Rider is on a size medium w/a 75.4 deg. s/t, 432mm reach and is comfortable combining that with a 50mm stem.
Considering another size "medium" bike w/a 76.5 deg. s/t, 470mm reach w/a 30mm stem.
Big adjustment or negligible?
Freedom of contract. We sell them guns that kill them; they sell us drugs that kill us.
Are the ETT's the same? That's what you feel when seated/climbing. Also if the wheelbases are dramatically different you may feel a bigger difference there than in reach numbers.
Conversion from slacker seat angle bike to a steeper one and trying to figure out how to maintain your seated reach number is super confusing.
When I went through this years back I took a bunch of ridiculously detailed psuedo-science notes...which I've since erased.
Think each degree steeper seat angle equaled a 7mm deduction in (seated) reach.
For stack each 10mm of spacers (at 66°) was 4.1mm shorter (standing and seated) reach.
Note that small stack means reach will be smaller than taller stack, as bars move up and back as spacers are added.
However, reason I deleted these notes is that when you actually go out and sit on a steep seat angle bike you your previous seated reach number isn't all that relevant. Your weight is way more forward, which balances the bike out while climbing in a way that is fundamentally different. My current shorter reach feels stretched out and more comfortable for my back than my longer reach slack seat angle bikes ever did.
Also, like Jotegir said, the wheelbase numbers will be a bigger factor than it would seem on paper.
My buddy was riding an old school Trek, which had a very slack seat angle, just picked up a modern super steep seat angle bike. The standing reach now is a massive 1 1/4" longer (32mm), but the seated reach is 3/4" (20mm) shorter. He climbs and decends better, fit looks spot on, and says the other bike now feels wrong.
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Btw, how tall? Long arms/torso?
As said above.
Tungsten reality is numbers aside there is no real good simple answer. There is so many factors in any frame and bike build that effect how you feel and enjoy the ride. To be honest you can buy whatever frame based on numbers that would work however that is just the start. You have to realize that you will still have to tinker with stem lengths, bar heights, and so on.
And here is the other thing. You can get the frame or bike that numbers look good. However if it feels lousy and you’re not enjoying riding it then you will not ride it.
Oh, and be careful with too tube lengths. Thanks to long term injury effects learned that to long a too tube creates more issues.
When I was speccing out my custom frame (based on an existing frame but shorter stem and longer everything else), I used two websites to compare geometry:
BikeInsights - has a database of production frames and you can compare the geometry with a pretty picture
Mad Scientist geometry calculator - lets you input frame geo and modify it to see how things will change if you go to a longer fork, shorter stem, more swept bars etc.
I'd plug the bikes into these two and see how they compare to each other.
It sounds like you're making a reasonable guess. It always feels like with a new build you make a good guess then just go ride since there's always other factors that contribute to effects you couldn't predict. It's always interesting to see where you end up compared with your initial build.
Oh tip. If your doing this build from the frame up. When you install and go to trim the fork steer tube better to trim it a bit longer then too short. Allows for more ability to tinker with stem height as you figure out what is best for you. The added bonus is there is potential to not have buy a bunch of handlebars of differing rise to find a height that works- what I dealt with when my Stylus came with a steer tube length to short to allow that kind of tinkering.
I am 5'7" I went from a(2018-2020) 430 reach, 597 top tube, 50mm stem. To (2020-2024) 460 reach 593 top tube, 40mm stem. It was a big jump but felt great. I think keeping the top tube similar help make it feel good. Now I ride a (2024-plus) 454 reach, 591 top tube 38mm stem.
Depending on your friends heigh 470 is a huge jump and IMO too long of a reach. What is the top tube length?
Posted by: heathen
I am 5'7" I went from a(2018-2020) 430 reach, 597 top tube, 50mm stem. To (2020-2024) 460 reach 593 top tube, 40mm stem. It was a big jump but felt great. I think keeping the top tube similar help make it feel good. Now I ride a (2024-plus) 454 reach, 591 top tube 38mm stem.
Depending on your friends heigh 470 is a huge jump and IMO too long of a reach. What is the top tube length?
Remembering to include ETT is so helpful. Everyone knows their range of good ETT then it's easy to enough to adjust fore-aft which you can get a pretty good estimate of based on reach, ESTA, ASTA and head tube length.
Posted by: craw
Posted by: heathen
I am 5'7" I went from a(2018-2020) 430 reach, 597 top tube, 50mm stem. To (2020-2024) 460 reach 593 top tube, 40mm stem. It was a big jump but felt great. I think keeping the top tube similar help make it feel good. Now I ride a (2024-plus) 454 reach, 591 top tube 38mm stem.
Depending on your friends heigh 470 is a huge jump and IMO too long of a reach. What is the top tube length?
Remembering to include ETT is so helpful. Everyone knows their range of good ETT then it's easy to enough to adjust fore-aft which you can get a pretty good estimate of based on reach, ESTA, ASTA and head tube length.
Top tube is key. All the numbers work together to make the complete bike. If one number is out it can make a bike ride like garbage. I find it funny how many people are so focused on reach they totally over look ETT.
I tell people reach is how the bike feels standing up. ETT is how the bike feels seated. You can see the bulb turn on when you break it down like that.
Thanks guys, great discussion.
Hepcat - I'm pretty normal proportionally. And very stable. ahem.
Endurimil, oh yeah I got a frim grip on the steertube issue. When I bought my Transition from NS I made Mark(?) much to his annoyance, go dig an uncut fork out of an box yet unopened and swap it onto the bike I was buying because the steertube on it had been cut so short there was maybe 10mm of spacers under the stem. Crazy. + MR's once cut a steer tube too short during a road frame swap. Took a new fork, at my expense, to sort that out.
Tristan good link!
I'll have to research the EET thing more.
So, like some other ideas put forth on these forums (NOT on this particular thread except my own) I'm just kinda' pulling this outta' my ass, but I'm trying to roughly figure out the "cheek-to-palm" distance.
432+50=482
470+30=500 - roughly 8mm (as per Hepcats calculations) from a slightly more than 1deg steeper s/t = 492
So that's like a cm then I can fiddle with spacer or bar height.
Current bike is the middle wheel size, future bike is 29'er.
And there's noone to be found in the showrooms so I can't go sit on one.
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