|   brake jack/suspension question | frankie
May 18, 2002 7:24 PM | | I ride a Giant NRS. Since buying it, I've started doing more technical downhills, and dislike the fact that applying the back brake effectively locks out my rear suspension, when I need it most.
I want to buy a freeride bike, as I figure this will give me the best of both worlds, and also I don't intend selling my NRS, as I still enjoy riding it as a "general" trail bike. I considered the Giant AC, but I'm reading it also suffers from brake jack, similar to the NRS.
So what should I look for on a full suspension frame, that ensures braking doesn't lock out suspension. I see on frames like the Intense UZZI, there's a pivot just in front of and below the rear dropout, but on the Giant AC the pivot is above the dropout, on the seatstay?? Is this what makes the difference????? |
| the uzzi's got a horst link while the AC doesn't | RVM
May 18, 2002 7:29 PM | | apparently it makes a big difference.
I get brake jack on my hardtail too. So, I try not to use the rear brake at all when the things get rough... |
| Yes, that's what makes the difference | Steve from JH
May 20, 2002 6:08 AM | | When a linkage bike has the rear pivot on the seatstay above the dropout and has a disc brake, then it behaves the same as a single pivot bike when applying the rear brake. When the pivot is on the chainstay, ahead of the axle, it behaves as though it had a pivot farther forward than any of the actual pivots.
Your Giant NRS actually has the pivots mounted the latter way. The problem with it is that it is run already topped out. This means that when you put on the brakes and the load distribution shifts more to the front wheel, the rear shock can't extend any so it acts like it was preloaded the same amount as the load shift. This makes it inactive unless the bump force exceeds the load shift.
Below are some diagrams that compare a monopivot and two Horst link bikes. The smaller the angle b is compared to angle a, the more active the rear shock absorber will be when braking. |
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