# EMTB Geometry?



## mike_kelly (Jul 18, 2016)

I need a short cockpit. So any frame I look for means studying geometry charts to find those few frames that don't have LLS "modern" geometry. I was looking at the Orbea Rise charts and the reach seemed really excessive even for LLS. Then it dawned on me that on eBIkes the motor appears to shift the bottom bracket back. This might explain why a frame that has similar VTT to what I need has a reach that is unreasonable. I think the reach does not compute because the BB or in this case the motor spindle sits further back, on the frame, so the reach, measured from that spindle point is longer even though the frame may ride more like a similar size and similar VTT on a MTB. It is just the measurement is not comparable due to the shift of the spindle.

Does this make some sense that one might expect a longer "reach" measurement for the same actual fit as a shorter "reach" measurement on a non-emtb?

Thanks for your thoughts


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## beholdtheflesh (Jul 4, 2021)

The Orbea Rise and the Orbea Occam (equivalent non-e MTB) have exactly the same reach and stack. The only difference is the chainstay length is a touch longer on the Rise to accommodate the motor.

The reach and stack measurements are measuring from the bottom bracket (or spindle) on both MTBs and eMTBs so they are measuring the same thing. An eMTB with a reach of 474 will feel the same as a non-e MTB with a reach of 474.


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## mike_kelly (Jul 18, 2016)

Well those bikes (Occam) also look like they have BB behind the seat tube giving them the same position as the eMTB has. The BB is much further back than other (older?) bikes. Thanks for pointing that out. Which problably means it will not work for me, which is disappointing. Back to the drawing board, or geometry charts.


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## mike_kelly (Jul 18, 2016)

Here is my Fatillac compared to the Rise. Although with the BB not in the same place it makes comparison very dificult since it is used as the reference point in reach and stack measurements, it looks like the Lenz BB is much forward of the saddle compared to the Rise where the spindle is further back. So even if the VTT measurements were similar the Reach measurements would not be.
For example:
The Lenz TT=61 and the Rise is 61.9 so 1/2" difference yet the Lenz Reach=425mm and the Rise=474mm nearly 2" difference. So is the Rise really much longer from the seat to the bars or is the rearward BB skewing the reach measurement so it seems much longer.


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## BmanInTheD (Sep 19, 2014)

Seat to the bars (VTT) measurement is just that, middle of the seat tube horizontally to the top of the head tube. Reach is horizontal distance from BB to top of head tube. So the difference is the seat tube angle. The Rise is 2.5" longer in the wheelbase than the Lentz so it makes sense that the "Reach" is significantly longer as well. So VTT is how it fits while seated, Reach is how it fits while standing. Bikes have gotten much longer Reach lately as seat tubes have gotten much steeper.


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## dysfunction (Aug 15, 2009)

it's possible for a bike with a longer reach to 'feel' shorter.. assuming that the bike being compared to has a slacker seat tube.


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## beholdtheflesh (Jul 4, 2021)

mike_kelly said:


> So is the Rise really much longer from the seat to the bars or is the rearward BB skewing the reach measurement so it seems much longer.


I think you are overcomplicating this. The reach, stack, effective top tube length are measurements taken at the touch points (i.e. where you sit, stand, and grab the bars). The specific location of the bottom bracket relative to the rest of the frame are differences in design of the frame only, and they don't "skew" any measurements. The reach is the distance (horizontally) from where you are standing to the where the bars are...and the design of the frame can vary but the reach is the reach.

The similar top tube length but longer reach on the Orbea Rise is due to the difference in the seat tube ANGLE. A steeper seat tube angle brings the saddle closer to the bars, shortening the effective top tube length. However the longer reach (aka longer frame length relative to the bottom bracket) cancels that out, so you get a similar top tube length.

What this means in a practical sense, is that when you are seated, the Rise will feel very similar to the Lenz, but when you are standing, it will feel longer.


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## ocnLogan (Aug 15, 2018)

Reach affects standing fit. ETT (Effective Top Tube), affects seated fit.

Newer bikes have steeper seat tube angles to get your weight forward while climbing and help prevent the front tire from wandering. Its kind of like they took normal seat tube geo (that exists on flat ground), and then tilted it forward, to counteract the fact that the bike is typically being pedaled up a hill with some grade.

The caveat is that all of these measurements are of the FRAME of the bike. Not the touch points. So where your hands end up is going to be dependent on the length of the stem, sweep/rise of the bars, number of stem spacers, etc. 

I nearly wrote out a few more caveats/things to consider, but thought that would muddy the waters a bit. The big picture is not to look at only reach. Look at ETT as well, and then account for other actual contact point differences (like when I went from a bike with 400mm of reach, to one of 475mm of reach ... but the old bike had a 100mm stem, compared to the larger bike having a 35mm stem... the actual position of my hands didn't change much, even though reach and ETT were both way different).


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## beholdtheflesh (Jul 4, 2021)

mike_kelly said:


> it looks like the Lenz BB is much forward of the saddle compared to the Rise where the spindle is further back. So even if the VTT measurements were similar the Reach measurements would not be.


I just re-read this and realized you are essentially correct here - just not articulating it the same way as I did.

_Lenz BB is much forward of the saddle -_ that's because it has a slacker seat tube angle (remember the seat tube angle is the angle from the BB to the saddle)



mike_kelly said:


> So is the Rise really much longer from the seat to the bars


It is not - it is the same (or to be precise, only 9mm different) length from the seat to the bars. Therefore when seated it will feel exactly like that - similar.



mike_kelly said:


> is the rearward BB skewing the reach measurement so it seems much longer.


What you are seeing as "the rearward BB" is actually true in a sense - but more correctly interpreted as "the frame is longer in front, and the seat tube steeper" It's not really "skewing," it's just a longer frame in front of the BB which can appear (when comparing with the Lenz) as the BB being further back.


Just a bit of advice - this pattern you are seeing is called "long, low, slack," "progressive," or "forward geometry." This is specifically designed to allow more maneuvering room when standing, and allowing for more precise body positioning when descending. There are a lot of benefits to this kind of geometry, and the Orbea Rise is not even close to the most "progressive" of the bikes out there. I would not write off a bike because it doesn't have that more "old school" geometry that your current bike has. It's worth trying out the new geometry, I think you would be pleasantly surprised at how well the bike handles.


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## AEyogi (Nov 19, 2021)

Go a size down? Sizing is effectively measured in reach.


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## mike_kelly (Jul 18, 2016)

BmanInTheD said:


> Seat to the bars (VTT) measurement is just that, middle of the seat tube horizontally to the top of the head tube. Reach is horizontal distance from BB to top of head tube. So the difference is the seat tube angle. The Rise is 2.5" longer in the wheelbase than the Lentz so it makes sense that the "Reach" is significantly longer as well. So VTT is how it fits while seated, Reach is how it fits while standing. Bikes have gotten much longer Reach lately as seat tubes have gotten much steeper.


The seatube angle does not affect reach. That is why the industry came up with reach, it is relative to the BB not the seatube. As the seat tube angle gets steeper the VTT gets shorter but the reach remains the same. On the other hand if the BB moves along the line of the wheelbase further back then the Reach gets longer even if the VTT as the VTT remains the same.


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## mike_kelly (Jul 18, 2016)

beholdtheflesh said:


> I just re-read this and realized you are essentially correct here - just not articulating it the same way as I did.
> 
> _Lenz BB is much forward of the saddle -_ that's because it has a slacker seat tube angle (remember the seat tube angle is the angle from the BB to the saddle)
> 
> ...


The new LLS does not suit me as a rider. I am a trail rider. LLS is mostly designed for downhill riders, which I am not. But you confirmed my realizattion that just comparing reach, for me, is not useful. Unfortunately VTT does not give the whole picture either because it is not measured to the handlebar-stem point. When the headtube angles change radically the handlebars move a lot yet the VTT does not change, much.


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## mike_kelly (Jul 18, 2016)

AEyogi said:


> Go a size down? Sizing is effectively measured in reach.


No the virtual seatube and stack would screw me over in a smaller frame.


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## mike_kelly (Jul 18, 2016)

ocnLogan said:


> Reach affects standing fit. ETT (Effective Top Tube), affects seated fit.
> 
> Newer bikes have steeper seat tube angles to get your weight forward while climbing and help prevent the front tire from wandering. Its kind of like they took normal seat tube geo (that exists on flat ground), and then tilted it forward, to counteract the fact that the bike is typically being pedaled up a hill with some grade.
> 
> ...


The trouble is that you only have so much room to move. Longer/short stems and moving the saddle around will only correct so much on a really bad fitting frame. Most LLS frames require a shorter stem to start with.


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## beholdtheflesh (Jul 4, 2021)

mike_kelly said:


> The new LLS does not suit me as a rider. I am a trail rider. LLS is mostly designed for downhill riders, which I am not.


Personal preference is personal preference, but most trail bikes and even most XC bikes in the last few years are moving towards progressive geometry.

I have a 2021 Specialized Epic EVO, traditionally an XC frame, and even that has a 66.5 degree head tube. Although the seat tube is still relatively slack at 74 and change, and it has a 60mm stem and a 460mm reach in size L, so it's not totally LLS, but certainly much more so than previous iterations of XC bikes. And it's still a rocket on climbs, and ridiculously capable on descents.

The Rise is definitely in that middle ground of modern geo, not as long or slack as some other trail bikes, but still modern.


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## mike_kelly (Jul 18, 2016)

I did a lot of research to find the Lenz Fatillac and I really like the way it rides. It fits and suites me well. It is an archetype for me now. So I think I am going to have to find a Rise to try which will not be easy.
Thanks to everyone for the conversation.


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## ocnLogan (Aug 15, 2018)

mike_kelly said:


> The trouble is that you only have so much room to move. Longer/short stems and moving the saddle around will only correct so much on a really bad fitting frame. Most LLS frames require a shorter stem to start with.


I'm not saying anything about good fit/bad fit. I was responding to this.



mike_kelly said:


> Here is my Fatillac compared to the Rise. Although with the BB not in the same place it makes comparison very dificult since it is used as the reference point in reach and stack measurements, it looks like the Lenz BB is much forward of the saddle compared to the Rise where the spindle is further back. *So even if the VTT measurements were similar the Reach measurements would not be.*
> For example:
> The Lenz TT=61 and the Rise is 61.9 so 1/2" difference yet the Lenz Reach=425mm and the Rise=474mm nearly 2" difference. So is the Rise really much longer from the seat to the bars* or is the rearward BB [you meant steeper seat tube] skewing the reach measurement so it seems much longer.*


Just saying that to compare the size of frames, you need to compare reach, and ETT. A steeper STA is not "skewing" the reach measurement. The reach measurement just is. Longer reaches came first, and then a few years later seat tube angles started to steepen.

But the steeper STA is "shrinking" the ETT, compared to a frame that was otherwise identical, with a slack STA.

As mentioned, the Rise isn't actually all that progressive with a 66 degree HTA. But even still, to get the same geo as the Fatilac, will take some doing. The best options are 1) to give it a test ride as is, and see how you feel about new geo (especially if you've never ridden it). 2) If you ride it and find its not your thing, then sizing down, getting a setback dropper post and/or sliding the seat back in the rails, combined with a longer stem and high rise bars for the front.

Not sure on other ebikes that would work though, as I don't really pay attention to ebikes personally (luckily geo is geo ). Best of luck in the search.


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## BmanInTheD (Sep 19, 2014)

mike_kelly said:


> The seatube angle does not affect reach. That is why the industry came up with reach, it is relative to the BB not the seatube. As the seat tube angle gets steeper the VTT gets shorter but the reach remains the same. On the other hand if the BB moves along the line of the wheelbase further back then the Reach gets longer even if the VTT as the VTT remains the same.


Um, that's kinda what I just said. I didn't say seat tube angle affects reach. I said that seat angle is why you can have such a big discrepancy comparing VTT and Reach from bike to bike. And no, LLS is not mainly for DH riders. It's for any riders that ride a lot of up and down terrain, the steeper and longer up and down the better. Traditional geometry is often better for flatter trails where neither steep seat tubes or longer reach is really an advantage.


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## 33red (Jan 5, 2016)

Like you i need a short cockpit.
I just break all the rules. I buy a small Ebike than i put a large seatpost to raise the seat.
Than i put the highest riser bar i can find to get a better fit.
Than i cut the bar to find a position that fits my body and preferences.
Basicaly i keep the short small frame but transform it to fit my legs that can fit a large.


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## mike_kelly (Jul 18, 2016)

33red said:


> Like you i need a short cockpit.
> I just break all the rules. I buy a small Ebike than i put a large seatpost to raise the seat.
> Than i put the highest riser bar i can find to get a better fit.
> Than i cut the bar to find a position that fits my body and preferences.
> Basicaly i keep the short small frame but transorm it to fit my legs that can fit a large.


I have to do that also but it is always better to start with something closer to the right fit.


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## mike_kelly (Jul 18, 2016)

ocnLogan said:


> I'm not saying anything about good fit/bad fit. I was responding to this.
> 
> 
> 
> ...


The thing that messes everything up is that slacker head tubes move the bars back. But there is no real measurement for that. the ST is reflected in VTT but both VTT and Reach are measured to the top of the headtube. With every aspect of geometry changing radically with every builder it gets difficult to assess what might fit. If you buy the typical big three production bikes you can fairly easily find a bike nearby to just test instead of worrying about it. But if you don't live in a big city and you want something off main street then it gets to be roulette. And these days with a lot of chips on the table.


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## mike_kelly (Jul 18, 2016)

beholdtheflesh said:


> I think you are overcomplicating this. The reach, stack, effective top tube length are measurements taken at the touch points (i.e. where you sit, stand, and grab the bars). The specific location of the bottom bracket relative to the rest of the frame are differences in design of the frame only, and they don't "skew" any measurements. The reach is the distance (horizontally) from where you are standing to the where the bars are...and the design of the frame can vary but the reach is the reach.
> 
> The similar top tube length but longer reach on the Orbea Rise is due to the difference in the seat tube ANGLE. A steeper seat tube angle brings the saddle closer to the bars, shortening the effective top tube length. However the longer reach (aka longer frame length relative to the bottom bracket) cancels that out, so you get a similar top tube length.
> 
> What this means in a practical sense, is that when you are seated, the Rise will feel very similar to the Lenz, but when you are standing, it will feel longer.


Just to clarify for anyone else reading this in the future. The measurements reach, stack and VTT are not measured to touch points and that is important. The reach is measured to the top of and center of the headtube not the bars. The stack is measured from the BB to the horizontal line to the heatube also not the pedals that you stand on. The VTT is measured from the same center of the top tube horizontal until it intersects the seat post not the saddle. There is no measurement that tells you where the BB or spindle is relative to the center of the hubs along the line of the wheelbase which would be helpful. The movement of the BB along the wheelbase does change the whole frame.The frame is essentially a paralellogram and the BB is one of the vertices. If the BB is moved every angle changes in the frame. The problem is that there are no real reference points anymore. In the "old" days when the top tubes of road bikes were flat and the head and seat tube angles only varied a few degrees you only really neded to know the TT and ST length. Now there is really no point on a bike that does not change to be a reference point.


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## Tickle (Dec 11, 2013)

I really like the steep seattube and slack HA of the new school geometry but the overall fit and feel of the cockpit is not as comfortable IMO, the upright position puts more strain on my hands(bought some Ergon G3 grips) and it feels more cramped. I'm on an XL w/70 stem too, the stock 55 was too short

**and the wheelbase can be a handful on tight sections of trail


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## ocnLogan (Aug 15, 2018)

mike_kelly said:


> The thing that messes everything up is that slacker head tubes move the bars back. But there is no real measurement for that. the ST is reflected in VTT but both VTT and Reach are measured to the top of the headtube. With every aspect of geometry changing radically with every builder it gets difficult to assess what might fit. If you buy the typical big three production bikes you can fairly easily find a bike nearby to just test instead of worrying about it. But if you don't live in a big city and you want something off main street then it gets to be roulette. And these days with a lot of chips on the table.


I have a giant nerdy spreadsheet where I did the trig to calculate where my hands Wild be on bike frames based on their head tube angle, number of stem spacers, stem length, bar rise and sweep, etc. 

You are right that a really slack bike with 40mm of stem spacers does indeed pull the bars closer to the rider more than a bike with a steeper HTA. But unless you’re really putting tons of spacers, it’s not really a huge change. 

For a bike with a 63-66 degree head tube angle, every 10mm of stem spacers under the stem reduces the effective reach by about 4mm (low obviously dependent on the exact HTA, but it actually doesn’t vary app that much as the angles on bikes is usually only a few degrees different at most). I haven’t done the math on steeper angles, but can’t imagine that would change tons. Maybe 3mm for every 10mm. I might go run the numbers later. 

Which is to say, if you’re worried about getting your handlebars to an ideal stack height on a smaller frame without changing the cockpit size as much. Then your best bet is to run nun either no spacers, or a moderate number, and instead get a higher rise handlebar. You can find 30, 40, 50, 75, and even 90mm riser bars in normal widths out there if you need it.


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## mike_kelly (Jul 18, 2016)

I do all that.
It also depends on how long of a steerer tube you get to work with. Steerer tubes vary a lot these days. Most manufacturers only "allow" 30mm of spacers. I use a nice program called "stem comparison tool" which does some of what you have done. Stem Comparison Tool | yojimg.net
It translates the length and angle of a stem to the reach/run and stack/rise of the stem, so to speak. But I hate the look of handlebars that look like old stingray "ape" bars. 
I have to push the limits. On the fatillac I put in a wolftooth headset spacer at the fork crown which essentially adds to the headtube length.
Because of all this I first try and get a frame that comes close to fitting. But it is really hard sight unseen. It is also easier if you only have to eat only a frame. I have not bought a retail built bike since 1972. It irks me to have to buy a whole bike and discard half the parts.


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## ocnLogan (Aug 15, 2018)

mike_kelly said:


> I do all that.
> It also depends on how long of a steerer tube you get to work with. Steerer tubes vary a lot these days. Most manufacturers only "allow" 30mm of spacers. I use a nice program called "stem comparison tool" which does some of what you have done. Stem Comparison Tool | yojimg.net
> It translates the length and angle of a stem to the reach/run and stack/rise of the stem, so to speak. But I hate the look of handlebars that look like old stingray "ape" bars.
> I have to push the limits. On the fatillac I put in a wolftooth headset spacer at the fork crown which essentially adds to the headtube length.
> Because of all this I first try and get a frame that comes close to fitting. But it is really hard sight unseen. It is also easier if you only have to eat only a frame. I have not bought a retail built bike since 1972. It irks me to have to buy a whole bike and discard half the parts.


Ahh, good to see someone else nerding out about the numbers . That stem tool is a portion of what I did with my spreadsheet. Only difference is that is only the stem (not bar rise/sweep).

I started out because I was really wanting a new bike during Covid, and for years there wasn't anything to demo, or even rent at times. So I was trying to do the best I could without being able to physically sit on the bike and demo. Plus, half the frames I was interested in were some boutique brand that I'd never be able to see in person anyway. So I know the feeling, trust me. If it helps, all the math I think was worth it. The bike I bought during covid fits me better than my old bike. And I chose the frame size entirely based on the math/geo chart ( I was between frame sizes, and went down. But pared with a 50mm stem, 10mm of stem spacers, and 30mm rise bars, I think it fits pretty well).

I agree getting as close as possible at first is the best choice. Just was trying to think of other ways to get you close to where you want. And I still think sizing down, is probably your best bet. A layback dropper post and the seat rails can easily give you +25-50mm more room in your "VTT/ETT", and 10-20mm of stem spacers + a 40mm riser bar will probably get you close. You could also alternatively throw in an angleset to steepen the HTA of the bike. That would push the reach out a bit more.

Good luck .


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## mike_kelly (Jul 18, 2016)

The real question is whether you can trust the numbers in manufacturers geometry charts :0 
I have seen a few that were grossly wrong.
My problem is not too small a cockpit it is too long. To give you an idea my custom road bike is 62x56


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## mlx john (Mar 22, 2010)

The current Levo SL has older school geo. The frame is really expensive though.
My large has a reach of 455mm. My SJ, which is relatively progressive, has a reach of 475mm low, 480 high.

The upcoming update of the SL will probably include more progressive geo.


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## mike_kelly (Jul 18, 2016)

The long reach just puts too much weight on my hands.


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