GT Timberline Service

[KneesUp]

If it looks like 118 it's almost certainly 118 - the exact model isn't listed with good old Sheldon, but lot's of similar age / level Shimano triples were 118.

https://www.sheldonbrown.com/bbsize.html

 

[Ajax Bay]

I’m assuming that the measurement is taken from the ends of the square drives?
Any recommendations on the easiest reassembly order for the axle and bearings/end caps?

Measure from square taper end to end. Ignore threaded. Hal fords have a 118mm BB for a tenner which would be fine for this bike which will get little use. ETA: Spa Cycles have a wide range: eg Stronglight BB.
Reassembly of current cup&cone:
Clean everything. Toothbrush for the BB shell threads and paraffin (or whatever) in a cup to get the caged bearings clean.
Replace the now heavily regreased caged bearings into both the right and left side cup; and screw the right one in tight (reverse thread).
Grease on both cones of the spindle and insert so right cone is up against bearings.
Screw the left hand cup in till resistance, and then screw on lockring gently tight.
Check spindle cannot move in and out. Check spindle spins smoothly.
Adjust compression till above criteria optimised (loosen lockring, turn cup as nec, tighten lockring, check).

 

[C R]

Measure from square taper end to end. Ignore threaded. Hal fords have a 118mm BB for a tenner which would be fine for this bike which will get little use. ETA: Spa Cycles have a wide range: eg Stronglight BB.
Reassembly of current cup&cone:
Clean everything. Toothbrush for the BB shell threads and paraffin (or whatever) in a cup to get the caged bearings clean.
Replace the now heavily regreased caged bearings into both the right and left side cup; and screw the right one in tight (reverse thread).
Grease on both cones of the spindle and insert so cup is up against bearings.
Screw the left hand cup in till resistance, and then screw on lockring gently tight.
Check spindle cannot move in and out. Check spindle spins smoothly.
Adjust compression till above criteria optimised (loosen lockring, turn cup as nec, tighten lockring, check).

I would also suggest using self extractor bolts if replacing the BB, it will save you faffing about with the crank extracting tool.

 

[Tenacious Sloth]

Measure from square taper end to end. Ignore threaded. Hal fords have a 118mm BB for a tenner which would be fine for this bike which will get little use. ETA: Spa Cycles have a wide range: eg Stronglight BB.
Reassembly of current cup&cone:
Clean everything. Toothbrush for the BB shell threads and paraffin (or whatever) in a cup to get the caged bearings clean.
Replace the now heavily regreased caged bearings into both the right and left side cup; and screw the right one in tight (reverse thread).
Grease on both cones of the spindle and insert so cup is up against bearings.
Screw the left hand cup in till resistance, and then screw on lockring gently tight.
Check spindle cannot move in and out. Check spindle spins smoothly.
Adjust compression till above criteria optimised (loosen lockring, turn cup as nec, tighten lockring, check).

Thanks for that.

The bearings x 11 are actually loose. I guess there are probably only 10 if caged?

I haven’t had a chance to clean the cones and cups yet to see if there is any pitting (daily life got in the way).

I did eventually find that sealed unit on Halfords and will probably go for that if there is any damage. My preference is to re-use what is fitted as the axle is slightly offset and I don’t want to mess with the chainline.

As I work Mon-Wed I probably won’t get a chance to look at this until Thursday.

On the plus side my wife did 10 miles today and is talking about keeping it up, so fingers crossed.

 

[Tenacious Sloth]

Ok. The BB is back in. The cups and cones were just about acceptable and a clean, regrease and assembly has got it working with no play and just a very gentle rumble that’s not noticeable when pedalling.

I think it’ll be ok for the mileage she’ll be doing on it - if it does give any further problems then I’ll stick a sealed unit in.

I’m attempting to keep the parts bill to zero as everything is fairly dilapidated including the frame, so not really worth spending money. I have spare grips, cables and pedals in my spares cupboard, so I hoping to charge her nothing.

Right then. Next problem. The brakes are shocking.

The pads look to have plenty of meat on them, so a good clean and resurface with wet and dry should suffice. The front cantilever is not working well at all, with nearly all of the movement happening on the right-hand side. I went to adjust the centering screw - but it’s missing!

Anyone have any idea where I can source a replacement screw? It’s a Shimano BR-M502 cantilever brake unit.

 

[KneesUp]

Not got a spare screw, but if one side is moving less it's probably worth removing the arm and giving the mounting post a bit of a once over with some of the wet and dry, as you have it out anyway. Then grease the post before you replace the arm

 

[Drago]

Is that a 4130 frame? If so, the tubes can be as little as 0.4mm thick in places, so were it in my workshop id clean and grease the seat post first, and then clamp it via the seat post.

Nice bike, and fair play for helping someone out.

Service, set up and toe in the front brakes. If that doesn't bring the desired result shorten the cabke above so the apex of the straddle portion is lower down and closer to the wheel. This should improve effort, albeit at the cost of a little feel and modulation.

 

[Tenacious Sloth]

Not got a spare screw, but if one side is moving less it's probably worth removing the arm and giving the mounting post a bit of a once over with some of the wet and dry, as you have it out anyway. Then grease the post before you replace the arm

Yes. I was going to do this anyway. The reason the left side moves less is because it’s very near the wheel rim due to the absence of the centering screw.

Is that a 4130 frame? If so, the tubes can be as little as 0.4mm thick in places, so were it in my workshop id clean and grease the seat post first, and then clamp it via the seat post.

Nice bike, and fair play for helping someone out.

Service, set up and toe in the front brakes. If that doesn't bring the desired result shorten the cabke above so the apex of the straddle portion is lower down and closer to the wheel. This should improve effort, albeit at the cost of a little feel and modulation.

It’s Tange 1000, so fairly agricultural. I’m always very careful clamping frames. I recently treated myself to a Feedback Sports Pro work stand which seems to hold bikes very steady with very little clamping force.


I’ll maybe have to wait until bike shops are open to drop ins and see if I can source a centering screw from them. There are a few good bike shops in Peterborough.

 

[I like Skol]

Any suitable M3/M4 bolt should do, it will be a standard metric thread.