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I think I can explain at least part of the huge difference in indicated speed in STi's vs. other cars.

I did a radar/speedo check on my STi recently with brand new 235/45/17 tires (1.6% taller gear than stock 225/45/17). If the speedo was accurate, I should've been going 1.6% faster than my speedo indicated, but I was actually going 5% slower than the speedo indicated. So, assuming nothing changed from '04 to '05 model year on the STi, Brian's speedo was likely reading 6 to 7% higher than actual speed, meaning 80 mph on the speedo was really around 75 mph.

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Keith Q.
2008 Top Gun
http://www.youtube.com/watch?v=KmX8XuZ_DCo&NR=1

Yup. I used a GPS to check mine after I got a speeding ticket and it stated that I was going 4mph slower than indicated on my speadough.

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Silver Honda
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"Never let life be shaped by fear of its end"

No, you're a towel!

I think we're working along the same lines Dick. Just a different approach. Miles tried the Hawk HP+ and felt they were too instense. He felt he could lock up the car too easy. So he went with PFC-Z pads. Those are a fair bit better than the regular PFC pads but not as intense as the HP+. The regular PFC pads are supposed to be equivalent to OEM. The OEM C4 pads are semi-metallic. Nothing really special.

I was told that the HP+ wouldn't heat up enough in autocross and to use HPS. But the HP+ were free ( a popular tarheels price I would try HPS next time or Bobcat/Panther pads from Carbotech.

Keep in mind your formula car probably weighs half of the Vette. At the end of that straight section on the course I really missed the HP+. I tried deep braking once with the PFC pads and overshot the runway. Even though my R comps are pretty worn down I barely hit the ABS all day with the PFC pads. I would have engaged it with the HP+. On my car that isn't a bad thing. The ABS works quite well and I don't flat spot tires...

Graham

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http://www.greywinds.com

Graham,

Thanks for the feedback. I agree that we are on the same page . . . and that there are lots of options depending on the needs of the car.

FYI, I ran HP+'s one season on my formula ford. They are actually pretty much a high performance street pad meaning they work cold but have a higher cf (plus lots of dust) and also a higher max operating temp. Too aggressive for my car (no abs).

FYI according to GEEZ Miles and I saw peak braking g's of about 1 g. My 1100 lb ff routinely would show peak braking g's of 1.3 (slicks help a LOT when they are fresh and warm!).

Interesting stuff. I generally learn something new at (or after) every event, even after 30 years in the sport.

Dick (still lots to learn)

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Dick Rasmussen

FS 50 2018 Mustang GT

Dick, I now have time and can expand a little further on my brake comment.

The STi comes stock with 4-piston front and 2 piston rear Brembo brakes, along with slotted rotors. I've run Castrol SRF brake fluid from day one. My car has 16k miles on it. About 2 months ago I decided to try a series of 70mph to 40mph braking. After my fourth attempt or so I had brake fade. These braking manuevers were in rapid succession. Since the rest of my braking system should not be the weak link (well, no SS brake lines but their use for street and AutoX is arguable), I suspected the pads. I put the Bobcats in about 3 weeks ago and noticed an immediate improvement after I bed them in.

Fast forward to the T&T. I ran 5 events last year, my novice year. I'm far from smooth on the course and I ALWAYS brake too late and overdrive offsets, etc. So, my mod money for this season went to things that allow me to still jerk my car around (Much larger front sway bar, and an AutoX alignment to max out my front camber), and to brake like I always do but actually do it effectively. I still jerk my car around but had much better results through slaloms, lane changes, etc...the front sway and alignment helped out quite a bit. I also started my braking 'late' like I always do but noticed that I was slowing down too soon. I braked later and later with each run and only overdrove the following turn once. Plus, my braking at the offset on the left hand side on the main runway and my braking at the pivot cone in the slalom element was much better than last year.

So, since I don't have an actual before and after braking distance comparison I'll have to go by my 'feel', as subjective as that may be. I understand that tires have a lot to do with braking but I don't understand the dynamics that the size of the pads, the type/material of pads, the size of the calipers, the number of pistons, the rotors, etc, have to offer with braking. I'm just a weekend guy with NO mechanical aptitude and no previous experience with a car that allows me to have so much fun. If it 'feels's good I'm happy.

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