Thread: Scary moment on general grabbers

Originally Posted by weeds

i have never driven a car with tracton control but i didn't think TC would come into play cruising on unsealed roads as i thought you have to loose tracton for TC to work......is this with CDL engaged or dis- engaged?

My apologies. I meant to say ABS not TC although my understanding is that they are both on the same fuse, happy to be corrected. I have had the car fishtail badly with the CDL both engaged and disengaged and each time it has been when I've applied the breaks on a loose gravel road. On very long unsealed stretches that are in good condition I will drive too fast for the conditions (most people do I think) but with the fuse pulled I havent been able to get it to fishtail in the same way. By the sounds of it not the OP's problem though.

It's a 1992 so traction control isn't a problem. Ill try dropping the pressures and see how it helps.
It also has heavy duty shocks and springs which are a little bouncy.
And I'll have a look into the tyres as see how it goes. Might swap to a proper pair of muddies and have all terrains spare.

Originally Posted by Celtoid

When I first got Scorpion ATRs on my D4 I found them a little un-nerving in the wet, specially the front-end when cornering. They felt a little skittish. I was disappointed as I'd read such great reviews about them.

I checked pressures....all 40psi+. Dropped them to placard pressures (33 -36psi) and they are good as gold.

Funnily enough, a mate of mine just got 17" Scorpions fitted to his Triton work ute and he stated that he felt that they were not quite right. I checked his pressures...all 40psi+. His placards state 29psi when unloaded! Thank god he didn't get to drive it in the wet!!!

Will you be shocked to learn that an increase in pressure in the wet gives increased grip/traction ?

Always did this on race cars that ran treaded racing tyres and always worked.

Originally Posted by rick130

Will you be shocked to learn that an increase in pressure in the wet gives increased grip/traction ?

Always did this on race cars that ran treaded racing tyres and always worked.

Yeah I would be. It creates a high spot on the tyre and thus less tread on the ground.

Racing is probably different due to the speeds forcing more tread onto the track.....but I just made that up.....LOL!!!

In real terms....tyre composition, size, shape, suspension set up, etc, etc, etc....is it the same for a registered vehicle?

Oh forgot...increase in pressure...what does that mean? Is the tyre now at the correct pressure (as in before it was too low) or is it now operating above the manufacturer's spec?

Physical evidence for road going vehicles would suggest otherwise.........

I think there is well catalogued wear evidance on all brands, all sizes, etc, that would support my claim too.

Kev.

Regardless of construction, either radial or bias, increasing tyre pressures of around approx 10psi above normal hot operating pressures gives an increase in grip and traction.

Of course it crowns the tyre out slightly, that's why you do it.

It opens up the channels, but more importantly, by increasing the carcass stiffness makes the tread blocks work harder, which generates temp in the rubber and hence gives you greater grip.

Dropping pressures for the wet is exactly the wrong thing to do, (yes, I've done it to see what would happen) but I suspect it's what most people would do, although in reality we all just use what was already in the tyre and keep on driving.

The only reason I brought it up was because you said "Thank god he didn't get to drive it in the wet!!!" and I'm suggesting it would have been fine

I always go higher pressure than lower for the same reasons, better grip and handling. They also tend to wear better. The manufacturer normally looks to ride comfort and typically many trucks have goodies on them that they don't contemplate with the placard pressures- lpg, bullbar, sliders etc.

I run 245/75/16 generals in AT2 light truck so my pressures have to be higher than the stock tyre anyway.

I prefer CDL on high speed dirt, but it will tend to oversteer rather than understeer - just have to drive accordingly.
Cheers

Lower pressures than standard = higher fuel usage, more comfortable ride, greater side wear on hard surfaces and floatation over soft mashy or sandy ground.

Higher pressures than standard = lower fuel usage, harsh ride, greater wear in middle of tread, less side wall damage from stakes and more grip on a greasy surface over a hard clay bottom.

Tyre pressures are not as important when travelling on a hard decomposed Dolerite gravel road, where the surface is like ball bearings on glass.
When you find you are in those conditions, slow down!!! and feather the accelerator and brakes.

Originally Posted by rick130

Regardless of construction, either radial or bias, increasing tyre pressures of around approx 10psi above normal hot operating pressures gives an increase in grip and traction.

Of course it crowns the tyre out slightly, that's why you do it.

It opens up the channels, but more importantly, by increasing the carcass stiffness makes the tread blocks work harder, which generates temp in the rubber and hence gives you greater grip.

Dropping pressures for the wet is exactly the wrong thing to do, (yes, I've done it to see what would happen) but I suspect it's what most people would do, although in reality we all just use what was already in the tyre and keep on driving.

The only reason I brought it up was because you said "Thank god he didn't get to drive it in the wet!!!" and I'm suggesting it would have been fine

Ha! Ya beat me to it... I was just about to say the same.

On gravel, I keep the pressures up. I run narrow tyres which lets the tyre 'bite' through the loose surface. Dropping the pressures might make the ride more comfortable but it would just make the car wallow though the corners and the tyres not as affective.

M