Geometry, mathematics and the newbie.
 

hello,

Go a real newbie style question... please be gentle.

I have a thirty year old road model, that I'm trying to tame.
I have some spare road bars that I want to replace the riser bars,
that were put on it by the last owner.

I want to use a threadless stem, so it's easier to swap out handlebars.

My question is : What stem do I need ? ( the two sizes in bike speak, what is the Bar Clamp Diameter and the tube size ? )

The Clamp Diameter at the moment on the riser is : circumference is roughly = 7cm 2.8 inches.
The handlebars, taper from 8.3cm/3.25 inches in the center to 7.3cm/2.9 inches on either side and down into the drops. Do I have a 1" or 1 1/8" fork ?

Many thanks in advance,
Psy.

Are the current fork & headset threaded or threadless? If you are looking to convert a threaded set up to threadless just to make it easier to swap bars, just buy a quill stem with a removable face plate like this:
http://www.niagaracycle.com/product_...ucts_id=421202

Unless the bike was modified, it's highly likely that you have a 1" threaded fork. If that's the case, you can't just buy a threadless stem and put it on (unless there's some sort of work-around that I'm unaware of.) You would need to buy a new threadless fork, and a threadless headset.

Getting a quill stem with a removeable faceplate as suggested is a great idea to be able to swap bars. Just measure the rise and reach of your current stem and buy the new one accordingly. Of course, you can get a stem that has more/less reach/rise depending on how happy you are with the positions offered by your current stem. Also measure the diameter of your stem, or the ID of your steerer tub. The new stem must have the same diameter or it won't fit (or it will be wobbly.)

Threaded fork .. a couple approaches ...get an adapter stem ,
Its a plug ,quill 7/8" at the bottom , 9/8" at the top.
so you can clamp a threadless stem onto it..

Dimension [QBP] makes a quill stem thats adjustable in angle , and has an open faceplate for your bar swaps

not as ugly [subjective] as the profile example, but black finished.. .

Thank you all for replying... So if I have handlebars that are 8.3cm/3.25 inches in the centre. What size bars are these 25.4, 26, 38.1, when looking for the right stem to properly fit it ?

Secondly what is the other end of the stem sizing - is it a 1-1/8" stem or 1", if the one already on it is roughly 7cm/2.8" in circumference ?

I am thinking, that i should be looking for a stem that is ( 1-1/8" by 26 ) - is that right ?

I don't think you fully understood the posts above relating to steerer tube diameter and threaded v. threadless. I would reread them.

What do I need read in order to understand ? The dimensions I have, I can't find conversions for ?
Hoped someone here, who has a lot of experience might just easily say what I need.

It's a threaded headset, I am looking for a quill with 'a removable face plate' as stated by 'CACycling'
but from the sizes I have, what stem do I need to look for ? What size probably is the quill stem already installed, which is ( 7cm/2.8" ) and what size are the handlebars, which in the centre are ( 8.3cm/3.25" )

You need better measurements. From what you've given us, I'd guess you have a 1" steerer. But the bars could be 25.4 or 26, it's really too close to call the way you are measuring. Try looking closely at the drop bars for any writing on them (usually at the clamp area) to see if the size is marked on them.

30 year old road bike - Chances are pretty good it's 1" stem. Clamp diameter could be 25.4 or 26 or even 26.4, I think. If there's a riser bar in there, it's probably 25.4.

I guess Salsa Quill stems are officially history now, but there's still Profile Designs quill stems with faceplate for easy bar changes.

I agree.

First off you most likely have a 1 inch threaded fork and headset with a quil stem at present. If you think you have anything different then you will need to measure the diameter of the fork's steer tube for yourself. We can't read minds or see things from here. A great resource for checking things out first before asking is www.parktool.com/repair . The diagram of the bike is loaded with links that will take you to other pages that have pictures of the different options and information on how to measure the stuff to find out what you have.

Without getting a newer threadless 1 inch fork and headset the only way you can switch to a threadless stem is to get a quill to threadless adapter. Once you have one of those and assuming you get a 22.6 to 1 1/8 adapter THEN you can shop for a 1 1/8 to 26mm threadless stem to fit a set of drop road bars.

On the sizes you measured and reported above they don't do us any good. The stem and clamp sizes work in diameters, not circumferences. Use a set of cheap calipers to measure them again. Once you measure this stuff then you'll realize what sort of stem clamp sizes you need.

As fietsbob suggested, this is a quill adapter...
http://store.velo-orange.com/media/c...adaptors_1.jpg

It replaces the 1" quill stem that you probably have on your bike. The top of the adapter is sized to accept stems that are used on 1-1/8" threadless forks, such as this...

http://store.velo-orange.com/media/c...s/t/stem26.jpg

...which can be purchased for either 25.4 or 26.0 bars (plus 31.8mm). If you purchase the 26.0, but your bar is actually 25.4, you can shim it with aluminum cut from a can. Or you can spend more money on fancy shims..

Thank you everyone, I appreciate your patience.

So is a 'quill adapter' the best way to go, or can still get a 1" quill with a... ( whatever size these bars are... ) stem ?

The bars by the way are Nitto's 177 ( Noodle bars ) - Do they come as one size for the central area that attaches to the stem ?

http://www.google.com/products/catal...0CGoQ8wIwCDgK#

http://www.google.com/products/catal...d=0CG8Q8wIwCA#

Noodles are 26.0mm

26 just at the centre ?
...because the noodle has a raised centre
and then is noticeably smaller down and into the drops.
It that part 25.4 ?

I think 23.8mm is the most common diameter for the grip area of road bars.

http://www.google.com/products/catal...d=0CG8Q8wIwCA#


Thanks for the links... just an aside, but isn't the join from the stem to the quill ugly as sin.
( Looks like the stem crash landed into the quill - or some strange sexual sculptural act, we'd all like to be acting out )
The two piece join of a quill adapter and a stem is by far ( ...if expensive ) the more attractive option ( as suggested by desertdork )

Thanks !

Yep, Profile stems are hideous. Their primary market is triathletes. Shame the Salsa quills are all gone. I couldn't even find any on eBay. There have been a couple other removable faceplate quill stems, can't remember the makes, however. Seems like Ritchey had one at one point.

Profiles are definitely the cheap/easy solution, perhaps a little lighter than the adapter+threadless stem.
The other option I don't believe mentioned yet is that you could go for the gusto and source a 1" steerer threadless fork + headset + stem.

Price/Looks/Weight considerations depend on what the bike is and what you plan to do with it.

The relationship between circumference and diameter is C=Pi*D where Pi=3.1415 - so your 8.3cm is about a 26.4mm diameter and the 7m is about 22.2mm. It is tough to accurately get diameter by measuring circumference but the 26.4 is an intriguing number as certain Italian bars from that era were 26.4 which is not a common size seen today. And the 22.2 is indicative of the diameter of the end of a quill stem that fits in a 1" fork.

Or maybe this...

http://ecx.images-amazon.com/images/...WL._AA300_.jpg
http://www.amazon.com/Deda-Murex-Qui.../dp/B0028NRFZK

Well yeah, but 8.3cm still comes out closer to 26.0

26.4 * 3.1415 = 84.0
26.0 * 3.1415 = 82.7

...and Nitto is Japanese

My slide rule may be in need of adjustment but I get:

26.4*3.1415 = 82.94
26.0*3.1415 = 81.68

???

sheesh, you used a slide rule? Cheater!