# RTI calculation

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by k5king, Aug 29, 2001.

1. ### k5king1/2 ton status

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<font color=green>i know the distance/wheelbase x 1000 = RTI ,,,, but does it matter what the angle of degree's the ramp itself is or what ? and should you ramp it in 4 wheel or in 2 wheel ? on my 79 pick-up with 39.5's 4 inch susp.,,3 inch body,,i can ramp an 800 on a 7% ramp in 4x4 untill i rub,,i don't lift a wheel.,i can get it to ramp about 650 in 2 wheel,,but that's cause no bed weight on it,,wooden flat bed, i can't get traction in the gravel to make it twisty so what's the usual ? 4x4 or not, and does the ramp factor in somewhere also ? i know that 7 is far from 30,,but it get's awful twisted up round 8 feet </font color=green>

<font color=purple>ANYBODY LOSE THEIR JEEP????????
I JUST FOUND ONE UNDER MY BLAZER!!!!
</font color=green>

2. ### Jeff4271/2 ton status

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<a target="_blank" href=http://lyonsdesign.bizhosting.com>Lyons Design Web Site</a>

3. ### 6.2Blazer1/2 ton status

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The idea behind this is basically how far you can raise one tire (typically one of the fronts) off the ground and still keep the 3 other tires touching the ground, so it's a test of suspension flexibility and not traction. So basically do it in 4x4. I have seen trucks with open front and rear differentials that can't get a true reading because of lack of traction...they can't pull themselves far enough up the ramp to completely flex the suspension, while trucks with just one rear locker could drive off of the end of the ramp...though at least one tire would be in the air at least part of the way up.

Yes, the angle of the ramp makes all of the difference concerning what you "calculate" the RTI as. The truck will flex the same no matter what the ramp is, just the so-called number will change according to the ramp angle. This is because the steeper the ramp is, the less distance forward you have to drive to get the tire the same distance up on the ramp.

For example, let's say you took a forklift and picked up up one of the front tires and could raise it 2 feet off of the ground (bottom of tire to the ground) before any of the other tires on the truck came off the ground. If you then drove it up an "RTI ramp", then the tire would still be 2 feet off of the ground when one of the other tires started to lift, no matter what angle the ramp is.

The difference is that on a 7 degree (I'm assuming you mean 7 degrees and not 7 percent) ramp, you have to move the truck forward about 16 feet (200") before that front tire is 2 feet off the ground. Assuming approximately a 100" wheel base (to make calculations easier), you would score a 2000. Now try that on a 30 degree ramp and you would only score a 480 because you would only drive up 4 feet (48") up the ramp before having the front tire 2" off of the ground. And finally, on a 20 degree ramp you would score a 705.

It's all just a numbers game, the truck flexes the same amount each time but the angle of the ramp dictates the RTI for that particular angle of ramp.

I don't know your wheelbase, but using our example of a 100" wheelbase and ramping an 800 on a 7 degree ramp, that would translate into ramping about 200 on a 30 degree ramp. As the wheelbase of the truck increases, this number will go down.