5 lb weight difference - how significant?

Bike Forum

[closed]

5 lb weight difference - how significant?

79 posts & 34 voices | Started 1 year ago by bonesetter | Latest reply from jamesb

Tags:

No tags yet.

Pages: « Previous 123 Next »

cynic-al - Member

FWIW though I agree with most of what you said- racy frame angles are generally found on light builds/ cruisier angles on more robust builds- and I think that's why a lot of people expect light weight to equal a faster bike, when in fact it's that the design males it a more efficient pedalling machine.

I still disagree - angles can make a bike feel faster, but make it physically more efficient? I don't think so.

Al - it makes a HUGE difference to me.. but we are just different riders it seems

In real terms i.e. time? And who says I ride? I'm just a forum-troll-bot come armchair-engineer come TROLL-BATTLING-EPIC-LEGEND.

Posted 1 year ago #
GW - Member

TROLL-BATTLING-EPIC-LEGEND.

What happened on that thread in the end Al?

Posted 1 year ago #
vinnyeh - Member

@GW, I didn't phrase that very well, did I. Of course you're right, and 5 pounds will make a big difference, especially on wheelset changes, though I've never been able to lose that much weight off a bike.
What I'm trying to say is that people often focus on the weight difference between two frames as the source of the difference, rather than the geometry.

Posted 1 year ago #
GW - Member

I could lose 5lb off every bike I own fairly easily but I wouldn't want to ride it afterwards, durability is as important to me as weight on a bike build.

Posted 1 year ago #
molgrips - Member

I still disagree - angles can make a bike feel faster, but make it physically more efficient? I don't think so.

It does. A whippet flat back position uses different muscle groups to a sit up and beg one. That's why gym exercise bikes are cack. Also why time trial bikes have steep angles.

In real terms i.e. time?

Dunno, but it sounds like you don't go flat out on singletrack as a matter of course...?

Posted 1 year ago #
vinnyeh - Member

I still disagree - angles can make a bike feel faster, but make it physically more efficient? I don't think so.

more efficient to pedal was what I meant.

Posted 1 year ago #
sheldona - Member

5lbs = 1/100 Singlespeedstu

Posted 1 year ago #
robhughes - Member

wish my 08 wolfridge weighed 5 lbs less.

Posted 1 year ago #
Trent Steel - Member

GW - Member

vinnyeh - Member

racy frame angles are generally found on light builds/ cruisier angles on more robust builds- and I think that's why a lot of people expect light weight to equal a faster bike, when in fact it's that the design males it a more efficient pedalling machine.

Think you're wrong! Take 2 identical 4X hardtails. use the exact same same light weight (4.5lb) Alu frame, build one with XO/Reba/ProII/717 and light dependable finishing kit the other with old Saint/Argyle/721 and average DH worthy kit and you'd have one 25lb bike and one 30lb one. both as efficient pedalling as each other but with the same rider on board the light one would make up a bike length out a start gate, change direction faster and be more manouverable. take them both on a proper DH track and although less manouverable the heavier one will be easier to control.

How about take 2 different frames of the same weight, one racy and one slack and put the same kit on each, would they feel the same? No.

The answer is weight and geo both make a difference, why do all these threads just turn into black or white disagreements when the world is grey

Posted 1 year ago #
Scienceofficer - Member

Because its full of internet heros who know theirs is the one true path?

Posted 1 year ago #
R.lepecha - Member

well, a 36lb hardtail my end, rides better than my lighter full sus and my mates lighter hardtails, i say just mtfu and get on with it

Posted 1 year ago #
GW - Member

the thread's about weight, trent

Posted 1 year ago #
cynic-al - Member

GW it got pulled, I remain mystified as to why.

"It does. A whippet flat back position uses different muscle groups to a sit up and beg one. That's why gym exercise bikes are cack. Also why time trial bikes have steep angles."
sit up and beg vs. TT bike maybe. A few degrees on mtbs I disagree.

Posted 1 year ago #
mtbtomo - Member

I think geometry does make difference, I've had fairly similar weight hardtails before but one was horrible up hill because the geometry put you in a bad position in relation to the pedals and it felt like I was using different muscles.

A bike with DH geometry will feel different efficiency wise, even if it's the same weight as an xc geometry bike. On mtb's you get bikes with head angles that are different by as much as 8 or 9 degrees, which is more than just a few degrees? Short or long top tubes will make a difference. It all affects how much you can expand your rib cage when breathing surely?

Posted 1 year ago #
buzz-lightyear - Member

That's why gym exercise bikes are cack

The upright position is less efficient. But consider that they generate no motion which means they are 0% efficient!

Posted 1 year ago #
molgrips - Member

why do all these threads just turn into black or white disagreements when the world is grey

The world is pretty grey this morning, quite right

If you scroll back though, you will see that I did in fact acknowledge that both weight and geometry are both important

But consider that they generate no motion which means they are 0% efficient!

I meant in terms of power generated versus perceived exertion.

A few degrees on mtbs I disagree

I don't. My bike feels quite different if I move the saddle forward or backwards. To pedalling style and weight distribution - your weight is not only further forwards but you have to raise the saddle if you move it forwards which puts your COG higher. And if it's full sus, there's less weight over the back wheel which changes how the suspension behaves and how you can set it up....

I love details

Posted 1 year ago #
cynic-al - Member

My bike feels quite different if I move the saddle forward or backwards. To pedalling style and weight distribution - your weight is not only further forwards but you have to raise the saddle if you move it forwards which puts your COG higher. And if it's full sus, there's less weight over the back wheel which changes how the suspension behaves and how you can set it up....

Precisely none of which has been established to make the bike go faster.

Posted 1 year ago #
SpokesCycles - Member

I think it's a reasonably well accepted fact that Cynic-Al thinks weight makes sod all difference, but in reality 5lbs is a lot and the weight (along with other factors such as geometry and tyres) will make it noticeably slower.

GW is right. I'm going to add "sciencefact" to that, so I guess that's this argument shut.

Posted 1 year ago #
rkk01 - Member

I remember mols posting his power output calcs... on a thread about climbing times / rider / bike weight???

On the the same thread I posted average commute times for the bikes I had run over the last 5 or so years. Two of those bikes were similar weight hardtails - a lightly built L / 19.5" Pace RC305 and a similar weight 21" Airborne Lucky Strike. Both weighed in at between 23-25lbs depending on wheel / tyre combos fitted at any given time.

Airborne always felt way faster than the Pace, except on more technical descents, where the very long stretched out geometry became too prone to over the bars moments...

Commute timings bear this out too. Airborne was 5-10 mins per hour quicker than the Pace.

I'm not arguing all for geometry - just countering the "geometry doesn't affect efficiency" trolling

5lbs difference on the bike is huge - 5lbs on the body / in the Camelback will be more tiring over the day, but doesn't affect the ride in any way the same manner.

Posted 1 year ago #
PJM1974 - Member

So why am I less knackered after riding my 34lb AM bike over a long distance than I am on my 28.5lb XC bike?

Pedal efficiency has a lot to do with it.

Posted 1 year ago #
cynic-al - Member

Luke, your opinion trumps mine, even though mine is backed up by tests?

Posted 1 year ago #
crikey - Member

Nice to see cyclists still regard the bicycle as independent of any of the laws of physics...

Posted 1 year ago #
molgrips - Member

Don't talk to me about laws of physics! Studied them for four years! What I am doing is applying those laws to the handling and performance of our bikes.

Out of interest, what do you consider 'bugger all difference' to be? On a 10 minute fire-road climb, if someone gets to the top 30s ahead of someone else, that's a fair old difference when you're racing your mates, but it's only 5% in quantitative terms...

Posted 1 year ago #
cynic-al - Member

Say 5lb of 25 (bike) + 155 (rider) is 2.75%, a direct gain on climbs, where say you spend 40% of your time in an xc race, making you 1.1% faster, 1:12m faster in a 2 hour race.

Posted 1 year ago #
crikey - Member

What I am doing is applying those laws to the handling and performance of our bikes

...and describing the effect in terms of 'massive' or 'huge' or 'the size of an elephant'....

...and convieniently ignoring the huge camelbak, the STW weight rider, the baggy unaerodynamic clothes to claim that a small reduction in overall weight makes a difference to you going at the speed of light through singletrack.

Posted 1 year ago #
chiefgrooveguru - Member

I think the main issue is that it's partially unsprung weight if it's on the bike, whilst if it's part of the rider (and you're riding competently) that extra mass is travelling with a flatter smooth trajectory.

Anyone will two bottle cages on their bike and a Camelbak could experiment with this by carrying water either on the bike or on their back, and then attacking some singletrack and seeing how it feels. However, if you're not riding actively then your weight will be less well sprung and you might not notice the difference.

Posted 1 year ago #
SpokesCycles - Member

Al- I used the words sciencefact, did you not see?

Posted 1 year ago #
molgrips - Member

...and describing the effect in terms of 'massive' or 'huge' or 'the size of an elephant'....

Yes. It depends on what you mean by huge. See my above post.

Do I think it'll make you 15 minutes quicker up the Afan climb? Of course I bloody don't.

...and convieniently ignoring the huge camelbak, the STW weight rider

The fact that you think I'm SO stupid to have actually overlooked the relative weights of rider and bike doesn't reflect well on your own powers of thought and ability to follow an argument on intelligent terms.

The most simplistic angle is to calculate 5lbs as a percentage of total bike+rider weight. I'm saying that there's a lot more to the physical model than that, but perhaps more importantly the human interpretations of the consequences of the variables in that model are quite subtle.

ONE example being that if you finish a 5hr enduro 5 mins before someone else, that's a sizeable victory, but a pretty small percentage of time.

Have a read and a think, you might learn something from all the valid posts on this thread that don't insult the posters.

And yes I know I am being insulting and antagonistic, but I'm annoyed.

Posted 1 year ago #
cynic-al - Member

AH OK Luke so you are ****ing about.

The most simplistic angle is to calculate 5lbs as a percentage of total bike+rider weight. I'm saying that there's a lot more to the physical model than that,

...which makes even less real difference than the 5lb. And 5m in a 5 hour race, 1.8%, I wouldn't call it a significant victory at all.

Sorry mate, it's guff.

Posted 1 year ago #
molgrips - Member

...which makes even less real difference than the 5lb. And 5m in a 5 hour race, 1.8%, I wouldn't call it a significant victory at all.

I would. Plus that was only one example of the many aspects of the issue.

Sorry mate, it's guff.

No it's not.

Posted 1 year ago #
cynic-al - Member

Yes it is.

Posted 1 year ago #
molgrips - Member

No it's not.

Posted 1 year ago #
sheffield43 - Member

Don't know if anyones said this already as I couldn't be arsed to read through all the science and pseudo science but how much the rider weighs must make a difference - bigger heavier rider it'll make less of a diference. 7 stone rider it'll make a huge difference, 14 stone rider much less of a difference.

Posted 1 year ago #
cynic-al - Member

110% guff!

Posted 1 year ago #
molgrips - Member

Peak power of the rider makes a difference too. If you can put more torque into the pedals at any given instant, you're more likely to be able to get a 35lb bike moving in two or three pedal strokes after a hairpin.

Posted 1 year ago #

RSS feed for this topic

Pages: « Previous 123 Next »

Topic Closed

This topic has been closed to new replies.

Singletrack Mountain Bike Magazine

Bike Forum

5 lb weight difference - how significant?

Topic Closed

Don't miss…

Singletrack

Website & Forums

Exits