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New frame need help with geometry changes plus bike porn

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New frame need help with geometry changes plus bike porn

Old 04-15-20, 07:49 PM
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trail_monkey
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New frame need help with geometry changes plus bike porn

I had a soma Wolverine V2 (early model) in a size 58. I warrantied the frame and got a V4 type B and went with a size 56. I always thought the first frameset was a little big for me and I ran a short stem to get a decent fit. It felt pretty good but I figured a 56 would be a closer fit and it would free me up to lengthen the stem a bit. I am 6' and have a 34" inseam. The geometry has changed from my old version to the new version. With the 58 V2, I was running 45 mm spacers with an 80 mm stem with 17 degree rise. The new 56 has more stack height than the old 58. The new 56 standover is a little closer to the old 58 than the new 58 is. The weirdest change for me is the seat tube angle difference between the 2 sizes, which has remained the same through all versions. The 56 has always had a 73.5 STA and the 58 has had a 73. How many cm/mm does this move the seat forward/closer to the headtube? I am trying to set the new bike up similar to the old bike by using a longer stem. I am thinking slightly longer stem like a 90? I have several stems on the wall I have been playing with especially a Race Face ride 90 mm by 6 degree stem and using either 30 or 40 mm spacers underneath. The 90 feels good but I keep overthinking things and changing my mind. I keep trying to visualize how the old one felt and I am grasping at straws trying to remember off muscle memory. I guess I need help calculating the differences in reach when factoring in the new STA. The geometries are below. The first chart is for my old frame size 58. The second is for my new frame size 56. I included a few pics from today's ride for a little porn.









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Old 04-15-20, 09:04 PM
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Geometry is a funny thing.

All my bikes range between 57 & 60.
The seat tube angle with in reason is meaningless. What matters is the sit bones in relation to the crank.
From there, it's the sit bones to wherever your hands spend the most time. (Hoods, tops, drops)

On all my bikes, I place a book on the saddle and a level. Once level is achieved, I place the crank arm in line with the seat tube and measuring inline with the seat tube, the center of the measuring tape is 92cm.

Then I grab a square (or a plumb bob) & place the crank arm horizontal. I sit on the seat and adjust it fore/aft so that soft area between the bony protrusion & my knee cap is over the pedal axle. (KOPS, though the method is dated, it works for me)

After that, knowing that I am in a consistant position over the foundational contact points on the bike, from bike to bike, I measure the sitbone area of the seat to the hoods. In my case: 86-88cm to the vertical part of the hood with 6cm drop in height from the saddle to the "flat" horizontal part of the hood is about right.

Handlebar reach is largely irrelavent on the component level. The stem length is used to compensate for proper 86-88cm total reach & 6cm drop. On one bike the stem is 90mm, on another it's 130mm the rest are in between depending on the particular frame. Some flipped up, some flipped down. Some slammed, some not.

Some handlebars the tops are higher than others, on some the drops are deeper than others. What matters is where your hands spend 90% of their time. Use this as your standard. I usually set the levers as perpindicular to the floor, but they usually end up with them rotated back a couple of degrees. Hence the 86-88cm variability. It largely has to do with the ergonomics of a particular lever & how it fits my hand.

I'll ride any of my bikes a century with out a second of hesitation. They all fit *me* the same. The important bits are in the same place from bike to bike in reference to *me.*

To a large extent, the particulars of the bike frame under me doesn't matter. It's the contact points in relation to eachother.

I hope this is at least moderately insightful.
Base2

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Old 04-16-20, 05:28 AM
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Originally Posted by base2 View Post
Geometry is a funny thing.

All my bikes range between 57 & 60.
The seat tube angle with in reason is meaningless. What matters is the sit bones in relation to the crank.
From there, it's the sit bones to wherever your hands spend the most time. (Hoods, tops, drops)

On all my bikes, I place a book on the saddle and a level. Once level is achieved, I place the crank arm in line with the seat tube and measuring inline with the seat tube, the center of the measuring tape is 92cm.

Then I grab a square (or a plumb bob) & place the crank arm horizontal. I sit on the seat and adjust it fore/aft so that soft area between the bony protrusion & my knee cap is over the pedal axle. (KOPS, though the method is dated, it works for me)

After that, knowing that I am in a consistant position over the foundational contact points on the bike, from bike to bike, I measure the sitbone area of the seat to the hoods. In my case: 86-88cm to the vertical part of the hood with 6cm drop in height from the saddle to the "flat" horizontal part of the hood is about right.

Handlebar reach is largely irrelavent on the component level. The stem length is used to compensate for proper 86-88cm total reach & 6cm drop. On one bike the stem is 90mm, on another it's 130mm the rest are in between depending on the particular frame. Some flipped up, some flipped down. Some slammed, some not.

Some handlebars the tops are higher than others, on some the drops are deeper than others. What matters is where your hands spend 90% of their time. Use this as your standard. I usually set the levers as perpindicular to the floor, but they usually end up with them rotated back a couple of degrees. Hence the 86-88cm variability. It largely has to do with the ergonomics of a particular lever & how it fits my hand.

I'll ride any of my bikes a century with out a second of hesitation. They all fit *me* the same. The important bits are in the same place from bike to bike in reference to *me.*

To a large extent, the particulars of the bike frame under me doesn't matter. It's the contact points in relation to eachother.

I hope this is at least moderately insightful.
Base2
Thank you for that response. I understand what you are saying. As far as KOPS, I have measured that in the past for a reference and out of curiosity, but at least in my case I don't believe it. I am out of the saddle a lot instead of sitting in the seat and I shift around in the seat a lot. Lengths of rides, types of rides, weather conditions, single speed or geared, fatigued or fresh,.....All these affect how much I sit in one place so in my case KOPS has never stayed consistent and therefore I never put too much emphasis on it. I have done all day century rides with no knee issues as well. I am still a kid on a BMX by nature so even on a geared bike a lot of times I like to get out of the saddle and grind it up a hill without shifting. When I built a Salsa Fargo in 2018, I set the saddle where it felt the best and got the drops as high as I could get them. I ride in the drops on that bike 80% of the time cause they are so super comfy for all day rides. This bike above doesn't have the drops quite as high. But I can still crank it out in the drops in comfort. The verdict that is out right now is what feels good on a long bumpy bouncy gravel ride. I just finished this bike so the only rides I have are a couple 4-5 mile rides around our city streets. It is gonna take some experimentation and hopefully I can get it close at the start so I don't fight it.

I thought the steeper seat tube would push me closer to the bars and was unsure how much? I figured in regards to how stretched out I was or wasn't, the STA might have to be compensated for with a longer stem. I do understand it changes my body position to the BB and did notice this at first because I had to slide my seat back a CM on the rails to feel the same balance point as i did on my old 58.

One thing I never understood was the measurement of "reach". I know what it is but how does the measurement from the BB center to the HT center affect anything if you are sitting on the seat? To me ETT has always seemed more like a valid measurement to reference than reach but correct me if I am wrong because I want to understand this.

Last edited by trail_monkey; 04-16-20 at 05:32 AM.
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Old 04-16-20, 05:37 AM
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Stem Comparison Tool | yojimg.net

I've found this stem calculator to be very helpful when choosing stem angle/length.
I hope it helps.
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Old 04-16-20, 08:53 AM
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Originally Posted by ober27 View Post
Stem Comparison Tool | yojimg.net

I've found this stem calculator to be very helpful when choosing stem angle/length.
I hope it helps.
Thank you for this link. I have been playing with it this morning and I have found stem and space or combinations that I never thought of trying.
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