Cassette Ratio's

[Tigerbiten]

If it is a 130 BCD then a 38t is the smallest chainring that will fit.

But what's your front mech and shifter ???
An other option is to use a triplerizer to go from a double to a triple if your shifter/mech will allow it.
That will let you go for something like a 50/38/28 front without changing the BB.
But you may also need a longer cage back derailleur to take up the extra slack.

Luck ............

 

[stevey]

If it is a 130 BCD then a 38t is the smallest chainring that will fit.

But what's your front mech and shifter ???

Veloce FD & Veloce shifters with thumb shifts

 

[ColinJ]

I can suggest something which would make a huge difference, but you may not feel happy tackling it... If you have any doubts about it, get someone more skilled to check that your bike is suitable and to do it for you!

I had exactly the same gearing on my CAAD5 and was finding 39/29 a bit OTT for the steep climbs that I often encounter in this area. The first change was to get hold of some 12-30 cassettes. I'm not sure if Campagnolo still make them, but the 30 gives only a 3.4% reduction vs the 29 anyway so I wouldn't worry too much about that.

I discovered that my 10-speed rear shifter is quite happy working with a triple chainset so I bought THIS ONE from Spa cycles. My rear mech had enough capacity to work with the change as well. I fitted an Ultegra bottom bracket to suit the new chainset.

I went for the 48/38/28 chainset so my bottom gear is now 28/30, more than 30% lower. It makes all the difference on the steep stuff. My top gear is very slightly lower, but no problem - I don't generally ride around at 50+ kph (except downhill) and I can always freewheel when I start spinning out.

My front mech didn't quite move far enough to shift to the 3rd ring because a metal tab pushed up against the seat tube. I managed to file enough off to overcome the problem.

When the middle ring wore out I replaced it with a 36. That is really nice with a 12-30 cassette. I can stay on the middle ring most of the time and the changes between the rings feel better spaced.

My 'triplised' bike...

 

[Ajax Bay]

Pretty sure that you can swap in a new compact (50-34) and it doesn't need to be Campagnolo.
Agree with most of @ColinJ comment, but I'd keep it simple: stick to two rings. The left ergo will click across that nicely and with the 34t the OP will have gained a gear 13% lower. I'd go for Spa too: https://www.spacycles.co.uk/m8b0s109p45/STRONGLIGHT-Impact-Double
And unless the OP is 6 foot +, then their knees will appreciate a crank length of 165mm - see the text on the page I linked.
The RD should handle that extra 2t (50-34, whereas current 53-39) without difficulty.

 

[Brummie53]

I have read the posts with interests and confess to not being technically/mechanically minded. Could someone please explain what the numbers are on the chain set in a simplistic form and how this would help in the actual riding of the bike. Or is there a good Dummies guide I could use? Many thanks.

 

[Ming the Merciless]

I have read the posts with interests and confess to not being technically/mechanically minded. Could someone please explain what the numbers are on the chain set in a simplistic form and how this would help in the actual riding of the bike. Or is there a good Dummies guide I could use? Many thanks.

The numbers refer to the number of teeth , the bits that stick out and the chain engages with. More teeth at the back means hills are easier. More teeth at the front means you can pedal for longer downhill before you legs are spinning too fast for you to keep up.

 

[Ajax Bay]

please explain what the numbers are on the chain set in a simplistic form and how this would help in the actual riding of the bike.

A chainset is a crankset with chainrings. There may be one, 2 or 3 rings (and @Ian H will have an image of one with 4 ) - current vernacular: 1x, double/compact/semi-compact, triple.
Combined with a sprocket at the rear this allows the rider to 'gear up' (or down) their pedalling to produce a torque at the rear wheel to enable efficient forward propulsion.
Number of teeth
Each ring has a number of teeth eg 48t. When the chain is on that ring and a 12t sprocket at the back, the gearing advantage is x4: so every turn of the cranks turns the rear wheel 4 times. A reasonable/typical cadence (number of revolutions of the cranks per minute) is 80rpm. So @ 80rpm in the 48/12 combo with a wheel circumference of 2.1m means the cyclist is travelling (and applying effort) at 80 x 4 x 2.1m (= 672m) per minute or 40kph / 25mph.
With that top gear a cyclist can pedal faster (higher cadence) but sooner or later the cyclist will 'spin out' and no longer be able to pedal fast enough to apply any force to the pedals. With this gearing the speed at 120rpm would be over 37mph and most riders would have gone into a tuck and freewheel way before then (or be running a bigger gear eg 52/11).
Up a steep hill a cyclist will use their smallest chainring - say a 36t combined with their smallest sprocket (say a 32t): a gearing ratio of 1.125. Cadence will likely be lower uphill (YMMV), say 60rpm, so the cyclist will ascend at 60 x 1.125 x 2.1m per minute = 142m per minute or 8kph / 5mph.
If a cyclist tries to climb a hill with too high a gear they will reach the limit of the force they can apply to the pedals and 'stall': being forced to stop - falling over optional.
Have a play with this Gear Calculator.
Bolt centre diameter (BCD)
Chainrings are bolted onto the right hand crank with bolts: typically 5 or 4. The circle the bolts are on varies in size and different makers have chosen different variations: their size is described by their diameter their BCD. Typical values are 135mm, 130mm, 110mm and 74mm but there are many more, and a new or replacement ring must be exactly correct (BCD and number of bolts). See this Sheldon Brown link for more.
HTH
How many teeth have your chainrings got, @Brummie53 and what is the range of your cassette at the rear (eg 11-32)?

 

[Brummie53]

Thanks all for your help. I have an old ( unknown age) Apollo 10 speed and if I have measured/ counted correctly these are the sizes dimensions.
Chainrings- 180mm 42 T and 210mm 52T. The range at the rear is 14-24

I also have an elderly Raleigh Royale 5 speed with a chainring of 190mm 46T .
Range at rear 14-22.

 

[Ajax Bay]

If I may offer you a gratuitous suggestion (this assumes friction gear levers), you might wish to consider swapping the 5 speed blocks with a 6 speed ones - 14-27t. This will keep roughly the %age step between each gear but give you an extra gear when hitting the steepest hills - 12%. The 6sp block will screw onto the freewheel hub fine. Your current lowest gear (42/24) must be a challenge, unless you live in the fens or Holland. This Gear Calculator.

 

[Brummie53]

Thanks Ajax Bay, I’m looking at refurbishing one or both of the bikes over the winter months now I’ve nearly tamed the garden! I’ll give your suggestion serious thought. Not too many serious hills around here but it’s not flat either. Thanks again

 

[Ajax Bay]

Bitd my 5sp 14-25 freewheel broke and (in those days I was not competent) the bike shop I took it to could only quickly source a 6sp 14-28 freewheel which they fitted. Boy, did I appreciate the lower gearing the next time I climbed a steep hill?!
Good luck with any refurbishment.