Which Single Speed Ratio for the Hills?

buddha

I'm currently running a 48/22 ratio on my pompino.
However I struggle on some of the steeper Surrey and Kent hills. Even when I swap the fixed wheel for my 5-speed hub gear(which gives a 0.67 reduction in 1st).
Anyway. I want to change the chainring to one with either 42 or 39 teeth.
So here's my "how long is a piece of string question":
Will the 39T ring be too spinny, or should I go for the 42, as it's closer to the 55/28 'ideal'?

NorwegianBlue

Sorry to be the one to say this, but the preferred gear depends on the rider. Ride with a group of other riders with multiple gears and on a given hill almost every rider will be turning a different gear at the same road speed.

The only solution is to suck it and see. Even then what seems right one day will seem too low the next day and too high the day after that.

buddha

After a quick morning ride I reckon 4th gear (1.27 with 48/22 setup) is fine for my max crusing speed. So playing around with ratios this means I ideally need a chainring of 40.64 teeth. Which is pretty much in the middle of the 39 and 42 tooth rings available.

So as you say, I'll have to suck-and-see. And get and try out both. Though I just found some Stronglight rings for £11 each

Thanks for your help, Peter

steverile

Going from 48 to even the 42 is quite a change. I'd try that first. 42x22 is a pretty spinny ratio, which you might get fed up with coming *down* the other side of your hills. Anyway, like the man said, we're all different. Enjoy

NorwegianBlue

There's always a Surly Dingle sprocket and a double chainset for a choice of gears.

Monty Dog

I find my gear ratio is as much set by my downhill speed as much as uphill - you soon learn to grind up any hill - I regularly ride the Surrey Hills on 48/18 and can pretty well get up most - just differing in the degree of pain or body language required to get up the hill. However, coming down the other side is just as important - too low a gear means that unless you can spin 180rpm plus, you may find control difficult. I'd seriously suggest that you look at something like a 46 or 44 tooth chainring to enable you to maintain a decent speed on the flat and downhills and you'll soon develop the leg strength to get up most hills.

NorwegianBlue

Hills? Surrey?

Edwin

Put some effort in and build your legs up. I run 48/12 and do some pretty steep hills. Perhaps I'm just insane?

graham_g

Edwin wrote:

Put some effort in and build your legs up. I run 48/12 and do some pretty steep hills. Perhaps I'm just insane?

Unless the 12 was a typo, then yes, you are insane

Edwin

Nope, not a typo. I'm obviously insane. It's a bit slow uphill, but downhill I've had 41mph out of her. I hate spinning too quickly downhill!

steverile

108". Jesus.
...you should have a go on the track!
Have you been riding that monster for long? We're all different I know, but I'm pretty sure it would knacker my knees.

PS I can get almost 40mph out of 42x16 and I'm far from the fastest of spinners.

Edwin

Strangely enough I've been riding the track league all summer and I'm rubbish! I have to use a club bike instead of my Langster as it's got brakes on, and it just feels all wrong. I get cramp building up after a few laps and haven't done better than fourth place in anything all season. I'm probably knackering my legs riding to work every day opn that beast of a gear. It's my first season racing though, so I'm going to develop a new strategy next year.....

NorwegianBlue

Firstly it's a five minute job (if that) to convert a langster to track use and back again. All you need is a spare set of bars without brake levers. Unclamp the bars from the stem, remove the brake calipers and clamp in your other bars. Simply reverse the process at the end of your track session.

Secondly I don't want to cast aspersions, but even the greatest tour riders in the days before derailleurs were allowed didn't run that sort of gearing on the climbs. Even sticking to the A-roads round here (I'll ignore the unclassified switchbacks) I honestly don't see them as climable at even walking pace on a gear that big. I'll think of you next time I'm climbing Holme Moss.

Edwin

Thanks for that idea, I'm not sure it's that simple as I've got a computer as well with wires going to the front forks, and the cranks for cadence. The wires are wrapped round the brake cables so it might be a bit tricky. I'll look into it though as it's a good suggestion.
Don't worry about casting aspersions, it's a bit of a silly ratio. I'm not showing off, I just like the challenge of a ridiculously big gear, and when I'm bowling along on the flat at 20-25mph I'm spinning 90-100rpm so it's spot on. I used to live in Leeds so I know West Yorks is pretty hilly, but I honestly get up Himley Road in Dudley every night and that's fairly steep. The first time I tried it I nearly fell off I was so slow, but after buiilding my legs up and losing a bit of weight I can manage about 8-12 mph up it on that gear.
The real problem is that my increased leg strength hasn't translated into much of an improvoment on my road bike, or the track. Surprisingly honking a big gear up hills just makes you better at.........honking a big gear up hills. I'll put the old wheels back on for the winter, with the original 16T cog (might be 17T, can't remember) and devise a new winter training strategy ready for next season.

NorwegianBlue

I know what you mean. Leg strength isn't the same thing as efficiency, so it doesn't translate to overall performance. Conversely having to spin your legs off in a low gear does seem to improve your performance a little.

I don't ride geared bikes at all. I have my fixed, my single and my dirt bike which is also single speed. And I find that keeping the gears low seems to make for the best average speed. My fixed is about 72", my single 64" and my dirt bike 58" which is really too high for off road use. I'm thinking of reducing the fixed to the same ratio as the single speed and seeing how it goes, I might fit a freewheel to the other side for the downhills. That's the nice thing about living in properly hilly country the climbs and descents are both pretty long so it's worth stopping at the top and flipping the wheel to change gears.

Edwin

Wow, you really like to ride fixed. I got one to increase my cadence and after a while people started telling me I was spinning too quick, that's the reason I went for a big gear to work on power. Think about TT-ing though, the pros will be pushing 54/11 or even a 55 chain ring, although obviously that's with a full range of gears they can work up through. It all depends how you ride I suppose.
Anyway, I've hijacked this thread, to reply to the original poster, around 70inch is generally considered about right, 48/22 is already lower than that so I wouldn't go for a 39T - that's like bottom gear on a road bike with a standard double. If you are struggling I'd be inclined to say work on leg strength. Losing weight has really helped me with hills as well, this might be something you want to look at unless you are really skinny already.
No offence!

steverile

20-25mph I'm spinning 90-100rpm
I'm not persecuting you here, but I honestly think your numbers are out!
Something like 42x16 will give you about 90-100 RPM at 20mph.

Have a fiddle with http://software.bareknucklebrigade.com and see what sort of numbers you get...

Edwin

Fair point, my cadence sensor stopped working the other week and I haven't bothered fixing it. That was off the top of my head and no doubt completely wrong. Will report the actual figures if I can be @rsed getting it working again. Thanks for the link.
Still think the OP wants a gear that's a bit on the low side though......

Monty Dog

When TT'ing on fixed, you'll find riders use something like 50x16 as you need to be able to get on top of the gear, particularly at the start or if you've got any slight hills. Norwegian Blue - paradoxically, there are some short and steep hills in Surrey - 20-25% and it's possible to link together a 100 miler with about 8000 feet plus of climbing - enough to test any fixed-gear rider both uphill and down.

NorwegianBlue

When it comes to sustained hill climbing this is my theory:

Imagine being at the gym and lifting the heaviest weight you can manage without popping something. Now imagine, say, fifty reps of that. Hard work? Can you even manage it without a break? And you'll be shattered by the end of it.

Now take half that weight and try one hundred reps in the same time as you managed fifty with the original weight. Easy isn't it? And you still feel pretty fresh at the end of it. In fact you could probably keep going all day.

That's like the difference between a sustained climb in the highest gear you can manage and a much lower gear. The important bit is keeping up the cadence so you are still doing the same or a higher speed.

Big gears are over rated for climbing. Obviously however they're great for descending.

peejay78

"Gearing rule-of-thumb: your chainring should not be larger than your front wheel."

NorwegianBlue

peejay78 wrote:

"Gearing rule-of-thumb: your chainring should not be larger than your front wheel."

It's a good idea if it's bigger than your sprocket too.

Try telling that to some mountain bikers though.

22/34 gearing? 17 Inches? 100 rpm would be about 5mph, there comes a point when it's better to get off and shoulder the damn thing. Perhaps that's why I gave up on MTBs and got a cross bike (now deceased).