Ask Pinkbike: Wide Rims, Coaching and Skipping Chains
Here at Pinkbike we get inundated with all kinds of questions, ranging from the basic "Can I have stickers" to more in-depth, soul searching types of queries like if you should pop the question or what to name your first child. Ask Pinkbike is an occasional column where we'll be hand picking and answering questions that have been keeping readers up at night, although we'll likely steer clear of those last two and keep it more tech oriented.
Wide Rims Worth it?
Question: Pinkbike user sevensixtwo asked this question in the 29er forum: I have a question about rim width on 29ers: I'm wondering if an upgrade from a rim with a 19mm inner cross section to one with a 24mm width be extremely noticeable? I currently ride 19mm internal width Easton EA90XC wheels, and my tires are all 2.2 - 2.35'' wide. I usually use Schwalbe's Racing Ralphs for cross-country racing and Nobby Nics for fun. Thanks!
 | The short answer is that yes, it will be noticeable, but only if you take the time to experiment with the slightly lower tire pressures that a wider rim allows you to use. This is because of the extra support the wider rim provides, and you should be able to drop 3 - 6 PSI depending on how you ride and your local terrain. This will make your bike feel more forgiving, almost like you're running just slightly softer suspension, and you'll also have more traction. Start by dropping 2 - 3 PSI and continue until the tires begin to feel vague in the corners from casing roll, then go back until that feeling goes away. Also, watch for burping. - Mike Levy |
A wider rim provides more support for the tire, allowing you to run less air pressure for more traction. On the flip side, it adds volume to tires, so cross-country racers could use a skinnier, lighter tire without the usual drawbacks..
Chain Skips on the Smallest Cog
Question: Tfree asks in the All Mountain and Cross-Country Forum: So, I took my one-by-nine setup off of one frame and installed in on a Stumpjumper frame that I am looking to sell. I tuned the derailleur, and when it is in the smallest cog, the chain skips - even with hand pressure on the pedals. I never had this problem when it was on my other frame. It rides smoothly and shifts great in all other cogs but the smallest skips like crazy. Any help would be great!
| I assume that you know how to tune a rear mech, so I won't bother with the proper chain wrap speech. Normally, an 11 or a 12-tooth cog skips under load when either the sprocket teeth or the chain are worn beyond their service lives. The slight mismatch between the length of the chain and the width between sprocket teeth compounds until the chain jumps a tooth and then the process repeats. Unless you replace your chains often, both the chain and cassette tend to wear evenly, so skipping is rare unless a new chain is installed on a worn cassette. I read in a following post that you used the same chain on the new bike, which should have produced the same skip free performance as before - unless you flipped your chain upside down, which would make it behave like a fresh chain and skip like mad. Try flipping it around. and if that doesn't work, the culprit may be that your Specialized's chain line is too far inboard and you may have to space the chainring or the crank axle outwards three or four millimeters to get the chain to run smoothly over the outboard cassette cogs. - RC |
The rear derailleur setup in this photo provides the maximum amount of chain wrap, so if the chain skips over the small cog under load, the culprit is probably a worn chain or cog. In rare cases, a bent hanger or a bad chain line can cause similar symptoms.
Skills Coaching
Question: Pinkbike user AlanP asked this question in the All Mountain, Enduro & Cross-Country Forum: Hi, can anybody recommend any skills courses at intermediate/advanced level? I'm looking to improve and gain confidence in jumps, drops, speed, flow. I'm happy with most black trails at trail centers, but less confident when things get a bit gnarly and I lack confidence to use speed in gravity enduro racing.
| Well, considering your location in Birmingham, current riding level, goals and the enduro racing aspect, there's a brace of local options: Choose from The Bike School or Neil Donoghue Coaching. The Bike School offers courses at Cannock Chase and Sandwell Valley as well as as guided trips out to Snowdon in Wales. They use three different instructors including Adam Halling who has been exploring the Chase for years, who is also an Elite level enduro racer and fitness trainer, so don't bother trying to out-sprint him. They offer varying types of course but a specific "Jumps and Drops" course is available. A 3-hour course runs between 10am and 1pm for 35GBP with a maximum group size of 6, so you can get all the help you need directly from the coach. If you want provenance, Neil Donoghue is an ex-World Cup downhill racer, now spending his time as a fully qualified coach who still races enduro at the highest level. Two time UK Gravity Enduro champion and all round nice guy. A little further afield, Neil is based in Shrewsbury and offers skills courses and guiding at Eastridge and Coed Llandegla (as well as some more exotic locations), and also offers a specific "Jumps and Drops course". A full days coaching starts from 110GBP, and includes a video analysis, food/drinks and a USB stick with all your pictures and videos from the day to take home. - Paul Aston |
He's called 'The Don' for a reason. World Cup riding speeds, coaching skills and the ability to transform your riding.
Have some unresolved tech questions? Jump in the Pinkbike Forum and we'll look to answer it for next time.
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Member since Jul 22, 2013
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But the clue to the skipping was actually in the question...
"I tuned the derailleur, and when it is in the smallest cog, the chain skips - even with hand pressure on the pedals. I never had this problem when it was on my other frame"
The derailleur clearly was not tuned PROPERLY.
Sorry to puncture anyone's veil of infallability, I can however speak from personal experience of having an old chain skip on the smallest cog of a new rear cassette. Wipperman chain, new SRAM 9 speed cassette. The chain had been running on another frame on another rear wheel with an identical SRAM cassette. I didn't have a new chain at hand, so used the old one. And 9th gear slipped under load. Constantly.
I retuned the derailleur (properly deeight!!) numerous times that day but could not eliminate the problem until I suspected the problem lay in the "old chain, new cassette" perennial problem, so replaced the chain.
You might be interested to know that the derailleur needed no retuning after replacing the chain for it to run perfectly.
Must have been magic then.
It shouldn't really affect chain wear, at least to my knowledge, though.
I know im not explaining myself properly
As to evening out bushing wear on chain pins... that was all fine and dandy decades ago when chains all used bushings between the pins and rollers, but shimano and everyone else have long since abandoned that form of chain construction for multi-speed chains. Eliminating seperate bushings saved weight, simplified construction (thus cheaper to produce/sell) and improved strength. They wear faster though but with wide cassettes ranges and weird chainlines, the lateral strength ends up being more important.