RTI Ramp Information and Calculations
By Steve Henderson
The information found in RTI history was borrowed from sources on the web, conversations, email, discussions and memory so I take no responsibility for it's accuracy. This is always open for revision or improvement so if you see anything wrong or would like to add anything please email the webmaster.
RTI Ramp History
It's believed that the RTI ramp was originally designed by Four Wheeler magazine, for what purpose I'm not sure, but all the information I can find seems to point to it's use to measure a rigs capability. RTI stands for Ramp Travel Index, which is basically a percentage of your wheelbase. The RTI ramp serves two basic purposes, bragging rights and testing. RTI scores have become a measure of how capable your rig is on the trail. The higher the RTI score the better your rig should be on the trail, in theory, and the more bragging rights you have. A RTI ramp is also a great way to max out your suspension to determine if new modifications made an improvement, how much of an improvement, check for binding, rubbing, make sure things, like brake hoses, aren't going to break on the trail, etc. I prefer it's use for the latter, but RTI ramp competitions can be alot of fun. The original ramp standard was a 20 degree ramp, but with the advances in suspension design and technology we are seeing an increase in ramps that are 23, 25, and 30 degrees. The Katy chapter ramp is a 25 degree ramp.
RTI Ramp Competition Rules
The rules here are to ensure fairness and equality for all rigs when competing for the Ramp King title!!!
Tire pressure must be equal in all four tires.
Shocks must be mounted.
No scoring on ramping in reverse.
No "riding the rail". You must travel up the center of the ramp.
RTI Ramp Measurements
There are several methods of taking RTI ramp measurements, but we prefer to measure from the bottom of the tire on the centerline of the hub to the ground.
RTI Scoring
As with measuring there are several methods of scoring. The method we chose can be applied with or without a RTI ramp. If you have access to a forklift, neighbors brick wall, or other method of lifting one tire off the ground then you can use the following formula to determine your RTI score on any degree ramp. You'll need two measurements to calculate your score, the wheelbase of vehicle from the center of the front axle to the center of the rear axle and the distance from bottom of tire raised off the ground to the ground.
Figure 1
Thanks Doug Chartier, for the graphic and explanation.
The calculation is (a/sinA)/wheelbase x 1000 or Distance of lifted tire from ground divided by the sine of the ramp angle you want to calculate for equals the distance traveled up the ramp. Next you use the standard RTI formula, distance traveled up ramp divided by wheelbase times 1000. To make this easier use the sine table below or, for you really lazy folks click here for a page you can just plug your numbers into.
Sine Table
17- .2924 22- .3746 27- .4540
18- .3090 23- .3907 28- .4695
19- .3256 24- .4067 29- .4848
20- .3420 25- .4226 30- .5000
21- .3584 26- .4384 31- .5150 |