Dropout spacing confusion
 

I converted my mid 80s road bike from 6 speed freewheel rear (126 spacing) to a 7 speed free hub rear with cassette. The hub came from a 700c road bike rear wheel of a late 80s early 90s Trek. It is a Shimano Exage hub. I measured it and it is 130 on the spacing. I cold set my rear drop outs and all is good. I just recently stumbled across some info that says 6 and 7 speed road bike rear spacing is 126 and 7 speed mtb spacing is 130. But this hub was from a road bike. What am I missing here?

There's no Hub Spacing Police. Those numbers are merely reflections of how most manufacturers spec'd their bikes. Bridgestone stuck with 126mm 7s on their mountain bikes for a while, then resisted the move to 135mm a few years later, and got Shimano to make them some special 130mm Deore hubs.
There are two reasons I can think of for the difference.
One, mountain bikes used triple cranks, which require the cranks be more outboard from the frame, especially on non-ferrous frames. Moving the cassette farther outboard keeps the chainline good.
Two, mountain bike rear wheels are more likely to be subjected to lateral loads, so the wider spacing decreases dish and equalizes spoke tension side-to-side.

I just went out and remeasure the hub spacing just to make sure I wasn’t crazy and as best I can get a measurement through my spokes with my calipers it’s about 130.5 so basically a 130 spacing. I had been led to believe that when they went from the free wheel hub to the Cassette free hub the spacing jumped to 130 even though it was only a 7 speed cassette. At least I’m all set if I ever want to put another free hub body on some day and put in an 8 speed cassette LOL

Also remember that late 80's-early 90's was the transitional time for spacing going from 126 to 130. It was not unusual then for manufacturers to make frames in 128 spacing so that either type of hub OLD could be used. It was also a transitional time for manufacturers, Shimano included, and sometimes a bike that was supposed to get a 126 rear freehub instead got a next-level-up 130 spaced freehub with a 4.5mm spacer to correctly space out the cassette. That may be the case here. I've certainly been surprised from time to time, especially with some 7 speed tricolor bikes that came with an 8 speed 130 hub and a spacer.

Note that there were 7 speed Shimano freehubs during that period (e.g. 105 series 1051) and even earlier there were 5 and 6 speed Shimano freehubs on 600 and Dura Ace.

This news might make many people feel insecure.

Well, there MIGHT be, but if so, they're secret....

Exage was kind of a nebulous group -- some parts were clearly "road" or "mountain" but Exage oftentimes occupied a space somewhere in-between for hybrids or sport-touring or other not-premium bikes. I've had a couple of 130mm-spaced 7-speed Exage hubs pass through my hands. (I respaced them for my 126mm bikes.)

In other news, now that you've stretched out your bike to 130mm, there's nothing stopping you from moving up to 8-11 speed. ;)

I have one set of 126 wheels I respaced to 130 by adding two spacers. Unless you've had the wheel since they were new...


But when 130 became common for road bikes, I imagine even the cheaper hubs in 7 were spaced that way so Trek didn't have to produce different frames for the 1000 vs the 1400, for instance. 8 speed was reserved for nicer groups in that period.

Did anyone but me ever play the old Hitchhiker's Guide to the Galaxy computer game? (If not, you still can: Hitchhikers Guide to the Galaxy 30th Anniversary) One of my favorite gags in the game was that if you consult the Guide about the Galactic Security Agency agents from the Galactic Security Agency show up, rough you up a bit, tell you there's no such thing as the Galactic Security Agency and never to consult the guide about it again, then leave. The exchange above about the Hub Spacing Police reminded me a bit of that.

Perhaps your reference for a 7 speed road bike with 126 mm rear spacing was for an Ultra-7 freewheel?

Dean

It was Sheldon’s sight. He had s chart/table

Shimano 7s road were 126 too. Freehub and freewheel.

According to VeloBase the Exage 500EX was available with 126, 130 or 135 spacing.

I'll also add that it's a pretty simple matter to replace the freehub body on a 7-speed Shimano hub to make it 8/9/10 speed compatible, and when doing so one would probably make the spacing 130.

I never played the game... but 126 divided by a triple is 42... coincidence?? Did they have to change the rear spacing to remain secret?

No such thing as a non "Ultra" 7-speed AFAIK.

As long as the wheel is dished properly, I doubt you'll have a problem.

Suntour's 7s spacing was narrower than Shimano's and Sachs-Maillard. Regina also made an ultra-7 FW IIRC

All my CV bikes are 126mm rear spacing, even the one with the 7 speed Shimano cassette. Tim

120 spacing was for 5 and ultra 6 freewheels.

126 spacing was for standard 6 and ultra 7 freewheels and cassettes on road bikes. All of the 7 speed stuff was about 5.0 spacing - Shimano and Suntour.

130 was for 8 and greater speeds, but some cheaper bikes still came with 7, but in 130 spacing.

I was under the impression that all of the above had roughly 5mm center-to-center spacing (excepting SunTour Micro-Drive.) What I was trying to get at was that there wasn't a "wide" variant of 7-speed.

Yup, a select number of Shimano 7 sp freehubs fit 126, depending on the dropout design. Sometimes you had to futz with it.

About.
7 speed is all narrow or "ultra" spaced, that's why it will fit in basically the same space as a standard 6. But there are a few differences between 7s.
The overall widths are about the same. Shimano/Sachs has the same spacing all the way across. Suntour's outer two spacers are thicker than the inner four though. This makes it tough to dial in the shifting across systems.

:thumb: +1

A few years ago- having in the moment actually forgotten that I did indeed knew better (certainly a sign that I'm getting older), I made the assertion that all 126mm Shimano freehubs were UG, & incompatible with later HG systems.

Doh!!

I'd totally spaced off the fact that about 4 years before, I'd actually converted a 126mm, Shimano 105/1055 HG 7sp hub to 130mm/ 8sp, that is, to the same spec as the 105/1056.

All it took was swapping out the hub body, and swapping out the axle & spacers. Shimano's 126 & 130mm hub shells have the same dimensions (I can't remember offhand if the shell interface itself is different for UG & HG hub bodies. It's been a while; I seem to recall it's the actually same for both types).

The HG 7sp hub bodies are Bronze & slightly shorter (about the same length as a UG body) to fit the 126mm spacing; the HG 8sp are Black & about as long as 9sp body. If they have a little indelled line encircling the body, about halfway down, it's one of the UG/HG bi-compatible transition bodies. The latter also have both types of lockring threadings.

But that doesn't mean that Suntour 7 is narrower in any important way - uses the same width chain as all the other 7 speed systems. Which is not what your earlier comment made it sound like - it is no more "ultra" than the rest.

If indexing is important to you, then it's narrower in the only way that is important.