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Currently have a Double chainring and bash guard, biggest chainring being 33 Tooth 4 bolt type, im thinking of changing to 38 tooth just to maybe gain a bit more top end speed, ? Has anyone done this ? and is it worth it ? as i will also have to buy a bigger bash guard. Cant Quite make up my mind yet.

Cheers

Yes it can be done, not sure how much more top speed it will give you but will stop you spinning out so quickly.
Black spire do a bash guard up to 40t compatible.
You will probably have to adjust the front mech too by lifting it up, i think 2mm per extra tooth? so that would be 10mm.
Then you might want to replace the granny ring to something a bit bigger. What size granny ring you running if you big ring is 33T
I put a 40t/26t on mine but have a 11-36 cassette to give me a low enough gear for hills

Hi Carl

Granny ring is 23 dunno if it will need replacing wot do you reckon ? (im not even sure about changing the 33 tooth yet just trying to get some feedback to see if it is worth it)

Your quite low geared, have you just taken the outer ring off to go 2x10/9? Or you have a 11-32 cassette to give you a slightly higher ratio for when your in the low gears?

33/23 is low i would go 38/26 or as i have done 40/26 or you could go 40/28. what size is your cassette?

Hi Carl
rear cassette is 11/34

Steve

Thats ok Can still change to 24 or 26 granny ring or 38 or 40 big ring if you wanted to but be slightly more effort going up hill when your in the lowest cassette gear

Yeah, I was wondering what the top end difference would be on a 38 ?

Sheldons your man steve

im here

I did have a quick look at his site....

Quite easy i will do it for you

whats your crank arm length and 10 or 9 speed

It's 7'' centre to centre 9 speed

Okay it looks like this I based it on 175mm crank arms



Cassette---- chain rings
Gears---------- 33--- 23----------- speed (MPH) based on a cadence of 60 (RPM

11--------------- 5.3--- 3.7------------ 15.3--- 10.6 mph
12--------------- 4.9--- 3.4------------ 14.0--- 9.7
14--------------- 4.2--- 2.9------------ 12.0--- 8.4
16--------------- 3.7--- 2.6------------ 10.5--- 7.3
18--------------- 3.3--- 2.3------------- 9.3--- 6.5
21--------------- 2.8--- 1.9------------- 8.0--- 5.6
24--------------- 2.4--- 1.7------------- 7.0--- 4.9
28--------------- 2.1--- 1.5------------- 6.0--- 4.2
32--------------- 1.8--- 1.3------------- 5.2--- 3.7

now if you change the big ring to a 38T There is quite a difference in ratio's. Non on the small ring as its the same.

--------------------38--- 23

11--------------- 6.1--- 3.7----------- 17.6 mph 23T same as above
12--------------- 5.6--- 3.4----------- 16.1
14--------------- 4.8--- 2.9----------- 13.8
16--------------- 4.2--- 2.9----------- 12.1
18--------------- 3.7--- 2.3----------- 10.7
21--------------- 3.2--- 1.9------------ 9.2
24--------------- 2.8--- 1.7------------ 8.1
28--------------- 2.4--- 1.5------------ 6.9
32--------------- 2.1--- 1.3------------ 6.0

Difference of 2.3 mph at 60 rpm in top gear

I just calculated mine, I have 40T 26T Rings 11-36 10 speed cassette

My top speed at 60 rpm is 18.5 mph in top gear
5.7 mph in 40T ring & 36T gear
12.0 mph in 26T ring & 11T gear
3.7 mph in 26T ring & 36 T gear

I get slightly higher top end (3.2mph based on your present gearing and 0.9mph if you put on a 38T ring) but both get 3.7 mph in lowest gear, based on 60 rpm.

Thanks For that Carl, not just a pretty face are ya

now i will decide to do it or not !

So they say