Problem re-installing TA Cyclotourist cranks

[Kenn]

I just removed a TA cyclotourist RH crank to replace chainrings on my 1980s King of Mercia tourer. On reassembly I found that the hex-headed bolts that hold the RH crankarm to the outer (large) chainring just foul the bottom bracket lockring, scoring a shallow groove in it. I can't understand why - they are the same bolts on the same crank. I have changed both chainrings but this doesn't change the distance between the crank and lockring. I haven't touched the bottom bracket. The crank-bolt was tightened to 40Nm (30 ft-lb).

It's hard to know what to do. I could chamfer one side of each of the five bolts and try to keep this inwards towards the lockring by tightening the nut rather than the bolt but this shouldn't really be necessary and seems a bit extreme.

If anyone has any idea why this could have occurred or has a solution I would be very grateful.

Thanks, Ken

[Brucey]

it isn't that unusual for the crank to pull on a bit further when it is reinstalled. It is unusual for it to make a difference though.

I wonder if you can adjust the clearance in the bottom bracket somehow?

Alternatively slimmer heads on the bolts might do it.

Bit annoying this but I'm sure there is a solution.

cheers

[BigG]

There seems to be something odd here. The right hand bearing cup is normally fixed and does not have a lock ring. Only a few fairly rare designs (Phil Wood, Kajita and some old Suntour) have lock rings both ends to allow adjustment of the chain line. The right hand cup is normally (always?) left hand thread on British bikes and the binding of the crank bolts would therefore undo it. Indeed, if the interference was enough to wear a groove, then I am surprised that you can turn the cranks at all. Lock rings are normally chromed steel whereas the five TA bolts are alloy. Alloy bolts wearing a groove in the steel ring seems unlikely. Finally, because both the middle and inner rings on the TA Cyclotouriste are mounted inside the outer ring, the crank is fixed to a fairly long axle, typically 127.5 mm. This carries the fixing bolts well clear of the bottom bracket if the inner ring and its fixing bolts are to clear the chainstays. Have you perhaps removed the axle and remounted it the wrong way round? All very odd. Have I completely misunderstood the situation?

[Brucey]

....whereas the five TA bolts are alloy....

steel, usually....

and fag paper clearances are not at all unusual here, depends on chainline...

photos might help

cheers

[Kenn]

Thanks for all your help. My description of the bottom bracket may not have been entirely accurate - I'm not an expert and don't know all the exact terms. The bottom bracket is a sealed cartridge (I don't remember what make - Mercian put it in a long time ago and I saw it at the time. The bike has been mothballed for almost 20 years). I assumed it was held in place by what I called a lockring at each end. The RH cup seems to be alloy with a slight step and bevel around the outer edge. The corners of some of the TA alloy bolt heads cut a very shallow groove in the bevel. I didn't ride the bike - just turned the crank by hand during reassembly. I smoothed the groove out with a fine file and there is no real damage. I have never removed or adjusted the bottom bracket in any way. The inner ring I removed was close to the chainstay but cleared it OK. The smaller ring I put back clears it easily.

I think Brucey's diagnosis could be right. I didn't check the clearance before pulling the crank. I had no reason to, but I remember that it was difficult to slide a rag behind the chainwheel to clean around the bottom bracket.

The chainwheel to crank bolts have 3mm deep heads. The "sleeve nuts" (I don't know if there is a correct term here) have 1.5 mm deep heads. There is also a washer under the bolt heads. A quick look tonight makes me think it may be possible to reassemble with the nuts towards the bottom bracket giving more than 1.5 mm of extra clearance. I checked the nut sleeve length against the depth of hole in both the crank and ring and it should work either way. I plan to try this tomorrow when I have time to do it carefully and will let you know what happens.

Cheers, Ken

[simonineaston]

Just like to add my tuppence worth as a Cyclostourist newcomer... I have a couple of bikes with this lovely narrow Q crankset fitted to them, and I recently changed one of the chain rings. The 5 tiny nutsNbolts that hold the chain ring onto the right side crank were difficult to fit - I could get 3 out of 5 in OK, but the 4th was not easy to press into its hole and when it came to the 5th, I found it wouldn't go in at all. After lots of experimentation, I found that the holes in the crank did not exactly line up with the holes in the chain ring, in spite of the fact that both were, as far as I could tell, genuine TA products... so, my advice is, check to see that all 5 tiny nutsNbolts are correctly seated in their respective holes, and if not, be prepared to undo them and turn the chain ring round, with respect to the crank, so that different holes in the chainring ring line up with different holes in the crankset... My idea is that although you may have been able to add all 5 nutsNbolts on reassembly, 1 or more of them might not be seated correctly, and so may be fouling the b/b ring. Certainly on my 2 bikes (F frame Moultons) things are a bit tight down there!

[Kenn]

Problem solved! Thanks for all the help. Reversing the nuts and bolts worked perfectly. The thickness of the crank arms amd outer ring are almost the same so the sleeve bolts work fine either way. Now have over 1.5 mm clearance.

I'm now sure that the RH crank arm pulled in a bit more on re-installation - so once I knew it wasn't something stupid I could look at simply increasing the clearance.

Now on to the next problem. Front mech won't slide down enough for much smaller chainrings (which match my ageing legs) without fouling the chainstay. Short term I'll put back the larger outer ring and fit a bit (rather than a lot) smaller inner ring ( I have a few TA rings tucked away). Long term I'll either change the front mech or put on a 32 or 34 tooth freewheel and keep the larger chainrings.

Can't wait to get back on the bike after 20 year layoff!

Thanks again, Ken

[531colin]

What sizes chainrings have you fitted?
TA Cyclotourist chainsets are awkward in that there isn't enough gap between the crank and the big chainring to fit a modern mountain front mech., which on the face of it is the easiest solution for small chainrings. (thats what they are designed for!)
There may be "obsolete" front mechs. still knocking around which will do the job, or it is possible to shorten the cage of the existing mech. eg. by cutting it down and silver soldering it to complete the "square"

[BigG]

The TA rings are spaced at 6.5 mm compared with 7.5 mm on modern triples. The front mech throw required is therefore 2 mm less. Old road double mechs will almost always cope with this and give no problems either with the (probably) smaller big ring or the chainstay clearance. The only problem might be the small to middle ring change as the Cyclotouriste middle ring will have no ramps or pins. I had no problem with this using a half-step arrangement but a smaller middle ring may not work well with a road mech.

[Kenn]

Thanks for the really helpful inputs. The bike had a 36/48 double and 14-28 six-speed freehub. I want a lower bottom gear as I don't want to risk knee injuries now I'm in my mid-sixties. I don't really need a high over 75-80 in.

I have TA inners of 26, 29 31 36 teeth plus 40 and 48 outers. I wanted 26/40 giving a bottom gear of 25in with a 77in top and a bit of overlap between front rings to reduce number of front changes. The 40 gives 13 mm gap to the front mech cage when it's as low as it will go without fouling the chainstay. Measurement and calculation show that 45 or 46 front will fit with 2mm clearance to mech, 44 teeth may fit with a 3-3.5 mm clearance.

The rear mech is a Shimano Deore XT super plate with, I think, a capacity of 40 or 42 teeth total. The front Deaore XT mech has, I believe a 22 or 24 tooth capacity.

I plan to try 29/48 which gives a 28 in low with no overlap. If this is too annoying I'll go to 31/48 which gives a single approx overlap and a 30 in low gear. If I need a lower gear I'll get a 44 outer and try 26/44 or change to a 14-32 or 14-34 freehub - probably 32 since the gaps in the 34 are a bit big.

If all of these don't work I'll sell the darn thing to someone with younger knees and put the money towards a new bike with a Rohloff.

Cheers, Ken

[Brucey]

if you can get hold of one, an older front mech meant for a double chainring will work fine with your set-up. Something like a suntour cyclone MkII would be perfect. It'll clear the crank and the chainstay, and it'll have enough enough capacity.

Incidentally 'modern' hyperglide sprockets can be made to fit your (I assume) UG freehub. Just grind one corner of one spline down. You'll need to keep the 14T top cog to hold the other ones on with. This opens up a variety of gearing options, including 7s, and maybe some 8 (from 9) options too. This could give you lower gears, a wider range, and smaller gaps.

cheers

[LollyKat]

For years I have used a Cyclotouriste half-step triple: 46-42-26 with an old Shimano 105 double mech - works perfectly.

[gaz]

.

[BigG]

I didn't realise you were using a double. My mistake again! The inner plate on the front mech then has a much easier task with both inner and outer plates just moving the chain on and off the outer ring - exactly what a double is designed for and the inner ring size is irrelevant.

[Kenn]

Just installed 44T/26T front rings and an IRD 14-32 freewheel. The front changer clears the chainstay with a sub 2mm gap to the front ring. Front and rear both shift perfectly.
My creaking knees really appreciated the low gears on a test drive today. The new freewheel weighs in at 540 grams but the whole bike is still under 26 lb which is pretty good for a 26 year old steel frame.
Thanks a lot for all the suggestions and comments - they really helped.

Cheers, Ken