Lightweight bike...any point?

Carlos13

It's nice to have a light bike, but does it make any difference to performance for the average rider? It might be fairly easy to reduce the weight of your bike by 1kg or 10%, but if you're a sturdy rider like myself it might only make a 1% difference to your total riding weight of 100kg. Are you really going to notice a 1% drop in weight that could be achieved in the toilet before riding? (well ok, maybe 1kg might be going some!). Is there any point in reducing bike weight by a kilo, then buying a camelbak with an extra litre's capacity in it's bladder?

Is there anything special about bike weight versus body weight? If so, can you explain what that difference is? I can understand the differences with rotational weight and the amount of torque required to spin a wheel, but this would not appear to apply to overall bike weight.

What I'm looking for is an explanation of why bike weight is more important than body weight, if indeed it is.

supersonic

It is still a kilo less, no matter how you look at it!

Placement of weight is one reason - a lighter bike is easier to move underneath you. Most people seem to find a weight which is ok, and any more is hard work. I find 30lb bikes very hard going, but 22lbs much easier, more than an 8lb difference would suggest.

Larger people need more strength and stiffness and can usually cope better with a slightly heavier bike anyway.

Carlos13

Why is it easier to manouvre if your weight is still bearing down on the bike? Or, to take my numbers as examples, is it only 1% easier to manouvre? The average rider won't notice a 1% difference will they?

I find 30lb bikes very hard going, but 22lbs much easier, more than an 8lb difference would suggest.

Why is that? Why does the 8lb difference count for more than 8lb?

supersonic

Like with a bowling bowl: no probs with a 12 pounder, 16 can't handle it at all. 10lb feels like a feather!

All I can say its try one a light bike out - it varies for us all and the feel is not as linear as you may expect. Again depends where the weight is, the COG, if it is rotating. There is no set rule.

BOYDIE

8lb is a big difference,you would fly up hills with out having to carry that extra weight lol.I feel that a lighter bike handles better in most situations,and a heavy bike IMO tends to wander off line a bit for me,Im only 10.5 stone.My current bike Ive managed to get down to just under 27lb for a full susser.

Carlos13

A 10lb bowling ball is nearly 40% lighter than a 16lb one, and that weight is entirely supported by localised muscles. I think for the comparison to be valid you'd need to sit on the ball and then tell me it felt lighter

Regarding centre of gravity, reducing the weight of the bike will always increase the CofG since the bulk of the weight (your body) is above the bike. Increasing CofG is normally bad for stability.

I'm not trying to be difficult, I've just never seen an adequate explanation.

Carlos13

BOYDIE wrote:

8lb is a big difference,you would fly up hills with out having to carry that extra weight lol.I feel that a lighter bike handles better in most situations,and a heavy bike IMO tends to wander off line a bit for me,Im only 10.5 stone.My current bike Ive managed to get down to just under 27lb for a full susser.

Presumably I could achieve the same effect - 8lb lighter - by not taking my Camelbak?

The question is: is 1kg on the bike worth more than 1kg on the body? If so, why?

supersonic

Lol, it was an example of how a few pounds difference can make a bigger impact than the numbers would suggest.

But from a physics point of view, the bike will accelerate and change direction quicker, climb better and usually a lot easier to bunny hop. I sling the bike around a lot on twisty courses, and it makes a difference to me. Again, where the weight is can make a difference to how noticable this is. Reducing wheel mass improves acceleration.

supersonic

Carlos13 wrote:

BOYDIE wrote:

8lb is a big difference,you would fly up hills with out having to carry that extra weight lol.I feel that a lighter bike handles better in most situations,and a heavy bike IMO tends to wander off line a bit for me,Im only 10.5 stone.My current bike Ive managed to get down to just under 27lb for a full susser.

Presumably I could achieve the same effect - 8lb lighter - by not taking my Camelbak?

The question is: is 1kg on the bike worth more than 1kg on the body? If so, why?

Fit panniers to your forks and fill with 8lbs of water. Will handle like a pig!

johnsav

my current HT weighs just under 24lb
my last one weighed about 31.5lb

do i notice a difference?

HELL YAAAAAA

Carlos13

What's the Physics explanation for why the bike performs better if the 1kg is off the bike, rather than off the body?

I'm with you on rotating weight, but forks, frame etc, why is weight here more important than body weight?

supersonic

Any weight loss is advantageous, no matter where from. But as the bike seems to move about a lot under me, especially getting it up and over obstacles and sudden changes of direction - seems easier with a lighter bike. With a bunny hop you lift the front end, then lift the back wheels with your legs.When cornering I lean the bike right over, and then maybe the opposite way in a split second - your body does not move as far when you lean!

Again, have a test and see how it feels.

zero303

Carlos, the bikes weight is well and truly outside of your muscular skeleton so you are trying to manipulate something which is 30lbs, but with just your limbs (and you're also trying to then support your own weight on the bike and balance).

Weight gains that are actually in your body or strapped closely to it are closer to your muscular skelton and your core and are spread out across the whole body. Whenever I hear people say 'oh I just take a dump before riding' I can't help but chuckle to myself as it simply doesn't work like that.

You still seem sceptical. Tell you what, add 8lbs to a camelbak and run up the stairs and then strap that same 8lbs to your ankles and do it... you will see a huge difference.

I'd say an average rider might not notice just a single pound spread out over a bike. However, a pound loss from say the forks will notice when lifting the bike over things or a pound less from the wheel set will notice a LOT. I recently shaved a pound off mine by going to a skinny XC tyre, I didn't notice the pick-up weight difference but once riding I noticed it but this was as down to it a) being weight loss, b) rotating weight loss at that, and c) it was just a faster rolling tread.

Carlos13

I have a Rockhopper which I modified by adding lightweight bars, stem, seat post and seat, saving about a pound in total. I think I can notice the difference when I lift the bike with my hands. It's possible that the knowledge of the weight loss makes the bike feel a lot lighter when I'm riding it. A bit like an expensive watch feels nice on the wrist.

I'm just after a more scientific explanation than "it just feels better", which you have certainly gone some way to providing zero303

The biggest difference came when I fitted lighter tyres, but then I could get my head around why this should be.

Stoo61

Just head out in the scud....fair fly up the hills.

supersonic

Reduced unsprung mass also makes suspension work more efficiently.

I see no reason for carting excess weight around on a bike. In a nutshell lighter bikes are easier to manoevre and take less energy to do so. Sure 100g saved might not be noticable, but save 100g on each component - it is then.

steveo450

I've got a 45lb bike and although i struggled at first due to my fitness.. Now I can climb pretty well with it generally keep up and sometimes lead on XC rides.

With regards to chucking it about.. On the tight twisty singletrack I can throw it around very easily. The bike doesnt feel heavy in the corners.

Dont get me wrong.. The weight is a git when going up. all depends what type of riding.

Recent trails I've done are Marin / llandegla / Whinlatter.. Not struggled at any where others with much lighter bikes have.


If I was only ever doing Fast XC rides then a lightweight bike is a must.

I generally ride anything and enjoy more the downhill / jumps / freeride style of riding. hence the heavy bike

Captain Turok

"Lightweight bike... any point?"

:shock:

Surf-Matt

Well I like my bike to go OVER stuff rather than THROUGH it!

Carlos13

Captain Turok wrote:

"Lightweight bike... any point?"

:shock:

I think there is a point, but I need(ed) someone to explain why. ie why is a pound off the bike worth more than a pound off the body. Most responses on here can be distilled down to "it just is". Well if it, is, what is the reason? zero303 came up with the most logical explanation so far.

supersonic

most responses seemed to me to point to mass location and movement of it!

Captain Turok

Carlos13 wrote:

Captain Turok wrote:

"Lightweight bike... any point?"

:shock:

I think there is a point, but I need(ed) someone to explain why. ie why is a pound off the bike worth more than a pound off the body. Most responses on here can be distilled down to "it just is". Well if it, is, what is the reason? zero303 came up with the most logical explanation so far.

Sorry I'm unable to give qualified explanation. But if you get the chance to try something lighter, give it a go yourself (friendly LBS?).
A lack of (a reasonable amount of) weight becomes quite aparent and it all makes perfect sense when your cycling.
I'm just to dumb to be able to expain it eloquently. I can't give you full explanation of gravity either, but I'm not floating away just yet.

El Capitano

I'm a weight-weenie. I've spent stupid amounts of money getting my XC race bikes as light as possible. Here's a few thoughts:

1. Lightweight. Cheap. Robust. Pick two of those.

2. I've got my FS XC bike down to around 22lbs. It's nice at that weight, but completely unrideable except on the smoothest of roads (Maxxix flyweight tyres at 330g each like to puncture a lot). You can go too far.

3. Rotational weight is where the most benefit can be gained and noticed. Ignoring item 2 above, look to reduce the weight of your tyres/tubes/rims.

4. Dont sacrifice comfort for lightweightness - especially if you do long rides. It's no used having grips that weigh 12g and a saddle that weighs 135g if your uncomfortable on them after an hour or so...

5. My Coiler-Dee-Lux weighs about 30lbs. It's virtually completely stock. I have no intention of reducing it's weight as it serves it's purpose like this.

TBH, it's all about what you want out of your bike and how much you want to spend really. I race 12 and 24 enduro races, so need the bike to be both light and comfortable. I have removed as much weight as possible, Ti and Alloy bolts throughout, carbon fibre bar ends, dremelled away excess metal on the chainrings. I'll not do any further work to reduce weight now as I know in it's current build, the bike is reliable - it took a pounding at SITS, but kept working, which is more than can be said for a lot of the bikes taking part.

Carlos13

supersonic wrote:

most responses seemed to me to point to mass location and movement of it!

Well, having re-read the thread again only one response attempts to explain why, everything else tries to explain what. But, I got the answer I wanted, one that appears plausible to me, and which corresponds to my own experiences of fitting lighter parts to my Rockhopper.

Don't get upset though Supersonic, I buy MTB products based on your recommendations, and continue to read your column in WMB. No disrespect meant to you!

In fact, a related question: I have two bikes, a Meta 5.5 and the Rockhopper, I find myself turning to the Rockhopper for the local flat trails around Peterborough, especially now it's winter (lower maintenance). Past versions of the SID fork are not well reviewed, mostly due to "flex", whereas the Reba is well thought of. It seems to me that the second hand market reflects this - you can buy used SID far cheaper than a similar Reba. Given that I ride the Rockhopper in mostly forgiving terrain, would it be a wise move to acquire a set of SID forks and reap the weight benefits, and not suffer the flex disadvantages because of the type of terrain I ride. Or are <09 SID forks just best avoided? Would it be bad to go from 100mm travel to 80mm on the Rockhopper? It currently has Tora 302 which I think are around 2.4kg. SIDs are not much more than half that...

supersonic

The SIDs do flex, but might not be an issue for the riding you suggest, and would be a useful weight of losing a big chunk of weight but keeping front end comfort. If a heavy rider (say over 90kg) the flex may be more noticable. Rebas have a very high stiffness to weight ratios, and as you say, the fork holds value.

If you want faster front end handling, 80mm would be of benefit, and the shorter fork is less flexy too. I use a 80mm Manitou Skarab on my Zaskar - it flexes, but I don't thrash it as hard as the Idrive. So works well for me (80kg fully laden).

Glad you like the column lol, and bizarrely an up and coming one is on theis very subject! ;-)

TonyWard

Carlos raises a fair point.

Here is a different way of looking at the same thing - is there ANY performance difference between carrying the same amount of fluid in a water bottle (=heavier frame) and in a camelback (=heavier rider). Notably most top XC racers and all road cyclists seem to favour bottles which would seem to indicate the weight is not worse on the bike than the rider.

Rotational weight does seem in a different category.

By the way, while I take the point about going to the loo before heading out, I'd be very surprised if anyone takes that decision on the basis of the weight of the bike they are about to ride

zero303

TonyWard wrote:

Carlos raises a fair point.

Here is a different way of looking at the same thing - is there ANY performance difference between carrying the same amount of fluid in a water bottle (=heavier frame) and in a camelback (=heavier rider). Notably most top XC racers and all road cyclists seem to favour bottles which would seem to indicate the weight is not worse on the bike than the rider.

Rotational weight does seem in a different category.

By the way, while I take the point about going to the loo before heading out, I'd be very surprised if anyone takes that decision on the basis of the weight of the bike they are about to ride

Believe me, I hear the 'toilet' logic all the time on here!

As for XCers not wearing camelbaks - probably a couple of reasons here. You can be passed new bottles when empty, camelbaks, while on the body, weigh a lot more than a bottle before you even put water in it. I suspect they chose to lose the camelbak more to it feeling restrictive around the body too - I know I always chose a camlebak on the MTB (ok I have no choice due to lack of bottle mounts but would still chose camelbak) and bottles on the road bike.

stevieboy

Yep, racing with a camelbak is a pain - I ditched mine after my first in favour of bottles. They are too tight when you really get the lungs going, loosening them becomes a pain on the singletrack.

As for the lightweight bike thing - a kg off the bike is better than a kg off the body. Don't know why, it just is from first hand experience.

I did a time trial two weeks running.

Week one - Dry, mid summer

Bike weight 29lb
Body weight 11st 1lb
Time over 6 miles 28 mins 10 secs

Week two - Dry, mmid summer

Bike weight 23lb
Body Weight 11st 1lb
Time over 6 miles 26 mins 21 secs

Now these are two results that I would call back to back as far as can be. Just under two minutes faster for a 6lb reduction (new bike).

However, since getting fitter and getting my weight down to 9st 12lb I can do the course in about 24 mins 20secs with the bike still at 23lb. But this has been acheived through blood sweat and tears.

joe1983

Just a quick point- body mass is usually somewhat proportional to strength for an athlete, or a least a fit(ish) non-oveweight bloke. So if I put on a stone not all will be dead weigh as some will be useful muscle - especially if training hard. A kg on the bike adds nothing, a kg of bodymadd will at least go somewhere to negating it;s negative properties. Plus it keeps you warm.

johnsav

good point ^

Northwind

To some extent it's got to be similiar to unsprung weight- the whole bike is effectively unsprung, with your arms and legs the springs.



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