Search found 192 matches

by Chris Jeggo
24 Oct 2018, 6:45pm
Forum: Bikes & Bits – Technical section
Topic: !965 moulton speedsix
Replies: 28
Views: 1487

Re: !965 moulton speedsix

Brucey Rear block 11-13-14-16-18-21-----60 on the TA chainwheel gear ratios are thus http://ritzelrechner.de/?GR=DERS&KB=60&RZ=11,14,13,16,18,21&UF=1320&TF=90&SL=2.6&UN=KMH&DV=gearInches 47.3, 55.1, 62.0, 70.9, 76.3, 90.2" -which is quite a lot different to those re...
by Chris Jeggo
21 Oct 2018, 4:00pm
Forum: Bikes & Bits – Technical section
Topic: Campag Skeleton caliper.
Replies: 21
Views: 978

Re: Campag Skeleton caliper.

+1
My Weinmanns have a QR on the lever. On another bike my Tektros do not, and I occasionally forget to reset. It's an age thing!
by Chris Jeggo
20 Oct 2018, 11:17am
Forum: Bikes & Bits – Technical section
Topic: !965 moulton speedsix
Replies: 28
Views: 1487

Re: !965 moulton speedsix

Those gear ratios in the 'Cycling' article can't be right. Using a spreadsheet, 90.1 / 83.6 = 1.07775 = 1 + 1/12.86, approximately 14/13! 83.6 / 77.7 = 1.07593 = 1 + 1/13.17, approximately 14/13 again! 77.7 / 68.0 = 1.14265 = 1 + 1/7.01 = 16/14 which is credible 68.0 / 60.4 = 1.12583 = 1 + 1/7.95 = ...
by Chris Jeggo
20 Oct 2018, 12:09am
Forum: Bikes & Bits – Technical section
Topic: Tinkling sound under drive from rear wheel
Replies: 53
Views: 2298

Re: Tinkling sound under drive from rear wheel

I've had noises from laced spokes in an old wheel, caused by slight grooves in the spokes due to fretting where they cross. You can detect this by squeezing adjacent spokes together near their crossing to see if they move smoothly or jerkily. I would have thought that what you did with cardboard squ...
by Chris Jeggo
19 Oct 2018, 11:58pm
Forum: Bikes & Bits – Technical section
Topic: Schwalbe Marathon Vs Marathon Plus tyres.
Replies: 28
Views: 6257

Re: Schwalbe Marathon Vs Marathon Plus tyres.

On the Schwalbe website you can compare their tyres using their 'blobs out of six' ratings for Rolling, Road Grip, Off-Road Grip, Protection and Service life.
by Chris Jeggo
15 Oct 2018, 2:15pm
Forum: Bikes & Bits – Technical section
Topic: saddlebag on carbon seatpost
Replies: 21
Views: 2242

Re: saddlebag on carbon seatpost

In one image you link to Bridge Street Saddlebag - seat post clamp.jpg the seat pillar appears to be a saddle cradle insert fixed in a plain tube. In this case, if the insert is a good fit and goes further down the tube (by a distance of several tube wall thicknesses) than the whole of the bag suppo...
by Chris Jeggo
14 Oct 2018, 2:29pm
Forum: Bikes & Bits – Technical section
Topic: Brake blocks for chrome rims.
Replies: 8
Views: 742

Re: Brake blocks for chrome rims.

I recall that chrome-plated rims are awful in the wet; they were more widely used in the 70s, when one piece of advice was to remove the chrome plating from the braking surfaces. Rusty rims stop you better than alloy ones. Also, at that time, you could buy chrome leather brake blocks, which were ano...
by Chris Jeggo
13 Oct 2018, 3:34pm
Forum: Bikes & Bits – Technical section
Topic: 32 or 36 spokes
Replies: 18
Views: 1203

Re: 32 or 36 spokes

+1 As it is a multiple of 16, 32 spokes may actually be stronger/more durable than 36 ... sounds more like numerology than physics or engineering to me. When I was a lad we had 32 front and 40 rear, a pattern of 4 repeated as often as required/desired, recognising that the loads on the front and rea...
by Chris Jeggo
11 Oct 2018, 1:47am
Forum: Bikes & Bits – Technical section
Topic: Is this probably a bent derailleur hanger?
Replies: 17
Views: 1077

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: 3597

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: 3597

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: 471

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: 3597

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: 2163

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: 3597

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 (...