Mtb to IGH 8 speed conversion

[dutchguylivingintheuk]

So i have a Carrera Crossfire 1 bike, currently it once again has issues with his gears and his wheel hubs are gone. Now i can change this but to be very honest it is'nt worth the investment for me in terms off, for the same money i can be a second hand.
However currently everything has lockdown prices so it's all a bit inflated looking at my other bike that isn't made to go very fast but is reliable as hell(only thing i ever had with it is a puncture because of a large chunck of glass)
So long store short i have the idea in my head of getting an 8 speed nexus wheel and change the rear cassete to an 8 speed fixed gear with a roller brake.
I have found all the information i need about how to mount the rollerbrake an d the special lockrings you need the mount the wheel, the point i have questions about is:
- Can i use the existing shifter or do Nexus hubs have other gear ratio's? (it's currently a 8 speed cassete originally and suntour derailer but i tink i put an shimano on some time ago)
- do i need to remove the old derailer or can i leave it on as chaintensioner and/or to make test runs easyer(as if that's possible i don't have to go the the lbs first to let them shorten my chain)
- i now have 3 rings in front with a front derailer, do i need to convert this to a single ring aswell? (i see it being done quite frequently but nowhere i find if it's really needed or not, i almost never use these chainrings but if it isn't needed it's an extra step out of the way)

 

[tyred]

I done something like this once.

You will need the specific shifter for the hub gear as gear adjustment is absolutely critical on any hub gear.

I used an old steel frame with horizontal drop outs but if you need a chain tensioner there's no particular reason why you couldn't use an old derailleur if you are using a 3/32" chain. If you plan on using the proper 1/8" chain for a hub gear bike it probably will be too wide to run on the jockey wheels.

You could use your existing chainset if the chainline works out, ideally to the middle ring. I doubt you will be that lucky though.

If your chainset has removable rings you can bin the two you don't needs and use shorter bolts or washers to take up the space.

The reason a single speed chainring would better is because you have full teeth with less chance with the chain coming off and it should wear better but you can still use one for derailleur gears. I've done so many times.

 

[Tigerbiten]

Do you need a triple up front with an IHG:- No.
Will it help to have a triple up front with an IHG:- Maybe.
You will be cutting down your range of gears going from a derailleur setup to an IHG setup.
So it's a question of will the 307% range of a Nexus 8 cover what you need taking into account your derailleur setup probably has a 400%-500% range.
So how many gears from your current setup don't you need ??
Can you get away without something like your top gear and your bottom 3 gears.
If not then multiple chainrings can be used to open up the range.
It then depends on the front-back chain line as to how well it works
Can you use a rear derailleur as a chain tensioner:- yes.
I've done it with a Rohloff and twin chainrings setup.
I just fitted longer limit screws so they could be screwed it to lock it on the correct chain line.
But with a single chainring the correct single wheel tensioner is more efficient.

Luck ...........