# Help needed with headset spacing on Carbon stem.



## chas0039 (Jun 26, 2007)

Hi guys,

I have this frame and fork and I need help determining the maximum number of spacers I can use between the headset and the stem.

Maybe BikesDirect or anyone else who knows can chip in with advice?

Thanks


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## PJ352 (Dec 5, 2007)

chas0039 said:


> Hi guys,
> 
> I have this frame and fork and I need help determining the maximum number of spacers I can use between the headset and the stem.
> 
> ...


IME and without exception the max number of spacers allowed is 40mm's, so that's where I'd stop. Also allow for (at least) a 5mm spacer between the top of stem and top cap.


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## chas0039 (Jun 26, 2007)

Thanks for the info. I have seen different numbers (lower) for carbon and your number for steel and aluminum. I even saw a different opinion stating that carbon could use a larger number.

I'm hoping to get away with 30mm so I am probably safe.


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## PJ352 (Dec 5, 2007)

chas0039 said:


> Thanks for the info. I have seen different numbers (lower) for carbon and your number for steel and aluminum. *I even saw a different opinion stating that carbon could use a larger number.*
> I'm hoping to get away with 30mm so I am probably safe.


I'd take _opinions_ with a grain of salt, but I've never seen less than 40mm's (max) as a recommendation for full CF forks. Granted, manufacturers sometimes include the 'cone spacer' in those recommendations. But yes, I realized that yours was full CF, so that's why I posted that number. 

JMO, but generally speaking, full CF forks are actually stronger than the models with alu steerers and I agree that going with 30mm's of spacers is safe. Still, consider adding the 5mm spacer between top of stem and top cap, because almost all manufacturers require that.


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## chas0039 (Jun 26, 2007)

The main source I saw with Carbon for less than 40mm was the current Park Tool bike book where they specify 25mm as a general rule for just the spacers under the stem. My LBS also agrees with you at 40mm for the entire stack so I can see where Park got 25mm if you have a spacer above as well as a top cap. I always put a 10mm spacer on the top (just a 5mm cuts things too close) so if I go for 30mm under and 10mm over, I will be just a little high. I think the confusion come from the fact that relative newbies like me (just wrenching a little over 5 years) tend to not think the spacer _over _the stack makes any difference so a lot of posts use the correct method of measuring the height of below and above stacks and a lot of the rest of us are just talking about below.

Interesting to find that CF are stronger than aluminum.

I learned something new, thanks.


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## PJ352 (Dec 5, 2007)

chas0039 said:


> The main source I saw with Carbon for less than 40mm was the current Park Tool bike book where they specify 25mm as a general rule for just the spacers under the stem. My LBS also agrees with you at 40mm for the entire stack so I can see where Park got 25mm if you have a spacer above as well as a top cap. I always put a 10mm spacer on the top (just a 5mm cuts things too close) so if I go for 30mm under and 10mm over, I will be just a little high. I think the confusion come from the fact that relative newbies like me (just wrenching a little over 5 years) tend to not think the spacer _over _the stack makes any difference so a lot of posts use the correct method of measuring the height of below and above stacks and a lot of the rest of us are just talking about below.
> 
> Interesting to find that CF are stronger than aluminum.
> 
> I learned something new, thanks.


I agree that there is some confusion in the way the numbers are thrown around, and variations in terminology used only add to the confusion. I call the part before spacers a cone spacer, but others consider it just another spacer. No matter what it's called, it's height has to be calculated into the max spacers allowed. FWIW I only consider the cone washer and any spacers under the stem when calculating the max number. The spacer above the stem is there to insure full contact of the stem with the steerer. While riding, forces exerted on the steerer will be between the stem and top of headset. 

All that aside, IMO you're more than safe with your plan to use 30mm's of spacers below and 10mm above the stem. I wouldn't go more than 10mm's in height with a cone spacer, though. 

To clarify my remarks on CF versus alu/ CF forks. It's JMO, but from everything I've read and am aware of regarding failures, the majority of time they occur at the alu/ CF bond (usually at the crown/ steerer). Full CF negates the need for bonding, thus (IMO) a stronger unit.

Just a suggestion, but it would be interesting to see pics during and after your build. Got all the components together yet?


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## chas0039 (Jun 26, 2007)

Not yet. The frame and fork are here, of course, and I have about half the Campy parts in my excess "garage" stock. I still need the shifters and some small things from Ribble and the stem and some odds and ends from AEBike. I just built up a Waterford last year with a Veloce grupo and Brooks for the leather and this one will be virtually the same components. I need a rather steep stem and I only use FSA Wing handlebars so there are a few things that are sometimes hard to get cheaply. I'm also picky about Vittorio since my favorite Vredestein tires were discontinued. 

The main things I had to do before ordering parts was to get the right kind of seatpost that would allow the proper setback for the seat so that it set my knee in the right position. With the Brooks saddles, there is no where near the same range of adjustment so I have to be careful that the post has enough setback as well as enough bracket surface to allow for some machining to account for the harsh taper of the Brooks rail. Then I have to get the length of the stem just right so my reach will be accurate; and you just cannot do that until you have the frame and seat set up. Then I can finally get the fork tube cut and start the real assembly. Until the frame actually is in front of me it is kind of a crap shoot as to whether it will actually all work out. So far, this build looks like a winner.

It never occurred to me that anyone would want to see the build in progress. Would there be any value to posting the pictures and steps here?


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## PJ352 (Dec 5, 2007)

Sounds like an interesting and challenging build. I do some of my own builds and size/ fit myself (after 25+ years you learn what you need) but never encountered the type of issue you describe with the Brooks. Each build is different, though and we learn from them. 

This is my latest. Nothing fancy, but that's as it was intended.
http://forums.roadbikereview.com/showthread.php?t=207745

I can't speak for others, but I think your build is unique enough that it would be of interest to see the phases documented in a thread. You could do it here, but IMO a new thread would be better cuz now we're 'off topic'.


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## chas0039 (Jun 26, 2007)

Well. just when I figure I have it down, BikesDirest tells me I can use 35mm of spacers under the stem _in addition_ to the cone spacer on the headset. I think I'll split the difference between Park's recommendation and that of BikesDirect and go with 30mm.


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## PJ352 (Dec 5, 2007)

chas0039 said:


> Well. just when I figure I have it down, BikesDirest tells me I can use 35mm of spacers under the stem _in addition_ to the top cap on the headset. I think I'll split the difference between Park's recommendation and that of BikesDirect and go with 30mm.


I'm not sure I follow you unless you mean 35mm's of spacers _in addition to _the cone spacer. IMO the top cap is a non-issue when calculating max spacers.

That aside, I think as long as you stay at or under 40mm's below the stem and counting the cone spacer, you'll be fine.


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