Outer Limits 4x4 Board

Here is some information regarding RTI ramps it based on stuff I have done with the RTI ramp and what I have gathered from magazines and the net.


RTI is it a LIE…?

Is the RTI ramp biased for a specific type of vehicle..? Whilst you could build a rig to conquer the ramp it would not necessarily be the best trail or crawling 4by. Though it is also important to remember that a rig that does have a large RTI may still be fairly capable but it is the whole package that counts.



So we all know what a RTI ramp is or here is your chance to learn, a platform normally set at 20egrees or 30degrees…? You drive up the ramp until a tire starts to lift off the ground and then measure the distance traveled up the ramp. The measurement is divided by the wheel base of your vehicle and multiplied by 1,000 to give your RTI number. It seems foolproof but there are many ways to look at it.

Distance up ramp
Vehicles wheelbase X 1000 = RTI number

Basically RTI ramps favour short wheelbases and wide track widths. If you assume that a higher RTI number makes a vehicle better for the trail, then lets imagine the perfect RTI 4by, This vehicle would have to have the shortest Wheelbase possible, say a Sierra with 35â€

makes me wanna get mine on a ramp again to test my latest suspension mods.

Anyone know when the next melb ramp day is?

re-match.

10psi all round
inside of tyre fully on ramp
and get out the set squares.

And on that Note the Suzuki's Came in 1st 2nd and 3rd at our local RTI ramp day. These are road registered 4bies remember scoring over 1000RTI which isnt too bad.

Sikid (with a Vitara) came in Second and I came in 3rd

no its not a lie.
RTI is RTI

but it means bugger all.

like you say its not necessarily the best trail rig, there is a blalance that a truck needs and its different for all.

I was in Tuff Truck 06 and came 32 out of 35 in the travel ramp
and came 8th overall in a zook

its just another activity that can be performed by a 4wd, I think its only real use is to see if your suspension fouls or binds, but is slill not the same as the flex a truck will get on a trail.

good to see some tech

enjoy
ashley

germo wrote:no its not a lie.
RTI is RTI

but it means bugger all.

like you say its not necessarily the best trail rig, there is a blalance that a truck needs and its different for all.

I was in Tuff Truck 06 and came 32 out of 35 in the travel ramp
and came 8th overall in a zook

its just another activity that can be performed by a 4wd, I think its only real use is to see if your suspension fouls or binds, but is slill not the same as the flex a truck will get on a trail.

good to see some tech

enjoy
ashley

Perfect example of this is the BBM scat (no offence to those involved with this build, i loved it ). Look at the flex pics, it got 4th from memory. Yet it was all rear end work, front barley moved. Lots of flex, but no balance. Please not, i am not having a shot at the car or builders, just pointing out something.

Layto....

All of a sudden its 1999!

The US mags have done this issue to death. FourWheeler first started using an RTI as part of the 4X4 of the year testing in, abour 1991. When they started TTC in '93, they took it out to Hollister hills to form part of the empirical score.

By about '95, they had to go to a 30deg ramp.

JP mag (or was is Petersens?) ran an article where they got Cappa's old flatty to improve its score about 300 points by airing down tyres, disconnencting shocks and pulling out shackles, just to prove that an RTI score doesn't mean you have a drivable car.

RTI is a useful setup tool to assist with many aspects of suspension and car behaviour, but it is not a useful comparison between two different vehicles, and has even less to do with capability.

However, RTI can be used to empirically measure how well a vehicle balances. It is possible to calculate the percentage of total articulation that is being achieved by the front axle when driving up a ramp. Obviously, ideally, 1/2 of the articulation would be being done by each axle, but this is very hard to achieve with most setups.

Have a look at this site:
http://www.yellowdefender.com/twist_off ... ff_result/

This is one of the best examples of how to use a ramp for good rather than evil.

Cars photographed reversed up ramps make me laugh as it is a sure sign that that car has rubbish balance.

On another note, the 30degree ramp is not just harder to score on because it is steeper, the secondary effect is that the steepness transfers more weight to the rear of the car so it will actually make the front end flex less as it has less weight on it.

Steve.

A score of 1000 on a 20 deg ramp is really nothing to write home about, but if you can manage that score on a 30 deg ramp (as used at Tuff truck), you have acheived something! But as Germo and Layto rightly say, it means squat in the bush. When was the last time you saw a ramp at Menai or your local bush track? Balance is the key.

Any score on the steep 30 degree ramp is more difficult to attain than the same score on a shallower 23 or 20 degree ramp.

as said in the post, and as Rick has said scoring 1000 on a 30degree ramp is a achievement but also if your getting that kind of score your vehicle is most likely not driven or registered to go on the road anymore.

As for scoring 1000 on a twenty degree ramp for a Hilux or 80series or any other long wheelbase I wreckon that is a pretty good achievement, that is quite alot of suspension work to get that kind of score especially for a road going 4by.....

MUDPIG, sorry if this sounds agressive, don't tank it the wrong way but I'm not really sure what your point is. you are posting lots of tech about something that everyone else is trying to tell you is pretty much meaningless. Did you even read http://www.yellowdefender.com/twist_off ... ff_result/ ? You should have had a pretty good handle on what you can achieve with a ramp once you had read this.

In realtion to your point about wide, short cars ramping well- Lets drive a sierra with hilux diffs and a hilux up the ramp THE SAME DISTANCE. The sierra might be ramping 1000, the hilux maybe 700. Both cars are, in fact, at that point, articulating their suspension exactly the same amount. However, the hilux should, assuming generally the same suspension set up (lets assume both cars are SPOA) be sitting "flatter"- i.e it will be less nose up, and therefore feel more stable and balanced, this is the effect of the longer wheelbase.

This is why the steeper the terrain you want to drive, the more wheelbase you require. But, conversely, the worse RTI score you would get. This is just one way that RTI is a crock.

The numbers this relates to on an RTI ramp cannot be compared from vehicle to vehicle and really mean anything. The (might) only be useful when you change something on your own vehicle in comparing before and after.

Most critically, cars with drop shackles and other stupid poser crap ramp really well- RTI doesn't measure how stable the car is, how equal the wheel loading is, or how spooky the car feels when it is in that position.

I have even seen people boast about their RTI when reversed up the ramp (go ahead and drive up hills in reverse then!)

Leave RTI for posing and get on with building a balanced, capable car for the terrain you actually drive rather than a ramp.

Steve.

a real test should be ... work with me here .....


vehicle parked on flat ground
measure wheel track
using 2 fork lifts , lift Front right and Rear left at same time , till one of the other tyres lifts.

assuming here the Rear right lifts off the ground , take a measurement of the Rear Left from ground to the lowest point of the tyre.

to calculate Articulation Index

Height lifted divided by
wheel track
multplied by 1000

granted it still doesnt test real world seat of the pants offroad capablity
but if you were to have a front to rear flex ratio as part of the score it would put 4x4s with 50/50 front / rear flex 1st and ramp champs like the SCAT back to the rear of the field where they belong.

ToyTruck wrote:a real test should be ... work with me here .....


vehicle parked on flat ground
measure wheel track
using 2 fork lifts , lift Front right and Rear left at same time , till one of the other tyres lifts.

assuming here the Rear right lifts off the ground , take a measurement of the Rear Left from ground to the lowest point of the tyre.

to calculate Articulation Index

Height lifted divided by
wheel track
multplied by 1000

granted it still doesnt test real world seat of the pants offroad capablity
but if you were to have a front to rear flex ratio as part of the score it would put 4x4s with 50/50 front / rear flex 1st and ramp champs like the SCAT back to the rear of the field where they belong.

To be quite honest - the real test is stop pulling your appendage on a metal ramp and drive the fawking thing.Ramps comps are for posing full stop.

Layto....

lay80n wrote:To be quite honest - the real test is stop pulling your appendage on a metal ramp and drive the fawking thing.Ramps comps are for posing full stop.

Layto....

BWAHAHAHAHA

Best reply by far

i 100% agree

Gwagensteve wrote:MUDPIG, sorry if this sounds agressive, don't tank it the wrong way but I'm not really sure what your point is. you are posting lots of tech about something that everyone else is trying to tell you is pretty much meaningless. Did you even read http://www.yellowdefender.com/twist_off ... ff_result/ ? You should have had a pretty good handle on what you can achieve with a ramp once you had read this.

In realtion to your point about wide, short cars ramping well- Lets drive a sierra with hilux diffs and a hilux up the ramp THE SAME DISTANCE. The sierra might be ramping 1000, the hilux maybe 700. Both cars are, in fact, at that point, articulating their suspension exactly the same amount. However, the hilux should, assuming generally the same suspension set up (lets assume both cars are SPOA) be sitting "flatter"- i.e it will be less nose up, and therefore feel more stable and balanced, this is the effect of the longer wheelbase.

This is why the steeper the terrain you want to drive, the more wheelbase you require. But, conversely, the worse RTI score you would get. This is just one way that RTI is a crock.

The numbers this relates to on an RTI ramp cannot be compared from vehicle to vehicle and really mean anything. The (might) only be useful when you change something on your own vehicle in comparing before and after.

Most critically, cars with drop shackles and other stupid poser crap ramp really well- RTI doesn't measure how stable the car is, how equal the wheel loading is, or how spooky the car feels when it is in that position.

I have even seen people boast about their RTI when reversed up the ramp (go ahead and drive up hills in reverse then!)

Leave RTI for posing and get on with building a balanced, capable car for the terrain you actually drive rather than a ramp.

Steve.

Nah none taken dude, I thought I would put up some tech on a topic, I know a lot of guys on here Im sure have heaps more modified or capable 4bies than me in in no way was this a pose though photos make it more interesting too read and get a idea if your new and learning. I just thought I would have a go at some tech for people wanting to learn about RTI and at the end others could add there knowledge and other good sites like the one provided. The reason I brought it up was that we just had a RTI day up here for our local forum and whilst it was a fun day to meet up I think I was nearly the only person checking out what was on bump stops and how close other things were too hitting something else like my steering link too the chassis.

Yes I did read through the yellow defender site as well it was a good read some very technical stuff. I agree with you on comparing the Hilux too a Sierra with Hilux axles and again on trails they are both going to be capable and the Hilux may have better balance because of the wheelbase but again there is the other side the Sierra has more clearance in the middle before getting hung up on something it could go on forever.