Are these forks ok for M20

[Buggbairn]

Hi folks
Are these forks suitable for a small frame M20 ?

Fox 36 Rhythm Float GRIP Boost MTB Forks -29" | Merlin Cycles

Buy your Fox 36 Rhythm Float GRIP Boost MTB Forks -29" at Merlin. Free worldwide delivery available on most items!

www.merlincycles.com

 

[Shjay]

These would fit your bike fine, although Orbea don’t recommend more than 150mm travel on the front, they base it on axle to crown max length found in the Blue Paper. I am running 160mm travel although not fox suspension.

 

[Rod B.]

Buggabairn,

I'd like to add further to what Shjay says in regards to suitable forks for the Rise M20.

You don't mention the year of your Rise M20. For conversation purposes, let's assume it's a 2021/2022 Rise M20. Check the fork section of the "Rise Blue Paper" owners manual for the 2021/2022 Rise. The Blue Paper provides a maximum fork length to be installed on the Rise. The length is measured from the center of the axle to the top of the crown.

The Rise Carbon M series has a maximum Axle to Crown length of 561mm

I find that a 160mm fork travel really enhances the Orbea Rise's descending capabilities. However, it's important to note than when you increase travel, you change the headtube angle. Therefore, while descending is really enhanced, you will also suffer a very slight loss in nimbleness due to the change in headtube angle.

Orbea specifies both a maximum travel (150mm) and Axle to Crown length (561mm) for a reason. As you increase fork travel, this places a higher stress load on the Rise's carbon fiber headtube. Exceeding the maximum Axle to Crown length, will likely exceed the frame's engineered stress load tolerances and you could potentially crack your frame if you take a hard hit. As for me, I subscribe to the "Ride it like you stole it" philosophy and figure the engineers probably built a little bit of a Fudge Factor into the frame.

All manufacturers provide "Axle to Crown" fork specifications for their products. Some do this via detailed drawings and others will provide the information via a user manual. It's important to note that 29" forks and 27.5" forks, even with the same length travel, i.e. 160mm, will have differing Axle to Crown measurements. So when checking for axle to crown length, make sure you are referencing the correct fork, i.e. 29".

If you visit Fox's website and click on "Tech Help" under bicycles, you will open up the Bike Help Center and see a link for "Specification Sheets."

Bike Tech Help Center | FOX

www.ridefox.com

If you review the Fox specification sheet for the 2023 Fox Rhythm, 29" fork, 160mm travel, you will find it has an Axle to Crown measurement of 575mm, plus/minus 5mm in manufacturing tolerance. This places the fork outside of Orbea's maximum axle to crown length and will void the warranty if the frame/headtube should crack.

Note: A Fox fork's Axle to Crown measurement will sometimes change depending upon the year of manufacture. As an example, I ran a 2015 Fox 36, FIT4, 160mm travel fork on my Rise M20. The Axle to Crown measurement for the fork is 567mm, plus/minus 5mm. When I measured my fork, it came out to 562mm.

While the 2015 Fox fork is an older fork, I modified it with a different damper and Vorsprung suspension. It was a very capable fork and I beat the living shit out of my Rise and the fork for over 3,200 miles/5,200 Km, mostly on double black diamond terrain. I had no issues.

Rockshox provides a "Specification Manual" for it's forks which includes the "Axle to Crown" length for every Rockshox fork.

https://www.sram.com/globalassets/document-hierarchy/service-manuals/rockshox/front-suspension/2023-front-suspension-oil-air-coil-token-specifications-english.pdf

My buddies all own, or used to own Rises. They used a host of differing fork brands and models which exceeded Orbea's Axle to Crown maximum limit. The Rockshox Lyrik with it's 35mm stanchions is lighter than the Fox 36 and tends to suit the Rise's ultralight design ethos. My buddies found the Lyrik 160mm to be a very capable fork. If you review the specification manual for the Lyrik 160mm, you will find it has an Axle to Crown measurement of 571mm.

The Fox Rhythm will work on your Rise. Ultimately, how far you want to exceed the Axle to crown gray zone is a personal choice and depends on how well you tolerate risk and uncertainty. Nothing may come of exceeding the axle to crown length. On the other hand, an extremely hard hit may break the headtube or frame and have catastrophic consequences.

Be safe,
Rod

 

[Buggbairn]

Buggabairn,

I'd like to add further to what Shjay says in regards to suitable forks for the Rise M20.

You don't mention the year of your Rise M20. For conversation purposes, let's assume it's a 2021/2022 Rise M20. Check the fork section of the "Rise Blue Paper" owners manual for the 2021/2022 Rise. The Blue Paper provides a maximum fork length to be installed on the Rise. The length is measured from the center of the axle to the top of the crown.

The Rise Carbon M series has a maximum Axle to Crown length of 561mm

View attachment 123773

I find that a 160mm fork travel really enhances the Orbea Rise's descending capabilities. However, it's important to note than when you increase travel, you change the headtube angle. Therefore, while descending is really enhanced, you will also suffer a very slight loss in nimbleness due to the change in headtube angle.

Orbea specifies both a maximum travel (150mm) and Axle to Crown length (561mm) for a reason. As you increase fork travel, this places a higher stress load on the Rise's carbon fiber headtube. Exceeding the maximum Axle to Crown length, will likely exceed the frame's engineered stress load tolerances and you could potentially crack your frame if you take a hard hit. As for me, I subscribe to the "Ride it like you stole it" philosophy and figure the engineers probably built a little bit of a Fudge Factor into the frame.

All manufacturers provide "Axle to Crown" fork specifications for their products. Some do this via detailed drawings and others will provide the information via a user manual. It's important to note that 29" forks and 27.5" forks, even with the same length travel, i.e. 160mm, will have differing Axle to Crown measurements. So when checking for axle to crown length, make sure you are referencing the correct fork, i.e. 29".

If you visit Fox's website and click on "Tech Help" under bicycles, you will open up the Bike Help Center and see a link for "Specification Sheets."

Bike Tech Help Center | FOX

www.ridefox.com

View attachment 123774

If you review the Fox specification sheet for the 2023 Fox Rhythm, 29" fork, 160mm travel, you will find it has an Axle to Crown measurement of 575mm, plus/minus 5mm in manufacturing tolerance. This places the fork outside of Orbea's maximum axle to crown length and will void the warranty if the frame/headtube should crack.

View attachment 123775

Note: A Fox fork's Axle to Crown measurement will sometimes change depending upon the year of manufacture. As an example, I ran a 2015 Fox 36, FIT4, 160mm travel fork on my Rise M20. The Axle to Crown measurement for the fork is 567mm, plus/minus 5mm. When I measured my fork, it came out to 562mm.

While the 2015 Fox fork is an older fork, I modified it with a different damper and Vorsprung suspension. It was a very capable fork and I beat the living shit out of my Rise and the fork for over 3,200 miles/5,200 Km, mostly on double black diamond terrain. I had no issues.

View attachment 123776

Rockshox provides a "Specification Manual" for it's forks which includes the "Axle to Crown" length for every Rockshox fork.

https://www.sram.com/globalassets/document-hierarchy/service-manuals/rockshox/front-suspension/2023-front-suspension-oil-air-coil-token-specifications-english.pdf

My buddies all own, or used to own Rises. They used a host of differing fork brands and models which exceeded Orbea's Axle to Crown maximum limit. The Rockshox Lyrik with it's 35mm stanchions is lighter than the Fox 36 and tends to suit the Rise's ultralight design ethos. My buddies found the Lyrik 160mm to be a very capable fork. If you review the specification manual for the Lyrik 160mm, you will find it has an Axle to Crown measurement of 571mm.

View attachment 123778

The Fox Rhythm will work on your Rise. Ultimately, how far you want to exceed the Axle to crown gray zone is a personal choice and depends on how well you tolerate risk and uncertainty. Nothing may come of exceeding the axle to crown length. On the other hand, an extremely hard hit may break the headtube or frame and have catastrophic consequences.

Be safe,
Rod

Rod, many thanks for your detailed post, it's much appreciated.
Given that I'm not big on leaving the ground to any extent I don't find myself getting anywhere near stressing that specific area of the frame.
It sounds like you and your buddies have put in a lot of trail time with Forks slightly exceeding Orbea's limits and I bet you guys put your set-ups to the test quite often.
Thanks again and best wishes from Scotland
Buggbairn

 

[Rod B.]

Rod, many thanks for your detailed post, it's much appreciated.
Given that I'm not big on leaving the ground to any extent I don't find myself getting anywhere near stressing that specific area of the frame.
It sounds like you and your buddies have put in a lot of trail time with Forks slightly exceeding Orbea's limits and I bet you guys put your set-ups to the test quite often.
Thanks again and best wishes from Scotland
Buggbairn

 

[Rod B.]

Buggbairn,

I can guarantee that my buddies and I have greatly exceeded the design parameters for the Rise. In my younger days I was pretty much willing to hit any line, gap or jump. I find that as I approach the age of 64, crashes hurt a little bit more and I'm a little bit more cautious on line choice. Like you, I tend to avoid large jumps, but I'm a sucker for a technical rock section or drop. Never buy a couch.....

You'll be really happy with a 160mm fork. The Fox Rhythm is also a good choice. With the money you'll save, maybe consider changing the damper to a GRIP2 damper. The Grip 2 is a very good damper and you'll essentially have a Performance Elite fork.

Last September, my buddies and I did a two week road trip from California to Bentonville Arkansas. Along the way, we stopped and rode various bucket list places. The riding was incredible. During the trip, I took pictures with my iPhone and used the pictures to make a trip video. I don't own a GoPro, so the video is mostly pictures of my buddies and I and the places we rode. Someday I may buy a GoPro, but not today. I hope you enjoy the video.

Depending upon the device used to watch the video, it may automatically default to a blurry 360P and you'll need to manually switch the video to high definition 1080P. You can do this by clicking on the gear symbol in the lower right corner of the video.

 

[Buggbairn]

Hi Rod, thanks again for the Reply. I also have 3 or 4 mtb buddies who love a weekend away in the hills, we're spoiled in Scotland with our single track paths and forests. The bike park availability is growing which is also encouraging. I'm 49 and a late starter on the mtb scene (5yrs) I never had that period of my youth where the "fcuk it" attitude would get you over most jumps. I have the cautious 40 something head which does to many "What if" calculations . I just wish we had a bike park close by with progressive jumps and drops.

Enjoy your weekend