[Eddiejt]

After reading all the excitement over Aero bikes I’ve challenged myself to make a sub 7kg, sub £1000 road bike for club run specific route and maybe the odd TT/crit race.

I’ve so far spent £330 on a used Planet X N2A frame forks and seat post, and will also invest in some of China’s finest 50mm clinchers for another £300.

Now on to the groupset. Call me mad but for simplicity’s sake (and cost and weight targets) I want to ditch the Front Deraileur and go for a 1 x 10 speed on a 12-32 cassette with 50t chainring. This isn’t as bad an idea as it sounds, since on our club run route I currently ride a Cube Litening with 11-25 cassette and 53/39 chainrings; I use less than half of the range offered by this setup on this particular route and could reproduce this range with the 50 x 12-32 proposed. Plus having this range on the same chain ring would be preferential.

Now then, I am open to suggestions on groupset to achieve this. I have no bias towards manufacturers, and will have to buy used. My goal is light and all in for £250. I’m thinking:

-Dura Ace 7800 shifters and RD (but not sure I can get a 12-32 cassette for this).
-SRAM Red 10 speed BB30 crankset
-DA 7800 brakes

OR

-SRAM Red 10 speed everything (again not sure if 12-32 cassette available).

All pretty dependent on what bargains I can find on ebay.

Topic

[Eddiejt]

Yep, definitely worth
Yep, definitely worth considering.

[Eddiejt]

Yes, that’s an idea, it’s
Yes, that’s an idea, it’s just that a 50t ring is a lot easier to come by than a 48t.

[Eddiejt]

Think I’ve been convinced to
Think I’ve been convinced to go Red 10 then after the above, particularly since they do a BB30 crankset (unlike Shimano) and I’ll take my chances with a standard chain ring. I can always change it if necessary.

Glad to hear you’re a fan of single chain ring, Mike.

[BBB]

It happens to some
It happens to some people/bikes and don’t happen to others. My setup is a DH 44t Middleburn chainring run on the inside for a perfect chainline, with a 11-25t 10sp cassette and the shortest possible chain. And without a fr mech acting as a guide the chain drops.

[mike the bike]

SRAM never tire of telling us
SRAM never tire of telling us that their single chainring set-up has a wide-narrow ring to keep the chain in place. The theory is that the chain has to splay further from side to side to cover all the cassette, whereas with a front derailleur you would be careful not to run big-to-big or small-to-small.

However, I’ve been a fan of the single front chainring for two decades, mostly on my commuter bikes. Edinburgh Bicycles used to specialise in them as part of their Revolution range and I bought four over the years. And without the benefit of the patented wide-narrow chainring did I suffer from chain drop? In short, no.

I’m not saying it never happened, but I can’t remember it.

[Eddiejt]

Excuse my ignorance but why
Excuse my ignorance but why would I need a “wide narrow” chainring? Why would a regular chainring cause the chain to come off in a 1×10 setup? Is this due to the absence of the FD?

[adam900710]

Eddiejt wrote:Very

Eddiejt wrote:

Very informative and some good ideas. Thanks guys.

On seeing someone today with full 5800 that he got for just £250 new, I’m tempted!

Might just go 1×11 with that….50×12-32. The 11 speed will help with the gaps. Do you think it would be much heavier than Red 10 or 7800, 6700?

For the price of full 5800 groupset, £250 is still too high.
But that’s OK as most Shimano dealer won’t drop their price too much.

In fact, you can get full 5800 groupset, with BSA BB included, without shift/brake cable, at about £210. (Ok, most Shimano dealer in China is sellomg at that price online anyway)

For weight, IMHO, it should be much heavier than 7800 DA, even7800 DA are two generation older. And for RED, it’s lighest among all groupset, only newer RED can defeat it anyway, it’s about 100g ligher than same gen DA.

For comparision among Shimano, DA 9000 weights just less than 2kg, UT 6800 2.3kg, and 105 5800 is near 2.7kg
I’d like to assume 7800 is at most 2.1~2.2 kg, so about 500~700g weight penality.

Personally I prefer 105 5800, due to its super good brake power and modulation, and of course its 11 speed, other than 2nd gen older DA,
even with the weight penality(one 650ml bottle of water).

But if you don’t feel good with that 500~700g weight difference, 10 speed RED should be your best consideration anyway.

[Eddiejt]

Very informative and some
Very informative and some good ideas. Thanks guys.

On seeing someone today with full 5800 that he got for just £250 new, I’m tempted!

Might just go 1×11 with that….50×12-32. The 11 speed will help with the gaps. Do you think it would be much heavier than Red 10 or 7800, 6700?

[BBB]

You could go for a 11-28
You could go for a 11-28 cassette (easier to find) with a 46T chainring…
You’ll need some form of chain retention device. When I started running my 1×10 setup I was dropping the chain frequently even with a dedicated single chainring. The neatests solution would be to get a narrow wide chainring. Wolfteeth Components makes them in many sizes and BCD options.
The only drawback I can see with your setup would be gaps in between the gears. Think if you could live with a slightly higher bottom gear…

[adam900710]

Not sure 7800 is good
Not sure 7800 is good enough.
As far as I tried 5700 and 6700, the shifter needs more force to operate even than 4600.
And that’s why the new 4700 jumps from external shifter routine to the 2nd generation internal routine, just skipping the 1st generation one(5700/6700/7800).

So for your case between RED 10 or DA 10, I’ll choose RED other than DA, even I’m not a fan of double tap.

But personally, I’d like to choose full 105(5800), except the crank. Maybe Rival 1x crank or other custom crank with wide narrow chainring.
If you stick to 10 speed, 4700 should be as good as 5800.
4700/5800 should be easier to find and maybe even cheaper than some good condition used DA parts. Although heavior anyway.

And if using 5800, 11-32 cassete with gs derailleur is quite easy to find.
I have 2 bikes with 11-32 setup, commuter one using 5800 compact and good one using 6800 semi-compact.

For 10 speed, 12-32 is not easy to find.
My previous 10 speed bike is using 12-30 6700 cassette, IIRC, it’s already somewhat hard to find. It should be even harder to find nowadays.

[Eddiejt]

Ah, so it is possible to make
Ah, so it is possible to make up your own cassettes, but mixing 2 together? I knew it was physically possible, but did wonder why I had never read anything about it being done.

Thanks for the link; I’ll have a good read later.

[CXR94Di2]

You will need a ‘gs’ cage on
You will need a ‘gs’ cage on the rear derailleur. This will guarantee it will work with 32T gear. Now you need to check weight difference between all the shimano range, only a few grams to get the right derailleur.

Or you could use two 6800 cassettes to create a 14-32 cassette, it will give you smaller steps in the middle, at the expense of top speed

I have dabbled with various setups see
http://road.cc/content/forum/149963-14-32-cs6800-cassette-gearing

[Author]

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