80mm BCD 5 arm chainrings?

Shadowduck

Hello everybody peeps,

The compact double on my poor old roadie is looking a little tired and I'd like to replace it with a standard double (as I regularly spin out and rarely use the small ring).

The problem I have is that it's an old Stronglight five arm crankset with an 80mm BCD - chainrings with such a small BCD seem to be incredibly hard to find and those few that do exist don't go up to the sizes I need. Does anyone know where I might find such a beast?

To complicate matters further, it's a six-speed running a 6/7/8 speed chain - would it be a problem to stick a chainring designed for nine-speed on there?

All advice gratefully received!

Monty Dog

Try the likes of Spa Cycles

dennisn

Shadowduck wrote:

Hello everybody peeps,

The compact double on my poor old roadie is looking a little tired and I'd like to replace it with a standard double (as I regularly spin out and rarely use the small ring).

The problem I have is that it's an old Stronglight five arm crankset with an 80mm BCD - chainrings with such a small BCD seem to be incredibly hard to find and those few that do exist don't go up to the sizes I need. Does anyone know where I might find such a beast?

To complicate matters further, it's a six-speed running a 6/7/8 speed chain - would it be a problem to stick a chainring designed for nine-speed on there?

All advice gratefully received!

Just curious what chainrings and freewheel or cssette you are using that you "regularly
spin out". Doesn't sound like a normal 50-34 crank with a 12-23(or the like) on back.

Dennis Noward

Shadowduck

dennisn wrote:

Just curious what chainrings and freewheel or cssette you are using that you "regularly
spin out". Doesn't sound like a normal 50-34 crank with a 12-23(or the like) on back.

I can answer that, 'cos I counted 'em this very afternoon!

I've got a 48/36 on the front with a 14-28 six-speed on the back, meaning that a little over 20mph has my legs going far too fast to give any meaningful propulsion! Ideally I'd like to go to something like 53/39 on the front to give me a bit more on the top end.

Shadowduck

Monty Dog wrote:

Try the likes of Spa Cycles

Is this likely to be more of a touring thing then? The bike has a rack and mudguards so I usually refer to it as a tourer but didn't realise it was particularly specific...

Spa Cycles have a huge range of chainrings, I can see 64mm and 86mm BCD but no 80mm I'm afraid. I'm beginning to think I should just flip the old ones and learn to pedal at 120rpm.

aracer

The question is, how much of the time do you find yourself riding faster than 24mph (90rpm on that top gear) on a bike with mudgaurds and rack? If you're not even managing to pedal that fast without "spinning out", then I'd suggest you should work on your spin rather than buy new kit (BTW 120rpm would be over 32mph, so I doubt you'd often need to pedal that fast).

Then again, are you sure it's 80mm BCD? That's not a size listed by the great Sheldon
http://sheldonbrown.com/harris/chainrings.html even amongst his obsolete sizes.

Shadowduck

aracer wrote:

The question is, how much of the time do you find yourself riding faster than 24mph (90rpm on that top gear) on a bike with mudgaurds and rack?

None of it, with the current gearing! :P

aracer wrote:

If you're not even managing to pedal that fast without "spinning out", then I'd suggest you should work on your spin rather than buy new kit

When I posted this topic, I wondered how long it would take for someone to tell me I just need to up my cadence... To be honest, I've been putting some effort to doing just that - even my current 75 - 80rpm used to feel horribly fast to me but I'm sort of used to it now.

On the other hand, given that I'm regularly riding a bike which is so old I don't even know how old it is, I don't think I can be accused of just buying kit for the sake of it! I don't see the point in having twelve gears and only using the top four 95% of the time - since the chainrings need replacing anyway, can you give me a good reason not to go to ratios which seem more appropriate and useful to me? I'll still have plenty of lower ratios if I need them, and the front shifter might actually get used!

aracer wrote:

Then again, are you sure it's 80mm BCD? That's not a size listed by the great Sheldon
http://sheldonbrown.com/harris/chainrings.html even amongst his obsolete sizes.

Well, there's always a bit of guesswork involved since it's a five arm crank, but I've measured it three different ways (eyeball & steel rule / calipers & steel rule / digital calipers) and they all pretty much agreed. Another hint is that it says "Stronglight 80" down the side of the crank, but I suppose that could be referring to something else.

If I can't find anything to do the job I'll just keep training my legs to spin faster!

aracer

Shadowduck wrote:

Another hint is that it says "Stronglight 80" down the side of the crank, but I suppose that could be referring to something else.

Well why didn't you say earlier? A Stronglight 80 crank is 86PCD. By all means if your chainrings are worn get some new bigger ones, but I'd suggest working on your spin too - 80 is still on the slow side, and pushing big gears isn't good for the knees.

Shadowduck

aracer wrote:

Shadowduck wrote:

Another hint is that it says "Stronglight 80" down the side of the crank, but I suppose that could be referring to something else.

Well why didn't you say earlier? A Stronglight 80 crank is 86PCD.

Aye, that might have helped. :oops:

aracer wrote:

By all means if your chainrings are worn get some new bigger ones, but I'd suggest working on your spin too - 80 is still on the slow side, and pushing big gears isn't good for the knees.

I do try to up the cadence, and sometimes manage to pedal faster for a while but I find it very difficult to do so - partly because it feels totally unnatural to pedal so frantically and partly because my breathing isn't really up to it (asthma). Over time I should be able to overcome the first problem and increased fitness will help with the second, but it's not going to be a quick process!

Since there seem to be two schools of thought on cadence - with a couple of clicks I could be reading some fixed gear fan telling me how it makes you stronger slogging up hills in gears way higher than I'd use for climbing - is it really so bad to stay around the 80rpm? Serious question, without snark. In fact, I've started a poll and if the consensus of opinion is that I should stick with the granny gears and try to up the spin rate, I might delay the change of cogs a couple of months and put some real concerted effort into it!