170mm or 175mm??

[cjs]

I'm about to get a new Shimano XL Crankset for my MTB. My existing Truvativ has a 175mm crank length, any thoughts or opinions on going for a 170mm V 175mm? Most of my riding is XC trails and woods, no huge hill climbs or descents.

Edited by cjs on Monday 28th April 14:52

[pdV6]

Assume you mean LX or XT (almost definitely LX at that price).

Unless you're a real short-arse or have a really low bottom bracket and have undue problems with pedal strikes, just stick with the 175mm.

[cjs]

pdV6 said:

Assume you mean LX or XT (almost definitely LX at that price).

Unless you're a real short-arse or have a really low bottom bracket and have undue problems with pedal strikes, just stick with the 175mm.

Yes I meant LX. No none of the above, I am wondering if a 170mm might suit me better. Is 175mm the "Standard" length?

[neil_bolton]

You'll generally find 175mm easier to use - you don't get the climbing power out of a 170mm as you do a 175mm.

Also, you'll find your cadence maintenance easier on 175mm cranks as you don't spin so quickly overall (although its minimal really).

If you're really worrying, get a 172.55mm if they still do em', just to throw the cat amongst the pigeons


just realised how wanky 'Cadence Maintenance' sounds. God, I mortify myself sometimes.

Edited by neil_bolton on Monday 28th April 15:28

[mat205125]

Unless you have 2 identical bikes side by side to do a Pepsi challenge, you will not notice that they feel significantly different, and in the real world where we all ride non-competitively, the difference really isn't worth worrying about. Go for the 175 to match 99% of the rest of us, and enjoy your riding ... The LX kit is good and strong, and great value for money. I skipped a night on the tiles, and put the funds in to get the XT kit. Does everthing that you can reasonably need, and is perfectly sorted for 99% of riders 99% of the time .... Look the bks too

[pawsmcgraw]

The real difference between crank length is the tip speed of your foot, and the question should be are you a spinner or a masher?For every 2.5mm(1.4%) is equates to a change of tip speed of about 6 rpm.....so if you ride at 90rpm average on 172.5 then the same tip speed on 175 will be 84rpm.
Torque is lost with the shorter crank hence why the default setting for mtb is 175...most people don't spin, most grind slowly and have no benefit only loss by running 170's, unless your very small or very ,very short in the leg.
Work out your average rpm with a simple caydence meter, ride the longest crank you can to match your leg length.175's will do fine for most people

[cjs]

mat205125 said:

Unless you have 2 identical bikes side by side to do a Pepsi challenge, you will not notice that they feel significantly different, and in the real world where we all ride non-competitively, the difference really isn't worth worrying about. Go for the 175 to match 99% of the rest of us, and enjoy your riding ... The LX kit is good and strong, and great value for money. I skipped a night on the tiles, and put the funds in to get the XT kit. Does everthing that you can reasonably need, and is perfectly sorted for 99% of riders 99% of the time .... Look the bks too

Thanks for the advice, I have decided to stick with 175mm cranks. I was going to go for the XT kit but I have to keep my costs down, a few quid extra here and there has pushed up the cost of my rebuild way beyond my original budgets. New tyres, new tubes, new crankset, new chain, tools etc.

[pdV6]

cjs said:

I was going to go for the XT kit but I have to keep my costs down, a few quid extra here and there has pushed up the cost of my rebuild way beyond my original budgets. New tyres, new tubes, new crankset, new chain, tools etc.

Don't worry - the LX still looks nice (not quite as sexy as the XT) and is functionally just as good. I run LX HTII on both my bikes as for £50 a go (at the time) I really couldn't say no, or stretch to £90 each for the XTs.