My obsession with idler pulleys

Hello community,

This is a topic I’ve been working on for some time now and I bring it up again because I think it might be useful to those interested. Additionally, I would like to give credit to the work of others whose ideas and products gave my configuration shape.

I built a board in May, and quickly realized that the most enjoyable part of eSkating is blasting up hills! Opinion aside, I built a board for exactly that purpose.

The problem with belt tension and the skipping teeth pissed me off, but also terrified me when braking downhill. The motor noise under heavy tension, and the strain on the hardware was unacceptable to me, so I set out to eliminate it.

I read a few posts about the benefit of idler pulleys, but couldn’t find any (inexpensive) caliber2 motor mounts that had 'em. So I started modifying the parts I already had and came to a solution.

That is a torqueboards mount with a shoulder -bolt (8mm x 20), standard skateboard bearings, a bunch of speed-washers, and a flange nut. I barely have the clearance between the wheel and motor, so I wanted to try a new configuration.

I purchased the incredibly well made reverse-mount from torqueboards, to free up some ground clearance, and for the space it afforded for the idler. After some rudimentary measurements, i drilled a hole and bolted it up.

The pulley requires a longer belt, and I found that the ideal fit is in the 340-355 mm range. The configuration below is with a 340-5m-15 from D&D Powerdrive (Amazon) and fits well, but is at the lower limit of the CTC range of the motor plate in a 15/40 tooth ratio.

I will be running a 15/36 tooth ratio on the other wheel (for higher top speed), and will add to this post when I get it put together later today.

As I mentioned earlier, the purpose of this post is to help others in eliminating the belt tension/skipping-teeth trade-off. I also would like to see more options out there for sale that come with an idler!!

As far as “credit wherecredit is due” my inspiration for the mod is an article by @JuniorPotato93

And thanks to @torqueboards for the hardware that accommodates the modification. Dexter’s reverse mount is the first I’ve seen that has the CTC headroom for my needs, and I couldn’t be happier with it!

Again, this is a simple addition to a brilliant product that is intended to improve braking capabilities and acceleration, and extend the belt/hardware life in high performance builds. Gotta go set up the other motor, and more results will follow.

Thanks for reading, I hope this was beneficial so far.


Nice work! Just FYI, it’s better to put the idler on the slack side of the drive train. What did you use to drill a hole into the mount?


Sorry if this is a bit off topic but is it ok to have two different gear ratios on different wheels? because wouldn’t one wheels spin faster the the other?

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@pat.speed no its fine. @Jinra you are right, he does have it on the slack side though.
@PatRocks I have been saying this for a LONG time now! Idler pulleys are the best! I will never build another board without them. If anyone has an obsession with idlers it’s me LOL.


You’re right, I was thinking of inward mount.

@lowGuido How do you create the slot on the mount for the idler? and what screw do you use?

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I just drill a 7.5mm hole and thread an 8mm bolt through. you can even drill an 8mm hole and use a nut on the other side to hold it.

I have been meaning to make a video about this for a while now.


Idler are working great for me. Way more brakes. The bend doesn’t even have to be that much. Only issue i had is the idler bearings lost all the oil quickly. Im trying white lithium grease now. Heard smaller 8x16x5 might be better for high speed that idler spins at.

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I’ve order some 6mm bore bearings to do just this. I tried using standerd 22mm bearings with its 8mm bore is just too big for v4 diy mount.

One of the bearings I ordered are 14mm, and the other ones are 17mm. So I hope to have plenty of room.

I’m planing on having maybe two idle pulleys per mount. One for forward movement, and one for braking. I didn’t see a lot of talk about duel idle pulleys, but it will mesh more teeth, and it should allow me to run a loosed belt so that should be good.

Your vids don’t get advertised enough haha. What bit do you recommend for drilling through aluminum?

Aluminum is prettying easy to drill, just used a metal drill bit, lube the cutting tool, use a punch to start the hole, and drill a pilot hole.


SO TRUE!!! I’m the same, I will not build without!

I used an HSS 7/32 bit to drill, I believe. It took a little filing to fit the m6 threads though. I did not tap the mount, because I rely on the flange nut for strength and stability of the pulley

And here we have it!! Effortless hill climbing, full-stop downhill braking, and the timeless beauty of gorilla tape


Eventually, I’ll replace the 6355 with a second 6374. For now, the two are just fantastic together. I’m running both speed controllers as masters, so the gears don’t matter. I also would like to play with different kv motors, for the “turbo” effect on top speed

awesome! UDR posse represent!

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If i currently use a 280mm belt, do you think 300m would be enough extra for an idler?

What mount do you have? Rather, how much ctc range? I found it difficult to clear both the motor and the wheel/pulley with shorter mounts

I was using a 265 on a 15 / 40 ratio, and when I added the pulley to the inboard motor mounts, I had to increase to a 285

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So you’re using bolts as a shaft, the bearings are rotating on the threads? Or do you file the thread down?

Do you put speed rings in between the bearings as well or only on outer sides?

Lastly, if using 6mm bearings, what do you use instead of a speed rings?

There’s enough tension on the bearing for it to spin without causing the bit on the bolt to spin along the bolt (less friction on the actual ball bearings than on the bolt).