ALL THE GEARS, NO IDEA
Q: At the beginning of the year I started a custom build project ending up in June with a 2005 Marin Attack Train Frame, full Shimano xt groupset and a nice set on Rockshox Revelation forks up front all for little over a £1000 (the wonders of eBay).
After a few summer rides the bike was spot on, then, a week ago whilst riding home I was on the biggest chainring (mega9) and biggest sprocket when the chain began trying to skip off the chainring down onto the middle ring.
I had a good look at the setup and found the front mech needed tightening up and aligning. I thought I’d cracked it. Oh no. Took the bike out and tried it out. As I put my weight through the crank the chain skipped again resulting in me over the handlebars, oh how my wife laughed.
Now, no how much tweaking with the gears (followed Shimano’s website to the letter of the law) I cannot seem to prevent it trying to skip. When I have the chain on the big sprocket and chainring and turn the crank backwards the chain skips down 4 sprockets, should this be common? I’m now starting to question whether the BB is the correct one.
Also, when I’m on the smallest chainring and smallest sprocket the chain runs over the plate which connects the outer plate of the front mech to the inner one, can this be correct as the mech cannot go any lower?
Next port of call is the local bike shop — is there something obvious
I am missing before I do?
Ian Smith, Washington
A: The obvious thing you are overlooking is your gear selection while riding!
Although your choice should always be long enough to allow you to select the biggest front with biggest rear gear, in reality you shouldn’t be trying to run this extreme gear, the same is true of the small front, small rear combo. The angled chainline created by trying to run these gears often causes the problems you are experiencing.
Accepted good practice dictates you should be running small front with the larger half of the rear cassette, middle front with every rear gear and finally large front with the smaller half of the rear cassette.
The gears placed “out of bounds” are duplicated elsewhere in the range so you still retain a full efficient range of gear ratios working on an optimised chainline and with decent chain tension, which, besides giving smoother operation, will extend the life of the drivetrain components.
If you really do feel a need to run the non-recommended gear ratios then every part of the drivetrain will have to be set up perfectly and be in pristine condition (you didn’t say whether your eBay bargains were new or used?) which is a job for a professional cycle mechanic, even then there is no guarantee smooth operating can be achieved.
Q: Hi, I am relatively new to mountain biking, I did dabble a number of years ago using an old GT Karakoram and a Marin Pine Mountain. After some time away and doing other things, just completed the UK Ironman. I have decided to get back on the trails.
After some searching and trials I purchased a Scott Scale 40 hardtail. I did read your input re the scale 30, but with a different stem it was the most comfortable bike I rode.
I should have probably asked these questions prior to buying, but I am not too concerned as all my riding friends use hardtails. Could you explain what all the tech terms are in relation to a 4” travel or 5” etc and 180mm of travel. I realise it is all in relation to suspension, but any chance of a simple explanation.
M. McNamara, Blackpool
A: Suspension travel for both forks and frames can be quoted in either old-fashioned inches or EU friendly millimetres and as it’s relatively easy to convert one to the other it doesn’t really matter which system a specific manufacturer chooses.
As to “what” this measurement refers to, well for suspension forks, it is the distance the fork lower (and wheel) is able to travel from being fully extended (unloaded) to fully compressed (loaded). This measurement is easy to take as the majority of today’s suspension forks are of a telescopic type where the fork lowers and wheel move in a straight line along the forks axis as the forks are compressed. Wheel movement and fork measurement are the same for a telescopic fork i.e. 1:1.
It’s on the rear that things get complicated, you can’t just measure the range of movement on the shock absorber, as the length of the attached levers i.e. linkages and swingarm greatly effect the amount of rear wheel travel that is achievable.
Each different frame design will allow the wheel to move along a “path” unique to that design.
While it is assumed the travel quoted by manufacturers relates to the amount of vertical wheel axle movement achieved from fully unloaded to fully compressed this is not always true. The axle of a wheel traveling along a rearward and upwards path may travel 8″ but the difference in its start and finish height may only be 6″. Complicated? Yep, that’s why some manufacturers quantify their travel measurements as a “vertical” movement or “axle” movement to help clarify the situation.
BIG BRAKE BODGE
Q: OK so I have been eating a few too many pies and the 160mm rotors that come as standard with Shimano disk brakes were not enough anymore.
Didn’t fancy the jump to 205mm especially as the forks wouldn’t take it so I ordered a 180mm rotor and a +20 adapter, then found the +20 adapters don’t work with the Shimano calipers as they are a funny shame.
This lead to a bit of a hissey fit on my part. Until along with I realised you can use the mount from the rear brake on the front to make a Shimano +20mm adapter.
And the bike shops said it couldn’t be done, so anyway, if anyone wants a +20mm adapter for a Shimano front disk you can do it using a Shimano Mount Adaptor Rear Post to IS 160mm
Chris Hughes, e-mail
A: I’ve been utilizing this little trick for years. I’m surprised more shops don’t use it as it’s not new and dates back to when the international standard for disc brake mounts was introduced. The norm then was to run a 20mm larger disc on the front forks, so fork “lug” standards and frame “mount” standards were set with this in mind.
Once you’re aware of the difference it doesn’t take a rocket scientist to work out the additional variations you can achieve by swapping front and rear callipers/adaptors.
Though do be aware there are exceptions to these fitting standards with certain forks and frames e.g. Fox 40s, Boxxers, Intense frames.
Q: I’ve recently bought a pair of new wheels for my bike. With my old wheels I used Nutrak Butyl Lightweight tubes (176g) and Panaracer Fire XC Pro tyres but the problem is I always got punctures. But every time I got a puncture I had to get my Dad to take my tires off to fix it because of my rims (Sun black eye rims) and my Dad struggled to get my tires off! So every time I got a puncture I had to wait for my dad to get home from work. So when I got my new wheels I started to use slime inner tubes (340g) which are great but they are a lot heavier so I don’t get the benefit of my new wheels. The problem with the nutrak tubes is they puncture and pop very easily so I couldn’t use those. Please can you recommend any tires or tubes which are light enough to benefit from my new wheels without getting punctures every day! Please help me to get out of my misery because I’m 13 and I have to got to school and do homework so I haven’t really got time to fix punctures! Thank you for your time I hope you can help me.
Will Leverton, email
A: The rim, tube, tyre combo you’re using shouldn’t be causing any problems, as they are all “pukka” parts.
You haven’t stated what “type” of recurring puncture you are getting — pinch flats or holed tubes from objects piercing through the tyre?
If it is “pinch” flats, make sure your tubes are inflated fully, also check the rim tape’s in good condition and if it is of the “plastic” variety that there are no sharp edges or better still replace with a good self adhesive type of tape (cloth or pvc). While you’re at it, inspect the rim’s valve hole for sharp edges and the same goes for the spoke ends and rim joint. If all seems OK turn your attention onto the tyre. Besides the usual feel inside for anything protruding through, carefully inspect the beading, sidewalls and main carcass for any tears or small holes, if you find any throw the tyre and replace with a new one.
If everything checks out but you still suffer from punctures then you’ll have to consider fitting a heavier i.e. thicker walled tyre to tube.
If you are trying to stop something sticking into a tube you need more rubber as a barrier.
If you are trying to stop a tube being “pinched” by the rim when hitting an object hard you need more rubber to cushion the blow. That’s why DH tyres and tubes are so heavy – not by choice but by necessity (although tubeless tyres partly addresses these issues!).
If you do decide to buy a different tyre — take along your wheel with you and make sure you are able to fit your new tyre onto the rim easily, preferably without tyre levers. At least that way you will not have to wait for your Dad to mend your punctures.
I have not recommended a specific tyre as the range is huge, you are better putting the staff at your local shop on the spot and asking them what they use, which of course will be relevant to local riding conditions.
KKEEP IT CLEAN
Q: I started MTB’ing last September and have ridden a fair few trails now but I am still pretty much clueless as to how and when to clean my bike? I’ve asked numerous riders and got answers varying from: “every time I go out” to “once it’s properly dirty”. I clean my bike after each ride with a hose and a brush but things such as degreasers/greases/lubes etc confuse me. Any chance you could give me a decent run down on how to clean my bike properly and what added extras I should be using?
A: Personally I prefer to clean the bike after every ride and whilst this has led to much mickey taking over the years from riding buddies (and MBR staff) the routine I have adopted has helped ensure the bikes I have been using work to their best possible ability and remain reliable.
Once you’ve decided to clean your bike there are two approaches, the “official” bucket of warm water, mild detergent and sponge method which although labour and time intensive it is “idiot” proof; OR the “frowned” upon power washer + strong cleaner method — when done correctly you can end up with a beautifully clean bike in less than 10 minutes which is why it is the preferred method of most pro teams. Unfortunately, incorrect application with the power washer can drive mud and water into places you don’t want it!
My own routine after a muddy ride is as follows:
1. Prop your muddy steed against a wall ensuring it is not likely to roll away, then using the power washer, not too close, blast off the worst of the dirt top to bottom before turning the bike round and doing the opposite side.
2. Using a specialist cleaner such as Muc Off, Dirt Attack, Hope’s Sh1t
Shifter, etc spray both sides of the bike with the cleaner and leave for a couple of minutes to soak in.
3. Next turn the bike upside down, this makes it easier to clean muck from the drivetrain and speeds up the wheel cleaning. Power wash both sides.
4. With the bike right way up again, give it a final spray down.
5. Bounce bike on it’s wheels a few times to shake off excess water before wheeling indoors to dry off. I normally leave mine to dry overnight.
6. Finally, it is time to re-lube your immaculately clean and dry bike – use a specialist chain lube. Don’t overdo it, little and often works best, then use a non-sticky thin Teflon type lube on front and rear derailleur pivots and for the real pro touch a little bit of silicon lube around your fork seals and rear shock seal.
In summary, wash the bike regularly before dirt gets baked on, don’t get too close to bearings with the power washer, let the specialist cleaners do the work, be careful not to over oil (and get lubes on discs) which will help cut down on having to use degreasers.
The end result of this whole routine is not just a clean and lubed bike, you will also have had the chance to make a visual inspection around your machine, hopefully, picking up on any potential problems or safety issues.