[corneliu]

Hi all, I am a rookie to off-roading and got into a bit of a sticky situation today.

I had decided to go driving along a beach and had aired down my tyres to 20 PSI in the morning around 8 am. However, when I actually headed out into the beach sand at 11 am it was extremely hot and my tyre pressure went up to 25+psi while driving (I got to know this only later when I decided to deflate them some more).

I had parked my car in a stretch of soft sand (I didn't realize it was soft while parking), and when I got back to drive out I found 4H was only digging me in further. So I switched to 4L and began to rock back & forth to get some traction going out, but I found that when the revs exceeded 3k the car started shuddering quite violently. I think my front tyres might also have been turned at that time as I was trying to turn my way out. As soon as this happened, I got my foot off the throttle. Eventually, I did get the car out, but I was curious to know the reason for this shuddering.

Some of the tyre tracks seem to indicate it might be something called wheel hop which involves traction being repeatedly gained and lost and is possible for high pressure tyres in sand. Is my assessment correct? If so what causes this in a sand environment and how can it be avoided? Also I believe wheel hopping can be catastrophic for the transmission, and although the car is running fine, are there any checks I need to do? Any advice is much appreciated, thanks!

Pictures attached below for reference:

[ashivas89]

Quick question, what type of car were you driving? If it was a car with a live axle, then it was very likely axle tramp. If so, a one off occurrence should not wreck the transmission in principle.

Was it something like this ? :

https://www.youtube.com/watch?v=ViyL...l=TheGrandTour

[corneliu]

Originally Posted by ashivas89

Quick question, what type of car were you driving?

I was driving a Toyota Hilux with IFS in front and a live axle in the rear.

Was it something like this ?

Not exactly, I think in this video the front wheels are jumping together, whereas in my case they were jumping alternately, so it was giving a kind of a rapidly alternating left/right jump & shudder.

[shankar.balan]

This is one reason why its useful to have one more pal with you in a 4WD for recovery purposes if need be. The other thing you would be well advised to buy or else get fabricated and carry with you is a pair of sand ladders.

[HappyWheels]

Originally Posted by corneliu

...
I had parked my car in a stretch of soft sand (I didn't realize it was soft while parking), and when I got back to drive out I found 4H was only digging me in further. So I switched to 4L and began to rock back & forth to get some traction going out, but I found that when the revs exceeded 3k the car started shuddering quite violently. I think my front tyres might also have been turned at that time as I was trying to turn my way out. As soon as this happened I got my foot off the throttle. Eventually, I did get the car out, but I was curious to know the reason for this shuddering...

From the image, the sand does not look very soft, so 20 PSI should not have been an issue, unless you had a fully loaded vehicle that weighed it down.

A video of the "hopping" would have helped, but without it, not attempting a response.

Next time, go down to anywhere between 13 to 15 psi. Just don't try to do donuts at this pressure.

[corneliu]

Originally Posted by shankar.balan

This is one reason why its useful to have one more pal with you in a 4WD for recovery purposes if need be. The other thing you would be well advised to buy or else get fabricated and carry with you is a pair of sand ladders.

Lesson learned. The very next mods happening to the car are roof rack + sand ladders + shovel, and this will have to happen asap.

Originally Posted by HappyWheels

A video of the "hopping" would have helped, but without it, not attempting a response.

Just managed to extract the video from my dashcam. Here it is:

https://www.youtube.com/watch?v=hcJZ2E3qNWc

Next time, go down to anywhere between 13 to 15 psi.

Yup, later in the day I went down to 16psi and the car took that exact same stretch without any issues.

Just don't try to do donuts at this pressure.

I intensely dislike doing donuts and watching them being done, especially in peaceful and untouched places, so I don't think this should be an issue.

Originally Posted by anjan_c2007

But please check the legality about venturing for a drive on Goa's Beach sands. To my knowledge many beaches in Goa going by current laws are out of bounds for vehicle use thereupon.

Thanks, yes I am aware of this. This was not in Goa though; it was at a beach where I double checked the legality of taking the vechicle in before going, as the access to our resort was via the beach itself.

[HappyWheels]

Originally Posted by corneliu

...Just managed to extract the video from my dashcam. Here it is:

https://www.Youtube.com/watch?v=hcJZ2E3qNWc
...

Your analysis was right; tires getting grip and losing it (due to the "hard" patch breaking off). Right call to reverse and try again instead of pushing it further. You "could" have gotten through if you had worked the steering - which is continuously turning the steering to 3 o'clock and then to 9 o'clock, whilst giving constant slow power to the wheels so that they spin but do not over-spin and throw sand and dig in, till the vehicle drives out of the bogged part. Try this the next time; you can also do this when you feel you are getting bogged down, provided the speed is within control.

Originally Posted by corneliu

... Yup, later in the day I went down to 16psi and the car took that exact same stretch without any issues...

Driving in sand is mostly about PSI and momentum. Get these right and you are good.

Originally Posted by corneliu

...I intensely dislike doing donuts and watching them being done, especially in peaceful and untouched places, so I don't think this should be an issue. ...

Same opinion about donuts!

Happy exploring!

[dhanushs]

Originally Posted by corneliu

...but I found that when the revs exceeded 3k the car started shuddering quite violently.

Looks like you were experiencing wheel hop. How old is your car?

I might be wrong, but this might be the phenomenon that happened. You dont have traction, you slip - slip makes tyres dig in and slightly increasing the tractive contact patch. This gives enough traction to move. But when you move you again have a patch with no traction, you slip, slip makes tyres dig in, increasing the tractive contact patch. This keep happening and resulting in wheel hop which you've experienced.

Originally Posted by corneliu

Not exactly, I think in this video the front wheels are jumping together, whereas in my case they were jumping alternately, so it was giving a kind of a rapidly alternating left/right jump & shudder.

You have an Independent front suspension, hence.

I found 4H was only digging me in further.

Ideally 4H shouldn't dig you in. Looks like you were applying too much acc pedal.

In sands with very low traction you need to be patient. Start moving slow and slowly build up momentum. 4L helped you cos it was slower. But, if you could replicate the same speed in 4H you would've gotten out quickly.

[corneliu]

Originally Posted by HappyWheels

Your analysis was right; tires getting grip and losing it (due to the "hard" patch breaking off).

Right so this does look like a case of wheel hop.

You "could" have gotten through if you had worked the steering - which is continuously turning the steering to 3 o'clock and then to 9 o'clock, whilst giving constant slow power to the wheels so that they spin but do not over-spin and throw sand and dig in, till the vehicle drives out of the bogged part. Try this the next time; you can also do this when you feel you are getting bogged down, provided the speed is within control.

Definitely, will keep this in mind for the next time. Thanks a lot for the advice!

Same opinion about donuts! Happy exploring!

Cheers!

Originally Posted by dhanushs

Looks like you were experiencing wheel hop. How old is your car?

I might be wrong, but this might be the phenomenon that happened. You dont have traction, you slip - slip makes tyres dig in and slightly increasing the tractive contact patch. This gives enough traction to move. But when you move you again have a patch with no traction, you slip, slip makes tyres dig in, increasing the tractive contact patch. This keep happening and resulting in wheel hop which you've experienced.

Right, so @HappyWheels and your analysis is pretty much the same and it looks like its a confirmed case of wheel hop. The car is less than a year old. Is there something I need to be concerned about, or get checked asap? From what I read on some other forums wheel hop can totally wreck the suspension.

You have an Independent front suspension, hence.

Ah right, this totally explains it!

Ideally 4H shouldn't dig you in. Looks like you were applying too much acc pedal.

You're absolutely right, on hindsight I do feel I was too agressive on the throttle in 4H, which is what got me into this situation in the first place. Also yes, the sand wasn't loose enough to warrant 4L, because 4H was feeling pretty comfortable & less strained from the get-go.

In sands with very low traction you need to be patient. Start moving slow and slowly build up momentum. 4L helped you cos it was slower. But, if you could replicate the same speed in 4H you would've gotten out quickly.

Excellent advice thanks & noted. Will keep this in mind for the next time.

[Geo_Ipe]

Originally Posted by corneliu

...I found that when the revs exceeded 3k the car started shuddering quite violently. I think my front tyres might also have been turned at that time as I was trying to turn my way out...

Could you please tell us which vehicle you were driving?

One doesn't need to rev up to 3000 rpm in 4L to get out of soft sand. Maybe you should have tried in a higher gear - maybe 2nd or even 3rd (assuming you were in 1st gear) with lower revs.

It's always a good idea to have someone else to spot or see which tyres have traction while off roading. Just my 2 cents!

[corneliu]

Originally Posted by Geo_Ipe

Could you please tell us which vehicle you were driving?

One doesn't need to rev up to 3000 rpm in 4L to get out of soft sand. Maybe you should have tried in a higher gear - maybe 2nd or even 3rd (assuming you were in 1st gear) with lower revs.

It's always a good idea to have someone else to spot or see which tyres have traction while off roading. Just my 2 cents!

I was driving a Toyota Hilux.

I did try to keep the revs low, but the car was on automatic gear selection, so I'm guessing the car defaulted to 1st gear initially and hence the throttle input momentarily brought the revs to above 3k, which triggered the wheel hop. Will keep your advice in mind for the next time.

Unfortunately, on this trip I was all by myself and had no one to spot for me. In this case though, our resort was nearby so help was not too far away.

Another big lesson learned is to study the tide timings before venturing out onto beach sand. In this case, I had rather naively gone out around 12pm with the high tide expected to be incoming by 1pm. Even though I was in a spot that would technically be safe from the high tide, there was always that 10% chance that a rough high tide might spill over, and the thought of this risk got me really jittery.

[1.2TSI7DSG]

Originally Posted by corneliu

Hi all, I am a rookie to off-roading and got into a bit of a sticky situation today.

I had decided to go driving along a beach, and had aired down my tyres to 20 PSI in the morning around 8 am. However, when I actually headed out into the beach sand at 11 am it was extremely hot and my tyre pressure went up to 25
+psi while driving (I got to know this only later when I decided to deflate them some more).

I had parked my car in a stretch of soft sand (I didn't realize it was soft while parking), and when I got back to drive out I found 4H was only digging me in further. So I switched to 4L and began to rock back & forth to get some traction going out, but I found that when the revs exceeded 3k the car started shuddering quite violently. I think my front tyres might also have been turned at that time as I was trying to turn my way out. As soon as this happened I got my foot off the throttle. Eventually, I did get the car out, but I was curious to know the reason for this shuddering.

Some of the tyre tracks seem to indicate it might be something called wheel hop which involves traction being repeatedly gained and lost and is possible for high pressure tyres in sand. Is my assessment correct? If so what causes this in a sand environment and how can it be avoided? Also I believe wheel hopping can be catastrophic for the transmission, and although the car is running fine, are there any checks I need to do? Any advice is much appreciated, thanks!

Which Car?

I think it would be slip differentials (LSD/MLD/BSD) engaging

[DirtyDan]

Originally Posted by 1.2TSI7DSG

I think it would be slip differentials (LSD/MLD/BSD) engaging

You will get the same phenomenon from a vehicle with locking differentials (such as the Gurkha) so I doubt it has anything to do with limited slip diff. I think Danushs and Corneliu have pretty much got the proximal cause diagnosed, above.

[tsk1979]

This is hopping. It happens with any vehicle. More to do with power delivery + suspension geometry etc., On sand it happens when you have overinflated tires. So your tire is getting grip and losing it immediately. It can also be seen on dragsters.

Lower to 10-12PSI in sand and give low throttle inputs and you would be out.

[Cresterk]

It is from the locked differentials and your steering being turnt. 4low locks both front and rear wheels to turn at the same speed and while turning, the wheels want to spin at different speeds. The sand does not look soft enough for the wheels to spin freely. The shuddering is also pretty mild compared to axle tramp or wheel hop.