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  1. #1
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    AR frame size for 71mm saddle height.

    Hi everyone. I am seriously thinking of buying an AR1 frame set. Unfortunately I'll be buying online and test fit isn't an option. And I can't decide whether I go for size 54 or 51. I am 174cm tall and have 80-81cm inseam. My current saddle height is 71-71,5 cm and I am currently riding a 54cm Felt Z series bike comfortably (the measurements are similar to AR series except for the 20mm taller head tube on the Z). But I am wondering if I should go for 51 on AR for more sporty position.. But it's 120mm short head tube scares me. I don't want to end up using spacers under the stem. 140mm head tube on 54cm AR seems like a sweet spot for me.. But I think I may use a longer reach bar/stem combo on AR, since most flat top aero bars have longer reach, so the total reach can be extended compared to what I'm riding now.

    I know it is personal and each individual is different. But I am wondering about the general choice/consensus for people who has similar measurements to mine.

  2. #2
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    I ride a bigger frame than you but I went with the same size AR as my endurance frame, a Roubaix. The head tube is actually about 4 cm lower on the AR than the Roubaix and reach is a little longer. I was looking for a more aggressive fit and that was enough to get my position where I wanted it. What angle stem are you using? If you are using a -6 stem then you can gain another 2 cm or so with a -17 stem in addition to the lower head tube.

  3. #3
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    The 54cm frame would be a better fit for your 5'8" height if you want no spacers. You're right that the shorter headtube will not bring the bars up enough.

    At 5'8", I'd expect to see a 54-56cm top tube fit you best.

    Ignore that "no spacers under the stem" stupidity if you want the smaller frame, but I think the smaller frame would be a bad decision anyway. The small frame trend has jumped the shark.

  4. #4
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    Quote Originally Posted by cobra_kai View Post
    I ride a bigger frame than you but I went with the same size AR as my endurance frame, a Roubaix. The head tube is actually about 4 cm lower on the AR than the Roubaix and reach is a little longer. I was looking for a more aggressive fit and that was enough to get my position where I wanted it. What angle stem are you using? If you are using a -6 stem then you can gain another 2 cm or so with a -17 stem in addition to the lower head tube.
    Actually the reach is 1mm shorter on AR than on my endurance bike Z, (383mm to 384mm). I believe it is because the seat tube angle is steeper on Z but the top tube length remains the same (545mm). I am using a 90mm and -8 degree stem. The stem/bar combo I'll be using on AR will probably have longer reach. So I bought a cheap longer stem to test the fit on my Z. If I struggle with the reach, I may consider going with the 51cm AR with spacers.

  5. #5
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    Quote Originally Posted by Peter P. View Post
    The 54cm frame would be a better fit for your 5'8" height if you want no spacers. You're right that the shorter headtube will not bring the bars up enough.

    At 5'8", I'd expect to see a 54-56cm top tube fit you best.

    Ignore that "no spacers under the stem" stupidity if you want the smaller frame, but I think the smaller frame would be a bad decision anyway. The small frame trend has jumped the shark.
    Thanks for the input Peter P.(Parker?? You seem to know about bike fit. Why exactly do you think the smaller frame would be a bad decision? Or that the trend has jumped the shark? If it was logical and practical back then, why it isn't now? I am not so experienced in the area but I can see an advantage of having the bars closer and lower, while sprinting and climbing. But both these scenarios are pure performance oriented. I can feel the 160mm tall headtube on my Z is limiting my out of saddle efforts for instance. I cannot rock the bike efficiently. But in comfort wise, it provides me an all day comfort. That is why I think 140mm headtube on 54cm AR would be the sweet spot for me. My only worry is that if I use a bar that has longer reach, such as 3T Aeronova which is the stock bar that comes with AR1 bike, will I get too stretched? You say 54-56cm top tube is best for me.. But 56cm seems too long to me.. But then again I am not very experienced.

  6. #6
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    Why exactly do you think the smaller frame would be a bad decision? Or that the trend has jumped the shark?


    The "super radical difference between the saddle and the bar height" craze looked all rakish and cool but long term comfort such as holding your head up to see down the road, suffered greatly. The claimed aerodynamic benefits are VASTLY overrated.

    Same holds true for sprinting and climbing as you mentioned. Sure; you need to lean forward to engage your more powerful muscle groups, but these super saddle-bar differentials have gone beyond silly. Which is why the market created "comfort" and "endurance" geometries. They merely swung in the other direction, albeit in many cases too far.

    I don't know what the setup of your current bike looks like but your intuition sounds right; the 160mm head tube is too long and 140mm probably won't venture into too short.

    It does sound like your top tube/stem combination is too short for your body and your frame size, but without looking at you and/or the bike, I don't know why. Feel free to post photos here.

  7. #7
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    Quote Originally Posted by Peter P. View Post
    Why exactly do you think the smaller frame would be a bad decision? Or that the trend has jumped the shark?


    The "super radical difference between the saddle and the bar height" craze looked all rakish and cool but long term comfort such as holding your head up to see down the road, suffered greatly. The claimed aerodynamic benefits are VASTLY overrated.

    Same holds true for sprinting and climbing as you mentioned. Sure; you need to lean forward to engage your more powerful muscle groups, but these super saddle-bar differentials have gone beyond silly. Which is why the market created "comfort" and "endurance" geometries. They merely swung in the other direction, albeit in many cases too far.

    I don't know what the setup of your current bike looks like but your intuition sounds right; the 160mm head tube is too long and 140mm probably won't venture into too short.

    It does sound like your top tube/stem combination is too short for your body and your frame size, but without looking at you and/or the bike, I don't know why. Feel free to post photos here.
    I too think the reach became short after I switch to SRAM shifters from Tiagra. The stem is the OEM size. Here's the pic of the bike. Frame size 54, Effective TT is 545mm, 90mm stem(-8). Saddle top from BB center is 71-71.5cm (fizik antares VS) and these are 170mm cranks. I looked for a side view photo of me on the bike but can't find any.

    Btw I did not change the saddle height after I switched to 170mm cranks from 172.5mm. As I felt comfortable. But I recently moved the saddle back about 5mm. I had started to gett some front knee pain after long rides and it helped.

    The bike is 2015 Z6 frame with Z2 fork (6.75 kg. without the pedals and the bottle cages
    AR frame size for 71mm saddle height.-img_6834.jpg
    Last edited by TrueType; 11-28-2016 at 04:52 AM.

  8. #8
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    Geez; the setup of the bike, particularly the saddle to bar drop, looks good. The only thing that's missing is a 5'8" rider on the bike for a sense of proportion and fit.

    If that Felt fits you well, then I'd replicate it with the smaller frame you're considering and forget vanity; install the spacers under the stem and flip the stem up if necessary to attain the same saddle to bar drop.

  9. #9
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    Quote Originally Posted by Peter P. View Post
    Geez; the setup of the bike, particularly the saddle to bar drop, looks good. The only thing that's missing is a 5'8" rider on the bike for a sense of proportion and fit.

    If that Felt fits you well, then I'd replicate it with the smaller frame you're considering and forget vanity; install the spacers under the stem and flip the stem up if necessary to attain the same saddle to bar drop.
    But if we have to replicate the current fit, isn't it easier and better with the 54cm AR? I attach the drawing I made for comparison. These are the basic geometries of each frame sizes based on the saddle height and also reach and stack lengths and HT and ST angles. Every line is center to center and the dashed line is the effective top tube. I also added the virtual stem length (90mm for each) and the 20mm stack from the top of the head tube.

    Red = Felt Z 54cm (current bike)
    Green = Felt AR 54cm
    Blue = Felt AR 51 cm

    You can see the 54cm AR is very much close to what I am riding now.

    AR frame size for 71mm saddle height.-bike-geometies.jpg
    Last edited by TrueType; 11-29-2016 at 03:24 AM. Reason: pic correction

  10. #10
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    Digesting the information from the graphic...

    I'd rather see you on the smaller frame, with a longer stem, and a stack of spacers (no more than the max permissible by the manufacturer; typically 30mm, 20-25mm more common), than the taller frame with an unusually short stem such as the 90mm you're using now. A short stem for your height does not balance the weight distribution over the bike well.

  11. #11
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    Oh I understand. Well it is the stock stem that came with the bike. All 54 cm Felt road bikes share same effective top tube measurement. But the stem length is different for each line up (Z=90mm, F=100mm, AR=100/110mm). Maybe, instead of making a shorter frame, Felt put shorter stems on the Z series to make it more up-right fit. Maybe SuperDave give us an insight if he's still around the Felt forum.

    I was going to try my current bike with a 100mm stem anyway, as I also thought 90 mm is short. But it has been a stormy weather for couple of days here. Hopefully I'll try it tomorrow. I've checked other manufacturer's geometries and they usually put 100 or sometimes 110mm stems for their 54cm road frames.

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