Guerilla Gravity Smash Conversion

“Welll what’s the point of this?”

This was my primary thought as I contemplated converting the Gnarvana to a Smash. Once I had all of the parts in my hand I was questioning why. The weight wasn’t going to change very much. The shocks had the same eye-to-eye, albeit with different strokes. They can both take a 170mm fork. Holding the two different chainstay assemblies together suggested minor differences in pivot placement. The largest noticeable change (other than travel, which seemed to be down to shock stroke as much as anything) was the difference in chainstay length, with the Gnarvana having an extra 10mm over the Smash. Why so much work to drop a centimeter of travel on each end and tweak the geometry a few mm and a few degrees?

I carried on. Because tinkering with bikes is what we do.

Why would you?

Perhaps we should back up a few feet, and talk a bit about what we are talking about. For those of you that are unaware, Guerilla Gravity sells a few models of bike, but they all share the same front triangle. Within that constant, they are able to tweak each model by altering pivot locations, chainstay lengths and headset cups. In my instance, my bike started as a Gnarvana (the heavy hitting 29er model) and we’re converting to a Smash (the slightly less heavy hitting 29er model). You can see the two geometry charts below.

There’s nothing overly ambitious about the geometry of the Smash. My size 4, with the headset cups set to long, has a reach of 498mm, coupled to a 64.7 degree head tube angle (although, my particular bike is probably a tiny bit slacker due to the 160mm fork compared to the 150mm stock). Seat tube angle is pushing 77 degrees, and chainstays are hanging out at 440mm. Travel is 150mm in the rear.

The Nuts and Bolts – Obtaining Them

So, if you own a Gnarvana (or a Smash) and decide to go down the path of turning your bike into a different animal, Guerilla Gravity will send you a nice little package with everything you need to convert it from one to the other. For now, the Smash and the Gnarvana are the only two bikes available with the carbon chainstay, so, if you would rather have a Shred Dogg or Megatrail, you’ll also need to fork out for an aluminum chainstay kit.

Further to that, if you fancy some different parts to hang on your bicycle, Guerilla Gravity will bundle you up some parts to send along with your rear end kit. Need a fork or a shock? Perhaps some lighter/heavier brakes, wheels or tires? No problem. Just add it to your package and it will show up in the mail a little while later.

My package contained the seatstay assembly (which included a new hanger, fresh bearings/bushings already pressed into place, and even some new pivot hardware), and if I were paying retail that would have cost me US$495. The fine folks at Marzocchi provided me with a fork and a shock to complete my build. I also talked the GG folks into sending me an additional crown race, just to make fork swaps easier.

Ponderings on Forks

The fork was where the doubt really started. Out of the box, the Z1 coil is 170mm, which is within the range suggested for the Smash, but is also the same travel as on the front of the Gnarvana. It sure would have been easy to just leave that fork at 170mm, but how could I go to all of this trouble to convert the bike, only to wind up with the same travel up front via a slightly over-forked bike with a bit less travel in the rear? But then again, tearing apart a brand new fork just to drop 10mm in travel felt a bit crazy too. But if I leave it at 170mm, why not just run the Gnarvana? Thinking about this consumed a few days.

Another holdup was the lack of the correct oil. Now, as you might know, the Grip and Grip 2 damper are both designed to ingest the oil in the lowers. That bath oil that you put in the damper leg will wind up in the damper itself, by design. I have it on good authority, from the most trusted man in mountain bike suspension (top 5, anyhow), that you should worry about this, and you should use the correct oil. Not using the correct oil means that your oils are going to mix and things are going to happen. Good things? Bad things? Who knows. But things. Likely bad. Best to stick with the Fox stuff. The right Fox stuff. In the right leg, only. Use the other right Fox stuff in the left leg. Which you think they would sell directly to you…but no.

With the right oil taking its sweet time, I thought it would be no problem to catch the oil and plop it right back in the fork. And, it was. A problem. It was going well but somewhere along in the process I nudged the lowers from their finely calibrated oil storage position (tilted on a table with the coil spring box underneath). Oil everywhere. I’ll have to re-do everything once I have a bottle of the correct stuff. I captured enough of it to get me through a few rides, but I should get the right amount of oil back in those lowers.

Other than my impromptu oily slip-and-slide, adjusting the travel on the Z1 coil is actually pretty simple. The worst part of the job is removing the retaining ring that holds the coil shaft in place. That part sucks. So, for just a tiny bit more work than your typical lowers service you can have 170, 160 or 150mm of travel. Now, how awesome would it be if Marzocchi figured out a way to adjust the travel by pulling everything out of the top of the fork? If you could switch travel without having to pull your lowers…oh man, game over. If that were the case, you could run either the Gnarvana or the Smash with the same fork, just with a quick switch of travel each time.

You could probably do this as it stands, but if you’re me, having to do a full lowers service each time probably means that you’re not going to do it ever. As well, the Gnarvana deserves a stouter fork on the front (like a Zeb or a 38) so there’s another reason not to, right there. Those forks shine in the worst of circumstances, and the Gnarvana is a bike for the worst of circumstances. You’d also find yourself right back in that rabbit hole. Why would I set a fork to 150 or 160mm of travel when I could have 170mm at the exact same weight? Why am I swapping parts out in the rear only to run the same length shock with a slightly shortened stroke? Let’s talk about that.

Consider the Rear

Swapping the seatstays seemed pretty simple, so without looking at the instructions, I started pulling bolts and everything went smoothly until I got to the dropouts. The seatstay dropout pivot is a stout clevis that clamps around the chainstay. The outer (male) bolt pops out easily, but the inner (female) portion does not. I twisted and I turned and I bashed and some mystery washers started falling off the bike. I decided to have a look at the instructions. This was illuminating.

First, I figured out where the washers belong. Next, I figured out where I went wrong. GG suggests leaving the seatstay linkage bolts loosely installed while you remove the chainstay pivots. And this makes sense! Doing so prevents the seatstay from twisting, and makes sliding the chainstay pivots out (and in) much easier.

Once you have the seatstays out (and the brake and derailleur un-bolted), you just swap in the new seatstay and shock, reverse the process and you’re done. With a bit of practice, and with a fork prepped and ready to go, you could easily turn this job around in 30-60 minutes. I will put that to the test soon.

A thought just popped into my head. With 10mm less chainstay, things would probably be better with a shorter chain. I’m not going to worry about this. If you’re building up a Smash and thinking about a Gnarvana conversion at some point, you should.

First Rides

Hopping on the bike, my first impression was that it was smaller. Yes, everything is sitting a teensy, tiny bit lower (stated Gnarvana BB height – 347mm, stated Smash BB height – 343mm), and the handlebars are a bit lower (a theoretical 10mm), but the reach actually goes up as the head tube steepens! Why did it feel smaller?

Pedalling felt a little bit more urgent too. Not much, but a bit. I had the same amount of sag with both setups (within my margin of error for measuring such things), but this could also just be down to the feel of a different model of rear shock (I built the Smash with a Bomber Air). In speaking with Guerilla Gravity, they state that for the Smash, there is slightly less progression and slightly more anti-squat, compared to the Gnarvana. This plays out with how the bike feels. Similar yet different.

Taking it to the trails, it was a surprisingly different beast. It climbs better than the Gnarvana. Surprisingly so. It pedals better. It handles technical bits better. It just gets to the top faster.

Descending is different too. Not so surprisingly, there’s more feedback than the longer travel Gnarvana. But it shouldn’t feel this different! Where the Gnarvana plows, the Smash requires (and provides) a bit more precision. It’s certainly snappier in and out of corners. It also beat me up a little bit on fast, repetitive hits and I lost some of that holy shit cushion that I loved about the Gnarvana. Where I found myself wanting a slightly firmer top and middle end of the Gnarvana, I’m thinking I need to mellow the Smash out a bit by downsizing the spacer in the shock.

On one hand, none of this is surprising from a slightly steeper, slightly lower, slightly shorter travel bike. But it also shares 90% of the parts with its burlier brother, and if somebody tried to explain to me just how much of a difference there would be between these two builds, I probably wouldn’t believe them.

Final Thoughts

What next? I don’t exactly know. We’ve covered a lot of this bike already with the Gnarvana review. I’ll probably talk separately about the Z1 Coil, as I have a few things to talk about there even though Deniz beat the subject to death not that long ago. My Bomber Air Shock review is still steaming, so I don’t have much more to say on that. I’ll check back in at some point, talk more about how this bike rode and maybe speak a bit about the reverse comparison of going back to the Gnarvana.