STF posts

[xnamerxx]

290p/260p
350/350

[NJ Drive]

Initially I was planning on staggering heavier in the front w/o a bar and give it a go. My wheelbase is a little longer than yours too so behavior under braking might not be as pronounced.

Your data acquisition is nice too.

[xnamerxx]

So the more I stagger rear roll stiffness the more liftoff/brake oversteer I get, there was a fine line from nice rotation to fwd drift car. Just having the rear spring stagger gave me enough front end accel traction that inside spin wasn't such a bad problem, I still complain about it but its mostly due to me getting back on it too soon when the front inside wheel has no load and is at a sharp angle.

Now I'm not positive this is true so take it as here-say but you can't transfer load dynamically from the left front to the right front by using stiffer springs can you can do so from the left front to the right rear and vice versa so taking load off the front by using stiffer rear springs seemed to be the way to go in getting some more front end bite. I still feel I need -4 camber to fix to get the Toyos happy but I haven't pursued that path yet.

[racerb]

Finally ran the Yaris in STF with the local SCCA group, was the only car in class but turned fairly respectable time. Only mods so far, 23mm UR rear bar, K&N drop-in filter, and some rock hard Goodyear Eagle GT tires.

http://www.ncrscca.com/sites/default...auto-x_fin.htm

racerb

[ilikerice]

good job racerb. imagine what it CAN do now.. lol.. was that just a "all my other cars are down right now, lets just run the yaris" event? or will we see more STF mods to the yaris and more/better results?

[racerb]

Planning on doing about everything possible to prep the Yaris to the maximum of STF rules. I have been also concidering a B-Spec Yaris, but with an earlier chassis, 2007-2008 model from one of the salvage car sites, really cheap that way. Here is one of the salvage sites I mentioned....
http://www.salvageworld.net/search.p...2009&x=52&y=11

racerb

[cali yaris]

the more liftoff/brake oversteer I get, there was a fine line from nice rotation to fwd drift car.

yep. That's really fun with 300+ to the wheels. I've done some power slides that made my passengers wonder what the heck was happening.

[xnamerxx]

Well just wanted to add my feedback for the z2's.
I ran first session on my R1R's and second session on my z2's and I was about a second faster with my larger diameter z2 vs the R1R's. Had to go into the data to figure out why, but the limit of the Toyo's and the dunlops appear to be about the same with the z2's having a slighly higher limit, what made the Dunlops so much faster was that I was able to keep the car on the limit from the entrance of the turn to the exit.

[racerb]

Thanks, good info as I'm still trying to decide on tires for this season!

racerb

[xnamerxx]

I wanted to do a back to back between my R1R's(195/50/15) with about 50 runs on them and my brand new z2's(225/45/16) to see how much of difference I would have between them.
The toyo R1R's have tons of grip but are a really really numb tire that doesn't have great turn in feel and requires lots of camber to work correctly. I was running at best 66.2 on my Toyos and the car was skiddish hard to control and very very loose. Tire pressure was set at 30 psi.
Switching to the z2s later in the day after I had finished my runs on the R1Rs, the z2s were sharper had more overall cornering grip, but they didn't let go quite as easily as the R1Rs so the car didn't want to rotate very well at low speed. The biggest thing I liked about these tires was that I could get the slip angles pretty bad and it would still hold on, and I mean wheel cranked really really far over, the tire would just scream and eventually pull over, these tires require a lot of work to get the most out of them, but seem to be a touch heat sensitive(at least on my car). above 130 degree's they give up slighly. No where near as bad as the Toyo's but I didn't quite have the same results at the STX BMWs.


Car setup
Front
Camber -3.5 degrees
Caster 5 degrees
Toe 0"
Rear
Toe .2" in
Camber didn't bother checking

Dunlops (42.5 psi) 16x7 OZ Chrono HT
Toyo's (30 psi) 15x7 Kosei K1R I think


Going over my data I was able to stay on the limit longer with the z2 than I was with the R1Rs. The r1rs seem to hold about 1.1gs according to the data and the z2 were holding 1.15 steady state but I did lose a bit of acceleration going to the taller tire.

These results are subjective as the course was very very dirty in the morning when I ran the toyos, I was picking up OPR and rocks like no ones business, but it felt quite a bit more clean in the afternoon. The surface was asphalt so I don't know if the results will carry over to concrete. On a side note this was the first time I didn't have horrible shoulder wear on a tire after an AutoX run so at least for camber limited cars I would say the z2 is a good pick. Overall I think the Z2 is going to be a tire to have in the future.


So I went further into my data and I was faster on the Toyos for the most part but I was having some pretty bad issues with the Toyos just letting go out of nowhere. Not sure if it was a course issue or not but it was something I was experiencing.

[justjesus]

hmmm. interesting info, Namer. Especially the last part about the toyos being a bit faster for the most part.

Damn. I really need to sell some wheels and do a little more prep work on the Yaris.

I just signed onto SD regions' site, so I'll be looking to run some events there. I'll be alternating between the cars. hehe... in pursuit of learning and developing as a driver.


Thanks for sharing your findings with the community.

[xnamerxx]

i think there was something wrong with the course when i ran with the toyos, the car was really loose on the edge, almost like driving on dirt or oil.

[NJ Drive]

Just wondering why you chose 42psi for the ZIIs? Seems very high for a light car like the Yaris. Dunlops also don't reach their prime until after a couple events or a couple weeks of street use.

[xnamerxx]

I varied the pressures from 38-45 and was fastest with 42. I treated them like the old Z1s for pressure and kept them on the high side.

At 42 I ran a 65.282
At 44 I ran a 65.537
At 38 I ran a 66.235
At 40 I ran a 65.713

Going with temps on the tires the center was still cold at 42 psi and even at 44 but the car felt quite a bit more stable transitionally at 42 than it did at 44 but at 44 it felt as if I could hold the corner better.

Here is a screenshot of my fastest runs with both the Toyo and the Dunlops. For whatever reason I had more confidence driving on the Dunlops vs the Toyos, I'm pretty sure it was due to something on the track but I'll have to test this again at another place to be sure.
Red is Toyo
Blue is Dunlop

[NJ Drive]

Interesting. They'll get better with use. Is your site asphalt or concrete? Air temps?

[justjesus]

Namer, we could always do testing at Adams! !
Tuesday nights (and some saturdays as well)

[xnamerxx]

I can do a sat, but the tues night ones are difficult for me since I get off work so late

Air temps were mid 70s for the toyos and 80 or so for the dunlops. This sight was asphalt with track temps in the 80s for the toyos ad 90s for the dunlops.

[NJ Drive]

Originally Posted by xnamerxx

I can do a sat, but the tues night ones are difficult for me since I get off work so late

Air temps were mid 70s for the toyos and 80 or so for the dunlops. This sight was asphalt with track temps in the 80s for the toyos ad 90s for the dunlops.

Thanks Namer, great info and data. Our first test 'n tune is March 10 on a runway site but the rest are at the Meadowlands, which is smooth, perfect asphalt.