Yet Another Cycling Forum
General Category => Freewheeling => Velo Fixe => Topic started by: Revellinho on 07 May, 2016, 02:55:40 pm
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Any thoughts on these? The bike in question is a Genesis Flyer 2015
I can't get the rear wheel out without deflating the tyres - is that normal?
I put a 15T cog on and because the wheel has to go further back than normal, the brakes are too close to the tyre wall for my liking. Is it just a case of getting slimmer brake blocks? When I first tried it I detected the brake rubbing on the tyre so I released the tension on the rear brake and did not use it.
The chain tension is a bit slack when the chainwheel is in one particular place (pedal horizontal and pointing back, but NOT pedal horizontal and pointing forward) - I don't think it is dangerously so, but I don't want to find out the hard way. It moves at least 1cm, but is pretty much as tight as I would want elsewhere without binding in any way. Is that normal or do I need a chain ring that is more like a circle shape?
I'm assuming you can treat the freewheel side just like another cog - remove it (have not got the tool though) and put a cog/lockring on. (I have a 15T and a 16T and it would be more convenient to have them either side.)
I greased the 16T cog when I put it on, but still had to whack the chain whip with a hammer to remove it. Is that normal or is there some magic grease that they haven't told me about?
How can you tell the difference between 3/32 and 1/8 just by looking?
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Any thoughts on these? The bike in question is a Genesis Flyer 2015
I can't get the rear wheel out without deflating the tyres - is that normal?
Eh? Are the tyres catching on the brakes, the mudguards or something else? If it's the mudguard, set it up with a bit more clearance at the back, or else get some of those plastic QR stay attachments.
I put a 15T cog on and because the wheel has to go further back than normal, the brakes are too close to the tyre wall for my liking. Is it just a case of getting slimmer brake blocks? When I first tried it I detected the brake rubbing on the tyre so I released the tension on the rear brake and did not use it.
Surely you can alter the position of the brake shoes in the calipers?
The chain tension is a bit slack when the chainwheel is in one particular place (pedal horizontal and pointing back, but NOT pedal horizontal and pointing forward) - I don't think it is dangerously so, but I don't want to find out the hard way. It moves at least 1cm, but is pretty much as tight as I would want elsewhere without binding in any way. Is that normal or do I need a chain ring that is more like a circle shape?
Wait, are you running with an oval chainring? Yes, I'd definitely get a circular chainring.
I'm assuming you can treat the freewheel side just like another cog - remove it (have not got the tool though) and put a cog/lockring on. (I have a 15T and a 16T and it would be more convenient to have them either side.)
Yes you can do this.
I greased the 16T cog when I put it on, but still had to whack the chain whip with a hammer to remove it. Is that normal or is there some magic grease that they haven't told me about?
Rotafix (https://www.youtube.com/watch?v=5qIVEpyelP0)
How can you tell the difference between 3/32 and 1/8 just by looking?
One's fatter than the other!
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The chain tightening as you pedal is often due to the chainring not being exactly right on the spider. Slacken the chainring bolts off very slightly, turn to position that makes the chain tight and squeeze the chain together above below the chainstay. This will move the chainring a tad. Tighten up the bolts and check.
Not being able to get wheel out without deflating tyre is nothing to do with being a fixie, it is just because of the proportions of your dropouts/wheelsize/tyre. I guess it isn't able to get past the bridge at the chainstays.
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Some brake blocks are taller than some rim braking surfaces, then yes you need slimmer blocks if you can't/don't want to lower them.
Filing a bit off the slots can provide some more drop, though it'd be unusual to need that with the brakes supplied with a bike.
Braking and safetywise, you don't need more than a very small amount of clearance between block and tyre, just as long as you account for any difference as the blocks wear down.
Quick release brakes should help with wheel changing, otherwise it's not uncommon to have to deflate the tyre.
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Nothing wrong with a bit of slack in the chain (despite the stupid comments from some on here). It doesn't really matter if the tension varies a bit as your turn the pedals.
Depends on how you are measuring the tension - at least 1cm where? If that's in the middle of the chain, then a few cm movement up or down is fine. Try using a screwdriver or similar to push the chain off as you turn the pedals, you will find there's not much chance of it actually derailing.
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Tyre: when the brake cable tension is released with a small lever/cam it only seems to slacken it off a fraction and the tyre is too fat to get past the brake blocks. Just have to live with that one till I wear the tyres out. On my touring brakes it is never an issue, because you just pop the stopper at the end of the brake cable out and the brakes open completely.
Block position: They're just as low as they can go now, but as the wheel goes back to take up the slack caused by using the 15T cog, the blocks threaten to touch the tyre. Slimmer blocks I guess. I suppose if I was not ever going to use the 18T supplied with the bike a link might be able to be removed. Would the difference between 18T and 15T allow that I wonder?
Chainring: bolts sound worth investigating, it's definitely just the one 'hotspot'. In fact, I checked the bolts to make sure they were properly nipped up and was very surprised to find that they were not. I suppose they must have worked loose after the bike had been assembled and then ridden for a bit. I only used a multi-tool, so not much torque was used.
Whacking with hammer: I used the grease I had for putting on new pedals - the one they sell in Decathlon. Interesting video!
Slack: I was going from the middle of the top chain run (middle being between the cog and chain ring). Sounds like it is taut enough, but thanks for the derail tip.
I think I am much more safety concerned with this bike than others I ride, because I feel right on the edge of control when riding it fast down hills.
Thanks very much for the time you spent making comments.
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I'm assuming you can treat the freewheel side just like another cog - remove it (have not got the tool though) and put a cog/lockring on.
You can put a cog on, but you probably won't be able to fit a lockring if it's a flip flop hub. I have that setup on my Flyer: 18t cog on the fixed side (with lockring) and 19t cog on the freewheel side (without lockring). I haven't had any problems not using the lockring, but I have two brakes and try to avoid skids!
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Forward-facing dropouts are sometimes tricky for wheel removal but rear-facing dropouts with mudguards are the really annoying combination. You either have to leave a lot of space between tyre and mudguards when fitting them, or be prepared to undo the mudguards every time you need to fix a puncture.
If they are dual-pivot brakes, perfectionists will set the blocks at different heights on either side when new. One block travels upwards as it wears and the other travels downwards because of the geometry of the brake.
Incidentally, you don't need a rear brake on a fixie so you can just remove it if the problem seems insoluble. Do pay extra attention to front brake maintenance, though, as stopping by resisting the pedals is not hugely effective.
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Block position: They're just as low as they can go now, but as the wheel goes back to take up the slack caused by using the 15T cog, the blocks threaten to touch the tyre. Slimmer blocks I guess. I suppose if I was not ever going to use the 18T supplied with the bike a link might be able to be removed. Would the difference between 18T and 15T allow that I wonder?
Yes, you can certainly remove a link or two of chain.
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Nothing wrong with a bit of slack in the chain (despite the stupid comments from some on here). It doesn't really matter if the tension varies a bit as your turn the pedals.
Depends on how you are measuring the tension - at least 1cm where? If that's in the middle of the chain, then a few cm movement up or down is fine. Try using a screwdriver or similar to push the chain off as you turn the pedals, you will find there's not much chance of it actually derailing.
Have you experienced derailing with a fixed gear? It's only happened to me once at no more than 160 rpm. AFAIK it rarely happens at low cadence, when the consequences would be less serious. I agree that the stock advice about slack is close to meaningless. OTOH I can easily push my chain off the chainring (with fingers :o ) even when it's so tight that it binds at the tightest spot on the chainring. I suspect that is not a sound test.
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I suppose if I was not ever going to use the 18T supplied with the bike a link might be able to be removed. Would the difference between 18T and 15T allow that I wonder?
A quick Google search reveals that the 2015 Flyer reviewed here (http://road.cc/content/review/144906-genesis-flyer-singlespeed) has track ends (rear facing & not drop-outs). That means brakes get closer to the tyre as the rear axle moves back. So a smaller sprocket (or chainring) may cause brake problems, as you found.
Shortening the chain is a pragmatic solution. Removing a whole link (i.e. one inch) would match a reduction from 18T to 14T (not exact, but close enough). I suggest inverting the bike, loosening the rear nuts/bolts/QR & seeing whether you can move the axle far enough forward to fold the chain a whole link shorter.
There is more than one way of shortening a chain. You could use a half link (i.e. half an inch) if a whole link was too much. Joining links (re-usable ones like SRAM & KMC) allow you to take a bit of chain out & replace if you need to.
Chainring: bolts sound worth investigating, it's definitely just the one 'hotspot'. In fact, I checked the bolts to make sure they were properly nipped up and was very surprised to find that they were not. I suppose they must have worked loose after the bike had been assembled and then ridden for a bit. I only used a multi-tool, so not much torque was used.
As ever, Sheldon Brown (http://sheldonbrown.com/fixed.html) offers good advice
Slack: I was going from the middle of the top chain run (middle being between the cog and chain ring). Sounds like it is taut enough, but thanks for the derail tip.
My approach (not original) is to tighten as far as possible without the chain binding. That usually means overdoing it & then sliding the axle forwards just enough that the the chain doesn't bind at the "high spot" of the chainring.
I re-tension when the chain slack is enough that I can feel it when going from propulsion to leg-braking at low cadence (Andy Gates, formerly OTP called it flibble)
I think I am much more safety concerned with this bike than others I ride, because I feel right on the edge of control when riding it fast down hills.
Agreed. It takes time/practice to build confidence in your ability to control fast descents. A good back brake is important if you feel you're losing the battle. It's a learning process. You need to find your own way of coping with legs whirling at a silly rate.
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It isn't always practical to change this (once you have a bike), but if you can, go for the biggest front ring and largest rear sprocket possible. The chain is more secure, there is less wear on each tooth and things will run more smoothly (IME).
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It isn't always practical to change this (once you have a bike), but if you can, go for the biggest front ring and largest rear sprocket possible. The chain is more secure, there is less wear on each tooth and things will run more smoothly (IME).
there is a weight penalty, but i agree regarding smoothness, hence a 60t 'ring is waiting when the current chain is worn out ;)
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52 x 20 is a nice combination that doesn't look too weird. As always with a fixie, ensure that chainring teeth/sprocket teeth is not a whole number, and preferably an irregular fraction or at least not ending in .5 or .33. 52/20 = 2.6 which means the sprocket gets hammered at five 72 degree intervals around its circumference, which is as near-as-dammit even wear with the amount of chain wrap on a 20T. 48/16 is the worst possible as the sprocket will always wear in the same place with each "power stroke".
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Forward-facing dropouts are sometimes tricky for wheel removal but rear-facing dropouts with mudguards are the really annoying combination. You either have to leave a lot of space between tyre and mudguards when fitting them, or be prepared to undo the mudguards every time you need to fix a puncture.
If they are dual-pivot brakes, perfectionists will set the blocks at different heights on either side when new. One block travels upwards as it wears and the other travels downwards because of the geometry of the brake.
Incidentally, you don't need a rear brake on a fixie so you can just remove it if the problem seems insoluble. Do pay extra attention to front brake maintenance, though, as stopping by resisting the pedals is not hugely effective.
I have a 2015 genesis flyer, I use Secu Clips on the rear mudguard as I have for most of the fixed bikes I've owned, this means I can just unclip the mudguard to aid getting the wheel out. On my Flyer the rear brake has a reach that is a bit too short, which means the rear wheel can't be to far back in the track end, if a cog size change brings the wheel too far back just adjust the chain length to compensate, there are half links available if needed. Its common to have loose and tight spots in fixed wheel chains, some caused by cogs and chainrings not being round or the chainring not sitting right on the spider or uneven wear on the chain, just set the chain tension at one of the tight spots. My flier is my winter bike and often used in slippery conditions so I like to keep the back brake on it, it means I can leave the front brake alone when its slippery.
https://www.sjscycles.co.uk/mudguards/sks-secu-clip-for-front-mudguard-stay-34-mm-each/
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Most out-of-roundness is usually in the chainring rather than the sprocket and can be minimised by loosening the bolts holding the chainring to the spider and giving it a judicious tap rearwards with the chain at its tightest point, before checking again and re-tightening the bolts. The ultimate solution is Really Expensive chainrings, which tend to be the roundest.
You shouldn't be able to push the chain off the chainring. If you can, it is either too slack or it has become worn out.
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I beg to differ about pushing the chain off the chairing - see my earlier post. However, my experience is with 3/32" transmission. The chainring teeth are full width (give or take a bit of wear ;)), but the chains I use now are 8-speed bushingless components designed for derailleurs. It may be different with a bushed chain &/or 1/8" width.
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I beg to differ about pushing the chain off the chairing - see my earlier post. However, my experience is with 3/32" transmission. The chainring teeth are full width (give or take a bit of wear ;)), but the chains I use now are 8-speed bushingless components designed for derailleurs. It may be different with a bushed chain &/or 1/8" width.
I've always used 1/8th chains, never had one I can just push of the chainring, I normally have to slacken the chain to remove to chain from the chainring, if I had one that I could just push of I'd be worried about having the chain jump of whilst riding.
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52 x 20 is a nice combination that doesn't look too weird. As always with a fixie, ensure that chainring teeth/sprocket teeth is not a whole number, and preferably an irregular fraction or at least not ending in .5 or .33. 52/20 = 2.6 which means the sprocket gets hammered at five 72 degree intervals around its circumference, which is as near-as-dammit even wear with the amount of chain wrap on a 20T. 48/16 is the worst possible as the sprocket will always wear in the same place with each "power stroke".
SHIT! You know your...
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Most out-of-roundness is usually in the chainring rather than the sprocket and can be minimised by loosening the bolts holding the chainring to the spider and giving it a judicious tap rearwards with the chain at its tightest point, before checking again and re-tightening the bolts. The ultimate solution is Really Expensive chainrings, which tend to be the roundest.
You shouldn't be able to push the chain off the chainring. If you can, it is either too slack or it has become worn out.
...stuff!
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I beg to differ about pushing the chain off the chairing - see my earlier post. However, my experience is with 3/32" transmission. The chainring teeth are full width (give or take a bit of wear ;)), but the chains I use now are 8-speed bushingless components designed for derailleurs. It may be different with a bushed chain &/or 1/8" width.
I've always used 1/8th chains, never had one I can just push of the chainring, I normally have to slacken the chain to remove to chain from the chainring, if I had one that I could just push of I'd be worried about having the chain jump of whilst riding.
Are your chains bushed or bushingless?
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FWIW, I've used both and neither could be pushed off the shainring. Bushingless chains are a lot more tolerant of 1-2mm misalignment than full-bushing ones, which can be rather crackly. I've never objectively measured the comparative longevity of bushingless vs. full-bushing.
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FWIW, I've used both and neither could be pushed off the shainring. Bushingless chains are a lot more tolerant of 1-2mm misalignment than full-bushing ones, which can be rather crackly. I've never objectively measured the comparative longevity of bushingless vs. full-bushing.
I presume that they were both/all 1/8".
I haven't used a bushed chain for more than a couple of decades, so don't know the effect of the greater lateral stiffness, Perversely I happen to have a new bushed 3/32" chain in the spares box (A long story to do with Youngest Daughter's hub-geared bike, which needed a biggest sprocket). However, it waits its turn in the maintenance schedule. I'm not keen to experiment for the sake of a ROT that is popular, but unambiguously invalid for me. I prefer to try to prove positive results.
Nevertheless, I still seek an explanation why the ROT works for others, but is utter fairytale stuff for my bike. It's hard to believe that the difference is simply due to a 25% reduction in (internal) chain width.
Does anyone have any ideas, or even extra facts?
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<...> 48/16 is the worst possible as the sprocket will always wear in the same place with each "power stroke".
ignoring your opinion just got the 16t sprocket for the 48x16 setup :).
the thing is, cyclist delivers the power smoothly from say 2 to 6 o'clock position. during that one third of crank revolution the sprocket turns the whole turn with almost even tension/pressure to all it's teeth resulting even wear. while it's a bad combination for doing skids (is it still a "thing" with fixie riders?..), it's perfectly fine for normal riding, just as any other suitable ratio.
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<...> 48/16 is the worst possible as the sprocket will always wear in the same place with each "power stroke".
ignoring your opinion just got the 16t sprocket for the 48x16 setup :).
the thing is, cyclist delivers the power smoothly from say 2 to 6 o'clock position. during that one third of crank revolution the sprocket turns the whole turn with almost even tension/pressure to all it's teeth resulting even wear. while it's a bad combination for doing skids (is it still a "thing" with fixie riders?..), it's perfectly fine for normal riding, just as any other suitable ratio.
It's not just about skid-stops though. When climbing, it's going to be pretty hard to maintain as smooth a power stroke as that, particularly on a tall gear. I know from personal experience I used to wear tyres in patches, sometimes quite alarmingly, when I ran a 42 chainring and haven't had the problem now I use 43. And I've never managed to do a skid stop.
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SO 46-16 is a decent shout for general road riding?
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depends on where you ride, how fast, how hilly and how stop/start. plus your riding style.
I'd regard that as far too high - time triallers used to use a 72" as a standard and 46x16 is 77"
When I rode fixed as my sole machine I rode on 64" on the advice of old club riders, but then I lived in a hilly area.
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As above - learning to ride fixed back in 1969 we would use 48x18 which is 72" on 27" wheels. Once we could pedal we would gear down to 48x20 which is 65". For time trialling on tubs (i.e. 700C) I would use 48x16 which is only marginally bigger than that which you are considering for general use. I still prefer 48x20 (now on 700C) for general use but I have always lived in moderately hilly areas. I know the modern trend seems to be to ride higher gears, but as far as I can tell that is for hipsters in flat cities, not people who actually go somewhere.
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Got 48-16 on now which is fine for (a fairly hilly) city and a bit further tbh. Thinking 75 would be fine for longer days in the saddle (up to 200).
Surprised by TT comments as everyone I know who has tested on fixed goes for something in the region of 86-91
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72" was specified for 'medium gear' events.
I've nearly always ridden 67.5" (43x17), though I sometimes go down to 43x18 these days. I manage to keep up.
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I rode 48-16 summer and 48-17 in winter.
In East Anglia. That's the important thing.
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46/16 would be too high for me too - I prefer 43/17 (or 18 in winter). But if you're happy riding it then crack on.
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46x19 is fine for 60ish mile rides in slightly bumpy Midlands. I'm commuting on 46x17 ATM, hilly but on that gear 10 min tops. Not sure how far I'd get on it audaxing.
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FWIW I have now finished my first proper year with the Flyer, so thank you to those who have contributed to this thread. I rode 46/16 most of the time, which is 77" and managed to get round The Lincoln (400km) audax and the Mersey Rds 24 using that gear, plus a load of short TTs, a discipline I had never tried before. I've just about managed to adjust the brakes enough to get the 15T cog on the back but it's a bit close for comfort and I'll probably move to having two chains of different length, so I can still use the 18T freewheel for pootling around on holiday etc.
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First positive result...
I've replaced the old chain with the bushed one - two changes. I've replaced the chainring with an unused one. That's another change The 20t cog at the rear has been renewed as well, but I would be very surprised if that affected the "pushing off the chainring" test of excess slack.
I can't push the chain off the chainring (with fingers) with the new components & a carefully chosen chain tension/slack. I've checked the old chainring and it's thickness is only around 200 micrometres less than new.
I'll wait and see whether the R.O.T. works for this setup.
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Correction to previous post... The chain is not bushed. It's a KMC Z-610RB, which is 3/32" and only intended for "single-speed" use (possibly for competition BMXs). LBS advises that it doesn't work with derailleurs. It's much stiffer laterally than any other 3/32" chain I've encountered in the last 6 decades. Presumably the clearance between the outer & inner sideplates has been reduced to minimise de-railling problems.
By a strange coincidence, LBS has a few old (unused) Reynolds 3/32" bushed chains, which are flexible & clearly intended for use with the traditional 2x5 derailleur gearing of the 1950s, 1960s & 1970s.
On reflection I'll leave the "push the chain off" R.O.T. in the category of "urban myth until proven otherwise by careful experiment". Ymmv.
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I'm assuming you can treat the freewheel side just like another cog - remove it (have not got the tool though) and put a cog/lockring on.
You can put a cog on, but you probably won't be able to fit a lockring if it's a flip flop hub.
A fixed hub has two threads - a right-hand thread for the sprocket, and a slightly smaller left-hand thread for the lock-ring. On the freewheel side, you'll just have the single right-hand thread. This is the reason that you cannot fit the lock-ring.
I think I have read that you can use a spare lock-ring from a traditional ball-and-cup bottom bracket, as they have the same right-hand thread as do sprockets? Is that right? It's not quite as satisfactory because the sprocket and ring can slip together - but, there again, some riders don't bother with a lock-ring anyway.