Did you think big sprockets on road bikes was a new idea?

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Brucey
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Did you think big sprockets on road bikes was a new idea?

Postby Brucey » 3 Sep 2018, 10:03am

I stumbled upon this Sun Tour ephemera on 'Disraeli gears' and I thought it deserved to be seen more widely

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That the freewheel is identified as an '8.8.8' model dates it to (I think) before 1973. After about this date they branded the same freewheel as a 'perfect'.

A 34T sprocket was (at the time) huge, (hence 'big new'... :wink: ). It appears that the RD had a 36T total capacity so you could have a 14-34 freewheel and up to a 16T chainring interval, leaving scope for a half-step system or an alpine double.

A bit like this;
http://ritzelrechner.de/?GR=DERS&KB=40,46&RZ=14,18,22,27,34&UF=2150&TF=90&SL=2.6&UN=MPH&DV=gearInches&GR2=DERS&KB2=30,46&RZ2=14,18,22,27,34&UF2=2150

I'm not sure which other manufacturers offered similar sized sprockets at the time. That the derailleur design was 'correct' can be judged by the fact that all SRAM mechs and many current shimano models are basically built the same way, i.e. with one sprung pivot and a slant parallelogram. Sun Tour started building mechs this way in about 1964.

cheers
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ANTONISH
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Re: so you think big sprockets on road bikes is a new idea?

Postby ANTONISH » 3 Sep 2018, 10:17am

Interesting that Brucey.
I've just made an alpine double 44/26 coupled with a XT rear changer and 12 - 36 rear cassette (9sp).
I found my double Sora changer wasn't compatible and dug up an old Dura - Ace changer which works very well. My only problem is that the short cage means that on the smaller rear sprockets there is some rubbing but as that is after the ranges overlap not a problem.

Brucey
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Re: so you think big sprockets on road bikes is a new idea?

Postby Brucey » 3 Sep 2018, 10:33am

IIRC old model Dura-Ace FDs had a 'tail' that included an M4 bolt and a tube spacer. It is possible to fit a longer bolt and a longer spacer so that the back of the mech is flared more and there is less rubbing when you are cross-chaining.

However my problem with old DA FDs is that the mech just isn't wide enough at the front; the slightest amount of chainring flex results in intractable rubbing.

cheers
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Bonefishblues
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Re: so you think big sprockets on road bikes is a new idea?

Postby Bonefishblues » 3 Sep 2018, 11:06am

My first 'proper' bike was a Raleigh Royal with a 52/42 chainset and one of those 5 speed Suntour 14-34 cassettes. That would have been early 80s.

Brucey
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Re: so you think big sprockets on road bikes is a new idea?

Postby Brucey » 3 Sep 2018, 11:36am

whist we are on SunTour stuff this

http://euphras.blogspot.com/2011/10/how-to-touch-up-vintage-suntour-index.html
Image

show how to refurb accushift shifters, including a method of recovering worn indexing parts.

This link
http://suntourcommand.blogspot.com/

is to a page where someone has commissioned newly made inserts for SunTour command shifters that convert them to index 'road' Shimano 10s (not 4700 presumably).
Image
The post is old (from 2013) but it has been updated in 2017 and I think the inserts will also fit other SunTour accushift type shifters

cheers
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peetee
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Re: so you think big sprockets on road bikes is a new idea?

Postby peetee » 3 Sep 2018, 12:07pm

Nicely trawled Brucey. While the gear spacing on a 5 speed 14-34 block looks collosal it probably isn't far off a 5 speed Sturmey for total capacity (too lazy to do the sums, sorry) and I coped with one of those for a few years. Combined with a sensible combo of front rings to split the difference it would be a bad set up at all with the added advantage that cogs and chain longevity would be vastly improved over a contemporary 1x10.
Current status report:
Latter side of fifty and feeling less than nifty.
Too many bikes on pegs and too few miles in the legs.

mig
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Re: so you think big sprockets on road bikes is a new idea?

Postby mig » 3 Sep 2018, 3:20pm

sprockets from that era always look so much more 'meaty' and durable.

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Cunobelin
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Re: so you think big sprockets on road bikes is a new idea?

Postby Cunobelin » 3 Sep 2018, 3:26pm

mig wrote:sprockets from that era always look so much more 'meaty' and durable.


Problem is that the distance between hub and frame is finite.

If you have 6,cogs in that space, they can be reasonably thick, but as you get to7, 8, 9 or 12 the only way to fit them in is to make them thinner and thinner along with a narrower chain.

mig
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Re: so you think big sprockets on road bikes is a new idea?

Postby mig » 3 Sep 2018, 3:34pm

Cunobelin wrote:
mig wrote:sprockets from that era always look so much more 'meaty' and durable.


Problem is that the distance between hub and frame is finite.

If you have 6,cogs in that space, they can be reasonably thick, but as you get to7, 8, 9 or 12 the only way to fit them in is to make them thinner and thinner along with a narrower chain.


yup. the thing is that, when i ride a geared bike, i only use about three of 'em anyway for the majority of the time. i do a fair bit of (unladen) climbing too.

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Cugel
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Re: so you think big sprockets on road bikes is a new idea?

Postby Cugel » 3 Sep 2018, 4:48pm

In 1976 I lived next door to a lad who has a Puch Free Spirit bike like this one:

http://oldtenspeedgallery.com/blog/wp-c ... cer-09.jpg

It had Suntour GT gears with a 14-34 or perhaps even a 36 sprocket. I remember it as we went for many a ride in The Bowland Fells and The Yorkshire Dales around Settle/Ingleton - him with his 30 summick sprocket and probably a 36 small ring too, with me on a 42/21 bottom gear.

His Puch Free Spirit weighed about 40llbs whereas I was on a lightweight Ribble 531 of something like 22llbs. Nevertheless, he kept up on the really steep bits since I had to weave side to side to get up on 42/21 whereas he could go straight whilst a-twiddling-oh.

These days my fast summer bike has 34/50 at the front and 14-36 at the back. Having had the lesson from that Puch bike, long ago, I too now avoid the weaving up Fleet Moss. 50X14 is still good enough at sprinting for the Grassington sign on the way down. :-)

Cugel

MikeDee
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so you think big sprockets on road bikes is a new idea?

Postby MikeDee » 3 Sep 2018, 4:57pm

mig wrote:sprockets from that era always look so much more 'meaty' and durable.


I found that it wouldn't take long before Suntour cogs skipped. Must be made of soft steel as compared to Shimano.

Bonefishblues
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Re: so you think big sprockets on road bikes is a new idea?

Postby Bonefishblues » 3 Sep 2018, 5:03pm

MikeDee wrote:
mig wrote:sprockets from that era always look so much more 'meaty' and durable.


I found that it wouldn't take long before Suntour cogs skipped. Must be made of soft steel as compared to Shimano.

Weighed an absolute ton, mind!

pliptrot
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Re: so you think big sprockets on road bikes is a new idea?

Postby pliptrot » 3 Sep 2018, 6:41pm

Soft steel or not, the demise of Suntour is a loss to us all. They were innovative, great engineers and probably never did subscribe to cheap populist cycle equipment marketing: the number of cogs on the back is all that matters.

I'm a trendy consumer. Just look at my SM-G900F using Tapatalk

Brucey
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Re: so you think big sprockets on road bikes is a new idea?

Postby Brucey » 3 Sep 2018, 6:45pm

I think that the large suntour sprockets with splines were slightly harder than the smaller threaded ones and neither was quite as hard as a shimano UG sprockets were, BITD. All were a lot harder than the HG sprockets we use today.

Full height teeth (as found on older freewheels) are susceptible to the slightest hooking; once even slightly hooked they will skip under load with a new chain. Wearing them back to a sensible shape takes ages; when compared with an HG sprocket there is more material to remove and it is harder, too.

When I used SunTour New Winner freewheels, the small threaded sprockets saw little wear so lasted for ages, and the larger splined sprockets saw little wear and were (although they recommended not) anyway reversible. The ones I used to wear out most often were the threaded sprockets (that couldn't be turned) in the middle of the freewheel; usually 15, 16, 17, 18, 19T. Regardless of it being a touring or racing freewheel, most of mine had a threaded 16T and/or 17T sprocket in there somewhere, and I was eventually in danger of running out of good ones to use. I tried de-hooking them and whilst this was a great improvement it still meant the one would get skipping under high load, so no out of the saddle frenzies were possible in some gears. With those sprockets it took thousands of miles to wear them back to a shape that wouldn't skip under high load, and in fact I'm not sure I ever did wear one back to the point that I would trust it completely in a full-on out of the saddle sprint effort. HG sprockets seem a lot more forgiving than that.

For an HG sprocket to retain a useful tooth shape, the inevitable wear in the loaded areas (that can create the distinctive hooked shape) needs to be balanced by wear in the (relatively) unloaded areas of the tooth form. These see some load as the chain engages and disengages; the rollers slides over the surface of the tooth form and also (because they are always a loose fit on the chain) rattle against the tooth as it engages too. But a few microns too much wear and the chain won't engage so easily when under load, and slipping ensues.

FWIW if you build a wheel to 135mm OLN and optimise the wheel dish, you can fit 7 sprockets (of ~1.9mm thickness) and there will be almost zero dish in the wheel. A 2x7 or a 3x7 setup with carefully chosen sprockets provides enough gears for almost any purpose.
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Brucey
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Re: so you think big sprockets on road bikes is a new idea?

Postby Brucey » 3 Sep 2018, 7:16pm

pliptrot wrote:Soft steel or not, the demise of Suntour is a loss to us all. They were innovative, great engineers and probably never did subscribe to cheap populist cycle equipment marketing: the number of cogs on the back is all that matters....


well sort of; arguably they started the 'race for more'; more technology and more gears for sure. Arguably Shimano just came along later and did the same sort of thing but better.

SunTour first introduced a fancy freewheel called the 'Winner'. This was a high tech lightweight freewheel but at a fraction of the cost of fancy European lightweight freewheels. It had a few flaws however , so a couple of years later they launched the slightly cheaper/heavier (and considerably stronger) 'New Winner' freewheel.

To put this into context most folk were using 5s freewheels and whilst standard spaced 6s existed (and was popular in the pro peloton) it wasn't the choice of normal mortals; for example even SBDU frames came with a default 120mm 5s rear spacing and 126mm 6s was to special order only. Well the New Winner was not terribly expensive and could be configured as standard 5s or standard 6s (5.5mm sprocket pitch) and (crucially) could also be built in new 'Ultra Spacing' (5.0mm sprocket pitch) as a 6s or 7s unit, to fit 120mm OLN or 126mm OLN respectively. The new Sedisport chain worked (but in hindsight shifted rather poorly) on these 'ultra-spaced' freewheels, so you could (literally) go 'one up' on your chums simply by buying a freewheel and chain; an upgrade at 120mm OLN to 6s and 126mm OLN upgraded to 7s. Heck it would even (in standard 6 or ultra 7 fitting) take a 12T sprocket, and everyone needs one of those.....

Of course, callow youth that I was, I thought all this was 'brilliant'

Image

and I bought into it in a big way. I remember thinking that when the all new, shiny, top of the tree Dura Ace 7400 groupset was launched, it was already a bit behind the times; after all I'd had 7s for several years by then and the DA 7400 stuff was 'still only 6s' to start with.

So some of the blame for 'more' has to lie at the doors of SunTour. But when shimano picked up the ball and ran with it, SunTour struggled to keep up. In just a few crucial years shimano launched feature-heavy MTB groupsets and road groupsets that only made sense if they were fitted as a complete system; such bikes appealed to consumers and outsold those with alternative equipment. SunTour tried to launch their own groupsets but it was too little, too late, and they went from being #1 to a distant second place in just a few years.

Maybe shimano would have done what they did do anyway. But maybe SunTour showed them that more sprockets = more sales and set them off on the path they took.....

cheers
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