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Post by dirkpitt74 on Dec 1, 2015 8:44:45 GMT
Guys,
Looking to order a 2x10 SLX groupset for the Mega in the next few days.
Can be had with the following front ring options:
38 24
38 26
40 28
Thinking 38 26 as my current set up is 36 24 and find it a bit under geared on the flat pedally sections and a bit spinny on the ups.
Cassette range on both old set up and SLX is 11 36.
Should I go for 170 or 175 cranks?
Thanks
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Post by jgmu97 on Dec 1, 2015 9:09:16 GMT
It's all personal preference really. Like you said, if you're already spinning out with your current setup, then yeah you should move onto the next one, a 38t chainring will give you abit extra on the flats/downhills
Crank length doesn't really matter, I think the longer they are, the more torque you can get, but the shorter they are, the quicker you'll spin and there's less chance of pedal strikes
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Post by dirkpitt74 on Dec 1, 2015 9:54:27 GMT
Thanks.
Crank length difference of 5mm gives a 2.8% difference in torque (yes - sad I know but I thought I'd see what the difference was!!).
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Post by step on Dec 1, 2015 10:52:05 GMT
Get 172.5 cranks  The 26-38 sounds like a good setup, will depend though on your rear cassette. Im running 26-36 but then an 11-40 rear. if your spinning out on flats then a bigger finial drive as it were would be better so the 38T but hills you could probably get away with an 11-36 cassette. |
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Post by Jan on Dec 1, 2015 11:44:18 GMT
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Post by Jan on Dec 1, 2015 11:46:52 GMT
I'm sure crank arm length should be determined by your height/leg length, hence why kids bikes have shorter arms.
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Post by glynnsixo on Dec 1, 2015 16:07:58 GMT
i have 24-38 and 11-36 on the in-bred. feels good for riding the ups and downs of the peak district. just to add im also still happy with my 3x9 on the mega. im old fashioned like that iv tried 175mm and 170mm crank length and can tell absolutey no difference between them |
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Post by Jan on Dec 1, 2015 17:38:18 GMT
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Post by andy4d on Dec 5, 2015 21:03:08 GMT
I thought crank length was down to your height, 170 for short arses and 175 for normal, but maybe not. I know nothing.
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Post by dirkpitt74 on Dec 10, 2015 10:55:09 GMT
Thanks for the info guys.
Another question though - rear mech cage length.
Have read a couple of articles and I'm now confused.
I'm planning on running 2x10 with 28/36 front and 11-36 rear.
One article suggests medium cage where the other says long.
Found this formula for calculating capacity:
T = (big front + big rear) - (small front + small rear)
With the above combo it works out at 33 teeth.
Shimano spec for the mech is:
Medium Cage 35T
Long Cage 43T
So based on the above I could use a medium cage.
But if I changed any of the ratios though (i.e. went with a 40T expander on the back) I'd need to go long cage.
Do I need to take into account chain growth as it'll be for the Mega?
No price difference between the 2, just want to order the right one.
Confused!
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Post by roundie1981 on Dec 10, 2015 12:06:33 GMT
Dont think it makes too much of a difference to be honest mate, you could just get the long one and that'd do for both situations, but you would get away with a medium too. Medium would be better as it'll be more out of the way when out riding.
Ratios wise I've used a short zee mech and a 40t expander and it worked spot on. So wouldn't read to much into it, chain length is probably the biggest thing to get right.
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Post by dirkpitt74 on Dec 10, 2015 12:19:18 GMT
Thanks. Have realise my calc is out too - DOH! Front rings will be 38/26 - so that puts it at 37T. So might just go with the long cage.
Chain length was going to be my next question!
So - how do you work that out?
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Post by roundie1981 on Dec 10, 2015 12:23:20 GMT
Big to big plus 2 links is the standard rule of thumb mate
Copied from another site for full suss
You forgot to mention that on a full suspension bike you need to fully compress the rear shock before checking the chain length, because when you compress the rear shock, the chain will grow just a bit more, so that's the point were you need to check the length of the chain, before you cut
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Post by step on Dec 10, 2015 15:22:11 GMT
Big to big plus 2 links is the standard rule of thumb mate Copied from another site for full suss You forgot to mention that on a full suspension bike you need to fully compress the rear shock before checking the chain length, because when you compress the rear shock, the chain will grow just a bit more, so that's the point were you need to check the length of the chain, before you cut This is why I had to go with a long mech, worst case 36T - 40T comedy my chain length is 114 links now! |
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Post by dirkpitt74 on Dec 10, 2015 19:34:09 GMT
Thanks chaps.
Dumb question again.
I take it the chain is threaded through the rear mech?
Is it worth just letting the air out of the shock as a 'worst case' for chain growth?
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Post by Deleted on Dec 10, 2015 19:39:54 GMT
That's how I did it Chris.
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Post by Deleted on Dec 10, 2015 20:50:01 GMT
I followed this guys advise when doing my 1x11 on the Titus
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Post by dirkpitt74 on Dec 10, 2015 22:15:38 GMT
Thanks Bob!
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Post by Rlo80 on Dec 20, 2015 11:38:43 GMT
I was using 26-38 rings with 11-36 cassette. Found it spot on for everything. You need long mech for that. Chain is always better to buy bigger and then remove links as adequate. The issue is when some chains are only available in 114...but usually fine anyway.
The measurement from the floor to your crotch is usually what determines the crank length...I had 170 and 175 before...can't feel a difference! One thing im doing on the new crank is to put some Race Face crank boots/shoes to avoid damaging the arms on rocks...
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Post by dirkpitt74 on Dec 20, 2015 15:19:33 GMT
Thank rlo80 - think I'll give the 28-36 a go. Reading up I fall between 170 and 175 lol. Will probably go with 170 for a tiny bit more ground clearance and also I'm slighly short legged long bodied lol.
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Post by Rlo80 on Dec 20, 2015 22:43:54 GMT
Thank rlo80 - think I'll give the 28-36 a go. Reading up I fall between 170 and 175 lol. Will probably go with 170 for a tiny bit more ground clearance and also I'm slighly short legged long bodied lol. You won't regret it I don't think...Me too at 172.5...which I couldn't get and since the 170 version at the time was considerably cheaper than 175, I went for that. On the new built I went 175 because with less gears a bit extra torque will probably help (if you can even notice that is!)...like I said before, some crank shoes for 7 quid might be a worthy investment. Good luck |
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Post by dirkpitt74 on Dec 21, 2015 6:58:44 GMT
Cheers.
Do you have a link to the crank sleeves?
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Post by Rlo80 on Dec 21, 2015 9:51:18 GMT
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Post by Jan on Dec 21, 2015 11:22:08 GMT
You can get the crank arm boots off eBay for just over a pound. I have them on a couple of my bikes.
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Post by dirkpitt74 on Dec 21, 2015 15:53:42 GMT
Thanks chaps.
Will order a pair.
Can you get anything that covers tbe whole crank arm to stop heel rub?
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