BMAX2 MR bottoming out
 

Hi,

I recently changed my dex210 to the Yokomo bmax2 MR. I really like how the car behaves in turns but I feel the car bottoming out (specially on the rear) landing on jumps making me waste a lot of time (my dex used to be so smooth). I am using the kit springs (blue and blue-long) and AE 35 shock oil and on the rear I tried the original pistons (1,3 mm holes I guess) and 2 holes with 1,7 and 1,5. Still haven't gone anywhere. Any ideas? Does this car need a heavier shock oil? Do i need to add some rebound? How much?

The only weight I added were 70g under the lipo.

Cheers.

Pistons as per manual have way to little pack. Try the smallest kit pistons in the rear as a starting point. For detailed set-up advice you should ask around your local track.
If the shocks feel ok but the car bottoms out nontheless, you could put some old o-rings on the outside of the shock shafts similarly to the bump stops supplied with other cars (AE?). In the front, the car likes heavier oils, I am currently on 550 cst with 1.6 two-hole pistons, which is slightly heavier than AE 42.5 wt.

Unfortunately there aren't many BMAX2 running around here.

Tracks on the region have jumps with very short receptions or no reception at all, so cars fly and land on flat ground.

Any suggestion for the rear?

Difficult to say without knowing the track. Too heavy shock oil can make your car's handling erratic, but you'll need more pack than with the kit set-up for sure. Following your description I'd try the 1.5 pistons, 40 wt oil and some o-rings/bump stops on the outside the shocks for a start.

Too little pack if you're running that light an oil with those pistons. Try something like this, found it to be great on a bumpy astro-track with jumps. Still works fantastic on high-grip carpet tracks too, wouldn't change a thing!

Front: 35wt - #2 kit pistons, kit spring
Rear: 30wt - #1 kit pistons, lighter, associated white spring

I dont have this problem. On the rear I'm running kit springs, kit pistons, 27.5 ae oil, in on tower out on arms. No additional weight and shorty all the way back.

I'd take out the additional under lipo weight.
I find the kit blue xl springs work well. I keep going back to them. They are quite stiff. I found a softer spring makes the car want to collapse at the rear.

I've tried a bunch of pistons and some don't offer enough pack. the kit piston is a bit light on pack, as is AE 1.7. I'm now using AE 1.6 piston front and rear, with 500cst front and 400cst rear oils.

what's your ride height? noticed lots of setup sheets had low 17-18mm ride heights, but found that was far too low for any tracks with jumps. iron about 22mm rear ride height, and a touch lower in front

Neal, are you using the cheapo molded pistons or the expensive machined ones? Also are they flat of tapered?

Cheers

The ones that came with my AE big bore shocks, flat. I guess they are the moulded.

I think the 3x1.3mm pistons would be a good one to try next.

Cheers :)

Hey guys,

thanks for your inputs. How do the Associated pistons offer more pack than the Yokos?

I mean, I'm assuming AE 2 holes 1.6 is the same as the Yoko 1.6, or am I wrong? Is its diameter a little bit bigger? Are they slightly thicker? Do you actually note any difference?

Regarding car height, I notice the car can't go much higher than 18~19 mm on the front. On the rear I guess I can try to get it to 2mm without any problems.

Cheers

I'd imagine a two hole 1.6 from either manufacturer would perform the same. I was comparing AE 2x1.6 flat with yok kit tapered 4x1.3mm. the AE ones have more pack.

I don't understand your reply about ride height?

Sorry,

I was trying to say that my car height with blue springs is now at 18~19 mm (front and rear). On the front I think I can't get it to raise it anymore. The adjusting nut has reached the end of the screw on the front shocks. On the rear there's plenty of screw to go, so I can still raise it some more.

That's what I was trying to say :).

Yep thats true, it seems that the yoko fronts are a little short, have a look at getting a pair of the AE fronts or AVID, they are a little longer and work well.
Maybe even losi ones work as well but haven't tested them.

Im using AE flat ones 1.6 F+R, oil Ill have to get back to you on.

I also tried 1.7/1.6 with two 1.1 holes as well... worked well as you get the nice big hole movement along with the 1.1 pack when you land flat or wrong.

I'm going to try some CSI/CRP pistons. Will build the shocks tonight and will know the performance after the meeting of Sunday. :thumbsup:

let us know how it goes ;).