STA & Cranks

[Miranda]

I've done some reading on these two aspects of geometry, but need some more feedback...

Seat Tube Angle (STA):

The fitter has noted for me 74degrees is a good STA. I've read stock average is between 73-75degrees. My femurs are probably shorter than average in comparison to the rest of my body proportions.

In reading here, some of you with long femurs do well with a 73 STA to get enough set back. In searching geos in smaller frames, the STA seems to be steeper for most brands...

I realize my position could be moved back (with a steeper STA), but it increases reach. Which I have that problem now with my frame that's too big for me...

So, I'm almost thinking I'm better off going with a 73 STA and being moved forward. Which I assume then would shorten my reach, and could be addressed with a longer stem if needed from my ideal TT size...

BUT... what does this moving forward do to your knee position?

Crank Arm Length:

I found a link to an article on bike fit from an old thread that gave an equation regarding crank arm length...

According to that, 165 would seem ideal for me. That's what's on my "overall non-fitting bike" right now as stock. The fitter wrote down 170. It seems like most smaller frames come normally with smaller cranks.

If my legs are average/shorter, would a 165 be better? Or are there other reasons?

The fitter comes very well recommended, so I'd try it... but just looking for some answers from others if there is a reason a longer crank could be a better fit.


TYIA

[Crankin]

My guy insisted I get a 170 when I got my Kuota. I had only had 165s on my other bikes. One ride on the 170s told me no way. I felt like I was mashing the whole time. He thought it would give me power. I said, "You have to have power to get power."
Seriously, I am barely 5' 1" and have a 28.5 inseam. There is a reason small bikes come with small cranks.

[Miranda]

My guy insisted I get a 170 when I got my Kuota. I had only had 165s on my other bikes. One ride on the 170s told me no way. I felt like I was mashing the whole time. He thought it would give me power. I said, "You have to have power to get power."
Seriously, I am barely 5' 1" and have a 28.5 inseam. There is a reason small bikes come with small cranks.

Thx for that post. I read in the fit link I posted about the arguments for diff crank sizes... being what you are saying from your fit guy. The longer crank will give you more power 'supposedly'... but, I agree with you (and that is what this article was saying). There are things about my body that are not designed to 'mash'. My heart muscle can take more effort to spin. I didn't really think/ask about it at the time to the fitter. Too many other things swirling around my head. But, I will. Appreciate the input.

[tulip]

While I think it's very good that you are delving in so deep into the geometry, eventually you will need to just ride a bunch of different bikes and see which ones are comfy and which are not (and try to note what is different about each). At the very least, you will be able to translate all that geometry into real bikefeel, which in the end is all that matters.

[Miranda]

While I think it's very good that you are delving in so deep into the geometry, eventually you will need to just ride a bunch of different bikes and see which ones are comfy and which are not (and try to note what is different about each). At the very least, you will be able to translate all that geometry into real bikefeel, which in the end is all that matters.

That is problem #1... Finding something remotely close to what I want in my size at a shop. I have started calling some out of town shops too. Even one in a larger city for sure I thought would carry my size did not. It's not just low winter stock either. They said they do not stock it standardly *ever*. Of course any shop is happy to order it for you... with the idea that you are going to buy it. Mail order bride deal. Tulip, as I read your story of finding your Luna you wrote about in Ana's thread, I sat at my computer shaking my head thinking... "man, GF, you got lucky!". It's like your Luna found you... it was destiny. Me, on the other hand, hasn't gotten there yet *sigh*.

[OakLeaf]

For me, crankarm length has to do with the angle of my knee at the top of the pedal stroke. Too far flexed and I get kneecap tracking problems. If I'm going to be able to reach the pedal at the bottom of the stroke, then I need 165s. Your fitter should be able to measure your knee angle at the top of your pedal stroke and give you an idea of whether it might cause trouble, and if so, whether it can be remedied by setback or a different STA, or whether you need shorter cranks. That's how I'd discuss it with the fitter if it was me, in any case.

My 50 cm bike came with 170s and I swapped the cranks. I have short femurs.

[Miranda]

For me, crankarm length has to do with the angle of my knee at the top of the pedal stroke. Too far flexed and I get kneecap tracking problems. If I'm going to be able to reach the pedal at the bottom of the stroke, then I need 165s. Your fitter should be able to measure your knee angle at the top of your pedal stroke and give you an idea of whether it might cause trouble, and if so, whether it can be remedied by setback or a different STA, or whether you need shorter cranks. That's how I'd discuss it with the fitter if it was me, in any case.

My 50 cm bike came with 170s and I swapped the cranks. I have short femurs.

Oakleaf... that is good to know. I had knee pain before when my stroke was too far forward. I do know what that feels like. Plus, it gives me some things to discuss with the fitter. Thx.

[tulip]

I would not have bought that particular pre-built Luna without riding it. I just happened to be in the same place as the bike, so it worked out. I would (and eventually will) order another Luna from Margo from afar. This one will be custom made for me. Don't start yet, Margo, I have a kitchen to finish paying for!

I don't know what to tell you about trying bikes. If you get to the point of knowing all the geometry, you can really narrow it down. But I would still want to ride a few before I spent money on a bike.

In any case, you are really gaining alot of knowledge so that when you DO find bikes to ride, you will be armed with great information, maybe even more than the salesperson!