How Important Is Ramp Travel Index (RTI)?

Humvee4us

New member
Which setup would be preferred for rocks and deep ruts, 35" tires with a ramp travel index (RTI) of 700 or an RTI of 832 but only 33" tires?
 

jadmt

Well-known member
articulation is nice but belly clearance is also important. depending on the tires some times there is a bigger difference than simply what is marked on the tires for actual size. ie with some 35's are are close to 35's say true 34.5 where some 33's might really be 31.5 so you end up with a 1.5" more ground clearance. Also when airing down you lose clearance which of rock crawling you want to do.
 

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Shovel

Dreaming Ape
This is the same question you asked a day ago. Often when people ask the same question repeatedly they are trying to will a specific answer into existence because they do not like the actual answer. If you tell us what answer you want, maybe we can fabricate an inventive justification so you can feel good when you ultimately do the thing you've already decided you will do.

As for the value of RTI on routes which do not inherently present a roll-over risk if you have sufficient torque distribution (limited slip, lockers, etc) for the terrain then RTI doesn't really matter at all. Example Video: LINK

On routes which present extreme changes of elevation within the length of your vehicle - equivalent to what you would see on a 20 degree ramp for example, then you run the risk of building up axial momentum when weight transfers between diagonally opposed wheels. On a vehicle which would keep all four wheels in contact with the ground, any such axial change is damped by the shock absorbers so the speed of the weight transfer can be metered by the speed of travel. In practice this means a somewhat wider margin of safety when encountering a significant change in angle. The result of insufficient articulation at the wrong time is pretty clearly illustrated here LINK - it's impossible to predict whether that outcome would have been different with greater articulation but if we imagined that vehicle with double the suspension movement at both ends then in the three-wheel situation demonstrated there the body of the vehicle would have already been lower to the ground by better averaging the elevation of all four tires, and a portion of the weight transfer between the rear right and front left tire would have been damped by the shock absorbers to keep that weight transfer and the axial momentum it represents at a minimum speed.

The question no forum can answer for you is which kind of terrain situation you will encounter more and how you will choose to drive in those varied terrains.
 

Smileyshaun

Observer
Rti numbers are for car shows and bragging rights , you could have two rigs with a 700 rti score but at that point one could be on the verge of tipping over and the other could keep driving up the ramp with a tire dangling and still feel stable .
 

1stDeuce

Explorer
I too think your question is loaded... Are we talking about running bigger tires in the mud or snow? Then bigger tires will get you farther than smaller ones no matter what your RTI is. Rock crawling? I'd probably go with better RTI over tires with 1" more clearance.

RTI does count for something, at least at the extremes, as it is a measure of the vehicle's ability to flex and accomodate obstacles without lifting tires. If you're in a vehicle with really poor flex, you're lifting tires all the time, and a tire in the air is one less tire making traction. Given two otherwise identical vehicles, the one with better flex will obviously do better offroad...

Want to look cooler while offroad? DEFINITELY go with the bigger tire and less flex. Lifting tires makes the trail look hard and makes for cool photos.

I built my TJ for Moab originally, before the damn side by sides and rock buggies tore it all to hell. My buddies all had YJ's. We all did the same trails, but they had tires in the air all the time. I don't recall ever managing to even lift a tire hardly. Same line, same obstacle, their pics are "cool", mine look lame. For the most part, we all went the same places though. I just made it look easy, and with less pucker factor. And smaller tires... :)

FWIW, I found that my tires rubbed hard enough on the front fenders at full stuff to bend the inner lip, especially if I was turning. Instead of limiting travel, I chose to keep my travel and put a 3/4" body lift on the Jeep, along with a 1" motor mount lift. Now I have no rubbing, 1" more clearance under the oil pan, and very nice suspension geometry. Perhaps you can think outside the box and get 35's to fit without limiting up-travel... ??
 

billiebob

Well-known member
Which setup would be preferred for rocks and deep ruts, 35" tires with a ramp travel index (RTI) of 700 or an RTI of 832 but only 33" tires?
Are you rock crawling with a dedicated rock crawler and zero camping stuff?
Or overlanding with an RTT, food, cooler, and camping stuff.
Or will you drop a trailer at base camp.

Cuz as soon as you throw an RTT and rack on the roof, the last thing you want is a high ramp score. You want stability.
Ramp Index indicates all 4 tires are in contact making traction limiting wheel spin.
2 selectable lockers on anything will do the same thing.

But if you want good answers, you need to tell us what you are doing and where.
Deep ruts say ground clearance.
Rocks say articulation.
 
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As Scooter

Observer
Well, we can pit it another way. Some people have a blood sugar that may normally run at 150, which is considered prediabetic, but is a concern, yet they live their life normally and are quite athletic. Others can run 100 and be morbidly obese. The numbers are just indicators of performance. There are guys out there that can take an IFS with minimal travel on a trail that guys with high flex jeeps cannot accomplish.
 

Kraqa

Member
coming from the rock crawling world and ultra4 racing. RTI has little impact on vehicle capability.

flex is needed...but too much flex can be a bad thing. the real test is compare a vehicle with open difs and a HUGE RTI number.......to a vehicle with lockers and a very low RTI. Lockers will win nearly everytime.
 

dvdswan

Member
Lockers are the way to go for sure. Keeping the tires on the trail helps too. But on a side note, a winch is also needed. It's not fun digging for hours to get a locked vehicle unstuck. Just my .02.

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nitro_rat

On a Suburban Excursion
RTI is a meaningless number by itself. It's only usefulness is to factor out wheelbase advantages when comparing the ramp travel of a short wheelbase vehicle such as a CJ-5 to that of a long wheelbase vehicle such as a Suburban. A Suburban with less travel than the Jeep can go farther up the ramp than the Jeep can simply due to its longer wheelbase. The "RTI" makes the Jeep look better in a ramp travel competition in a magazine when it's competing against anything else. That's why RTI even exists.

It's a useful number when comparing the results of modifications back to back to see how much travel you gained.

RTI usually can't be compared directly because the angle of the ramp also plays a factor. All ramps aren't the same angle so #'s from one ramp to another can't always be compared (unless of course you know the two ramps are the same angle).

Leave RTI where it belongs, in the magazines...
 
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