Hi guys, you seem to be a knowlegeable bunch, so let me ask you a question. I just installed my Trail Tech, and I can't get the circumference dialed in. My preliminary runs experienced a top speed of 146.7 mph. Approximately double what I really did. I re did the 2*pi*radius equation (thanks to my geometry class[img]i/expressions/face-icon-small-wink.gif[/img] ) and it got down to 80.3 mph. This is completely stock, wide open on my road. I don't want to do many more road runs since I am only 14, and don't want my license witheld. What are your suggestions on getting this deal accurate? I don't have too many flat open areas to run beside a car, but my dad may help me do that someday.
Thanks for the input.

 

Thats sounds close enough to me. Isn't like 78 mph the claimed top speed?

Another method that you can use is:
1. Make a mark on the ground and your front tire.
2. Line up the two marks.
3. Drive your quad foward until the tire rotates one complete rotation.
4. Make a new mark on the ground that lines up with the mark on your front tire.
5. Measure the distantance between the two marks.
6. This is your circumference.
7. To convert inches to mm, multiply by 25.4.

Want more accurate? On step number 3, rotate the tire more times. After step number 5, divide by the number of rotations.

Simple as pie! (pun intended)

 

I agree.. I did the MATH like you first and it was not right. Do it the easy way. just like the above directions.

 

Actually, my math was much closer than the string around the wheel, as well as the mark on the ground methods. I used the mark on the ground and got 62 inches exactly, and multiplied that by 25.4 to get the mm, as you said, and got 1574.8mm. This is the measurement that produced the 146.7 mph top speed. I then used the string around the largest circumference of the wheel and I got just under 62 inches. With my calculation of pi (3.14159...) multiplied by the radius (21 inch tire, by my measurement, not the stated size. 21/2 = 10.5) multiplied by two, I got 65.97. Multiply that by 25.4 and you get 1675.7... mm. This produced the 80mph result. I don't understand how just 101mm can make that huge of a difference.

Thanks for the input, I will try everything from scratch again and report my results.

(Edit: I believe the top speed of the DS is somewhere around 72mph, but I could be wrong)

 

I think that you have it set to KM/H when you get 146.7.

 

Yes the 140's is what mine reads when I forget to change it to MPH.
If your stock on flat ground you can hit 81 mph.

 

you say that a stock ds will hit over 140km/h? i thought it was only in the 130's, i wonder wat mine will do wit the 22" on it

 

If you want to go really fast, just set your wheel circumference to 9999mm on your speedometer and set it at KM/H. You will think that a Indy car is slow, by comparison.

 

I'll try to get a pic of the top speed on my website (along with tons of other stuff) since I think it actually was in mph. Anyways, it makes no difference since I know I wasn't going 146 mph.
Later