2019: Why are TT's faster than Class 1 buggies?

michael.gonzalez

Well-Known Member
Alright,

Let's say you are driving a fire truck....but wait for it.... IN THE DIRT (Fire truck weighs 10k empty for illustrative purposes)
Anyways, Your water tank is empty (25%) so you are sitting at 12,500lbs.
You're driving down a dirt road going 60mph alongside your friend.
Your friend is also driving a fire truck. (Don't ask me why you and your friend both have fire trucks). His tank is half-full (50%) (Or half-empty depending on how your day is going). He is sitting at 15,000lbs.

You both have a "brake-off". 60mph to 0mph.

Ten times. Each time you both stop at the same distance. You want to win the 11th time, should you drain your tank or fill it up?
 

Bro_Gill

Well-Known Member
Funny you bring this up. In ACTUAL TESTING of this very situation, it was found the heavier truck had a better stopping distance because there is so much weight transfer to the front wheels, it became impossible for them to lock up, allowing better and safer braking. FYI- Most fire trucks use really narrow tires for their weight, but very large diameter. And an empty fire truck weight more than twice what you must think it does. full of water and tools, 3 times as much. But keep having fun thinking the computer models are correct when real life has shown they are off a bit.
 

Radiobirdman32

Well-Known Member
I'm no physicist but the way I see the weight being a positive factor is that with the advent of such quantum leaps that have been achieved in suspension technology in the last 15 years, the trucks body, frame etc stays pretty stable while the wheels follow the contour of the track. In the old days the buggies bounced over everything moving the whole car up and down as the suspension just wan't there yet. Once the trucks started to weigh 7000 lbs. and the suspension, in some cases 34", advanced, the driving compartment of these beasts began to stay more stable with just the wheels rising and falling according to the terrain. Add of course 900 HP to push them and drivetrains that will stand up to the abuse and that is where I think the weight can be an advantage. Just my 2 cents.
 

jcorsico

Well-Known Member
Concerning braking, the only difference is the friction coefficient.
Michael - you have the correct physics formulas for friction, but only for uniform materials that do not disintegrate when subjected to load. A tire interacting with a road/dirt surface is way more complicated than those formulas suggest.

For example, there is no consistent coefficient of friction for "dirt". Dirt is millions of small particles that roll and slide past each other. It's kind of like a fluid. I'm guessing that the coefficient of friction for dirt changes depending on the load placed on the dirt. But that's just a guess. No load = particles can easily slide past each other = low coefficient. Heavy load = particles get compacted together = higher coefficient of friction. ???

A similar mathematical problem happens on pavement. The coefficient of friction of rubber varies based on the load placed on the rubber. Plus, when a tire slides on pavement, there is a combination of (1) sliding between the rubber and the pavement (friction) and (2) the rubber shearing apart, leaving rubber stuck to the road (that's a failure of the rubber itself, and is not friction - you'd have to model the force required to rip rubber apart, which varies based on temperature, and temperature changes a lot in a race tire from second to second through a turn).

So from a 50,000 foot view, your formulas are correct. But the actual interaction between the tire and the ground is super super complicated.

The TTs are faster than buggies for a host of reasons mentioned in this thread. There is no single silver bullet. It's all the small differences added together that make them faster.
 

Bro_Gill

Well-Known Member
Changing a cam, going from 4 piston to 6 pistons in a caliper, etc... really do nothing to harm weight, but do improve performance. But what does that matter, The formula says...
 

Honda48X

Well-Known Member
Have you heard of the term: A object in motion tends to stay in motion. Let’s put it this way. A heavy object tends to take longer to slow down then a lighter object. Same brakes, same dirt, and I guarantee you a lighter vehicle will stop faster. Is this that hard? I can’t believe I get sucked into these stupid discussions. Lol
 

J BomBer

Well-Known Member
trophy trucks stop faster cause of weight, less slide, just like a loaded semi truck stops faster then a unloaded, why? Cause the unloaded has more of a chance to skid.
 

Honda48X

Well-Known Member
trophy trucks stop faster cause of weight, less slide, just like a loaded semi truck stops faster then a unloaded, why? Cause the unloaded has more of a chance to skid.
Seriously JJ. You take a Dodge 3500 and I will take my Toyota Tacoma and we will do 70 miles per hour on sand and apply the brakes at the same time. I will give you the Toyota if you stop in a shorter distance then me. Not gonna happen!
 

novaman64

Well-Known Member
trophy trucks stop faster cause of weight, less slide, just like a loaded semi truck stops faster then a unloaded, why? Cause the unloaded has more of a chance to skid.
Oh boy, lets science this...

Given the same brakes, and tires, ground PSI affects traction. The lower the ground PSI, the more traction (wide tires, tracks on track steers, etc.). More weight increases ground PSI, which decreases traction and decreases deceleration.
 

isdtbower

Well-Known Member
Since the first years of KOH I have been taking race video for their promotional use. But now the pro’s have taken the burden so I can go back to focusing on suspension video in challenging sections. First it was to see issues in the whoops, Then IFS. Then suspensions that turned better (geometry). Last year was a spot combining most. I had not thought about looking at braking as that is kind of an individual driver thing and how they set-up for a corner…or when they saw that ditch. I usually like to take video of each rig so they can compare or evaluate against others. Last year I found a spot with a slight uphill. medium whoops, a braking section to turn around some rocks and then accelerate on up the hill. Nothing super technical but where seconds could be lost in a 100 yards.

Here are three videos where you can compare.Every Mans challenge cars (usually front engine straight axle), KOH rigs (front and rear engines, IFS and SA, 500-800HP). And, in between, the T1’s had their race. I “was prepared” for faster, but I was not prepared for later and harder braking. Personally, I found a more comfortable position behind much bigger rocks. I only went thru these quickly, and not at editing s l o w speed….. But it looks like the T1’s have less spring or antidive in the front so the tires will follow the ground better….???? Or they don’t set up for droop?? Or the front motor weight plants the front as the rear weight is not high enough to make a COG change??

Anyhow here they are for comparisons. It would really be cool to find the same types of sections and edit out TT vs Class 1 to see the differences.

T1’s and KOH rigs are different animals. I doubt the TT”s were much faster than 20mph over a competitive KOH rig on the “T1 course.” But I was surprised at how quick the T1’s were. Accel, braking, and even some in turning. But, of course, the other KOH laps require articulation and other items for “real rocks.”

The Every Man Challenge had some pre-running whoops. T1’s made some good whoops for the 4400 class rigs the next day.


EMC 2019 Mile 87 or so.

TT-T1 2019

4400 2019
 

isdtbower

Well-Known Member
Given the same brakes, and tires, ground PSI affects traction. The lower the ground PSI, the more traction (wide tires, tracks on track steers, etc.). More weight increases ground PSI, which decreases traction and decreases deceleration.
Am I reading this wrong?? As a offroad biker wanting to stop. would you shift your weight way to the rear so the front would skid....or move more centered or toward the tank to "plant" the front wheel (just under skidding) and just let the rear skid. Only talking stopping....Not trying to carry speed thru a corner....
 

novaman64

Well-Known Member
Backwards, more weight increases traction, less weight decreases traction and more of a chance for tire skid, or spin.
If that were the case (in relation to ground pressure) why does a doezer use tracks instead of tires then? Tires would apply more pressure to the ground than a track. The track puts less PSI on the ground than a tire would.
 
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