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Discussion Starter #1 (Edited)
Rumble Strips Problem

I was at Road America last weekend and noticed something new when I clip the rumble strips at the apex or on exit. I'll be in 3rd gear for example (doing 70-90 mph) and the shifter will shake violently left and right all the way from the apex to the exit while the car is drifting. There is also a loud, deep chattering sound while this is happening. If I stay off the rumble stips then the shifter doesn't shake nor is there a sound. Any ideas?
 

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Discussion Starter #2 (Edited)
Rumble Srtips Problem

I was at Road America last weekend and noticed something new when I clip the rumble strips at the apex or on exit. I'll be in 3rd gear for example (doing 70-90 mph) and the shifter will shake violently left and right all the way from the apex to the exit while the car is drifting. There is also a loud, deep chattering sound while this is happening. If I stay off the rumble stips then the shifter doesn't shake nor is there a sound. Any ideas?
 

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That is probably a function of rear shock rebound. What kind of ,and if OEM, year of shocks do you have ??

Could also be:
- loose shifter
- loose tranny/diff mount
- loose engine mounts
- whip in power shaft
- failing power shaft coupler

Using the rumble strips reminds me of the old mediacl adage:

Patient: "Doc, it hurts when I do this....."
Doctor: "Don't do that!"
 

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Discussion Starter #4
I have the Sachs shocks that came with the T1 suspension package. Sounds like I should also tell you that I had a fire at the end of last season underneath almost the entire car, engine bay, and all 4 wheel wells. One of the dust boots melted off the right rear shock but I did notice the problem when my left wheels hit the rumbles on exit.
 

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Probably have a transmission mount that is weakened and hitting that rough pavement brings that out--just a guess.
 

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If you have ever seen that rumble strip/cubing at RA up close, you would not climb on it unless your repair budget is substantial. It's hard on tires and the shock to powertrain can't be good either.
 

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I tried it both ways and while unfortunately my laptimer quit on me, so I can't give you a definitive answer, my best guess at this point is to use rumble strip a litte at the apex and track out except for a couple of corners. I think you should use all the room after the bridge following Canada Corner, the rumble strips are pretty small so it's not hard on the car. Also it might be advantagious to use the rumble strip in the last corner. If you go beyond the first rumble strip, the concrete is actually not that bad. Again, I can't tell you for a fact that this is faster but it sure felt faster.

I tried using all the rumble strip and I think it's not getting you any advantage except for the two corners mentioned.

BTW, anyone knows what a good time at RA is for a stock Z06 on Toyo RA1's?
 

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Discussion Starter #9
Turn 1 has a bump at the apex that is unavoidable that also causes the violent shaking of my shifter and the noise when driving faster than about 60 mph. I do stay off the majority of the rumbles after noticing this problem and the car seems to drive fine, but that doesn't exactly solve the potential underlying problem with the car.
 

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yeah, my post was not meant to say your car doesn't have a problem, rather to address the stay off rumble strip comment above. my $0.02 would be the tranny/engine mounts as the starting point but it's really just a guess.
 

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Well, I use them in some of the corners-and I can tell you that when I rode with Lou G, he used all the track-especially turn one, and turned a 2:29 with me in it.
 

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bbunting said:
Well, I use them in some of the corners-and I can tell you that when I rode with Lou G, he used all the track-especially turn one, and turned a 2:29 with me in it.
He used more than all of the rumble strip. I noticed coming out of turn 5 and turn 14, he was on the pavement on the other side of the rumble strip. The surprising thing about Lou's car was that I hardly felt the rumble strips. He had a great set up for the track, whatever it was.

Sal
 

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bufman23 said:
I was at Road America last weekend...
You guys, what are your lap-times (..with mods) at RA?

This past weekend is my second weekend at a track, and during the last session on Sunday I did a 2:45 in Group C, which is an improvement over last October's 2:52; stock '02 with '04 shocks and CarboTech pads.

JDBgn said:
Stay off the rumble strips.
Poor driving technic if you ask me.
MHO
Mafia said:
I tried using all the rumble strip and I think it's not getting you any advantage except for the two corners mentioned.
If you watch the fast guys at any event at RA, they are all over the rumble strips. Also, if you watch any F1, those guys are all over the rumble strips too. It seems they view them as that much more track to use.

BTW, anyone knows what a good time at RA is for a stock Z06 on Toyo RA1's?
I was talking to a guy last night with a stock CE (..including brake pads) who is an instructor, and he said he did a 2:32 with that setup; WOW! A very nice guy, too, who freely shared his brake-points and turn-ins, as well as entry and exit speeds. I learned a lot and have plenty to think about for next time (..May 28/29 with Chicago PCA).
 

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2:32 is very fast... what tire was he running? my best timed lap was 2:35 on RA-1's. I do have aftermarket brake pads. Interesting about rumble strips. Like I said I tried it both ways - once using every bit of track there was and once using just a little curb. Unfortunately, my laptimer didn't work for the second part so I can't tell for sure what's better.

Turns 5 & 14 do make sense to use the rumble strip. It has a concrete rumble strip beyond regular rumble strip that's actually relatively smooth. Next time at ALMS I'll be sure to watch the lines GT3 guys are taking;).
 

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Discussion Starter #15
Back to my original problem, the more I think about it, I am guessing it is drive line or transmission related. The shaking continues long after I'm off the rumbles and only goes away when the car stops drifting and straightens out. I am not changing gears at the apex so perhaps it is not the shifter or even transmission related. How should I begin to problem solve this?
 

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Had something similar in the Pocono Long course, when I got home and checked I had cracked rear uper forward control arm piont where the factory weld failed, but what was making the noise was that I only had one of the Trans/Diff mount left an it was also lose. Installed the missing bolt and torqued the both bolts down the problem never cam back. hope this helps.
 

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Discussion Starter #17
I found the culprit! A nut had worked it's way off one of the shock pistons. I put on some heavy duty lock-tight to prevent that from happening again!
 
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