Originally Posted by
windellmc
First off make sure you did not build the diffs with the small S3 orings behind the 4 small gears in the diffs. Then try 3 degrees rear toe in, 5k rear diff oil, if you do not need a lot of punch to clear jumps right out of corners on your track, 5k center diff oil should also help but you will lose a fair amount of punch. Run the lower hinge pin hole in the rear hub and run the link long. All of these should help. You can also space your rear hubs forward to get more traction. I also run 350 rear shock oil.
+1 on virtually all of this.
I'm not sure about 3 degrees of toe though. It DOES make the rear more planted, but it also makes it harder to recover if you get sideways.
Also... smaller rear swaybar will give you more cornering bite in the rear... if you already have the smallest rear bar, you can go bigger on the front bar to take some traction away from the front, which essentially does the same thing to balance the handling.
Mugen swaybars are nice too... adjustable... if you loosed the set screws on the bar ends and slide them OUT, it is like going down in bar size... slide them in is like going up in bar size. (don't forget to re-tighten them!)
Get a camber gauge and be sure to set them all even. The mugen seems to like a lot of camber- we used to run about 3.5 degrees, which is a LOT. Start with at least about 2 degrees, but don't overdo it! (3.5 wouldn't work well with Crimefighters due to the flat tire profile!) If you can get your hands on a Hudy setup station (a little pricey, but worth it!) you can also set front toe. Try about 1 degree OUT per side... if the car turns in TOO abruptly, reduce it to half a degree per side. You could also set it with graph paper, a protractor, and just some flat plates of metal or plastic with a hole for the hub and the same distance from the hole to the end as you have from the hole to the center of the tire tread on your wheels. A camber gauge is available for about $10 or so... but that Hudy station that sets toe is over $100... nice, but you can go the cheap route with graph paper and protractor if you are on a budget!
Leaning your shocks in at the top will give more cornering bite too... but also makes the car get upset over bumps easier. EVERYTHING is a tradeoff.
7k in the center diff like you have makes the car very aggressive. Going down to 5k will calm it down. 5k front 5k center 2k or 3k rear is a good starting point. 5-7-1 like you have is a great setup... for an experienced driver that LIKES a car to be loose and aggressive! The center diff in this case is probably more of your problem than the rear... try 5 and see if it doesn't calm things down significantly.
Make ONE CHANGE AT A TIME and note the results, then continue from there. It is a painstaking process to set a car up for your preferences, and since every driver is different, what works for one may not be a good setup for another.
And just a word of caution: The Mugen is THE most planted, stable, forgiving, easy-to-drive car made... and it is tough as nails! Don't even think about changing cars if you think that one is too loose. Just work with the setup to get it where you want it to be.