Help on custom Ion16- Mtbr.com
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  1. #1
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    Help on custom Ion16

    My current bike needs to be replaced suddenly and I need some help on geometry for the custom Ion16 I intend to order. As I haven't followed the discussions on geometry of current bikes and there is so much in general, but not specifically for tall guys I appreciate your help.

    I mainly ride in the Alps on (steep) singletrails and sometimes a few days in the bikepark. I don't fly high. Current ride the seat tube is 23" (580mm) and horizontal length is 26.3" (670mm). Head angle 68 degrees. The 160mm of this bike is better for me than the 140mm I had on my Turner 5Spot that I bottomed pretty hard sometimes.
    Sizing is perfect for my 6'8" height with tall legs (weight is 86kg). Saddle needs to be at 90-92cm above BB for pedalling. On the 5Spot with the same size I had a 120mm stem, so also the length is not overdone with a 50mm stem.

    What would the slacker headangle bring at these sizes where stability is already good? I mean the thing is difficult to get around tight switchbacks. Would 650B deteriorate manouvrability compared to my current 26" wheels.

    For future proofing I tend to take the 650B wheels although it is much more expensive, but I am more in doubt about the head angle.
    Thanks in advance for your advice.

    Edit:
    Most likely following new parts will go on:
    - RS Vivid air
    - Manitou Mattoc
    - Spank Subrosa + Hope Evo
    Move over:
    - Hope V4
    - Shimano XT 2x9 + Bash
    - Bar and stem
    Last edited by XXLspot; 04-11-2015 at 02:03 PM.

  2. #2
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    Can you tell me what you're current bike is so I can look at the wheel base?

    I would go slacker than 68deg personally, length is also influenced by the chainstay of course.
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  3. #3
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    Great you are responding, as you must know a lot about these things, given the custom Ion you built yourself.

    My current bike is a Turner RFX from 2008, which is a great ride, but there is no similar bike in the Turner line-up anymore. It's wheel base is a little under 1.25m. Going from the 68 degree angle to the 66 +/- 0.5 of the Ion that will add a little under/over 2cm. Going to the 650B wheel size might add another cm. Both will add stability, while I never noticed any unstability with the Turners (both very similar geo). But before those I started biking with a steep hardtail, so I had the learning curve on the Turners. I am probably so prejudiced by this, that I would not recognize possibilities for improvement.

    Yesterday I read in the Mojo trilogy about the geometron that length and slack head angle of the bike is not really a problem and that getting used to that is relatively easy, leaving no significant drawback.

    As you might understand, this is still my main worry as a custom bike is what it is, once it is made. Thanks for anything you can add.

    Edit: extrapolating the Ion geo sheet, the wheel base would end up at around 1.25 probably a 1cm longer to compensate for the head tube length, but it would not get to the 1.28 I calculated above. Possibly caused by a different real seat tube angle. Something to take into account for the new frame.

  4. #4
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    Ok. I'll try and reply in full tomorrow but I don't thing you should worry too much about the length as Chris Porter suggests.
    The Ion is 65.5/66deg as standard with 650b wheels.
    For you I would give yourself more reach for the same length bike especially with the terrain that you ride so maybe 77deg SA and plan for a 35mm-50mm stem with 65.5/66 HA. You don't need slacker with a bike that long.
    Do you know/can you measure the reach on your Turner? I may be able to find it on the web..
    What stem do you use on the RFX.
    Do you feel it fits you correctly with your current stem length?




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  5. #5
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    Thanks, the whole geometry question is starting to converge in my head. I will try to measure the reach this afternoon as I don't know any number for it on the web, so don't waste your time on that. This bike ran out of prodcution before Turner (and most others) started providing the number.
    On the RFX I use a 70mm 45 degree stem that I feel lately gives some overheight, but the length feels fine. On the Spot that I am also still running for more XC duties around town the stem is really long and I was thinking to put a shorter one on it. With the 160 fork I put in it the geomertries of the two frames are pretty close.
    Together with the increasing inflexibility of age (nothing strange, but I have to admit I get older, although most mountainbikers think I am still 35ish), and coming from 72.5 SA I think the 77SA you suggest is to steep. Note that for my length the cranks are not any longer than average. The 74/75SA of the Ion is I think enough change. I need to think a little longer on this one in relation to the reach though. Thanks for bringing it on my radar. More on this later today.

    By the way I started the ordering proces at the Dutch retailer of Nicolai, so in a few months time it will be there!

  6. #6
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    With 72.5 SA your relative reach is likely to be smaller.
    I felt the same way about SA. You could try moving your saddle forward on the Turner to try the feeling, it's approx 0.5 deg for every 5mm of movement.
    Your bike is already long and the head angle won't be too slack so you don't need a super steep SA for that but it depends on whether you feel you have plenty of room on the Turner already. The reach will increase by about 9mm per 0.5deg steeper ST so with 74.5 of the Ion you would get perhaps another 36mm of space with the same ETT.

    I think you could easily go a further 20mm on your ETT to allow a 50mm stem (it is a much better feeling than 70mm in my opinion, shorter the better) without compromise, the wheelbase would still be comparable to the long Geometron due to the reduced HA and shorter CS. And comparable to my friends Ion with 665mm ETT and 64 HA.
    I have a project on a drawing at 64deg, longer CS and 76SA with 1290 wheelbase and I'm a lot shorter than you..I have no problems with switchback on my current Ion at 1.25m wheelbase, 650b. It is a slightly different technique though.

    Check the reach and think if you feel you have lots of room or if you have to put a big bend in your arms when descending or cornering remembering you will have this extra 36mm with the same ETT/stem.



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  7. #7
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    Measured stack is 640, reach is 495, thus seat angle is 72.6, as htt is 670, which is as documented. When correcting for the spacer and the 45 degree stem the effective stack is 670 and reach is 485. That is nicely on the line through the Ion spreadsheat and one and a half size up from the XL.

    As the extrapolated wheelbase of the Ion using the ETT of the RFX in place of that of the Ion was about the same length as the wheelbase of the RFX, the reach will be marginally shorter, not longer. EDIT: This is incorrect, the reach should be gettting longer, but probably the chainstays are as much shorter (enabled by the ST offset at the BB), which makes the wheelbase stay the same. Why the stack and reach calculated above then come out so nicely is then not explained.

    Fortunately I need a longer ETT due to the larger difference between SA and ST as I should look at the distance between the saddle and the mounting position of the stem on the steerer (roughly) to have the same position when seated.

    As you mentioned I could try to find a shorter stem, although the effective length of the 70mm 45 deg stem is only 50mm (under the assumption that the steerer would allow enough spacers to get the handlebar gets to the same height). I need to check max steerer length for the available forks, if they are also 260mm (like 26" forks), then there is 2cm more available for height adjustment and I could maybe use a normal stem. Then there is more choice (also in very short ones lately).

    If that works I can think of adding some length to the ETT.

    I really need to think whether I need to excessively bend my arms when descending/cornering. I adapted to what was needed on the Turners as that's my only history; I grew so much into them that I consider them to fit me like a glove, which could well be as the stack and reach seem to be pretty consistent.

  8. #8
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    The reach you have on your Turner is the same as on my bike but you at 10inches taller!
    The reach is s function of the position of the BB relative to the frame front and rear centre so and is affected by ST angle relative to ETT too.
    If you discuss with Marcel your questions regarding saddle height, headtube length, bar height and the relationship with ETT and reach he will be able to create a good drawing for you to see.
    I assume you use a high rise bar, 30mm or more?
    There is also a compromise to think about between an ideal seated pedalling position and a bike with sufficient reach that when out of the saddle descending it is comfortable/right.
    I would think a 670-690mm ETT, normal Ion HA, a ST the right length to give you a good dropper post (Moveloc 200mm? If available or will be available would be perfect for you)
    I would get Marcel to produce a drawing with a 76deg SA (this will reduce to 'normal' when sagged for climbing/pedalling and you can always move the saddle back but it gives you reach for a shorter WB bike)
    Marcel has experience of the steeper SA now too. With testing of the geometron.

    You need to talk some of this through with Marcel and see it on a drawing I think.
    I think I could spec up a starter for you that would work well but it's not my bike!!


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  9. #9
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    This thread converges well. After yesterdays post I also concluded that standard SA and HA would probably be OK and that the ETT would end up a little longer than 670 to get the saddle positioned properly to the handlebars. As you already mention the reach and wheelbase will change depending on SA. I agree with you remark that the SA drops when climbing and could be chosen steeper, I would think that both reach and wheelbase then get longer, as I don't expect a change to the chain stays is possible/needed.
    The seat tube I want to be long enough to work decently with a 420mm seat post and will be around 580mm.

    This now gets in the range where I need to draw an overlay of the Ion with the Turner geometry to see where everything lands. After that I will be prepared as good as possible to talk this through with Marcel (assuming he is the one going to design my frame). Of course my handicap remains that I don't have any relevant experience with other geometries, but I have now enough confidence that this will work for me after some adaptation. So thanks for the help in achieving that.

  10. #10
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    The wheelbase will only change with SA if you increase or decrease the ETT. It's most important to get the right reach with your intended stem as you spend all of the fun time out of the saddle!
    Keep us updated on your journey.
    It will be Marcel who does your frame drawings.


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  11. #11
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    When draftly drawing the frame I found a few unexpected things. With the steeper SA, the seats gets significantly higher (about 15mm), as I don't want the handlebar to drop lower with respect to the seat than on my Turners, I also need about 15mm extra stack. Logical, but did not think of it before. The wheelbase gets over 130cm and is thus 5cm longer than my RFX, I can't find a mistake and it is in line with my initial expectations in my 2nd post in this thread, it looks like the wheelbase in the slide does not include the fork offset or so. All in all the reach gets to just above 510mm, which would allow a 50mm stem to get at the same position I am now. I still need to think how much I would really want there, as it comes at the cost of wheelbase. Increasing the SA would increase it, but like the letter 'z' also gets wider when making the angles steeper, the wheelbase also gets longer in my view.

    And indeed the fun starts when descending, but I should also be able to get to the top without aching neck and knees, otherwise I could better buy a DH bike. Unfortunately bikes for tall people are already a lot less ergonomic due to lacking crank lengths and short fork steerer tubes.

  12. #12
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    What rise bar are you using/planning to use?
    Why wouldn't you ask Nicolai to make a taller head tube if you are going custom already? They may not, but no harm in asking.

    If you want to keep the length shorter but have reach and ETT you can spec a slacker seat tube, which will work fine but you will find two things; climbing less efficient unless you move your weight distribution (when climbing bar height should be less of an issue as much as when descending as you should be lower 'in' the bike) one other way to do that is increase the chainstay length....but of course it gets longer again, I don't think you should worry so much about the length of the bike rather get the right fit. Don't forget you can always plan to move the saddle back 15mm and also roll the bars, forward or back to adjust riding position by another 25mm or more.

    It sounds like the Geometron is longer than you would get to anyway at 1313 and it doesn't worry Mr Porter.

    Frustratingly all bike design/fit is a compromise.!
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  13. #13
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    As I find the stack and reach on the RFX quite OK as I have gotten used it. It allows me to ride with light hands (as Lee McCormack describes in his "Mastering MTB skills"), without getting to tired in my legs. So it can not be really wrong.
    I was searching some more theory for what it should be for me and I found this interesting article:
    http://betterride.net/blog/2013/moun...body-position/
    It does not directly lead to measurable values, but I can at least determine whether it is really halfway OK on the RFX and thus also find in which direction it could need to be improved.

  14. #14
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    After a pleasant communication with Marcel about my geometry, the frame was designed and made. I was pleased with the amount of attention I got for the custom surcharge. It got a little stressy to get it in time, but it all worked out perfectly, thanks to Fooh Stuff / Bikeboutique (the shop I ordered through), Nicolai and especially Marcel's efforts.

    So the frame arrived on my doorstep 4th of August. Had a lbs build in the headset the same day and could start building up the frame after work in the evening.
    After some trouble fitting the front derailleur I could go for the first ride on Sunday 9th. It felt good and efficient on the flat and on the tiny hills I have around home; Most importantly it was in time for my three weeks holiday in the Alps that started off Sunday 16th.

    First week I stayed in Les Gets, Portes du Soleil, France on the campsite. I arrived on a quiet campsite as the weather of the preceding week had been terrible. On Monday I decided not to spend the day in the bike park as everybody got covered in mud and I did not want to do so myself on the first big ride with my new bike. So I opted for the black XC tour that needs a little climbing and then descends back through forests and fields on singletrack back to civilization. The climbing went fine (I did not even discover the Compression switch of the Monarch+ yet). In the descending part I was too cautious to really judge the bike as I did not want to get caught by the slippery roots on my first day. From the second day on I had a 5 day liftpass as the trails had dried down pretty well now (unfortunately a shower at 3pm left me and my new bike still caked in mud). I still need to adjust a bit for the cornering but on the straight ends this bike is really fast. I feel a little uncomfortable with the idea, but the comfort the suspension offers is so much better that I just let it roll to the next corner. In the last days of this week I also get my cornering improved to a level I did not achieve before (I like to do these kind of things but I am not really good at it). As I do only up to red trails, as my dropping/jumping small obstacles shows too much variation to try the bigger stuff, I won't judge the bike on this. I find it more difficult to pop the rear, but that might have been a matter of a click less rebound as I found later that it was misadjusted (I am very much a set and forget guy). The bike did not disappoint.

    The second week was spend in Switzerland where most ascends were done by lifts and the descends were all steep, rough singletrail and an occasional bike a hike. As the bike allows to climb really steep stuff and I have enough power for it, the hikes were not very long for me (though next year I'll bring a 22 front ring instead of the 24). Apart from the occasional pedal strikes (The RFX was about 2cm higher in BB) that I had to learn to avoid, it worked very well. One descend there were rather highspeed hairpins (only a little tighter than 90 degrees corners) in a narrow (30cm wide) trail, where the bike showed how precise and predictable it steers with sufficient speed. Hairpin after hairpin were gone in so little time that we all wished the trail would have been a bit longer. Big smiles anyway. So it went for the whole week, even so that I simply rode the bike and enjoyed without trying to judge it. The wheels seemed to be glued to the ground anytime anywhere.

    In the third week I did the Tour de Mont Blanc, so no ski lifts this time and about 1500m in 40km each day. Fortunately I was sufficiently fit to stay cool on most of these climbs and only getting to my aerobic threshold on the steep stuff. This is also where I discovered that setting the compression lever to the middle position let the bike climb nearly like a hardtail (except for the heavy enduro type tires I used for all 3 weeks). Due to the balanced position in the bike I did not need to push my nose in the handlebars to keep the front on the ground. It allowed me to do the full climbs from Les Contamines to Les Houches without having to walk and even do the steepest piece just out of Les Contamines without setting a foot to the ground, showing that even at slowest speeds the steering is good enough to go, although the front does easily wander a little due its 65.5 steering angle. On narrow rocky sections that does require some attention. Setting it from low to high appeared to be non-trivial during the holidays, so much so that I decided to first do this at home as it did not come loose.

    Is its long wheelbase an issue as I was worried about initially? Well not really. Of the hairpins I could not make, I don't think it made a significant difference. On one descend it was too long to follow the trail between some rocks, it simply did not fit where a smaller bike could pass. On a ski lift a threshold was hit due to its length, putting the whole lift to a stop. Hanging up the bike very carefully in a specific position solved the issue on later runs. In Pila one has to get the bikes from the chair lift at the top oneself. When getting up, the chair moved so much that the rear tire hit the ramp and the bike fell out. I was just in time to catch it before it hit the floor upside down. Later runs getting up a bit more subtle solved the issue. In general one has to be on the outlook for issues as 125cm seems to be the maximum bike length the lifts seem to be designed for and the 130.5cm poses issues that were overcome with some inventivity.

    The conclusion is that I am very happy with my bike. A few details still to be sorted out; but nothing that can not be resolved. The Mattoc will need a small service, but I think there is still lubing oil in the lowers, which is much better than my old forks that ran dry in two of these weeks usually.

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