rrthorne8

dont you race a nissan?

rrthorne8

50 pounds isnt much in my opinion. however if i was to make the change, go to 550ish rear. But try what you have first right?
staying with 315 rear, probably 315 front toward end of season, just depends on how busy i get with other endeavors.
Car likes a little tire contact patch split front to rear, however the one inch difference is a little much with low power output (front heats up quicker then rear)
car doesnt balance out till 2nd run after fronts get sprayed

03threefiftyz

Yeah...and not well either .

ebdavis

Anyone know what width Ankeny was running on his? I think it was significantly narrower but I'm pretty much talking out of my ass.

sproutxj

I will just pickup 550s when I get the 750s for the front.


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sirbunz

Yeah...and not well either .
[/quote]

Only so many places to talk about BSP and help recruit newcomers? I applaud your efforts! My black car may be a BSP car once again!

-Marc

sproutxj

^ I do appreciate the sharing of knowledge for sure.

Do you think I will need to be concerned about bumpsteer in the rear going as low as suggested? Our big course venue doesn't have the smoothest tarmac.

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sirbunz

Here is my best attempt at this question ... From this point moving forward, I will stick with OEM ride heights (or close after corner balancing) for better clearance of the big wheels/tires and for handling/suspension geometry/etc issues. There is no doubt Robert's car is the proven setup to date and my attempt at a BSP car was plagued with electrical issues. Still, my opinions come from the R&D when we all ran in STR, comparing what worked with what didn't. Given the limited grip the 255 width street tires, handling got progressively worse as the car was lowered. When we set ride height back to stock, the desired rear stability and overall handling came back. Hoosiers tend to mask these characteristics with lots of available grip compared to the street tires. There is some balance in the suspension that likes stock height on the lower speed/fast transition type courses you get from auto-x. On paper, lower should be better. We took off the springs/shocks and measured the angels and change in alignment as the control arms moved. The bump steer/toe changed less when lowered, but on course the rear doesn't "dig in" or hold grip when tossing the car around like it does at stock heights. We went through countless ride height, alignment, and corner balance changes over the course of 2 full seasons trying to find that "magic setup" for this car like we did in the stock class.

For shocks, I like using more rebound vs compression for adjusting the rate of movement of the car, but that's only relevant if you have a basis to compare shock valving from me, Robert, or whoever else your comparing notes. Each driver will have different preferences here.

For swaybars, I like stock. The adjustability is nice and may be useful to someone who likes to have that option, but the springs take most of the sway out. I think 800-1000lb springs up front and 600-800 rear will be what most settle with "if" they use softer/OEM bars.

I did not like KWs, so I have no input for you there. The set I have most my experience with were similar to the Koni 8242s (probably why I like adjusting with rebound). The high speed became a factor on the typical bumpy surfaces we run on. This didn't make much sense until I started running on the high dollar monotubes. I would advise to stick with what you have and save for these in the future when you change springs.

Im only average when it comes to advise on this stuff, so take that into consideration. On the flip side, I do have a ton of seat time with these cars in many different levels of prep. I drive these cars on the absolute edge of the limit "high risk" so ignore me if you are a conservative driver.

Best of luck with the build!

-Marc

mLeach

here's the good news about bump steer - its linear. it doesn't change much on the AP2 rear, so you're good there. On the AP1, as long as you maintain grip, the car tightens up as you increase the lateral load (entry, in most cases) and loosens up as the friction circle takes a more longitudinal load (corner exit). If you can slow down the rate of change in geometry, the car is more predictable. On the AP2, it's neglible. You probably get as much change in geometry from bushing deflection.

re: ride heights. The higher the car, the lower the spring rate has to be because the high roll center transfer's rate faster The roll center and CG are closer together. When you lower the car, you also lower the roll center, and more weight is transferred, but it takes longer to happen, so you have to use shocks/springs/bars to get the responsiveness back.

I think I will be raising my car slightly and running a slightly softer setup this season with all of this in mind.

IntegraR0064

Understatement of the year