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Allowed heigth of Headset Spacers?(12 posts)

Allowed heigth of Headset Spacers?CraigVM
Mar 5, 2002 1:16 PM
Having just installed my new headset & fork, I now need headspacers to bring the stem / bar, up to my prefered height. The problem is that space is over 50mm "right at 2 inches" When I called my LBS to see if they had a handful of spacers in stock, they told me that was much too far of a gap and would put to much stress on the steerer. They said that 3/4" is considered maximum for using spacers and anything beyond that, I should get a stem with less downward angle or one that actually rises to keep my bar height up. Perhaps I fear cutting any more of the steerer than I have to, knowing I could never cut it Longer in the future. Is 3/4' maximum truely the rule of thumb or what would be the longest gap suggested. It is a carbon steerer and I am over 200 lbs, so I don't want to push my luck.
1 5/8"Spoke Wrench
Mar 5, 2002 2:10 PM
I just measured several new stock bikes in our shop. The highest spacer stack I found was 1 5/8". There were lots of stock bikes with between 1" and 1 1/2". A Fuji Team with a carbon steerer had 1".

It sounds like you got a new fork. Did it have any specifications regarding spacer height? It seems to me like most of the carbon steerer forks do. If you have a steel steer tube, 3/4" seems pretty timid to me.
re: Allowed heigth of Headset Spacers?johnc
Mar 5, 2002 2:13 PM
Most carbon steer tubes allow 2cm (20mm)of spacers-max . Even that seems like a lot. With your weight, I would definetly cut the steer tube down and get a stem with the appropriate rise.
website which shows diagram of headset, spacers, stem,steererKroyl
Mar 5, 2002 3:54 PM
Is there any website which shows diagrams or clear explanations how these things all work together for threadless headsets??
re: Allowed heigth of Headset Spacers?merckx56
Mar 5, 2002 3:57 PM
look and reynolds both say 30mm!
reynolds == 30mm for 1.125" steerer; 25mm for 1.0" (nm)dsc
Mar 5, 2002 4:06 PM
re: Allowed heigth of Headset Spacers?HGS
Mar 5, 2002 5:50 PM
This topic has been posted at least a dozen times, with at least a dozen different replies.

People espouse that the stack height should never be more than 2cm and some quote Reynolds at 30mm.

Unfortunately, there is absolutely no evidence that any single person has reported a carbon steerer failure for stacks greater than 2-3cm.

In order to be careful, most manufacturers claim that a height in excess of 2.5-3cm is dangerous. Yet despite this claim, I am unaware of any single steerer failure being reported due to any cause or stack height excess.

I have read about stem failures, despite approved lengths,
seat post failures, handlebar failures, wheel failures, fork failure, crank and frame failures, but no steerer failures.

The question is....
Is this whole stem height paranoia warranted and is the steerer inherently strong enough to take even 3-4 cm stack heights.????

Anyone who is aware of a steerer failure due to stack height excess, please let me know.

MGS
I have to agree...Geof
Mar 5, 2002 7:53 PM
it seems the stress applied on the steerer is just not significant enough to 'break' the CF. Unless there is a bad joint or some other structural flaw already present. Even under a hard sprint, the entire system absorbs the torque, not just the steertube. My Look HSC3 has nothing written that defines an absolute stack height. I currently run 1 cm up and 1 cm over. I figure that the stem clamp has a bit more surface area to hold onto and there is less chance of any type of crush problem in torqueing the stem down. I think stem clamp systems pose a more inherent threat to steerer failure than stack height. Assuming we are talking carbon steerers. If it's an alloy/cro-mo steerer... Don wooorrry 'bout it....

Personally I would not worry about it on the CF either...

OMT... Profile states only 1.5 cm spacer height on their carbon steerers... Go figure...
I have Reynolds Installation bookletLazywriter
Mar 5, 2002 9:43 PM
right in front of me and on they say up tp 1 inch (25mm)stack height on a 1" steerer and 1 1/2 inches (38mm) on 1 1/8 inch steerer tube. I keep seeing wrong information and figure and this is directly from the instruction manual.
The larger 1 1/8 steerer makes a big difference in strength apparently, but I think that manufacturers put limits way below what they feel would be unsafe as people will invariably push the envelope or not follow directions.
My question is, why does every one worry about carbon forks failing when the seem to worry less about cf bikes failing in general?
It's not failing, it's flexing that concerns ridersPaul
Mar 6, 2002 6:19 AM
I built up a Look 386 with a hsc3 carbon fork/steerer. The instructions said nothing about stack height of spacers. There was a previous post that used more then 1" of spacers on a Look fork with a 1" steerer. This bike was built up at a good LBS according to the post. I now wish I had tried 1.5 inches of spacers, as now I have to buy a s tem with a rise to give me the drop that I want. But I've noticed pro bikes built up with stems that have a rise, and they have well under an inch of spacers.
I think this is really a weight savings. Other mechanics have told me not to go over an inch for one inch carbon steerers.
So, I'll err on the side of caution.
BIG BIG difference in flexCT1
Mar 5, 2002 9:50 PM
Big stack = big flex

big flex = BAD HANDLING!

Is that simple enough
JohnG
A mechanic (builds pro bikes) says don't go over an inch.Paul
Mar 6, 2002 4:23 AM
I wanted an extra 1/2 inch, and bought a stem with an 80 deg rise, whcih at 100mm in length, gave me the 1/2 inch. I used a protractor to figure out the rise as the stems (how advertised) is confusing. If you need any help on this let me know your stem lenght, height need, and I'll let you know.