Does Unsprung Weight Really Impact MTB Suspension Performance?

Not pro enough to notice.

very vague?????, a 500 gram increase in derailleur is nothing, 500 gram rotating tyre, hell yes.

In one of those Frameworks bts videos Niko talks about the carbon rear triangle replacing the original allow one. Says he was hoping the lighter weight would help suspension performance but was disappointed that he couldn’t feel a difference. But maybe a heavy cassette would be more noticeable?

Thanks Sspomer. But couldn't all of this just happen in the tire geek thread? At least it's not in Roumors.

In my experience, if you remove enough weight it can make a truly significant difference. Back in like 2017, I set out to drop as much weight off the rear wheel as I could, going from stock low-end everything to high-end everything. I dropped 700ish grams and it made a massive difference in not only suspension performance (it could flutter for the first time) but overall bike handling/feeling as well, enough that I've prioritized it on every bike since.

That was an a Devinci Spartan. I could've dropped more weight but stuck to an alloy rim and doubledown casing. I run a mix of SRAM X01/XX1 11spd, incredibly light stuff when paired with a decent wheel -- and 11spd parts are often heavily discounted.

When I saw the thumbnail I read it as "does vorsprung weight affect suspension performance"

@Vorsprung have you been hitting the carbs hard?

Whoa. 

Are we disputing the math or whether it’s worth chasing? 



 

Lol I did feel this needed to be broken out to its own thread - Neko Mullaly did a great video on weight here and came to the same ind of conclusion I did - 

There is a certain minimun weight of wheel/tyre/brakes etc most people need to run for the bike to ride well, and the only way to drop any significant amount of unsprung weight from those parts would impact performance far worse than anything you gained. As long as you have good tyres, wheels that are stiff and strong enough for you then you can try to save tiny bits of weight on the smaller parts but they will make no difference at all to how the bike rides. Unless you've optimised every single other part, and removed as much friction from the suspension as you can, then dropping weight from the weels/unsprung mass is probably going to do more harm than good

I have, thanks for noticing!

Hi everybody, for me really significant is basically  the rider weight.

Some people chase numbers. I only chase feel.

There's a difference.

Sounds like you're the ideal person to answer this one then! Can you go to a hardware store and pick up a roll of lead flashing, work out how much heavier a heavy electronic drivetrain and cheap hub are and tape/zip tie it to your frame as near the hub as possible? Then do a quick video with and without?! I reckon it'll be quite a difference over braking bumps/high speed roots 

I run 11 speed X0 cassettes in 10-42 for the weight saving and clearance, I feel a difference.

But the key thing is:

Sure, removing weight at the rim or tyre probably has more impact on suspension feel, but that directly affects grip, stability and durability in a negative way.

Losing weight at the cassette and derailleur has virtually no tradeoffs, unless you really hate that one cable and love the feeling of electronic shifting.

I'd argue that losing weight at the derailleur does have significant trade offs.  For me, it doesn't affect suspension performance, but when i get into the chunky, choppy, nasty stuff whether i run a heavy electronic or cable derailleur is a significant difference.  Â There's a lot less slop and bouncing of that derailleur.  So a light weight cable XT feels smoother, and I get less feedback from it slapping around, less chain slap, and feels in general much calmer in the nasty chunk.  I do agree that it offers no suspension performance difference, but the feel of that weight bouncing around is significantly noticeable. That's why I still run cables, especially on a bike with short chainstays, the difference in feel is pretty definitive. 

I have two wheelsets for my trail bike:
1550g wheels + 2.4 Exo casing
2100g wheels + 2.4 Exo+ front and DD rear
Overall, over 1kg of extra weight.
There are a lot of variables that make them change the on-trail fell drastically.
But with a heavier wheel, I always speed up the rear suspension rebound, otherwise it feels much more "dead".
Front one, I don't notice that much, but there is less weight difference.

I recently tried dropping unsprung weight and found there to be minimal impact for the cost when doing so with the drivetrain. After a deal on an XTR cassette (10-51) and a short cage XTR derailleur and chain came my way, my SRAM X0 Eagle with Shimano Deore cassette and chain (also, 12-speed) were replaced, purely to drop weight on the rear axle. The difference was so small that it wasn’t worth the investment and the XTR cassette creaked like the door to a haunted house. The short cage derailluer and slightly shorter chain helped quiet trail noise from the drivetrain, though. 

I had also been experimenting with a lighter tire casing up front (EXO+) and shortly after the somewhat failed drivetrain experiment, opted to go back to a DD casing on the front wheel. For the same tread and size, the trail feel was greatly improved with the DD tire. It tracked better and more support was available when aggressively pushing the front end. Tire weight has a fairly profound impact on bike feel, and I reckon even for the same amount as say, the drivetrain in my experiements, tires and wheels have a more notable effect. The issue is lighter tires tend to deflect and squirm more. I’ve found this an issue regardless of pressure, too. 

Anecdotal but dropping 100g on my cassette via going from a GX to an X01 was not noticeable to me. I’ve had friends say going from an NX to an X01 was noticeable though. 

I found swapping to a lighter cassette noticeable in how the bike feels, but I am not equipped to measure that difference, nor conssistent enought in my riding to time it

IMO, other things like rotational weight get way too much attention compared to unsprung weight. If I were racing, I'd focus a lot on reducing unsprung weight.

But... since I'm not a racer, I just get whatever's dependable and easier to live with.

time to swap to XO 7 speed on my trail bike now I guess

So the TLDR is that all the gearbox hype ("dude, so much traction") is just hype? 

This season I switched over to a Zerode Katipo; gearbox belt drive setup. The rear end tracks exceptionally well likely due to a combination of factors; low CM of the gearbox, quiet belt, minimum unsprung mass on the rear end. Most satisfying gravity oriented bike I've owned.  Switching back to normal derailleur rigs I mostly notice the chain noise and resonance of the long, oscillating derailleur and cage.  

I can't help but think derailleurs are effectively Untuned Mass Ocillators (TM) that can negatively impact the perceived feel and smoothness of the rear suspension. Everyone knows how satisfying a really quiet bike is, so maybe worrying about quieting down the drivetrain  before sweating 100g of derailleur battery is the bigger tangible improvement.

It's kind of funny seeing this discussion when the ideal solution already exists in the form of the pinion belt drive setups. The combination appears to be solving all of these issues. 

TBH, I've ridden a bike with suspension that was glued to the ground and it pretty much trivialized the challenge in the trail. It encouraged me to go even faster, to the point that I was back to the limits of traction, to feel like I was progressing in skill. When I said it felt dead to others, and they asked for details, they insisted that was what suspension was supposed to do.

I went back to suspension that bounced and found it "playful", and felt more at peace perhaps because it was familiar and felt like I didn't have to take risks to have fun. I never expect to have a trail all to myself, unless I'm paying to race, and didn't want to make others feel like they have to get out of my way since I'm going so fast and have questionable control. I wasn't willing to pay $$$$ to get the real suspension, thinking there could be some sort of balance between the two for non-competitive use.

damn dude you could’ve searched out bigger trails on that hovercraft—sounds great!

Ground hugger. It feels different on SoCal loose-over-hard than you'd expect, and even weirder taken up to higher altitude forests on composty duff.

With some sense of the ground gone, it leaves you sensing the suspended part of the bike, which means that sensing the bike's geo changing becomes so heightened that it dominates your thoughts. You start to feel like the bike rides a little low, going kinda deep on dips and other kinds of G-outs.

It's not too unlike feeling like having a silent freehub would be amazing, allowing you to hear the tires scratching for traction, but reality is different. Wind noise becomes so noticeable that it seems deafening loud, and all sorts of other noises on the bike become far more apparent, like chain noise.

Personally, I think I like extra feedback through the wheels. When I ran Industry 9 wheels with alloy spokes, it was able to feel so much of the ground. That was when I was riding at my limit. I think the way I prefer to ride now, that extra feedback would simply be unnecessary noise that affects my comfort and ability to have a more chill pace/vibe.

It's not how much it weighs. It's how you use it. 

That's what she shred. 

Pretty sure.