Ford Focus ST Forum banner
141 - 160 of 168 Posts

·
Registered
Joined
·
938 Posts
Will probably add a touch of front toe-out before the Packwood Championship Tour now that I'm trusting what the rear will do. Not that turn-in is slow, but I found I would get behind in steering if I wasn't paying full attention, so a little sauce to make up for my own shortcomings.

After the Tour, I'll likely try some spring adjustments (front & rear) in conjunction with swapping to the Strano rear swaybar on soft.
I have a rear tower brace, since it's multi-functional for use with hauling stuff around as well. The rear always seems to 'take a second' to get planted with the separated rear spring set-up. I found I really liked it when I was prepared for a hard corner, but I absolutely hate how much time you will/could lose when it is a 'less smooth transition' and body roll becomes a massive shift in balance/weight.

Again, I'm set for more 'all-around' and just need to figure out where to focus when it's more tarmac oriented. The rear is one thing, my coilovers are valved way off from the spring ratio (yeah, all bought as a package that came from Taiwan so I guess it's no surprise!). I'm gonna add a larger front sway bar in an attempt to settle the rear and balance them via softer dampening with harder chassis, if that makes sense. Lots of runs need to be made indeed! I'm still in testing mode after 2 months, lol.
 

·
Registered
Joined
·
1,386 Posts
Discussion Starter · #142 ·
The photographer (Brent Remillard) was hoping to catch Pepper tripoding. He let me know this was my last run on Saturday, so I've been able to pinpoint the data in Solostorm.

The pic is probably 0.66G lateral and 1.00G combined axes (e.g. throttle shifting weight to the rear), 48.0 mph. Rear wheel lift probably occurred a car length back, so at 48 mph and 15 Hz GPS, that's roughly 56 inches per tick, so three ticks back is a car length. Solostorm says 0.64G lateral and 0.86G combined axes at three ticks back.

There's a possiblity wheel lift was earlier, while braking, but that's another car length further back and I don't think the experienced photographer using rapid fire would have missed a wheel lift by 2 car lengths.

393105
 

·
Registered
Joined
·
1,386 Posts
Discussion Starter · #143 ·
Ack! Aaargh!

Front brake pads started groaning already, telling me end-of-life and I don't have any spares for this weekend's competition. Making frantic phone calls and hoping $$$ will get me something in hand so I can at least participate on Sunday.
 

·
Registered
Joined
·
1,386 Posts
Discussion Starter · #144 ·
Pads made it here 8p. Just finished dinner, so going to try installing them, but don't have exactly correct brake piston retractor tool, so this may be a fight. If successful tonight, then I'll be setting my alarm clock for 3:30a to make it Packwood by 7a.
 

·
Registered
Joined
·
938 Posts
Wake up!! It's time to go race =-D I think you're 2 hours behind Central time, so yeah... I hope you got it all sorted and get to go light up the track today!
 

·
Registered
Joined
·
1,386 Posts
Discussion Starter · #146 · (Edited)
Wake up!! It's time to go race =-D I think you're 2 hours behind Central time, so yeah... I hope you got it all sorted and get to go light up the track today!
Took about an hour to change pads & tires. Normally I would change tires on site, but with the hot weather forecast and silly early alarm clock, I opted to change them at home & leave them on.

Suspension-wise, I'm all set for the Packwood Championship Tour in two weeks. After the Tour, I'll explore another setup change, losing some swaybar stiffness and replacing with spring rate.

Speaking of tires, by next season I think I'll be on Yokohamas. The more national-level results I see in STH, the more it looks like that is the tire and I'll just have to adapt my driving and setup to accomodate them. Likely fitment issues with the Falkens also forces my hand, though a hybrid setup of Falkens in front and Yokohamas in the rear is not out of the question.
 

·
Registered
Joined
·
1,386 Posts
Discussion Starter · #147 ·
How much acceleration is lost due to ambient temperature? How much acceleration is lost after several runs?

Well, I've got some acceleration data, even if it doesn't include intake and coolant temperatures. Something to start recording from OBDII if available!

Runs #1 & #3 from Saturday morning at Packwood, 26 June 2021, were at 82F & 84F, about every 10 minutes, spraying ice water on the intercooler & radiator & intake tubing between every run, hood open, engine turned off. Afternoon runs were in 102F, about every 4 minutes, spraying cold water (the ice was long since melted) on the intercooler & radiator & intake tubing between every run, hood open, engine left running with A/C on.

When things got hot, spraying kept the engine cool enough that there was minimal loss of acceleration during the first half of each run. It seems there's about a 5% range due to uncontrolled variables such as traction, line chosen, etc. Starting with the second half of the run, about 25 seconds in, the acceleration loss was noticeable. The data is from accelerating full throttle to the finish line, where the greatest acceleration difference was observed.

Conclusion: Over 100F ambient temperature translates to around a 10% loss in acceleration and it gets worse as more runs are taken. If the coolant temperature needle rises above that rock-steady middle line like it did for runs #6 & #7, you need to really cool things down again before taking a run. After run #7, the needle was at the 2/3rd mark. It seems about 6 runs every 5 minutes with careful cooling between runs is about the limit in extreme heat.


393307
 

·
Registered
Joined
·
1,386 Posts
Discussion Starter · #148 ·
Here's a glimpse of Pepper's current handling. My codriver and I are finding it very predictable, trustworthy, and easy to recover from mistakes. Solostorm data from our runs shows all we need to do is drive closer to the edge without going over it.

 

·
Registered
Joined
·
1,386 Posts
Discussion Starter · #149 ·
Packwood Tour Debriefing

  1. Saturday went better than Sunday for myself primarily because I didn't push hard enough in the toughest sections. I was off the desired pace by 0.7 sec on Saturday and 1.1 sec off the pace on Sunday per the SoloStorm data.
  2. Codriver was better at tossing the car into turns than I was, but I made up for it by having tighter lines and generally being on the throttle earlier (except for the finish on Sunday). His pulling more Gs gives him something like a 1-3 mph higher average speed in sectors, but my shorter distances most always wins. Pepper is obviously capable of making the Gs, so the trick for me is to get them without getting behind in the steering, which is how I believe he is traveling extra distance.
  3. When Pepper oversteers and you correct, she almost instantly snaps into understeer (unpublished video of codriver's day 2 third run). Believe this is due to the inside rear wheel lifting and then dropping back down, thus the proper driver reaction is to just do a slight countersteer and not lift throttle, as seen midway through codriver's day 2 video.
  4. Referencing other classes (STS, STX), the SoloStorm data suggests there is no reason to use different tires. However, I've ordered a set of Yokohamas to test before Nationals especially since the parts to try another suspension config will not be here in time, so I am concentrating on "do what you can". I know the Yokohamas will pull more Gs than the Bridgestones, but during my last trial with the Yoks, I only got massive understeer throttling out of corners.
  5. If Nationals were held tomorrow, I'd probably come in 14th of 18 (ugh). Pretty certain it's the driver and not the car at this point.
 

·
Registered
Joined
·
938 Posts
Lots of really good insight! I'm looking into a local event, finally... My setup is just not meant to do rallycrosses (well, I don't have time for all the extra wrenching anyways, lol), but it's pretty much gtg for at least getting into my first autocross. I'll just keep renting prep'd cars for the occasional rallyX, hehe.

I'm going to keep rummaging through your thread for some of these excellent tips and experiences. Great work keeping this so detailed and constantly updated!
 
  • Like
Reactions: gemery

·
Registered
Joined
·
1,386 Posts
Discussion Starter · #151 ·
Got a number of comments on how well Pepper is handling. My codriver is in tune with her and I'm in tune with her, so we're not changing the basic setup before Naitonals. We know where we're making our driving mistakes. At this point, if we can't fix our driving, finding & adapting to the best tires are our hope to improve beyond fixing the mistakes.

The Yokohamas are on backorder and the 2-yr old 255 Bridgestones on 17x8" rims left over from G Street config are shot, so another set of 255 tires for the 17x8" rims is required to tide me over until Nationals. Was going to try stretching another 20 runs out of them, but I need competitive tires for Aug 7-8 events and these old tires are not them!

I'm saving the 100-run 265 Bridgestones on my 18x9" rims for Nationals in case the Yokohamas don't work out... crossing my fingers that I'll have the Yokohamas before Aug 7-8, but who knows if/when they'll be here?

So which tires to try this time, Falken or Kumho? I picked the Kumhos on the strength of their performance amongst G Street drivers, reports of being fast on first runs, and doing well in colder weather. Not Yokohama fast, but more so than the Falkens. Just have to remember, like the BF Goodrich tires, they're no good in the wet.
 

·
Registered
Joined
·
1,386 Posts
Discussion Starter · #152 ·
Very interesting discovery... Kumho Ecsta V730 tires do not talk to you until you've exceeded optimum grip. The grip loss is rather sharp, too, subtly losing time whenever you hear any squeal. Probably not a tire for the beginner as they won't have the experience to find the edge of traction except by continually going beyond it.

Grip loss showed up in Solostorm as I'm feeding throttle, on both the speed & lateral force traces. Peak G-force occurs just as the tire regains grip. What surprised me about this result is that my peak lateral grip is NOT occurring during turn-in. In truth, the later peak G-force has been evident before with other tires, but I haven't recognized the need for a subtle change in my driving style: turn-in more forcibly, particularly as I've got the rear under control these days, and maybe be slower to return to the throttle.
 

·
Registered
Joined
·
1,386 Posts
Discussion Starter · #153 ·
0.9-1.0G with the pinched 255 Kumhos right before throttle application and inside wheel remains touching the ground as I intended.

395031
 

·
Premium Member
Joined
·
888 Posts
Those wheels look great on that car!! :love:
 
  • Like
Reactions: gemery

·
Registered
Joined
·
1,386 Posts
Discussion Starter · #155 ·
Tire Testing Wrap-up

Trying to decide between 3 sets of tires for Nationals: the 265/35-18 Yokohama A052 tires, the 265/35-18 Bridgestone RE-71R tires which have over 100 runs on them, and the skinnier 255/40-17 Kumho V730 tires on 8" rims. If they made them, I have no doubt I'd be on 265/35-18 Kumhos, however...

Since I only have a single set of 18x9 race-duty rims, the Yoks could not be tested back-to-back against the RE-71s, so I'm glad I have Solostorm for data collection. The last time I tried the Yoks, they did not work for me while under throttle and attempting to turn. It turns out they're more load sensitive than the other brands, so a fwd car needs a little extra rotation to make them work. Not necessarily oversteer, just some way to complete the rotation before adding throttle. I'm managing that rotation by adding rear tire pressure, setting the tire pressure higher in the rear than the front. The Yoks mainly need a greater difference between the front & rear pressures to get the desired effect; I've changed nothing else in my setup.

A-B-A testing pattern. I took 8 runs in the Yoks to get used to them and find the right pressures. Swapped to the Kumhos, took 8 more runs, and matched the Yoks time. Swapped yet again (rotated tires front-to-back because Yoks wear fast), 3 more runs, and beat the Kumhos by only 0.2 seconds on a 64 second course. Since I like the feel of the Kumhos more and they wear better, normally that wouldn't be enough to convince me to choose the Yoks, so I had to look at the data.

As expected, the data shows the Yoks pull a little more G-force in transitions without getting squirrelly, provided you're not trying to overdrive them. That difference may be due to the extra width of 265s over 255s, but it's enough to be worthwhile. In sweepers, a little tire talk, a little singing is the indicator that you're on the edge of traction. So I feel the Yoks have an edge over the Kumhos, but I need to not ask too much of them on corner exit, make sure the car is pointing in the correct direction before pinning the throttle to the floor.

Note that I'm bleeding front tire pressure after each run, but letting rear tire pressure rise naturally. Yes, that means the rear gets looser, but it is offset by heat making the tire stickier. The cooler the weather the lower the tire starting pressure should be for all these tires. A drop in the 0.5-1.0 psi range seems adequate. I've tried pushing run 1 rear tire pressures upward slightly and smokey 1st turn spins have been the result.

Summary

A052 -- 37F/39R starting pressures for second run, bleed fronts back to 37 psi each run. I think 36.5F/38.5R for first run is appropriate, but haven't thoroughly tested. 36F/39R was definitely wrong on a cool day and 37F/38R is safe. A little singing lets you safely find the edge of traction. High load sensitivity means braking and acceleration weight transfer can produce undesireable results. Wear rate is high and the tires are costly. The rubber turns to dust rather going gooey & peeling.

V730 -- 34F/35R, bleed fronts back to 34 psi each run. They respond crisply to weight transfer, best feeling tire I've experienced on Pepper. If they're talking, particularly under throttle, you've exceeded optimum traction. Appear to wear extremely well, though I've only put 24 runs on them so far. The 255 width matches the 265 width Bridgestones for grip. With a lack of tread blocks, this is not a tire for the rain!

RE-71R -- 34F/35R, bleed fronts back to 34 psi each run. The tires talk, but the sounds aren't consistent enough to use as a guide. Tread pattern hums if used on the street. Wears well, easy for me to get 140+ runs out of a set. Good rain performance. Out of production since fall of 2019, so probably not competitive after this year.

RT660 -- haven't tried them yet as the section width of 265s will likely rub badly with my current suspension.

Pilot Sport 4S -- 35F/36R or maybe 35R. These are rain and cool/cold weather autox tires as they overheat too easily above 65F ambient unless its raining. I've been using 245s, but am now considering how to move to 265s for better grip in damp-but-drying conditions.
 

·
Registered
Joined
·
1,354 Posts
Sounds like the Kumhos behave similar to the BFGs, except better in cooler weather, where the BFGs try to kill you if the temps aren't above 70 degrees.
 

·
Registered
Joined
·
1,386 Posts
Discussion Starter · #157 ·
Sounds like the Kumhos behave similar to the BFGs, except better in cooler weather, where the BFGs try to kill you if the temps aren't above 70 degrees.
I'm wondering if the 255 Kumhos would match the 265 Yoks once they're put on 17x9 rims instead of being pinched on 17x8... longer ARP wheel studs arrived Friday and I'll be cutting them down to my desired length soon, but the install is still at least a month away.
 

·
Registered
Joined
·
1,386 Posts
Discussion Starter · #158 ·
Kumho wear after 24 runs: the outer block holographic tread is still visible.
395316
 

·
Registered
Joined
·
1,386 Posts
Discussion Starter · #160 ·
Aftermath of Nationals

Right outer CV boot has definitely leaked grease, but I couldn't find the tear. Shop will have a look on Wednesday and I've already booked Sep 29 for repair, but it isn't as bad as the left outer CV boot was last year, so I may get away with a temporary repair (aka duct tape & saran wrap) until Sep 29 rather than parking Pepper for several weeks.

The feared left front wheel rim rub turned out to be melted pylon trapped under the car from a spin at Packwood 3 weeks ago. The color made me think it was Pepper's paint. Have a look!

Tire Wheel Vehicle Plant Car




There is a rub on the fender liner that doesn't concern me. Also spot the glob of melted pylon stuck on the brake line on right of pic. That's why I thought there might be a rub on the brake line.

Automotive tire Hood Motor vehicle Automotive design Automotive fuel system
 
141 - 160 of 168 Posts
Top