Friday, February 03, 2006

Pivot Point Madness

I got an e-mail question recently that enquired about the Astrix Monk 29"er full suspension bike, and specifically, what I thought about it. Well, I will say upfront that I have not actually ridden an Astrix Monk, but I have ridden several single pivot full suspension bikes. Here is my opinion. Your mileage may vary!

It might serve the reader well to know my perspective here, so I submit this for your approval...........

I started riding different full suspension designs when they first started showing up around these parts in the early nineties. As the original designs hit the streets, it was soon apparent that the suspension designs were quickly falling into two or three different camps. One: the simple single pivot design and it's variants. Second: the "four bar" and Horst link bikes. Thirdly: there were several; shall we say, rather odd designs, some of which persist to this very day! By far and away, the single pivot and Horst link bikes were the most popular designs, even then. It was rather apparent, as well, that each of these had their own peculiar traits, which have never really been changed, in a basic sense.

The biggest nit that anyone had, or still has with full suspension is pedal/ rider induced suspension activation. Usually the "pedal induced" type is the most complained about. To rectify this, several band-aid solutions have been employed over the years, with the biggest and most humorous solution, ('s funny to me, at least!), being the platform dampers available on todays rigs. This all plays out in the ways that the Horst link and single pivot bikes work. The traditional rap with the single pivot bikes is that they suffer from pedal induced kick-back, bobbing in the granny gear, and braking problems. The Horst links were better in the braking and granny ring areas, but you got alot of rider induced suspension activity when out of the saddle, and sprinting was, shall we say....interesting!

Now, I know I'm painting with broad strokes here, but I'm trying to keep this brief! At any rate, the thing that really always bugged me about the single pivot bikes isn't something that is usually mentioned in most reviews. Single pivot bikes usually have their pivots aligned so that climbing is enhanced, which is fine and dandy. I think; however, that the single pivot bikes feel funky in high speed situations, especially in fast," g-out" type corners. The type of corners that you might find in a sweeping downhill run, or in fast singletrack corners. I always can feel the wheelbase grow when the rear end squats down in the corner, and this is disconcerting to me. I never felt comfortable with that feeling, and our local riding enhances that problem, so no single pivots for me!

Of course, this is what the Astrix Monk is: namely, a single pivot bike. As I said, I have not ever ridden one, but I know that the cornering problem is going to be there, for me. Also, the chain growth, pedal induced kick back thing has got to be there, at least a little bit. The geometry doesn't lie! Finally, the swing arm flex must be kept at bay in a classic single pivot design, and I cannot comment on how Astrix has dealt with that. Supposedly, they have a special reinforcement in the rear swingarm to resist twisting and lateral flex.

Now some of you are going to be thinking, "But what about the platform damper? Doesn't that cancell out those beefs of yours?" Well, maybe. I doubt that the negative physical attributes of the design can be cancelled out without also adversely affecting the benifits of the suspension. It's a band-aid solution to an age old problem. Does it help? Probably. I've ridden a single pivot design that had a platform damper, and it made it better- but not that much better! Again, the Monk is part of a species that has certain charateristics in common with each other due to the commonality of design. They all exhibit these characteristics to a certain degree. It's not going to be masked totally by a platform damper, pivot placement, or material choice.

So, what do I think of the Monk, or for that matter, the upcoming Fisher Super Caliber Race Day bike? It's a single pivot bike!...........Nuff said!

Would I ride one?......................Oh, hell yeah! Just because it is a twenty nine inch wheeled bike is enough for me to bite! But really, the bigger wheel option will make the smaller bumps disappear, so that the suspension could be set up stiffer, which should help with my complaints. Maybe someday I'll find out................someday!

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