i've been thinking about whether or not to convert my new 29er to a 1x9 set-up and i stumbled upon some maths-based potential issues which i'm bringing up here to either be confirmed or poo-poo'd.

the idea is this.....

if i'm running a 1x9 set-up with, for example, a 32T chainring up front and a 9spd 12-36T cassette at the rear then i get a certain set of gear ratios.

but.....i'm forgetting to calculate the circumference of the wheel itself.

surely there'd be a noticeable difference in running this same gearing ratio on both a 26er and a 29er - no???

the logic seems to me to work: moving the same amount of weight (bike and rider) over different distances (the circumference of the wheel) using the same (for example 32T front and 16T rear = 2:1 ratio) would require increased energy input for a 29er.

sooo.....is this:

a) something that is common knowledge and i'm just catching up
b) nonsense and i'm overlooking something obvious
c) true and i'm some kind of geometrical genius

what do we think....?

Afternoon ... you are correct that there is a difference in gearing when using 26" and 29" wheels. If we were talking singlespeed (rather than 1x9) then the general thought is ... a difference of 2T. 32x16 with 26" would be roughly the same as 32x18 on a 29er.

I do notice the difference on a singlspeed but don't really notice it with gears. Your 36t rear should pretty much cover you, although it may now feel like a 34t rear

Leg better?

good good.

glad my logic hasn't failed me.

i think i'll try the set-up as it is on my 26" bike and then change things if i notice that it's too hard (when heavily laden on steep climbs).

and.....no, the knee's still giving me hassle.

i popped out on the 29er yesterday and i still can't put any power down without it twinging - it's crap!

i'm off back to France at the weekend and have a mini bike/bivi/bike trip planned and so we'll see how it holds up (as i'll be damned if i'm cancelling).

Google 'gear inches'. There are more wheel sizes to get your head around than 29 & 26"

I was hoping there would be a decent Android app. but there isn't one yet.

holy crap!

some people (this sheldon brown fella for example) seem to have a lot of time on their hands.

will wade through all of it when i get a minute - good stuff.

thanks, gairy.

You've never heard of Sheldon Brown?

Ahh ... Sheldon Brown (RIP), a true eccentric of cycling. He must have been responsable for setting thousands of folk on the road the oddness

Ian wrote:You've never heard of Sheldon Brown?

nope - but.....now that i think about it i'm sure i've come across his site before (when looking up obscure bike figures) but don't know anything about him.

seems to know his stuff!

i blame/ thank sheldon for setting me on to the one-speed path of the righteous. :D

i built up a SS mtb in my final year of school with only sheldons site as a reference. 6 years later i spent a good proportion of my final year at uni converting a 1989 raleigh into a fixed wheel with only sheldons site as a reference.

The cycling world is poorer without him.

Amen to that..