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  1. #1
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    Mach 6 Frame size

    I'm about to order a Mach 6 frame from my LBS, I'm going back and forth between Large and Medium frame size. My height is 5"10".
    Pivot's frame recommendations-
    Med- 5'9"-6'
    Large- 5'11"-6'2"

    I have been riding a large frame firebird even though its recommended for 5"11" and up. The reason is that I don't like how bikes handle with a long stem and I don't want a medium with a long stem. I also (maybe just in my mind) feel like I have a little more stability during high speed descending which is my 1st priority when bike shopping. Right now I'm leaning toward a medium but I just don't want to have to have that long stem on it.

    What I'm wondering is- can anyone here who has been riding their new Mach 6 shed some light on how they like their frame size for their height?

  2. #2
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    I am the same height as you and got a large. I rode the medium and it felt tight even with the 70 mm stem they ship it with. Unless you want a BMX style setup I would go the same direction.

  3. #3
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    I'm happy with a large at 6'1"; long legs, shorter torso. I'm currently running a 70mm stem, 750mm bar. Yesterday's ride had a lot of steep up/down switchbacks and punchy climbs, and I had the room I needed to work the ups. All other aspects felt great as well so I'll run with it.

  4. #4
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    Thanks for the replies so far. You guys have me leaning towards the Large frame/short stem. I think I'm right in that tricky 'goldilocks' height where its right between medium and large. I won't have a chance to demo before buying so I'm trying to gather all the intel I can.

    I'm so excited about this bike that I kept waking up last night thinking about it! Mach 6 be causing insomnia!

  5. #5
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    Well, if it is any consolation, your excitement and lost sleep over the Mach6 is completely warranted. Sooo much fun! I'm really glad I had multiple days off to throw a few different types of trails at her right off the bat.

  6. #6
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    Further update- now back in the medium camp after thinking it over a bit more and sadistically obsessing over every review and comment I could find in this forum and other reviews.

    The guy who wrote this is just under 6' tall-
    "The medium size felt really good. I suspect I could’ve fit fine on the large as well but the medium felt playful and compact without feeling cramped. I took to it immediately."


    Also the length of the top tube on the medium is only .4in less than the large Firebird, I have a very short stem on my FB so I can have a similar one here or a touch larger and it'll probably feel like home with less weight. Salespunk makes me a little nervous since it seems he's as obsessed as I am and he's getting the large but I think I'll roll the dice on Medium. I'm going to see if there is a shop in town that has a medium I can sit on.

  7. #7
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    In terms of sizing, I ride a large HD with an 80 mm stem so I like my bikes more stretched out. I figure my Mach 6 should be perfect with a 65 stem.

  8. #8
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    I'm 5'8" and riding Medium /w short stem (50mm) and it's fine.
    Mach6 top tube is much longer than FB

  9. #9
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    For anyone still interested in this-
    I called around and a LBS had a medium frame (with 80mm stem, standard from Pivot), they strapped on some pedals and I did some laps in the parking lot. It felt pretty close but just a tiny bit too cramped. I know the stem will have to be shorter on my bike and that tips the scales to the large. Bike shop guy said he thinks my legs are on the longer side and that forces me a bit high and over the bars for a medium and I think he's right.
    Final answer= Large Frame

    Its the first time I've seen the bike in person and I must say it is very good looking and seemed super stiff and light. It was an XX1 build with tubes, no pedals or dropper it was only 26.23 on the scale.

  10. #10
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    What's going on with there reach numbers. I'm like 172cm and want to run a 50mm stem. Looking at geo's of kona process 153 and knolly warden these reach numbers look so short. Top tube is about the same. If I want to run that short of stem should I go large?
    Life is like riding a bicycle. To stay balanced, one must keep moving. - Albert Einstein

  11. #11
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    Life is like riding a bicycle. To stay balanced, one must keep moving. - Albert Einstein

  12. #12
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    Quote Originally Posted by thegromit View Post
    What's going on with there reach numbers. I'm like 172cm and want to run a 50mm stem. Looking at geo's of kona process 153 and knolly warden these reach numbers look so short. Top tube is about the same. If I want to run that short of stem should I go large?
    The Mach 6 (like most Pivots) has a pretty slack seat tube angle, effectively decreasing reach for a given top tube length. I haven't heard the rationale for this from Pivot, but I suspect it is attributable at least in part to the inherent antisquat nature of the DW Link suspension.

    Designs like the Kona and Knolly will sink into their travel more when climbing, and a steep seat tube angle helps keep the riders weight from sliding too far back. The Pivot will ride higher in its travel, allowing the front to be more easily weighted under these circumstances.

    I happen to like Pivot's approach, as a) it allows for a shorter wheelbase (long reach/short stems are nice to a point, but eventually the wheelbase can become unwieldy) b) it allows for zero offset seat posts without putting the rider in a TT position at full extension.
    A government big enough to give you everything you want is a government big enough to take from you everything you have.

  13. #13
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    I'm coming off a medium tracer 275 60mm stem which rode pretty well. Climbed good descended very well. I was running a -1.0 angleset on a 160 pike so the headangle was 66.5 +or- .2 bb raised a bit somewhere near 13.5 or so. Comparing geo there pretty close but the pivots Top tube is reading longer by .6 than the intense which I want but intended still has a longer reach. I don't get how pivot is coming up with such a short reach.
    Life is like riding a bicycle. To stay balanced, one must keep moving. - Albert Einstein

  14. #14
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    Quote Originally Posted by thegromit View Post
    Comparing geo there pretty close but the pivots Top tube is reading longer by .6 than the intense which I want but intended still has a longer reach. I don't get how pivot is coming up with such a short reach.
    That is odd considering Intense also lists a slack "effective" seat tube angle of 71* I can only guess that the companies calculate "effective" (since the seat tubes do not form a straight line with the BB) seat tube angle, and in turn effective top tube length, differently. Having the reach measurement is very useful in cases like this, and it helps explain why the wheelbase on the Intense actually comes out longer than the Pivot, even though it has a shorter listed ETT and 1.5* steeper HTA.

    At ~5' 8" it seems unlikely that you would want a large, but perhaps not completely out of the realm of possibility. The head tube/standover is only nominally taller than the medium, so if the seat tube length works for you (i.e. it allows you to run your dropper of choice) it might very well work for you.

    One other consideration- if you haven't already it may worth trying a wider bar with a 50mm stem on your current ride (or even just trying the shorter stem by itself) to make absolutely sure you want to make up for the shorter stem with a longer top tube.
    A government big enough to give you everything you want is a government big enough to take from you everything you have.

  15. #15
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    I am going to be running 785mm bars. Probably just my 60mm stem and get a medium if I get one. I was just liking what these other company's where doing with long top tube short stem combo.
    Life is like riding a bicycle. To stay balanced, one must keep moving. - Albert Einstein

  16. #16
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    I really can't decide what size to get. I want to ride a 50/40mm stem but fear the 15.8 Reach will make me too cramped. The 16.3 reach is more inline with most the bikes I've been looking at (knolly warden/kona process 153) In my eyes the good for the large is; longer reach, 45" wheelbase the head angle is 66.25 and I already have a pike 160 so I won't dip below 66* the bad/worry is will I fit with my 120mm reverb, I think I will but not sure. I also have 170mm cranks. My friend at the bike shop agreed with me about running a large with the short stem. He's my height and also thinks the medium feels a little small. Anyone with a large running a short stem 50/40mm? If so how tall are you and what bike where you riding before? It seems like every bike in this category has a longer reach. Am I crazy for thinking like this?
    Life is like riding a bicycle. To stay balanced, one must keep moving. - Albert Einstein

  17. #17
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    Quote Originally Posted by Salespunk View Post
    I am the same height as you and got a large. I rode the medium and it felt tight even with the 70 mm stem they ship it with. Unless you want a BMX style setup I would go the same direction.

    What size stem did you decide on and how does it feel?

  18. #18
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    I am on an 80 stem with 1 cm of spacers and it feels great.

  19. #19
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    I demoed the Mach 6 in both a medium and large with a 50mm stem. Being 5'9" with a 31" inseam, I could have picked either size. Neither felt wrong for my height and I liked both, they just felt different. The medium was more playful and the large more stable. I ended up with a medium Bronson and I run a 50mm stem and I'm very happy.

  20. #20
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    I'm 5'11, 32" inseam and ride a large with the stock stem. Feels just fine. Thought about the medium, which I ride in Specialized sizes, but the large felt just fine on the Mach 6 to me. Happy with it
    I have too many bikes, but it's not enough

  21. #21
    OriginalDonk
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    I'm 5'11" with a 32.5" inseam, normal proportions. Took out a Mach 6 from the Bike Co. They calle and me, discussed my riding style and existing bike before suggesting a large with a shorter stem. Took a large with a 50mm stem out to some Santa Ana Mountain chunk and felt really balanced. Can't say "dialed" give the tire/fork setup on the demo fleet but really solid. Walked back in and ordered a large.

  22. #22
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    The Mach 6 has a very short reach when you compare it to the 'modern geometry' bikes (mostly from europe).
    That's what was holding me back ordering one. I had a Bronson and I would have liked it to have longer reach too (but the Bronson is even longer than the Pivot). So the Mach 6 felt of my short list.
    Ibis has the same problems with too cramped cockpits as well I think.

  23. #23
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    I'm just under 5ft 9in and running a medium with 50mm stem. Fits perfect. I was on a Carbine 275 medium with 50mm stem. That fit well, but the Mach6 has a big "sweet spot" to work within. The cockpit feels roomy compared to the Carbine but I never feel stretched out.

    According to Pivot, I should run a small (5"4 - 5"9), but I'm glad I'm on a medium. Maybe their sizing chart reflects the fact that they ship bikes with too much stem.

    I would recommend going with a stem 65mm or less on aggressive trail bikes like a Mach6, Range Killer, Process 153, Bronson, etc. Longer stems seem to work better on light trail or XC bikes or if you won't be riding a lot of steep downhills.

  24. #24
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    Mach 6 size.

    Quote Originally Posted by Throttlemire View Post
    I'm just under 5ft 9in and running a medium with 50mm stem. Fits perfect. I was on a Carbine 275 medium with 50mm stem. That fit well, but the Mach6 has a big "sweet spot" to work within. The cockpit feels roomy compared to the Carbine but I never feel stretched out.

    According to Pivot, I should run a small (5"4 - 5"9), but I'm glad I'm on a medium. Maybe their sizing chart reflects the fact that they ship bikes with too much stem.

    I would recommend going with a stem 65mm or less on aggressive trail bikes like a Mach6, Range Killer, Process 153, Bronson, etc. Longer stems seem to work better on light trail or XC bikes or if you won't be riding a lot of steep downhills.
    I ride enduro, I also cannot decide what size, I am 5" 10, the concern I have with the medium is on steep technical climbs, the slack seat angle will put you over the back wheel when seat post is fully extended, as for cramped position I am not concerned as on descents I am generally standing with weight on pedals. Like the idea of lower. Bottom bracket for my style of riding. I am hoping to test a medium in the next week or so, the large felt to big for me even with 50mm stem.

  25. #25
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    I wish I had one to sit on at least to test here, but I had to order mine sight unseen. I'm 5'8" and both the bike shop and pivot customer service recommended the small. We'll see. It should hopefully be here today or tomorrow.

    From reading this, a medium with a 50mm stem might have been best. I think my legs are slightly shorter than they should be for my torso so who knows.

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