*is excited* (road weight weenie content)

I couldn’t resist the Planet x carbon 20mm rims at £70 a pop…they’ve arrived, stiffer than open pro’s in the squeeze test, and 265gm.

These should make the road bike spritely and comfy, can’t wait!

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IMAG0907[/url] by alan cole[/url], on Flickr

What hubs you using Al?

Excuse my ignorance but what sort of brake pad is needed to run with carbon rims?

Do carbon rims wear in a comparable manner to alloy rims?

tbc – not sure yet, probably cheap/light Tai front (70gm or so) and 105 rear.

You still on for Weds BTW? Dinnae pull out last minute please.

LMTTM – dunno! you get special pads. SUmmer only use I suspect.

😆 Sort of thing I would do 😆

Shame about the horrid graphics. I’m sure PX/OO would sell more stuff if their labelling was a little more subtle.

Def ON for Wed – no pulling out from me.

p.s. got some carbon inserts in if you need em.

Excuse my ignorance but what sort of brake pad is needed to run with carbon rims?

I’ve used special pads which came with the wheels and decent quality normal brake pads booth have worked well, what you supposedly shouldn’t do is use brake pads which are normally used on alloy rims on carbon rims as swarth and metal from the rims embedded on the pads may damage the carbon rims. I always swap pads with rims for piece of mind.

My 1250g 50mm’s one are hung on the wall above me as I type 😀
Wha tubs are you going to run Al?

Very nice! If I swap to a chainset power meter I’d be extremely tempted by some of these, at £70 you just can’t go wrong!

Excuse my ignorance but what sort of brake pad is needed to run with carbon rims?

Do carbon rims wear in a comparable manner to alloy rims?

Traditionally a cork based pad, although there are now different artificial compounds floating about. I got on with the Bontrager cork ones (on Bonty rims) or SwissStop Yellow Kings. The braking surfaces are more variable than on alu rims, I’d not use cheap brake pads for carbon rims – it can be a bit scary.

Rims can wear if you use them all year round, but they tend to last pretty well, on par with alu at least. The bigger issue (and the two are linked) is that the brakes really really do not work satisfactorily in the wet, I’d not choose carbon for a winter wheelset, and suggest that those who do don’t actually ride in the wet, and thus don’t wear them out!

tbc…carbon inserts…for what? Cool re Weds. I ‘ll book noms for say 6:30?

Oh, and “stans alphas for sale!” 😀

6.30 is good.

Inserts for cartridge pads.

How easy is it using tubs for racing?]

basically is it worth the faff? Will I see improvements in TT times? faster accelerations in road races

Using them is just as easy as clinchers…

Fitting, repairing and replacing them is more faff, not difficult, just time consuming. If you go to your bike and you have a flat tub you’ll most likely want to use a different wheel, not change it before you nip out!

Saying that you can carry spares and change them roadside to get you home, and worry about a proper glue job etc at a later date.

IMO there’s little point unless you’re looking at carbon wheelsets, as there is a pretty substantial weight penalty associated with using clinchers on top end wheelsets.

Edit: damn your edit clarifying what you meant!

The tyres themselves won’t make a massive difference, but if you’re on 1600g 23mm deep clinchers and you change to 1200g 50mm deep tubs you will see a difference. As part of that you gain tubs, but that’s not really where the big advantage comes IMO. Were you to change to 1600g 23mm tub wheels I’m not sure you’d see much (if any) real improvement.

If someone could make 1000g clincher wheelsets for £400 I’d choose those, as clinchers are undeniably less faff, but they can’t, so it’s tubs!

Well I’ve upgraded nothing on the bike all year and been racing on the planet x model b (1653g)

For next year i have been thinking about wheel upgrades. Originally looking at the stans alpha 340 rims on some nice hubs but like the idea of tubs if they are going to save me a load of weight as i’ll only be racing on them.

If you go for the right rims (ie carbon ones) then they will. For UK racing I’d get deeps, even the P-X 50mm rims are lighter than Alphas, but with a big aero benefit. It’s certainly not gonna slow you down…

I’m only trying tubs again due to how well stans fluid works, and the weight/price.

ME was that they are alot more comfy, that’s pretty subjective though.

IDGAS about aerodynamics, my riding is fun & chain gang, I want the bike to feel light

i looked at carbon rimmed tubs at one point. took the weight penalty for cosmic carbone with an ally braking surface in the end. not much fun in the rain the reports suggested.

Nah but least while it’s dry you’re not dragging around some bloody heavy rims 😉

so 50mm worth it over the 20mm even if they are heavier?

20mm – 250g
50mm – 379g

Nah but least while it’s dry you’re not dragging around some bloody heavy rims

when you’ve got my power output (gut) a few grams on the wheels makes f*ck all difference.

so 50mm worth it over the 20mm even if they are heavier?

Definitely. The 50s are still light and at anything above about 15mph will be faster. They’re also stiffer and allow a lower spoke count which will save a bit of weight and make them even more aero in comparison to the 20s.

Edit – I’ve got a pair of PX 50s built up into a cheapo Novatec front and a not-exactly-light Powertap SL and they’re still under 1450g.

If you’ve got a big gut your power’s probably fine, it’s your power:weight that you struggle with 🙂

so 50mm worth it over the 20mm even if they are heavier?

General concensus is yes, aero is of more benefit, unless you’re climbing Alps.

also, aero look better and that’s the most important thing of all.

Any stats on 50mm vs 20mm @ say 20-25mph?

I think someone quoted some Zipp test on the last thread but it was seen to be biased…

The other thing is that 20mm rims being lighter will feel quicker on the hills (accurately), probably more so than the deeps will actually feel quicker on the flat (that was my perception anyway), so if what feels faster is what matters than absolute light weight may be better!

njee20 – Member
so if what feels faster is what matters than absolute light weight may be better!

IMO it has to be, as long as stiffness isn’t sacrificed too much….fast feeling bikes are rarely the fastest IMO.

Any stats on 50mm vs 20mm @ say 20-25mph?

I think someone quoted some Zipp test on the last thread but it was seen to be biased…

Great wheel test 2008 – Part 1 – Aerodynamics

Thanks theprawn, what I take from that test is:

W @ 50kph (32mph) – highest 32, lowest 16 – this is for 1 wheel with no bike in the picture…so we are talking an absolute max of 32W @ 32mph – a speed few on here will sustain for more than a minute.

@ 20mph (which the reasonably fit can sustain solo), assuming other resistance factors to be insignificant (inaccurate I know, but way more accurate than taking 2 x the power for one wheel in the wind tunnel), given wind resistance ~ speed squared, the 32W goes down to 13W.

What would we be putting out (fnaar) a 20mph? 300W?* so it’s in the absolute WCS of 4.3%…which is pretty significant. I’ll google *…

OK looks like my 300W wasn’t far off.

http://en.wikipedia.org/wiki/Bicycle_performance

but:

the power required to overcome drag increases with the cube of the speed.

meaning my estimate above is (a) completely wrong and (b) flawed.

32W should have gone to 3W mening 1% WCS.

I thimnk 😕

300W for 20mph? Only if you’re built like the proverbial!
On the road bike, flat road, little wind, 300W gets me 24-25mph and on the TT bike closer to 28. And I’m not very aero.

that moves it by a few % (of 1%) I think).

wiki:

Amateur bicycle racers can typically produce 3 watts/kg for more than an hour (e.g., around 210 watts for a 70 kg rider), with top amateurs producing 5 W/kg

how accurate is your meter?

300W for 20mph? Only if you’re built like the proverbial!

That’s about what I do, I’m 68kg! Maybe a couple of mph quicker.

I fancied them, but I think I’m over the weight limit?

Someone up there wanted cheap and light clinchers, Giant top end ones are sub 1400g. That’s what I’ve gone for. 1362g I think and scandium.

how accurate is your meter?

A lot more accurate than Wikipedia 😆

njee – is that a winter bike/mudguards with winter kit on etc or nice summer bike in warm weather?
300W should get anyone less than a giant to well over 20mph.

Oh, and “stans alphas for sale!”

Give to me plz Al thx.

LS & OMITN…inconclusive!

Fred – dream on! Make me an offer!

this is about bikes isn’t it?