Thanks again ,
The motor really was almost to hot to touch though . And the room temperature was cold (some guys had their coats on ) . I have made some quick and aproximative maths and they suggest a 21 or even a 19t pinion . What I had forgotten was 2 facts on the ZX5 ... The first one is that I'm used to the B44 84t spur whereas the ZX is a 78t spur so a slight higher gearing ... the second is that I had chosen the 25t pinion for the RB5 which as a 2.6:1 final drive ratio and not 2.5:1 like the ZX5 .
Anyway I've just ,as I write , switched on the car on off ground and full throttled it (makes a certain whole sound on the diffs etc) and I've mounted a 21t pinion the sound is exactly the same . That's a very aproximative guess but really the top speed seems the same . And of course I have much more acceleration on my carpet lol .
I know LRP's motor need a lot of gearing doing . My X12 6.5t I had put on the B44 was boiling hot with a 19t pinion (17t equivalent ZX5) I had to drop it to 17t on the B44 to get a nice temperature (just warm) so that's as if I had 15t-16t pinion on the ZX5 (for a 6.5t motor) . What was nice when I tried this is that I had much better acceleration and more top speed all together
Also another thing that I remembered is that with the 19t pinion the car did 25min with a pack whereas the 17t did a nice 35min for more perfomance ! And that was with a much more powerful motor .
Something else to mention is that on the track we have a long straight (the whole gymnasium lenght) and my car was slightly slower than the other until the middle of that straight but it was reaching its top speed a about 3/4 of the straight ... I sometimes had to touch the brake before the max speed was reached .
I'll try to get a 23t pinion as well just to try (I'll have a complete set 17-19-21-23-25 which is nice to have to experiment with) .
One car question :
I've put the car on a scale and it weighs 1580 grams is it ok ?
thanks