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  1. #1
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    advice/question Helius AM

    Hi,

    got a question about my brothers Helius AM frame. Itīs a tailormade Helius AM frame. First we wanted it to ride with a 150mm Talas fork, so we let Nicolai make drawings to fit this. Later when the drawings were ready (nothing had been confirmed yet), the new 36Talas RLC 160mm were out, so we decided to go for these. We asked our dealer if N could make new drawings for this, but unfortunately the frame had already been welded.

    So he had a frame which is designed for a 150mm fork, but he has a 160mm fork. Then we asked our dealer (which asked it to Nicolai) if it's possible to drive it with a 160mm fork. They answered it wouldn't be a problem. When he first rode the bike the front always wanted to go to the left and right, which really doesn't ride nice and not stable, and which should be the strength of a Helius AM.

    Now I've measured the bottom bracket height to axle which appeared to be 20,3 mm too high. The seat angle and the head angle changed too, it becomes much slacker. We have asked Nicolai about it and now they say it's not possible to ride it with a 160mm fork.

    What do you think, can this cause the nervous riding in the front? And what about the front that's coming of the ground when climbing? Riding with more sag like the dealer supposed to do is not possible because less air pressure is not possibly. (already near the lowest allowed pressure)

  2. #2
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    Maybe get offset shock mounts ride with a bit less travel. Like that you can get a lower BB and change geo.
    I think going custom always implies risk. Standard geo is proven, once you change from that, the frame becomes unique meaning also less adaptable.

  3. #3
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    No, other shock mounts ainīt an option.

    -3 = 66,34° ha and +30mm bb heigth
    -7 = 66,85° ha and +36mm bb height

    The BB height is getting way to high, so the bike isnīt rideable anymore at all.

    Maybe itīs a risk of tailor made, but my other frames are all right. Frame Geo normally is always made very well by N, also when tailormade. Plus he needs tailor made because he has a very rare size. Normal size wouldnīt ride well.

    So what are the other options?

  4. #4
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    Sorry mate, I don't get your calculation. It seems to be opposite to what I would think should happen.
    Isn't the minus offset supposed to move the shock forward in the frame, thus lowering the BB and slackening the HA?

  5. #5
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    calculations are from Nicolai, so I guess they are right.

  6. #6
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    No those calculations are wrong; the BB should be lowered with the offset shock shuttle. I suspect that the error is arising in communication between you, the dealer and Nicolai.

    The shock shuttles with -3mm and -7mm do move the shock forward in the frame assuming that you are using the appropriate eye to eye and stroke length damper. This brings the rear end up and drops the BB as well as slackening the HA.

    I know because this is precisely what I have done to my AM and I've taken measurements before and after. In my case, my frame was designed around a damper measuring 200mm (eye to eye) by 57mm (stroke). The -7mm mount I have fitted drops the BB by around 17mm and for the same fork length, reduces the HA by about 1.5 degrees.

    The part that needs clarifying is which fork did you originally ask the frame to be designed around? The amount of travel the fork has doesn't mean very much, for example a 150mm Fox 32 fork has an axle to crown (A2C) height of 525mm and a 160mm Fox 36 fork has an A2C of 545mm.

    It is the A2C that determines the end geometry of the bike; if the difference in A2C was truly only 10mm then that wouldn't produce a change you would notice.

    But if you had originally asked for the frame to be designed around a Fox 32 fork (and I am assuming you did because Fox haven't made the 36 range with 150mm of travel for about five years) and are now running a Fox 36 fork, then that would produce the changes you're experiencing.

    This would effectively raise the front end by about 20mm, which would reduce the HA by 1 degree or thereabouts and would raise the BB by a small amount although I really couldn't say by how much.

    Changing the shock shuttle without changing the fork however will not work; the front end would be too high and although you would lower the BB height, you'd rake the front end out even more making the bike even harder to steer at low speed.

  7. #7
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    Just thinking a little more about this.

    If you had asked for a frame to be built around a 150mm Fox 32 fork, then it would make sense for the BB height to be raised. Nicolai would want to keep the BB the same distance off the floor and so with a much shorter fork, they would be moving the BB higher.

    Nicolais response that the frame cannot be used with a 160mm fork after all, is probably explained by the discrepancy between the original request, which they will have rightly assumed was a 520mm A2C and what they now realise to be a 545mm fork (i.e. the 160mm Fox 36).

    Your solution is easy.

    Just go back to using a Fox 32 or RS Revelation 150mm fork.

    Problem solved.

    Next please.

  8. #8
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    First of all, the calculations come direct from Nicolai, so no communication problem between us, our dealer and Nicolai.

    Yes it was going about a 150mm Talas fork first. But when we decide to go for a 160mm Talas we didn't confirm the frame yet, then why do we get a frame for a 520mm A2C fork?

    My brother thinks buying a 32 Talas fork isn't a solution. He doesn't have money anymore for a new Talas 150 fork and he has a nice almost brand new Talas 160 here. BTW a new front frame would be almost cheaper then buying a new fork.

    And we didn't decide to go for a 160mm Talas for no reason. If one orders a frame for a 160mm Talas one would like to ride a 160mm Talas in it. Weird thing is that Nicolai first said (well my dealer told us they did) "yes, you can drive it with a 160mm Talas, no problem", but now when we say it doesn't ride well they say "no, you can't ride it with a 160mm Talas".

    Like you said it's a difference of 20-25mm A2C length. The head angle and seat angle will be slacker and the BB to axle height is much higher. Changing the shock mounts doesn't help.

    Conclusion is: it ain't possible to ride it with a 36 Talas 160mm. We didn't confirm the frame yet. My brother don't want (and can't) ride it with a 32 Talas 150mm. So solution...?

  9. #9
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    Can you reduce the travel on the Fox 36.I notice it is the Talas version,so you should be able to reduce the travel and correct the 25mm A2C length problem.

    Can you reduce the Fox 36's down to 140mm?

  10. #10
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    Dutchdriver - I can imagine this is very frustrating. Here is what I think happened, but you know, I am just some guy sat reading a web forum, so really you shouldn't take too much notice!

    The problem I think centres on what fork you originally specified. If you said to me 'I want it designed around a Fox 150mm Talas fork', then the only fork I think you could possibly mean is a Fox 32, since that is the only 150mm fork that Fox make.

    What I would do then is qualify that with you. I would say: 'Do you mean a Fox 32 150mm TALAS?' If you then said yes, I would then be working with an axle to crown height of 520mm because that's what the measurement of that fork actually is.

    I would also be saying, 'Please be aware that if we design the bike around THIS fork, then if you ever wanted to use a Fox 36 at 160mm, it would most likely make the bike handle very differently. Are you OK with this'.

    I am guessing this is not how the conversation went with Nicolai?

    This is what I suspect has happened based on what you've said; it's just a logical conclusion and could be completely wrong, but if the fork they built the frame around was a Fox 32 150mm TALAS and now you want to use a Fox 36 160mm TALAS, then those two forks do have a very big difference in A2C.

    The frame will still be warrantied for a 160mm fork though because that's what the AM is designed for. Maybe that is what they meant when they said that the frame could still be used with a 160mm fork. Whereas what you meant when you asked that question was 'will it still handle and ride correctly?'

    I think the Fox 36 TALAS settings only allow a switch between 160mm and 120mm, which means that you can't really solve the problem by that feature. 120mm will actually be too much of an adjustment.

    Maybe you can swap the internals of the Fox 36 TALAS for regular Float internals? I know for a fact that you can reduce the travel of the standard Float down to 100mm in 10mm increments. All you need are some plastic spacers and it's a 10 minute home fit job. That would solve the problem without too much expense - maybe even no expense?

  11. #11
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    Nicolai said "if we change the frame for a 150 Talas, you can only ride a 150mm Talas in it". Because of that (we don't really wanted that) and the fact that the new 36 160mm Talas came out (which was very nice) we decided to go for a 160mm Talas.

    We didn't confirm the drawings yet so the frame shouldn't have been produced yet. We told our dealer we wanted to change the geo for a Talas 36 fork, but then the frame was already welded, so we couldn't change it anymore. Very strange that a frame is already welded before we confirmed the tailormade geo....

    So we told obvious we don't want it for a 150 Talas anymore, but for a 36 Talas 160mm could you please make some new drawings, before we confirmed anything.

    Now we don't want to change the fork to 140mm or so, where do I need a 140mm fork for in a Helius AM?

    Swap it for Float internals isn't an option too. The Talas (which is air, like I think you know) is almost too stiff for his weight with an air pressure near the lowest allowed.

  12. #12
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    click and calculate what happens when changing forks

    I figure you know the geo of your frame since you got it custom.

    Some weeks ago i had a technical problem with my fork (fox 36 @160mm) and replaced it with a 888 I borrowed from a friend. This fork has an a2c that is 60mm longer than intended.
    Even with this it was still rideable.
    In my book 25mm axle to crown more should not ruin it too much.

    Don't know what Headset you plan on fitting. If it's a Reset, finding one with a lot less stack height isn't a difficult task. Going to an Acros AH-07 will save 3.5mm for example.
    Maybe this is a route you can go?

  13. #13
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    I'd imagine that with a set of 'offset shock bushings' and an offset headset (or Cane Creek angle set which is also zero stack) you should be able to change the bikes geometry quite dramatically to compensate for the custom geometry. These bushings and headsets can be used to steepen things as well as slackening them.

    Hope this link works but if not try searching for 'offset shock bushings'. At 20 Euros it would be a cheap place to start and got to be worth a try.

    http://www.southerndownhill.com/revi...-bushings.html

  14. #14
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    Dutchdriver,

    Can you send / post the given frame geometry v.s the one you want?
    I have been playing with geometry modifications lately and your case sounds interesting.

    The picture is of a 1.3 deg slacker HA, steeper seat tube angle and a lower BB with Lyrik 160mm.

    Regards
    Saar
    Attached Thumbnails Attached Thumbnails advice/question Helius AM-fork_at_an_angle.jpg  

    A different angle on bikes:
    www.ofanaim.net/has.html

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