Search found 725 matches

by rfryer
25 Apr 2013, 12:29pm
Forum: Bikes & Bits – Technical section
Topic: slowing down on hills - some 'O' level physics
Replies: 70
Views: 2835

Re: slowing down on hills - some 'O' level physics

Ayesha wrote:To ride up a cone, and freewheel down the other side, requires the same energy as riding round half its base circumference, if the angle is 4%.

Less steep, more efficient to ride up and over. More steep, more efficient to ride round. :wink:

Interesting. Though it's presumably speed-dependent - if you go slowly enough around the cone for the air resistance to tend towards zero, the limiting angle will be much smaller. Similarly, if you are at a higher altitude with less air density. :P
by rfryer
25 Apr 2013, 11:44am
Forum: Bikes & Bits – Technical section
Topic: eliptical chainring - want to try one?
Replies: 61
Views: 8696

Re: eliptical chainring - want to try one?

To me, "nice circles" mean that you are spinning with (what feels like) a continual forward pressure on each crank, and with smooth variations in that pressure.

I've been using Rotor Q-rings on my road bike for the last year or so. I found the most noticeable difference to the pedalling action is when climbing out of the saddle. It feels more powerful and less jerky, presumably because I'm spending less time struggling through tdc. Put another way, rather than "landing hard" on the bottom of each pedal stroke, it feels as though I'm smoothly transitioning into the next. I've also found that my endurance has improved, though it's hard to isolate that from other causes (more training, different bike).
by rfryer
24 Apr 2013, 11:42am
Forum: Bikes & Bits – Technical section
Topic: Shimano Alfine 11 - Longer term reliability
Replies: 830
Views: 175588

Re: Shimano Alfine 11 - Longer term reliability

There's been a lot of talk about deviation from Shimano's suggested input ratio of 1.9 having the potential to cause problems, presumably because running a lower ratio allows the rider to put more torque through the hub. But then manufacturers are freely building bikes with lower ratios than that, or putting them into tandems where the potential for high torque is magnified. I suspect it's all a bit of a red herring.

I do wonder, though, if running the hub with the shifter slightly out of adjustment can cause gradual damage before actually exhibiting any problems (by which time it's too late). My experience is that the yellow marks were perfectly aligned from new, but that I've had to tweak the cable adjustment quite a few times to keep it that way, despite having had no feedback (other than the yellow marks) to indicate that it was going out of adjustment. I now try to check that the marks are aligned every time I ride.

How diligent are other users about checking cable adjustment, especially those that have had problems?
by rfryer
22 Apr 2013, 7:49am
Forum: Bikes & Bits – Technical section
Topic: Tyre pressures.....
Replies: 39
Views: 1963

Re: Tyre pressures.....

Thanks to Reohn2 for starting this thread, and posting the link to Cycling Quarterly. As a consequence, I increased my tyre width (from 23 to 25) and dropped the pressures (from 110 to 70/95) on my road bike.

I rode a sportive on this setup yesterday, and the ride was significantly smoother, and I found it much less fatiguing. Also, although conditions meant that my average speed was poor, my position in the results table was at least as good as I hoped for. And no punctures!

It works!
by rfryer
20 Apr 2013, 9:01am
Forum: Bikes & Bits – Technical section
Topic: bike positioning help please
Replies: 93
Views: 177456

Re: bike positioning help please

If you're pushing back onto the saddle, you might consider lifting the nose at the same time as moving the saddle back?
by rfryer
17 Apr 2013, 8:11am
Forum: Bikes & Bits – Technical section
Topic: Shimano Alfine 11 - Longer term reliability
Replies: 830
Views: 175588

Re: Shimano Alfine 11 - Longer term reliability

Meshuga wrote:@rfryer: looks like the genesis cable end bolt is from an alfine 8. the 8 shifts to a higher gear as the cable tightens, and the cable wraps clockwise around the cassette joint. The 11 shifts to a lower gear as the cable tightens and wraps anticlockwise around the cassette joint. Hence the bolts are drilled to produce a mirror image. Very curious that they should provide you with the wrong one.

In both systems the cable end bolt should be affixed to the cassette joint with the nut facing outwards. with this genesis one are they asking you to fix the nut facing inwards perhaps? I didn't think this was possible but it would be a suitable bodge.


Genesis did supply the Nexus part on the Alfine 11 with the bolt facing outwards. It fits, but removal without pliers is tricky as you can't use the standing part of the cable to rotate it.
by rfryer
16 Apr 2013, 10:24am
Forum: Bikes & Bits – Technical section
Topic: Double Chainring & low Gearing
Replies: 36
Views: 3519

Re: Double Chainring & low Gearing

reohn2 wrote:
I'm very happy that you (reohn2) get on with triples so well. My experience with Ultegra has been less rosy. It worked OK initially, but then I replaced the inner and middle chainrings to lower the gearing, and thereafter the shifting was much less clean, to the extent that I was adjusting the cable to choose whether I wanted reliable access to the inner two or outer two chainrings. And, despite what you might think, I'm reasonably competent at setting up bikes.

Chainring sizes?

I dropped the inner from, I think, 30 to 26, the smallest compatible with the BCD. I then replaced the middle after an incedent with loose chainset bolts caused it to bend :oops: I think it was after this that the shifting got more problematical, and I don't know if it was related to a differently ramped chainring, different tooth count (I don't remember the details) or because I mislaid the shim washers that were used on the original. Anyway, I came away with the impression that triples were much fiddlier to set up correctly than doubles.

reohn2 wrote:
I'm surprised that you can't accept that a double setup might not be as reliable as a triple - that's the opposite of my experience,

But that's not what I said.

You did say, of triples,
reohn2 wrote: I can't think of a more reliable drivetrain...

...which I took to include doubles. OK, technically, you were just saying that triples were no less reliable than doubles.
reohn2 wrote:
and counter-intuitive given the reduced complexity

It isn't more complex,it's just one more chainring.

...plus a three-way STI shifter, with tighter tolerances due to the need to reliably select the middle chainring while shifting in both directions.

reohn2 wrote:
My comment about gear selection is very much a personal one. I find that on a double there is far less call to switch chainrings, and I like that. Simultaneous front/rear shifts are far less straightforward and predictable than rear-only shifts, and I found myself doing a lot more of them on a triple setup.

So what's to stop you having the same outer rings on the triple and a inner ring of choice for the real hilly stuff or when you've just bonked and around the next bend you're looking at a 20%
hill,which is just one of many scenarios where a triple will pull or rather push you out of the mire so to speak.

I think that's pretty much what I used to have. However, my perception (and I could be wrong here) is that the cage on a triple front dérailleur is narrower than on a double in order to hit that middle ring accurately, and that therefore the ability to cross-chain is reduced, forcing more front-shifts. I'm pretty sure my middle ring used to dislike the rear dérailleur being at either extreme, meaning that you can't strictly use it as a double with a bail-out clause. But I could be talking tosh :mrgreen:

One other down-side of triples I forgot to mention earlier is the increased Q-factor, which I would assume is more relevant to some than others. Personally, I can't say I noticed a lot of difference!

I'm definitely not anti-triple; there's no arguing with the wider gear range without the wide inter-gear spacing. Hopefully, at some point, I'll get to ride an electronically-shifting triple that eliminates most of what I see as the downsides.
by rfryer
16 Apr 2013, 8:02am
Forum: Bikes & Bits – Technical section
Topic: Double Chainring & low Gearing
Replies: 36
Views: 3519

Re: Double Chainring & low Gearing

No, I've not ridden the classic French cols on a double. I have ridden classic UK climbs, up to 1 in 3 gradient, on both a triple and a compact double with WiFli.

Maybe there's a disconnect, in that by "double" you think I mean a traditional road racing double, which is invariably geared very high. In fact, I mean any system with two front chainrings, and you can get some very small ones if you're prepared to sacrifice some of the top end in order to be able to climb the steeps.

Anyway, I'm starting to feel this has been discussed (or, rather, argued) to death. Expressions like "The best system by far is..." don't really get us very far. I think all systems have pros and cons, and am very interested in discussing them and deciding which suits me best for a given ride. That's why I had had a triple until it was stolen a few weeks ago, and currently own a normal compact double, a WiFli compact double, an Alfine 11 and a fixed gear. I'd also hope to try Rohloff and NuVinci hubs at some point, as well as electronic shifting. There are so many options out there - it's great!

All the best!
by rfryer
15 Apr 2013, 11:57pm
Forum: Bikes & Bits – Technical section
Topic: Double Chainring & low Gearing
Replies: 36
Views: 3519

Re: Double Chainring & low Gearing

Without wishing to flog a dead horse... :D

I'm very happy that you (reohn2) get on with triples so well. My experience with Ultegra has been less rosy. It worked OK initially, but then I replaced the inner and middle chainrings to lower the gearing, and thereafter the shifting was much less clean, to the extent that I was adjusting the cable to choose whether I wanted reliable access to the inner two or outer two chainrings. And, despite what you might think, I'm reasonably competent at setting up bikes.

In contrast, my double setup has been very reliable, and wasn't at all phased when I swapped in ovalised chainrings.

I'm surprised that you can't accept that a double setup might not be as reliable as a triple - that's the opposite of my experience, and counter-intuitive given the reduced complexity. In fact, I'm even finding my Alfine 11 to be more reliable and nicer to use than a triple, but it's early days there! I do like the fact that on an IGH you can lower the gearing of the entire bike by swapping in a single, low-cost sprocket.

My comment about gear selection is very much a personal one. I find that on a double there is far less call to switch chainrings, and I like that. Simultaneous front/rear shifts are far less straightforward and predictable than rear-only shifts, and I found myself doing a lot more of them on a triple setup.

As I said before, it's all a matter of preference. I prefer the shifting style of a double, I'm flexible enough with my cadence to tolerate wide gear spacings, and if I need it I'm more than happy to sacrifice some top-end gearing to have the bottom-end that I need.

But I fully accept that they are not tradeoffs that you'd be happy with. That's why both doubles and triples are available, and it's worth openly discussing the differences to help people who might be considering either option.
by rfryer
15 Apr 2013, 11:28am
Forum: Bikes & Bits – Technical section
Topic: Double Chainring & low Gearing
Replies: 36
Views: 3519

Re: Double Chainring & low Gearing

reohn2 wrote:There must be something wrong with you're set up.
I've been riding triples on solos and tandems for 20years,6,7,8 and 9sp with d/tube,b/ends/kelly's/MTB and road STI's without any issues.yes I've had the odd problem,mainly overshooting the granny ring,which has been cured with an N-gear Jumpstop.
The triples on five bikes(two tandems and one solo 9sp with STI's and two solos with 8sp on Kelly's-friction front,indexed rear-) are 100% reliable

I'm sure they can be made to work, though I'd be more confident using them with a friction shifter on the front. If they're indexed, chain ring position becomes extremely critical, sometimes needing shim washers to get the teeth into exactly the right place.

reohn2 wrote:As for Di2,toys for rich boys/girls IMO.

I've not used Di2 personally, but given that the two main benefits seem to be trimming the front derraileur to match the rear, and performing extremely slick front shifts, I'd say that triples were an ideal application. They could even be extended to select the incrementally "next" gear intelligently, switching chainrings where necessary. Or you could run a short-cage rear derraileur with a wide-range chainset, and prevent shifts into untenable gears.

I agree it's an expensive technology, but given the amount people are spending on bikes these days, I don't think it's all that outrageous.

reohn2 wrote:How close does it (SRAM WiFli) get to 24t front x 34t rear?

Clearly, not very. But it gets pretty close to the 30t front x 28t rear that was the best triple that Shimano Ultegra could offer until this year.

In my view, the main advantage of the triple chainset in comparison to a double is a (potentially) wider gear range, while keeping narrow inter-gear spacings. The downsides are higher cost, more weight, trickier adjustment and less straightforward gear selection. Neither's better in all cases - it depends on your priorities and style of cycling.
by rfryer
15 Apr 2013, 10:11am
Forum: Bikes & Bits – Technical section
Topic: Double Chainring & low Gearing
Replies: 36
Views: 3519

Re: Double Chainring & low Gearing

I've nowhere near the touring experience of Gearoidmuar, but I've cycled a lot of hills and passes, mainly in the UK but some abroad too.

My experience of triple chainsets has been sketchy - I've found them a pain to get shifting smoothly and reliably. I'm hoping to be convinced otherwise when Shimano comes out with a Di2 triple.

In the meantime, I'm quite happy with SRAM's Wifli concept - a compact double with a 32 tooth sprocket. That's pretty close to the bottom gear you get on most road triples. Of course, having such a wide range on a double chainset means the gears are fairly widely spaced, but I'm happy with that compromise.
by rfryer
12 Apr 2013, 3:23pm
Forum: Bikes & Bits – Technical section
Topic: Shimano Alfine 11 - Longer term reliability
Replies: 830
Views: 175588

Re: Shimano Alfine 11 - Longer term reliability

The "top hat" cable stop doesn't provide any waterproofing - it's in no way a tight fit. The Shimano part is soft rubber, and seals tightly against the ferrule. The main exposure to leakage seems to be the hole where the cable exits the bellows, and my hope is that it's a pretty small exposure; the hole's pretty tight, and there's a fair chance that any water that did get would get caught up in the bellows rather than getting into the cable. I'm certainly more comfortable using the standard Shimano parts rather than those supplied by Genesis.
by rfryer
12 Apr 2013, 11:40am
Forum: Bikes & Bits – Technical section
Topic: Chainset for mountain-climbing
Replies: 12
Views: 895

Re: Chainset for mountain-climbing

Valbrona wrote:And there aren't any mountain roads in the UK. Just hills.


I did try not to bite, honest I did!

It all depends on how you define mountain roads, I suppose. True you won't find any sustained 1000m climbs in the UK . But you'll find some decent sustained ascents (such as the Bealach na Ba at 626m) and some climbs which are ridiculously steep compared to most continental roads (eg Hardknott Pass at 1 in 3).

I'd argue that cyclists in hilly parts of the UK have at least as much need of low gearing as those on the continent.
by rfryer
12 Apr 2013, 11:27am
Forum: Bikes & Bits – Technical section
Topic: Double Chainring & low Gearing
Replies: 36
Views: 3519

Re: Double Chainring & low Gearing

I once bodged a road bike for a particularly hilly sportive. It has an Ultegra compact double setup on it. I just replaced the double chainset with a road triple. I couldn't get hold of any spacer washers, so I just slapped a second middle chainring on the outside, and had a 26-tooth granny ring.

I had to adjust the front dérailleur a bit, but I don't recall any major issues.
by rfryer
11 Apr 2013, 5:36pm
Forum: Bikes & Bits – Technical section
Topic: Shimano Alfine 11 - Longer term reliability
Replies: 830
Views: 175588

Re: Shimano Alfine 11 - Longer term reliability

For those who haven't been following carefully(!) I've recently bought a Genesis Day One Alfine 11, and was a little surprised to find that the parts around the end of the cable were nothing like those in the Shimano documentation. So, I decided to try buying and fitting the correct parts...

I bought the parts from Petra Cycles for just over £15 including shipping.

First up, the cable stop (aka CJS700 inner cable fixing bolt unit in cble fix, part number Y6TV98070). The following photo shows the Shimano and Genesis offerings together. As you can see from the needles pushed through the cable holes, the Genesis has the hole drilled through the wrong diagonal, making it a complete pain to fit and remove. The Shimano one is much better.

Image

Secondly, the cable housing (aka SLS700 outer casing holder unit case, part number Y6TV98060). As you can see from the photo below, Genesis simply supply a cable stop to fit into the cassette arm, rather than the full rubber bellows assembly. It was a bit of a faff to fit the Shimano part, partly due to difficulty threading the cable through the end of the bellows, and partly because the new housing requires a greater length of cable between the ferrule and the fixing bolt. However, there was sufficient cable (just) and once fitted it all looks good, though in top gear the end of the bellows is very close to getting dragged into the cable track round the cassette. I tried crimping the end of the bellows to the cable (there is a metal ring included, you can see it at the tip of the bellows) but can't get it sufficiently tight that the cable won't pull through.

Image