Gear ratios ? 29 er wheels

[tunariaan]

Morning guys

i currently ride 34x20 but its a bit hard on climbs like Montagu

 

Would a 32x18 be any better-

and how does 32x18 compare to 34x20

Im playing around to get the right ratio for Karoo to coast.

thx

[Grease_Monkey]

32/18 = 1.778 rotations of the wheel.

34/20 = 1.700 rotations of the wheel.

 

So a 32/18 will be even harder on the hills than 34/20.

 

I would suggest playing around with either the chainring or cog, not both. Try a 32/20 (1.6 ratio). If that is too easy then you can play around with the cog - you can get them at a very inexpensive price from Rapide.

 

32/16 = 2.00 ratio

32/17 = 1.88 ratio

32/18 = 1.77 ratio

32/19 = 1.68 ratio

32/20 = 1.60 ratio

 

The ideal ratio for most guys I know that ride SS is 32/16 or 32/17, but both of those are harder than your current ratio of 34/20.

 

The move to a 32t chainring will be better for you because it gives you slightly more freedom in your ratio choices. As far as I know you don't really get bigger cogs than 20t, so that makes an easier gear hard to find. If you have the 32t with a 20t on the rear I doubt you will ever need easier.

 

EDIT: Remember, the bigger the wheel the harder it is to get it to do one revolution. So the same ratio on a 26er pedals easier than a 27.5" which pedals easier than a 29er. But, that's not really relevant to you because you are not playing around with wheel size, that's the one variable in the equation that stays the same for you.

Edited September 6, 2017 by Grease_Monkey

[Letum911]

I use this site as a reference: http://surlybikes.com/info_hole/spew/spew_single-speed_gearing_101

 

and then use gear inches to calculate the resistance:

Gear inch = (Diameter of drive wheel in inches) x (# of chain ring teeth)
                                                # of cog teeth

 

if I'm correct the 34/20 setup is actually a bit lighter that 32/18.

29" x 34

20              = 49.3" travel per rotation

 

29" x 32

18              = 51.55" travel per rotation

[LeoKnight]

Can also try this website

 

http://gears.mtbcrosscountry.com/#26I1I1

 

They give you what is the estimated speed at the difference cadence 

 

Speed (km/h)  Cadence:  60       80      100      120

Highest gear                    26.0     34.6   43.3     51.9

Lowest gear                      5.4        7.2      9.0    10.8

[Iron]

Without getting into to much tech ( im to doff for it ) 

 

my magic gear was 33-18 ( std blade not narrow wide ) , trained on it raced multiple races on it , sub 3 road race at 94.7 it just works well on a 29er .

 

my 2 cents 

[Jewbacca]

Riaan, don't listen to the guys in Jo'burg, they don't have any mountains and ride ridiculous ratios.

 

32/19 is a magic gear. I sort of settled on it and it stayed. For Cape Town, Lesotho, Freedom Challenge etc.. It is light enough to climb most things and good enough to keep your speed up on descents... you will always be buggered on the flats!

 

Never mind fancy maths, if you drop to a 32 oval and get a 19 tooth rear cog you won't regret it.

 

(But if you apply basic maths while you play 32/20 = 1.6.. 32/19 = 1.68 and 34/20 = 1.7)

 

So it will be only very marginally easier than your current set up.. maybe the oval will help.... that or a cup of cement tea

[madbradd]

This gives you a good idea of all the various ratios with different cassette options. Can mail the native file if you want to make any edits. Colour Coding is just for ease of comparing on my current ratios.

 

 

Edit: Note this is just the general ratios. Native file does wheel and tyre size as well.

Edited September 6, 2017 by madbradd

[Letum911]

Riaan, don't listen to the guys in Jo'burg, they don't have any mountains and ride ridiculous ratios.

 

 

 

So it will be only very marginally easier than your current set up.. maybe the oval will help.... that or a cup of cement tea

We're just stronger over here

 

But what difference does the oval make?

[tunariaan]

Might try the 32x19

We got lost of climbimg here..a average ride off 40km wil give you about 500 to 700m of climbimg

I raced Attakwas on 34x20 maybe i must just ride more????

[Grease_Monkey]

If you do go oval, I would recommend using a tensioner. I used oval for a while with no tensioner and it was just horrible IMO.

[Jinga]

I start with 32-18 but not happy with top end.

Tried 32-16 better top end but started getting knee pain.

Now running Oval 32-16 and  happy with top end and knee pain disappeared.

 

Good Luck

[Hairy]

for CT riding and including Table Mountain, 32x20t was the perfect gearing for me.

[tunariaan]

its going to be 34x20

Thanks guys

[Hairy]

its going to be 34x20

Thanks guys

34x20t @ the std SS gear set ups of Sitting, Standing and Walking!

[tunariaan]

decided to go 34x18 on Friday,

It was def the right gear ratio.

Had a blast , well done to the other okes

[Francis1]

I run a 34 oval x 16 or 18. Did the baviaans this year and stayed on the 34 oval x16. Paid the price on the climbs but still finished in 13:30.

 

Tried a 15 but just toooooo much hard work.