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Discussion Starter · #1 ·
I have a new Mach 5.7 and my knee is a bit forward of the pedal axle with my seat as far back as possible.

Which would you recommend adjusting first? Longer cranks or a setback seat post?

I'm 6'1" riding a large frame.

Thanks!
 

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I have a new Mach 5.7 and my knee is a bit forward of the pedal axle with my seat as far back as possible.

Which would you recommend adjusting first? Longer cranks or a setback seat post?

I'm 6'1" riding a large frame.

Thanks!
Hmm.....with a ST angle of 71.5 degrees or less, most people wouldn't need a setback seat post, is your seat high enough? Your seat position should be relative to the BB in order to generate the best pedal stroke. If you need to get further back then I would suggest a setback seat post. Longer cranks would cause more pedal strikes. But, maybe you should look at getting a pro fit done.
 

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Discussion Starter · #3 ·
Yeah my seat was high enough when I measured. I'm going to run a setback post for my ride tomorrow and see how it feels.

Good point about longer cranks. I had a chance to look at the cranks that came equipped and they are 175mm which are pretty long to begin with (I think the longest shimano xt is 180mm)

Thanks for the input.
 

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I was thinking I would like a set forward seatpost... I had a set back post on my Mach 5 but found it really hindered climbing. I have a zero offset Thomson now and the Geo is much better.

Raise your seat or put a longer stem or wider bar on IMHO.

Sent from my Nexus S using Tapatalk
 

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Discussion Starter · #5 ·
After a few rides with the setback post my climbing is definitely weaker. I'll ride with the zero offset post for a few rides again to compare. It could be the first time I measured my seat was a little low.
 

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Well, remember, any new position will change what muscles you are using, and while it might be new it could be 'new and better' or 'new and worse' :). So just because you are weaker, that isn't necessarily bad for now.

Are you measuring kops by the area under the kneecap? Lots of people do it wrong by measuring from the part of the knee that is most forward. It should be measures by the area under the kneecap.

I personally am in a road bike position at the top of my adjustable seat post, put there by a precise bike fit process, am 6' 0' on a large Mach 5 frame, and have the seat all the way forward to the limit lines. I am using a Joplin 4-inch post, which has no forward or backwards tilt. So, it does seem odd that you need to go back more, I probably have 2 inches maybe 3 that I could move the seat backwards!

The bike may be too small by just a bit, or we all have different ratios of femur to body or femur to calf length, so there might be something funny going on with body ratios. I have something slightly funny going on myself, to get in the correct position my seats are often slightly more forward than average.

Is a high-end bike fitting place doing this for you? It is very worth paying 50 or even 100 bucks for a bike fit if you are doing long rides (4-6+) or are competitive or even if you just want to really really make sure you don't get knee injuries and want the best fit.

So, make sure to measure under the patella (kneecap). Along the lines of what the other person said, is your leg basically straight, but you can still put it there, if you put your heel on the pedal by the clip while sitting? That is one measure (really various angles should be checked) that you are high enough for road position. Higher in general puts you farther back, that is why they were wondering if you are high enough and I also want to make sure of the same thing.

Also, I've talked to some people who really know what they are doing, and if you are doing long rides and care about how fast you are going, and work on your rpm for example (keeping it high) then a smaller crank arm length can be better given 2 similar lengths. Longer is more leverage, but slows RPM. So if you do shorter rides, super steep kinds of things, almost trials style in difficulty then the longer crank arm is great, but if you are doing a 4 - 6 hr ride and want the best time then high rpm and slightly shorter crank arm length is great. Like I said I'm 6 feet, and I used a relatively complex online crank arm calculator somewhere (had to measure various bones which isn't easy) and I thought because I'm 6 feet and they put 175s on most bikes that I would end up with 177.5, was really hoping for it (hey, I'm American, bigger is always better, right?), and it came out right at 175 exactly. And the guy I was talking to about this said for me he might even try 172.5 for the rpm aspect. I just left it at 175.
 
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