-17 before you drive the car off the lot. That's what I did but tires were Z2's at the time. No messing with wheel spacers, the RPF1's are hub centric to our cars and look great. The quality of the wheels will be remembered long after the price is forgotten. If you swap a lot you'll be cursing wheel spacers. Especially since that may mean longer studs.

Mark

[Laloosh]

Solo...have you ever put the car on a rack? I have the same gauge and plates and mine is .4-.5 degrees off.
it's very consistent, just off by .4-.5 from the rack.

Edit: I measured only in my garage and always zero out. Have not tried this anywhere else. Next time Im on the rack I'll bring it with me to compare.

[simpleisbest]

Originally Posted by Laloosh

Solo...have you ever put the car on a rack? I have the same gauge and plates and mine is .4-.5 degrees off.
it's very consistent, just off by .4-.5 from the rack.

Unless you got the professional equipment (rack, etc...) and dead level floors, I've heard home alignments are best get to get things "close" to where you want them.

I use my trackside alignments to make set-up changes for testing, but follow-up afterward with a proper alignment.

While most DIY equipment may not the greatest accuracy, they sure can be used to measure how things changed.

So from solort's post, we learned that the TRD springs give about 0.2 to 0.3 degrees of neg camber

[Laloosh]

Exactly....which is nothing...also wondering if he accounts for his weight. Throw his weight in there an he loosing .2ish on the drivers side.

[solort]

Originally Posted by Laloosh

Exactly....which is nothing...also wondering if he accounts for his weight. Throw his weight in there an he loosing .2ish on the drivers side.

Just sharing my measurements and observations. My camber is maxed, my toe is adjusted where the car handles great, and I am pleased with my new pre-owned FRS. I look forward to meeting many of you at Nats. I hope to trophy again this year...

[Blue Gt]

Ok so we just installed TRD springs on the blue 2013 FR-S. Ride height change was -20 mm in front and -25 mm rear. Front camber went from -1 degree to -1.2 degrees (each side) and we have crash bolts installed. Rear camber went from -1.2 degrees to -1.8 degrees on each side. But I do not have the best available camber gauge.

What a royal pain in the ass this was, I could not find a 17 mm spark-plug socket anywhere in the USA. Ended up using a short socket and pipe wrench or channel lock pliers on sockets to loosen / tighten the strut lock nuts. It's Miller time boys! DP

[markw]

Pass through socket sets are your friend.

I've got the gearwrench 8921 pass through socket set, which I picked up just for doing struts. 30 minutes on each front, rear took a tad bit longer as you need to disconnect the swaybar and then pull the cross bolt for the arm to hub so you can droop the arm far enough to get the strut out.

I also have the "flying miata" jack adapter to jack the car up on the seam. This works great to get one corner or both tires off the ground.

[SeanRTR]

Quick summary of tire test


BFG Rival-S 215/45/16 (23.6 inch diameter) (yes 16's) on 16lbs +48 wheels
vs.
Bridgestone RE71R 235/45/17 (25.4 diameter) on 15lbs + 42 wheels


These tires both measure about 8.5 inches in width mounted on the rim FYI


Saturday was a Pro Solo (concrete) (our local region does one every year) 30 second course, drag style 0-60 start before fast slalom, 180 degree long sweeper, and some off sets and sweepers on the way back. Top speed 60-62 MPH. This was geared perfectly for the tall Bridgestones, and the times showed.
Tried BFG's 36 PSI and then 32 PSI. 32 PSI was quicker, best times of 30.3 and 30.5, all over the limiter in second, or shift to third on one spot.
RE71R's, at 29F 32 R = 29.5 on each side, just barely hitting the limiter in one spot only. Call it .8 advantage for the Bridgestone. Slaloms in the BFG didn't feel great, but it got through just fine, acceleration off the line is great. The 180 degree sweeper felt HORRIBLE. Turn-in was slow, I expected slow, but I couldn't even place the car where I needed to at speed, ultimate mid corner grip simply was not there.


Sunday: Super tight local BS event (asphalt) , with three super tight turns, that lead into WOT straight sections, with a 4-5 cone slalom to finish that could be taken flat if done correctly. Top speed on this course was only about 50 MPH at best, and the tight turns should have made it perfect for the short 16 inch Rivals. However, again the tight sweepers were totally vague feeling, and ultimate grip mid corner simply was not there. People say these tires start to slip, and then you just give them more input and they grip again....well that shit doesn't work. These tires are simply inferior (at least in this size). I got down to a 29.5 on the Rival-S on this course, and it felt like it wasn't easy....yet the course was super easy. I was running 31ish PSI square. I then tried 42 Psi front, and 38 PSI rear, and it didn't help and went .7+ slower. I swapped to the B-stones for the final two runs. The car was way out of the powerband for all three hair pin turns, and felt slow as shit, but it was super easy to drive, and the first run matched my Rival-S time at 29.5 I was confident I would have beat that time by a tenth or, but some broad wanted to go for a ride so I accepted, and ran a 29.7 on the final run. I'm not sure if the tire size doesn't work, or the compound doesn't work....but something clearly doesn't work at all. Does anyone think the 6mm difference in offset could be effecting anything? STS Civic/CRX drivers were doing the Rival and B-stone testing on Saturday as well, and they had different results. One was faster on B-stones, and one was faster on Rivals. The B-stones car won on Saturday, but the Rivals car won on Sunday. (they are comparing 225/45/15 Rival-S vs. 205-50-15 RE71R)


The Rival-S are working for other people...but they sure as shit didn't work for me. I don't get it. Either that tire size (215/45/16) is simply too short (23.6 inches), and gives up too much contact patch, or something about the Rival-S compound just doesn't work that well on our cars. I really wanted this tire to work, because I hate the Bridgestones. They tires are completely brainless. They literally suck the joy out of competitive driving for me. I'm on the fence for going to nationals. I feel like I need a car that makes 50-100% more power (or weight or both) to actually have something that's challenging and therefore fun to drive.

[renfield90]

Originally Posted by SeanRTR

I'm on the fence for going to nationals.

That's too bad; after that review I was really looking forward to beating you on Rivals.

[TMF]

Originally Posted by SeanRTR

The Rival-S are working for other people...but they sure as shit didn't work for me. I don't get it. Either that tire size (215/45/16) is simply too short (23.6 inches), and gives up too much contact patch, or something about the Rival-S compound just doesn't work that well on our cars. I really wanted this tire to work, because I hate the Bridgestones. They tires are completely brainless. They literally suck the joy out of competitive driving for me. I'm on the fence for going to nationals. I feel like I need a car that makes 50-100% more power (or weight or both) to actually have something that's challenging and therefore fun to drive.

Well I haven't even driven my FRS on an autox course yet, but I can at least compare the raw data:

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
215/45-17 3.8in 12.3in 24.6in 77.3in 819 0.0% (stock size)
215/45-16 3.8in 11.8in 23.6in 74.2in 854 -4.1%
235/45-17 4.2in 12.7in 25.3in 79.6in 796 2.9%
225/45-17 4.0in 12.5in 25.0in 78.5in 808 1.4% (size that I will be running, but I don't have any other tires to compare).

So I think you're right, the Rival's might just be too short due to their size. I'm hoping that the 225 Stone is right in the sweet spot in terms of gearing and responsiveness.

I don't get why people don't like the Stones? They seem to be THE fastest tire on the market this year. Is this the same reason why some people don't like GTR's - they are just too "easy" to drive?

And with regard to your last comment, I'm making the opposite switch...I just sold my 400+ whp SM STI (not full prep, but you get the idea) for my FRS. I wanted something more competitive for it's class, RWD, and something with a lower "limit" that you could easily drive at the absolute limit.

I guess the sun is always brighter on the other side. Perhaps you may want to consider a C5 Z06...double the HP of the FRS, about the same price, and still very competitive in AS.

BTW, thank you very much for providing the test results with the times!

[chucky12012]

Originally Posted by SeanRTR

Quick summary of tire test

I feel like I need a car that makes 50-100% more power (or weight or both) to actually have something that's challenging and therefore fun to drive.

I get what you are saying that it isn't a true street tire, but at the same time your comments can come across as arrogant. Not every car is fun for every driver, but to say there is not challenge is what I might expect from someone running away with a class nationally...

I'm excited to run in another huge nationals class, hopefully not dropping the ball like last year while doing so! Almost hitting 50 registered already is awesome in my book. That alone should give you all the challenge you could want. I mean, this might make more sense if you were running a Spyder in ES... ugh.

[vroom4]

My thoughts exactly.