Front discs weight

[duke63]

Is there such a thing as lighter front discs or are they all engineered pretty much the same as there is limited weight savings to be made?

[C00kiemonster]

Not heard of them, but i suppose drilled disks partly save weight?

Get some carbon brakes? Good enough for motogp....

[Blade]

Yes weight savings to be had.

Depends on materials used, disc thickness, carriers, etc.

Can't remember the actual saving but the Galfer discs on my SP2 are lighter than the OEM Honda items.

Its unsprung mass so the best place to loose weight from although in real world terms probably negligible benefit but saying that it all adds up.

Cheapest weight saving mod is fit light tyres. Your fitting them anyway so effectively free and can safe up to 1kg on the largest diameter of the unsprung mass. Amazes me people pay £2500 for carbon wheels and then fit heavy tyres. As a rule of thumb from my research Pirelli / Metzler seem to be the lightest and Dunlop the heaviest.

[duke63]

When i took the front wheel off this week i was amazed how heavy it felt. I wish with hindsight i had weighed it before taking it in as it seemed lighter when i refitted it. Just got me wondering how much weight can be lost and where.

If a set come up at the right price at the right time i would like to fit some magnesium wheels with Supercorsas for occassional track use only. Just wondered what savings could be made on discs too. Will have to dig some information up from tinternet.

[Kwacky]

https://www.bikehps.com/braketech/axis_cmc_discs.html" onclick="window.open(this.href);return false;

[D41]

Blade is pretty much spot on, and you start changing out OEM discs you're opening a can of worms regarding fitment & compatibility with the wheels AND the calipers....through 'offsets' and other annoying things.
More bother than any perceived benefit you'll ever gain.

[Cav]

Disc thickness, drill holes and grooves. These are the main considerations.

As for material, I would only choose a High Carbon Steel or Ductile Iron disc. The Brembo 320mm disc I have now is a couple of grams lighter than OEM (300mm) disc due to thickness

[rocket]

I got hold of some Ebc light discs for the rs250 ... I weighed them when I got them and they are 100 grms heavier than stock. However the stocks have been used and the ebc look like they have just been stored on the bike

[Blade]

You can fill the tyres with lightweight air if you want a cheap reduction in unsprung mass.

[Monty]

I know that was said in jest Blade, but you could actually. Helium.

[Cav]

You could put helium in tyres but you'd be forever losing tyre pressure due to molecule size

[Monty]

True that. Thats why they use Nitrogen

[kiwikrasher]

True that. Thats why they use Nitrogen

But not for weight savings.

Air is already 78% nitrogen. By replacing the 21% O2 and other misc. gases you would save absolutely feck all weight.

We used N2 in Aircraft tyres for the following reasons,

Dry, no moisture as with air so less corrosion problems on the hubs (rims)

Less change in pressure due to heat variations

Safer, aircraft tyres on the A4's were inflated to 350psi, so if that was air there would be a significant component of high pressure O2, would would cause issues during a brake fire.

I know there advantages to the whole weight debate but for me I have 150 hp and can't use it all on the road 98% of the time. I stop at a pub and fill my gut with a pile of food and drink which would be a kg or so. I'm not really fussed about 200g here, 100g there. The easiest way for me to reduce weight is leave the pillion at home

[D41]

My own thinling is that of all the plances to lo9 weight on a bike the BRAKING discs are probably not the best place to start...??

Spot on about a nitrogen charge in the tyres.....it really does work well.

[Cav]

The thing is with nitrogen.. you'll never achieve 100% Nitrogen and the molecule size is 3pm larger than oxygen - that's 0.000,000,000,003m

[Cav]

As for weight saving unsprung mass...

Wheels
Brakes
Suspension
Bolts
Hugger

That's about all you can do. You could change tyres for the lightest but for me, the confidence a tyre gives me is worth way more than saving 0.5kg

[Monty]

True that. Thats why they use Nitrogen

But not for weight savings.

Air is already 78% nitrogen. By replacing the 21% O2 and other misc. gases you would save absolutely feck all weight.

We used N2 in Aircraft tyres for the following reasons,

Dry, no moisture as with air so less corrosion problems on the hubs (rims)

Less change in pressure due to heat variations

Safer, aircraft tyres on the A4's were inflated to 350psi, so if that was air there would be a significant component of high pressure O2, would would cause issues during a brake fire.

I know there advantages to the whole weight debate but for me I have 150 hp and can't use it all on the road 98% of the time. I stop at a pub and fill my gut with a pile of food and drink which would be a kg or so. I'm not really fussed about 200g here, 100g there. The easiest way for me to reduce weight is leave the pillion at home

Cav was talking about molecule size not weight. Nitrogen has two molecules of Nitrogen bonded together, helium has one and smaller molecules. Hence you lose less gas.

[Kwacky]

It's only a concern if you can be bothered to check your tyre pressures.

Which I don't.

[D41]

Are we really getting down to a discussion of the molecular density of various gases???

You can tell it's winter.

Speaking of which it's storming right now...that's today's MTBing plans out the window.

[kiwikrasher]

Cav was talking about molecule size not weight. Nitrogen has two molecules of Nitrogen bonded together, helium has one and smaller molecules. Hence you lose less gas.

The way I read it the convo went

Use light air
Better still use helium
It'd all fall out if you did
"That's why they use Nitrogen"

I was pointing out why they use nitrogen which isn't because the lighter smaller molecule helium escapes.