Final Drive

Swingarm

The swingarm supports the rear wheel and pivots around the motor centerline.

Mounting

• The swingarm joins to the frame doublers via large diameter bearings and a kind of bracket that it bolts to.
• The rear shock connects to the right side of the swingarm crosspiece, on the hump of an arch, making the swingarm asymmetrical.
• The swingarm has threaded holes (M8x1.5mm pitch) for rear stand spools.
• The swingarm supports the rear axle with an adjustment slot for belt tensioning and alignment.

Rear Axle

The rear axle is hollow, threaded on the right side and capped on the left for swingarm fitment.

Years	Inner Diameter	Outer Diameter	Pitch
2013-2014
2015+	11mm	20mm	1.25mm

Removal

This removes the Rear Axle part of Rear Wheel Removal.

Tools

• 27mm socket
• Breaker bar

Instructions

1. Place the motorcycle on a lift or rear stand

Raise just enough that the rear wheel spins freely. 2. Mark/photograph where the alignment marks reside on each side of the axle for re-alignment when re-installing the wheel. 3. On the right side, loosen the rear axle nut (27mm) with the breaker bar. 4. Remove the rear axle nut. 5. Pull the axle part-way out so that the wheel can be moved forward enough to loosen the belt. 6. Pull the belt off of the rear sprocket.

Let it hang outside of the swingarm slightly to avoid interfering with the wheel. 7. From the left side, pull the axle through the wheel.

Install

To replace the rear axle, see rear wheel replacement.

Belt

Zero uses a belt for primary transmission of torque to the rear wheel. It's quiet and lightweight but is a proprietary design that can wear out. If you plan to put a lot of miles on a Zero or risk the belt often, buy a spare belt ahead of time and mind its maintenance.

Belt Risks

Drive belts fail by snapping or by stripping the teeth.

On Landing

The most common situation for a belt snap is when going over a major bump or jump where the rear wheel leaves the ground.

• If, while airborne, the throttle is not immediately relaxed, the rear wheel will rapidly spin up.
• A wheel that is moving extremely quickly in the air will get jerked back to its regular speed on landing. This is transmitted to the belt through the rear sprocket and can easily strip teeth.

From Debris

Gravel or sand that gets thrown between sprocket teeth and the belt will force the belt to expand quickly under load, and can cause it to snap.

Reportedly, sand is a much more reliable path to belt failure than gravel.

The sprocket tooth design is meant to deflect gravel to the inside of the swingarm towards the wheel.

The bike has an upper debris guard made of soft ABS plastic, but does not have a lower guard.

From Mis-Alignment

An unaligned belt can wear really badly and break sooner.

Belt Specifications

Zero's final drive is a custom-designed Gates HTD (high torque drive) Poly Chain Carbon toothed carbon fiber belt.

• It's never been available outside of Zero's parts system.
• It's been the same part for 2012-2016 models.

2017 models shifted to a wider belt that can accommodate more torque/loading.

Years	Width	Pitch	Models	Sprockets	Number of Teeth	Length	OEM Part No.	Photo
2010-2011	14mm	8mm	S/DS	98T / 28T	200		30-02641
2012-2016	〃	〃	S/SR	132T / 28T	220		30-03673 (old logo) 30-08084 (new logo)
〃	〃	〃	DS/DSR	130T / 28T	〃	〃	〃	〃
2017-	17mm	14mm	S 13.0	130T / 28T	〃	〃	〃	〃
〃	〃	〃	FX/FXS DS/DSR SR/S6.5	90T / 20T	158		30-08086
2020-	20	11	SRF	90T / 20T	151		30-08226

Part

Gates GT Carbon, 14mm wide, 8mm pitch, 220 teeth. It's only available from Zero.

P/N's are 30-03673 ("Belt Drive, 220T, 8mm Pitch, 14mm Wide") and also 30-08084 (same belt w/new Zero logo).

One rough match for reference: Gates 8MGT-1760-12 Belt

Another Gates product page that highly indicates a product/technology match: Poly Chain® GT® Carbon™ synchronous belts per Gates drive belts (EMF Thread)

Belt Tension Check

Krikit Tension Gauge

Zero recommends the Gates Krikit belt tension gauge to check belt tension.

Krikit Tension Gauge invoice and box

Krikit Tension Gauge gauge and instructions

Video Guide

MostlyBonkers made a How-to video:

Tips

• Turning the back wheel backwards before measuring will give different readout compared to turning the wheel forwards before measuring using the same spot.

The difference may be significant to the (pre-2017) 20-30kg belt tension specification.

For wide-belt 2017+ models, the tension specification is very wide (~25-75kg) and thus has a lot of leeway but seems worth a rotational check anyway. - The center of the belt can be reached from below, without removing the mudguard.

This is described as a note in 5.14 in the 2015 manual

Steps

More detailed generic instructions for the Krikit deflection device

1. Ensure the blue indicator arm is pressed down.
2. Place the gauge in the center of the belt span, such that it is aligned longitudinally with the belt length.
3. Place a finger on the blue pressure pad and depress this pressure pad.
4. Keep pressing the blue pressure pad until you feel and hear a distinct 'click'. When this 'click' sound is heard, do not press any further.

5. Remove the gauge and read the belt tension by observing the point where the top side of the blue indicator arm crosses the numbered scale on the gauge body.

6. Care must be taken to ensure that the gauge is not 'rocked' when pressing down on the blue pressure pad. The strap above the pressure bar is provided to attach snugly over the finger and prevent any 'rocking' motion.

7. Due to the fact that this device requires some amount of practice and operator skill, the accuracy and repeatability of the tension readings are not high.

Improvement

Because this procedure is not trivial to perform consistently, there is a modification to make the tension gauge easier to align

Gates' Carbon Drive mobile app

As of 2017, the Official Owners Manual also includes a procedure using Gates' Carbon Drive mobile app to check belt tension.

• iOS version
• Android version

Usage

• Use the application in a quiet environment.
• Pluck the belt near the center of the lower belt span, so it vibrates like a guitar string.

Belt Type	Years	Resonant Frequency	Tension Range
Narrow	2013-2016	96.3 Hz – 124 Hz	20 – 30kg
Wide	2017+ (except S 13.0)	42.5 Hz – 73.6 Hz	25 – 76.5kg

The frequency can also be checked with instrument tuning apps such as Tuner-gStrings for Android.

Belt Adjustment

FST Platform/Drive Belt Adjustment

Belt Wear

Generally, watch for belt damage and try to anticipate when to replace the belt to avoid an incident on the road where the belt snaps.

What to Check

• Check the teeth for wear and cracks.

If you see cracks in the tooth forming, the belt is getting old.

If you see deep cracks starting, it's time to replace the belt ASAP.

Rear Drive Belt Wear Analysis

When to Replace

• When it snaps.
• When any teeth have been ground off.

Hard Skips

• If the belt experiences a "hard skip" from debris between the belt and a sprocket, it is likely to fail soon after. Watch it carefully if this happens.

Tension with aging

Apparently, per forum user JaimeC, belts don't wear like chains.

As they get older they'll actually get tighter, not looser like a chain.

• When a chain ages, the little bearing points between the links and rollers wear causing the chain to hang looser.
• When a belt ages, the rubber on the inner/toothed side begins to swell.

Since the Kevlar belt on the outer circumference won't stretch, the inner circumference will shrink making the belt tighter around the sprockets.

Generally, you want to make sure the belt hasn't gotten any tighter since you brought it home.

References

• Drive Belts

Belt Replacement

FST Platform/Drive Belt Replacement Procedure

Sprocket

Sprocket Specifications

Belt				Front				Rear
Width	Pitch	Years	Models	Teeth	Depth	Bore	Other	Teeth	Depth	Bore	Other	Ratio
14mm	8mm	2012-2016	SR	30	15mm	1"	key measurements?	130	15mm	1"		4.33:1
〃	〃	〃	FX/FXS	25	〃	〃	〃	132	〃	〃	〃	5.28:1
〃	〃	〃	S/DS/DSR	28	〃	〃	〃	130	〃	〃	〃	4.64:1
〃	〃	2017-2018	S 13.0	〃	〃	〃	〃	〃	〃	〃	〃	〃
17mm	11mm	〃	FX/FXS/DS/DSR/SR/S6.5	20	17mm		spline measurements?	90	17mm			4.50:1
〃	〃	2019	S/DS/SR/DSR/FX/FXS	〃	〃	〃	〃	〃	〃	〃	〃	〃

Reference

2013 DS chain drive

Re: Big belt Kits for pre-2017 bikes.

Sprocket Wear On Belt

Wear debris from the tire or the road can accumulate on sprocket teeth, putting pressure on the belt which can wear it out faster.

Recommendation

Keep the sprocket teeth clean to minimize wear on the belt.

A non-abrasive brush should be effective.

Front Sprocket Removal / Swap

Removing or replacing the front sprocket on S and X platforms.

Video Guide

Some guidance from Terry in this motor removal thread:

• Basically, if you are doing this to try to get more acceleration by moving from a 28 tooth to a 25 tooth, Harlan recommends trading in the DS on a 2015+ SR or 2016 DSR if you need the off road capabilities. You will get much much more acceleration and not hurt your top end performance.
• On the drive belt side, the upper rear 5mm bolt takes extreme care to remove. It is tapered to locate the motor. There is a very strong chance of stripping the head and have to drill it out. Make sure to have a machine shop close by just in case.

• On the other hand, removal of the motor may not be necessary.

• The other 7 bolts, 3 on the sprocket side and 4 on the rear brake side are the only thing simple and straight forward.

You will need a special 3" or longer 6mm allen head socket for sticking in the hole through the frame at the front of the motor.

1. Remove the rear brake pedal and assembly to get the heel guard out of the way of the top right rear motor bolt.

   Be careful not to strip these bolts either.

   They have Loctite; use a torch.

   And make sure your local hardware store has these replacement bolts handy in case you have to drill them out.

   The rear brake pedal needs to move anyway to get the right swingarm bolt out. - Also the sprocket bolt itself, as well as removing and installing the new sprocket on the shaft can be very difficult. Some of the best professionals have had trouble.

Loctite has been used on everything and you will need a torch to remove them.

Even so, you will need a strap wrench with an old belt as the strap to hold the sprocket and a high power impact wrench. - Even with all that right, you have a chance of stripping or breaking the bolt. The sprocket is pressed pretty tight. - Be very careful not to permanently damage the motor bearings by prying between the motor itself and the sprocket to try to remove it, and also by tapping with a hammer to try to fit the new one on. You will be tempted to do both, but you need to find another way.

A gear puller would be much better. - There are other things to watch for: - Mark your phase leads and pay special attention to the routing. - Don't over-tighten the motor jack nuts and bolts until you have the swingarm back in place as it can pull the frame together slightly making it impossible to get the swingarm in place. - Make sure you unplug the 8 way motor encoder harness and it doesn't get yanked and pull a wire. - The top shock mounting bolt is a 15 and 17 mm and can be done with ratchet wrenches 1/32 of a turn at a time, or without ratchet wrenches if you are known to have extreme patience. It can take a while. The 2014 is a little easier and is (seems to be a) dual 17mm bolt and nut. - The swingarm bolts are 10mm allen head and can be extremely hard to relocate even when working with someone else, a rubber hammer, and a flashlight. Those who have replaced their own belt before can vouch for this. - Again, I doubt too many on this forum have done this, and those who did I'll bet agree with me that it makes more sense after they did it and perhaps had their bike out of commission to work through the things that didn't go right, and would agree to just upgrade to the SR or DSR first vs trying to change the front sprocket. - Also the 25 tooth sprocket will break belts easier as less teeth are engaged than the 28 tooth, which can make it more likely to sheer teeth in the event of a wheelspin, and it bends the belt at a sharper radius which can possibly fatigue the carbon strands more. The SR actually uses a 30 tooth front sprocket which is even nicer to the belt than the 28 tooth.

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Source: zeromanual.com/wiki/FST_Platform/Unofficial_Service_Manual · Wayback capture of 2025-05-17 · wiki last edited 2 May 2020 00:04. Community-written content from the Unofficial Zero Manual, reproduced for preservation; not written or verified by OpenZero. Links to pages that were not mirrored go to the Wayback Machine.