Dual shift levers, old bike and indexed gears

Question

Long story:

 I once built a road bike for my wife over 30 years ago. It has Reynolds 531 tubing / 501 forks and alloy parts, so it is quite a decent build. However, my wife has been put off riding it again (after many years absence) as it has shift leavers on the down tube.

 As a solution I've managed to get a pair of Shimano Tiegra levers. I've now installed these (after some cabling gynecology). The gears do work as, fortunately, do the brakes, but they are very clunky/jumpy. I suspecting a number of things are the issue!

1. A worn chain
2. Non indexed rear block (is there such a thing?)

The front chainset is an alloy TA double with plenty of miles left in the teeth.

The rear changer is a shimano DuraAce. There are 5 cogs on the back and the matching the Tiagra dual control

So ... recommendations/answers please!

Is there a means to tell if the rear block is/is not indexed.

I vaguely recall the recommendation that you always change to block/chain and front rings at the same time. Is this still true?

If I need to update the front cogs how do I find the correct fit the bottom bracket axle (if i need to buy online)?

I'm suspecting this may be a pre metric bike as the wheels are 27" x 1.25"

Also, what is the best method for checking a worn chain!

I do have quite a lot of experience with bike maintenance, but I'm a little rusty.!

Answer 1

Most likely your Tiagra brifters (brakes+shifters) are 8 to 10 speed depending on their age, so the cable pull is different to a five speed cassette and probably pre-dates hyperglide.

So count the number of clicks on the right brifter, and add one. That's the gear count you need to match. On the left side brifter you want a double, so just one click, or two if the bike has a triple. More on this later.

You will need a replacement back wheel, cassette, and chain. All that needs to match the gear count of the right brifter. The OLD of the rear wheel will have to be the same or very close to the OLD of the existing wheel. But its a steel frame so can take a small amount of cold-setting, if you make the rear dropouts parallel again afterward.

You might need a new rear derailleur, because the cassette may have a larger large and smaller small cog than the original.

You are unlikely to need replacement chainrings assuming the wear is good. The front derailleur mech should be okay but may need to have the cage narrowed for the thinner chain.

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You can do this.

I have a 1981 Raleigh Arena with 3x9 speed Shimano 105 groupset on it. I changed the wheels and the entire transmission. As a result of going from 27" to 700c wheels, the brake calipers didn't reach so I had to replace them with long-reach ones. The bike now looks like this:

EDIT Another possible issue with your front chainrings is that the cable pull on the LEFT brifter might not match the inter-chainring gap. As a somewhat halfway solution, you can leave the left downtube shifter running the front mech while connecting the right brifter to the rear mech. Downside here is changing chainring means a downtube friction shift, but trimming this shift is easier. Friction shifting makes a lot of things easier.

Any questions please ask.

Answer 2

A worn chain will certainly make shifts less smooth. You can use a 'chain checker' to see if the chain is worn, or measure the distance between links with a decent (steel) ruler. They should be 1" apart, an increase of 0.075" is time to replace (take an average over many links).

The indexing issues are likely to do with the Tiagra levers on a 5 speed block. The earliest Tiagra groupset (listed on wikipedia) is 9 speed. So whilst the derailleur will most likely be compatible (Shimano made them work the same up to 10speed), the levers are probably not pulling enough cable to shift the 5.5 mm between 5 speed cogs. I think the first (Dura Ace) Dual Control levers were made for 8 speed cassettes where the rear cogs are 4.8 mm apart, so it won't be possible to get dual control levers to match the 5 speed block.

You can find out how many gears the Tiagra levers expect by counting the number of clicks they make and add one (9 speed clicks 8 times each way). Then the number of cogs on the block must match. It may be possible to source a new block that suits the levers, but then, the wheel and/or frame might not be spaced wide enough to accommodate this, given the age you indicate.

And yes, if you install a new block/cassette, you should install a new chain. If the Bottom Bracket axle is square taper then a square taper crank will fit. The axles are available in different lengths you can measure the existing one when cranks are off.

You can 'cold set' a steel frame to increase the spacing to accept a new, wider rear wheel for more gears if needed, but this is likely to require going from 120 mm to 130 mm which is relatively large increase and may not be recommended/ideal. Then if you can only source 700c wheels the brakes may or may not reach... and if you want to replace chainrings or anything else too it is looking expensive. Maybe 20 years ago it would have been simpler because these changes would have been more incremental at the time, but now the types of parts readily/cheaply available have changed so much that there is less compatibility.

There are videos on changing things like 27" to 700c wheels easily found online, but I think it is worth researching first and estimating how expensive things could get in total before going too much further. Don't forget cost of tools! (Freewheel tool, crank puller, BB tool...)