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02-22-2009, 12:31 AM | #1 |
Parallel Parking Pro
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But similarly with tire pressures, generally softer yields better traction. Yet you could go too soft and cause tire contact deformity, or too hard, which causes lack of tread compliance. Hence optimizing is the key, what you have called compromises. But I respect your experience, which I do not have. If I manage to get my hands on this Cusco bar, I'll report back with what I found, at least it'll help others make a more informed decision.
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Leong's NCP91 Toyota Yaris E Hankook V12 Evo 195/55/15 on Buddy Club P1 replicas 15x7 ET +38 Stebel horns, Philips Silvervision turn indicator bulbs TTE Lowering Springs, Camber bolts TRD Blue brake pads Fujitsubo Super Wagolis axleback exhaust DC Sports header |
02-22-2009, 10:27 AM | #2 |
What?
Drives: 2007 Yaris LB Join Date: Nov 2008
Location: Safety Harbor, FL
Posts: 1,006
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Adjusting tire pressures does two things: adjusts the shape of the tire's contact patch, and adjusts the effective "spring rate" of the tire.
Today's high-end performance tires have SO much reinforcement of the tread area that tire pressure has little effect on the shape of the contact patch. It stays flat no matter what. If you're on craptastic all-season tires, you might see some change in the contact patch with pressure. (but this thread isn't for those people!) The change in effective spring rate of the tire, as long as you don't distort the contact patch too much, is primarily what we feel with our tire pressure changes when we're tuning a car. We work within the "window" of pressures that the contact patch stays flat in. (with a good performance tire, that can be a big window... like the Azenis... easily 30-50 psi!) Within that window, you're simply fine-tuning a spring rate that has the same effects as changing any other "spring rate" in the suspension. So, whether you're adjusting tire pressure, spring rate, sway bar rate or shock damping, the general effects are the same: Stiffen the front = create more understeer or less oversteer Soften the front = create less understeer or more oversteer Stiffen the rear = create more oversteer or less understeer Soften the rear = create less oversteer or more understeer Those are the facts. You can look them up in any suspension tuning book or even on one of a thousand different suspension tuning guides that you might find on the internet. Knowing that, if you NEED to fit that larger front swaybar to prove it to yourself, go for it. There really is no substitute for experience. I'm all for experimentation that will help people learn and quantify what suspension changes really do. I just hate to see people waste money on parts that aren't going to help them. Do the cheap or free experiments first... like playing with tire pressures... disconnecting the front swaybar... stuff like that. Those cheap rubber donut spring spacers that you can get from JC Whitney for like $20 a set are a GREAT experimentation tool. Toss a set of those on your springs... take some measurements and figure out what you've changed the spring rate to, and document the results. (I tried a pair on the rear of my Yaris, my calcs said it raised the spring rate from about 2.0 kg to 2.5 kg... it was a happy understeer-reducing change, just like it was supposed to be, and it's why I never wanted to fit the 2.2 kg rear springs that came with my K-Sport kit) |
02-23-2009, 02:33 PM | #3 |
What?
Drives: 2007 Yaris LB Join Date: Nov 2008
Location: Safety Harbor, FL
Posts: 1,006
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Hmmm... in SCCA stock class, you can't change the springs or alter the ride height. Dampers are otherwise unlimited... Hmmm...
Seems to me that you could get a generic race shock to replace the rear shocks on the Yaris pretty easily. It's just an eye at the bottom and pin at the top, very common configuration. Get something that you can dial in really some really stiff compression damping for autocrossing and it should do a world of good for reducing understeer. That, plus maxing out the front camber, and the tires mentioned above... that should do a pretty good job of challenging the competition. footnote: One of the caveats of the "shocks are free" rule is that you can't alter the spring perch height. Since the spring perches aren't part of the Yaris rear shocks... you should be free to replace those rear shocks with ANYTHING. |
02-24-2009, 09:27 AM | #4 |
Drives: Yaris Join Date: Oct 2008
Location: Michigan
Posts: 199
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02-25-2009, 03:42 PM | #5 | |
Drives: 2010 Mazda3 iTouring Join Date: Jun 2007
Location: San Bernardino
Posts: 234
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Quote:
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03-03-2009, 12:17 AM | #6 |
Don't drive it, RALLY it!
Drives: 1999 echo PRC rally car Join Date: Oct 2008
Location: Joyner, Brisbane
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03-03-2009, 02:53 AM | #7 |
Drives: 2010 Mazda3 iTouring Join Date: Jun 2007
Location: San Bernardino
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Ohlins right^^^^^^^??? I'm pretty sure that's how they set up their external reservoirs.
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03-22-2009, 02:27 AM | #8 |
Drives: 1NZ-FE Join Date: Oct 2008
Location: asia
Posts: 55
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02-23-2009, 02:56 PM | #9 | |
Start another Oil Thread!
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..... and getting the yaris to rotate is by far the most important thing in stock class :D
it's a shame you won't get any real camber out of the front though :(
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03-03-2009, 04:00 PM | #10 |
Super Moderator
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Question: How would 10mm rear hub spacers affect handling?
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03-03-2009, 04:39 PM | #11 |
Apexing Egg!!
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i have been meaning to look this up as well.
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HighTach Motorsports 2007 Toyota Yaris-ARGH!! Mods: Tokico HTS, 6.6 kg F, 6.1 kg R custom springs, 23 mm RSB, 2-way TRD LSD, 15x7 +25 Team Dynamic wheels, 195/55/15 Dunlop Star Specs, Cobra Suzuka S |
03-03-2009, 05:01 PM | #12 |
What?
Drives: 2007 Yaris LB Join Date: Nov 2008
Location: Safety Harbor, FL
Posts: 1,006
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Wider track usually means more grip (for various reasons). So, widening the track in the rear would make the rear stick better. Not really what most of us are fighting for, with a FWD car, you want more grip in the front.
The rear hub spacers are purely a cosmetic mod. (not to be confused with alignment shims) |
03-03-2009, 05:21 PM | #13 | |
Apexing Egg!!
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im still working on this shocks thing, i have to turn in a research proposal this week and its consuming all my time! :(
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HighTach Motorsports 2007 Toyota Yaris-ARGH!! Mods: Tokico HTS, 6.6 kg F, 6.1 kg R custom springs, 23 mm RSB, 2-way TRD LSD, 15x7 +25 Team Dynamic wheels, 195/55/15 Dunlop Star Specs, Cobra Suzuka S |
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09-02-2009, 08:54 AM | #14 | |||
Start another Oil Thread!
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03-22-2009, 02:28 AM | #15 |
Drives: yaris Join Date: Mar 2009
Location: under there
Posts: 8
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Post #1 of this thread doesn't show me yaris handling information?
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07-24-2009, 06:53 AM | #16 | |
I ♥ Yaris
Drives: Black 08 LB MT & red 97 Miata Join Date: Oct 2008
Location: Indianapolis IN
Posts: 1,313
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Quote:
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The trouble with the world is that the stupid are cocksure and the intelligent are full of doubt. - Bertrand Russell |
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07-24-2009, 08:34 AM | #17 | |
Start another Oil Thread!
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fortunately i kept a backup. PM me and i'll email it to you. until i know it won't get deleted again without explanation i'm not going to post it in the original post.
edit: lol look! it magically re-appeared.
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11-02-2009, 06:45 PM | #18 |
Drives: 2007 Yaris LB Join Date: Mar 2007
Location: San Jose, CA, USA
Posts: 685
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I am looking for a little advice. So the wheels I have now on the Yaris were the very first mod I did and I must say, I didn't do my homework before buying. So I ended up getting 16x7" with 195/50-16 tires. After finding this kick-ass thread and doing more reading on the subject, I'm thinking about going back to 15x6.5" with 195/55-15, as recommended here
Now, I also have lowering springs (NF210) and shocks on my list, which is the next thing I had in mind, but I was wondering, would it make more sense to replace the wheels first and then get the springs and shocks or get the springs/shocks first? |
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