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I think the rough rule used to be 3cm of spacer max under the stem maximum.
Will I die if I use 4 x 1cm spacers?
Depends a bit on the bike and why you're wanting a higher position.
You might die if it means your stem doesn't clamp enough of the steerer.
40mm under the stem as long as there is enough steerer for the stem to clamp. Anything more than 40mm and you've got the wrong size bike.
The amount that make it fit
Anything more than 40mm and you’ve got the wrong sized bike.
that isn’t specifically true. Headtube lengths are shorter than what they used to be.
Anything more than 40mm and you’ve got the wrong size bike.
More likely you've bought the wrong type of bike. As I'm now at an advanced age longer headtubes are where it's at for me.
Check the spec of the fork and the frame: sometimes they publish a maximum, since it increases leverage and stress on the steerer and headtube
No generic answer without knowing f&f details
Thorn say you are wrong Neil
Doesn't mean thorn are right .but it does make your sweeping statement wrong.
Most Carbon steerers do how ever have. A max allowable spacer height.
40mm under stem max under stem and at least 5mm above stem, is the general rule iirc
6 Ft 2 rider
110mm head tube
internal headset
30mm of spacers
50mm rise Spank Spike bars
I want to try my bikes bars another 1-2 cm higher (this years frame has been updated with 1cm more on the headtube)
Head tubes on different brands frames vary so much.
A Stanton Slackline 19.5 inch frame has a 140mm head tube and it takes an external bottom cup so thats another 10mm
A Santa Cruz Chameleon XL mk7 frame has a 110mm head tube with an intergrated headset
Both bikes are for roughly the same size rider but there is a 50mm difference in bar height.
Most manufacturers seem to adjust the seat tube and the length of their frames a good deal but only adjust the head tubes a tiny amount. I’m wondering if the larger frame headtubes should increase in proportion with the other dimensions.
Most bikes historically have.
But fashion for being unridably low because the pros are drives them.not to incase they get a silly reviewer who marks it down due to not being able to emulate his idol
“I’m wondering if the larger frame headtubes should increase in proportion with the other dimensions.”
It’s a puzzle. If a bike has short head and seat tubes then a rider with a long back and short legs can size up for more reach. But a rider with a short back and long legs will need to run a lot of seatpost (that’s a good thing - longer dropper!) and more steerer spacers and bar rise, because for a given riding style your bar height relates most to your hip height.
At a long-legged 5’11 I’m running 30 and 40mm rise bars with ~20mm of spacers on bikes with 150 and 160mm forks. Both bikes (one medium, one large) have pretty tiny head tubes (110 and 115mm).
So I’d say head tubes do need to get a bit longer, like very recent seat tubes, but not a whole lot. More standover with a short head tube too, often where you most appreciate it when things go wrong...
Most pro enduroists are running HIGH bars nowadays.
RockShox manual states no more than 30mm of spacers below the stem.
thorn, spa cycles and most custom touring builders leave steerers long with plenty of spacers.
fashion is shyte
comfort makes sense
How many is too many, not how many is too much.
#grammerpendant
‘Are too many’ not ‘is too many’
#grandmapedant
Nasty petard wound that!
"RockShox manual states no more than 30mm of spacers below the stem."
While it's true it says that now .
I'm old enough to remember when that statement was only found in the carbon steerer section.
Sounds suspiciously like a copy and paste error .
I think the rough rule used to be 3cm of spacer max
What rule? The stresses on the steerer tube and headset bearings will be the same whether you use spacers under the stem, a riser stem, or riser bars. Fork travel has increased massively over the last 15 years so people are running less rise on the bars and stem to keep the bars down to a sensible height. In the old days, running the bars 100 mm above the headset wasn't unusual and people weren't falling over dead everywhere.
^
What rule?
Let's see:
Bar ends on risers?
Suspension seat-post on full-suser?
Silver cranks - black bars, stem and seat post?
Answer: No rule. No rules at all.
I can see that stresses on the headtube don’t change, but I’m sure that it affects the steerer.
Think about a stem that gives 25mm rise, with no spacers. Then that same stem flipped with 50mm of spacers under it, so 25mm of drop.
Bars end up in the same place, but in the second case the steerer is clamped by the stem 50mm above the top cap and a long way above the upper headset bearing. Stress on the steerer must be different.
I guess that’s why the limit is published for the fork (not the frames, as I thought before). Just looked up the fork I just fitted, says max 40mm spacers below the stem.
But fashion for being unridably low because the pros are drives them (sic)
alternatively, most folk I see on the trails don't/won't/cant get low enough to actually ride properly.
(some sarcasm may be involved in the production of this comment )
If there's a limit on spacers under the stem then there should be a limit on stem length .......
My 130mm Thomson even when slammed must exert more force on a steerer than a 35mm gnarduro stem with 50mm of spacers under it....
I'd try it first .. nothing "sane" is going to break in a few rides. (sane might change with carbon steerers)
Mess with the spacers .. ride and decide what you need. It might be inside 40mm...
Once you do that you can work out how you move on... bars and stem can be changed if necessary .. but one thing is sure, sticking the extra 10-20mm back on the steerer is bloody hard once cut!
Stress on the steerer must be different.
Nope. The maximum stress on the steerer will be around the top headset bearing. If the bars are in the same position relative to the headset, then the stresses on the steerer and headset will be the same for normal riding. Crashing might be different, of course, because the end of the steerer might take the full force of the crash so a longer steerer will exert more stress. Still going to be much less than the bike landing badly on the front wheel.
That 50mm difference in height between a Slacklime and a Chameleon will have a lot to do with the Chameleon being a 29er
Let’s see:
Bar ends on risers?
Suspension seat-post on full-suser?
Silver cranks – black bars, stem and seat post?
Answer: No rule. No rules at all.
That's a Gravity Dropper. The rest I'll give you.
One,maybe 2* , any more ruins the aesthetics!
*unless you are very tall,then you can have more to make your gate a more comfortable ride. 🙂
Pffft, whadda bloody South Africans know?
Too much.
#grammerpedant
Ahem!...
You know when you have too many spacers because the top cap bolt won't be long enough to screw into the star nut 😁