Riddle me this - Suspension

sandgroper
If you can throw a 120mm fork on a hardtail then why can you not put a 200mm DH fork on a bike like the Cube Frtiz 180 (180mm travel enduro bike) ?

If you have both front and rear tuned to your weight whats the issue?
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iceman2058 9/24/2017 2:37am
9/24/2017 2:37am
All bikes are built around a specific fork length, or a range of lengths. If you stray too far from the ideal Axle-to-Crown height for each given bike, you will end up affecting important general geometry figures like head angle, BB height, and stack height. All of those have a significant impact on how your bike handles and feels on the trail.

In your case specifically, going from a long travel single crown fork to a dual crown fork can end up having an almost negligible effect on the geometry of your particular bike, due to the fact that dual crown forks have A-C measurements that are shorter than a single crown fork, at comparable travel. For example, the A-C of a FOX 36 @180 mm travel is 569mm, while the A-C of a FOX 40 @203mm of travel is 571mm - just a 2mm difference even though there is a 23mm difference in travel. The reason is that the lower crown of a dual crown fork can be much shorter than on a single crown fork, since there is another crown that helps secure the stanchions.

There are however other considerations: the increase in weight is significant, and since that weight is added right to the front of the bike it could end up making the bike feel unbalanced. Also, your frame has not been conceived to run with a dual crown fork, which can generate larger forces on the head tube than a single crown fork can. Additionally, you will need to run bump stops on the stanchions to avoid them contacting your frame directly, and your frame may well not be strong enough in the area of contact to withstand the forces generated in a crash for example. Most DH bikes have stronger tubing and/or specific reinforcements in that area of the top tube to deal with a dual crown fork.

So there you have it. In your case it's doable although still not recommended. Why do you want to do it in the first place?
sandgroper 9/24/2017 3:57am
9/24/2017 3:57am Edited Date/Time 9/24/2017 5:22am
Great thank you for the detailed reply. The reason for the initial question was to have an enduro bike and then put some plush forks on for the occassional DH runs. I hadnt considered the raised BB height of 20mm as being significant after taking into consideration the amount of sag under load. But after reviewing the overall geometry of the DH specific bike frames vs enduro I can see your points are valid. The head tube strength initially didnt seem to be an issue as I thought the plushness of dual crown forks vs the harsh single crowns would balance out in terms of the stress being applied during hits. Given SC forks are designed to flex alot more unlike DH specific forks then i guess thats another no on the list.

Thanks for the feedback Wink


luisgutrod 9/25/2017 5:36am
9/25/2017 5:36am
sandgroper wrote:
Great thank you for the detailed reply. The reason for the initial question was to have an enduro bike and then put some plush forks on...
Great thank you for the detailed reply. The reason for the initial question was to have an enduro bike and then put some plush forks on for the occassional DH runs. I hadnt considered the raised BB height of 20mm as being significant after taking into consideration the amount of sag under load. But after reviewing the overall geometry of the DH specific bike frames vs enduro I can see your points are valid. The head tube strength initially didnt seem to be an issue as I thought the plushness of dual crown forks vs the harsh single crowns would balance out in terms of the stress being applied during hits. Given SC forks are designed to flex alot more unlike DH specific forks then i guess thats another no on the list.

Thanks for the feedback Wink


Many manufacturers of 170-180mm travel bikes state "dual-crown" compatibility... Knolly Delirium, Intese Uzzi, even Canfield Balance..

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