I suggest to check the FDR you had in your MI9 which should be around 7.xx depending on the pinion gear you had on the motor. Look at the gear chart table and pick up a ratio close to what you had on the MI9.

One of these is new, the other is over soaked (overnight if I recall correctly).

And some guys here on rc-tech called me crazy because i mentioned the same thing is happening with the shock bladders
After some time they get too big and make it super hard to rebuild the shocks.
Letting them soak in brake cleaner will make bladders and those o-rings swell even more but after letting them sit for quite a while, or heating them up with a hairdryer to accelerate it, the brakecleaner can evaporate out of the bladder/o-ring and they get close to their original size.
I wouldn't recommend this for the O-rings, at least, unless you have no choice because you don't have any spare ones. But for the bladders I haven't noticed any problems yet.

There was a running change for the Mugen shock bladders or maybe the bladders got a new article number. The kit ones were quite stiff and now there are updated ones which are more flexible.
I'm not sure if they changed the material and the swelling is resolved or they updated the geometry/wall thicknesses to achieve the flexibility.

If you wan't to try even softer shock bladders, the schumacher MI9 bladders will fit the MTC3 shock without problems.
They don't swell as fast and are a lot cheaper to replace when they do it.

yep.

If you mean MU-A2175, Tonisport has them in Stock from Today.

The left one definitely looks bigger, but I wouldn't call that an issue. They leak if they don't swell, which is why the manual tells you to soak them first.

Do you have a comparison shot showing 2-3 hours soak (per the manual) vs overnight?

I'm with you on that--I would not call it an issue either. The shock still going to do its work with a swollen x-ring. Still, the original manual already said to soak them first and we were already doing that. The question is why they updated the manual to say don't soak them longer.

I plan to compare a 3 hr treatment with the new and overnight once I build new shocks. I'll report back then.

I've soaked the mugen seasl for a few days before they built super smooth and would do months before they started leaking. I say build them and if they're smooth when built and do leak, I say run them.

The only reason did such a long soak at first, I had noticed the seals would seal better after a couple day after replacing the seals. Figured I would experiment with soak time and noticed a longer soak was beneficial in getting seals swell to size were they seal better and are still smooth.

Getting zero rebound on these shocks are a PITA

looks like the biggest spur gear I can put on the car is a 100, but I can’t get the same gearing I had before. I tried the gearing that Volker and Cruz are running, 90/23 and I can’t get the proper gear mesh. Are they running a different moto mount?

90/23 won't work on the A2709 motor mount. You need A2709-B instead. Sounds like you have an original batch kit.

ok, that’s what I thought. Do I just contact Mugen to get the updated motor mount?

For those that run mod and you have the original motor mount, what spur and pinion are you running? Thanks in advance.

96/24 should get you started

If even with the revised shock bladders you can't get zero rebound you can try Mi9's shock bladders, those are even softer.