A New Breed... of Custom On and Off-Road Lightweight Electric Bikes.

Vivax Assist

Experienced Vivax Assist Kit Fitters 
(Since 2008) 

As demonstated On ITV News
By GOAT Bikes UK. (That's us too!)

Vivax assist Conversion Kits Available from £2589.

The Vivax Assist, (formerly Gruber Assist)  Is the lightest most concealed electric bike kit available on the market and it is also very quiet running. Maybe it is what you always dreamed of? It comes either with the battery stashed inside the water bottle or in a small saddle bag. And warranty can be extended from 2 years to 3 years when your Vivax assist kit is serviced at the end of year 1 and year 2.

CLICK HERE for 2017 Vivax Assist product catalogue,
Vivax's own info on their Bikes and product info on the kits

We - Electric Mountain Bikes now offer our own range of bikes using the Vivax Assist conversion kit. Offering both on and off road options.
Click the below to see the dedicated website to our GOAT BIKES 
GOAT BIKES - "A New Breed"

Above: How the Vivax Assist works with a commentary explaining the basics.  

Vivax motor and bevel gear fitted to crank

Above: Video of the Vivax Forza CF Road Bike

Above: Check out this video to see how quiet the Vivax assist drive system is!!!

Invisible Performance Package £499


GOAT Bikes - Carbon Elite (Shimano ULTEGRA) E-road bike - £6599
Also available as frameset - £4749 
More info

GOAT Bikes - Race (Shimano ULTEGRA) E-road bike - £5459
More Info

GOAT Bikes- Race (Shimano ULTEGRA) E-road bike - £4999
Also available as frameset and motor kit only - £3499
More info


GOAT Bikes - Trail E-MTB bike £5899
Also available as frameset £4199

GOAT Bikes - Track E-MTB bike £4879
Also available as frameset £3399
More info

Vivax Assist - Road

Vivax Forza frameset
Vivax Forza Carbon Road frame/frameset With Vivax Assist 4.0 fitted £6099 (inc crank, forks, hanger, clamp)
Full specs HERE

Above: Vivax Forza Geometry.

Vivax Assist- Mountain
The Vivax Libero 27.5" Groupset - Shimano XT £5559
Full specs HERE 

The Vivax Previo 27.5" Electric Mountain Bike 10.9Kg  
Groupset - Shimano XTR £7599
Full specs HERE 

The Vivax Optimo 27.5" Electric Mountain Bike 12.9Kg  
Groupset - Shimano XT £4739
Full specs HERE

The Vivax Pico 29" Electric Mountain Bike 12.9Kg  
Groupset - Shimano XT £4639
Full specs HERE

The Vivax Primo 26" Electric Mountain Bike 14.4Kg  
Groupset - Shimano Deore £3839
Full specs HERE

Vivax Assist - Trekking

The Vivax Viaterra 700c Electric Trekking Bike 14.9Kg  
Groupset - Shimano Deore £3929
Full specs HERE

General Information

I hear you asking, "How useful is this kit?"  

The Newer Vivax Assist Has now taken over from the Gruber assist as mentioned above. 
So, I hear you asking, "How useful is this kit when it comes to getting me up that hill?..."
I answer, very useful considering the complete kit only weighs 1.8 Kg's, in fact, not short of miraculous! 
I have a customer that has the technology on his bike (a SRM crank system) that can measure the power that is applied at the pedals when cycling.
He told me that he is a semi-pro rider and could output 360 watts on average over 10 miles. Now, this to me says that if a rider could output 200 watts for this amount of time ,they would be reasonably fit, and remember that his 360 watts for 10 Min's only from a semi pro rider!
The power that he has recorded at the pedals of his bike from the Vivax assist is 150 watts continuously, so added to his 360 watts he is now at Olympic winning standards with help from the Vivax. 
For those of us that output about 150 watts continuously on a jaunt out, the Vivax will be like having the power of a twin brother or sister on board that only weigh 1.8 Kg's.
One of the great things about the kit also, is that the speed at which the motor is revolving can be changed instantly at the push of a button. So if you are racing on the road you will probably have the motor spinning as fast as pos constantly, but if you are enjoying a cruise, then you can set the cadence (speed at which the pedals/cranks are turning) to match the same as your pedalling speed, and if you are climbing a steep hill and are in a low gear, it is good to know that the assistance from the motor is the same as if you were flying along on the flat, because although the motor may be small compared to a big hub motor, the small but amazingly powerful motor is working through as many gears as you have on your bike. With a hub motor it only has one gear and it has to work though out the range of gears and speed capable of. 
I am not putting down hub motors at all, as for grunt up that bank 1000 watts is very useful but maybe a little bulky, but when taking into consideration bike weight of the vivax and available power, It really is a corker, but I must say that with this system you need to know how to change into the next gear as you are cycling as you don't need to stop the motor to change gear. 
At the end of the day clever use of technology can bring a light weight electric bike to the market weighing less than 10 Kg's. I don't think this to be sniffed at at all!! For more info please feel free to give us a call 01458 550304.

Fitting The Kit
Frame requirements:
Aluminium, Steel, Titanium, Magnesium and Scandium or custom carbon. 
Seat tube must be straight and continuous without obtrusion or bends or kinks etc to allow motor insertion right down to the Bottom bracket.
The seat tube must have be 31.6 mm or 30,9 mm inside diameter. This measurement is stamped on the seat post. (27.2mm is very common and is not working)
Seat tube must also be central on top the bottom bracket. (not set slightly forward or back)
Bottom bracket must be threaded. either Italian or BSA are fine.
If these criteria are met then I would say there is a very good chance of conversion.

Emailing pictures or sending links are a great help in determining compatibility, but it is not guaranteed until I have given the thumbs up, and I need to see it for that and start work.

Due to the "Incompatibility law of nature", customers do not have the correct diameter seat post tube, So I can recommend them a Vivax compatible frame with the system installed and then you can swap over parts over from your original frame.
Then there are customers that want a new bike altogether, and often have a good idea of the components they want to fit too. So I have a sourced suppliers that will supply me with high quality frames.A wide range of components can be sourced to build bikes up in a custom fashion . 


The Vivax assist will not fit into a regular carbon frame because there needs to be extra strength in the seat post tube. Carbon Vivax friendly frames have been developed, Carbon with a reinforced seat tube with Kevlar makes it stronger. Vivax will not Issue warranty to the systems fitted to carbon frames not recommended by themselves.

Specialist Electric Bike Building
We specialise in building electric bikes and will discuss which motor option and which style of bike will be best suited to each individual customer, so please let us know what you whats on your mind.

Where is the Motor??
The Vivax assist motor is situated inside the frame and drives the bottom bracket via a bevel gear.

How does it work
With the touch of the button on the handlebars the motor kicks in and gives a surprising amount of assistance.

This bike is fitted with the Vivax Assist. Which only adds 1.8 Kg's. We can fit the kit to your bike if the seat post tube connects centrally to the bottom bracket housing.The motor fits bikes with a seat post diameter of 31.6mm or 30.9mm, check the dimensions that should be stamped on the seat post itself.

Frame only
If your frame does not have the right size seat post tube then you may want to buy a frame with the motor  pre-installed, then build it up with the components from your current bike. There really is a massive choice of complete bikes and frame only set ups. Every bike is custom built to order and every frame is custom fitted with the drive system.

Your style
With the Gruber Assist cycling and electric biking meet. Riding your bike has completely new meaning, whether it is a mountain bike a road bike.

The range of this kit is very good 20 miles or 1.5 hours constant full power use, no problem as the peak power is 150 watts at the pedals which is a very useful boost. I would say your average cyclist will put out less wattage than this, a fit cyclist will output around this and an Olympic winner will put out around 350+ watts when the heat is on, so for a rider pushing 200 watts an extra 150 means you could keep up with an Olympian!

Top speed
The motor is small and light, as is the battery pack (at 1.8kg's for the complete kit), this does not mean the assistance is not strong. When travelling on the flat and undulating, average speeds can be easily is excess of 20 mph with the de-restricted off road motor version. (road legal versions are also available at no extra cost)

On the hills
Up hill, because the power is transferred through the gears the motor runs at its happy efficient speed giving plenty of assistance , just as it does at 20mph on the flatter gradients, although progress is not as fast on the hills, if you sit back and pedal at a comfortable pace and let the motor work harder you will find yourself at the top of that hill without gasping for air. It is truly is amazing what the small powerful motor on a steep hill is capable of. If you want to see for yourself the I invite you to get in touch by phone 01458 550304

Vivax Assist Specifications:-


200 watt service-free sensor less motor 
Length 220 mm 
Weight approx. 730 g.
Required seat tube inner Ø 31,6 or 30,9 mm


High Tech Gear with freewheel
Power transfer to the crank:  Helical, maintenance-free bevel gear-pair

Electronic control unit: 

installed invisibly into the provided seat post, sensor less
Weight approx. 120 g.


Seat post: Alloy seat post length 280mm and 350 mm, 278g. 300mm 
Carbon fibre seat post - length 350 mm, 213 g.
Optional: Seat post rear suspension Cane Creek Thudbuster ST, length 350 mm, 445 grams.


30 Volt Lithium Ion technology
6.0 Amp hours -  850 grams
9.0 Amp hours - 1250 grams. 
Recharge time 4.5 hours


33.6 V, 3 A


Mini button to start/stop and set cadence (RPM)
wireless & wired.

Saddle bag: 
Vivax assist 90 g. Dimensions 180 x 90 x 110 mm

Suitable cranks:Shimano Hollowtech II - with axle length of 120 mm 

Crank set not included in kit price

Frame Requirements
Aluminium, Steel, Titanium, Magnesium and Scandium  or Vivax carbon.
The seat tube must be straight and continuous without obtrusion or bends or kinks etc to allow motor insertion right down to the bottom bracket. 

It must be 31.6 mm or 30,9 mm continuous inside diameter.
The seat tube centre and the Bottom bracket diameter centre should be dead in line, 
this means when the motor is inserted into the seat tube, when looking through the bottom bracket the gear must not be towards the front or back of the bottom bracket. (The gears will not mesh properly as you can imagine if this is not correct.) So, a straight line from the top of the seat tube to the centre of the bottom edge of the bottom bracket should be a mirror image of each other. With the cranks removed this can be tested to a pretty high degree of accuracy with a taught length of twine. 100% compatibility will be confirmed during the installation process)

The seat tube should be at 90 Degrees to the bottom bracket and the therefore the axle too. please call us for more clarity in this area.

Click on the video links below for plenty more info from the Gruber Assist manufacturers, and electricmountainbikes.com at the bottom of the page. 

Remember:- These info videos were made for the Gruber assist and so the noise levels are somewhat more than on the newer Vivax assist.

Vivax Assist FAQ'S

1. How do I know the bike will fit me?
Every care is taken to talk through the process of  building every bike with every customer , so not only will the bike be the right size but all the components on it will be selected to meet your needs as a cyclist

2. Will the drive be restricted or an off road de-restricted version?
Vivax Assist comes in either a unrestricted (off road) version or a road legal version limited to 15mph top speed.

3. Is there a choice of batteries with the Vivax Assst?
Yes there are 2, either 30 Volts 6.0 Ah or 30 volts 9.0 Ah

4. What is the smallest size frame that the Vivax Assist can be fitted to?
A 15 inch frame is as small as it will fit into.

5. Which type of crank/ Bottom bracket is the Vivax assist compatible with?
It is compatible with Hollowtech 2 cranks only and threaded rather than press fit is preferable.

6. What size seat post tube is compatible with the Vivax Assist?
The vivax Assist comes in 2 sizes, 30.9mm and 31.6mm and it must be straight and central over the bottom bracket and with no obstructions apart from water bottle bosses that is.

7. What is the Weight of the Vivax Assist drive System?
The Vivax Assist weighs 1.8 Kg’s in total.

8. Does the battery need any maintenance?
No Maintenance is needed on the battery.

9. Which Chemistry is the Vivax assist battery and how does it like to be cared for?
Battery Is Lithium Ion so there is no memory effect, you can charge it up after every ride or whilst you have lunch or whatever short break you make. This chemistry of battery prefers to be kept topped up and not than left deeply discharged. If you plug in after every ride you are doing he best for the battery.

10. Does the motor need any maintenance?
There is no maintenance need ed on the Vivax motor, However The manufacturer recommends that the oil in the Gearbox is changed after each 300 hours of use. So if you ride 6 days a week for a year then it will be time fore a oil change. If you do half this it’s twice a year and so-on. There is a lot of cycling to be done between services!

11. What happens if you push on the pedals or resist the motor?
The motor will cut out after a second or two when it senses that the cranks have stopped turning, It is designed to cu out if you have to stop quickly.

12. Can you just let your legs follow the pedals or you can add to the motors power by pedalling a bit harder.
It is a joint effort, you are pedalling and the motor is contributing too if you pedal less hard then you will be in an easier gear and if you are pedalling harder you will be in a higher gear so moving quicker moving through the gears more quickly too, if you are following the pedals you will still be pedalling softly. You will find that you will pedal at a comfortable level for you and as you ride more you will find your legs get stronger.

14. Is it difficult to stop the motor if say I had to stop the motor quickly but did not have time to push the button on the handlebars?
To give you an idea of how much resistance you would have to give to stop the motor, you would have a job to stop the crank from turning by hand, but with your legs it is no problem, The vivax is designed to be stopped by your legs if you want to. When the motor/crank has been stopped from turning for around 1 to 2 seconds the power will cut off automatically and then to restart it you would press the button and off you would go again.

16. Does the Vivax Assist work with Hub gears?
Vivax and they do not recommend use with hub gears - either the Rohloff or Alfine because of the nature of the way you have to change gear i.e. stop pedalling to change. This would mean turning the motor off every time you want to change gear. I personally would prefer not to have to do that but it would be possible but for the ease of use I think the way to go with the Vivax is with Derailleur gears. Derailleur gears save you weight over the hub gear systems as well. Of coarse you can easily change from Derailleur gears to a hub gear system if you really felt that was the way to go later. Good quality Derailleur gears work very well too, one click one gear instantly and smoothly. However i have recently had a customer who refused to give up his Rohloff gears and he tells me he is getting on just fine with the Vivax.

17. When the Vivax is on the cranks are turning, if they are turning too quickly, how do you slow the cadence?
You can alter the cadence easily. You set the cadence when the motor is off and to do it, all you have to do is pedal at the cadence you wish it to be at and hold the on/off button in on the handlebars for a few seconds. generally on the road I have it on a fast cadence and off-road when the going is technical I slow it right down. You will find your sweet spot with it as I have.

18. What is the experience of climbing a hill with the Vivax Assist?
When you are climbing a hill you will stay in the cadence you have set it at previously and change down the gears as you climb, when you reach the top of the hill and it flattens out you climb back up through the gears, if you keep the assistance on, you will pick up speed quicker as you move back up through the gears. Leave it on or switch it off as you wish.

19. How does Hill climbing effect the cadence with the Vivax Assist?
The cadence stays the same if the re is no resistance to the motor, but when you hit a hill then the rpm/cadence will slow down as you start to climb because now the motor has some work to do. As you climb, you can put in the power from your legs as desired, but the vivax will keep seam rolling until you switch it off.


Vivax Assist Kit Prices

Vivax Assist Standard kit including 6.0 Ah battery and charger - £2589
Vivax Assist Water bottle battery kit including 6.0 Ah battery and charger - £2989
Installation of kit into bike £199
Upgrade from 6.0Ah battery to 9 Ah battery + £160

Li-ion manganese Battery (30 volt 6.0 Ah) -  £460
Li-ion manganese Battery (30 volt 9.0 Ah) - £599
Extra Li-ion charger £165 (recharge times- 3hrs for 6Ah bttery, 4.5hrs 9Ah battery)
Li-ion car charger £165
Cane creek Thud buster suspension seat post - £240
Carbon seat post upgrade - £140

Invisible performance water bottle battery upgrade package - £499

More Vivax Assist Info

We also distribute bikes and frames from a company In Austria called Steinbach that supply Vivax compatible frames and bikes. Like us they have also worked together with Gruber for many years now:  
Steinbach Bikes

To see the Vivax assist in action again click on video below.