Project BMP

Page 30

   
 
 

Tweaking

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With the addition of the D60 axles I was experiencing some rubbing between the front driveshaft and the transmission (the positions of the driveshaft changed slightly due to the different pinion locations of the D60 vs. the old Toyota axles).  From what I could tell Toyota carrier bearing was allowing too much movement of the driveshaft.  I replaced the carrier bearing with a solid pillow block bearing from Surplus Center.

The ID of the new bearing was a perfect match for the shaft on the Toyota two piece driveshaft.  The only thing that concerns me with this setup is the bearing is not sealed very well and it is only designed for a max of 2200rpms.  I plan to keep it well greased to keep any moisture out and I am hoping the bearing is underrated as far as the rpms go (the drive shafts spin under 2000rpms in any gear under 4th).  I wouldn't recommend this bearing for a street driven rig. 

The mounting method for this bearing turned out kind of strange due to space constraints.  So far I haven't had anymore interferences so the change looks to be a success.

After getting some more seat time I decide to make some more changes to the suspension. The big driver of the changes was some interferences both front and rear.  Out back I had a bump stop ripped off while crawling which allowed my driveshaft to impact the frame.   Up front I cracked my alternator when the upper link mount hit it after a hard landing. The only real solution was to raise the whole vehicle by raising the lower shock mounting point or lowering the upper shock mounting point.   Raising the vehicle also had some additional benefits besides limiting the up travel, namely raising the belly for more clearance and allowing for more travel before the bump stop came into play.  While the rig was very stable off road, it road kind of harsh on road due to only having 2-3 inches of travel before hitting the bump stops. 

As you can see above I chose to re-make the lower shock mount tabs and made them all two inches taller.  There are actually 3 holes in each tab, the lowest is where the original mounting hole was.  I did this in case I needed to drop the rig for whatever reason down the road, I could just chop the tab down and use the next lower hole.  The tabs were changed out in the back as well and now I have over 4" of travel before the bump stop contacts its pad.  This change made a huge difference on the dirt roads with the tradeoff being slightly more body roll.  At the same time I am also trying a lighter spring combo out back, I retained the 175lb lower spring and swapped the upper 130lb spring out for a 90lb spring.  This change also affected the ride quality for the better but allows for slightly more body roll.

So I have pretty much drawn the conclusion that your can't have a very smooth hi-speed ride with little up travel and that allowing more up travel and using lighter spring rates to smooth out the ride effect stability in a negative way.  To compensate for the extra body roll off road I started using my winch more often to suck down the front end.  I found that whenever the body started to lean I could tighten the winch which stiffened up the shocks and  leveled out the body.  This worked so well I plan on installing a small winch in the rear of the buggy to allow me to do the same thing in the rear.   Up till now I really only used the winch to pull down the front end during climbs.

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