More? Better?

Going Long With The Top Fuel

This is feeling a bit like my personal Groundhog Day at this point. I have lost count of the number of times now that I’ve decided to lengthen the travel of a given bike, or take a long travel bike and put it on a diet, or cut the ear off a sow and fashion it into a silk purse. Yet here I am again, deciding to Frankenstein up the Trek Top Fuel I reviewed last summer.

Why? What is wrong with me? Why can’t I just ride the bike I am sent, quit scratching this compulsive itch, and be happy? Gah. I’ve written about that chicken/egg set of motivations enough too, arguing both sides of the same coin, until I am completely tarred by a brush coated in my own hypocrisy.

But this time, it’s gonna be different. THIS TIME, I am performing a Trek endorsed Top Fuel stretchotomy, adding a modest 10mm of travel at each end of the bike and keeping the faffing to a strategic minimum. This time, I am keeping the paint between the lines.

Trek sells the Top Fuel as a 120mm rear travel bike, usually pairing it with a 130mm fork. As such, the venerable but recently revamped Top Fuel occupies something of a trail-bike no-man’s-land. It has more travel than most dedicated XC bikes, as well as more weight and a ride characteristic that aspires more toward comfort and tractability than blazing acceleration. But it is substantially lighter than most of the current crop of 130-140mm trail bikes, and as such feels a lot more nimble in tight going as well as much more fun to point uphill when compared to some of the plow-oriented competition. It also comes with a nifty little Mino Link at the lower shock mount, allowing for some fudging between more or less progressive shock rates as well as some bb height/head angle adjustment. And, again, Trek absolutely says “go for it” when it comes to adding a little travel to the mix. So, why not? I mean, what could possibly go wrong?

The stretchotomy itself is pretty straightforward. In the case of the 9.8 GX AXS Top Fuel I’m riding, I needed to procure a longer air shaft for the RockShox Pike fork and install it. That took about a half hour, but only because I lost some time drinking beer and looking for a syringe to spooge some oil back into the lowers. Seriously, it’s stupid easy. Just be careful not to scratch the shaft when removing or installing the circlip that holds the air shaft in place.

For the rear, there are travel limit tokens inside the 185x50mm RockShox Deluxe Ultimate shock that can be removed upon disassembly, leaving you with a 185x55mm shock and a travel bump from 120 to 130-ish-mm. However, the sag and travel info anodized onto the shaft will no longer be accurate. So, there’s that to consider. Not a huge deal.

In my case, Trek went low-key upgrade sneaky on me and offered up a 185x55mm Super Deluxe Ultimate piggyback unit with adjustable high and low speed compression damping and hydraulic bottom out. This is kinda cheating, since instead of just pulling the shock apart and yanking the travel limiters, I installed a roughly $600 shock. On the plus side, it’s a very swank upgrade and it takes about five minutes to swap a shock as opposed to maybe an hour spent getting shock oil on my hands. On the minus side, it makes the bike a couple hundred grams heavier and adds $600 to the price tag.

So, the fork ends up 10mm taller, and the rear stays the same, but bottoms out 10mm deeper. Because of this, I flipped the Mino Link from low to high, in order to keep the head angle about the same as it was before (65.5 degrees), but to bring the pedals up so that I wouldn’t be smashing them into the ground all the time. Between the fork getting taller and the chip getting flipped, the bottom bracket went from 345mm to 354mm. All in all, it was a pretty basic swap. I weigh 190 geared up to ride at the moment, so pumped the fork up to 80psi and left it with one air volume token. Both high and low speed compression dials ended up smack in the middle. Rebound also ended up in the middle, 10 clicks out from fully closed. This is faster than I might have gone in the past, but I am trying to keep up with the cool kids here at nsmb.com and get with the times.

Rear setup took some more finagling to get right. I am currently running about 27% sag, in this case 195psi. Low speed compression knob is turned all the way closed (not sure it really is doing much, but am still bracketing runs trying to feel something), and high speed compression is two clicks out from closed. Rebound is 6 clicks out from closed.

In terms of how things have changed, the bike is now a mix of “hell yes, awesome!” and “swatting it with a rolled up newspaper doesn’t seem to be helping when it pees on the floor.” I am going to break this down into two parts: suspension action and handling dynamics.

Suspension Action

I gotta say, I am finally really warming up to RockShox suspension. The fork was impressive at 130mm when I first tested the bike. Opening it up to 140 just sets up more of a good thing. Really nice small bump compliance, responsive and tuneable mid-range, and it behaves really well everywhere from the loose small rock garbage that covers trails everywhere down here in Baja on up through ledgy chatter up into dropping into holes that eat up most of the travel. It’s a very composed, well controlled suspension unit. Adding 10mm of travel enhanced and improved the comfort and the range of the fork.

The shock is something. As far as suspension performance goes, it’s kind of a cheat code. But it took some fiddling to get it where I wanted it, and I don’t think I’m done fiddling yet. First off, at 120mm, Trek recommends sag of around 30%. This felt good to me, and the bike struck a good balance between responsiveness and plushness (relatively speaking, as far as 120mm travel bikes go). Bumping the travel, and with the variable of an entirely different shock thrown into the mix, and that 30% sag number now felt a little too active, too bobby, too deep in the stroke when pedaling around. Yes, it was substantially more plush and tractable, but it felt a bit choppered out and no matter what I did with the low speed compression knob the only way I felt comfortable when climbing was if I threw the lockout switch from open to firm. None of this had been an issue at 120mm.

After a few rides, I arrived at the settings I mentioned above. Less sag brought the ride height where I wanted it and quelled the bob to tolerable levels. Cranking in the low speed compression didn’t seem to have much impact on the bob or the small bump behavior but might, mmmmaaayyyybe having an effect on the ride height, and cranking the high speed in a couple clicks definitely calmed things down in a positive way. It climbs just as well as it did before, but has more tractability and more squishy comfort through to about three quarters travel, then it just quietly eats up whatever the hell I am doing as I try to reach bottom out. Like, super quietly. I mean, ridiculously quietly. The downside to this is that it’s not really a 130mm bike now, because the sag combined with the progression in the air can, combined with that ohhhh, so sweet hydraulic bottom out, well, it’s a challenge to smash all the travel out, at least as far as being an old geezer floating around on loose chundery trails trying not to get stabbed by cactus.

This is all to say, damn. That is a mighty good shock. I think there’s a ton of potential here, and I also think that potential really does broaden the capability of what the Top Fuel can handle. But, that said, it takes some fiddling to get it dialed. And, I suspect it’s not quite gonna be a “one setting to rule them all” kind of thing. I look forward to getting into some different terrain to find out just how it all comes together. But in the meantime, daaaaaang.

Handling Dynamics

Here’s where it gets sticky. And here’s where we get back to that old chestnut of leopards trying to change their spots, or something like that. While the suspension capability definitely improved, I can’t say the same for the handling. I think there are a few things contributing to this. First, the bottom bracket sits almost a centimeter higher. This means that the saddle is also a centimeter higher, and the entire center of gravity went uphill. Sure, when riding, in dynamic motion, that should all kinda relatively pan out, but my princess and the pea brain swears it feels “different” tipping into turns now. This may also be just one of those things I get used to. Or, maybe, I need to get some cranks that are 10mm shorter, then drop the bottom bracket back down, then see how things feel. But right now, it’s a thing I am trying to come to terms with that does not feel as awesome as it did before.

Secondly, I weigh 190. The Top Fuel, while not the lightest bike in the world, has a carefully built and respectfully lightweight chassis. The Pike, while having a whopping 1mm more stanchion diameter than a Fox 34, is also a relative lightweight. The bike feels more flexy now than it did before. Again, this may just be something I need to get used to, but it is something I am perceiving in terms of how the wheels follow each other when tracking through fast chunder or when trying to carve chattery turns. It doesn’t ruin the ride, but it does not feel more surefooted than before (except for the fact that the suspension DOES feel better than before and that helps mitigate what I think is going on with the handling). I suspect this is a sensation that varies dramatically dependent upon the weight and aggression level of the rider. I think I am, at my weight and ride feel preferences, more in the market for a shortened Fox 36 than a stretched out 34 or Pike. 150lb riders who tend to keep the wheels on the ground may never even notice. But big aggro people almost certainly will. Some will not care, others might. By comparison, the Transition Smuggler (130mm rear travel) and Privateer 141 that I just rotated through both felt ridiculously stiff and super planted. They also weighed something like five and nine pounds more, respectively.

Here We Are. Again.

Like I said, groundhog day. In some ways, this was a revelation. That Super Deluxe Ultimate shock is pretty damn impressive. The longer Pike holds its own. The Top Fuel has some raaaaange. But on the other hand, modern trail bikes are all getting heavy for valid reasons. Stretch the travel on light bikes and they start getting flexy. Hell, we didn’t even talk about how the stock Gunnison and Montrose tires that I felt favorably about in Colorado at 120mm travel suddenly felt like little death pucks at 130mm travel in the southern end of the Vizcaino desert. And how the brakes that kinda sucked before REALLY sucked once there was some super plush extra travel on tap allowing me to reef into the apexes a little hotter.

This all may come across like an overwrought bunch of hand wringing about compromise, again. I'm thinking my way through a conundrum that has been dogging me for decades. I am nevertheless impressed with how this particular part swapping experiment has gone. I can work with this.

I added half a pound of shock weight and gained a half a bike worth of added capability. The Top Fuel still climbs beautifully, it is ridiculously comfortable, and since I do not intend to start looking for new gap jumps to case, I can adapt around the flex and consider it a fair trade for how well everything else works. Which is a good thing. Because I’m in Mexico for three months, I went on record saying I was going to be bagging 10 hours a week of saddle time, and this is the bike I brought with me. So, in the spirit of the holiday just past and the second best Christmas movie of all time; “yippee ki yay, motherfuckers.”