Why Wide Tyres Do Not Help In Desert Driving

[Frederic]

Since joining the club i have seen a plethora of 4x4's in the sand, all performing differently based on the driver skills, how powerful the car was, or how the ground clearance made it easier or more difficult to cross dunes in the UAE.

What many people seem to assume is that wider tyres would improve their footprint in the sand, and would make it easier for them to drive in the dunes or climb hills. Others choose these fat tyres more for the looks than anything else, without knowing how much it affects their performance negatively.

How is this possible ? 

Basically it all comes down to the surface area that any tyre will take up on the sand. A longer footprint will distribute the weight of the 4x4 better so it "floats" better and does not sink in that much.

The surface area is determined by the weight of the 4x4, tyre construction, and tyre pressures, but NOT tyre dimensions. In fact a narrower tyre will deform more during deflation than a fat tyre to achieve the same footprint. 

The second factor is the rigidity of the sidewall. The more rigid the sidewall is, the less it will form a longitudinal footprint. We have seen this very regularly on our drives where a BF Goodrich tyre needs to be deflated below 12psi to get better flotation. This is due to the rigid sidewall, which is a good thing in wadi or mountain driving, but that is a different story.

What does seem to help in favor of desert driving is a larger overall diameter, as it has flatter interface with the sand and lets the sand behave more like a solid. Smaller tyre diameters have a sharper radius and sand may flow out more easily from underneath the tyre.

A good example are the huge rear wheels on tractors and their incredible ability to not get bogged. Tractors have very larger diameter tyres. They do not have wide tyres.

Another important factor is that fatter tyres are much heavier and will take away lots of power from the drive axles, and on top of that will create early wear and tear on the axle and drivetrain.

 

Moral Of The Story ?

Given the above description, it makes sense to stick with the OEM tyre and rim sizes, or when upgrading only go for a slightly larger diameter (not necessarily wider). A larger sidewall will give you better protection from rocks and will minimize popouts.

Personally i have seen lots of Jeep Wranglers performing the best in hill climbs with their 245/75/17 tyres which may look a bit skinny but climb so much more easily in comparison with Jeeps that have the massive bulky tyres. 

 

[Ilya]

Would be great to have a clear experiment. We have a lot of Wranglers, with both stock and and upgraded tires. So we can shoose hill with no bumps (so driver can just drive), soft sand, same starting point, manual gear... Happy to be part of this excersise!

[Rahimdad]

@Ilya Golubinsky thank you for your kind suggestion. This exercise is not something which we can take care off in an hour or a drive. It should be personal responsibility and commitment over several drives in different terrain to know what best suits you and your car.

[Varun Mehndiratta]

Thanks @Frederic exactly the query I was about to ask, mainly as I noted the requirement of high profile tyres for upgrade to Intermediate.

I drive a Wrangler Sahara 2020 model with stock 18 inch rim and stock all terrain tyres. I have been happy with performance, especially once it's down to 12-13psi. Plus gives a smooth on road drive  So wasn't too happy with thought that might have to change, as didn't understood the expectation well. 

Your post clarifies it for me. Thanks for the same ..

[Ilya]

1 hour ago, Rahimdad said:

@Ilya Golubinsky thank you for your kind suggestion. This exercise is not something which we can take care off in an hour or a drive. It should be personal responsibility and commitment over several drives in different terrain to know what best suits you and your car.

As physics/theory of the phenomenon was described, the most correct and reliable way of the experiment would be exactly a set of short "laboratory" experiments, to eliminate the impact of driver's skills, etc. 

On the other side, conducting a real scientific experiment will not be easy, as usually with widens you also get a bigger overall diameter. So we actually don't know what factor's impact is growing faster, and in practice, we can only do a comparison between standard and large (wight + diameter) wheels. 

It seems to me that at least Wranglers perform better on upgraded 33", rather than on stock. On 35" without regearing you losing power significantly (I feel it very clear), so by default 33 can be better than 35, easily. But after regearing - not sure. 

[Rahimdad]

@Ilya Golubinsky I'm not a big fan of re-gearing. I have seen Jeeps with 31s doing the trick, so why you want heavier tires with 33s or 35s. 35s are the worst, only good looks and maybe more apt to off-roading in mountains and rocks. But on sand 31s can do the trick. Your vehicle might be the best in the world with the ultimate setup, but its your drive capabilities and style which will help you to learn and grow. This comes with experience, which comes with regular drives to improve on what you've learned and picking up some new tips and tricks. After driving off-road in the sands for over 12 years only thing I can confirm is that I too am learning along with everyone else.

[Ilya]

@Rahimdad, I am not questioning the importance of skills (skills are much much more important than anything else), I believe this is why many of us here, to learn
What I am saying is, that with equal skills in the equal conditions 35'' might be better than the stock ones for Wranglers. Because there are arguments supporting this and not, I proposed doing a test  

Also, big tires don't come alone,  you normally do new suspension, shocks, etc.. so you can drive faster on bumpy areas, so you can get more momentum for the place you need it.. but this is one more time about driving technics and skills. I think the original topic was more about traction and adherence itself

[Rahimdad]

@Ilya Golubinsky you're right. I understand you. I'm not much into mods, as more you dwell into mods, more components, more chances of failure. 35s as I said are good for off-roading in mountains and rocks. Sure you can try them out in sand. But as you mentioned it would need some mods to support the 35s. Plus heavier tires do take a toll on your engine and transmission. I had a friend once who had a TJ which gave him 400 KMS on a full tank. Once he molded his car to support 35s and put them on his fuel economy went down by about 50%, he used to get only 250 KMS on a full tank. He was always complaining about some issue or the other with the 35s. Once he even flipped his TJ on a roundabout with the 35s. My experience after watching my friend suffer is enough to teach me a lesson.

Let me know how it works out for you. I've never seen someone make a difference for the better with 33s or 35s.

[Varun Mehndiratta]

9 hours ago, Rahimdad said:

@Ilya Golubinsky you're right. I understand you. I'm not much into mods, as more you dwell into mods, more components, more chances of failure. 35s as I said are good for off-roading in mountains and rocks. Sure you can try them out in sand. But as you mentioned it would need some mods to support the 35s. Plus heavier tires do take a toll on your engine and transmission. I had a friend once who had a TJ which gave him 400 KMS on a full tank. Once he molded his car to support 35s and put them on his fuel economy went down by about 50%, he used to get only 250 KMS on a full tank. He was always complaining about some issue or the other with the 35s. Once he even flipped his TJ on a roundabout with the 35s. My experience after watching my friend suffer is enough to teach me a lesson.

Let me know how it works out for you. I've never seen someone make a difference for the better with 33s or 35s.

This has been confirmed repeatedly by Jeep enthusiasts, including the guy who runs Jeepers 🙂.  .Jeep is already prone to Roll overs and lifts required to accommodate heavier tyres surely affect the performance in terms of steering response/mileage as.well as enhances the risk of roll/trip overs...

Before buying my wrangler, I asked a friend working at Mopar in US and he advised against going for lifts etc unless really going for mountain/rocky trails etc. Sahara comments with 32 inch tyrea and can accommodate 33, without lift, I don't think this additional 1 inch (further in any case reduced post deflating) is going to make a diff in drive on sand. 

[M.Seidam]

Certain vehicles ( examples : Jeep Wrangler , hammer , Nissan Xterra , G wagon ... etc ) were produced in the first place for military purposes in their  stock form. However when they were shifted to the public the stock form has been modified slightly to accommodate the civilian needs in terms of appearance and compactness . However the core remains the same like engine and drivetrain chain. That’s why we see these vehicles perform excellent in their stock forms even to the extremes of the different environment with minimal needed no major modifications ( example : bash plates , kill switch’s , tyre size to certain extent ) , ( major modification. In my opinion is a modification that entails replacement or compensating an entire system e.g : huge tyres needs lift more than 2.5 in goes with that spacers then re gearing . Possibly the entire steering system and later ... etc ) ...  for all these reasons and also reasons that I am using my vehicle on the road , I believe that the majorly modified vehicles should be reserved for very specific controlled recreational event in specific area and driven by specifically trained ppl.
I think our common offroad vehicles in their major stock forms can perform reasonably with no major issues. 

Edited February 10, 2021 by Mohamed Seidam