Seen a few threads on here but need to understand what changing the travel at the back does to geometry.

Any one help, The lecht rocks seems to have a bit of experiance. Any one point him in this direction?

What Helius is it?

I have an AC and the geometry doesn’t change with the travel.

ferrit its an AM

I’ve got a Helius AM. The design of the rear shock linkage is such that in all four settings, the bottom bracket height remains the same and, therefore, the geometry does too.

That said, running with the shock on the longer travel settings – the highest travel is just under 170mm (on the upper most mounting location) – will give more sag and may, theoretically, slacken head angles.

Have an experiment with the settings – just be careful not to loose the two rubber washers that space the bushes inside the link!. You mught also need to adjust shock pressures too to get the best results.

Hope this helps.

Digga

cheers for the advice.

probalem is I dont have one just yet.

Im looking for options. I want a nice strong frame, but dont want to run a massive fork on the front. 140mm max for the front so im concerend that the 2011 frame will be too steep as its designed around a bigger fork. I will then plan to use the 136 or 146 setting on the back

RudiBoy

Also have an AM here and Digga’s points are entirely correct. I can tell you that the AM works very well in the second and third hole down, as well as the top hole (longest travel setting) although on the third hole down, the sagged BB height does start to get noticeable.

Depending on what year AM you have (the newer ones have slacker geometry and different eye to eye and stroke lengths on the damper) there is a modification you can make via Nicolai to run the bike in 145mm mode with a shorter fork without upsetting the geometry. This mod lowers the bike quite a bit so that the static BB is around 13″, but since you should only run the bike in the shorter travel settings any way (it will work in all but the longest travel setting, but it works best IMO, in the 145mm or 135mm modes) this still works OK. The modification is legitimate and turns the bike into an absolute cuise missile.

I wrote up the experiment on the MTBR website here: Helius AM to AC

Rudi,

What I elected to do was run a Fox 36 air fork which has 160 and 120mm travel settings, the latter for the uphills.

To be honest, the 160mm fork – because it’s 20mm axle and very rigid – combined with the awesome frame rigidity, makes the bike way more nimble than lesser 140mm bikes.

Ah just seen your reply.

Apart form the BB height, the newer generation AMs will work just fine with a 32mm fork in 150mm mode. The new HA is set at 66 degrees.

Running a Fox 32 or RS Revelation in 150mm setting will result in HA around 67.5 degrees, which is fine for trail riding.

The shorter fork will give you a slightly lower BB, say around 13.5″, but it will be a little taller than other slack/low/fast 140mm trail bikes, which are more likely to be around 13-13.2″

My AM (a 2009 one. If you can get hold of one cheap from Nic UK then this woulde be a real solution!) is set at:

BB 13″
HA 67.5
ST 72

With the Revelation and a Cane Creek Double Barrel and 1×10 drive trail, it weighs 29lbs. Would be 27.5lbs with an air can and a non-droper post.

digga, thanks. I need to run 140..

Gee. Interesting stuff. I am thinking about buying the 2011 helius Am off Nick on this forum.

Problem I have is that I dont want to run forks that are over 140. If I had the choice I would like to run my 125mm vanilla rc. Anything more than that is wasted on me.

What would your thoughts be on getting the -7 shuttle and using 140mm pikes on a 2011 helius geo?? obviously only using the the lower 2 rear shock settings.

JK

You’d have to ask Nicolai about that as it can get a bit complicated. The different mounting plates were originally used I think to allow backward compatibility for owners of older AMs to retrofit the new levers and run 216mm dampers (original design was for 200mm). There are a lot of permutations available though. Have a look at this document (you’ll need Google Translator or a German speaking friend!)

Helius AM Tech Sheet

To be honest though you should really be reaching out to Simon at Momentum, the UK distributor for Nicolai: Simon@nicolai-uk.com or else you can email Stefan Geiss directly at Nicolai: stephan@nicolai.net. He’s the chap who helped me fuigure out the changes I made and I then orderd them through Simon.

To be even more honest, if 125mm really is enough for you then you really shouldn’t be looking at the AM unless you want the bike to be flexible for use here, in the Alps, on DH courses etc (which is why I have one). Of course, you may be getting it second hand and therefore cheap, hence the interest.

Don’t get me wrong, I love mine so much that I’d probably still have one in this guise even if I didn’t want it to be multi-purpose.

To be clear we recommend the AM to be used with forks from 160mm upwards and the AC for 140/150mm forks.

It’s possible, but not recommended, to use different configurations but 125mm is likely to be far too short for either. Altering shock mounts also impacts on seat angle and head angle so again, we don’t recommend unless you know what you’re doing.

Gee- Simon

Thanks for the info.

What im trying to get is a good super tough xc trail bike. running a fork between 125 and 140mm is what I need as I dont want/need to run more than that as I have a DH bike.

As you said simon this sounds a little complex. Perhaps i will end up with a bike that will be niether here nor there.

Rudiboy, sounds like you need a Helius AC. You could also ask them to build a Helius AC with a Helius AM tubeset to stiffen it up. I was going to go down this road but in the end didn’t bother. I think the additional cost at that time was £100, but that might have changed.

The AM for sale on here is lovely but it’s not cheap at £1300 when for £400 you have a brand new one and spec the colour of your choice (although you’d need to wait for it). Warranty is transferable though so the price isn’t too far off what’s reasonable.

Have you also thought about a Last Herb AM? Similar in ethos to the Helius AM but designed from the ground up as a 140mm trail bike with attitude. Dirt reckoned it was the fastest trail bike they’d ever ridden downhill – considerably faster than the Orange Five but heavier also.

RudiBoy, I’d echo what Geetee1972 says; if what you are after is a very good, rigid, sturdy XC frame, then the AC will fits the bill nicely.

My AM is IMHO brilliant for XC but is also plenty burly enough for most local downhill jumps and drops. It is way beyond ‘just’ XC.

Digga where are you based?

cheers for the advice guys

again im after a superburley xc bike, so as you said custom might be the way forward.

just want a frame thats a little like the blur 4x but with a slacker angle using small travel fork.

but the bottom line is I want a nicolai

May be of interest – http://www.nicolai-uk.com/index.php/the-ion-14/