Have you ever had your car running great, had good speed, and the handling is "right on", then you change your tires and you find it just have the "punch" it did before? Then you've run into the dreaded "roll out" problem.

Not everyone knows that if the new tires you put on are a different diameter then the old ones are, you need to adjust your gear ratio to make up for the difference in tire size.

I've made an easy to use chart that helps you find what gear ratio to use to make up for this.
Here is a small piece of the rollout chart. It is written as a Microsoft Excel spread sheet. If you do not have Excel, you can download the Excel file reader here (http://office.microsoft.com/en-us/assistance/HA010449811033.aspx).

In this example, we were running a tire diameter of 1.80" and a gear ratio 2.15. This equals a rollout of 2.629 (the first red square). We then changed to a tire diameter of 1.90".

To find out what gear ratio we need to change to, we follow the numbers under the 1.90 tire size until we come to a rollout figure that is close to what we had before the tire change. In this case, that number was 2.629.

By using the chart, we see that we need to change our gear ratio to somewhere around 2.25 to 2.30 to keep the same performance that we had before the tire change.

The chart that you download here is zipped, so you will need to unzip it then view it in Excel or the Excel viewer. You can then print it out on your printer so you can carry it in your pit box. The About RC Vehicles Roll Out Chart has been sized so that you can change your printer setting to size your printout to "fit the page" and it will printout nicely. There are two pages included, so make sure you print both pages.

Now, don't waste any more time, download the HobbyTalk Rollout Chart and get a jump on the competition!

Hankster,

The roll out chart is a great thing, but I run pan cars and don't have tires that big. Do you have another chart with smaller tires, say from 2.50 down...for the foam car tires it would really help.

I also found this one: http://www.thercshack.com/index.asp?PageAction=Custom&ID=10

For Pan Cars, just type in '1' for the tranny and it seems to work great.

Hope this helps!

sheet1(2) in the chart has 1.7 - 2.9

If you need smaller, just row 3 values

For those who don't have excel

As Tres said, look at page 2 of the spreadsheet (tab at the bottom of the sheet) for smaller tire sizes. Thanks Tres for providing the pdfs and thanks Spdjunky for providing a link to an on-line version.

I just posted a palm program for calculating the rollout. You can find it at http://home.comcast.net/~cwinters15/rc/rollout_0_1.zip

Enjoy!
Chuck

how do i figure rollout for crc carpet knife 1/12 scale car

all pan cars are the same, as stated above

I just posted a palm program for calculating the rollout. You can find it at http://home.comcast.net/~cwinters15/rc/rollout_0_1.zip

Enjoy!
Chuck


Chuck I have just installed the Rollout Calculator. 0 1 and it works great. tried the 0 2 but it would not work. had to delete both programs and reinstall 0 1. I am very happy with it thanks.:thumbsup:




palm os tm software v3.1 on a visor made by handspring

I also downloaded the Palm program. Works great. Thanks. This beats carrying sheets of paper and a calculator. Now all I need is the Palm.

well in pan car you can figure out roll out if you have a calipier messure tire size times spur times pie`divided by your pinion gear....now you have a quick and accurate way for roll out ....pan car 10th you want around 2.50 for roll out exp....2.10(x)spur 100 (x) pie` 3.1415926535897932384626433832795 ( / ) pinion any questions you can post under oval track dis... mt. pleasant or bay city if you need more help about roll out

I just posted a palm program for calculating the rollout. You can find it at http://home.comcast.net/~cwinters15/rc/rollout_0_1.zip

Enjoy!
Chuck

and here i have a rotting palm pilot... it'll serve some use now in my pitbox.. ahahha.

Thanks all for the feeback all. It's nice to know people have a use for the software.

Bob W.: What is happening with v0.2? Does it crash, or just not work correctly? I never tested on a Visor, so any info you could give me will help to fix the issue.

Everyone else: What version of the palm program are you using?

Thanks,
Chuck

Chuck ......02 crashed on me. it also made the 0.1 crash after 0.2 was installed. I also tried to install 02 after removing both programs, but 0.2 still
crashed.

thanks again

Bob

Mike, grab a caliper...OD x pitch - 2, equals # of teeth

Example 1.905 (OD) times pitch (64) equals 121.92 minus 2 equals 120 tooth spur ;)

The above formula allows you to calculate the number of teeth of an unmarked gear.

Where'd you get this from? OD of a pinion or spur doesn't directly relate to the number of teeth it has, even knowing the pitch. Robinson Racing and Losi pinions aren't the same OD for the same number of teeth. Hence another reason to use the same brand of pinions for one car. Now, if you wanted to specify that formula for a specifc manufacturer, great, but what you posted isn't 100% accurate.

where can i download the roll out calculator and gearing calculator for my laptop?

jeff, if u can get the internet u can goto gearchart.com but i dont think its something you can download to your laptop.

http://www.gearchart.com/index.cfm?fuseaction=chart.create

yeah mike i saw that but where we were yesterday doesnt have internet hopeing to find something like that but downloadable.

this is the thread..

http://www.hobbytalk.com/bbs1/showthread.php?t=127748

this is the pdf

http://www.hobbytalk.com/bbs1/attachment.php?attachmentid=23307

try that?

pinion gear x tire size x times pie( 3.14 or transmission ratio) divided by spur gear


very easy to figure out.

nod... but a quick chart for tire size and all you need to calculate is pinionXspur and then lookie at the chart. sometimes when in a rush its faster? :P

http://www.rctech.net/forum/showthread.php?t=196398


heres your answer jeff.

heres a rollout program for oval racer i hope it help you it was 10 minute project.Dave
75418

hankster or anybody else out there do you remember the chart that was out years ago that was on a sheet of paper that was cut in circle and it had another circle on top of that and all you had to do was turn it until your numbers come up, man that thing was sweet and saved you alot of time but i cant remember the companys name that made them

Dennis, I sell what you are talking about. I designed mine like the old one that you are referring to, but mine will work with brushless motors and different gear ratios also. Works great for carpet pan cars. It is much quicker and easier to use and to see where you are at on the chart, then typing in a bunch of numers. You can see how close you are on the chart to going one way or the other this is some thing that you can not see if you do not have my gauge to look at.

I can not post my info to contact me right now if you wound like one post and I will get back to you some how.

I will post more info tonight when I get home from work.

Heres the 411 on my roll out gauge

Will work with the following
Spur sizes 80-135
Pinion sizes 10-57
Tire Dia. of 1.468 to 2.800

Will work on any scale as long as the numbers are in these ranges.

The cost is $35.00 includes free shipping and are ready to go you do not need to assemble any parts when you get it. You also get 4 tapes for measuring the tire dia. with each order.

Contact me at mlrockytop@gmail.com if you are interested in one or have any questions on it.

Later
Scott
SRP