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This is what I have found out about the setup of the MR4TC.  Don't take these tips as rules, but try it yourself and see if you agree. Remember that everything depends on conditions, driving styles etc.. Anyway, I hope these tips will be useful and good luck racing!

These are my tips mostly for asphalt running but you will hopefully find them useful when running on carpet as well. I will not cover all parameters that you can adjust, only those I feel are most important. 

First, check my standard setup that work well for me almost everywhere.

Here are a few critical points when setting up the MR4TC:

- tires and foams are always the most important
- shock lengths are extremely important.
- use stiffer rear springs and more toe in on the Special
- make sure the diffs are really smooth

Shock Length

As I said, this is very important on the Yokomo. I always try to run the front shocks as short as possible. Longer shocks (more droop) will give a bit more steering but will make the car very unprecise. The front end will wander and it will be very hard to get any feeling for the front end. With my standard setup I try to run 59.8-59.9mm with a ride height of 5mm. This will give the car very little droop. 
Now the rear shock length is not as crucial but still very important. Longer shocks (more droop) will give more grip. I have found 60.2-60.3mm to be good with a 5.5mm ride height. 60.0mm is the shortest I have gone. If you run a lower ride height you obviously have to run shorter shocks if you want to keep the same amount of droop. As a final note...droop screws would be really nice!


Now I know that most people running the Special will tell you that you can run the car softer than the previous cars from Yokomo (Pro, Worlds). This is what I did in the beginning as well. Somehow I thought the car was always a bit close to the limit and difficult to drive. The Special was designed to be a very responsive car (with the battery so close to the middle of the car) but it was almost too responsive. I tried to fix this with running soft (blue) rear springs. This did not work very well so I then asked Masami if he had any cure for it. As it turned out they had experienced the same thing and also had a cure for it. He told me to run green rear springs, which are actually quite a bit stiffer than the yellows that were then the standard setup. He also told me to remover the rear roll bar and run 2 deg toe in. At the next test I tried this and was surprised at how well it worked. The rear end of the car was planted and it was so easy to drive. With more testing I found that in some cases running the green springs would overheat the rear tires. So on my standard setup I run the silver springs (YS-14525) which are in between the yellow and green. I still use the green springs in some cases, depending on tires and temperature.
Silver springs is what I mostly run on the front as well as the make the car very neutral and logical. In really high grip conditions I would use the green springs to calm down the front of the car. I have also used the yellow springs but they make the front a bit slow.

Go to the Yokomo Spring List showing the stiffness rates

Rear Toe In

There are three different hubs for the MR4, 0, 1 and 2 degree. On the previous cars I almost always used 1 deg hubs. After Masami told me about running 2 deg I have always used them. The only time I run 1 deg was when I was having problems with corner-exit-understeer. 

Roll Bars

For the front end there are 3 different roll bars available. The ZS-412F uses very short bars and I would say that this is the type that works least well. The ZS-412FW is the type that was included with the Worlds car and is also included with the Special kit. Finally the latest type is the ZS-412FSP which is also included in the Special kit. I almost always run the silver (1.2mm) SP type roll bar as it gives the smoothest turn in steering. In really high grip conditions you might want to run a stiffer roll bar to calm down the front of the car.
I have basically stopped using the rear roll bar since I started using stiffer rear springs. When I used softer rear springs I used the rear roll bar to keep the rear of the car more stable.

Suspension Arm Position

On the front I always run the front arm in the most extreme angle (lower inner pin hole and upper outer). This will give the car really good steering around the apex of a corner compared to running the arm more horizontal. The car will be also be really stable and controllable during corner-turn-in. Running the arm more horizontal will give the car a bit more turn-in-steering but less around the apex. 
I always run the rear arm in the lower inner and outer holes. Using the upper inner hole will make the rear of the car really stable but the car will roll through the corner (more corner speed) a lot better when running the standard position (lower inner & outer).

Upper Deck and Arm Material

On the Special the upper deck is made of graphite composite. I would probably run this on high grip carpet but on asphalt I run standard plastic upper deck from the MR4TC Worlds. I have additionally removed the 2 center sections of the upper deck to increase flex. This simply give the car a bit more steering and really make the car more consistent and predictable. 
The same goes for the rear arms. The new rear arms are included in the Special kit. I really liked these on carpet but on asphalt I have been running the old standard rear arms (ZS-008R). Again, they give a bit more steering while making the car more consistent. The only negative side of using the old arms is that they don't allow you to set the wheelbase.

One Ways: I always run double one-ways.
Damping: I mostly run 40wt/#3. 
Shock Position: Always in the most stand up position.
Camber Link: #2 front and #1 rear. On high grip carpet I might run the rear link on the bulkhead.
Ride height: Front, 4-5mm. Rear, 4.5-5.5mm.
Wheelbase: Longer will make the car more stable
Caster: Use standard 5 deg blocks as I feel the 3 deg ones make the car difficult to drive.
Camber: Between 0.5 and 2 deg depending on tires and track.

Carpet with Foams

I have never tried this myself but this is what you probably would want to change compared to my setup:

- Front diff and direct center pulley for direct drive
- Stiffer springs (use Yokomo GT4 springs)
- Stiffer damping
- Graphite composite upper deck and new type rear arms
- Rear camber link on bulkhead


car over-responsive, difficult to drive use stiffer rear springs with no roll bar and 2 deg   toe in 
car difficult in chicanes and switch-backs run shorter front shocks
front end "hopping" under acceleration use black grease on dogbones in outdrive, check driveshafts for excessive wear
rear end losing grip over bumps run longer rear shocks

If you have any comments or tips please mail me at: