Search found 199 matches

by Chris Jeggo
11 Oct 2018, 1:47am
Forum: Bikes & Bits – Technical section
Topic: Is this probably a bent derailleur hanger?
Replies: 17
Views: 1080

Re: Is this probably a bent derailleur hanger?

Congratulations! And I've learnt something from your experience. The radius of the rim will be somewhere in the region of 320mm (less than 16"), so a 10mm error turns out to be around 1.8 degrees, and that's in both the vertical and horizontal directions. In one of the 45 degree positions (half...
by Chris Jeggo
8 Oct 2018, 2:34pm
Forum: Bikes & Bits – Technical section
Topic: Continental brakes - Wrong way round
Replies: 114
Views: 3615

Re: Continental brakes - Wrong way round

Thanks for that, Brucey. Much food for thought.

I thought you might disagree with my DG Wilson quotations, and I would not disagree with any of your most recent post.

Chris
by Chris Jeggo
8 Oct 2018, 1:31am
Forum: Bikes & Bits – Technical section
Topic: Continental brakes - Wrong way round
Replies: 114
Views: 3615

Re: Continental brakes - Wrong way round

David Gordon Wilson in 'Bicycling Science' (MIT Press, 2004) has a section 'Rim temperatures reached during downhill braking'. He aims to estimate the steady state rim temperature achieved during descent of a long, steady gradient at a speed that is held constant by braking. At very low speeds air r...
by Chris Jeggo
7 Oct 2018, 12:18pm
Forum: Bikes & Bits – Technical section
Topic: Changing mountain bike tyres for road tyres.
Replies: 6
Views: 473

Re: Changing mountain bike tyres for road tyres.

Tyres certainly make a difference. When I bought a new touring bike I noticed that it rolled more easily than the old one. At first I put it down to the old bike's transmission, which needed fettling. But it turned out to be the tyres. The new bike had Continental Gatorskins while the old one had Sc...
by Chris Jeggo
6 Oct 2018, 4:00pm
Forum: Bikes & Bits – Technical section
Topic: Continental brakes - Wrong way round
Replies: 114
Views: 3615

Re: Continental brakes - Wrong way round

If your COG is height H above a level road and horizontal distance D behind the front tyre point of contact, then excessive braking will send you over the handlebar if the coefficient of friction is greater than D/H and cause a skid otherwise.
by Chris Jeggo
5 Oct 2018, 11:16pm
Forum: Bikes & Bits – Technical section
Topic: Older Dawes horizon headset size
Replies: 15
Views: 2182

Re: Older Dawes horizon headset size

If it surprises you that a 27mm crown race dia. is a traditional size on British bikes of the 1950s and 1960s, then note that 27mm exceeds 1 1/16 inches by a gnat's wotzit (half a thou in this case).
by Chris Jeggo
5 Oct 2018, 7:32pm
Forum: Bikes & Bits – Technical section
Topic: Continental brakes - Wrong way round
Replies: 114
Views: 3615

Re: Continental brakes - Wrong way round

To slow a vehicle requires a horizontal force applied at the centre of gravity (CG). The actual braking force is applied at the tyres, thus generating a couple, or turning moment. In normal braking the vehicle does not topple because an opposing couple is generated by weight transference, the load (...
by Chris Jeggo
5 Oct 2018, 4:17pm
Forum: Bikes & Bits – Technical section
Topic: Continental brakes - Wrong way round
Replies: 114
Views: 3615

Re: Continental brakes - Wrong way round

Brucey wrote:... depends on what your grip is like ...

cheers

Grip between tyre and road, that is. Nothing to do with how strong your hand is.

Takes me way back to school-days maths/physics problems on friction - "does it topple or slide?"
by Chris Jeggo
5 Oct 2018, 3:13pm
Forum: Bikes & Bits – Technical section
Topic: Is this probably a bent derailleur hanger?
Replies: 17
Views: 1080

Re: Is this probably a bent derailleur hanger?

I have a new frame and a 12-36t cassette + wheel from a setup that was working perfectly. When setting up the rear shifting, if I set it so it shifts from 12t-14t, then up at the 32t sprocket it's almost trying to shift to the 36t. If I set it up so the it is not trying to shift to the 36t from the...
by Chris Jeggo
2 Oct 2018, 10:40am
Forum: Bikes & Bits – Technical section
Topic: It's got to be the mech hanger, surely?
Replies: 7
Views: 400

Re: It's got to be the mech hanger, surely?

If you have an Allen key which is a good fit in the rear mech fixing screw then it also acts as an indicator of hanger alignment. If it looks right and if you have a good eye for angles then I would guess that is good enough, but that's just a guess - I don't know what the tolerance is. You say it i...
by Chris Jeggo
2 Oct 2018, 9:52am
Forum: Bikes & Bits – Technical section
Topic: Is this probably a bent derailleur hanger?
Replies: 17
Views: 1080

Re: Is this probably a bent derailleur hanger?

Some time last year I took a Shimano 9-sp 12-36 cassette out of my spares box to replace a worn out one, and after fitting it I found I had similar symptoms to those you describe. If the wire was adjusted to give good alignment on the 14 sprocket, the alignment was wrong by the time I had clicked ac...
by Chris Jeggo
30 Sep 2018, 12:02pm
Forum: Fun & Games
Topic: English Language - what "Does your head in" ??
Replies: 916
Views: 36510

Re: English Language - what "Does your head in" ??

"You're a peedant", said my son.

"It's pronounced peddant", I replied.

"See what I mean!"
by Chris Jeggo
24 Sep 2018, 6:08pm
Forum: Bikes & Bits – Technical section
Topic: What are those squiggly lines on old metal parts?
Replies: 9
Views: 1142

Re: What are those squiggly lines on old metal parts?

nigelnightmare wrote:TINWORM!!! :wink:

+1
Don't forget that Howard had a problem with stoneworm in 'Last of the Summer Wine'!
by Chris Jeggo
24 Sep 2018, 6:02pm
Forum: Bikes & Bits – Technical section
Topic: Outer rubber layer of tyre split
Replies: 7
Views: 338

Re: Outer rubber layer of tyre split

I would postpone patching the outside of the tyre for a while, so that you can keep a watch on whether the structure of the tyre is deteriorating. If the fabric is of a synthetic fibre such as nylon it is probably waterproof, and now we're past the equinox there's not so much need to worry about UV.
by Chris Jeggo
24 Sep 2018, 5:52pm
Forum: Bikes & Bits – Technical section
Topic: High end steel frames: are they worth it?
Replies: 106
Views: 10515

Re: High end steel frames: are they worth it?

I like my Paul Hewitt Cheviot SE touring bike with its Taiwan-built Reynolds 725 frame. My oldest bike is a custom Roberts 531 with Nervex Professional lugs so I prefer its looks, but there's nothing to choose between them so far as riding is concerned. My son has lived in Taiwan for around ten year...