Singlespeed gearing advice

sgt822

I've had a search of the forum but can't find an answer to my query so here goes (apologies but a newbie when it comes to singlespeed).

I'm considering buying a Genesis day one which is equipped with a shimano 4600 front crank and outer ring removed leaving the 39t as the chainring.

It also has a 18t Shimano SF-MX30 freewheel.

39 x 18 being somewhat different to my only point of reference a specialised langster with 42 x 16 gears. I have a few hills on my commute which were tough with the 42 x 16 but doable.

So my questions are as follows (just in case I "spin out" too easily):-

A) is it possible to replace the 39t standard chainring on a shimano crank with a 42t ? If so who / where can I get one?
a 15t freewheel would appear to give me a comparable gear according to my layman's research. What 15t freewheel would be compatible?
C) do I need a special tool to remove / refit the freewheel?

iPete

A) Yes, a quick google suggests the BCD is 110. You probably also have a 3/32 chain. Worth double checking. This may be OK:
http://www.spacycles.co.uk/products.php ... b0s149p292

There are not many on the market in this size. The Shimano 16t BMX freewheel is easy to come by and cheap, the same as you have now. White industries do a better but much more expensive model.

http://www.chainreactioncycles.com/shim ... p-prod7805

http://www.ebay.co.uk/itm/White-Industr ... 0810617250

D) Yes, something like the Park Tool FR6C.

Have a play with http://www.bikecalc.com/

sgt822

iPete wrote:

A) Yes, a quick google suggests the BCD is 110. You probably also have a 3/32 chain. Worth double checking. This may be OK:
http://www.spacycles.co.uk/products.php ... b0s149p292

There are not many on the market in this size. The Shimano 16t BMX freewheel is easy to come by and cheap, the same as you have now. White industries do a better but much more expensive model.

http://www.chainreactioncycles.com/shim ... p-prod7805

http://www.ebay.co.uk/itm/White-Industr ... 0810617250

D) Yes, something like the Park Tool FR6C.

Have a play with http://www.bikecalc.com/

Cheers buddy. That's perfect. I knew there must be a solution out there somewhere, just didn't know the correct terms. So given my 4600 crankset is a standard rather than compact my google skills suggest a BCD of 130 rather then 110, but looks like spa cycles have that option covered nicely too

Will try the gearing as is, as I expect the wider tyres and weight of the D1 will mean I need a little more than the Langster but I now have the options!

Expect I'll wait for the freewheel to fail (the shimano doesn't seem to be well thought of) before I invest in a white industries replacement.

Spot on thank you!

term1te

I recently replaced a no-name free wheel with a White Industries one. The difference was amazing, best bike upgrade I've ever made. I'm running 42 17 on the single speed which is fine for up to 35 kph and 8% hills. I've got 165mm arms onthe chainset, which help with spinning, but give you less leaverage on the hills. The equivalent gear on my road bike feels easier going up hill with its 172.5mm chainset. Something to watch out for if you are "trying" gear combinations on a regular bike, caught me out and I had to moved from 16 to 17 cog when I was running it fixed.

FatTed

The Oracle
http://sheldonbrown.com/gears/

( go fixed )

wrayste

I run 46 / 18 on my Pearson Touche for commuting around London which I'm pretty happy with but I will probably start experimenting with gearing shortly. So far it's got me up Box and Leith hills fine (and bit of a struggle) and works ok with the light touring when the panniers are full.

I have the Shimano freewheel which I've not had any complaints about other than not being completely round. I have a brilliant Velosolo chain ring (http://velosolo.co.uk/shopcrank.html), the 130 BCD (I have standard SRAM Rival cranks) and use a 3/32" chain (the excellent SRAM PC890).

If I was going to upgrade freewheel then the White Industries offering would be what I would go with.

Back to gearing though, I use BikeCalc (http://www.bikecalc.com/gear_ratios) to play around to see what combinations result in what speeds, cadence, etc.

I try and maximise the teeth because that should mean that the components last slightly longer (i.e. think about going for a 18t freewheel rather than down to something like a 15t).