Decided to make some alterations to Greta’s setup as we were in for a rebuild anyway.
Visited Nigel at Chase Cycles to discuss the rebuild and decided to:
1 Take off the 63 tooth big ring because touring in the Alps we would not use it climbing and would be freewheeling and braking when descending. This would also reduce the vast amount of potentially loose chain, and allow us to position the front mech in a much better alignment to the chain rings.
2 Use the reduced gear capacity to replace the rear mech with a medium cage version to give us a bit more road clearance.
3 Change the plain middle chain ring (now the big ring) to a decent Middleburn one with some ramps and pegs to make gear changing slicker.
4 And while we were at it reposition the chainset to reduce the leg length for Sheila. Not an easy task. Unlike on a normal bike just raising or lowering the saddle, this is akin to shifting the bottom bracket and requires careful setting up to keep everything square as the 4 bolts are tightened down evenly in a new position.
Nigel ordered the new chain ring and XT rear mech. We had plenty of new chain in stock and after searching the internet found someone in Taiwan who could sell us a chain guard to replace the outer third ring.
A week or so later all the bits were in and we chose a fine day (can’t get Greta into Nigel’s shop so had to work on her outside on the forecourt – providing street theatre for passers by) and went back to Chase Cycles.
New mech on, new chainring set up on, new chains on. Give it a whirl. New chain ring shifter excellent and re-set end stop for a double chainring. But Rear mech would not shift consistently, jumping sprockets up and down.
After a lot of fiddling we rechecked the less than clear packaging and realised we had been sent a 10 speed mech and although the indexing is all in the gear lever the mech itself moves at a steeper angle for 10 speed to 9 speed and the derailleurs are not interchangeable. Took it off and packed up to return home.
A couple of days later Nigel kindly brought the replacement one to our house after work. Set it all up and it worked a treat.
Now we just had to sort out repositioning the front boom to match leg length and chain to the new set up for Sheila and then go for a spin. A few laps of the car park seemed to go well with everything shifting smoothly.
Next fine weather free morning off we went for a bedding down run.
Did not get to the bottom of East Hill without serious concern. Left front brake squealed loudly and shook fiercely. We struggled on as far as Passford House hotel and then gave up and limped home carefully. It was not just brake squeal, the whole left front of the trike seemed about to shake itself to pieces. Why was this? Brakes were OK until the great Dorset Coast. Disaster.
Period of deep depression. Not helped by ongoing bathroom refurbishment disaster back at home. Should we give up on Greta and refurbish Gertie Greenspeed before going on holiday?
Studied the Magura tech manuals on website and emailed them. Read lots if stuff about disc brakes. emailed Greenspeed to ask if they had any ideas.
Took it all to pieces. Cleaned the rotor and calliper thoroughly. Put on new brake pads. No change.
Went off and cycled the Round The Island Randonnee on Gertie, leaving Greta in pieces in the workshop. Great day, no problems. Well not many – while parked at the start an incompetent cyclist crashed into John sitting on the trike and fell on top of both smashing the wing mirror and mudguard.
Some time later with scissors and allen keys we had freed the mudguard and half of the supporting bracket, and had removed the near side mirror, re-configured it to be an off side mirror and fitted it in place
A few days later Jason came round to have a look at Greta. Took the brake assembly and pads all apart. Cleaned everything again and re-assembled the lot. No change. Decided the brakes MUST be set up OK, so the problem had to be elsewhere. Trouble is what could cause brake squeal and judder if not the brakes? Next thing in the structural chain is the stub axle and king pin assembly. At face value nothing had been altered here, but I had removed and refitted the mirror/mudguard post that screws onto the top of this assembly. We had a play with the steering and decided that it was fine but a shade stiff so if we were to change anything we should slightly slack the nut holding down the king pin. Backed it off one flat. Spun the wheel and gently held the brakes on……No noise.
Only a proper test run would prove the case, but had we finally discovered the problem. Namely, resonance between the disk brake assembly and king pin steering assembly just hitting the required frequency to feed-back and amplify itself in a self-destructing vibration. Classic engineering unexpected failure. Just moving the king pin nut a trace had damped the relationship and stopped the resonance.
There was still a bit of daylight, so as Jason headed off to take his father out for dinner, J & S put Greta together and took her into the car park for a series of laps and stops. Rapid, progressive braking and no squeal. No shake.
Back to today.
First proper run, over to Crow and back including a few downhill stops. All seems well. Just need to get our legs to work, get a bit better at shifting the Schlumpf Mountain Drive and we might just be triking again on Greta. Spent the evening on fitting “luxury” items like a bracket for rear light and the air horn.
Actually perhaps not luxuries, because Sheila has just discovered that our intended route in the Vercor includes a tunnel well over 1km long.