What makes a good rally car?

[Mutantcatmoxie]

Hey guys, I've been reading the forum for a little while now. I've been out of rc for about 20 years. This time around I'm really interested in rally. What are the characteristics I should look for in a good rally car (weight distribution, suspension, etc)? I'm not really looking for brands or models as much as what aspects make a rally car good. Thanks!

[haplm]

As a starter, I would be definitely looking for enough ground clearance (20mm+), sealed/protected drive train and electronics, and availability of good rally tires. It should be possible to fit long enough (75mm and more) oil filled shocks with a good selection of soft (super soft) springs, good differentials, and potentially slipper clutch.

If you want to race, you need to consider how the racing track is going to look like. That will tell you something about max. size of the car, required steering angles, allowed bodies, etc.

[colbynobo]

I once tried to convert a Vaterra V100S to a rally car. I was going to use it for broken pavement and dirt parking lots, so I wasn't concerned about having lots of suspension travel for jumps or clearance. I put on some Tamiya Rally Blocks and jacked up the suspension as high as it would go. I needed to use wheel speed to get the rear end to swing out, but since I was using a 17.5 motor this wasn't too difficult to achieve. Unfortunately, that particular chassis wasn't designed to be dirt friendly so I was constantly getting pebbles stuck in the steering rack and wedged between the driveshaft and chassis. I eventually gave up.

I've never owned a Tamiya XV-01 or a MST XXX-Rally, so I can't speak about how they are. There are plenty of people on this forum that have, so they'll probably step forward soon and say some stuff. It's a bit bigger than the 1/10 scale rally cars, but I purchased a HPI WR8 a few weeks ago. So far, it's been incredible!

[Mutantcatmoxie]

Thanks for the great info guys. As far as differentials go, is there a difference between the ball and gear differentials? Is one usually preferred over the other? When it comes to weight distribution it seems like you want all the weight toward the front and middle of the car to give better steering control. Is that right?

[haplm]

Originally Posted by Mutantcatmoxie

Thanks for the great info guys. As far as differentials go, is there a difference between the ball and gear differentials? Is one usually preferred over the other? When it comes to weight distribution it seems like you want all the weight toward the front and middle of the car to give better steering control. Is that right?

Ball differentials have tendency to slip when you apply a lot of power, so IMO it is better to have gear differentials for rally. If you need slip, you can always use slipper clutch...

You are right with the weight.

[4roller]

Sealed drivetrain is a major need for a rally car. Any bit of off-road will have your drivetrain hurting if it's not sealed. Open belts and gears are a no-no.

It also depends on the terrain and what you would call rally.

Road rally, like unprepared tarmac, then under 20mm of suspension is doable. If you want to to be driving on grass or rutty terrain, you'd probably want more of a buggys suspension.

Scale is also a factor. Cars with touring car bodies (~257mm wheelbase) will be limited large travel suspension (look to buggies or short course chassis), but have the looks you want. 1/10 scale bodies vs larger 1/8 scale bodies.

Suspension tunability, like adjustable
ride height, camber, and toe links.

4wd probably doesn't need mentioning, but yeah it helps.

Tires. Traction for the terrain you want to drive on. You can get many tires for most any RC I would not worry too much about this one. It all depends where you drive, there will never be a best tire for all conditions.

Differentials, geared diffs can handle much more power and require a lot less maintenance. But ball diffs work just fine.

You can make just about any RC into a rally car.

I'd ask yourself, where you want to drive it. I thought I wanted a rally car, but ended up converting my xv-01 into a road car that can handle crappy pavemet. Right now it's far to low to handle even short grass. But drives amazing on all types of tarmac and dusty hard packed dirt.

For the loose and rutty stuff, I ended up buying a MST crawler slapping on a big pinion and turned it into a trail runner to muck around in my back yard. A SCT or Baja truck would have been better suited for speed, but then again I wanted something that looked scale.




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[Mutantcatmoxie]

Thanks for all the information, it's really helping me get a better picture of what I need. Hopefully you'll see a build post from me soon. I'm going with an xv-01 build.