ron_v

Thanks for all the helpful posts folks. These are a lot of datapoints for an aged newb... but sorting it all out. I'll post what I end up doing... and how it works out.

Norm Peterson

I did, but it's been a while. I had some initial thoughts, just never got around to mentioning them. I'm staying out of any sub-topics that might exist.


That make sense, given that bumps and roughness can cause the bushings to alternately load (compress) something like double what the acceleration loading alone would do - and then let the compression rapidly unload and release the stored energy without there being a thing the driver can do about it except ease into the throttle slower. If this sounds like wheel hop, it probably is just like a very mild case of that, and ought to respond to the same fix. There's an Interstate exit ramp near where I live that has a badly deteriorating seam that I simply drive a different line through rather than put up with, which I may be trying to describe as making for similar behavior as that Sebring turn (for the record, I still have the OE PHB as well).

The difference wouldn't be as great on a smoother track. NJMP's Lightning is smooth enough that you can squeeze all the way down to WOT pretty rapidly in all but a couple of places without anything unpleasant threatening to happen. Going through and exiting 1 crests a hill and gives a little twitch that I also think shows up the disadvantage of the OE PHB in really hard driving, and you can run out of pavement if you're too fast into, run wide of the apex in, or are too hasty for available grip coming out of 5 (which apexes right at the crest of another little hill and keeps on turning into what is defined as 6 without there really being a straight in between).


Once off the bumpy stuff, a lot of this probably has to do with the driver - his confidence in the car, the degree to which he gets unnerved by the car's inertial motions, and how smooth he is with the controls. The more confident you are - more linear car behavior being a factor here - the faster you'll be simply because you're more comfortable operating 'up there'. Even if there's little or no difference in the ultimate or peak measured performance numbers.


I'll have to wait until I get home to see the track map (corporate internet filtering at work). But you're definitely playing at higher speeds.


BTW, your article may eventually cause one more set of NT-05's in 275/40-18 to be sold. My 3-season GY Asymmetrics (also on 18 x 9.5 GT500 wheels) are pretty linear most of the time but can get a little 'slide-y' after being beat on for a couple of sessions. This tends to force a slightly later and more gradual throttle application that might mask any control arm bushing differences. I'll bet they aren't the only street tire to behave this way.


Norm

SteedaBrandon

Feel free to shoot me a PM and we can discuss some recommendations for you and your particular setup.

UPRSharad

I definitely think the advantage of the upgraded LCAs is relative to the roughness of the track surface. And I understand what you mean about how the driver responds to the roughness. I can say this, I'd say I was driving around 9/10ths. In other words, they say you should drive 7/10ths at an HPDE, but I'm like "yeah right. Me, on a racetrack? Forget that!" However, I wasn't as aggressive as I might have been in an actual race. I never spun the car, never did any agricultural racing, and my biggest misshaps were blowing the apex on one corner (might have been 10) which only caused me to run a wider line, and boiling the brakes going into 17a which also only caused me to run a wider line.

IOW, I probably could've been a little more aggressive on the throttle during the axle hop on the rough stuff, but it seemed better to let the chassis settle. I bet the tires were actually bouncing off the surface in those places. I certainly didn't have that problem on the upgraded LCAs. As far as lap times go, it was faster on the upgraded LCAs, but we also changed the pads & rotors, so I can't claim that the lap time improvement (around 2 seconds per lap) was solely from the LCAs.

Regarding the NT05s, I liked them. I got about 15k miles out of them, they were decent in the rain, and their dry performance was good. Definitely better than the F1Supercars I'm on now. I'd like to try 295/40s all the way around, but that's another discussion entirely.