Slack head angle?

[Captain Fastbastard Mayhem]

 

 

Jip, have the 6.6, with lyric on. With the trek it feel much "flatter" the fork....

 

But i may have the suspision that the lyric was much to big for the fuel ex9 frame, which gave it that feel. Think the trek is rated for 120mm fork,haha

 

Lol!

 

Yeah. That definitely would have made a significant difference. More like a 66 then, which makes a 2.5 degree difference between the 2

Edited February 20, 2014 by cpt armpies mayhem

[TAAHIRWP]

Fuel - 68

rides best with 120mm fork and leave as is.

 

doesnt the slacker angle help with stability on steep descents but you also need to be mobile on the bike and change your riding style a bit. Moving weight side to side and forwards to cover the front wheel a bit is standard stuff if you want to go fast downhill.

Correct me if i am wrong (cz im still a noob), but the bb location also shifts if one would attempt to alter HA with a shorter/longer fork. which then affect the bikes handling, no matter how skilled the rider. too slack for the geometry would course the front wheel to un-weight in corners or even throw your balance off... also higher BB so centre of gravity is not as close to the ground as originally designed, again affects cornering.

 

i dont know just my 2cents, im sure there is a steep/slacken tolerance one is able to go.

 

but a bike designed with a slacker head angle should ride/descend like a bomb?

[Captain Fastbastard Mayhem]

100% Taahir

[Headshot]

Guys, don't get ahead of yourselves. You'd have to really do something bizarre like mount a DH fork on an XC bike to get the kind of problems you mention. Adding 20-30 mm to a fork on a bike designed for a 120 or 100mm fork will not have a negative effect, unless you expect the bike to still ride exactly like the shorter forked version - in fact it will be better if you like descending...

[Captain Fastbastard Mayhem]

Guys, don't get ahead of yourselves. You'd have to really do something bizarre like mount a DH fork on an XC bike to get the kind of problems you mention. Adding 20-30 mm to a fork on a bike designed for a 120 or 100mm fork will not have a negative effect, unless you expect the bike to still ride exactly like the shorter forked version - in fact it will be better if you like descending...

 

Problem is, Tim, in this case it's an extra 50mm travel and the a2c measurement is an extra 5.56 cm - which raises the BB by about 2.5cm, raises the headset by about 4.5cm, and extends the wheelbase by quite a bit. It would also have a dramatic change on the head angle. making it very much unlike the bike it was designed to be..

Edited February 21, 2014 by cpt armpies mayhem

[porqui]

Now for a system where you can adjust your HA with the help of your dropper post.

Seat up head angle steep.

Push seat down and HA slackens.

 

 

Hey! it's Friday

Edited February 21, 2014 by porqui

[Headshot]

50mm might make the change more extreme but nothing you can't overcome with stem and headset spacer changes and some extra air in the rear shock - I could make it work I bet. You can't just change one thing and leave the rest alone or expect the bike to feel the same as it did. See my earlier comment on the proper way to ride - ie not like a sack of potatoes, but mobile over the bike.

[Captain Fastbastard Mayhem]

50mm might make the change more extreme but nothing you can't overcome with stem and headset spacer changes and some extra air in the rear shock - I could make it work I bet. You can't just change one thing and leave the rest alone or expect the bike to feel the same as it did. See my earlier comment on the proper way to ride - ie not like a sack of potatoes, but mobile over the bike.

 

Oh absolutely - but then that wasn't the point of the OP, considering the bikes he's mentioned. A trek Fuel with 120mm at the back and 55mm extra height at the front is going to perform very differently to how it was intended to. And that also would have levelled out the head angle quite a bit.

 

But yeah - you CAN make it work, but at what level does it stop being a viable option, and become just plain stupid? The extra height in the front and the slacker angles would have made climbing quite a bit harder, at least on technical stuff, compared to the Intense he was running before (with the same fork)

 

Taking my old hardtail into consideration - a bike that was designed around a 100mm fork. I slapped that Revelation on there, which was a 150mm fork, and changed to a 40mm stem. Did it descend better? Hell yeah. But it also climbed like a donkey on the technical bits (much like I climb anyway, but still) and I had to keep my weight very far forward to prevent it from lifting up at the slightest provocation - leading to a loss of steering input as well as me coming off the back quite a few times when climbing. But then I just dropped it down to 120mm and that problem went away... I put it back up to 150mm for the downs. The BB started off being low with the 100mm fork on there, so with the 150mm on there it was in the same height range as bikes designed around a fork of that size...

 

Point is though - a bike built around a 170mm fork is going to handle and ride a lot better than a bike designed around 120mm with a 170mm fork shoved in the front. It's just plain physics. There may be cases where this isn't true, but I'm willing to bet that 95% of the time this rings true.

 

So - the effect of the bigger fork on the Trek Fuel (at least THAT much bigger than designed) led to a bike that performed very differently to what the OP was used to, and led to him going back to the old bike with the same travel, but a steeper head angle.

 

If the increase in fork size was more moderate, though, it would be a slightly different story - I'm thinking of the guys putting 140/150mm forks on the Trance / Fuel etc - which lessens the head angle, increases the travel, but doesn't affect the other variables enough to take it over the edge of viability.

[braailegend]

Here is a proper slack setup, mondraker putting no limits on how far they go, with their whole design process backing slackness, like it's a new wheelsize, lol. Just thinking having setup like this, will definitely handle/be different to the old steep setup. But these bikes are not designed with climbing in mind.

 

http://ep1.pinkbike.org/p4pb7883133/p4pb7883133.jpg

 

http://www.primussports.com/IMG/jpg/Mondraker-Zenith-Amael_LR.jpg

 

http://singletrackworld.com/wp-content/blogs.dir/1/files/2012/07/SBOUE160-640x426.jpg

[TAAHIRWP]

I think a frame designed for 100mm or 120mm with 140mm or 150mm fork will not do well on steep climbs because the seat post angle is affected as well. The seat post and seat will be more over the rear wheel, therefore the riders weight will be over the rear wheel making it hard to pedal, especially for the taller guys. And then like Mayhem said above the rider still has to contend with the front wheel wanting to pop up all the time.

 

The fuel is an awesome trail bike, and the travel and head angle allows the bike to climb and descend equally well. I would leave that bike as is. Oh wait, I did...

 

Yoh! Imagine climbing steeps and trying to shift your weight forward but the bike pulls you over the rear, and at the same time try to put weight over the front and keep the wheel down... Man!! Just sounds frustrating. LOL

[Capricorn]

Mayhem: it gets stupid when you violate the maximum allowable fork travel: decreasing the HA increases the loading on the headtube. The bike won't break immediately,the risk goes up substantially. An XC bike has less reinforcement to save weight, so respecting the max allowable travel is pretty wise.

 

Increasing the fork travel and consequently decreasing the HA, up to the manufacturer's stated limit on fork travel, gives the rider a choice of riding style. Adaption is the key.

 

The harder a rider pushes whatever bike he rides, the more capable he is of adaptation, simply because at higher speeds, you need shifts in body weight to be more effective at controlling the bike. Once you more comfortable shifting weight around, the shift between different geometries will come more naturally, and thus quicker.

 

Case in point, I've been riding my trail bike a lot more, and switching to the DH bike was actually a big change. The steering is quite abit less imprecise due to slacker HA, if i stick to the habits used to steer the trail bike. But the change was quick because pushing the trail bike harder definitely helped me use body english more effectively. That translated over very well to pushing the burly bike around.

 

It also very clearly showed that slacker is NOT always better. Its very much track dependent, and when you do go slacker, you damn well better have the skills to push it.

Edited February 21, 2014 by Capricorn

[Capricorn]

Here is a proper slack setup, mondraker putting no limits on how far they go, with their whole design process backing slackness, like it's a new wheelsize, lol. Just thinking having setup like this, will definitely handle/be different to the old steep setup. But these bikes are not designed with climbing in mind.

 

http://ep1.pinkbike.org/p4pb7883133/p4pb7883133.jpg

 

http://www.primussports.com/IMG/jpg/Mondraker-Zenith-Amael_LR.jpg

 

http://singletrackworld.com/wp-content/blogs.dir/1/files/2012/07/SBOUE160-640x426.jpg

 

the offset to the increased HA, is what mondrake calls the Forward geometry, and strongly associated with that is the zero reach stem. It's key to piloting that beast properly. I think it was PB or VitalMTB that had a review up a few months back on Mondraker's trail bike, and what i recall was the reviewing admiting just how weird the whole zero reach/forward geometry setup felt. But it climbed like a mountain goat and descended like a pyroclastic flow. But just the feel of the setup alone was so different from the standard geometry available on most bikes, it definitely wont be everyone's cup of tea.

Edited February 21, 2014 by Capricorn

[HaydenWilson]

So I have been toying with the idea of replacing the front fork on my 08 stumpy. the stumpy has 120mm of travel front and rear and a head angle of about 68.5.

 

The old fox on it has an a2c of about 490mm and the revelation has an a2c of about 530. so that would slacken the head angle to about 67 degrees wouldn't it?

[Skott5]

Here is a proper slack setup, mondraker putting no limits on how far they go, with their whole design process backing slackness, like it's a new wheelsize, lol. Just thinking having setup like this, will definitely handle/be different to the old steep setup. But these bikes are not designed with climbing in mind.

 

http://ep1.pinkbike.org/p4pb7883133/p4pb7883133.jpg

 

 

 

 

 

That thing must be a biatch climbing a trail with tight multi switch backs, but then again it wasnt designed for that.