Sprocket and speed advice

Hello all.

I'm looking for advice on how to get a bit more speed from my bike (which has a dongle). I have a rear hub Shimano Alfine , 8-Speed, It feels like I need higher gears as pedalling becomes ineffective at about 19mph, pedalling is stop and start. Is a new sprocket the answer? Also is the sprocket inside the bosch motor? Would it be costly to have fitted?

Any thoughts on this would be really appreciated

size wise you can go up to 22t on the front and there about 15 quid

http://www.pro-cycling-golla.de/E-Bike_Ersatzteile___Hersteller___Antriebe/Bosch_Active___Performance___CX_Line/Kassetten___Kettenblaetter___Verschlussringe.html

Thank you soundwave, This vid is really helpful.

To clarify would I need only one sprocket in the front/in the motor?

Would it be necessary to get a new chain?

You can also go down to a 16 tooth on the rear, you just need to take a link out of your chain, although it also depends on how your chain is tensioned on your bike.

I've had mine as high as pedalling to 38 mph on my Nexus 8, but I'm on a classic Bosch motor.

out of stock here http://www.wiggle.co.uk/shimano-sprocket-for-nexus-8/?lang=en&curr=GBP&dest=1&utm_source=google&utm_term=DC&utm_campaign=UK_Manufacturer_DC_Shimano&utm_medium=cpc&utm_content=mkwid|sxXF5pZob_dc|pcrid|77081344872|pkw|+shimano%20+sprocket%20+nexus%20+8|pmt|b|prd|&product_id=

This is all useful information, much appreciated - from what I gather either the rear or the front could be adjusted with a new sprocket?

I have Hub gears would this make it more difficult to do?

Also is there anyway to change the sprocket without changing the chain?

if the chain is to short you will snap it tho best get used to changing them as they wear out lot faster than a normal bike.

front sprocket will be the most simple to change and take 5 mins.

id say any more than 3t from what you have and will need to add a link or 2 to the chain thats all and simple enough if you have the tools that is.

This is all useful information, much appreciated - from what I gather either the rear or the front could be adjusted with a new sprocket?

I have Hub gears would this make it more difficult to do?

Also is there anyway to change the sprocket without changing the chain?

How many teeth does your rear sprocket currently have?

Yes either front or rear sprocket change, or even both, I'd be tempted to go bigger on the front first, purely because of the unusual chain-line the Bosch motor brings.

The sprocket is fairly easy to change, it is held on by a circlip.

Your chain may be reused, but I'd probably take the opportunity to fit a better quality one, something like this one http://www.wiggle.co.uk/kmc-x1-rohloff-compatible-chain/?sku=5360447194

There are loads of videos showing removal of the sprocket

This is all very helpful indeed.

I'm wondering how much gain there is for each tooth that is added, also if there is a climbing loss. I'm guessing that my bike has 14 at the front and this is not optimum, maybe 16 or 18 is good? (would prefer not to change the chain)

would a make like this be compatible? https://www.amazon.co.uk/Sprockets-Bosch-Bike-Motor-Teeth/dp/B00NZ51HK4/ref=pd_sim_200_2?ie=UTF8&dpID=31%2BbZZAfhgL&dpSrc=sims&preST=_AC_UL160_SR149%2C160_&psc=1&refRID=2G7SNT9PXGJ69PGS1HCD

This is the bike I have http://www.allterraincycles.co.uk/Cube-SUV-Hybrid-Pro-500-Electric-275-Urban-Bike-2016

connex are the best you can get i have 16t on mine and spin out around 29mph with 19t it got me to dongle cut off speed 35mph.

you need the socket or spanner to remove the lock ring tho.

I have 46 or 48 on the front with 16 on the rear with a 26' wheel.

I haven't spun out at 35mph and I can still climb 6% hill in third.

This is all very helpful indeed.

 

I'm wondering how much gain there is for each tooth that is added, also if there is a climbing loss. I'm guessing that my bike has 14 at the front and this is not optimum, maybe 16 or 18 is good? (would prefer not to change the chain)

 

would a make like this be compatible? https://www.amazon.co.uk/Sprockets-Bosch-Bike-Motor-Teeth/dp/B00NZ51HK4/ref=pd_sim_200_2?ie=UTF8&dpID=31+bZZAfhgL&dpSrc=sims&preST=_AC_UL160_SR149,160_&psc=1&refRID=2G7SNT9PXGJ69PGS1HCD

 

This is the bike I have http://www.allterraincycles.co.uk/Cube-SUV-Hybrid-Pro-500-Electric-275-Urban-Bike-2016

From the link I see your bike has a 17T front and 23T rear sprocket. If it was my bike I'd try a 16T rear first. Obviously your whole gear range moves higher, so your lowest gear isn't as low, but the motor allows you to get away with a high first gear anyway.

You could have a play with a gear ratio calculator, but times the size of the front sprocket by 2.5 because its not set up to work out the internal Bosch gearing. so put your front sprocket as 42 teeth.

http://sheldonbrown.com/gear-calc.html

Edited July 7, 20169 yr by Artstu

Chain length/tension is often a problem when changing the gearing on a hub gear bike.

Looks like you bike has sliding rear drop outs, which you loosen by undoing the two allen bolts on each chain stay.

No mudguards means you can move the wheel as far as the slots will allow.

Another option is to fit a chain tensioner, which then gives you lots of adjustment not least because the chain can be routed above or below the pulley.

Chain length is also much less critical because the tensioner can take up a lot of slack.

https://www.evanscycles.com/shimano-alfine-s510-chain-tensioner-EV172307?esvt=1502-GOUKE324376&esvq=&esvadt=999999-0-35300-1&esvcrea=61235636936&esvplace=&esvd=c&esvo=EV172307-NA-SVR&esvaid=50080&gclid=CO_snuWD4c0CFQaNGwodrm4J0g

Another option is to fit a chain tensioner, which then gives you lots of adjustment not least because the chain can be routed above or below the pulley.

Chain length is also much less critical because the tensioner can take up a lot of slack.

Exactly what i had to do when fitting the Alfine 8, chain tensioner needed as i have vertical dropouts, about £15 or so. Also changed the sprocket from 20t to 18t as it was maxxing out at 20mph, may go 16t, see how it deals with the hills.

Edited July 7, 20169 yr by tommie

From the link I see your bike has a 17T front and 23T rear sprocket. If it was my bike I'd try a 16T rear first. Obviously your whole gear range moves higher, so your lowest gear isn't as low, but the motor allows you to get away with a high first gear anyway.

 

You could have a play with a gear ratio calculator, but times the size of the front sprocket by 2.5 because its not set up to work out the internal Bosch gearing. so put your front sprocket as 42 teeth.

 

 

http://sheldonbrown.com/gear-calc.html

Thanks for all the info guys

I ordered this

https://www.amazon.co.uk/gp/product/B00NZ51JB6/ref=oh_aui_search_detailpage?ie=UTF8&psc=1 and asked the bike shop to put it on the back.

When I returned to the shop they had put it on the front and they said it was not compatible on the back and I need a different type of sprocket, any idea if that is the case?

(previously it was a 16 at the front) With the 18 teeth on the front now it has added about 2-3 MPH - of course now it would be nice to have a bit more speed, so any idea how to optimise this, should I focus on the rear sprocket?

why did they say its not compatible on the rear? its just a bigger sprocket unless its an off set one for some bikes frame design.

go faster then cheapest option would be a bigger front sprocket you can go up to 22t size wise.

This is the rear sprocket, as in the video and link above, 16 is as small as you can go, see how it goes with one, and if it isn't enough think about a bigger front sprocket

http://www.wiggle.co.uk/shimano-sprocket-for-nexus-8/

Edit, Forgetting you still have a 23 rear, the jump to 16 will be a big one.

Edited August 18, 20169 yr by Artstu

why did they say its not compatible on the rear? its just a bigger sprocket unless its an off set one for some bikes frame design.

 

go faster then cheapest option would be a bigger front sprocket you can go up to 22t size wise.

Come on SW you should know the sprocket is a front one, you've got a new Bosch haven't you?

you dont want 22t on the rear lol i have 10 on the smallest on the rear but have a cassette.

Like comparing apples and oranges, stop confusing the issue.

more speed bigger front sprocket or smaller rear one

how fast do you want to go tho?

more speed bigger front sprocket or smaller rear one

 

how fast do you want to go tho?

Well the bike has nine gears and three of them I never use - even for the highest hill - they are redundant....I was maxing out on 23mph on the flat today and Intuiva up signal was pointing up 'asking for more gear'. I would love to give two or three upward gear changes. i'm not sure I would really go this far but 30 would be really interesting (if the motor has the capacity it seems like a waste to not use it if necersary). SW you say you are getting 35 I guess you have to pound the pedals aswell?...that is an incredible speed eitherway..!

Well the bike has nine gears

Ah so it was you who got the Friday special hub where they sneaked in an extra gear :)

anything over 25 then i have to start putting effort in i could not keep it at 35 for very long tbh plus it nukes the batt.

i have 18t at front and 10t at the rear.