Search found 984 matches

by BigG
9 Sep 2016, 10:24pm
Forum: Bikes & Bits – Technical section
Topic: Which 9 speed mechs for top touring performance?
Replies: 27
Views: 1687

Re: Which 9 speed mechs for top touring performance?

I am surprised that no-one has recommended the older Shimano XT 761 SGS rear mech (pre shadow). This is excellent quality and will comfortably take a 45 tooth range and a rear sprocket up to about 40 teeth depending on the exact length of the rear drop-out. It also has a cable adjuster built in - I ...
by BigG
9 Sep 2016, 10:14pm
Forum: Bikes & Bits – Technical section
Topic: Old TA chainset
Replies: 17
Views: 996

Re: Old TA chainset

The old ProV1s chainsets popularised by TA and Stronglight (49A and 49D) were also made by Shimano (original Dyna Drive tourist) and Sugino. They were very flexible in that they allowed inner rings down to 25 tooth and big rings up to 60+. The difference between the double and the triple was simply ...
by BigG
24 Jul 2016, 8:32pm
Forum: Does anyone know … ?
Topic: How slow can your lowest gear go?
Replies: 40
Views: 2305

Re: How slow can your lowest gear go?

I find it just about possible to ride a reasonably straight line at 2 mph. A straight line is necessary in Devon as high banks, narrow roads and passing traffic make anything else decidedly unsafe. And by the way, keeping straight while climbing a steep hill under full power is much harder than doin...
by BigG
14 Jul 2016, 11:01pm
Forum: Bikes & Bits – Technical section
Topic: how to change 12-36T cassette to 12-40T?
Replies: 21
Views: 1112

Re: how to change 12-36T cassette to 12-40T?

The best (IMO) way of accommodating the extra large sprocket is to abandon the smallest one rather than one of the more useful ones in the middle. Taking off the two smallest and replacing them with a 13 or 14 tooth outer sprocket (available on ebay and no doubt elsewhere) gives space simply to add ...
by BigG
5 May 2016, 5:55pm
Forum: Does anyone know … ?
Topic: Alternatives to a triple
Replies: 79
Views: 5264

Re: Alternatives to a triple

I have never found changing down from the middle to the small ring a problem. Only a brief relaxation of pedal pressure is required (less than half a revolution) and the change is effectively instant. My bigger problem has always been the change up from the small ring which always occurs while I am ...
by BigG
25 Apr 2016, 8:15pm
Forum: Bikes & Bits – Technical section
Topic: What width tyre?
Replies: 4
Views: 352

Re: What width tyre?

The charts above raise the question "Why so few good 15 and 17 mm rims?" I was lucky enough to find some Sun 16 mm rims a few years back. These will cope comfortably with any tyres I choose to use from 25 mm to 35 mm.
by BigG
23 Apr 2016, 7:44pm
Forum: Does anyone know … ?
Topic: Calculating gears.
Replies: 13
Views: 1099

Re: Calculating gears.

58/39 is not a particularly big jump for a road mech. Using this with a modern double road mech should give you no problems unless you have a very shallow angled downtube on which the mech is mounted. I have used up to 27 tooth jumps on a half step and granny combination (31 tooth overall with a 48 ...
by BigG
31 Mar 2016, 8:22pm
Forum: Bikes & Bits – Technical section
Topic: Front changer for small chainrings.
Replies: 20
Views: 961

Re: Front changer for small chainrings.

The 1 mm clearance for the large ring is unnecessarily small. I was always taught that 2 mm was about optimum and my exprerience is that up to 4mm causes few problems. The extra 2-3 mm may solve the riginal problem. I have in the past found that the clearance from the inner plate of the front mech o...
by BigG
31 Mar 2016, 8:15pm
Forum: Bikes & Bits – Technical section
Topic: Upshift and downshift?
Replies: 32
Views: 1066

Re: Upshift and downshift?

I wonder what Manc33 would mean by changing "UP" on the front mech. Changing up surely means changing into a higher gear - I cannot recall anyone ever using a different meaning in normal conversation.
by BigG
21 Mar 2016, 8:19pm
Forum: Bikes & Bits – Technical section
Topic: spot the obvious mistake....
Replies: 14
Views: 999

Re: spot the obvious mistake....

I think they can work well but - over time the cable can fatigue when it is wrapped round any pulley The only points of possible fatigue are where the cable first contacts the pulley and where it exits from the pulley. At all other points it does not flex at all. This is no different to the entry a...
by BigG
5 Mar 2016, 3:57pm
Forum: Bikes & Bits – Technical section
Topic: Bottom bracket (ST) woes/weirdness?
Replies: 3
Views: 380

Re: Bottom bracket (ST) woes/weirdness?

I have had the same experience. I bought an Evans touring frame for my son some 20 years or more ago. He subsequently built it into a decent bike using among other things a Shimano UN52 bb axle. Many years later, he mentioned to me that his bottom bracket cups had an annoying habit of loosening from...
by BigG
5 Mar 2016, 12:51pm
Forum: Bikes & Bits – Technical section
Topic: Another chain length question...
Replies: 13
Views: 612

Re: Another chain length question...

With almost any practical triple, the small/small combination is an unnecessary duplicate, and even with extreme gear ranges (60 tooth total on the bike shown) the chain may not go slack. There is of course some rub chain on chain, the chain line is pretty awful and the chain wrap on the small sproc...
by BigG
2 Mar 2016, 5:28pm
Forum: Does anyone know … ?
Topic: Rear mech . . . 9sp down to 7
Replies: 6
Views: 497

Re: Rear mech . . . 9sp down to 7

9 speed Shimano mechs work perfectly well with 5, 6, 7, 8 or 9 speed freewheels or cassettes. 9 speed cassettes require narrow 9 speed chains, but all the rest work perfectly well with modern 7/8 speed chains. Seeking out old 3/32" chains for the wide 5 and 6 speed freewheels is not necessary -...
by BigG
29 Feb 2016, 7:25pm
Forum: Bikes & Bits – Technical section
Topic: Chain Catcher
Replies: 69
Views: 51234

Re: Chain catcher

If it wears away quickly, then you have a front mech adjustment issue. It should only be needed rarely. I have used Jump-stop devices for many years with some very large drops from middle to small ring - up to 26 teeth. Judging from the dirt on the Jump-stop, it has seldom been used. Prior to using ...
by BigG
27 Feb 2016, 8:39pm
Forum: Bikes & Bits – Technical section
Topic: Fat vs Thin.... an accidental experiment
Replies: 45
Views: 2116

Re: Fat vs Thin.... an accidental experiment

Isn't contact area inversely proportional to pressure for any given load regardless of tyre size (width and diameter)? Area x pressure = load give or take a small amount for the stiffness of the carcass.