Why don't people use GT3 pulleys and belts?

One thing I saw a while ago was that htd5 indeed doesnt match our rpm needs and power ratio intended…

I think it was somewhat around 2kw and 5000rpm (in chart seller provided) after that it goes out of its recommended use range.

@Duffman also used different belts/pulleys, if i remember correctly


Evolve boards are using GT3 pulleys and belts originally, but I’ve used HTD5 belts without even knowing that there is a difference. :man_facepalming:

Now I am a bit concerned regarding rpm on those belts.

If the belt’s aren’t skipping, the biggest risk you’re running is dramatically reduced belt life. But that’s about it.


I assume those numbers are only when using the corresponding pulleys. Do you know the effect of using a GT3 belt with HTD pulleys? Will there be an improvement in terms of less belt skipping etc. as well or is the belt/pulley combination the most important part?

Edit: according to this http://www.pfeiferindustries.com/documents/Timing%20Belt%20Tooth%20Profile%20and%20Pitch%20(Interchangeability).pdf a so called RPP (Reinforced Parabolic Profile) belt is also compatible with HTD pulleys. Is an RPP better than GT3?

Edit2: Well looks like using a GT2 belt on a HTD pulley is actually not a good idea (at least at 5M pitch)

I am not sure who to trust though as this document even says an RPP is not recommended to be used with HTD pulleys while the other link shows the RPP to be a drop-in replacement for HTD belts.

Gates has cited:

• Reduced performance • The sprocket/bushing capacity may be too low for new designs

Which equates to reduced belt life (I’m speculating not nearly as bad as HTD currently lasts, since we’re overloading HTD so much).

And that pulley systems currently designed for HTD belts may not be strong enough for the load capacity of GT2 belts. This essentially confirms that using a GT3 belt will increase available torque.

Typically in a drive system the belt is the weakest link, so in the case of failure or lockup of some sort many designs will rely on that belt breaking. If the belt doesn’t break, it could supply excessive torque and damage other systems. This is not true in our case as we aren’t shearing pulleys off of wheels or motors.

This hidden statement was incorrect, my bad.

I’d also like to point out that the document you linked says nothing about GT2 belts on HTD 5M pulleys, it only says not to use GT2 8M and GT2 14M on equally pitched HTD pulleys.

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It says not to use a 5M GT2 belt on a HTD5 pulley - or am I reading this wrong? :thinking:

Edit: checked again and it is actually the other way around int he document. HTD5 should NOT be replaced with 5MGT2 while 8M and 14M apparently can be replaced.

My bad! I must’ve missed that page, my apologies.

Anyways, yes it is “not recommended” however it is not “not compatible”

What’s important to distinguish is that “not recommended” is defined as having potentially reduced service life, or if a different product line is more suitable. I’d say it’s fair to conclude that it isn’t too bad (I’ve personally used GT2 belts on HTD pulleys many times before, not on a skateboard though) and that it’s mostly designated as not recommended because HTD is more suitable for HTD pulleys. 5M HTD differs from 5M GT2 more than the other pitches of GT2 and HTD, so it makes sense that they wouldn’t recommend it.

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I just find all this information very confusing. One document shows the belt to be perfectly fine to use while the next does not recommend exchanging them. Then we have the situation where we are actually exceeding the HTD specifications which in turn however could mean that a previously not recommended belt is in fact the better option. Also what happens then if we only rarely exceed the HTD specifications (during acceleration etc.) and most of time stay in spec when cruising. It’s just so much to consider… :exploding_head:

Do you know of any science papers on this that might shine some light? I can somehow only find very little documentation online.

Edit: I checked out a German book on belts by Raimund Perneder that also says: GT3 belts with 2, 3 and 5M pitch are only compatible with GT3 pulleys. Only pitch 8 and 14 are usable with HTD pulleys.

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basically… yeah. There are some boards that will always exceed the HTD spec when going at higher speeds, and there are some that won’t. But I can guarantee you that nearly all exceed spec on high acceleration.

@Brdchris and @PXSS wanna share some more details of your builds? What kinda ratios, motors, etc are you using? PXSS are your GT3 belts on HTD pulleys or did you manage to find GT2 pulleys? If they’re on HTD, how would you describe the tooth mesh?


I found in duffmans thread he used AT5/T5 belts:

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HTD belts cannot be used on gt2 pulleys and vise versa. You CAN do it, definitely. I have tried. But the performance and service life will suffer. The ideal solution is gt pulleys with gt3 belt. Gt2 and Gt3 have the same profile, the only difference being Gt3 belts (from Gates) are made with improved materials.

The only way esk8 could benefit from this is if our pulleys were made with the gt profile, otherwise forget it.

Oh and: The performance and reliability of your belt has much to do with how you’re using it as much as what belt system it is. HTD with excellent for many people and doesn’t work at all for others. Alignment, running conditions, pulley runout and material, all play a role here. The answer is not as clear cut as a graph from SDP-SI wants it to be

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@TowerCrisis bravo on your contribution above, easily the most interesting read I’ve had in weeks. Thank you


Anyone able to find a source for these types of pulleys? Just searched for 30min and no luck :rage::face_with_symbols_over_mouth:

Edit: for motor pulleys

rly? 5 sec search on ebay https://www.ebay.de/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313.TR12.TRC2.A0.H0.Xgt3+8mm+pulley.TRS0&_nkw=gt3+8mm+pulley&_sacat=0 edit: nvm they are the wrong ones mostly.

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IMG_20181019_163047 I got my GT3 belts today. I am no expert at this but i have a couple eyes in my face… They look 100% compatible with htd to me. I am busy today but i will test them on my trampa, let’s see the difference.


I just went to the park on my trampa for a test ride. I was really unlucky tho. The cops were bored to tears and decided to tag me(it’s illegal here) so i had to escape from them, ride slowly and try not no draw attention. Even like that i managed to climb a steep hill, sprint a lane and test brakes. I didn’t notice a better torque but the brakes somehow work better. Please don’t take my opinion as a reference because i just had a lousy ride with the cops on my butt. Right now i think it’s totally worth It if you have no belts, the upgrade is not worth It if you have small pockets. That’s just my first impression, i could find cheaper belts and change my mind so again, don’t mind my opinion.


when in doubt just dip out!! :stuck_out_tongue_winking_eye:


Glad you evaded the cops!! Based on the above information, I would think that the motor pulleys in the gt2/3 profile will have the most significant impact on performance, no? I’ve only seen teeth skip on the motor side…


I also wonder how the performance would change using GT3 motor pulleys


Interesting topic… the science seems convincing. Has anyone ever bought the upgraded htd5 Kevlar belts.They were more money than the regular ones so I didn’t try them.

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