Number of spacers recommended

[kimmie]

Hi all,

A n00b question... I understand that 40mm is the 'limit' for spacers under the stem, but is there any 'limitation' (or maximum height) for the spacers on top of the stem? My current bike has 40mm under and 20mm on top. Is that ok?

Secondly, how 'dangerous' it is to have 50mm spacers under my stem? My bike fit is best for 50mm, but I read that the recommended max stack is 40mm to avoid 'failure'.

I understand there are a lot of discussion about this on the net, but I would love to hear 'first hand' from you guys here in my trusted forum, rather from somewhere else, so please don't ask me to google.

[twizzle]

I raced an alloy Giant TCR for for ~2 years with 60mm of spacers under the stem on an alloy steerer. My wet commuter runs 4cm of spacers.

But I also have two Ribble frames, one 62cm, one 64cm, with TT of 58cm and 59cm, so not many spacers anymore.


Sent from my iThingy...

[scirocco]

If it is any consolation, when manufacturers give maximum loadings etc they are very conservative. They have to be to avoid getting sued. So the "limit" of 4cm will be based on something like having a safety margin for a 130 kg gorilla trying to rip the bars off in a 1800W sprint. If that guy isn't you then you probably have an even larger safety factor. Even at 5cm.

If you have a modern carbon steerer tube with the 2mm thick tube then it will probably survive a nuclear explosion. When I cut my carbon steerer down I tried running over the offcut with my car. It squished it a bit out of shape but it did not crack, tear or delaminate.

[kimmie]

@twizzle: Thanks for sharing your experience. Mine is a Carbon steerer - will that makes it more fragile?
@scirocco: LOL. I love your analogy. I am 178cm/77kg rider and I definitely don't have 1800W power... Well, my bike-fit was actually 6cm according to my LBS, but I try to compromise it a little bit by lowering the stem with 5cm spacers... Thanks for sharing your experiment with the carbon tube too. Really helpful.

So the stack on top of stem is irrelevant? It will not affect the strength at all? I mean with the bolt pressure, etc...

[twizzle]

@twizzle: Thanks for sharing your experience. Mine is a Carbon steerer - will that makes it more fragile?

No -alloy WILL fail from fatigue at some point in time. Carbon, when free of manufacturing defects, won't fatigue... well, that's what people in the industry *think*.

[RonK]

I raced an alloy Giant TCR for for ~2 years with 60mm of spacers under the stem on an alloy steerer...

Hincapie's only lasted a couple of hours...

[twizzle]

Hincapie's only lasted a couple of hours...

Because Lance weakened the tube with a hacksaw after George called him fat.

[jacks1071]

Hi all,

A n00b question... I understand that 40mm is the 'limit' for spacers under the stem, but is there any 'limitation' (or maximum height) for the spacers on top of the stem? My current bike has 40mm under and 20mm on top. Is that ok?

Secondly, how 'dangerous' it is to have 50mm spacers under my stem? My bike fit is best for 50mm, but I read that the recommended max stack is 40mm to avoid 'failure'.

I understand there are a lot of discussion about this on the net, but I would love to hear 'first hand' from you guys here in my trusted forum, rather from somewhere else, so please don't ask me to google.

I'm going to assume we are talking about a carbon steerer here?

There is no limit to the spacers on top of the stem however it is beneficial to have the stem clamp the area that is supported by the spreader bolt / wedge. This is because that will help prevent crush damage.

When you put too many spacers on top of the stem, you need an extra long spreader bolt / wedge if you want to support the stem clamping area.

I had some of these made up extra long for just such a purpose, the long version is 52mm which should cover you nicely for 20mm of spacers on top of the stem.

http://www.pro-liteoz.com/store/index.p ... oductId=41" onclick="window.open(this.href);return false;



I would not run more than 40mm of spacers beneath the stem on a carbon steerer.

If you need more than 40mm either flip the stem up, or get a stem with more angle, or change the fork to one with an alloy steerer.

Safety first when it comes to steerers, if you break a steerer you will crash and its almost always head first into the bitumen.

[RonK]

Hincapie's only lasted a couple of hours...

Because Lance weakened the tube with a hacksaw after George called him fat.

He called him a drug cheat too - I wonder what Lance will do to get even for that...

[twizzle]

Hincapie's only lasted a couple of hours...

Because Lance weakened the tube with a hacksaw after George called him fat.

He called him a drug cheat too - I wonder what Lance will do to get even for that...

Everyone called him a drug cheat. But no-one gets away with calling him fat.

[warthog1]

I'm going to assume we are talking about a carbon steerer here?

There is no limit to the spacers on top of the stem however it is beneficial to have the stem clamp the area that is supported by the spreader bolt / wedge. This is because that will help prevent crush damage.

When you put too many spacers on top of the stem, you need an extra long spreader bolt / wedge if you want to support the stem clamping area.

I had some of these made up extra long for just such a purpose, the long version is 52mm which should cover you nicely for 20mm of spacers on top of the stem.

http://www.pro-liteoz.com/store/index.p ... oductId=41" onclick="window.open(this.href);return false;



I would not run more than 40mm of spacers beneath the stem on a carbon steerer.

If you need more than 40mm either flip the stem up, or get a stem with more angle, or change the fork to one with an alloy steerer.

Safety first when it comes to steerers, if you break a steerer you will crash and its almost always head first into the bitumen.

+1 to this post really good advice. Make sure the compression nut/spreader is located inside the steerer where the handlebar stem applies its clamping force.

[TDC]

I would not run more than 40mm of spacers beneath the stem on a carbon steerer.

If you need more than 40mm either flip the stem up, or get a stem with more angle, or change the fork to one with an alloy steerer.

Not to forget, if you flip up the stem, you have to put on racks and panniers.

[Dave R32]

Not to forget, if you flip up the stem, you have to put on racks and panniers.

And a beard.......your second bike will be a recumbent.

Cheers
Dave.

[jacks1071]

A beard?

http://en.wikipedia.org/wiki/Beard_(female_companion" onclick="window.open(this.href);return false;)

[toolonglegs]

Shouldn't really tell you how I run my tt bike lol... Slammed adjustable stem, use expandable adjuster and spacers to set the bearing tension... But I need them for another bike, so once the stem is done up I take them all off...

[jacks1071]

Shouldn't really tell you how I run my tt bike lol... Slammed adjustable stem, use expandable adjuster and spacers to set the bearing tension... But I need them for another bike, so once the stem is done up I take them all off...

I've seen guys do that, it goes bad when they ride out to racing and realise the headset is loose

To be fair, you probably don't stress the steerer on the TT bike so much as you arn't swinging off it like you would a road bike and I'd imagine the KMS on it would be pretty limited compared to the roadie?