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Guy Jinbaiquerre
22-05-15, 07:30 PM
For the average rider (i.e., not a professional racer), is there a meaningful performance benefit to replacing the ordinary plastic/fiberglass parts on a sportbike with carbon fiber to save weight? What about at the professional level? How much weight does carbon fiber bodywork really save, and does it matter?

Seems to me that unless you're replacing solid parts like metal wheels with carbon wheels, it wouldn't make much difference.

(Just asking out of curiosity... not planning to carbon fiber-ize the GS.) :icon_lol:

Markw
22-05-15, 10:25 PM
For the average rider (i.e., not a professional racer), is there a meaningful performance benefit to replacing the ordinary plastic/fiberglass parts on a sportbike with carbon fiber to save weight? What about at the professional level? How much weight does carbon fiber bodywork really save, and does it matter?

Seems to me that unless you're replacing solid parts like metal wheels with carbon wheels, it wouldn't make much difference.

(Just asking out of curiosity... not planning to carbon fiber-ize the GS.) :icon_lol:

I think you'll find most plastic parts are a similar weight to carbon fiber. Fiberglass parts wil be heavier. The advantages of CF are it looks cool, is stiff, damps vibration well and is lght weight. Disadvantages are it is expensive and scratches relatively easily.

CF wheels are considerably lighter than aluminium wheels (about 50% less) and probably the best performance improving CF parts you can purchase for a sportbike, although not cheap at about $4,000 for a front & rear set.

rtfm
23-05-15, 09:11 PM
For the average rider

No, it won't. you will be talking about a few kilograms (maybe) on a 200+kg machine. The wheels will make a difference to the acceleration (less rotational inertia) but no difference to steady driving and you can get a new scooter for the same money. Unless you go full-out with aluminum / magnesium / titanium drivetrain parts, remove the HID hibeams, navi, rack, box, ETC and everything else that consumes space you will just be lightening your bank account.

There's some company that makes kevlar-wrapped brake lines. They outright refuse to sell them to non-pro race teams despite huge demand. Kevlar is both stiffer and a lot lighter than steel, but it doesn't handle abrasion very well. The race teams replace the kevlar lines every race. Very few average riders are willing to do a full teardown after the weekend out.


... and a Lithium battery

Ooh, yeah. Forgot about this one. Batteries, being a box full of lead, obviously weigh a lot. The lithium ones are so light (the lithium content weighs less than the plastic container) that you wonder if there's actually a battery in the box when you pick it up off the shelf. There's your carbon-fiber body panel weight savings for a lot less cash and work.

Doug68
23-05-15, 09:41 PM
Carbon wheels are banned from most race series due to failures that happened when they first appeared, which look like they are sorted now.
There's big weight you can remove from a bike without using carbon, that's the icing on the cake and not where you start.
At the track I'd say it makes a difference whoever you are, but being able to measure that is a difficult thing.
On the road MEH.

Neilb
24-05-15, 11:37 AM
Carbon looks cool and is a bugger to repair. Titanium Exhaust and a Lithium battery (And a visit to the toilet before riding) will make a big difference

Doug68
24-05-15, 03:14 PM
I got one of these for my track bike:

http://shop.antigravitybatteries.com/antigravity-batteries-sc-1/

That was 2.5kg saved right there, when you start getting serious about weight saving it turns into $ per g saved, in this case about 6 cents a gram, which is great value for money, on the other end of the scale were the titanium brake rotor bolts that were $2 a gram. But the OEM ones looked crap so had to go ;)

Lucky Pete
25-05-15, 09:04 AM
For a lot of people the easiest/cheapest way to get ahead on the weight/power ratio is often ignored or overlooked. Go on a diet, get fit and lose weight. No only will you go faster but you may also live longer. By cutting down on crap food and booze you'll also save $, not be spending it. If you are already that way then its the bike.

Guy Jinbaiquerre
25-05-15, 10:27 AM
Good answers on this post, thanks everybody.

I am wondering, though: Everybody acknowledges that lighter weight is good for handling, but at the same time, most people say that saving just a little bit of weight doesn't really make a difference unless you're a pro racer. So the question then becomes, at what point do weight savings start to make a noticeable difference for the average casual rider?

For example, most people would agree that a heavy bike like my R1200GS Adventure, while it may have many good qualities, is not going to handle as nimbly as a much lighter bike like the MT-09. That's a 46kg difference in wet weight, though (256kg vs. 210kg). Would you notice a difference about half as large, i.e., 23kg? How about 10kg? 5?

My guess is 20kg is probably the point at which weight saving starts to become noticeable; interested to hear what other folks think.

cmac
25-05-15, 11:29 AM
Weight reduction is always a prefered and noticeable performance upgrade. Generally cheap too as you take stuff off to achieve it. Usually results in reduced function and useability though.

Where you remove weight is most important. Wheels and extremities tend to show the greatest benefits. Adding weight up high, hanging off the front or way out back is a good way to reduce the handling capabilities of a bike. Ever experienced how a loaded givi box hanging off the back feels like the tail wagging the dog in the twisties?
But weight reduction alone isn't the end of the story. Removing 5kgs from the front of your bike by replacing a heavy steel stay means you've altered the balance of the bike and will need suspension adjustments to rectify that.

Another avenue is spending more and using alternate materials like carbon or titanium which of course is expensive but does tend to look cool and generally offers added durability or function. I bought a carbon front fender to replace a crash damaged stock item. It has been quite durable having survived 2 crashes since. :D Also tried some titanium rotor bolts that are reuseable where the OEM ones are not.

How much is a good reduction in weight? That is subject to the bike, intended use and most importantly, where you remove the weight. If you are an adventurer, better to pack light and add light weight accessories and position them well.
Want more? Best to switch package and maintain balance and useability.

Lugn
25-05-15, 12:08 PM
In my experience, I would say that it highly depends on the placement of the weight. Hauling 5L of milk and groceries in your top box will be noticed before a 10kg addition to the bottom of your engine block.
Rotating weight will also be more easily noticed, hence the desire to reduce weight on wheels, certain engine components.

The pursuit of an engine mounted front to back in the frame, with two crankshafts rotating in opposite directions is exciting from a pure theoretical point of view. Would love a test drive to see what it means in reality.

Doug68
25-05-15, 12:35 PM
My track bike is roughly 25% lighter than the quoted wet weight of a stock one, with stock wheels and no carbon involved.
You're not going to achieve that with a street bike, but probably 10% or so should be doable without going mad.
The bike should be better in all respects, the question is will you really notice it? I'm not sure, but effectively you'll be getting 10% more power 10% better brakes, 10% better everything (caveats on set up) (And 10% less to drag out of the ditch when it goes wrong ;) ). Which if it gets you excited is worth doing just for the fun of it if nothing else.

Adeonhisown
25-05-15, 01:28 PM
I guess it could be argued that an average rider wouldn't notice the weight difference in handling/ cornering if they obey speed limits, but I'd wager stopping distance and acceleration would be noticedable if you talking anything more than a few kgs getting near the 5~10% of bikes total weight (all else being the same) and in longer terms fuel savings maybe.

Jav
26-05-15, 02:28 AM
Throwing in my $0.10.

Changed side fairings & seat section on a Ducati 1098 and 1198. Holding the stock and carbon parts
( individually ) in hand, the difference felt around 4kgs per part ( i was amazed at how heavy the stock
parts were ). The bike with the carbon parts definitely felt lighter. Loosing 12kg on bodywork and another
6 to 7 kgs on a pipe is not insignificant.

Loosing weight on a bike, while the rider stays the same weight, will make a difference. The bike will require less
effort to control. Are carbon parts worth the cost? Depends on how much you value the weight savings and looks.

Another interesting point on rider weight, four riders ( me included ) rode a 250cc race bike ( 45hp ) in a race last
October. There was a 25kg difference between the heaviest and lightest rider. Two Japanese riders weighing in at about
65Kgs and two Aussies weighing in at about 90Kgs. All riders had similar abilities and interestingly
all riders were within 0.3 seconds of each other ( the heavier riders were actually the faster ). I am not sure if it is
provable or not, but I believe the bike weight is much more significant than the rider weight.

Adeonhisown
26-05-15, 09:03 AM
). I am not sure if it is
provable or not, but I believe the bike weight is much more significant than the rider weight.

I would assume, it is all to do with weight placement. As the riders can move having a heavy thing hang off the side of the bike in a turn would mean the bike didn't have to lean as much, hence better angles for cornering. The acceleration and deceleration surely must be different, but as the heavier riders can take more speed into a corner, less braking would be needed. Therefore the weight differences must cancel eachother out.
(I have No racing experience, this is purely guesswork.)

But I also remember from uni that I HATED dynamics classes, everything is completely counter intuitive.

Adeonhisown
26-05-15, 09:06 AM
https://youtu.be/cB8GNQuyMPc

If there are any engineers on here that didn't have hangovers though their dynamics classes, watch this to make you think that solid steel wheels should be better for motorbikes...

Twinrider
26-05-15, 09:10 AM
All riders had similar abilities and interestingly
all riders were within 0.3 seconds of each other ( the heavier riders were actually the faster ). I am not sure if it is
provable or not, but I believe the bike weight is much more significant than the rider weight.

This article analyzes MotoGP rider weight/success and concludes that ability matters more than rider weight. :-)

https://motomatters.com/analysis/2011/04/13/number_crunching_how_much_of_a_factor_is.html

Guy Jinbaiquerre
26-05-15, 09:25 AM
This article analyzes MotoGP rider weight/success and concludes that ability matters more than weight. :-)
The main point I took away from that article is that I am taller than the average MotoGP rider. :icon_cool:

Seriously, though, the question is whether shaving weight off the bike (or the rider going on a diet) will make a rider faster or better-handling than HE HIMSELF was when he and/or the bike weighed more. This is a very different question from whether a lighter rider will tend to beat a heavier rider (which is what that article focuses on).

When you're comparing two different riders, obviously one may be more skilled than the other, and that difference may be enough to overwhelm any improvement from reducing the weight of one rider and/or bike. But just because weight reduction may not make Rider A faster than Rider B, that doesn't mean that weight reduction won't make Rider A faster than he used to be.

Twinrider
26-05-15, 09:55 AM
Seriously, though, the question is whether shaving weight off the bike (or the rider going on a diet) will make a rider faster or better-handling than HE HIMSELF was when he and/or the bike weighed more. This is a very different question from whether a lighter rider will tend to beat a heavier rider (which is what that article focuses on).

Yes, I posted that article as a comment on rider weight, which Jav brought up. I edited my post to make that clear.


But just because weight reduction may not make Rider A faster than Rider B, that doesn't mean that weight reduction won't make Rider A faster than he used to be.

That would stand to reason.

Guy Jinbaiquerre
26-05-15, 10:27 AM
That would stand to reason.
Darn, I was trying to figure out how much I'd need to weigh to beat Rossi. :icon_lol:

rider2371
26-05-15, 02:17 PM
Interesting thread.


My guess is 20kg is probably the point at which weight saving starts to become noticeable; interested to hear what other folks think.

From my (limited) experience, I'd say you might be on the money. From about 15~20kg, the weight difference starts to be noticeable on my GS. Given my GS is somewhat comparable in weight to your GSA, I'd predict you would start to feel the difference from about the same figure.

Having said that, it's easy to imagine that a 20kg weight difference in a 100+hp 240kg (a GS or GSA) bike is going to feel less significant than the same weight difference in a 25hp / 140kg DP bike (and XR250 or CRFL). So the the point at which weight saving starts to become noticeable depends on the size/weight of the bike and the power/torque it makes.

The first time I experienced this weight difference was after I took the bike through its first round of mods: I added low and high crash bars, replaced the screen with a heavier/bigger one, added a bunch of Al protectors, an auxiliary rear mud guard etc. I think I must have added between 15 and 20kg altogether. The bike immediately felt heavier in acceleration and cornering. Fuel economy took a hit from avg 21km/L down to 19km/L, but improved to 20km/L after I started increasing air pressure in the tires.

Consider also the side cases and the top box. My vario side cases each weight about 8~12kg depending on how much stuff I have in them. Fitting both cases loaded adds about 20kg of weight to the rear (without top box). To accommodate the extra weight, I adjust my ESA setting accordingly. Nevertheless, the GS feels noticeable heavier and riding tight twisties becomes a lot more tiring. Adding a loaded top box adds another 15kg or so to the rear and moves the bike's center of gravityeven higher, making it even more tiring to pick up the bike out of a corner.

I think it would be quite an expensive exercise to try to achieve a 20kg weight difference using carbon fiber.

Guy Jinbaiquerre
26-05-15, 02:31 PM
I think it would be quite an expensive exercise to try to achieve a 20kg weight difference using carbon fiber.
It would vary from bike to bike, but basically I think you could save weight like this (note that these numbers are pure guesses):

Lithium battery: 3-5kg
Titanium full exhaust: 5kg
Carbon fiber wheels: 5-8kg
Carbon fiber bodywork: 3-6kg
Titanium bolts, etc: 2-3kg
Stripping off unnecessary parts (pillion seat, etc.): 3-5kg

So there's definitely potential to save weight out there... but eventually it becomes a matter of cost.

Markw
27-05-15, 09:06 AM
It would vary from bike to bike, but basically I think you could save weight like this (note that these numbers are pure guesses):

Lithium battery: 3-5kg
Titanium full exhaust: 5kg
Carbon fiber wheels: 5-8kg
Carbon fiber bodywork: 3-6kg
Titanium bolts, etc: 2-3kg
Stripping off unnecessary parts (pillion seat, etc.): 3-5kg

So there's definitely potential to save weight out there... but eventually it becomes a matter of cost.

I think your estimates are over optimistic. About half your numbers would be appropriate for the majority of bikes...

Doug68
27-05-15, 10:11 AM
Using just one example for a 2007 GSX-R 1000 Akrapovic claim their full race system will save 9.05kg.

http://shop.jamparts.com/pdf/GSXR%201000%20REL%20single%2007.pdf

There's a myriad of other places to save weight, most weight reduction comes from lots of 100g to 500g gains put together.
Another point is things you might change for other reasons are often lighter than the stock parts, for example I fitted a Ohlins steering damper as the stock one was freaking me out, that saved 200g right there.

Guy Jinbaiquerre
27-05-15, 11:33 AM
There's a myriad of other places to save weight, most weight reduction comes from lots of 100g to 500g gains put together.
Yep. Just for fun, here's an X4 owner I used to ride with (he dropped out of sight a few years ago after getting married :sad:) who first was bolting on whatever extra parts he could find, but then got the weight-saving bug and started stripping stuff off and lightening what he could -- sometimes in big chunks, sometimes gram by precious gram. He ended up getting it down to 64kg below the stock weight:

http://www.geocities.jp/x_4_custom/


That's almost one-fourth of the stock bike, gone! He carefully measured the weight of every part he removed versus the replacement, if any. Sometimes he went back and replaced a particular part again when he found something lighter. He even had custom one-off parts molded out of dry carbon fiber, because ordinary carbon fiber has extra weight from whatever plastic sealant they put on it to make it shiny. Probably the most extreme change he made was modifying the frame and swingarm, including changing the bike from twin rear shocks to a monoshock. Insane.

NOTE: He poured ridiculous amounts of money into this project. I don't recommend it unless the Internet company you founded just went public.

Markw
27-05-15, 02:39 PM
Yep, this obviously depends on what components the stock bike comes with. If it comes standard with lightweight component reducing a significant amount of weight is going to be a lot harder and more expensive...

rider2371
27-05-15, 03:26 PM
He ended up getting it down to 64kg below the stock weight

Impressive! That's almost as much as a trials bike weighs!

Did he ever tell you how the bike handled after achieving that?

Guy Jinbaiquerre
27-05-15, 03:33 PM
Did he ever tell you how the bike handled after achieving that?
Much better, as you might expect. I sat on it and the sensation of lightness compared to my X4 was astonishing. But part of the improvement in handling was probably also due to his modifying the frame to decrease the rake angle. Yes, he actually had somebody cut and weld the frame itself.

JapanRob
27-05-15, 08:22 PM
My solution: Eat less! The weight of the rider makes a huge difference.

Jav
01-06-15, 01:13 AM
My solution: Eat less! The weight of the rider makes a huge difference.

Read earlier in the thread, we already established that not to be the case :001_rolleyes:

rider2371
01-06-15, 02:06 AM
My solution: Eat less!

Or to quote a long distance rider I work with, "take a big dump".

ToraTora
14-06-16, 08:16 AM
Vamping the thread I know!!!

You can spend lots of money getting a heavy bike to be not quite so heavy, or you can just start off with a light bike--like a Replica Racer. But I really suggest that you don't do this--you'll find your RSV posted for sale, and you'll start riding modified fifties (don't ask me how I know this). And then when you can find the carbon fiber for your Racing Replica you'll get that as well. ;)

Carbon fiber is much lighter than stock body parts. Fiberglass is also lighter than stock body parts. Think of it like this:

carbon fiber < fiberglass < stock plastics

A light bike is very intoxicating. Two hundred pounds seems to be like a magic number. Bike I have that are around that are just way more fun to ride. I also have a Cagiva Mito with a bunch of the SP (sports performance) parts on it. I would guess it's probably around 250lbs. It's a really fun bike--but the slightly smaller Racer Replicas are just way more fun to ride, and it's probably because they are just a bit lighter to make it past that 200lbs threshold. There is also the sense of speed. On a lighter bike you feel the speed more intensely than you do on the heavier bikes. Which is to say you wont feel as comfortable going the higer speeds on the lighter bike.


http://i1064.photobucket.com/albums/u365/derbigpr/events/GPR%20Camp/IMG_4646_zpshoztky69.jpg

With regards to being fat, and GP riders and such. If you are overweight getting down to a healthy level will improve your riding quite a bit. Not so much because of less mass for the bike to haul around, but because you'll be in better condition. The GP riders are in top physical condition. Super lean dudes. When you are overweight it will drag on you. You'll have less energy, be tired more frequently, and your reaction times will frequently be slower than they would if you were in lean mode.

With regards to wheels, and unsprung weight. Lighter wheels will improve acceleration--both going forwards, and directional changes. There are some caveats however. When you go to a lighter wheel you will loose some of the gyroscopic effect that keeps the bike upright. Also, if it is a street bike carbon fiber and magnesium wheels have some huge disadvantages with regards to reliability. Track bikes don't have to deal with pot holes, and crapy roads. These hazards will wreak havoc on those wheels. But a lighter aluminum wheel is a nice compromise for the street.

Unsprung weight are things that aren't suspended. Things like your front fender on a sport bike. Going to fiber there is an advantage. Going to an aluminum swing arm can be an advantage too, as would a fiber hugger. There are also a bunch of steal parts on a bike that could be swapped out for aluminum. Like the subframe for instance (although that would be an example of something sprung).

But as has been noted is previous posts you do tend to give up things like convenience when dropping weight from your bike. Ultimately it should be judged on the kind of riding you want to do.