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All,

I’m shopping for a new road bike with endurance geometry (more upright position and shorter top tube), 9mm drop saddle-to-bars. I’ve had a Guru fit done by a professional fitter. The main problem is I’m 5’5” with 29” inseam, and one arm is 2” shorter than the other. So it’s been hard to find a small frame with a short enough reach and tall enough head tube (enough stack) to put the bars close enough without compromising handling.

Most of the 48cm or 49cm frames I’m looking at have a top tube that is too long and/or the head tube is not tall enough. Many 50cm frames don’t have enough standover clearance. The fitter has spec’d a 70mm 6 degree stem as a minimum and doesn’t want to go shorter.

I thought it might work to use a 70mm stem with a 25 or 30 degree rise, to effectively reduce the reach and get the handlebars high enough. It’s sort of like making the head tube taller and the top tube shorter, but with a riser stem. However, my fitter has advised against this, saying that using a riser stem with that much rise may adversely affect handling and weight distribution.

My question is, how is using a stem with 25 degree rise different from having a frame with a taller head tube (more stack) using a 6 degree rise? Is there a handling difference, and why?

Thanks

  • How did you end up with 2" / 50mm difference in arm length? Does it affect your shoulders? Is the difference in the forearm, upper arm, wrist, shoulder or just an overall shortening? Would it be any advantage to try a 2" thick foam wrap around the handlebar on your short side and see what that does? I've heard of different leg lengths being managed by shorter cranks and thicker pedals. – Criggie Jan 30 '16 at 0:45
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    Criggie, I broke my elbow at the growth plate as a kid, and after surgery it stopped growing so the forearm is shorter. It does affect my shoulders. My fitter said my body has adapted remarkably. I think it helps a lot that I do yoga regularly. It doesn't really cause problems except in fitting a bike. – North Krimsly Jan 31 '16 at 3:28
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    I suggest you inquire about medical adjustment support devices. Same sort of thing as orthotic shoes etc, perhaps you need a custom handlebar so the shortside really is 2 inches closer than the long side. Yes, it would look bizarre, but if it helps you then why not? Pick up two old scrappy handlebars and cut them to suit, and clamp them together with overlap and try it out. Nothing ventured.... – Criggie Jan 31 '16 at 8:18
  • This question is a couple years old now - do you have any more-recent information to add on what you did, and how its been working for you? – Criggie Jun 5 at 1:11
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Here's some images to help see the relative differences. Note they assume your stem starts at the same point, so if you're thinking of raising it, print the top one out on paper and then draw your riser in, and how the other stem sizes would work.

enter image description here enter image description here

If you're feeling unsure, wimp out and buy/borrow an adjustable stem. They're heavy and complex, but you can pick an angle and a length, tighten the bolts, and try it for a ride or two.

enter image description here enter image description here

My personal story - I changed from a 120 mm long quill stem to a 40mm long quill stem that is also 40mm higher, and fast downhills got so much more comfortable. However my climbs mean I have to get up on the front of the saddle earlier and stay there for most/all of a steep climb. I suspect 10mm either way is going to be hard to feel a difference.

  • Thanks Criggie. If I understand this chart correctly, the math would look like this: 90 degrees + (30 degree 70mm stem) = 120 - 71.5 head angle = 48.5 degrees ------ AND ------- 90 degrees + (6 degrees 70mm stem) = 96 - 71.5 head angle = 24.5 degrees ------- 24.5 degree rise 70mm stem on the chart is about 64mm reach. 48.5 degree rise 70mm stem on the chart is about 45mm reach. So the difference is 19mm in reach, which is quite significant. Does that sound right?` – North Krimsly Jan 31 '16 at 4:53
  • However, I'm still wondering why my bike fitter said not to use a riser stem. He wasn't able to articulate why but said it might mess up the handling or weight distribution. And I'm wondering why that would be. – North Krimsly Jan 31 '16 at 4:55
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    @NorthKrimsly If he can't explain it, then he doesn't know why. Could be asthetics "this makes your bike uglier" or it could be lore he's learned without questioning why. I don't know why either. – Criggie Jan 31 '16 at 8:14
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The weight distribution is affected only by the location of saddle and handlebars related to the wheels. It does not matter whether it is by higher rise stem or higher head tube.

The difference that might affect handling is that system of frame with high head tube and short stem is stiffer than one of lower head tube and longer angled stem. You can feel the difference when pedaling hard, but any modern stem will be far stiffer than old-fashioned quill stems used to be.

There is a financial difference, is your fitter recommending custom frames?

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    A frame with a taller head tube (and taller frame stack) will have small geometry adjustments to compensate for the slight shift in weight distribution towards the rear. Using a stem with a lot of rise will put you in a different body position than was likely intended by the frame designer. The geometry will not be as optimized. Will you notice? Maybe, maybe not. – Rider_X Jan 30 '16 at 3:15
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    Why would the weight distribution change? – ojs Jan 30 '16 at 7:55
  • the more upright your posture is, the more the center of mass is shifted rearward. Conversely when you get in the drops your body angle is more closed, you shift more weight to the front wheel, and the handling changes as a result. – Rider_X Jan 30 '16 at 8:50
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    How does the result differ if it is achieved with higher head tube or higher stem? – ojs Jan 30 '16 at 9:17
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    How exactly is the frame with higher head tube tuned for more upright rider position? Can you point to examples of this design? – ojs Jan 30 '16 at 19:48
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My bike fitter set me up with a stem that has a shorter reach stem and steeper rise to compensate for my aging, stiffer back. It's on a fast Cervelo, but I'm not racing anymore, as likely you aren't with your endurance bike. I cringed when I saw the "look" of the bike, but it rides beautifully and I am friends with my lower back again. His line was "you want the bike to look good, or do you want to look good on the bike." 'Nough said!

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