TCS and 5% rule????

[X-TNSIV]

I'm ording a set of Volk LE37T's for my car now...and here is my question:

does the 5% rule correspond to the rev's/mile or overall diameter of the tire?

I plan in using a 225 width tire up front.

I would like to run a 225/40/18, but if I go by Rev's mile then, they work. But if I go by rolling diameter, then both the 225/35/18 & 225/40/18 won't work.

see chart below:

Front Rev's/Mile B/W Diameter B/W
205/50/15 874 23.1
225/35/18 857 1.945% 24.3 5.195%
225/40/18 833 4.691% 25 8.225%

The wheels are 18x7.5 and 18x9.5

the rear tires are going to be 285/35/18

thanks,
Allen

 

[nsxtasy]

The reason that you're getting different results is that the revs per mile figures above appear to be wrong. They should be:

205/50-15 874
225/35-18 833
225/40-18 804

You might want to try using the tire calculator here.

The outer diameter of your rear tires is 4.0 percent larger than stock.

That means that for TCS to work, the outer diameter of your front tires must be between 1.0 percent smaller than stock and 9.0 percent larger than stock.

225/35-18 is 4.9 percent larger than stock, so those will work fine.

225/40-18 is 8.7 percent larger than stock; while those may work, they are VERY close to not working, and any slight variation (such as front tires that are worn more than the rear) will cause TCS not to work.

Just get the 225/35-18.

I have no idea whether these sizes may rub in your fender wells; my comments refer only to the TCS working properly.

I assume you know that those tire sizes will cause your car to be slower due to the change in "effective gearing", right? It's like having taller gears in every gear. You can avoid this by choosing tires that are slightly narrower and/or lower profile (lower aspect ratio) so that they're closer in outer diameter to stock.

[This message has been edited by nsxtasy (edited 05 August 2002).]

 

[Honda4Life]

Allen-


I run the 225-35-18 up front on a 18x8/45et wheel.....the combo works great! My TCS was not effected at all by the new tire and wheel setup.
The clearance is good with the 225-35-18 in the front too... this also depends on the wheel offset, wheel width, and suspension .... My car is adjusted very low, and I have no rubbing even in hard cornering.

BTW- Good choice in wheels!!! LE37s are very nice wheels, and 18s all the way around looks and feels so awesome.



------------------
www.xlconcepts.com

 

[X-TNSIV]

In regards to nsxtasy:

the figures that I used for Rev's per mile were from tirerack.com's technical specs page for Bridgestone SO-3 polepositions...

see the link below:
http://www.tirerack.com/tires/Spec.jsp?make=Bridgestone&model=Potenza+S-03+Pole+Position

Therefore the specs on the "tire tech" page are incorrect. That's why I was trying to calculate the %'s myself.

does someone know the "Correct" way to calculate the 5% rule using a formula?

this is the basic formula that I'm using:

%=(difference)/original spec rev's or diameter

so will 225/40/18's work?

thanks,
Allen

 

[X-TNSIV]

one more thing...

here are the true specs on the rear tires as well.

tires Rev's/Mile Diameter
225/50/16 811 24.9"
285/35/18 804 25.85"

I'm going with Nitto 555 for the rears, due to the tread life and handling characteristics. I've had a set before on my SL500, and I liked them a lot. Since the front's can only accomodate the 225's, that is why I'm going with a softer compound SO-3 to help prevent under-steer.

Allen

 

[X-TNSIV]

The comment was made that the front tires must be within 5% of the rears, but it was stated in the FAQ's section that the tires must be within 5% of the stock tires.

"The TCS systems tolerance for the ratio is reported to be 5%. As long as you keep the ratio within 5% of stock TCS should work with any size wheels you can mount on the car. See section 4.4 for a list of wheel sizes that NSX owners have tried and the appropriate tire sizes to use with them."

Is this referring to +/- 5% of the front to rear ratio, or +/- 5% of the stock tire size?

I just don't want to waste my time on ordering the wrong tires....

Allen

 

[nsxtasy]

Originally posted by X-TNSIV:
Is this referring to +/- 5% of the front to rear ratio, or +/- 5% of the stock tire size?

The ratio of the front outer diameter to the rear outer diameter of the tires must be within 5 percent of the same ratio for the stock tires.

Method 1

On the '91-93, the outer diameter of the rear tires is 7.75 percent larger than the front. That means that the rear outer diameter must be 2.75 to 12.75 percent larger than the front to work.

On the '94-01, the outer diameter of the rear tires is 4.65 percent larger than the front. That means that the rear outer diameter must be 0.35 percent smaller to 9.65 percent larger than the front to work.

Method 2

Regardless of year, if you increase the outer diameter of the rear tires by x percent from stock, then you must change the outer diameter of the front tires between x-5 percent and x+5 percent from stock for the TCS to operate properly.

[This message has been edited by nsxtasy (edited 05 August 2002).]

 

[nsxtasy]

Originally posted by X-TNSIV:
In regards to nsxtasy:

the figures that I used for Rev's per mile were from tirerack.com's technical specs page for Bridgestone SO-3 polepositions...

see the link below:
http://www.tirerack.com/tires/Spec.jsp?make=Bridgestone&model=Potenza+S-03+Pole+Positi on

Therefore the specs on the "tire tech" page are incorrect. That's why I was trying to calculate the %'s myself.

does someone know the "Correct" way to calculate the 5% rule using a formula?

this is the basic formula that I'm using:

%=(difference)/original spec rev's or diameter

so will 225/40/18's work?

No, they won't.

There is a basic problem with the way you were doing your calculation: you were mixing tire calculator numbers with spec sheet numbers.

The tire calculator calculates the outer diameter as the wheel diameter plus twice the sidewall height, where the sidewall height equals the tread width times the aspect ratio.

The spec sheet presumably does the calculation by measuring this particular tire.

A tire calculator calculates tire diameters, and divides them into a mile to compute revs per mile:

205/50-15 23.07 874.2
225/35-18 24.20 833.4 +4.90 percent
225/40-18 25.09 803.9 +8.74 percent

Using a tire spec sheet should give you similar results, AS LONG AS YOU ARE USING IT FOR ALL YOUR CALCULATIONS. In other words, you can't take the above calculations from a tire calculator and mix them with figures from a spec sheet, which is what you did.

If you use the figures from the Bridgestone table on the Tire Rack site, then you need to use those figures for all sizes, which gives you the following:

205/50-15 23.1 902
225/35-18 24.3 857 +5.25 percent
225/40-18 25.0 833 +8.28 percent

As you can see, the results are very close to those of the tire calculator, now that you are using the figure of 902 revs/mile from the Bridgestone chart instead of the figure of 874 revs/mile from the tire calculator.

[This message has been edited by nsxtasy (edited 05 August 2002).]

 

[nsxtasy]

Originally posted by X-TNSIV:
I'm going with Nitto 555 for the rears, due to the tread life and handling characteristics. I've had a set before on my SL500, and I liked them a lot. Since the front's can only accomodate the 225's, that is why I'm going with a softer compound SO-3 to help prevent under-steer.

It's a very bad idea to use different kinds of tires front vs back. Definitely not recommended.

I suggest you find a tire (the Nitto 555 or the Bridgestone S03 or some other tire) and find sizes for both front and rear for your car, so that you can use a set of four of the same kind of tire.

[This message has been edited by nsxtasy (edited 05 August 2002).]

 

[NSX_PDX]

Great advise! I had to run different treads on my Triumph on track day and the car was OFF! I know it could have been a bad combonation, but it was the worst day in 15 years of owning/tracking the car.

 

[X-TNSIV]

Originally posted by nsxtasy:


There is a basic problem with the way you were doing your calculation: you were mixing tire calculator numbers with spec sheet numbers.

nsxtasy,

I REALLY appreciate your help on this subject!

in correspondence to the quote above...I wasn't intentially mixing the two specs. I used the specs directly off of the nsxprime tire section in the FAQs section, so I assumed that the rev's/mile and diameter were accurate for the factory Yokohama tires. If they were pulled off of the powerdog's webiste, then I was using the 'incorrect figures', but if they are for the factory tires...then my calculations should be accurate.
http://www.nsxprime.com/FAQ/TireWheel/tiretech.htm

does anyone know where the figures where derived?


as far as using mixed tires...I understand your concerns and I will take it into consideration before ordering the fronts. But the Nitto's have been ordered for the rear.

Allen

 

[nsxtasy]

Originally posted by X-TNSIV:
does anyone know where the figures where derived?

They were almost certainly taken from a tire calculator, since they match those figures exactly. (Also, spec sheets on the OEM tires are rather hard to find.)

Originally posted by X-TNSIV:
as far as using mixed tires...I understand your concerns and I will take it into consideration before ordering the fronts. But the Nitto's have been ordered for the rear.

I see from Nitto's website that the Nitto 555 comes in 225/35ZR18, the front size you were considering that works with the rear size you've ordered. And, using the revs per mile for the two sizes (859F, 800R) shown on the website for the Nitto 555, you find that the rear is 7.4 percent larger in outer diameter than the front - almost exactly the same ratio as stock. So TCS should not have any problems with these sizes.

[This message has been edited by nsxtasy (edited 05 August 2002).]