View Full Version : FWD (front wheel drive) chassis

2007.07.09, 01:09 PM
Being a noobish driver I've never been quite happy with the handling of the RWD MiniZ. This became especially apparent when driving on track. While going out of corners 2 things could happen: understeer or, if you push the car too hard, oversteer. Besides the car brakes on rear wheels only on contrary to real cars which causes spinouts on low grip surfaces. It's same thing going into corners, will the car turn-in properly or will it understeer? The end result is that I drove my car at pedestrian speed (feeling that 70% of it's potential is wasted), and I wanted a solution to this.

I always thought AWD would be a solution, I mean it's almost like a real car, both driving and braking on 4 wheels, and everyone knows that AWD cars, no matter make or model, handles well. But this was back in 2005 before I knew of the AWD (besides it was too expensive for me anyway), and so I thought the next best thing would be a FWD.

Searching on the net I soon realized there weren't any FWD builds to take inspiration of, the closest thing were FWD converted xmods, and these were wrong as they have a rear weight bias. Then I'm left with building a FWD chassis on my own, and actually it worked.


This first build, though it suffered bad precision between parts and generally worthless reliablility, did handle well, much better than the RWD it was from beginning. Firstly, it had good braking with super short stopping distance and no spin-out risk. Cornering was very controllable too, if I wanted some understeer, I just gave throttle, if I want some lift-off oversteer I just release the throttle. By constantly blipping the throttle it was easy, to "feel" how the car behaved and shifted it's weight. I took it to the track once and won against a equally newbie friend with his twice as fast MR02. Unfortunately it was just as fragile as it looks, not because it was built by wood, but because the space-frame chassis had bad architecture (having a combined bumper/battery holder is no good) and was hold together by CA-glue, and none of them lasted any crashes.

Scrapping the old one I spent the following 1,5 years fruitlessly thinking out plans on a new FWD. Then came the Micro T, and the ASC Golf body, and it struck me: "what a perfect match"! So I went ahead and built my dream:



http://img518.imageshack.us/img518/909/ext07rralaw2.th.jpg (http://img518.imageshack.us/my.php?image=ext07rralaw2.jpg) http://img146.imageshack.us/img146/1381/chassis03flalbf1.th.jpg (http://img146.imageshack.us/my.php?image=chassis03flalbf1.jpg) http://img146.imageshack.us/img146/1567/chassis03bleu5.th.jpg (http://img146.imageshack.us/my.php?image=chassis03bleu5.jpg) http://img119.imageshack.us/img119/1628/chassis03srlyh8.th.jpg (http://img119.imageshack.us/my.php?image=chassis03srlyh8.jpg)

By now I could also afford the stock MA-010, I went ahead and bought one. To my dissapointment it didn't handle as well as I hoped, still it's superior to MR02. A comparison of the FWD vs the AWD these would be interesting then:


For your reference my best lap on that track with an MR02 is 13.1s, but mean laptime is a dismal 16s). Needless to say I was a bit surprised at the result too. I'm fully aware all those theoretical arguments against the FWD, the main one being that FWD sucks because it understeers with all that weight up front. Well, I say on drifting tires it's true (I've tried), but the grippier tires equipped the less understeer. I certainly couldn't see any understeer on the video :)

To explain how this car feels to drive, think of it as an opposite of RWD. It oversteers a bit when going into corners and is stable when going out. At full throttle, it's more stable at low speed than at high speed. In the curvy bits it sort of brakes, turns, and accelerates for you automatically. So all one have to do is keep throttle at a constant 70% and concentrate on steering, which yields a very pleasant "I'm pushing this car to the limit" kind of feeling. There's one gripe however: it is not very stable at high speeds, so steering need to be careful on the straights, but overall it is still easier to master than the RWD or even the AWD.

My point is then, since FWD is so noobie-friendly - which I believe most of the Mini-Z drivers are, if not else in the beginning - it should be made mainstream. I'd really like see Kyosho have FWD as their next release. If they could fit a 130-motor in front of the front wheels, a lockable diff between, preferrably some good suspension and a reasonable price I would be so happy.

So do you guys think? if a FWD chassis would be released by a known hobby manufacturer for let's say $150 RTR, would you buy one? Because I'm seriously thinking of writing a suggestion to Kyosho about this.

2007.07.09, 01:56 PM
not to discredit you or your opinions but i think a dedicated fwd chassis would be a waste of money when you can modify the existing awd to do the same albeit withouth the same weight bias. keeping the weight toward the center i'm told is much better for racing anyhow so accuracy is not really my driving point. an example is that i don't care about using awd bodies on my rwd car or the other way around.
fwd has been discussed on this forum before and i believe the general concensus is that a fwd does not make the best competitive racing car. nto that it can't be done with the right parts and more importantly the right driver but the existing formats are simply better out of the box.
given most newbies are heavy on the throttle i would argue that the trouble at high speeds for an fwd would be more of a detriment to a newbie vs. say an awd which is very easy to drive out of the box.

check some posts by marc as he's tried fwd i believe with the existing awd chassis.

thank you for posting and welcome to the forum! :cool:

2007.07.09, 02:24 PM
Hey there. Yes I have tried a fwd conversion with the Xmods. Reason being, is how many Honda Civics do you see with rear wheel or all wheel drive? So I got the AWD kit and removed the rear gears on it. It really did handle like an FWD car. It would easily do reverse 180's, and it could not corner very fast do to the under stear situation.
I personally drive a 2000 Honda Insight. A wonderful 56mpg fuel sipping car. I've been wanting to build an RC of it.
My first attempt was with the MR01 chassis, however the rear was an issue. That being on the Insight, the rear wheels have a narrower track than the front wheels. This makes handlign odd. I can't really explain the sensation when you try and push this car hard around turns.
From the Ultraman cartoon series, there exists some where a 1/24 scale plastic model toy of the Honda Insight. It is silver, blue, and orange, and has a blue light on top. This is the perfect size for a Mini-Z. Again, the issue was the rear wheels.
Now that we have Kyosho's wonderful AWD, I thought about converting that to front wheel drive, and make a custome rear section that would allow the wheels to be closer together, thus fitting inside the narrow'ed body.
Only problem is, I can't find this toy car anywhere. I was surprised to find it in the first place years ago. Purchased it from T@y East and havn't seen it since.
As arch said, FWD probably won't be very competative do to it's nature. However, if you want it for personal reasons, go ahead with your project! FWD might be good for beginners if you don't have to worry about spinning out as typical of RWD cars. And welcome to the forum as well!

2007.07.09, 02:41 PM
It look's like you made some good headway on this. I can see a FF (front motor, front drive) autocross class. About the closest I came to a front driver was with my AWD with a front one way diff in it, it drove like a front driver but with the brake effect in the rear.

Still nice to see someone push the envelope from time to time.

2007.07.09, 02:58 PM
i agree with hammerz, very nice to see innovative thinking:) i enjoy seeing the pictures. etc.

2007.07.09, 03:35 PM
Nice project!
I also have experimented the AWD>FWD conversion with my MA010, basically replacing the rear transmission with a simple plastic "U plate" that holds an axle borrowed from an ASC.
Soft foams front are required for that thing to start moving :D But it is real fun, and it will NEVER spin out in the corners. I did that last year, all I need is to make a clean rear plate and finish that fwd body, Renault R5 or "Le Car" :rolleyes:
Being fwd it is also surprizingly efficient climbing ramps (http://alain.galluser.free.fr/Z/videos/fwd.wmv) :eek:
FWD1 (http://alain.galluser.free.fr/Z/061113Renault5/103.jpg)
FWD2 (http://alain.galluser.free.fr/Z/061113Renault5/104.jpg)
FWD3 (http://alain.galluser.free.fr/Z/061113Renault5/106.jpg)
FWD4 (http://alain.galluser.free.fr/Z/FWDR52.jpg)

2007.07.10, 03:13 AM
Thanks for your feedback.

Ok, I believe my first post got a bit lengthy so some important point I need to clarify:

1) The FWD chassis is aldready finished.
2) The links are for videos, showing how it drives.
3) It is faster than my stock AWD on track (13,6s vs 14,5s, see video, third link)
4) It is way faster than a stock MR02 (16s)
5) (please take no offence on this) This is much better than a FWD converted AWD, be it MA-010 or xmod. This one have the right weight distribution (68% front / 32% rear), you might not believe this but it makes all the difference.

I have converted a MA-010 to FWD too, by replacing the rear diff with a loosened balldiff. It had bad acceleration, too much understeer on throttle, and spun out off throttle. And this is why I had to build my own FWD chassis.

It seems the general consensus on the net is:
"FWD sucks, not because I've tried but I'm not gonna try because i know it sucks".

I aware that there are countless of examples of people that convert their AWD and then got massive understeer, and then concluded that FWD sucks. And to support their clame they come up with a lot of quasi-physics arguments like "the front wheel has too accellerate, brake and steer and that's to much for them resulting in massive understeer", and so forth.

This is a shame, there are 2 kind of drivers the way I see it:
Those who can drive 20 laps around a track very fast without crashing a single time, and those who can't. If you guys belong to the first cathegory let's close this discussion, because the FWD is superior for those in the second cathegory, who isn't pro drivers.

May I ask you to put some weight in the front of your converted cars until they have at least 65% front weight bias, and test drive again.

El Tigre
2007.07.10, 07:26 AM
Nice work, good to see some creative scale designs, though I think you have too much free time.

2007.07.10, 09:27 AM
Nice work, good to see some creative scale designs, though I think you have too much free time.

I agree cool,
but you have too much time on your hands!

2007.07.10, 09:54 AM
i don't think people are putting you down or your ideas, just like anything else though you are not going to get everyoene with the same opinion. :)

i've tried a fwd awd car and i personally did not like it at all. others like marc and fovea3d have tired this to so we are speaking from some level of experience and not just "FWD sucks, not because I've tried but I'm not gonna try because i know it sucks". that may be the case on other fourms however we have some very experienced members here who have looked into this themselves.

i do think you will find yourselve fighting an uphill battle in claiming the fwd is a better racer though. real life applications and series prove otherwise as you don't see many fwd race cars.

i don't doubt that a fwd car may be easier to drive for beginners however you would certainly have to curtail the speed to fight the instability at straight high speeds like you mentioned. the toughest lesson to teach new drivers is not the ride the throttle all the time thus they typ. feed right into the problems you've described with the fwd.

do you have more pictures of your chassis? i certainly appreciate custom designs and work!

2007.07.10, 10:31 AM
I second that arch. We love seeing concepts at work!

2007.07.10, 01:13 PM
Thanks for your kind commnents :) I have a build-up thread at ripper7racing (btw that forum is loaded with interesting customs):

Well I certainly have no doubts of the vast experience of Mini Z you guys have. But I still don't agree that you've really tried the FWD. As I mentioned earlier, the converted AWDs and xmods are not proper FWD because they lack enough weight in front. It's same as if I drove an Iwaver, found it glitchy and then concluded that Mini-Z sucks too because of this. I too have FWD-converted my AWD and I can agree with you that a converted AWD isn't overly impressive.

Anyway I like discussions and won't mind "fighting an upphill battle" (it won't be so interesting if everyone were agreed from the beginning, will it?) I just like to see some real good arguments from both sides. And I must say do appreciate your good down-on-matter tone.

So here you guys have put forth some arguments I'm going to respond to:

1) I've tried a converted FWD and it was no good.
r: You haven't tried a proper FWD, these are not the same thing. Of course I wish I could ship mine over to you but it's pricey for me and you won't know how to repair it in case it breaks. The closest thing would be if you put some weight in your FWD-AWD until it has at least 65% weight in front.

2) There are few FWD race cars in real life
r: In europe, we have touring car championships like the STCC, BTCC, ETCC, WTCC and propably more. In these races, FWD and RWD race agains each other, with the FWD being a few kilos lighter as only handicap. And there's no RWD dominance, in fact in BTCC the leading positions are dominated by FWD. This should illustrate that FWD is at least on par with RWD.
But I think this is a bad example because real car physics is really different from 1/28 scale dito. The MiniZ has ridiculous amount of grip on track, all weight transitions is vastly exaggerated, and the tires increases it's relative grip with increasing load in contrary to real world. Any change-of-direction occur 28x faster in this scale, you've got no time to correct it like in real life. I've never heard of people counter-steering with their MR-02 to avoid oversteer/spin-out. These conditions are ideal for FWD however, it oversteers when you want it to (into corners) and understeers out of corners onto the straight. And both the over/understeer is less pronounced and more predictable than in a RWD. Certainly it's not perfect, as mentioned it oversteers at high speeds, but as long as you're accelerating, you'd be fine. It's only when you've reached top speed when it becomes very sensitive to steering. There's simply so much grip on track that I wished the motor could be even stronger.

Real-world sport cars with strong engines are RWD because they have relatively limited grip compared to power (european touring cars being the exceptions then), so they need to maximize the available grip. And direction changes occur slow enough for the driver to compensate.

3) Newbies still have to be gentle on throttle to drive the FWD properly
r: Yes that applies to RWD and AWD too. But this is the beauty of FWD, it has so intuitive handling that they'll learn automatically. I've driven the RWD for a total of 15hrs and AWD for 1h, and I still haven't figured out how to drive these around a track without crashing. With the FWD it took a few laps and couple of minutes before I could drive it quickly without crashing. Have a look at the video.
And this makes it race-worthy for newbies and the moderately skilled. When they race, most of their time is lost on crashing, or slow driving because of fear of crashing. A FWD is easier to master and lose you less time at crashes. I acknowledge that a FWD accellerates slower than a RWD or AWD, but the difference is not significant unless at pro level (0,3s every lap compared to the 3s you lose on crashing). It's very tolerant to heavy "throttle-fingers", the more throttle, the more stable.

4) 50:50 weight distribution is best for a cars handling
r: I'm told that this statement is based on the hypothetical situation where you have a 4WD and 4-wheel steer with all open diffs going in a perfect round circle. Obviusly this is never the case. A RWD benefits from rear-biased weight distro, a FWD from the opposite. Therefore, cars priced for their handling, like the Ferrari F430, Porsche 911, Carrera GT, and Ford GT, has more weight towards the rear. Therefore, Honda has moved forth the fuel tank under the front seats to give their Civic 70% weight in front.

Why then, have Kyosho not made a FWD already? because it's frigging hard to fit a 130 motor and a diff between those front wheels. Still I'm going to try that for my next build (wish me luck :)). This is not going to happen until next year though. If only I really had that much spare time you thought I have, lol :D

2007.07.10, 01:31 PM
i'll read the rebuttles but have to applaud your good attitude! we do not take differing opinions personally and greatly appreciate those that offer good debate on issues. keep it going :cool:

r7r is certainly a well rounded mod heavy forum. :) the great thing is many/most of them there are also very good contributors here as well. we are lucky to have a very good crossover between us.