: Rear drive belt keeps melting

HSP Killer
19-02-2013, 11:19 AM
Hi Guys,

just a question on why my rear belt to my HPI Sprint to Flux keeps wearing out
time after time, i sick of replacing the rear belt & the pully wheel as they keep burning up,:mad::mad:
a few mods i did to it just so you know,
pinion 90/36
running Lipo 2s
and changed the speed controller to a Trackstar.
attached a photo below


19-02-2013, 12:52 PM
Are you constantly hard on the throttle from a stand still? I've only ever done 1 rear belt and it was from constant abuse. If that's not the case check for movement in rear somewhere that could be causing the shaft to move back and forward which will loosen your belt, and cause it to strip.

19-02-2013, 03:38 PM
Do you have one of the newer ones with the redesigned diff bulkhead or the older ones? The older ones need to have a piece cut off the right bulkhead cos rocks and crap get caught in there and rip the belts to shreds. I went through four or so rear belts in a matter of a couple of months, until I was shown the mod and have only done one or two in the year or so since.
If you've got orange engine plates and shock caps chances are you will have the new style that has the bit already removed, if you've got the purple plates it'll be like mine was.
If you want I can post pics.
Although I've only just noticed that the pic you posted is showing the inside of the belt worn away which suggests that its been skipping the teeth alot. Have you got the belt as tight as it can go?

19-02-2013, 06:48 PM
How much run time are you getting between belt changes?

Are you setting the cam on the pulley shaft to remove the slack and reduce the chance of slipping which causes the belt to slip and burn up, also causes the pulley to become damaged.

You can also install a belt tensioner (custom fit up) this will also help to preserve the belt

HSP Killer
19-02-2013, 09:05 PM
Hi schmarkodave,

I've got the orange engine plates, could you post me some pics of the mods you done on yours please.
also everytime i replace the new belt and pully wheel its as tight as it goes so i dont have much to play around with otherwise it will move the front belt and thats no good, but im thinking of placing a belt tensioner but i have to customise the plate.


20-02-2013, 05:43 AM
Ok, if you've got the orange plates the bulkheads will already be the new type so its doubtful that's your problem. I've just remembered I replaced my whole rear end with one from an orange car anyway, so it doesn't have any mods on it.
I had the problem once of a rear belt being too loose and just skipping over the teeth. It made a really loud clicking sound (kinda like a stick caught in a bicycle wheel) whenever it did it. I fixed it by putting the pulley shaft as far forward as it can go, just by turning the offset bearing holders in the end to the right position and then I tightened the tensioner on the front belt so I didn't get a problem there too.
When I say the offset bearing holders I mean the two black plastic things at each end of the shaft, which the bearings sit in and the shaft goes through. They have a little lump on them that keys into one of the three notches in the motor plates. That's another thing you have to make sure of is that they are lined up in the same notch on either side otherwise the shaft will be crooked across the car.

HSP Killer
20-02-2013, 11:04 AM
can you put some pics of the example you talking about please.

HSP Killer
20-02-2013, 11:07 AM
how can i get a custom fit up tensioner installed on the orange plates?
show me some pics please.

20-02-2013, 01:19 PM
I found this, but dark but gives you an idea http://youtu.be/nOtUUSt6ahc

20-02-2013, 03:47 PM
I found this thread on rctech a while ago.
Has some really great ideas and shows you before and afters pictures of every step he took to do them. The very first step is a rear belt tensioner. There's a crap load of mods in there, most of which I wasn't gunna bother with..maybe one day.
But anyway this gives far more detail then I could possibly give you. So have a read of that, it's an awesome thread :)

I will post a couple of pics of what I'm talking about with the bearing holders too.

20-02-2013, 04:09 PM
These are the things I'm talking about and you can see the little lump on the side there.
They key into the little slots in these holes (I'm sure you knew this from rebuilding it already)
What I didn't realise for a while when I redid mine was that the bearing is actually offset in these plastic bits (you can sort of see it in these pics)
and if you don't put each one in the same slot of both sides, the shaft will be a bit crooked.
You may have already known this, but figured I'd point it out just in case you didn't, cos I know I didn't until someone pointed it out to me, lol. I was a major newbie though :p

HSP Killer
21-02-2013, 09:01 PM
thanks for that great info there but i managed to fix it by removing the front tension and placing on the rear belt. posted a pic.