Making Massive Downforce like an F1 Fan Car with Ground Effect

[@domenicogallo8312]

Gordon Murray is definitely alive. He founded his personal car factory and is about to launch the first road supercar equipped with a downforce fan

[@XenonG]

Mmmhmmm, the successor to the McLaren F1.

[@LogicalQ]

Gordon is still alive, Colin Chapman is not.

[@stevencraigie2430]

The t50 is the best sounding production car for years!

[@LogicalQ]

@@stevencraigie2430 cosworth doesn’t typically disappoint.

[@sepg5084]

Which would be irrelevant to most car enthusiasts around the world, he's just building cars for rich people who can't even change their own oil.

[@3d_aeroworks]

If you are looking for an increased pressure drop for less weight and power, have a look at a turbine style design. Edf's are good for moving large volumes of air but struggle with pressure changes. You did get some great results there however. The turbine style design is much more efficient at generating a pressure differential then moving large volumes. The edf's were likely stalling the blades and requiring 4s to maintain the low pressure required. I'd expect you could achieve the same result with 1 turbine on 3s. Keep up the great work!

[@waxball888]

This guy blows.... haha

[@fokjohnpainkiller]

He should at least put the fans in a series smh

[@derp6632]

but this application is high pressure ratio but low airflow with the underside of the vehicle being "dead headed".

[@frostyab7579]

what do you mean by turbine?

[@3d_aeroworks]

@@frostyab7579 what he has used is a ducted fan. A turbine would be more like a turbo charger style impeller.. designed more around increasing pressure rather than moving volumes of air. The ducted fans suck at creating large pressure differentials.. heh heh.. see what I did there ;)

[@sipbit]

Great Video, FYI EDFs are great at creating momentum and high velocities, not so much a pressure drop. Using something like a turbocharger (centrifugal fan) and create press drops 10-100x that of an EDF

[@EngineeringAfterHours]

The intent behind this video was actually to see how much of a pressure drop I can get with an EDF and it was a few times greater than need. I had read the pressure drop was very limited but no one had concrete values, so I was happy to see an EDF give me more than I need. Using a centrifugal fan will drop my flow rate substantially which makes the design way too sensitive to leaks and leak rate. So passing a crack with a centrifugal fan will have a bigger impact than passing a crack with my EDF. I also don't want a higher pressure drop as it's already high enough.

[@DeRock401]

GRP tires have an immense amount of grip when they heat up. They are so sticky they will stick to most surfaces. But good stuff man. I am having problems keeping my infraction on the ground when I attempt to give it full throttle l, it wants to take off like an airplane

[@derektran9404]

Seeing the amount of printed stuff you do, I really recommend Fusion Filaments HTPLA+ or 3dFuel Pro PLA, as they print like PLA but are far stronger.

[@KayJblue]

Gordon Murray is currently working on the T.50 proto which uses fans on a production road car.

[@TheTsunamijuan]

I think you should revisit this, I suggest using some UHMW tape as the skirt/interface between the surface and manifold. Which would also slide/wear away smoothly. Second I would suggest splitting the plenum underneath into multiple separate compartments connected via a manifold with some sort of either valving or treat it like vacuum tables. So that they again distribute the vacuum around better.

[@EngineeringAfterHours]

Thanks for the feedback, I'm definitely revisiting this with a car intended for a very low 0-60.

[@zqzj]

@@EngineeringAfterHours I believe they used bristles in the F1 fan cars. I was looking into doing an almost identical RC project, and my plan was to go with bristles as well.

[@martinmckowen1588]

Doing my head in watching you do calculations using imperial units.

[@STOLerant]

Thank you! I have been waiting for this to come up in the RC world.

[@loukiankostovic9022]

To increase the grip of rubber tires, apply WD40 on it, it destructures the rubber and makes it softer. Ajust the duration of exposure of the tire with the WD because too long can tear the tires.

[@logicalness]

This is such an amazing video! Wonderfully done.

[@EngineeringAfterHours]

Thank you!

[@niravdhruve8349]

This project looks awesome, I am in the process of developing my own RC car with similar systems controlled by a Arduino nano ble sense, hopefully can use the sensors on the chip to actively control systems. Maybe I should consider edfs😅 but might be a bit out of budget to be honest. Thanks for the inspiration and good luck for the lateral car👍🏾

[@EngineeringAfterHours]

Thanks! I've toyed with the idea of a speed run car and small active aerodynamics surfaces to stay on course was one of the things I dreamed of doing. I'm sure an arduino would work great for that.

[@tobichessell132]

Hi. This is awsome but i have one question... why the hell did you mount the EDFs the wrong way round???? You could have made a lot more suction by using them the right way round and therefore could have used hard or very stiff skirts wit less friction or with a tiny gap to the ground

[@EngineeringAfterHours]

How much does the pressure drop change based on orientation?

[@EngineeringAfterHours]

@@tobichessell132 hah...my main point is that we actually don't know if fan orientation makes a meaningful impact on pressure drop. I think I mention it in the video, but I have more downforce than I need and purposefully put the fans in that orientation for appearance. I will definitely be testing this in my 3rd round though and that should answer it finally. Greetings from Texas and thanks for the comment!

[@CKILBY-zu7fq]

Congratulations, I was going to mention a spring loaded. Vertical action. Type of seal. But as far as I'm concerned, you just made the genius book of records. First car to drive inverted, Make shure you submit that. Great display of your purpose. Thanks, it was a great video. 👍👍👍👍👍

[@aschethor3139]

Great video! Maybe, you could try out multiple "rings" of skirts under the car and increase the pressure difference in every skirt-ring. I believe this could help to further increase downforce. Maybe, this even allows you to keep a little gap between your skirts and the road so you don't destroy them in every run and further reduce friction with the ground...

[@bighaverlegend33]

The car looks absolutely sick

[@RickyImpey]

Great video, looking forward to seeing where you go with this.

[@peterzingler6221]

If you would mount the edfs the right way they would work much better.. The housing the blades all is designed to take in air from the front and not the back which is what you're doing atm

[@AdjustinThings]

Can you do a double skirt? One just inside the other. The inner one would be mostly solid and the outer one more flexible. What about changing the orientation of the fans to blow exhaust away from the surface?

[@EngineeringAfterHours]

I tested a few double skirt arrangements with mixed results. It may be worth another look. By changing orientation do you mean have the fans pushing the car down? When these fans are being used for a pressure drop, they create almost no thrust.

[@Kackspack0815]

Would like to see some grip comparisons on a normal track (with and without running fans).

[@Kurosaka]

Yh or like on of those professional rc tracks that are completely flat and clean for better results

[@derp6632]

I wonder how difficult it would be to have the load path go straight through the hub or unspring control arm. This way your pressure depression down force would act directly on the hub and tire and you wouldn't have to deal with compromising spring rates to compensate for the downforce.

[@georgestratford8029]

In regards to tyres it depends on the surface, roads can use sticky slicks tyres but wouldn't work on dirt, also the softer more grip but higher friction, harder compound less grip but less friction there's most likely a sweet spot for R/C tyres.

[@theundead1600]

Just miles from me is RA road racing circuit, they sometimes still have the chaparrals show up for vintage races. So awesome.

[@CuervoRC]

I think the fan propellers are working backwards. I don't even know how you got them to produce any power.

[@MixZTitaniumDubstep]

I'd like to know where I can get those smaller springs that you put on the shock shafts. I'm looking for them to use in my E-Revo to try to reduce shock sagging.

[@ZetecinsideMotorsport]

Thankyou for posting such a useful video. I have a Formula Ford with wings and I've been searching for a flexible side skirt/diffuser solution for a long time. I'll get some 3d printed and see how I get on 👏

[@SybrenR]

I highly suggest you flip around the EDF blades on the EDF shaft (this won't change the airflow direction). The hollow side of the EDF blade is now facing the low pressure side and the rond side is facing the high pressure side (the outlet). By installing the fanblades the right way around you will get even more power (vacuum) for even less Amp draw. This mistake is commonly made with RC plane propellers. Look for the video of FliteTest title: FliteTest - Prop Direction- FAST TIP In this example they explain it for a propeller but the same rules apply for a EDF fan. Cool project by the way.

[@rb3020]

Could you direct the exhaust/fans at a 45 degree angle up? More down force and less debree????

[@EngineeringAfterHours]

Oddly enough, the debris path is like a hemisphere as it goes back and radially outward. The second fan car I made did this and I cracked a gopro lens lol

[@Reecefpv]

You need foam tires to lower the weight alot compared to the hoons. And get some bec to eliminate the extra lipos or maybe a splitter to run off the balance lead of the main motor lipos. Another thought is to use a side skirt that can inflated from some of the waste air redirected into tube like skirts that expands to make a seal, kinda like actual hovercrafts do and you could adjust to pressure against the ground. Possiblity lol. Just some thoughts. But either way this is awesome and your definitely on to something.

[@alexpeacock3870]

Gordon Murray has just completed his new car ...... it's actually a fan car for road purpose.... maybe you know about this but as you seemed unsure on whether he is still alive I'm thinking maybe not.... anyway check out his new car its amazing.

[@earlstenson3037]

Question why not Angel the Exhaust side of the fans up at a Backwards Angle and Make it 4. One at each corner respectively or a 3 configuration?

[@ConsultingjoeOnline]

You should add a ramp for one side to do a half barrel roll to transfer from upside down to ground

[@Strav24]

Not sure if this would create too much complication or pressure drop, but what if the skirt is made out of an inflated tube, potentially siphoning some of the air from the fans. It around in theory be able to inflate and deflate depending on how much air you're pulling through

[@piereligio_ds]

Holy s***, it's years that I was wondering if i could create something like this! Watched the whole video now. Amazing, just amazing. My idea was just to increase grip at all speeds, and see how much it would be better with the system on compared to it turned off. I think there are no other vacuum RCs and I wished I was the first to do that, but well, congratulations! Ahah

[@ИгорьИгорев-е5й]

A good vacuum cleaner turned out!

[@corpsecoder_nw6746]

Wonder if floor designs where vortices are generated along the sides of the floor, starting in front of the floor, would work in maintaining some sort of floor sealing consistently. The way F1 does it these days. Also wondering about the math of the load necessary vs area vs fan suction

[@Shadow0fd3ath24]

Another thing you may have over looked is....they also had just as much aero as every other car PLUS these fans, AND a ton of air diffusers under the car, and that vacuum under the car helps the traditional diffusers work EVEN BETTER also

[@bibhabbag1]

Dang! Will eagerly follow this series. And want to see how good a race rc car this could be made into.

[@billlannister7965]

Can you use a bristles for the side skirts? Like the business end of a broom?

[@scottborst5430]

That’s cool have you ever seen the STP jet car it was a Formula One jet racing car instead of having the fans blowing straight out I think it was a 35 or 45° angle push down on the car more check it out

[@Chris-cv1ll]

Why didn’t you take a look at skirt designs for hover craft? They may do the opposite (high not low pressure) but they have to keep the pressure under them just as you are trying.

[@zaccarrollart3493]

This is incredible!! I dream about doing this to an rc drag car.

[@AdamOpheim]

Why not point the EDF exhaust up in stead of back? would provide more down force and not throw as much dirt directly behind it?

[@aus-reviews8462]

I think it would really cool if you could add a vacuum sensor to tell you when downforce is lost

[@Cloxxki]

Excellent work! What about an unspung aero car? Soft springs working for a high downforce car. Just make the second floor as light as possible.

[@bobbielinder8551]

Is it possible to turn your fans around to face forward and then turn the blades around Square as you're going to ground force is sucked in and push back out the back and as you go increase downforce

[@naelrc4583]

Really cool project my friend! Awesome! Really impressed how u manage to move your rc while sticking to the board. Will you do a project wall climbing rc using this downforce fan? maybe a building inspection rc?😁👍🏼

[@nljf1042]

you need traction compound to make the tyres have more grip and you should consider putting in like a 3 speed gearbox from a nitro car in there

[@EngineeringAfterHours]

Do you have any traction compound recommendations? I've never really played with the stuff.

[@nljf1042]

@@EngineeringAfterHours not really they all work similar , most have a light, medium and heavy i would suggest you get a pack with all three so you can try and see which is best for this car

[@HinduGangsta]

this is fantastic

[@doorlagr]

Larger diameter tires yield larger longitudinal patch...larger area perpendicular to acceleration forces means better straight line/off the line performance. A certain performance car's engineers noted an increase in drive tire diameter resulted in significantly increased results over just increasing width. In fact, I believe it was stated the car performed better off the line with something like 21 inch 245s vs 20 inch 315 or 335 or 395 or some ridiculously wide tire. It makes sense when thinking about the direction of the force compared to the contact patch and the friction needed to launch the vehicle...it's kind of like having a 2"x4" piece of wood laying flat on the 4" dimensioned side and using that to walk across a gap, then switching to a 2"x8" piece. There will be some strength gained with the increased width but if they switched to a 4x4 there would be an incredible performance difference. This is also helps to explain why lowering tire pressure increases accelerative performance, amongst a few other factors. I can't remember if you said the ultimate goal was just insane 0-60/straight line performance or all around high acceleration performance....something like being able to sustain 5g consistently through a corner. If it's the former, and rules are ...well flexible...have you considered using/creating something that equates to having a ton of weight on the vehicle(specifically over the drive axle since you said RWD) and immediately after initial acceleration occurs, which requires the highest level of friction, release the weight from the car so it doesn't negatively effect drive train and aerodynamic efficiencies. Please don't ask what something like that would look like or how it would work because I have no idea, I just know it sounds really cool from a performance standpoint to be able to have a ton of weight being applied to the drive tires right at take off .....and then imagine programming a mini ECU or something so it can drop the weight based on real time calculations performed up to 1000 times a second. The calculations happening every milisec would determine the optimal weight needed to achieve enough friction to keep the tires from breaking loose, so as the car accelerates and momentum continually increases, the weight needed to maintain straight line grip will reduce at a rapid rate and the vehicle will drop its PEMs(performance enhancing mass) faster than someone that's on a keto diet through nutrisystem that has richard Simmons as their personal trainer, just signed up for Jenny Craig, and not only owns a thigh master but also the highly coveted shake weight(we're talking serious weight loss and very quickly(talking about the car(not being a smartass)I lost track of how many open parentheses I created)hopefully this is the last one). Good luck on your future build and thank you for the interesting content

[@BrokenLifeCycle]

You could also take the fan exhaust and blow it across any aero surfaces to generate even more downforce like a blown diffuser.

[@no_name2882]

I wonder if you could make the fans face upwards to stop the debris from shooting everywhere. It might even make some form of downforce

[@jesse2916]

The Hot Racing aluminum 2wd traxxas trans housing is great.

[@jonh1209]

Would an upright exhaust give it more downforce over the rear axle?

[@aportabales]

As the volume is not that much once the vacuum is created why not to set the EDFs inline/series instead of side-by-side/parallel?

[@Jrod_FPV]

Could Test effectiveness by doing lap times on a basic circle track. Seems like if you exhaust out the top you could possibly gain some more down force?

[@sergiv92]

and if you put the fan outlets in a vertical direction, it would make more down force

[@bruder211]

Can i get an explanation?

[@ninehundreddollarluxuryyac5958]

Generally you improve the grip of tires by making them out of softer rubber. You can even mold your own using real soft rubber like fishing worms. This shortens the wear life of the tire but makes them real grippy. Making the tires wider to whatever extent possible adds more contact area. Pneumatic tires can run lower pressure which also increases contact area. Too little pressure can cause a tire to get too hot or roll off the rim. In the case of tires made of really soft rubber, it would be interesting to check the difference between slicks (no grooved tread) versus real deep tread. The idea is that deeply cut tread patterns will let the protruding lugs of rubber flex a bit while keeping the top of the lug in firm contact with the pavement.

[@MixZTitaniumDubstep]

You just made the hobby-grade equivalent to the Air Hogs Zero Gravity.

[@Cloxxki]

For lateral G's you could have the fans' exhaust hit some lateral aerofoil. Ideally one that deforms hydraulically, to switch between "skinny", "left" and "right". Voila, low speed lateral G's that don't load the tires. I want these dynamic aerofoils for high speed applications as well. Just SAIL around turn in stead of smoking up tires. Best thing: it would load up the inside wheels that would normally be unweighted. So you can derive mechanical grip from them and ride flatter.

[@Cloxxki]

You could also make a simply 3-way duct valve. As you steer, the fanned air is sent through one of 3 exhausts: up (downforce), left or right.

[@DannyGiusa]

The Algorithm brought me here, I'm not disappointed. Amazing work!

[@EngineeringAfterHours]

Thanks!

[@Pro_Vs_Con]

6:12 It wasn't creating too much friction. The tires was not in contact with the surface!

[@MrTimbestevens]

Hey man you did an awesome job I have an idea that might work for you have the bottom like air hockey the holes all in the to distribute maybe two more fans in front of the two fans to make it for fans

[@NORMIES_GET_OUT]

They make silicone wheels for those Japanese sumo robots that have insane amounts of grip. I'm curious if they make any similar tire compounds for rc cars.

[@EngineeringAfterHours]

I've considered molding my own...just not sure which project to apply it to.

[@martinhadraba5579]

Wasn't it be better if the edfs were facing upwards than backwards?

[@sl592]

Flaps on the inlets to vary the amount of air, and speed controlled. Damn edibles

[@rocketspeedracingleague2404]

This would be really cool for any open RC Class to see how much better it really is

[@cryobytedoesstuff2302]

Question, where’d he get the frame for the car?

[@roadanddirt3105]

Would love to see the fan cars ability to corner at speed vs a traditionally shaped rc car.

[@EngineeringAfterHours]

Fully agreed. The good news is I'm actively building and filming round 2. I bit the bullet and went with a 4wd chassis on this one...it should be a neat look with the new placement of the fans.

[@lukassonntag3956]

A tire with thicker sidewalls will increase grip (because of a larger contact patch ) as down force increases but this will obviously also increase wear and friction

[@ajrivera743]

I was just thinking about something like this the other day! Great work, you got my sub!

[@Man13471]

Cool design … why not connecting the signal of the fan ESC parallel to car ESC’a? In this case the fans power goes up proportionally with the speed of the car which looks more efficient.

[@scottmilano2940]

Why not use ducted fans pointing straight up, one at each corner? That way the exhausted air would contribute to the downforce. It could end up being an upside down quad copter on the car. Doing that you may even be able to eliminate the skirt. Certainly also consider varying the amount of downforce based on how much steering input is used. And if it’s needed for holding the drive wheels down when accelerating, you could vary based on throttle as well.

[@voodoochile7581]

This guy don’t upload enough for me to subscribe

[@EngineeringAfterHours]

Trust me....I wish I could upload more. These projects take a long time because I have to custom design parts, fabricate them, film everything and then edit it. It takes anywhere from 40-100 hours for some of the bigger projects so I can't pump out videos like the review channels can. I also work full time so 1 a month is about as good as I can do.

[@jaysonwallker1648]

All right here's a thought for you, how about if you reverse the fans to where they blow down to take the load off the springs and the wheels and, in effect, make the car lighter? Wouldn't that increase the top speed and possibly the efficiency? I'm an old engineering tech from Rockwell international..

[@bluestonebest1893]

make an hovercraft kind of skirt. it pumps air inside to reduce friction and vaccum in the center to keep the downforce. this way you get an air-suspension for you car with air friction

[@flames4724]

can you post ure 3d/cad models of what you made very curious

[@jaysonwallker1648]

This reminds me of the car that they had in MIB. You can run it upside down sideways right side up, however you want to.

[@SalihArtAndTech]

Wow, great work 👍👍👍

[@sined726]

Use the steering input to control the fan speeds then you don't loose speed in a straight line.

[@TwitchFast]

Absolutely look at GRP tyres, they're hilariously tacky once you get a little heat into them. I've had my car stick to tables after a night of ~110mph passes.

[@EngineeringAfterHours]

Do you have a recommendation for some 1/8th scale GRPs? I definitely want to give them a shot

[@TwitchFast]

@@EngineeringAfterHours Personally I use S01 Revo S5's, the S# refers to the rubber compound on that set of tyres. The lower the number, the softer the rubber and consequently the less heat required to make the tyres tacky. The compound number ranges from 1-7 and naturally soft is great of you're looking for grip, however you will inevitably wear them out faster, I find 5 to be a great balance between grip and durability for my RC. Best of luck!

[@RobertNES816]

You need foam tires that's what the speed run guys use. They're harder and have better grip. Also switch to a brushless system and lipo batteries. The Titan you have will be lucky to hit 25mph with the added friction of the skirt hitting the ground and the added weight. HobbyWing and Castle make really good brushless systems. Something like a 3000kv 3070 sized motor with a 120amp ESC running 4S would be good. Not sure what speed you're shooting for though.

[@Aa-ron01]

Airhogs zero gravity did these before and yes you could drive up walls. They had a humvee version aswell as far as I can remember.

[@bensondowler1053]

Brushes from window secondary glazing for the skirts, good experience though 🤠

[@2bidfilmsguy]

You should have the fans point upwards for even more down force that isn't dependent on air moving over or under the car

[@charlesyoung8600]

Should of said this before, try tire sauce and possibly tire warmers. They will help out a lot by making the tires more plyable. any rc store like a main should have some.

[@EngineeringAfterHours]

Thanks for the tip! I picked up a few tire "sauces" ill be testing. Still working through the warming situation.

[@tannerprice2875]

8:26 Love the shoes, Go Pokes! I go to OSU and work on aero for our Formula SAE team. We can't run a fan car of course, but we're doing something similar with a skirted diffuser!

[@EngineeringAfterHours]

Haha...great observation on the shoes. Good luck with FSAE. My undergrad was at UTA, and I always wished I had time to join their team. Do yall do any events locally?

[@tannerprice2875]

@@EngineeringAfterHours Oh, nice! We're good friends with their advisor (OSU alum) and team members. About half our team is from DFW anyway, so we are trying to do more events in that general area. We were at UTA a few weeks ago at the Texas Autocross Weekend.

[@LucaRovariss]

Why dont use arduino for chance speed of fan when G force increase?

[@theetonster]

As a person who is into RCs and 3d printing I find this very cool! I am a speed runner and I am trying to figure out how I could apply this to my cars. I would recommend 1/8 BSR foam tires. They come in different shore ratings (softness). That's what I use on my cars. Great video! Subbed!

[@curvs4me]

Great demonstration. I hadn't thought of that for lateral acceleration but what an advantage! Parts breakage will be the next hurdle when harnessing all the torque on the low end. You're going to need an Arduino or Raspberry etc controlling fan speed. A gyroscope will aid in fan speed changes with bumps coupled with a map sensor.

[@tm5123]

Would be cool if you could make a massive venturi tunnel mod for the RC car, and underpressure that with the fan?

[@djangoraineault1492]

For drive shafts you should get the hot racing driveshafts

[@0Ninja0Dude0]

I'm new to the rc scene and not a scientist by any means but I think if you throw a 1/8 scale brushless on it with a 4s lipo and adjust the gearing in your differentials. burn out them slicks a bit like drag racers you could get this thing 75+ mph easily plus with a larger motor you could use more force on those skirt hinges for improved vacuum. Also if your going to block your shocks with tubing try it above the caps of the shocks

[@0Ninja0Dude0]

You could also just put some collection bags on the exhaust ducts and have the best vacuum ever😂

[@EngineeringAfterHours]

I just picked up a 6S setup so its going to fly for sure. I still need to work on tore warming and prep. And no doubt about the vacuum lol. Or reverse it and make a leaf blower.

[@0Ninja0Dude0]

@@EngineeringAfterHours so pumped to see what's next!

[@ITpanda]

I want to see someone do a recreation of the scorcher rc car. I have such great memories of that little car, from when I was growing up.

[@jabwai]

though this might take considerable r&D but if you added a programmable accelerometer so the car could gauge it's angle and adjust the vacuum pressure and have racing that goes up walls and inverted

[@Arzon527]

I can imagine a clean RC track that's almost IRL Rocket League in physics. Pretty cool.

[@djangoraineault1492]

I think I got the 4x4 rear on my 2wd slash they work amazing with my max 10 setup or any esc combo u Throw at it they haven't Broken anything the driveshafts are really strong

[@landis277]

I like this build but I don’t get why it still has a brushed motor

[@ranjiyu5917]

what if.... the vacuumed area were 2 separate chambers... 1 for each fan.. and bristles for side skirts? just a thought.. I'm gonna try your idea first.

[@EngineeringAfterHours]

Brustles didn't work so well but I love the idea of 2 separate chambers. I considered doing this for testing but you have to do front and rear chambers instead of side by side or you may have unbalanced downforce

[@macbook802]

These new top speed runners should employ this

[@EngineeringAfterHours]

This car is more designed for acceleration so it's got quite a bit of drag. Speed runners usually want a more aerodynamically efficient body so this may give them problems. I've thought about building a speed rig, but I don't live near anywhere that I can actually test it regularly.

[@SGTMARSHALL1]

Leaverage your thrust by pointing you edf exhaust down not just back. Add dimples to your tyres like a golf ball for a gecko like effect of mini suction caps, the effect will vary depending on terrain and size and shape of dimples