iftkwoody

I assume that the only way to do this is to add larger forks than I currently have but is there any other way of making the front end of my bike sit a little higher?

I have a Scott aspect fx 35 full suspension and it's a great ride but I do feel as though I am weight forward too much.

My pal who I ride with has a boardman team fs and whilst our bikes are very similar lengths, seatpost height etc his front end sits a good few inches higher.

Is there anything I can do other than getting longer travel forms?

I'm currently using rockshox dart 2 and they aren't great anyway so wouldn't mind replacing them but for now if there's anything.

Thanks in advance

dabac

You should be looking ar riser bars, riser stem, steerer tube extenders instead.
Fitting a longer fork can change a lot of things best left unchanged.
Or simply a shorter stem.
Or try moving your saddle rearwards.

iftkwoody

Won't adding a larger fork make it a bit more "downhilly"?

I'm mostly trail riding and want a bit more travel than I've got anyway or does it really affect the ride quality?

dabac

Dunno about ”quality”.
Depends on what you mean by that.
Whether you like the change or not is up to you.
But it certainly affects ride characteristics.
Steering response will be slower.
It will also put more stress on the headtube/downtube junction.
Most bikes survive that, but it can’t be guaranteed.
It will raise the bottom bracket.
Reduce stand-over clearance.
Move your saddle and your handlebar towards the rear of the bike.

JonathanGennick 

I usually tackle that weight-forward feeling by going to a riser bar and a shorter stem. Doing so moves my grip on the bars upward and backward, thereby rotating my torso to put more of my weight on the seat.

rasheed

Like others have already said, shorter stem or riser bars (or both). If your steerer tube is long enough, you can also try to put in some headset spacers under the stem to move your stem and bar up a few millimetres.

Other than that, what dabac mentioned about why you probably shouldn't put a longer/larger fork on your bike is spot on. Most frames are designed with a certain crown to axle length in mind. Going outside this desired length will not only change the geometry of the bike, as dabac mentioned, it will add stresses to the frame that it wasn't exactly designed to handle, which could lead to the frame failing in one way or another.

JonnyVain

For me, a shorter stem increases handling characteristics. Higher bars increase comfort but handling decreases as your weight moves up also.

No one mentioned but is a gimme, lower bars aid climbing, higher bars aid downhill. So if by chance you're struggling more on climbs i wouldn't raise anything.

Kapusta

As others have said, the most straight forward way to raise the front end for purposes of your riding position is using a different stem or bar.

I would not switch forks simply as a means to change the height of the front end. Use a fork that gives you the performance and bike geometry you want, and then adjust the stem and bar to suit your riding position accordingly.

However if you are looking to replace your fork anyway (for which I don’t blame you, the Dart is mediocre at best), I would do that first, as it will likely change the feel of the front end. THEN mess around with a different stem or bar if need be.

As far as how tall a replacement fork should be: if you like the way your bike handles right now, I would look for one with about the same height (axle-to-crown distance). This is more relevant to handeling than the travel is.

If you would like something with a little more travel and a slighly slacker head angle, I would not think twice about using a fork up to 20mm taller than what came stock.

JonnyVain

Do you need to increase offset on taller forks? Taller fork=more trail=more wheel flop, correct?

Kapusta

Huh. Good question.

Trail would increase with a given offset anytime you slacken the head angle. So yeah, it does when you use a longer fork with the same offset.

Will it cause wheel flop? I think that has a lot more to do with how slack the HA and offset was to start with, but also the cockpit setup and rider technique. I've actually never had an issue with wheel flop since my earliest days riding in the late 90s. It could be that I just learned to compensate, but I am inclined to think it has a lot to do with going with wider handlebars,

Pretty much any fork model out there is only available with one offset, and you will find them speced on bikes with vastly different head angles. FWIW, increasing the fork length by 20mm slackens the HA by a little over 1 degree.

Looking at the fox website, I see that the rake measurement is identical between their 100mm and 170mm 27.5" forks. So, maybe it does not need to change with slacker head angles (longer travel bikes will generally have slacker head angles).

To be honest, I have never given fork offset much thought with mountain bikes, because in my experience, they all seem to work for me just fine. I know in the early days of 29ers, there were some wonky-handeling bikes before the fork offsets were dialed in, and it was something you used to read about in fork reviews, but I guess it got sorted out and you don't read much about it anymore.

Strange, because it is something I DO think and read about with road bikes.

The hard thing about a lot of geometry-related topics with mountain bikes is that geo is dynamic and imprecise to measure. Suspension is always moving, changing all the angles, and it is really hard to know where in the travel the fork is spending most of it's time.

Ryder1

A new fork is expensive, would be my last resort.

If stem spacers aren't all below stem, move them under (or keep 1 5mm spacer above). If that doesn't fix it, consider a shorter stem and/or riser bar. Ritchey makes 30 degree stems (Comp or Pro), Salsa has a 25* stem. Lots of aluminum riser bars to choose from. Check with your friends - stems/bars are something a lot of people replace, so have extras in their parts bin.

I don't know what year your bike is, or what stem/bars it has, but until very recently, mountain bikes were selling with long stems and narrow bars.

hig4s

This has been going around the bike community for a long time. If you do the math of the stress leverage, any change 40mm or less is inconsequential. Giant even uses the same steerer head, welded the same way, to the same size down tube and top tube, on bikes with fork ranges from 100mm to 160mm with several different head angles.

FrozenK

Which Giant bikes use the same front triangle? Because that's what you are saying right? That Giant uses the same front triangle on -I'm guessing the Anthem, Trance, and Reign. Because I'm looking at photos of the Reign and Trance on the Giant website and they are not the same on the head tube area. Not even close. Which makes sense, since the Reign is designed to be ridden through more demanding terrain.

And can you show me the math where an increase of ~10% in the arm length doesn't correspond to an increase of ~10% in the moment applied at the juncture? While we are at it, can you show a forces diagram that shows the resulting change in vectors due to the change in geometry will not affect the overall structure? I'm not saying it doesn't work the way you say. But I'd like to see the "math."

rasheed

Quote the full statement. I said "outside the desired length". That desired length is, more often than not, a range between X and Y, with the length of the fork that actually comes with the bike being somewhere in between. 40 mm +/- is right around the common thought that you can go an inch or two more or less than what your bike came with and still be ok.

hig4s

No that is not what I said. And the whole triangle doesn't matter, only the steerer tube, the size and shape of the cross and down tubes, the welds where the tubes connect, and the angle of the forks to the line that passes through both axles.

To start with you are starting with a false axiom. Using a Rockshox 100mm to a 140mm total length goes from 480mm to 510mm which is a only a 6% increase in total length, then with the increase in travel (at bottoming out, where the forces are greatest) it is an effective 5% DECREASE in length. So unless the hit is at or near 90 degrees with the fork extended (which is virtually impossible) it is inconsequential.

FrozenK

The only problem is that that isn't true. The head tube length on the Reign is shorter than on the Trance, for starters. And the Reign also has significantly more reinforcement. Yes, they are both made of aluminum and welded. But they don't use the same head tube nor are they built in the same way.

What RockShox forks are we talking about? On the Reba RL 27.5 the AC changes from 487mm to 527mm when you go from 100 to 140mm of travel. I couldn't find the AC numbers for this year's FOX forks, but I found a spec sheet for 2013. On the F32, going from 100mm to 140mm of travel increased the AC by 40mm. Now, if you go from a 32 100mm fork to a 34 140mm -which people will do if they want to beef up the bike- the AC goes from 500 to 550mm. Based on all of this, I think that assuming a change in AC of ~10% is reasonable.

Now, you are correct that at full compression the difference is smaller. We won't get into the issue that it will obviously take more force to apply full compression to a 140mm than a 100mm fork.

But we will get into the issue that it isn't axial forces that are the problem, but forces perpendicular to the fork. Which will happen when you, for example case a jump. Fork at full extension.

Again, I'm not saying you are wrong. All I'm asking is for the "math." Now, if you can show me the forces diagram...

hig4s

OK using your own numbers, Reba 100mm are full compression is 387mm long, a Reba 140mm at full compression is 387mm long.

When you case a jump, most of the force is on the frame, or case (from motorcycle terms). Unless it is on a half pipe and you come down backward catching your front tire on the coping, or you nose dive into a jump face, at no time are the forces anywhere near 90 degrees (perpendicular) and at the end of an extended fork. For that matter, forces are almost always well less than at 45 degrees to the angle of the fork.

If you actually want the math, you will have to figure it out yourself. I've done the math before and I'm am not doing it again. And you putting math in quotes does not change the meaning or invalidate the information.

FrozenK

So we are done with the "Giant uses the same head tube, top tube, and down tube for all mountain bikes" part? I see you ignored that part.

When it comes to casing a jump, yes nosediving into the face of the jump is the worse case scenario. Happens more than you'd think. Flat landings also will put some weird stresses that would be accentuated by a slacker angle and longer AC.

As for the math, you are the one claiming it is all OK. I think we need something better than "because I say so." Right now all you've demonstrated is that you don't really know much about frame design and manufacturing -claiming the Reign and Trance use the same head tube, top tube, and down tube. You don't know what the difference in axle to crown is between different forks. And you don't seem to fully comprehend the physics of how impacts affect the frame. Nor do you seem capable of performing an anaylis to evaluate whether it is safe to run a longer travel fork on a frame.