TCS light at 175+mph?

Joined
22 November 2001
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The last two times I have exceeded ~175mph the TCS light has come on and only gone off after I have turned off the ignition. Any ideas?. Could this be the rear tires expanding and tripping the light?. BTW, this is a CTSC'd '92 with 215/40/17 & 265/35/18 S02's.

Thanks
S.M.
 
And just exactly where were you going at 175mph?
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Where I live (Great White North) you can do that kind of speed any night of the week just a few miles out of town.
Any ideas on the TCS light issue?

Thanks
 
Yes nsxman, thanks for the tip but I am not asking for safety advice.

Back to the question: Does anyone know why the TCS light might come on over ~175mph?.

Thanks
 
I grant you that I was expressing an aggravation.

As to your question, is your observation merely a problem with the light coming on or are you experiencing a drop in engine power?
 
I'm guessing it's tire growth. Your sizes are already very marginal in terms of TCS, and tire growth is probably significant at those speeds even for low profile tires.

I wish I had a stretch like that on to exercise, I'd sure use it when I was sure I'd risk no one's like but my own. I've got places where I can do short top end bursts, but only during very odd hours and always with some risk of arrest.
 
Your sizes are already very marginal in terms of TCS

Actually, no they're not. The front tire is 3.0 percent larger than stock, and the rear tire is 1.8 percent larger than stock. That's pretty close, with the difference between front and rear only 1.2 percent. (Supposedly 5 percent is the threshold to avoid.) But if the rear set is worn much more than the front, that could add another 2 percent. That, and other slight differences (such as the dimensions for that specific model - see that other topic on the forums), can all start adding up.

and tire growth is probably significant at those speeds even for low profile tires.

Wouldn't the front tires and rear tires grow at the same rate?
 
nsxman, there is no loss in power, from what I can tell the light just comes on.

Both front and rear tires have almost even tread wear.

Yes I run out of headlights, but since there are no other humans around I don't mind driving on faith for a bit :
 
You just have to watch out for those Critters crossing the roads just one of them and your gone.


Steven 91 Blk/Ivory
 
I don't know the answer to your TCS question but maybe it's a compute error - 175mph and I need to execute TCS - compute WTF - tilt!

On a side note I'd love to see a video running that fast and hear the exhaust.
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I figure since you're up north it's either Alaska or ND as that's the only place I ever been up to those speeds. Fortunately not a lot of wild critters running around ND but Alaska is another story. If if Dakota I hope no milk factories are standing in the road.
 
Originally posted by nsxtasy:
Actually, no they're not. The front tire is 3.0 percent larger than stock, and the rear tire is 1.8 percent larger than stock…

Well, yes, actually I think they are. I try to use the manufacturers specs for the exact tire because the variance that are meaningless for most applications become significant with the NSX. In this case I was no longer able to get S02 specs so I used S03. The OEM tires in particular don't quite match the calculations, but that's typically ignored which can be a problem when you start cutting it close.

OEM Fronts: 896 rpm (revolutions per mile)
OEM Rears: 807 rpm
Rear to front ratio : 1.11
Note: specs are based on stock rim widths.

S03 215/40/17: 875 rpm
S03 265/35/18: 820 rpm
Rear to front ratio : 1.067
Note: specs are quoted at rim widths of 7.5 and 9.5.

The difference between 1.11 and 1.067 is already significant. If his front rims are narrower and/or his rears are wider, it moves him further from spec. As you say, if the rears wear faster then that too adds to the difference. (Apparently his are not. Since I run OEM tires I always think of the rears being more worn than the fronts.
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)

As for tire growth, I guess as a percent the front and rears might grow at similar rates, but there may be additional factors. The rears probably run higher temps which could make a minor difference, and I would think that a wider tire would grow more than a narrow one. (I don't have facts to support that, but it seems logical.)

No doubt each of these factors alone are minute, but the acceptable variance is quite small. Add them all together along with manufacturing tolerances for the tires and the TCS system and you might well find his particular combination to be marginal.
 
i use 285-30-r18 and run them at very high speeds also, i usually go across the bridges here in Tampa and have absoultly no problem with tcs or beating an R1.
 
I try to use the manufacturers specs for the exact tire because the variance that are meaningless for most applications become significant with the NSX.

Okay...

OEM Fronts: 896 rpm (revolutions per mile)
OEM Rears: 807 rpm


We (sjs and I) went through this discussion once before. At that time we concluded that these particular figures (which are from the Tire Rack website) are in error. This explains why they produce a rear-to-front ratio that is inconsistent with the standard mathematical formulas of tire size calculators.

To use another set of numbers, the Tire Rack website also provides specs here for the stock-sized Bridgestone RE010 (the other OEM tire) and their revolutions-per-mile stats for that tire in the stock sizes are 911 and 854, respectively. Thus the rear-to-front ratio for THAT stock tire is 1.067. Which means that the S03 stats posted for the sizes above have the exact same rear-to-front ratio as Bridgestone's stock-size OEM tires.

Granted, there can be errors introduced from other factors such as tire wear, but those factors can apply with the OEM tires as well. Based on the manufacturers' numbers, the use of these particular sizes should not have anything to do with TCS problems.

[This message has been edited by nsxtasy (edited 22 November 2001).]
 
Originally posted by nsxtasy:

We (sjs and I) went through this discussion once before.

Was that you? I'd forgotten who. However, I also don't recall ever concluding that the figures were in error. I'm more inclined to thing they are simply the variations between manufactures since I've seen many times that the calculators missed by similar amounts with other tires. I've also assumed (though could be completely wrong) that the A022H represented the majority of OEMs delivered (it certainly seems to be for replacements) so I use it as my baseline. Do you have specific evidence that the published values are incorrect?
 
I'm more inclined to thing they are simply the variations between manufactures

If that were true, then you would have to conclude that using tires from one tire manufacturer whose tires are being supplied on the NSX from the factory - and remember, this model tire was designed specifically for the NSX - permits enough of a difference to throw off the TCS. That's not very likely.

since I've seen many times that the calculators missed by similar amounts with other tires.

But that's the thing - usually, the calculations from the tire calculators are off by similar amounts within the same model tire. For example...

Bridgestone RE010 205/50ZR15
per tire calculator: 874 rpm
per Tire Rack specs: 911 rpm

Bridgestone RE010 225/50ZR16
per tire calculator: 811 rpm
per Tire Rack specs: 854 rpm

front difference: +4.2 percent
rear difference: +5.3 percent

Bridgestone S03 215/40/17
per tire calculator: 848 rpm
per Tire Rack specs: 875 rpm

Bridgestone S03 265/35/18
per tire calculator: 797 rpm
per Tire Rack specs: 820 rpm

front difference: +3.2 percent
rear difference: +2.9 percent

IOW, the manufacturers' specs as posted on the Tire Rack website are consistently showing roughly 3-5 percent more revolutions per mile than a straight mathematical calculation based on the tire size. Which makes sense to me. (There are various ways in which each of the dimensions in the calculation can be off. I would guess that the manufacturers might take into account the deflection of the tire at the contact patch, which could account for a slightly smaller outer diameter when mounted on the car and rolling with the car's weight on it. Smaller diameter means more revolutions per mile.)

Do you have specific evidence that the published values are incorrect?

Compare that with the figures posted for the Yokohama tire:

Yokohama A022H1 205/50ZR15
per tire calculator: 874 rpm
per Tire Rack specs: 896 rpm

Yokohama A022H1 225/50ZR16
per tire calculator: 811 rpm
per Tire Rack specs: 807 rpm

front difference: +2.5 percent
rear difference: -0.5 percent

So while all the other tire specs show significantly MORE revolutions per mile than a straight calculation, the Yokohama rear actually shows slightly LESS.

Basically, we're left with a choice between two conclusions:

1. All of the published figures are correct, including the one for the Yokohama rear specs which is totally inconsistent with all the other figures. If this is the case, then the dimensions of the Bridgestone OEM tire are so far off from the Yokohama OEM tire that using the Bridgestone tire risks making the TCS not function properly.

Or...

2. The Yokohama rear spec on the Tire Rack website is in error. If this is the case, then using the Bridgestone OEM tires or the Bridgestone S03 tires in the indicated sizes on larger wheels should not be a cause of the TCS malfunctioning.

I consider conclusion 2 far more likely than conclusion 1.
 
I sent them an email last night as well. It should be interesting to see if we get a response.

Actually, I'm hoping you are correct. If those dimensions the "right", it makes it simpler to match up other tire choices. I guess I'm guilty of exactly what I warn against, failing to double check important numbers. (Of course, I haven't yet bought non-OEM tires anyway.) I can't help feeling certain that I got similar numbers from a different source when I first bought my car, but I can't think where.

Anyway, if I've misinformed anyone then I apologize. (And I'll let Tire Rack know they set me up!)

As for the revs per mile thing, it looks like you can't ever convert directly from diameter. Apparently they account for the slightly reduced diameter of a weighted tire.
 
Originally posted by E36S50:
The last two times I have exceeded ~175mph the TCS light has come on and only gone off after I have turned off the ignition. Any ideas?. Could this be the rear tires expanding and tripping the light?. BTW, this is a CTSC'd '92 with 215/40/17 & 265/35/18 S02's.

Thanks
S.M.

You may be airborn! Does the car feel stable? Or, are you in a straight line where you may not notice the instability?

Dave.
 
TCS is designed to reduce engine power for a) handling control, b) rough road control, and c) grip control.

Per the NSX service manual...

"If the control unit detects an abnormality, it shuts the system off and causes the TCS system indicator light to come on."

"If the control unit detects an abnormality, it records a problem code..."

Notwithstanding the tire issue, since you are not suffering a drop in engine power -- and certainly you need all available to achieve this speed -- it may well be that the TCS normally shuts down at this speed.

Let us know the problem code.
 
Hey, I remember someone saying a while back that the TCS light AUTOMATICALLY turns on at 7000RPM's in 5th gear. Look at the 185mph speedo pictures that we have in the gallery here, the TCS error light is on.

I suggest you lift the e-brake handle up one notch, drive until the TCS and ABS are disabled completely, then try the 175mph run again.
 
Well, the good folks at Yokohama responded to my inquiry. The specs given on the Tire Rack site for the OEM rears are incorrect, and therefore so is that part of my assertion. The relevant excerpt from their response:

“The overall diameter of the 225/50R16 is 24.9", and the R.P.M. is 835. Every tire size is going to have a range that the dimensions can fall within. Additionally, the overall diameter is a mounted dimension, but not a loaded dimension. The R.P.M. is a loaded dimension. The tire will always change its dimensions a little bit when under load. I hope this information has been helpful.”

As nsxtasy said, other factors aside, the sizes noted above should be well within acceptable limits for TCS. What we still don’t know is the rim sizes, which makes at least some difference, and the relative growth rate of a narrow tire versus a wide one. Are those sufficient to cause the problem? I’m inclined to think not by themselves, but too little information.


[This message has been edited by sjs (edited 26 November 2001).]
 
SJS, is right, the variations between tire manufacturer or brand are pretty significant.

If anybody in the bay area interested to see in the difference of dunlop SP8000 and sumitomo HTRZ, and Kumho Ecsta 712 in 225/45/16, they can come by to Don at hilltop auto sevice. Don has all three tires in stock. not only the O.D of all three tires are different, but as well as the width.
 
Other systems not directly related to TCS can set off the TCS as well.

I got this a couple of times when redlining around 120mph in 3rd gear. I suspect a bad speed sensor on one of the rear wheels.

Also, when I unplugged my O2 sensors (had to after header install to make the engine run stable...don't ask...long story...), the TCS light comes on and stays on...so by defeating an emissions-related part of the system, the TCS is also affected...why? I have no idea, and neither does anyone else.

So...it could be something completely non-related to TCS...

Andie

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