kekek

iTrader: (22)

The hollow bars work just as well as solid since the majority of the twisting force (torsion) is absorbed by the outer diameter/portion of the material.

As for tires, I would be real weary of going too wide. With the fresh asphalt in Topeka they'll never warm up, especially if its cold. The other problem is the 315's are probably tall, and that extra height (and weight) is going to sap HP and TQ. We did a little experiment at a dyno day a few weeks ago. Car was an Evo9, went in for a tune on his stock size snow tires. Results were 307HP and 330TQ. Went a couple days later with 255/40 RA-1's and he lost around 20HP and 10-15TQ, temperature variation wasn't huge either. So the 285/30/18 is 24.6" Dia, 315/35/18 is 26.4" Dia and 315/35/17 is 25.4" Dia, these apecs are off the TR website and are for the V710. Hoosier's sizing seems to be better and their 295 is quite appealing. Personally I can only budget one set per year so it's V710 for me.

madmax199

iTrader: (20)

What's up Kevin!!! do you know if Jan (I beleive was running wider than 285 at topeka) was in heat range in his front as opposed to the rear? I'm the market for a set of autocross rims and I was contemplating running 285 in the rear and slightly wider in the front, providing that I can get them up to temperature.

SS RX7 r2

iTrader: (1)

Hi Kekek,

When I ran 255/40-17s I thought they were slightly shorter than the stock tire- I guess I should check TR. Were the tires 18?

I wonder if a dyno would show the increased friction effect of wide sticky tires and agressive toe settings?

Rick

kekek

iTrader: (22)

Jan was running 295 Hoosier A6's on 18x10.5 frt and 18x9.5 rr. We did some pyro measurements during the summer but I don't recall what they were. He was a single driver at Topeka, but I didn't speak with him too much about the tire/heat situation there. BTW, this is John, Kevin's SN is kevo.

Rick,
I guess my statement above has to do with something else....since I just took a peak. The Advan A046 is 25.3" OD and the 255/40-17 RA-1 is 25" OD. I was just always under the assumption they would be taller (and I have a set of each tire at the house, go figure). Now the bigger variables are weather, tire compound and width, I don't know Henry's alignment settings either. The RA-1's were mounted on TE-37's, so I don't think there was a large weight variance. Perhaps a more scientific test is in order, personally I was gonna hop on with my 285's but it was a little too rainy and cold. We just thought it was very interesting that he lost so much power, the curve's were identical, just a shift down on the Y-axis.

Matt2.8NJ

iTrader: (7)

John, I agree the dyno #'s sound like the variance might be some other factor than the wheel/tire pkg...as you know I've gone thru quite a few sets of 255's now, and they are definitely shorter in overall diameter to a degree enough that the redline in 2nd feels like it shows up quite a bit sooner -as well as the car feels faster off the line. I've also noticed from a couple of dyno days I've been to that some Evo's (perhaps your friend's) vary wildly from dyno to dyno. I wonder if this phenomenon is especially pertinent to turbocharged/FI cars.


Has anyone tried the 315/35/17 V710? Looks like a ton of fun Only major drawback besides $Texas price is the diameter is .4" larger than stock. Flip side to that is that your 2nd gear redline changes...perhaps for the better?

http://www.tirerack.com/tires/Sizes....del=ECSTA+V710

A 315/30/18 would be perfect as far as gearing goes.


For reference, I like this calculator for handy comparisons:

http://www.miata.net/garage/tirecalc.html

nick735

iTrader: (5)

John I think the horsepower difference was due to a boost leak w/ his stock injectors. I may be wrong though....

kekek

iTrader: (22)

Henry didn't change anything on his car between dyno runs. His car was at "the shop" getting some work done and he had the boost leak test and injector seals fixed prior to having the car tuned. He then went back to the same dyno with the RA-1's on the car and above was the result. They do ratchet down the cars pretty good on that dyno though, alot less than say a dynojet.

Matt,
Those 315's might work up front with an aftermarket fender and an 18x10 or 10.5, I highly doubt they would work with stock fenders (SP). As for gearing, even with the shorter 285/30/18 you still don't spend all that much time up at the end of 2nd, and when you do it is momentarily. At no point during the season was I "wanting" more speed out of 2nd.


Oh yeah, forgot to add this tidbit. Henry's Evo9 put down approx 250tq @ 3000rpm. He has dynoflash, MBC, intake filter, HFC and TBE. My Evo8, same mods w/test pipe, only had approx 150tq @ 3000rpm. WTF!!!! damn Mivec and turbo gets around 100ft-lbs tq EXTRA at 3000rpm, Son of a *****! Anyone looked at the logistics of an Evo9 Motor Update???

LanEvoNine

iTrader: (18)

Yeah... I thought they were taller too, but when I plugged them into a tire calculator it wasn't. Not sure for the decrease in hp/tq but the tire pressures were around 33 psi and a bit wet, pretty good tread had 3 autoxes and 1 track day on them. Stock suspension, camber maxed fronts -2.0, 0 toe, rears: -1.3, 1/16 toe-in... definately need some coilovers to be competetive in BSP, probably not till next mid/late season those vishnu spec ohlins are looking pretty good (did anyone say tax return )... probably will migrate to SM after a couple years

madmax199

iTrader: (20)

EVOlutionary in his original post brought up the aerodynamic factor as one of the tools to have a competitive car. I am curious to know the extent of the benefits guys with aero parts are seing in relatively low speed autocross courses. I do not doubt that at speed above 70 Mph aero parts are effective, but I was under the impression that Bsp/Sm evos(on top 2nd gear) are not reaching speed high enough to really need these expensive aero parts. Anyone with experience before and after please let us hear it.

kekek

iTrader: (22)

I think John Tak and Andy Lieber did some testing for us. At Nationals in colder temps and a rubber-less surface Tak almost matched Tunnell's later heat times. From the Nationals pics I see no aero enhancements to the Tak/Leiber Evo. Based on that and the fact that Daddio also does not have any I would begin to really doubt their effectiveness at lower speeds. I've also run wingless on my personal car and found no difference.

If anyone has any "real" data on the subject I could be swayed.

Warrtalon

iTrader: (6)

Mine are working very well so far. I have another SCCA-RM event in 10 days with the goal of taking 1000 points again, but it's still just the winter series, which doesn't count.

LanEvoNine

iTrader: (18)

jeez aren't you buried under 10 feet of snow in colorado?

Warrtalon

iTrader: (6)

Just about, but it melts quickly out here, luckily.

SS RX7 r2

iTrader: (1)

The rules are such that aero wouldn't help much in BSP. Wings other than stock are not allowed. You could run the popular 9" wickerbill Nascar- like spoiler on a RS trunk, but with the evo's tall roof profile, it prob wouldn't be too effective.

SM is fairly liberal in the rules, maybe 7-8sq ft? is allowed including wings and spliters - I believe.

STU is 5 sq ft.

Rick

Matt2.8NJ

iTrader: (7)

Aero parts for a blocky profile sedan at low speeds in a parking lot seem like a modification that would fall into the category of "diminishing returns". By this, IMHO, I mean there are signifigantly better ways to spend your $$$.

But what do I know compared to this guy??