simonsez

My apologies for yet another “this vs that” question!

So I think I’m down to either of those 2 carbon bikes and I wouldn’t mind hearing people’s opinions. Now because of the current Covid situation, bikes are pretty much purchased sight unseen (in Canada anyways) so I need to get this as right as possible or risk regretting this big purchase!

They are both the exact same price and they have very similar components but here are some differences that I can think of:

Drivetrain: The Sirrus has Shimano SLX and the FX has Shimano GRX-- not sure if one is better than the other.
“Suspension”: The Sirrus uses the “Future Shock” system and the Trek has the IsoSpeed decoupler in the seat tube and IsoZone handlebar and grips ----- again not sure which one is better here, probably personal preference, any insights?
Tires: Sirrus rides on 38s and the FX on 32s

I plan on riding mostly city paved roads but the occasional gravel bike path so I think both would work although the Sirrus appears to be more geared for off-road riding (so perhaps it's cushier but slower?)

Because I won’t get a chance to test ride (I know it’s crazy!) I do find that one big difference between these 2 bikes is the geometry, I’m just under 6’3” so I think XL would be the way to go on both bikes. I prefer a more upright riding position and if I understand correctly the Sirrus fits that bill more with a Reach of 398mm and a Stack of 687mm, the FX, on the other hand, has a Reach of 419mm and a Stack of 640mm. I’m no bike geometry expert but I believe this means that I would be much more stretched out on the Trek correct? If I go for the FX is it possible to “raise” the Stack?

Any opinions/insights would be greatly appreciated, thanks!

badger1

I'm in Canada, so yes: it appears that this new Trek FX is intended to compete directly with the Sirrus X 5.0.

I own/ride a Sirrus X Comp carbon ('19), which is essentially the same as the 5.0. It's a great bike, as I'm absolutely sure would be the FX.

On your questions.
1. FS vs. rear Isospeed: personal preference, I would think. I looked long and hard at the current carbon FXs, but I went for the FS precisely because I'm especially sensitive for various reasons to 'shocks' up the front end of the bike. The FS is very effective. I know that the rear Isospeed is as well, so you just have to decide which matters more to you.
2. Tire clearance: the Sirrus X frame will clear up to 42s. I run 32s on mine (road riding). I'm not sure what the clearance is on the FX; you'd have to check that with a dealer, if it matters to you.
3. Gearing range and quality: SLX (mtb) and GRX 11spd are pretty much equivalent in quality. For what it's worth, the gearing on the Sirrus 5.0 (42x11) is actually a bit 'taller' than that of the FX (40x11). Neither will affect your 'top speed' in any practical sense.
4. Geometry is different, as you say. Again fwiw, I find the positioning on my Sirrus to be a perfect compromise between 'aggressive' and 'upright'. Personal preference, obviously, but to my mind this is the crucial difference. If your preference is for a slightly more 'upright' position, go with the Sirrus. Yes, you can futz around with stem angles and bars to make the FX more 'upright' if you want, but if that's where you're going to end up why not just get the frame that 'fits' your preferences more effectively in the first place.

tl;dr summary: these two bikes are much of a muchness, imo. I don't think you could go wrong with either one. But if it's possible in the current climate, I'd wait until I could test ride; one will likely 'feel' more like 'your' bike than the other.

simonsez

Thank you for these detailed answers to my questions. Glad to hear that you're enjoying your X Carbon. Are you finding the 1x11 enough for most riding condition?

I didn't know the Sirrus could run with tires as high as 42, I believe the Trek website mentions max tire size for the FX is 35. To be honest I think I am leaning more towards the Sirrus but as mentioned in my original post I just hate having to buy an expensive bike without a proper test ride. I keep hearing that the business restrictions will start easing soon, perhaps I should wait a couple of weeks.

badger1

The Sirrus comes stock with 38s, and at least one poster in this thread successfully fit 42s, though I think clearance was/is pretty tight. A non-issue for me, though, because I use the bike as my 'road bike', with 32s.

As to 1x11: this is one thing, certainly, that you want to be sure of before lashing out money. I don't know about the Trek, but the Sirrus X frame is dedicated 1x; you can't retrofit a front derailleur later, as there's no provision for a braze-on nor for a front der. cable.

Me? I've always had a conventional double (2x10) on my road bike, but was attracted to the 1x11 primarily because simplicity/clean lines etc. In practice, I've not regretted the change at all. I've found the gearing more than adequate for my needs. Plenty low for climbing (which I like), and more than enough high gearing for me. And I do like the simplicity. Bear in mind, though, that I always ride solo -- I don't do 'group rides' -- so precisely matching cadence etc. is a non-issue for me.

That said, that really is one thing you want to be certain about before getting a dedicated 1x bike.

ecsuser

@simonsez I, like you had to purchase a bike without test riding it (I did test drive some 2019 models around the parking lot at the end of last season - but nothing big enough for me). I took delivery of a '20 Sirrus X 5.0 several Fridays ago. For comparison - I am 6'4 and 220lbs, I opted for the XXL (largely because of availability) and I could have lived with an XL. So I think you'll find the XL perfect. I came from a Schwinn 3x7 drive train and find the 1x11 adequate for all circumstances thus far. I ride paved and gravel trails. I really like the Future Shock and this light-weight bike just goes. I used to struggle to keep up with the girlfriend and her Sirrus X - now she can't keep up with me.

simonsez

Hey thanks for replying! Agree with you assessment, if I go with the Sirrus, it would probably be an XL. Did you get a chance to weigh your X? Curious to know the weight of their biggest size.

Not_A_Pro

I just recently purchased the Sirrus X5.0. There are a lot of great hybrid/fitness bikes to choose from and the Trek FS Sport Carbon was also on my "short list". I test rode them both before buying. I decided on the Sirrus because it leans a little more to off-road riding than road. It's also a little more upright which suits my own personal preference, and the standard tires are wider and designed for trail use while still being suitable for pavement. Compared to some bikes I find it to be a little bit "twitchy" but that comes with the geometry and just takes getting used to. I'm not a "serious" rider but I get out most days for a ride. I live in a moderately hilly area and have no concerns that this bike is not fast enough! It's the nicest bike I've ever owned.

simonsez

Thanks for the feedback and congrats on your new bike!! I'm still bike shopping but for financial reasons I've had to lower my budget a bit. I pretty much eliminated the Trek from my list and am now considering the Sirrus X 4.0 or the "regular" 4.0. You will see that I started another thread but I've had no replies yet. I'm basically debating if I should go Carbon with the 4.0 and upsize my tires to make it more trail-friendly or go with X 4.0 with the alloy frame, bigger tires and Future Shock.

Did you happen to test ride the 4.0 by any chance?

Thanks again!

Not_A_Pro

Thanks @simonsez, I am really enjoying it and I am about to go for a nice ride soon today :-)

The X4.0 also looks like a great bike. I didn't test ride one as I had already settled on the features of the 5.0 (I was actually almost decided on the X Comp Carbon just before the new X line came out). The biggest differences between the 4.0 and 5.0 are aluminum vs. carbon, Deore 1x10 vs. SLX 1x11, a minor tire difference, and only about 2 pounds. I like the general "idea" of the 1x systems. In theory the relative simplicity should result in greater reliability, though shift systems have probably long been perfected enough that this is more psychological than real for the type riding I do.

I found almost all hybrid/fitness bikes lean more toward road than trail. I think the type riding you do (and price of course) should dictate which one you choose. At least half my riding is on light trails, gravel paths, etc. so that led me to favor the Sirrus X line as they are one of the few that leans more toward light trail than road riding without incurring the extra weight of fork shocks. The Sirrus is also about the only hybrid using a 1x drive system.

MrChrome

Though you may have already chosen the bike for your riding needs, I bought the Trek and love it........I am currently customizing the bike with better handlebars (carbon with bar ends & narrower than the isobar) plus seat w/seatpost........I previously had a Paketa Magnesium road frame I converted to hybrid but it was a tad small and didn't have the upgrades I really wanted - thru-axle / tubeless ready with bigger tires for winter / disc brakes / frame size - so I sold it to my training partner and bought this........I looked over all possible bikes I was interested in and the Specialized Sirrus & the Trek were the only two on my short list; the Trek fit the bill and I was able to test ride it so I happily purchased the bike and have put over 130 miles on it in the first week of riding........

ozzyski

To answer your question whether a 1x11 is enough, I say yes. I have a 2018 trek dual sport 2 and I replaced my crankset so the bike can be a 1x8. Even with less gearing than a 1x11, I have no problems going up steep inclines even with my 2 kids and their burly bee trailer in tow.

sh00k

apologies if this has already been addressed but have you ridden both or either one of the bikes yet?

scbeano

I am on order for a Sirrus X 5.0, but am concerned it may not be up to regular trail/gravel use. My normal gravel trails are pretty big gravel and elevation changes. Any concerns about this? Thinking I might wait for the Flat Bar Diverge. Any thoughts? Thanks. I ride about 70% pavement, groomed trail, 30% gravel/muddy trail. Thanks!

Wanderer

If it were my choice, which it isn't, I would go for the 4.0..... I have an older Sirrus Comp, and love it....

With the 9 spd and a double on the crank, you won't be giving up much, and gain the carbon frame, more gear choices, and a great bike...you can probably even fit wider than the stock 32 tires, if needed.

I really like 9 spd, as it is slightly cheaper to maintain, and works great with a lot of choices. With that 11-34 cassette, and a compact double, you will have LOTS of gear choices. Enought to go fast, or climb trees.

MHO

badger1

My take -- and this is obviously in the abstract(!) -- would be this. If I planned to really bash around in/on gravel, muddy trails, even some singletrack, etc., I'd go for the E5 flat-bar Diverge, the 'Expert' version, provided the geometry worked for me. Remember, that bike has geometry that effectively follows current mtb trends: a very long front-centre (reach), combined with a very short stem.

Reasons? First, significantly greater tire clearance. Second, the more expensive of the two flat-bar Diverges has the Future Shock 2.0, whereas the Sirrus X 5 has the FS 1.5. The 2.0 version is properly hydraulically damped, and fully adjustable. I'm lucky enough to have the 2.0 on my bike (Specialized upgraded my defective FS 1.0 with this lovely warranty replacement); it really, noticeably works. The 1.0/1.5 ones work very well also, but there really is a difference.

If you don't plan on doing 'rougher' riding, but just occasional gravel/dirt roads or trails -- non-technical stuff -- then either will work fine. I don't find my Sirrus X Comp (now the 5.0) in any way limiting, but I no longer do 'roughstuff'; I'm mostly on-road.

denada

glad you made a choice you're happy with

i want carbon 4 components (1x) with an aluminum frame. even the carbon fork on my fx 4 makes me nervous. i know carbon is tough as **** these days, but you should see me lay my bike down while riding.

once i wear out my crassest and chainrings, i'll make the change. i keep it well oiled, but put over 2k miles a year on it so it can't be too long. plus i don't mind the current components at all. just never use the smaller chainring. i looked at the quick 2, but the fx 4 frame bit me to well. plus i got an insane deal on it, buying it in winter and coming once a week making a low ball offer i buy everything accessory and have any repair beyond me done at that shop, so my conscience is clean.

Awesomeguy

how much difference is their between the fx3 and fx sport, in the geometry?
I bought the fx3, but always wonder how much more aggressive is the sport variants?

MrChrome

- the geometry is just about the same, the only difference appears to be the FX 3 is aluminium and the 4 is carbon fiber.........I have the FX 4 and really like it but I've replaced everything except the drive-train.......it's pretty awesome now........

DarkSkyHUnter

The Q-Factor will be different. The stance is narrower on all the FX Sport Series. Only really an issue if you use the same pair of cleats between multiple bikes.

Awesomeguy

what did you replace specifically? What items , specifically ? just curious