Can you give me some advice on my RockShox Tora 302 fork? I’ve had my Saracen Zen 2 (2006) for two years now with few complaints. However, on two occasions now, my forks have dropped from 130mm to 80/90 mm of travel. My local bike shop has stripped them and serviced them to try and find the problem, but they have been unable to find anything wrong. The forks are set up with the correct pressure, and the only issue I can think of is that the fork problem happened after a particularly hardcore weekend at Coed y
Brenin and a heavy day on Dartmoor .
Glenbob, Ivybridge, Dartmoor
The standard forks on the Saracen Zen 2 were Tora 302 Solo Air items, featuring a single Schrader valve fitting on the top of the LH leg, and a rebound-damping adjuster on the bottom of the RH leg. The drop in height from 130mm to
80-90mm that you describe will likely be due to a problem with the air seals on the LH leg.
Although it is easy to check how well the Schrader valve is sealing by filling the valve with water after inflation and checking for tell-tale bubbles, it is far more difficult to determine which of the remaining seals that seal both the positive and negative parts of the LH leg are causing a problem.
If the two instances where the forks have been a problem (on long rides) were not consecutive rides but interspersed with problem-free rides, than I would suggest the problem lies with the internal seals connected to the operation of the Solo Air function. In basic terms, what is probably happening is that air from the positive air chamber is leaking into the negative chamber, and this is making the forks squat into their travel.
Dirty seals, over/under-lubed seals or worn/damaged seals would cause a problem and the best approach with air seals is, if you are in any doubt, change them. You really do need to know what you are looking for when dealing with issues surrounding suspension forks or shocks and it is therefore a job best left to the experts.
BY THE BOOK
I’m quite new to mountain biking and I was wondering if anyone knows of a decent maintenance book for mountain bikes?
I’m after something that covers all the basic stuff but also goes into more detail.
There’s plenty of info out there to get all you budding mechanics started with your DIY maintenance. The four books that spring to mind, as they are firm favourites within the cycling trade are: Sutherlands Handbook for Bicycle Mechanics; Zinn and The Art of Mountainbike Maintenance; Park Big Blue Book of Bicycle Repair; and Barnetts.
All these are quite thorough, Sutherland’s book is well known as it is now in its seventh edition and has been going for 30 years. Park Tools’ book is useful and there is lots of additional information on the Park Tools website to supplement the info found in the book. Barnetts also produce an extremely good DVD. The Zinn book is probably the easiest one to start with, that’s not to say that it doesn’t cover things in detail, but it is an easier read.
As with most things these days, it’s easy to go online and have a brief look at what each has to offer. The online approach can also be good for checking out workshop manuals and how-to videos from most of the major component manufacturers.
If the bicycle maintenance bug really bites then the next step may be to enrol on a course organised by one of the better shops or via a training body such as ATG or Weldtite, both of which run accredited courses.
It doesn’t require a huge amount of skill to carry out basic bike maintenance, nor should it take up a great deal of your time, but it will greatly improve your whole mountain bike experience.
Just a quick question regarding front suspension forks on a hardtail mtb.
My Kona MuniMula came fitted with RockShox Judy T2 80mm-travel forks but I’d like to upgrade them to 100mm Marzocchi MX Pro remote LO. Will the 2cm difference upset the geometry and the handling of the bike, or will it be difficult to notice any change?
There’s no question it will change the geometry and handling of the bike, but will it be better, worse or just different? I can tell you how the bike geometry will change and what the corresponding handling traits will be, but only you are in a position to judge whether the change fits in with your own style of riding!
Normally a 20mm increase in suspension travel at the front doesn’t mean a 20mm increase in loaded ride height (static height — yes) because some of the difference is taken up in additional sag.
However, the difference in overall height between 80mm RockShox forks and 100mm Marzocchi forks is actually greater than 20mm, as the RockShox have some of the shortest axle to crown lengths for a given travel, and Marzocchi are generally the longest for a given amount of travel. So it’s likely your Kona will be riding 20mm higher at the front, 7-8mm higher at the bottom bracket, have a slightly longer wheelbase and a fractionally slacker head angle. At the risk of overstating the effect the changes will have, the result will be a slower-handling, less XC-race-type hardtail. Looked at positively, you’ll have a bike that’s more stable at speed and better for downhilling.
MINERAL V DOTS
I want to find out if anyone knows or has experience of using mineral oil in a brake system that was originally designed for Dot 4 or 5.1?
As I understand it, if you use Dot 4 or 5.1 in a system designed for mineral oil it will corrode the seals. But does this happen the other way round?
The reason I ask is that I have recently upgraded my front brake to a Hope Moto 6 and would like to have the rear lever to match. However, at the moment, funds do not allow me to buy the whole rear system, so I was thinking of buying the rear lever and combining it with my existing mineral oil-based hose and caliper. Trouble is the new lever says Dot 4 or 5.1 only!
It’s true that mixing Dot 4 or 5.1 fluids with other brake fluids is a bad idea, as the chemical involved (polyethylene glycol) can react violently with other braking fluids. Mineral brake fluid, although generally viewed as a lower-spec alternative due to its lower dry boiling point, does have the benefit of being less corrosive and generally less harmful to O-ring seals and to the environment.
Even though it may be safe to temporarily use mineral fluid in your new lever designated for use with DOT 4 or 5.1, you cannot just connect any lever onto a caliper and expect it to work correctly or, more importantly, safely.
The ratio of the amount of fluid displaced at the lever, to fluid amount displaced at the caliper is critical, as it is this which ensures that sufficient force is exerted onto the disc pads.
Designers spend months working on disc brake systems to ensure the brakes are reliable and safe. Throwing two different system halves together might create an interesting hybrid, but more likely it will create a Frankenstein brake system that never quite works right and might be in danger of failing at the most inappropriate moment!
Do yourself a favour and save up for a bit longer, then buy the rear brake system in its entirety, as it was designed to be used. This will also be a more cost-effective way to purchase the brake system, as opposed to buying it piecemeal.