Search found 984 matches

by BigG
2 Jun 2017, 9:13pm
Forum: Bikes & Bits – Technical section
Topic: Chain jams
Replies: 17
Views: 4722

Re: Chain jams

Mick F is right. Those of us who do not have indexed front mechs always ease off the pressure and seldom have trouble. I have a 26 tooth drop (46 to 19 in a half-step and granny system) and have fitted a JumpStop as a precaution . The build up of dirt on this suggests that it is seldom if ever broug...
by BigG
7 May 2017, 9:26pm
Forum: Bikes & Bits – Technical section
Topic: Chain tool can't relieve tension?
Replies: 13
Views: 869

Re: Chain tool can't relieve tension?

Brucey's Cyclo must be newer than mine. Mine is exactly like the original photo but dates back to the 1950s. Definitely a Cyclo.
by BigG
6 May 2017, 7:36pm
Forum: Bikes & Bits – Technical section
Topic: Chain tool can't relieve tension?
Replies: 13
Views: 869

Re: Chain tool can't relieve tension?

The tool looks like a standard Cyclo chain rivet extractor. It is complete although the two prongs need to be straightened. They are only aluminuium alloy so a robust pair of pliers should do the job. The technique is to screw the pin down with the two ends placed roughly in position on the prongs a...
by BigG
31 Mar 2017, 7:57pm
Forum: Bikes & Bits – Technical section
Topic: 6 speed 14-47 tooth sprockets
Replies: 22
Views: 975

Re: 6 speed 14-47 tooth sprockets

I have a 14/40 freewheel using a standard 14-17-21-26-32 5 speed unit onto which I have bolted a 40T Cyclotouriste inner chainring. This works fine with very even gear spacing. Drilling the big sprocket to take the 40T ring is beyond the capacity of a normal DIY drill. The hardened steel needed the ...
by BigG
10 Mar 2017, 5:47pm
Forum: Bikes & Bits – Technical section
Topic: Derailleur Cage Tabs
Replies: 56
Views: 3099

Re: Derailleur Cage Tabs

I suspect that the change that has caused the introduction of the tabs is the combination of the widening tooth gaps on the chainwheel and the longer arm rear mechs. A sudden shift 15 or more teeth onto the small ring can cause the chain briefly to become completely slack on the bottom run. It is th...
by BigG
26 Feb 2017, 11:15pm
Forum: Bikes & Bits – Technical section
Topic: SICK OF IT - GEARS AND THINGS
Replies: 82
Views: 3252

Re: SICK OF IT - GEARS AND THINGS

BTW how are the pivots on the Duopar holding up? I have worn out three so far but still have a spare. It was always worn pivots and an increasingly non-vertical pulley cage that caused the replacement. Age is severely limiting my mileage now and I have two other bikes to choose from. The Duopar wou...
by BigG
26 Feb 2017, 10:42am
Forum: Bikes & Bits – Technical section
Topic: SICK OF IT - GEARS AND THINGS
Replies: 82
Views: 3252

Re: SICK OF IT - GEARS AND THINGS

I like 3x5! - nice wide cog spacing, plenty enough of ratios for me, etc. Of course unavailable I guess on freehubs, so stop reading now! I still ride a 5 x 3: for many years this was a 51-46-28 or 24 compact triple with a 14-17-21-26-34 freewheel. I have recently widened it a little to a 50-44-22 ...
by BigG
13 Jan 2017, 8:47pm
Forum: Bikes & Bits – Technical section
Topic: Gears in "Feet Travelled" (Excel Chart)
Replies: 60
Views: 3305

Re: Gears in "Feet Travelled" (Excel Chart)

Brucey is right to say that a 5'' crank with a 50" gear should give the same gear ratio as a 7" crank with a 70" gear. It does. However, it will not feel the same as our physiology gives us a fairly narrow preferred crank length that has everything to do with leg length and joint flex...
by BigG
10 Jan 2017, 9:51am
Forum: Bikes & Bits – Technical section
Topic: Gears in "Feet Travelled" (Excel Chart)
Replies: 60
Views: 3305

Re: Gears in "Feet Travelled" (Excel Chart)

If we are going to change from our traditional "effective wheel diameter" measure which our normal gear inches describes, then the best alternative is surely the true gear ratio; i.e. the ratio between the distance travelled by the bike along the road divided by the distance travelled by t...
by BigG
19 Dec 2016, 7:59pm
Forum: Bikes & Bits – Technical section
Topic: Chainset/Cassette Replacement.
Replies: 15
Views: 1262

Re: Chainset/Cassette Replacement.

Do you really need a 52 tooth ring? 52/11 gives top gear of 128" with 27" wheels. This is Mark Cavendish territory. Most would find 44/11 plenty high enough and even 40/11 (98") is fairly high for touring.
by BigG
9 Dec 2016, 9:27pm
Forum: Bikes & Bits – Technical section
Topic: Small Sprocket Wear Rates
Replies: 27
Views: 2801

Re: Small Sprocket Wear Rates

In reply to MickF's query regarding the effect of wheel size, I would guess that the lower chain tension with a small wheel (for the same force at the rim) is more or less countered by the higher chain speed with the smaller wheel. The net effect on wear is probably small. I have only limited experi...
by BigG
13 Oct 2016, 10:13pm
Forum: Bikes & Bits – Technical section
Topic: SRAM chainrings
Replies: 16
Views: 931

Re: SRAM chainrings

What happens at the rear sprockets as no effect on the chainring/chain relationship. Just visualise what happens if the chain just dangles loose from the chainring as you turn this. Double or triple chainsets are of course impossible to keep aligned.
by BigG
4 Oct 2016, 9:13am
Forum: Does anyone know … ?
Topic: Tyres
Replies: 11
Views: 844

Re: Tyres

I would have thought that a 38 mm wide tyre was rather narrow for a 24 mm internal width rim, though certainly not too narrow. A range of tyre widths between about 1.5 times internal rim width and 2.25 times IRW was traditionally considered appropriate for road tyres, but mtb tyres can sometimes be ...
by BigG
24 Sep 2016, 1:28pm
Forum: Bikes & Bits – Technical section
Topic: Broken KMC Link
Replies: 40
Views: 2287

Re: Broken KMC Link

Nice to see Erudin measuring his chains by hanging them. I have found this the only reliable guide. The Shimano chain with an extension of about half a link over 108 (or 100) is just about at the end of its useful life. IMO 0.5% extension limit allows the chain to be the expendable item while greatl...
by BigG
24 Sep 2016, 1:14pm
Forum: Does anyone know … ?
Topic: or recognise this CX frame and forks?
Replies: 6
Views: 824

Re: or recognise this CX frame and forks?

My old Simplex gear lever bosses were tapped for 3/16" Whitworth as Simplex, Cyclo Benelux and Huret levers sold in the UK all used this thread then. The 1.5 turns on an M5 bolt would suggest this.