http://citycyclingedinburgh.info/bbpress/ CityCyclingEdinburgh Forum » Topic: "Maintenance free" bike saga continues en Mon, 18 May 2026 14:43:47 +0000 http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=3#post-79317 Tue, 24 Jul 2012 20:27:13 +0000 scooby214 79317@http://citycyclingedinburgh.info/bbpress/ <p>In my inspection of the hub, it appears that the spring could be replaced without too much difficulty. I don't know if the existing spring could be wound tighter. If you made a new spring, I think it would be a trial and error experiment. </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=3#post-79135 Tue, 24 Jul 2012 07:42:37 +0000 Dave 79135@http://citycyclingedinburgh.info/bbpress/ <p>Apparently there are three shift points depending on which hub you get: 12, 14 or 18 km/h (7.5, 8.7 or 11.2 mph), yet mine shifts consistently at just over 10mph. Weird!</p> <p>I am thinking of opening it up to do something to the spring / add another one. The operation is so sweet, but the shift point so inappropriate, that it seems worth the risk. </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=3#post-79124 Tue, 24 Jul 2012 02:17:34 +0000 scooby214 79124@http://citycyclingedinburgh.info/bbpress/ <p>I recently built a 700c wheel, using the freewheel version of the SRAM Automatix hub. I installed it on a drop bar chromoly bike that I use for commuting. Using a 700c wheel with 700x32 tires, my shifting is consistent at 11.5mph. I used a 38t chainring and a 22t rear cog (a Shimano Nexus cog), to get 46 gear inches in low gear and 65 gear inches in high. With this gear setup, I can sprint through intersections and it shifts at just the right time. If I pedal casually, I have to get my pedal cadence up pretty high for it to shift. I like it this way, as it allows me to pedal at a comfortable 75rpm in low when climbing hills. I spin out at a fairly low 20-23mph, but I'm a spinner and the hub allows me to spin comfortably at a reasonable cadence. The hub works splendidly with this setup, but I think the 700c wheels are part of the reason for this. </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=3#post-77628 Wed, 11 Jul 2012 09:00:36 +0000 chdot 77628@http://citycyclingedinburgh.info/bbpress/ <p>Won't be "maintenance free" but fairly 'stripped down' - and a bit cheap looking -</p> <p><a href="http://www.flickr.com/photos/huggerindustries/6967143714/"><img src="http://farm8.staticflickr.com/7139/6967143714_84775c3c3a.jpg"></a><br /> <a href="http://www.flickr.com/photos/huggerindustries/6967143714/">Google Bikes Arrive on Campus: a Fleet</a> by <a href="http://www.flickr.com/people/huggerindustries/">Hugger Industries</a>, on Flickr </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=3#post-77212 Fri, 06 Jul 2012 16:23:59 +0000 Dave 77212@http://citycyclingedinburgh.info/bbpress/ <p>Well, it's used for all cycling inside the bypass. It takes 20-25 minutes for 5 miles on the commute (including red lights) which is a true average of 12-15mph (but those red lights mean riding speeds are presumably a good bit higher).</p> <p>Adding the trailer doesn't make it much slower unless I'm hauling a kitchen appliance! I suppose it takes a couple of mph off on the hills? </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=3#post-77210 Fri, 06 Jul 2012 15:50:21 +0000 crowriver 77210@http://citycyclingedinburgh.info/bbpress/ <p>Nice graphs Dave. I see the issue. Unlikely to be able to obtain a 25T sprocket for that hun, perhaps. What I'm missing is the third variable, chainring size. More expense, I grant you, maybe something you don't want to look at. However it might help extend that green zone a little?</p> <p>Ultimately though, the problem is you only have two gears! If only there was an Automatix 3 speed, eh? Ratios of say 0.71, 1.0, and 1.37 ?</p> <p>Also, I must say that your "normal use" range of speeds from 15 to 25mph is rather on the sporty sprinter side of cycling. I thought this bike was a trailer hauling workhorse, not a racer? </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=3#post-77197 Fri, 06 Jul 2012 15:05:21 +0000 Arellcat 77197@http://citycyclingedinburgh.info/bbpress/ <p>For different values of 'user servicable', I guess. I've read that some have taken to modifying the springs to effect a later shift, essentially making the springs stronger so that the weights engage later. It might be worth experimenting with adding a second, weaker, spring each side so that you don't have to modify the originals. </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=3#post-77191 Fri, 06 Jul 2012 14:40:10 +0000 Dave 77191@http://citycyclingedinburgh.info/bbpress/ <p>Aye, but it's a shame because the build quality of it (so far - touch wood!!) is far superior to either of the Sturmey hub gears I tried. </p> <p>The shift is so solid and secure-feeling (considering it shifts under load because it does so automatically) that it would make a really nice "workhub" if it only had a user-serviceable shift point. </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=3#post-77189 Fri, 06 Jul 2012 13:57:35 +0000 steveo 77189@http://citycyclingedinburgh.info/bbpress/ <p>That is some serious graphing! Maybe email it to SRAM, might be a good sideline for you.</p> <p>From reading your experiences I get the feeling the hub isn't really designed for "real" work, more the sort of thing you'd stick on a beach cruiser. </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=3#post-77188 Fri, 06 Jul 2012 13:54:11 +0000 Tom 77188@http://citycyclingedinburgh.info/bbpress/ <p>You're spinning out at 23mph and you're getting continual up and down-shifts at normal speeds. </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=3#post-77187 Fri, 06 Jul 2012 13:50:17 +0000 Dave 77187@http://citycyclingedinburgh.info/bbpress/ <p>I did some serious graphing over lunch:</p> <p>Horizontal bars represent cadence, green being "knees don't explode", two pairs of vertical lines denote common speed zones. Each line represents an alternative sprocket size.</p> <p>As you can see, the real hub is not very good at getting a large proportion of your journey into a sensible cadence:</p> <p><img src="http://mccraw.co.uk/upload2/shift10.jpg"></p> <p>Now, imagine if the Automatix shift point was increased to 16mph:</p> <p><img src="http://mccraw.co.uk/upload2/shift16.jpg"></p> <p>What an improvement! (I should be a bike hub designer, honestly.)</p> <p>But you see the problem? </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=2#post-77098 Fri, 06 Jul 2012 00:32:51 +0000 crowriver 77098@http://citycyclingedinburgh.info/bbpress/ <p>Seems the standard SRAM sprocket is a 19T ? Possible to change to a 20T or 21T. Lower gear is direct drive, 1:1. So it i your overall gearing that maybe too high. Either bigger sprocket on hub, or a smaller chainring? </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=2#post-76917 Wed, 04 Jul 2012 17:29:57 +0000 crowriver 76917@http://citycyclingedinburgh.info/bbpress/ <p>That's what I reckon too. Lower the gearing, if possible. What sprocket do you have on there just now? SRAM sprockets are allegedly fairly easy to swap out. </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=2#post-76894 Wed, 04 Jul 2012 14:34:23 +0000 wee folding bike 76894@http://citycyclingedinburgh.info/bbpress/ <p><em>This means that it's never possible to pedal the lower gear at a reasonable cadence</em></p> <p>Could you put on a bigger sprocket? </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=2#post-76884 Wed, 04 Jul 2012 13:48:26 +0000 Dave 76884@http://citycyclingedinburgh.info/bbpress/ <p>Yeah, I'm not sure given my track record with hub gears that I'd want to take this one apart rather than just sell it on. But on the other hand, it does feel much nicer than the S2C.</p> <p>The shift point is at 10.2mph, from a cadence of approximately 60rpm in the low gear to 43rpm in the high. This means that it's never possible to pedal the lower gear at a reasonable cadence. </p> <p>Speeds of 10-15mph are therefore being ridden with a strong feeling of "need to change down!" with the bike feeling more reasonable on either side. Unfortunately that's an extremely common range to be in. </p> <p>Well, it's keeping me fit trying to ride up Leith Walk &gt; 15mph! </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=2#post-76869 Wed, 04 Jul 2012 11:33:27 +0000 crowriver 76869@http://citycyclingedinburgh.info/bbpress/ <p><em>I'd take it apart and footer. I do that with bikes, cars, computers, pretty much anything really.</em></p> <p>In principle, I agree, but it depends on how feasible said footering is. Swapping out components for better/more suitable? No problem. Adding extra bits without damaging original? Again no issues. Potentially breaking something by modifying the original component? Different story... </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=2#post-76865 Wed, 04 Jul 2012 11:17:59 +0000 wee folding bike 76865@http://citycyclingedinburgh.info/bbpress/ <p>Well… if you're just asking me… I'd take it apart and footer. I do that with bikes, cars, computers, pretty much anything really.</p> <p>One of the things I don't like about the Brompton is the back hinge because I can't easily fix it myself. </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=2#post-76862 Wed, 04 Jul 2012 11:01:22 +0000 crowriver 76862@http://citycyclingedinburgh.info/bbpress/ <p><em>it's not working properly anyway so what's the harm in taking it apart?</em></p> <p>Conversely, if you spent 80 quid and the thing works but you don't like how it works, do you then break it to try and improve it and lose the 80 quid? Or do you 'live and learn'?</p> <p>Personally I've bought things over the years that, though they functioned well, were not 'right' for me. Customise or cut losses and sell on? Tough one. </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=2#post-76849 Wed, 04 Jul 2012 10:24:55 +0000 wee folding bike 76849@http://citycyclingedinburgh.info/bbpress/ <p><em>Yes, but I suspect that is not an operation for the faint of heart and no doubt invalidates the warranty.<br /> </em></p> <p>Well I usually take the view that it's not working properly anyway so what's the harm in taking it apart? </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=2#post-76827 Wed, 04 Jul 2012 00:59:26 +0000 crowriver 76827@http://citycyclingedinburgh.info/bbpress/ <p>Yes, but I suspect that is not an operation for the faint of heart and no doubt invalidates the warranty.</p> <p><a href="http://forum.ctc.org.uk/viewtopic.php?f=5&amp;t=62320">This guy stripped the hub down</a> and there's <a href="http://www.bikeforums.net/showthread.php/762155-Moulton-TSR-2-mods-New-SRAM-A2-Automatic/page2">a good discussion here</a> about tweaking the springs. I'd be too scared to knacker the hub... </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=2#post-76822 Tue, 03 Jul 2012 23:13:32 +0000 wee folding bike 76822@http://citycyclingedinburgh.info/bbpress/ <p>Found it:</p> <p><em>This is great because stretching or pushing this little spring makes it easy to optimize the shifting point for your purpose.</em> </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=2#post-76821 Tue, 03 Jul 2012 23:11:25 +0000 wee folding bike 76821@http://citycyclingedinburgh.info/bbpress/ <p>I think this guy</p> <p><a href="http://hubstripping.wordpress.com/fs-torpedo-automatic/" rel="nofollow">http://hubstripping.wordpress.com/fs-torpedo-automatic/</a></p> <p>reckoned that you could tweak the springs a bit but I didn't see that bit on this web page. Perhaps I dreamed it. </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=2#post-76820 Tue, 03 Jul 2012 23:02:52 +0000 Dave 76820@http://citycyclingedinburgh.info/bbpress/ <p>Yep - the core issue is simply that because it changes up at such a low speed, even if you change the sprocket so it is a low 60rpm cadence at 8mph, a rapid 120rpm will then only get 16mph. </p> <p>Or, another way of thinking about it is that the shift happens at a lower speed than I ride up almost any hill on my commute, so it's really just a single speed where your first half a dozen pedal strokes away from a red light are in an easier gear... </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=2#post-76813 Tue, 03 Jul 2012 20:17:06 +0000 crowriver 76813@http://citycyclingedinburgh.info/bbpress/ <p>I would imagine the only thing which might influence the speed at which the gear changes is wheel/tyre diameter. Bigger diameter, bigger circumference, fewer RPM to reach a given speed, hence gear shift would occur at higher speed. Vice versa for smaller diameter.</p> <p>I mentioned gearing (sprocket, chainring) only because you seemed to have an issue with pedalling cadence, particularly uphill. Which might indicate lower overall gearing required? </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=2#post-76811 Tue, 03 Jul 2012 19:50:51 +0000 Uberuce 76811@http://citycyclingedinburgh.info/bbpress/ <p>Oh, you mean rear wheel RPM and not crank RPM? </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=2#post-76810 Tue, 03 Jul 2012 18:56:18 +0000 Dave 76810@http://citycyclingedinburgh.info/bbpress/ <p>The problem is obvious although I didn't fully consider it. The change is based on RPM not cadence, so you can fit any gearing you like and it makes no difference to the speed you're travelling at when the hub shifts.</p> <p>Off out with the cadence meter fitted to see what exactly the shift pattern is. </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=2#post-76801 Tue, 03 Jul 2012 14:16:28 +0000 crowriver 76801@http://citycyclingedinburgh.info/bbpress/ <p><em>Yeah, if you gear it to top out at 24mph@100rpm, at 11.2mph you'll be getting about ~46rpm which seems about what I'm suffering.</em></p> <p>It seems you are fairly speedy urban rider then. Presumably the top speed would be slightly higher on 700c or 27" wheels, and maybe the gear change at a slightly higher speed too? </p> <p>With the start/stop of junctions, traffic lights, speed bumps etc. it is not that frequent that I manage to sustain speeds above 11mph in normal urban riding. When I do get into the 12-18mph range, a higher gear would help. Unless I'm on a downhill, it is rare I get above 18mph in the city. </p> <p>But that's me. I'm guessing you have a style of riding where a gear change at 11.2mph seems inconvenient or breaks the rhythm of your fast cadence.</p> <p>What I've tended to find is that I now change my style of riding depending on which bike I'm riding, so on my hub geared small wheelers I'm a bit more pootley; on the derailleur geared 700c bikes I tend to do a higher cadence faster style of riding; the cargo bike is somewhere inbetween; the tandem is different again as I cannot do higher cadence riding because of the junior stoker: his feet might fly out of the toeclips! </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=2#post-76795 Tue, 03 Jul 2012 13:28:42 +0000 Dave 76795@http://citycyclingedinburgh.info/bbpress/ <p>Yeah, if you gear it to top out at 24mph@100rpm, at 11.2mph you'll be getting about ~46rpm which seems about what I'm suffering.</p> <p>hi ho. </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=2#post-76785 Tue, 03 Jul 2012 11:37:46 +0000 crowriver 76785@http://citycyclingedinburgh.info/bbpress/ <p>On second thoughts it may just be that the way your Automatix is set does not suit your riding style. If you're a sporty fast cadence in low gear type of rider, rather than a pootley city bike cruiser type of rider, it might not be the right set up. I see on other fora that "shifting early" comes up quite a lot in discussion of the Automatix. </p> http://citycyclingedinburgh.info/bbpress/topic.php?id=7042&page=2#post-76782 Tue, 03 Jul 2012 11:21:32 +0000 crowriver 76782@http://citycyclingedinburgh.info/bbpress/ <p><em>Speed chosen to change gear is far, far too low. You get going and then it immediately changes up, so you've got to crank out 40rpm uphill unless you go *really* slowly.</p> <p>Will see if it beds in, but not a fan of automatic shifting unless the cadence is vaguely sensible!</em></p> <p>Is that not adjustable? I thought you could change (within limits) the speed at which the gear change takes effect?</p> <p>Hmmm. Maybe not. </p> <p>"The shifting points can be preset by SRAM according to the guidelines of the bicycle manufacturer at certain speed limits which can be 12, 14 or 18 km/h (7.5, 8.7 or 11.2 mph). The nickle-chrome plated internal gear hub weighs 980g and comes with a coaster brake. For different sprocket sizes: 15, 16, 17, 18, 19, 20, and 21-tooth-sprockets"</p> <p><a href="http://www.sram.com/sram/urban/products/automatix" rel="nofollow">http://www.sram.com/sram/urban/products/automatix</a></p> <p>Are you running 26" wheels? This may account for the gearing feeling low as the hub may be adjusted for 28"/700c. Change the sprocket to something smaller? </p>