Letter of consent
I’ve just bought some Marzocchi XC600 forks, which use a Post mount. Until now I’ve been running IS mounts, so
I’m confused as to how to space the caliper. I’ve got Avid Juicy brakes with 185mm rotors. Do I need a spacer or something?
Al, email

XC600s feature a Post mount fitting that allows for the direct fitting of a Post mount caliper onto the cast leg when paired to a 6in disc. This is the norm for most of the current single-crown suspension forks. If you want to run a disc larger than 6in then you do have to use the appropriate adapter for your chosen disc size. Avid’s own adapters are reasonably priced at £7.99, and very easy to fit.
Now here’s the bad news — Marzocchi recommends the 2006 XC600 only be used with a 6 or 7in disc, and if you’re on the latest 2008 forks then the manual states 6in disc only! Either way, your 185mm disc equates to a 7.25in, exceeding the maximum recommended size for this model of fork. Although it’s unlikely, this slight increase in disc size could potentially stress the fork to a point where the casting fails. For this reason you will invalidate your warranty unless you can get written authorisation from Marzocchi approving the use of your larger- than-recommended disc rotor.

Tyred and deflated
I switched to tubeless at the beginning of the summer, and up till last weekend I’ve found it really good. I’ve been running Maxxis High Rollers with sealant, and once I got them seated (is there any easier way than pumping like a lunatic?), they worked like a charm.
However, last weekend I was out riding and got a thorn or something through the tyre. The next thing I know it’s hissing and no matter what I did, it wouldn’t seal. Being a well-prepared sort, I had a spare tube with me, so I put that in, pumped it up and rode away — for about 15 metres, when all the other thorns that had accumulated in the tyre after a summer of riding punctured the tube. After wearily trudging three miles home, I took the tyre off and counted at least 10 bits of debris poking through the rubber. So, if you were in my situation, what would you do to get home riding?
Andy, Matlock

Whether on tubeless or tubed set-up, if you get a puncture, good practice dictates that you thoroughly check the tyre and wheel to remove any possible causes of a further puncture. If the inside of your tubeless tyre is looking like a pin-cushion, then simply fitting a tube into an unchecked tyre won’t get you very far, as you’ve already discovered! The other alternative is to locate the leak that the sealant appears to be unable to cope with and repair the offending area. How do you do this?
Well, there are two approaches; the first is to patch the inside of the tyre in a similar way to that of patching an inner tube, but using glue and patches specifically designed for a tubeless tyre carcass.
The second method is to plug the hole in the tyre using specially designed strips. This is my preferred option as it has been used in the automotive/motorcycle trade for many years and provides a
permanent fix solution.
Once you have got the hang of what to do, it is no more complicated than fixing a standard inner tube. The quickest way to inflate and seat a tubeless tyre is to use a compressor, obviously not very CamelBak friendly. CO2 cartridges are a good alternative. If you don’t have these available, only a normal mini pump, then the trick is to make the tyre-rim interface slippy, so that the tyre can start to slide into place easier.
Also, make sure both sides of the tyre beads are pushed into the ‘well’ of the rim prior to starting inflation — then pump like a lunatic!

True knowledge

My front wheel has got a bit of a kink in it, maybe three to four millimetres at worst. I’m pretty sure it’s been caused by riding, rather than just spokes losing tension as they’ve bedded in. I haven’t trued wheels for years, so I’ve been avoiding truing these for the past month or so. I run discs so I’m not getting any brake rub; I just wondered, is there any real performance advantage to me getting rid of this wobble? Will the wheel be significantly stronger if it’s straight, or will messing around with spoke tension cause more trouble than it will solve?
Stu, email

The combination of rough terrain and wide-carcass tyres found in mountain biking sets limits to the performance benefits of having perfectly true wheels.
The small drop in performance is there; after all you can’t cheat the laws of physics, it’s just that the mountain bike set-up masks the effect. Also, bear in mind many tyres display run-out of more than 3-4mm, even when seated correctly. What is of more concern for the mountain biker is wheel strength and reliability — most people can appreciate that a wheel loses a good portion of its strength when a spoke breaks, as this causes an uneven distribution of the loads placed on the wheel.
The same situation occurs with incorrectly or unevenly-tensioned spokes; a kinked wheel will have undoubtedly altered the tension on the spokes and consequently affected the wheel’s overall strength. A good wheel builder adjusts both trueness and tension in equal measures.
Although many home mechanics are able to true-up a wheel to remove lateral movement, most struggle with removing radial movement and nearly all fail to get a wheel accurately tensioned. For this reason, it’s best to get your wheels checked out by a professional.

A clean machine
As a relative newcomer to mtb’ing,
I am glad to take on board any help regarding the maintenance and up-keep of my trusty old heap. Mates laughed at the lack of attention I used to give my full-sus, so now I take great pride in cleaning/maintaining it (besides, the wife won’t let me get a new one till I can look after this one). But now I’m worried I might have overdone it. My newly-gleaming rear cassette makes a horrible noise whilst freewheeling, so, my question is: can you over-clean and not be able to get oils back into places washed out?
Robbie, Southampton.

I clean all my own bikes after every ride, as I detest having to do a post or pre-ride inspection and lube on a dirty bike. So no I don’t think you can over-clean a bike — but you could well be cleaning it incorrectly or too aggressively.
Look at this logically; if you start every ride with a clean, dry and freshly lubed bike, you will know:
What condition your components are in, as you will have been able to carry out a visual inspection
That moving parts will be moving freely and smoothly
That the dirt/mud/grit from the previous ride will not be grinding away your components
However, if you don’t clean your bike regularly, the reverse is true:
You won’t notice if grit is wearing the coating off the stanchions of your forks, or maybe what looks like a crack is starting to appear around the head tube
Gears will be stiff, and once they have shifted-up they will fail to drop down one unless you do a ‘down two and up one’ shift
Chainsuck on your new Race Face/Shimano chainset will drive you nuts, and that middle ring will soon be looking worn

The little-and-often approach works better than the big effort once a month. I must stress the importance of being careful when using a high-pressure water jet around bearings and bushings. At the risk of stating the obvious, the aim is to drive dirt off the components, not into them. Additional care should be taken when using strong degreasers or aggressive cleaning liquids, not to let them run into bearing housings, or you’re likely to get a horrible noise while freewheeling!
If this does happen, wait till the component has dried out, then depending on what it is, either strip and regrease or drip lubricant into the component.