Hi, all!
I knew that replacement Lefty steerers exist, but until yesterday I did not realize they could be used on a Cannondale frame in order to run a standard stem (that is, replace the Cannondale steerer and OPI stem).

Here is an example: http://mcfk.de/Produkte/GabelschaftLefty.php

I'm considering this route.

My Cannondale steerer weighs 79g; a 100mm/-15 OPI stem weighs 171g.

These carbon steerers weigh 79-80g, so no weight savings there. However, I am then free to choose my own stem. I'd consider the Syntace F109 (103g?) as I am using 31.8 bars.

1: Does anyone have experience with these steerers? This is for a light build that will actually be ridden and raced on real MTB trails. Are there any issues?

2: The OPI stem does not require a compression plug or top cap. Do these replacement steerers require that? If so, it reduces the weight savings. Most pictures of the steerer do not appear to include this -- but I imagine one needs the top cap to keep the stack together (and therefore a compression plug).

3: Can anyone recommend one brand over another?

Thank you!

I have about 8 months of trail riding on an MCFK steerer, so far with no real problems at all. I have a light weight top cover and bung in the steerer which adds about 20g, but at least gives some option for adjusting the headset when out on the bike. The tightening torque for the fork clamps on the steerer is lower than on the Cannondale steerer, so I think that makes it coming out of adjustment somewhat more likely. For a race though you could clearly remove it.

_________________
Enjoying my Funk

thank you. hm. unless i go with a really light stem, the need for a cap/expander reduces the benefit.

cannondale system = 79 + 171 = 250g
mcfk + F109 + cap/expander = 79 + 113 + 20 = 212g

any really light stems that work with 31.8 bars and are good for real-world use? the F109 seems quite sturdy and sensibly priced. extralite has the UltraStem OC @ 85g (http://www.extralite.com/Products/UltraStem%20OC.htm), which is more appealing from a weight perspective.....but too light for real MTB use?

i plan to use either Enve sweep (700mm) or MCFK flat (also 700mm) bars -- both 31.8 diameter. I ordered the MCFK and now admit that I wonder if they would be a problem in a crash. (I read some language from Extralite that 25.4 bars are stronger, and their carbon+alu bars are the best for normal use + an occasional crash (http://www.extralite.com/Products/handlebars%20standard.htm); however, they do not make their 25.4 bars in a width I prefer.)

any comments on the stem? should i worry at all about the MCFK flat 31.8 bar? i KNOW the Enve sweep bar is OK.

thank you!

That's exactly what I put on my new build! MCFK steerer and handlebar with a Extralite stem 90mm 31.8! I haven't been able to ride the bike but, i think i will be able to today!

I have an MCFK flat bar (bar end compatible) and have crashed a few times on it with no ill effects so far. I think its a great bar.

I think the bung isn't a requirement at all. Its worth the weight to me to know that I can always adjust it if I need to mid ride... but there are plenty of people who use the steerers without (pretty sure Eliflap is one of them). I haven't had to make any adjustments for a long time, so it may just have been a case of things settling at first.

_________________
Enjoying my Funk

is yours a 25.4 or 31.8 bar?

also, if one doesn't use a plug (bung), is there some sort of covering/top cap for the MCFK steerer that can be used? i imagine one needs an expander to thread the top cap's bolt.

does one use one of these to cover the opening?

http://stridaworld.com/en/componenttool/543-cannondale-lefty-steerer-tube-plug-hd210.html

i wonder about issues with these lefty steerers without an expander. well, i suppose they would include one (or state the use is required in the instructions) if they were essential.

just seems to be a concern.

my road bike's stem is heavier and although it sees higher speeds it experiences less bumpy terrain.

I may be biased here as I make and sell those EP steerers.

Facts:
1. Of nearly 300 pcs, real failure (broken off upper part) 2 of them, one during a crash. A another one a "JRA", if I recall right.

2. Several warranty claims are due to "crashes", very few of them is manufacturing defect.

3. I have replaced all but two of these warranty claims. Even some was over 1 year old.

4. Weights down to 62 grams complete tube can be delivered, any color, any setup type.

5. Tubes are nearly 100% UD from Ultra Carbon fiber made for me, with my specs, The overall thickness is only 1.6mm thick carbon, what is others?

6. I build combos too, with your specifications.

Personal thoughts:

I believe in aluminum or machined metal bearing surface in contrary what others does as carbon cannot hold a tolerance of h7-h8 out of a mold, they AREN´T perfect, rarely.
I could do a much lighter tube with carbon bearing surfaces but where is the precision? Just gone out of window.

Cannondale headset bearing have a tolerance window of 39.61 = sloppy fit, 39.66 = perfect snug fit, 39.69 = don´t go in.
So you see, +- 0.035 around there, that´s very close tolerance and it have to be parallell too, I do both bearing surface on same session every time, parallellism is a key to good bearing life.
That´s why I machine them after anodizing, the variance in anodizing build up is unacceptable for me, perfect bearing surface is what I accept.

Out of mould carbon cannot achieve that, not even lathed carbon either, I´ve tried that with very low success rate but I´m only a metal machinist guy.

Using expanders with my tubes is not recommended, often not needed, we are in the age of sealed ball bearings now.
Use a vise clamp when setting play then remove it before you ride.

_________________
Experimental Prototype

Interesting to read that about expanders as you can't adjust a Cannondale Si headset like a normal.

I've used OPIstem before but now I use a 70g steerer from Experimental Prototype and a Tune Geiles Teil 4.0 stem. The steerer works just like it should and the weight is fantastic. Good weight saving and nice to be able to use which stem you want. Using it with a AX-Lightness Poseidon handlebar if it matter.

_________________
/jonas l
http://cerrol.wordpress.com (my cyclingblog)

Thank you so much for taking the time to reply.

I noticed in another thread you wrote "If you want a more bulletproof product, take a MCFK, they have good reputation and better availability." (http://weightweenies.starbike.com/forum/viewtopic.php?f=1&t=98648#p839073)

Above you seemed to be saying your steerer (with aluminum contact points) is a much better way to go. i'm a little confused.

Thank you!

PS What stem(s) do you recommend for OS (31. bars for use with your steerer? The Extralite UltraStem OC's weight is intriguing, but I worry about it being too light for real trail use. The Syntace F109 looks great, but it is heavier and reduces the weight savings of replacing the Cannondale steerer + OPI stem.

You are correct, I´m not that reliable in my comments
In fact, my tubes comes with limited usage spectrum. MCFK doesnt. They allow for 100 kg rider weight and any riding type if I recall right.
The down side is as far I know, no machined bearing surfaces, if you can live with it. Go for it.

Regarding stems, Extralite stems are light but flexy, the very same applies to AX Lightness stems, go for them if you are in hunt for ultimate lightweight combo.

Or invest in a combo with tube + stem and handlebar, much lighter.

_________________
Experimental Prototype

I also have 2 EP's !
Good quality and weight, pricing is also fine.

just wanted to follow up. i actually ordered an MCFK steerer with the idea that it would be a lighter option than the stock cannondale parts.

i actually found that the MCFK carbon steerer weighed more than 100 grams -- compared to 79 grams for the cannondale steerer.

while the cannondale OPI stem is heavy (171 grams in a 110mm length), when i factored in the heavier steerer (109g), the weight of the expander/bung + top cap (not essential but helpful) (~20g) and the weight of a sturdy stem (e.g., the syntace f109 -- approx 120g), the weight difference was nearly nothing (250g for cannondale vs 249g for MCFK/Syntace). i decided i would rather have the security of the cannondale system. i understand others may want flexibility to run different (light) stems, but i wanted to run a sturdy stem that is still designed for hard trail use.

also, the MCFK steerer is quoted as 80g but actually weighed 100g. perhaps my sample is heavy. even so, the added complexity made it not worth it for me.

100 grams? really? They are bombproof I was told.

I recommend one piece combos for lightweight and good stiffness.

_________________
Experimental Prototype

The MCFK steer tube is actually quite stiff. I am 86 kilos and have ridden one in competition XC for about 2 years. Nothing but good experience from here! The CS from MCFK is further really great and I have received discounts on their products after I crushed the end of a MCFK handle bar in a crash (I ended up in a big rock, so guess it was fair enough that the end of the handle bar got somewhat messed up).