Ritchey stem size issue

[LegendRider]

The pictured stems are supposed to be identical - alloy WCS, 84 degree, 12cm, 31.8mm clamp. But, the one on the left measures 12.5 cm despite being labelled 12.0 cm. How did this happen?!?

[guido]

Some guys just got bigger stems. :rolleyes:

[Gummee]

Ummm some of us are bad at maths?

Dunno

M

[Limonade]

dunno, but this guy would surely be interested in finding out...

http://forums.thepaceline.net/showthread.php?t=166739

(also, other posters in that topic have mentioned similar variances)

[CPP]

Jesus, what a rip off!!!! How much for the 12.5?

[christian]

I've seen this on so many different brands of stem. Not sure how they cast them, but it seems an awfully imprecise process.

[soulspinner]

I've seen this on so many different brands of stem. Not sure how they cast them, but it seems an awfully imprecise process.
+1. I had an old 3ttt Forgie that measured 105 mm and was supposed to be 100....

[Black Dog]

I've seen this on so many different brands of stem. Not sure how they cast them, but it seems an awfully imprecise process.

It is the labeling that is the issue here. However, actual measurements between brands differ for the same nominal size.

[nooneline]

Is one a 6deg and the other a 17deg stem?

That would explain some of the difference.

[KonaSS]

Yep, I have no idea how, but this happens all the time. Most of us probably have a few stems lying around. Just measure them, you will see some crazy variation.

[oldpotatoe]

The pictured stems are supposed to be identical - alloy WCS, 84 degree, 12cm, 31.8mm clamp. But, the one on the left measures 12.5 cm despite being labelled 12.0 cm. How did this happen?!?

We hung out stems and saw this fairly often. 2 110mm stems, hung on same hook, both marked 110 and one is clearly longer. Sold only Ritchey also.

[nooneline]

It looks like the one on the left is a 17deg stem and the one on the right is a 6 deg stem. I'm saying this based on the fact that it looks like the steerer angles are different, based on what you can see if the surface underneath... and because that's what Ritchey sells.

I don't know how companies measure stem length if they make the same model in different angles - if they just measure the length, then, 110mm of stem only turns into 110mm of reach if you're using a -17deg stem (this is basic trig; a hypothetical stem sticking straight up from the steerer can be 110mm long but will obviously have 0mm of reach). In fact a 110mm stem at 17 degrees has 10mm less reach then a 110mm stem at 6 degrees.

[christian]

It is the labeling that is the issue here. However, actual measurements between brands differ for the same nominal size.

No. Two stems of same make, model, angle, and nominal extension size can vary in length. I have seen it with Deda, 3TTT, and (now) Ritchey.

If I had to guess, I think the forging dies wear and get larger as more stems are forged in each die. Then in turn, more material is machined off the forged blank, but the length gets longer.

So, new forging die - short stem. Old die - long stem, until they get to the wear limit, and then they're replaced.

If that's true, I bet you can find nominal 110mm stems in 109, 110, 111, 112, 113, 114, 115mm, but that stems that are between 115mm and 119mm are very very hard to find.

[LegendRider]

It looks like the one on the left is a 17deg stem and the one on the right is a 6 deg stem. I'm saying this based on the fact that it looks like the steerer angles are different, based on what you can see if the surface underneath... and because that's what Ritchey sells.

I don't know how companies measure stem length if they make the same model in different angles - if they just measure the length, then, 110mm of stem only turns into 110mm of reach if you're using a -17deg stem (this is basic trig; a hypothetical stem sticking straight up from the steerer can be 110mm long but will obviously have 0mm of reach). In fact a 110mm stem at 17 degrees has 10mm less reach then a 110mm stem at 6 degrees.

It's the angle from which I took the picture. Both stems are 84 degrees and labelled as such.

[Mark McM]

If I had to guess, I think the forging dies wear and get larger as more stems are forged in each die. Then in turn, more material is machined off the forged blank, but the length gets longer.

Wear on a forging die won't wear 5mm in one direction only. And it sure won't move the entire clamp flange (both inner and outer faces) 5mm in the same direction. These stems were made with two differently dimensioned dies.

My guess is that these two stems were made with two different dies (perhaps one being made after the other wore out). For one of the dies, the machinist mis-read a datum point on the drawing. Forging dies are expensive to make, so by the time the error was found, they must have thought, "Oops! Oh, well, it's close enough - we'll continue to use this one until it wear out, and we'll fix it with the next die."

[BdaGhisallo]

It's due to forging variances. I can't recall where I read it, but it was something along the lines of the forging tolerance being plus or minus the nominal size. I have a boatload of Ritchey stems in 110 and 120 and no two are the exact same length. One day (when I must have been reaaaallly bored, I measured them on a handle bar jig and labelled them with their actual length ala Team Sky. There was a lot of variation, both in the 4-axis stems and the newer C260 stems.

I guess it's what we have to tolerate if we prefer forged stems over machined ones. I recall Grant Peterson in a Rivendel reader waxing about the wonders of forging for stems over machining. The technology has surely moved on since he wrote that some 15-20 years ago but it was heavy on talk about metal grain and stress risers. Convinced me, and I've put up with forging variance since then.

[soulspinner]

It's due to forging variances. I can't recall where I read it, but it was something along the lines of the forging tolerance being plus or minus the nominal size. I have a boatload of Ritchey stems in 110 and 120 and no two are the exact same length. One day (when I must have been reaaaallly bored, I measured them on a handle bar jig and labelled them with their actual length ala Team Sky. There was a lot of variation, both in the 4-axis stems and the newer C260 stems.

I guess it's what we have to tolerate if we prefer forged stems over machined ones. I recall Grant Peterson in a Rivendel reader waxing about the wonders of forging for stems over machining. The technology has surely moved on since he wrote that some 15-20 years ago but it was heavy on talk about metal grain and stress risers. Convinced me, and I've put up with forging variance since then.

plus or minus .25mm seems like a lot of variance!

[BdaGhisallo]

plus or minus .25mm seems like a lot of variance!

A quarter of a mm wouldn't be so bad but it's the 1/4 cm variance that you have to look out for!

Cheers.

[irideti]

I have a few 110mm FSA OS-99 stems and all of them measured 115-118mm. The guy did my fit told me he has seen a lot of stems longer than their spec, but never shorter.

[soulspinner]

A quarter of a mm wouldn't be so bad but it's the 1/4 cm variance that you have to look out for!

Cheers.

Ha Ha just reread that:bike:

[Mark McM]

It's due to forging variances. I can't recall where I read it, but it was something along the lines of the forging tolerance being plus or minus the nominal size.

5mm forging tolerance over 120mm length (4%)? Not a chance. (0.4% error, maybe.) If forging tolerances were this bad, none of our forged machine parts would fit together.

The length error didn't occur when two stems were forged with the same die tolls, the error occurred when two different die tools were created out of tolerance with each other.

[John H.]

If you want to part with the shorter one- let me know.

The pictured stems are supposed to be identical - alloy WCS, 84 degree, 12cm, 31.8mm clamp. But, the one on the left measures 12.5 cm despite being labelled 12.0 cm. How did this happen?!?

[blasdelf]

5mm forging tolerance over 120mm length (4%)? Not a chance. (0.4% error, maybe.) If forging tolerances were this bad, none of our forged machine parts would fit together.

The length error didn't occur when two stems were forged with the same die tolls, the error occurred when two different die tools were created out of tolerance with each other.

it's not two die tools that were created differently (or at different stages of wear)

it's an adjustable-length tool for the initial forging operation that closes the second end of the tube