Rear wheel hopping? Please advise

[DL-NA1]

I was at a track event this weekend, on a slow tight turn (left or right) if I want to gas the car a little earlier before I came out of a turn, I can feel the rear wheels are hopping or at least that's how it feels like. Have any of you track guys experienced this, loosing tracking? Is it possible that is becasue I didn't turn off the traction control? Or there is something wrong with my car. Thanks in advance.

Jonathan

p.s. Very nice track car, no wonder is a NSX.

 

[Ponyboy]

Hmmm...try lowering the rear pressures a little and see if that helps. Could it have something to do with the pavement being bumpy or something? If you can soften your suspension, you may want to try that as well. But this will effect your other turns as well, meaning this action will affect your other turns causing your car to behave differently than before and *may* cause to lose more time than you've gained. If so, maybe feather the throttle a little more on corner exit.

 

[docjohn]

My 96 has never done that on track.was your tcs engaged?were you bouncing off the rev limmiter? these might help explain it.

 

[DL-NA1]

My 96 has never done that on track.was your tcs engaged?were you bouncing off the rev limmiter? these might help explain it.

The rev meter was at around 5-6k, not even close to 8k. I just got the NSX couple month ago, it's my first experiene with a NSX. After thinking more about it, it might be the tcs but then I did not see any tcs light flashing. Is there any warning light when the tcs is active? Thanks.

Jonathan

 

[Ojas]

I think Ponyboy and docjohn offer some good explainations.

I see you have a 1994. The only other thing I can think of is that your shocks may be worn (assuming they are the original OEM). How many miles are you car? Did you notice a lot of body roll?

The only reason I mention this is when I first autocrossed my last NSX, I experienced something similar. In my case it was due to worn shocks (car had ~150K miles on the odometer). Immediately after that event, I installed some Bilsteins and the problem went away.

BTW: Here's what an NSX should NOT look like going thru a turn:

 

[Ponyboy]

Yeah, I'm thinking it's a worn shock. In that case, good news, you'll be getting new shocks and springs. Cuz not a whole lot is going to help that.

Koni/Eibachs.

 

[NSXTC]

Ha! since we are all posting gratuitous track shots, I couldn’t resist. Here’s one that shows how much you can expect to lean with Dali Race Sways (21mm) and Zanardi Springs and Shocks. This is turn 5 at Willow Springs. Notice that we are actually burning a little rubber exiting out of that turn (high-boost BBSC) - that's not exhaust!

A little wheel spin, but no wheel hop here, baby!!

 

[Tom Larkins]

Have you also given a close examination to the pick-up points of your suspension and/or shock mounts in this area. Under loading you could be stressing a certain location that may only come to your attention at that time. The aforementioned opinion about the worn shocks would be a logical plan of attack first, but we don't know the history of the car.

 

[Hrant]

duplicate

 

[Hrant]

Take this one step at a time to simplify your diagnosis with the cheapest task done first. The recommendations thus far are on target but with different priorities ......

Here are some questions that helps diagnose the problem.

1. is this your first track event ever (not necessarily with an NSX). I ask this because it helps to put in perspective what your speeds could have been, your driving experience .... cost $0.00

2. what was the outside ambient temperature when this happened. cost $0.00

3. What type of tires did you run, both front and rear? And how much treadwear was there? ..... cost $0.00

4. what was the temperature in your tires before you got on the track (preferably measured cold in the morning). If you did not measure them, what was the temperature after you had the session. Tire pressures can go up as much as 8 psi in the rears and 6-7 psi in the front on aggressive driving in 80+ weather ...... by the way the NSX community is split on what is an appropriate track tire tempreture [lower is beeter .... <vbg>] . ..... cost $0.00

5. you probably were driving with the TCS on if you did not see the light on the center of the dash; yes it will come on when it engages. In simple terms (that's how I explain these to myself <g>), theTCS shuts off the gas when it senses one wheel spinning fatser than the other. You might think it was hopping but it would more likely be like bogging down ..... try turning the TCS switch on (turning the system off) next time you are at the same track and see what happens ... cost $0.00

6. Do you know if your alignment is within the recommended specs .... cost to check about $80.00 +/-

7. if all fails, start checking the suspenion components. Do you have any aftermarket parts? How many miles do you have on the car?

HTH

 

[DL-NA1]

First of all, thanks all you guys for the reply.

I have also thought about the shock could be worn out but I am just curious if anyone else have experienced this before.

Answer to Hrant's question,
1. I am a regular track junky for 4 years now, I usually drive my other cars, 95 Supra TT, 97 M3, and 97 Porsche C4S. I enjoy going to track event as often as I can, but the wify dont' like it as much.....

2. Outside temp was around 60 at the time, Seattle weather at this time of the year.

3. It came with the Dunlop SP Sport 9000 when I bought the car a few months, and the tread is about 90%. The tires would much better than I expected though.

4. Cold tire temp was at 33 all the way around, I don't know much about the NSX's behavior yet so just decide to start it there. Yes, the tire temp usually would get up to be about 7-8 psi higher.

5. TCS was on, I didn't turn it off.

6. I don't know the alignment spec, but I don't think that would cost the hop feel maybe the tread wear.

7. The car is completely stock, and it has 52k miles now.

Is there a easy way to tell if the shock is blown without taken it off the car?
Thanks again.

Jonathan

 

[Hrant]

Based on the tire pressures alone, as the ambient temp seems to be ideal, I am guessing that you most likely had a weird oversteer causing the back to retaliate for the grip on the front by hopping to catch up rather than to oversteer through the tire contact patch ..........? From others who have used SP9000, they say it is great in the rain but on the track it is not as communicative so perhaps the two issues may have resulted in what you experienced?

The NSX likes a differential in the tire presuures between the front and rear, at least 5 psi unless you have done major mods. I and others have found that when the tires are in the range of 28/33 psi cold front/rear we get the best grip. Others prefer the oem setting of 33/40.

Try it next time and see if reduces the hopping.