Questions about sourcing HPI Sprint 2 CS pulleys and belts

I see 3Racing offers many center pulley options, but what about different length belts? Are these 3Racing center pulleys and diff pulleys compatable with HPI?

Does each manufacture use the same tooth spacing of the pulleys and belts? Or do I have to make sure it is HPI parts or compatable?

I just finished putting together a CS set up on my sprint 2' it's pretty much a universal type of pulley for most belt driven rc cars, I believe it's S3M type of belt.

I have 3racing pulleys on mine, so the belts should work, I actually have a 3racing belt I am planning on using for the rear which is 3mm longer than the stock one.

I found that the belts will fit yokomo just fine but yokomo pulleys don't have the same center bore as the center shaft on the sprint 2, 3racing pulleys fit right in.

Oh and the diff pulleys wont work on the hpi diffs, if you can find a way to fit the 3racing diff in the sprint 2 or know someone that has done that before let me know lol.

Thanks for the reply. I did end up going with the 3Racing pulleys, they took a while to get standard shipping. I'm in the middle of fitting them into the car. I went with a 12T center front, and 18T center rear (150% CS). The Rear belt is just a little too tight, the front belt is really loose. I've driven the car with just the stock front center 15T replaced with the 12T and I can see it already makes a difference with CS.

The 3Racing fit great, they are 4mm bore which is what the HPI Sprint 2 center shaft is. I test fit the pulleys on the shaft are marked where they sat. Then took the shaft out and took the edge of a small file and filed a small flat spot on the shaft for the 3Racing pulley set screws to seat. The shaft can still be used with the stock pulleys.

You are correct the belt is a S3M tooth profile. From research I see a lot of the RC car with belts use this type of tooth profile, but the width of the belts can vary. The HPI Sprint 2 uses 4mm wide front and rear belts. I'm also in the process of taking the belts off and measuring with a 4mm wide long strip of paper. There are many places on the internet that sell small S3M belts. I need a new rear belt anyway, and the front belt is too long and would need a fancy tensioner set up.

I plan to get the correct length shorter front belt to run with my 12T center front pulley, and a correct length or slightly longer rear belt to run with my 18T center rear pulley. I might add a rear tensioner and get the rear belt a little long in case I decide to put a larger pulley in the rear.

As far as the differentials go, I don't plan to change out the pulleys on those...yet.

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