ive owned this bike from new 9 months ago,on the whole im very pleased with it,ive found i only use 5th to 8th gear even up hills,there for im thinking of ether changing the sprocket on the shimano nexus back wheel its 21 teeth now,so am thinking of going down to 16 teeth so im able to make use of all the gears,and maybe wont run out of pedal power at 15 mph,im unsure as to weather change motor sprocket or chain wheel to get what i want ,any advice would be greatly received duke
kalkhoff agutta
- Thread starter duke
- Start date
Dropping to a 16 tooth rear sprocket would increase the assist speed to about 20 mph in theory, but more like 18 mph in practice. The range would suffer though, since current would be used over a wider range of road speeds.
That's the only change you need if you are happy with everything but the 15 mph cutoff. Changing the motor sprocket and/or chainwheel could result in your pedalling speed (cadence) being changed, possibly to much faster with some combinations. Just changing the rear sprocket avoids that risk.
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That's the only change you need if you are happy with everything but the 15 mph cutoff. Changing the motor sprocket and/or chainwheel could result in your pedalling speed (cadence) being changed, possibly to much faster with some combinations. Just changing the rear sprocket avoids that risk.
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If you change to an 18 tooth rear sprocket it will have the effect of almost exactly moving all the gears up one. So the new 1st will become almost the same as 2nd is now at 30.5” instead of your current 2nd of 32”, and 8th will become 93.7” instead of the current 80.2”. So any intermediate gear you currently use you just need to use the next one down instead.
Personally I would not go below an 18 but if you have very few steep hills you might want to. It won’t affect the cut out speed though. That’s regulated separately by the software and the magnet on the back wheel. But a 93.7” top gear would give 25mph at a cadence of 90rpm. In practice you aren’t going to be doing that on the flat anyway unless you’re a strong rider, and if you’re going downhill you won’t need to be pedalling. A more usable 20mph is a comfortable 71rpm at the cranks.
If you want to override the rear wheel magnet and software speed restriction, you'll find how to do that on this link
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You don't say which Agattu you have, but I'm afraid this mod will be complicated.
If it's a belt drive it may not even be possible to change the sprockets.
Assuming it has a chain, the chain will need to be lengthened or shortened, depending which cog you change.
You may also struggle to get the correct tension.
There is - depending on the bike model - a little adjustment in the drop outs.
But that's often not as much as it appears because the tyre fouls the mudguard before all the adjustment space in the drop out slots is used.
The solution is a chain tensioner, assuming one will fit which it probably will.
Time to dust off the rear hub pic of my Rose:
If it's a belt drive it may not even be possible to change the sprockets.
Assuming it has a chain, the chain will need to be lengthened or shortened, depending which cog you change.
You may also struggle to get the correct tension.
There is - depending on the bike model - a little adjustment in the drop outs.
But that's often not as much as it appears because the tyre fouls the mudguard before all the adjustment space in the drop out slots is used.
The solution is a chain tensioner, assuming one will fit which it probably will.
Time to dust off the rear hub pic of my Rose:
Definitely the sprocket on the Nexus hub. Your Agutta should be providing some assistance up to approx. 17 MPH if you have the Impulse 2 drive. Like you, out of the box I found my Tasman Impulse 8HS to be undergeared and so fitted a 19T which I can now pedal at around 22 MPH on the flat. Of course the motor assistance still only provides help up to 17 MPH. I chose a 19T as I live in hilly South Wales and tend to use the Eco setting most of the time. If you have the same drive system as me I would agree that a 18T seems the best choice. A 16T seems overkill unless you pedal slowly.If however you have a belt drive you may have a problem. I'm think the current belt bikes have vertical drop outs so you would need a different belt along with a different sprocket (assuming you can buy one). Of course they may have a belt tensioning device which I am unaware of.
many thanks for all your help and advice,my agutta has a chain drive ,i think the central moter is the impulse 8 bosh,i live in brighton sussex whitch is very hilly,i will get an 18 tooth rear sproket,im very impressed with the chain tenshioner,as dispite re tenshioning chain it soon goes slack again,when i got the bike the chain had no movement what so ever,i felt this was to tight,can anyone recomend a chain tenshioner,can i get 1 that mounts under rear wheel nut ,
many thanks for the link,cant risk the dongel untill my warrenty runs out ,my pick up is mounted inside chain stay on a lug by bolt through centre of it ,was thinking of of moving magnet ,not sure this would have any noticeable effect,i looked at dongle what put me off was that the wires had to be crimped onto bike wireing,so if a fault devoloped im sure the first thing the shop would do was to carefully look for signs of where crimps cut into wireas im sure they are well aware of this,even so i was sorely tempted
http://en.hollandbikeshop.com/branded-bicycle-parts/batavus-bicycle-parts/batavus-chain-tensioner/batavus-chain-tensioner-45mm-bolt-30mm/
The problem with this design is that the extra power from the motor and the cyclist’s input pulls the chain forward in the dropouts on the drive side. Probably why they changed the dropouts when they went to belt drive. There have been a few threads about it. I use one 60 mm Batavus chain pull on the drive side. One is all you need, but two makes adjustment easier though. It’s impossible to keep chain tension otherwise even tightening it up to the torque limits.
A Baddass dongle is the way to go - they now have one for Kalkhoffs.
No wires, just clips on.
https://www.badassebikes.com/en/a-107/
When you change the sprocket you will probably need to lengthen the chain.
If, when everything goes back together, you can set the tension in the drop outs without the tyre fouling the mudguard, the Batavus tensioner will do the job.
The snag with lengthening - or shortening - chains is you can only do it an inch at a time, which can rather swamp the available adjustment in the drop outs.
You may have to fit a Batavus tensioner to locate the axle, and an Alfine tensioner - as on my bike above - to tension the chain.
No wires, just clips on.
https://www.badassebikes.com/en/a-107/
When you change the sprocket you will probably need to lengthen the chain.
If, when everything goes back together, you can set the tension in the drop outs without the tyre fouling the mudguard, the Batavus tensioner will do the job.
The snag with lengthening - or shortening - chains is you can only do it an inch at a time, which can rather swamp the available adjustment in the drop outs.
You may have to fit a Batavus tensioner to locate the axle, and an Alfine tensioner - as on my bike above - to tension the chain.
Yes, the chain pull will work fine - better than the Alfine tensioner in this application because the axle cannot move.
But in the case of the OP, it depends on where in the drop out the correct tension is following the sprocket and chain length change.
As I said, it can be frustrating if, to get the right tension, you need to pull the axle back further than the drop out - or clearance elsewhere - will allow.
The option then would be to add the Alfine tensioner, or use a queer thing called a half link chain which allows finer adjustment of chain length.
https://www.google.com/search?q=half+link+chain&ie=utf-8&oe=utf-8
Yes, I wrote that and then deleted it because I hadn’t read the point about the dropout position. Plenty of people have put 18 T sprockets on these bikes though, and I haven’t read about anyone needing a pulley tensioner. So there’s probably enough room in the dropouts to get it right. I was going to put a 18 T on mine and might still get round to it. Which is why I worked out the gearing. But where I live it’s all uphill and downhill with almost no flat at all. So I haven’t bothered yet.
My Rose has near balloon tyres which leave very little clearance in the mudguard.
That means the sliding adjustment in the drop outs is not as much as it appears.
The Alfine 11 hub does seem to like a bit of tension, so I may have needed a pulley tensioner even had I not changed the sprockets.
The tensioner does make it easy to dismount the chain when taking the wheel out.
But you need three hands to put it all back together again.
That means the sliding adjustment in the drop outs is not as much as it appears.
The Alfine 11 hub does seem to like a bit of tension, so I may have needed a pulley tensioner even had I not changed the sprockets.
The tensioner does make it easy to dismount the chain when taking the wheel out.
But you need three hands to put it all back together again.
many thanks for this useful advice,im getting the chain tenshioner ,i am sure this will cure my lose chain problem,ive got an 18 tooth rear sprocket winging its way to me,keep going back to baddass link for a look !! i have also got to get some sort of head camera ,as over these last weeks ive had a few near misses from car drivers cutting across cycle path without indercating ,im lucky i have hydrolic brakes,i think a large percentage of car drivers have never been on two wheels so they are oblivious to us,perhaps before you can obtain a licence you must use a bike of some sort for at least a month on the road ,
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