1” threadless stack height and negative rise querrt
 

Hello,

I’m not certain this is the proper board for this query so apologies if I’ve run aground.

I’m using some older parts on a new frame with a 1” threadless head tube. My only matching stem is a 3t mutant which has (I believe) a -10 degree rise.

I had my mechanic press the headset and leave the steerer long to accommodate an upright riding position required by my less than nubile body.

The steer is currently about 110mm above the headset. I was planning to keep the height and set the stem at the top.

My mechanic objected and mentioned with a negative rise and a 2-bolt faceplate could be unsafe if sitting on more than 40mm of spacers.

He thought such a stem wasn’t to be flipped and this would be unsafe.

He suggested a 120mm stem with a 17 degree rise would be perfectly safe at any height.

So, what gives? This doesn’t make any sense to me and I’ve never heard anything along these lines before. I can’t see a reason that shear force would vary significantly on a positive or negative stem or how flipping this stem would make it less strong.

Anyone have any insight or experience to share?

Finally, if anyone has experience using either North Roads style bars or perhaps Bosco’s I would be grateful to read your opinions!

thanks

It's your bike you decide.
But if an experienced machanic told me something I would listen. Will you be comfortable riding the bike down a hill after going against his advice.
Use a good stem that works. They are cheap.

Most stems are designed somewhat symmetrical and can be flipped with no problems. Looking at 3t mutant photos it appears to have more material along it's length at the top which would allow for higher tension loads from the down load on the handlebar. It appears that this stem is designed to be mounted one way. That being said as you are riding in a more upright position and if you are not an aggressive racer the stem is likely pretty strong and it is unlikely there would be a failure. However, as blamester says, stems are cheep so why not use one designed to be installed either way. Also the 3t mutant sell used for about $90 on line so you can likely but a new generic stem for less. The 3t Mutant will also look funny upside down in my opinion.

Difference between the stems and why the mechanic says the horizontal one at the max height (did you say you were using 40mm of spacers?) or the one with more upward rise that can be mounted closer to the top headset bearing using fewer spacers - has to do with stressing the steer tube too much.

I’ve always read that stems on threadless steer tubes ideally should have 30mm or less of spacers for optimal safety. If your steer tube is aluminum (or steel) then you can go a bit higher. If the steer tube is carbon fiber this becomes more important.

Please post a photo!

Most threadless stems are able to be used as either +/- rise / drop. The Mutant isn't one of those, however. If you're not planning on using the bike for anything more than light-duty casual riding, you'll probably be OK, but it will look funny. It'll probably look just as funny as putting a -17* stem on top of a 4" stack of spacers, just to make a mid-rise stem.

1" threadless is a bit of an odd duck, since it wasn't around very long, and hasn't been used in a long time. You can also use a 1-1/8" stem, with a reducing sleeve. It's pretty common, and would open up a lot more stem and bar options since 1-1/8" is pretty much universal now.

The 3T Mutant came in a 1” threadless version that required no spacer for 25.4mm steer tubes.

I know that, but 1" threadless stems are not all that easy to come by these days, and if you're looking for a specific rise and reach, there's a lot more options in 31.8"

Sounds like the OP is trying to make a bike parts-on-hand, and he's trying to make a 'race' stem work on his upright path-bike.

Leverage
 

He said a longer stem was safer than a shorter stem? That sounds counter- intuitive. A stack of inserts that high is definitely unsafe as the spacers are spacers ie built for compression not their lateral strength. Use a riser ;they are designed for lateral strength.

NITTO UI-85EX comes with a 1" - 1 1/8" shim

very nice item
https://cimg3.ibsrv.net/gimg/bikefor...12a02f32de.jpg

velo orange also sells

Stem Shim 1" to 1 1/8"

for $5.
I wouldn't feel married to ridiculous vintage 1" stems

Thank you all for your input.

Yes, I’m trying to build the frame up using my parts bin. I have other stems however the mutant is 1” threadless and so is the frame. The odds of having a chance to use it are pretty slim indeed!

Anyway, my primary question is about s negative rise stem and a maximum safe stack height.

The steerer is steel.

Does anyone know about using a negative rise stem on a steel steerer at say 100mm?

For a quill this wouldn’t be an issue so I’m not sure why it is on threadless steel steerer.

I don’t plan to flip the stem I just thought his response didn’t make much sense.

thanks again!

oh, and to Masi, 30mm max stack height is only important on carbon steerer.

It is stupid having a big stack and a negative stem. Flip it. It will also look stupid but in a more charming way.

Try some big ol silly cruisey bars with it too.

All about width
 

I have an 853 TT bike with a 1" threadless headset.It was all about reducing width/size and weight. My all steel bike weighs 8.5 kgs which BITD was extremely light for a steel framed bike.

Since you have a steel steerer, you’re probably alright structurally. The cosmetic result of some of these less than ideal threadless stem set ups is sometimes OK, other times it can look tragically wrong aesthetically.

Thread City could you clarify what you mean when you say negative rise stem? I am trying to visualize it but struggling....

He mentioned specifically a 110mm 17 degree stem would be safer to use at above a 40mm stack height than my stem (110mm -10 degrees) at that height or an 1” higher where it would likely end up.

I guess I don’t have a firm enough grasp on the physics bit I would think the leverage placed on either stem would be largely that same, as would the leverage on the steerer given equal exposure length.

-10 degrees. Or a slight decline from steerer to the the bar clamp.

My understanding of what the OP’S shorter stem is that it is going to extend horizontally from an uncut threadless steerer with a big stack of spacers. And that the longer stem is angled such that fewer spacers would be required thus making a more rigid (safer) threadless Aheadset install, albeit with unknown final reach and height.

Also - Thread City you now have over 10 posts so you should be able to upload photos now.

that what it’s all about at the end of the day

https://cimg2.ibsrv.net/gimg/bikefor...d843515a0.jpeg
Here’s a photo

All I can add is that I'm putting together a bike with a 1" threadless a fork, and am planning on replicating the proportions of a classic 7 stem. I will probably have a little more spacer stack than your mock up. I'm not sure of the look, but I'd be surprised if I was building a death fork. If this was a real and present danger I guess I could mill off the the extension of a quill stem and install it wedge and all inside the steerer, That way I could go from obviously fool hardy to obviously paranoid in a matter of minutes.

That kind of saddle will pitch you forward and place unnecessary pressure on your back and your wrists - I would advise a more conventional flatter saddle . I'm assuming the saddle is that high (compared to your stem) because of your inside leg measurement. A rudimentary saddle height adjustment (with a different saddle) is place your shoe heel (not the pad of your shoe) on the pedal at the 6 o 'clock position with a fully extended leg - that's your correct saddle-inside leg position. The aim is to lower the seat and not raise the stem. Slide the seat fully back and I'm assuming your using a north-bend sit up type bar rather than drop bars. If not possible I'm afraid the frame is too small for you. Having said that, it is a large frame, so I'm assuming you are well over 6' tall.

Jeepes Johno, that was a lot of assumptions squeezed in to one post 🥸

The saddle height is correct but everything else is in flux.

I grabbed the seatpost and saddle off the closest bike (my roadbike) to get a handle on where I want my hands to fall.

I have a Brooks pro lurking about but I may fiddle with the smp first.

Saddle height is only 73cm in the photo and the frame is a 56. I tried a 58 and preferred this one.

I’m not set on North Roads I may try a something like a Jones Bar or a Soma Dream Riser bar.

Spaced out
 

My inside leg is 33 inches and I'm 5 10. I ride 56, prefer 58 but have 3 or 4 60cm c-c bikes. I can't vouch for the safety side but my beater bike has a drop of 9 cms from the seat to the horns.My TT bikes are about 12 cms. I don't have any spacers as the 25 bikes that I ride are dialled for me only. Most are quill but my 853 bike is 1" threadless like yours.
An AHEAD center bolt has a very limited reach (unlike a quill stem) and is only a 8 mm x 50mm bolt whereas a quill is 21mm shank inside a steel steerer inside two sets of bearings and is usually about 150mm deep.
From what I understand an AHEAD steerer must be cut to fit - the stacks you see in shop bikes are a prelude to the cut and if my memory is right are stacked above the stem in the shop prior to the sale.
Because I ride and fix a great many bikes many folks come to me with problems their LBS can't fix. Usually it's because someone has sold them a bike that doesn't fit no matter how much they spend.
Every day I see folks struggling into a typical UK headwind on bikes that are not dialled in for their size.