170mm fork on 160mm bike

Rowan404

Hello forum, I own a 2016 Rocky mountain altitude 730msl and would like to get a 170mm travel fork to slacken the head angle and raise the too low bottom bracket height. Is this a good idea or will it obliterate the frame? Thanks for the help.

kajjal

Draw it out and calculate the actual difference, it won't be that much at all.

steve_sordy

It might not be just another 10 mm of fork length. I believe that the axle to crown height varies amongst manufacturers and types of fork. So you may get lucky and find the bigger travel fork has the same or less dimension to your current fork. Or it may be bigger than 10 mm. I am not a expert on this, but I have read of this being a factor to take into account.

Similar concerns over the trail dimension.

supersonic

Steve is right, the crown to axle measurements vary (amongst others), so a new fork could actually make no difference - or lower it further. Assuming it was exactly 10mm more, you'd slacken the angles by about 0.5 of a degree, and raise the bb a few mm.

Have you tried less sag, or increasing low speed compression damping (or volume spacers, if an air fork), to try and give the fork a bit more support? The latter wouldn't change your static figures, but when riding you may notice a difference. I'd have a play with what you have (if you haven't already!)

steve_sordy

supersonic wrote:

...............

Have you tried less sag, or increasing low speed compression damping (or volume spacers, if an air fork), to try and give the fork a bit more support? The latter wouldn't change your static figures, but when riding you may notice a difference. I'd have a play with what you have (if you haven't already!)

Good questions supersonic.

So, a question for Rowan404. What is about your current fork that you are unhappy with that makes you believe that 10 mm more travel will solve? You don't mention any other features about the new fork except extra travel. It's a lot of money.

Rowan404

steve_sordy wrote:

supersonic wrote:

...............

Have you tried less sag, or increasing low speed compression damping (or volume spacers, if an air fork), to try and give the fork a bit more support? The latter wouldn't change your static figures, but when riding you may notice a difference. I'd have a play with what you have (if you haven't already!)

Good questions supersonic.

So, a question for Rowan404. What is about your current fork that you are unhappy with that makes you believe that 10 mm more travel will solve? You don't mention any other features about the new fork except extra travel. It's a lot of money.

There aren't really any major problems with my current fork. I just want better stiffness and damping and am looking at a 170 as I would like to change the geometry a little. I haven't really decided on what fork yet but am looking at the lyrik, pike and yari. The current fork is a manitou mattoc comp 160.

Rowan404

Just got word from Rocky mountain and they do not recommend doing such an upgrade.

cooldad

As they would, so they don't get sued when you crash and die after the bike explodes.

steve_sordy

Rowan404 wrote:

...............

There aren't really any major problems with my current fork. I just want better stiffness and damping and am looking at a 170 as I would like to change the geometry a little. I haven't really decided on what fork yet but am looking at the lyrik, pike and yari. The current fork is a manitou mattoc comp 160.

I don't know that fork, but is it possible to reduce the air volume with spacers? I have done this with a Pike fork and the difference is astonishing. Despite the correct sag, the fork went through its travel far too easily for my taste. If I reduced the sag to stiffen it up, it was too hard. I played around with compression damping etc, but the big change was made when I fitted a couple of spacers, or "tokens" as they are also called. Buy the tokens, or borrow some to try before you buy. Fitting takes a few minutes. Reducing the air volume alters the spring curve and stiffens up the fork in the upper section of its travel. To get the same sag, you may have to reduce the air pressure which will give you a slightly softer ride on the easier stuff. Or just leave the air pressure the same; sag will be reduced slightly but you may prefer the overall result.

If it is possible to do this on your fork, this is such a cheap way of transforming your fork that it would be foolish not to give it ago. One of my mates used oil instead of spacers to achieve the same effect.

Rowan404

steve_sordy wrote:

Rowan404 wrote:

...............

There aren't really any major problems with my current fork. I just want better stiffness and damping and am looking at a 170 as I would like to change the geometry a little. I haven't really decided on what fork yet but am looking at the lyrik, pike and yari. The current fork is a manitou mattoc comp 160.

I don't know that fork, but is it possible to reduce the air volume with spacers? I have done this with a Pike fork and the difference is astonishing. Despite the correct sag, the fork went through its travel far too easily for my taste. If I reduced the sag to stiffen it up, it was too hard. I played around with compression damping etc, but the big change was made when I fitted a couple of spacers, or "tokens" as they are also called. Buy the tokens, or borrow some to try before you buy. Fitting takes a few minutes. Reducing the air volume alters the spring curve and stiffens up the fork in the upper section of its travel. To get the same sag, you may have to reduce the air pressure which will give you a slightly softer ride on the easier stuff. Or just leave the air pressure the same; sag will be reduced slightly but you may prefer the overall result.

If it is possible to do this on your fork, this is such a cheap way of transforming your fork that it would be foolish not to give it ago. One of my mates used oil instead of spacers to achieve the same effect.

Yea I'm aware of the benefits but I don't think manitou makes them for this fork. The only thing I have is compression damping adjustment. Would that do something similar to tokens?

The Rookie

No, but you can add a big blob or grease in the air spring chamber which does have the same effect.

steve_sordy

The Rookie wrote:

No, but you can add a big blob or grease in the air spring chamber which does have the same effect.

If you don't like the effect, oil is easier to get out than grease. Also, oil may be a bit easier for you to measure in volume terms than grease.

The compression damping adjustment is an important function to have, but it does not alter the spring curve like an air volume reduction would do.

Read this:
https://bikerumor.com/2014/10/30/bikeru ... -download/

It will tell you all you need (and probably a lot more) to set up your suspension.

supersonic

I have a Manitou Mattoc Pro - the air spring on this fork has the Dorado spring with IVA (incremental volume adjust) which allows you to fit spacers. Have a read of what it says on your top cap and, as mentioned above, there are other ways to decrease the air volume. They are very linear as standard. Some Comps may have had the MARS spring though.