XRAY - Model racing cars

If you live near a shop that sells mugen o-rings buy some of these.

http://www.carolinasrc.com/Webstore/Scr ... oduct=2421

Lot more expensive than Carr but my old stash thats been sealed in a little crack ziplock for a year or 2 measure out better with the low qual calipers I have with me right now than my X-RAY o-rings that do seal.Like I said mine were old & as you know from batch to batch things change but worth a try. I didnt go to the extent of measuringthe bore on the 808 shocks but did on my mbx5t conversion as its apart for rebuild right now. Mugen shaft is 3.48mm & bore is 7.01mm.Now since your inspecting yours could you post the bore dia?

The bore on the XT8 Shocks is 7.04 and its 6.98 deep. The 808 shocks that dont leak are 7.05 bore and 7.11 deep. This is exactly th opposite of what I expected to see if variation was the reason for the leaking. The 808 shocks that don't leak are actually compressing the o-rings less.

I don't see anything inside the oring bore that looks irregular. Its all smooth and clean.

The plastic o-ring spacer parts are all almost identical dimensionally.

All of the shock shafts measure 3.48mm.


Now I'm really confused. I'm not sure what to look at next..... I can't find anything to point at. This is making me crazy.

I have an 808 that doesn't leak and an XT8 '09 on order so I have been taking an interest.
The swelling would appear to be the reason for the leaking, at least it's the most likely thing to be suggested so far, But
It could be caused by 3 things
The O-Ring material
The Green slime
The brand of silicon oil

The obvious one is the O-Ring, but is one of the other 2 reasons above common to all the leaks experienced? that will tell you if its the O-Rings or not, or change the oil and don't use the green slime and see if the same thing happens

It leaked with both the kit supplied Xray oils and with Losi oil so I dont think it can be blamed on the oil at this point.

I just finished rebuilding them using the Mugen o-rings and no green slime. I didn't have enough extra Xray o-rings to do all of the shocks so I used the Mugen ones I just got in the mail today. They seem to be a little thicker and slightly tighter on the shock shaft so I figured they would seal tighter and while I do want to figure out exactly what was causing it, I am sick of rebuilding these things and just want it fixed. So I'm afraid i wont know if it was the green slime or the o-rings IF this fixes it.

I don't think I'm going to get to race this week end so it will probably be at least another weekend until I get to test it and find out if this did the trick anyway.

Thinking back, The last time I rebuilt them and replaced the o-rings with the ones Rocco sent me I did it the night before I raced it. Then a week later I raced again and they started leaking. I'm wondering if while they were still fresh and not even a day old they hadn't swelled yet so they worked fine, then after sitting for another week they had time to do whatever it was they did and then they started leaking.

EDIT: I guess as a precaution I would say its not a good idea to use green slime. Maybe someone else who is also having a leaking problem can tell us if they used green slime and what brand of oil they used.

I have never used green slime or any other lube on shock seals, I just make sure they are wet with the shock oil I'm going to use.
never had a problem (but have only just changed brands to Xray)

The amount they swell probably wouldnt be anough to catch your eye. At least the swelling I saw in the shock rings probably wouldnt unless you had new and old side by side and were looking very very carefully. The only reason I picked it up is because I am looking at this stuff in such detail trying to figure out what is going on here. Once you know the swelling is there and you look at the 2 o-rings side by side you can tell. I could set one new ring in with the 8 o-rings I just removed from the shocks and pick out the new one every time. It not alot different, but just enough to look a little different.

OK. I think I got this leaking issue licked now. The Mugen o-rings seem to have done the trick. 3 race days without leaking. And I'm really starting to like this truggy again. Dang thing is just fast. Great results the last 3 races. 2nd, 1st and 5th (was runnin 2nd behind another XT8 until the nut the holds the front upper arm link came off and I had to limp the rest of the race with a floppy wheel. Still took 5th though. )