APB Front Suspension

David Squires writes:

The following text was taken from a previous version of the website which was managed for many years by Mike Hessey.  It has been pointed out that, in the light of subsequent revisions by Pashley and the Moulton Bicycle Company, it is now obsolete.  A more up to date proceedure can be found here.   Updated versions may be available from the Moulton Bicycle Company and members are encouraged to check on their website to see if this is so.

Mike Hessey wrote:

My APB is a relatively early model, fitted with a rather hard front spring, which is not ideally suited to my normal usage, the vast majority of which is on roads, with occasional excursions onto canal towpaths, old railway tracks, bridleways etc. A few months ago an APB road spring was mentioned in The Moultoneer, and I subsequently bought one from the Pashley stand at Folder Forum 2 in May. Currently the factory only offers this road spring for the front, and a standard rear suspension unit - perhaps this makes the harder front spring which I removed a valuable item! I hadn't done anything about fitting the new spring until now because the APB had had a front end overhaul only 12 months before, and I thought I would wait until another strip-down before fitting the new spring. In the normal course of events that would have meant waiting at least another year, but as a technical article on APBs was needed, I was persuaded to do the job now (2nd October 1997).

Fitting a new spring in the APB involves much the same steps as replacing the Nylatron® cylinder at the base of the spring. This is a component that has been known to jam on occasion (though not on my APB), so the information that follows may also be of use to those tackling replacement of that cylinder. I had the corresponding cylinder jam on my AM7 (after about 7 years, so this is not a frequent or serious problem) and had replaced it myself, with a little help from my friends. Consequently, although this was not a job I had done on the APB before, I felt it was something I could tackle. If you are in doubt yourself, you should get a competent person (eg dealer) to do the job for you. The information which follows tells you how I did the job on my bike - it is in no sense to be taken as a recommendation that anyone else should do the job themselves, nor is it suggested that this is the way it should be done. If the information is useful, all well and good, but don't blame me for any consequences if you decide to do it yourself, whether you do the job in the way that I did or not.

1. The first job was to find a suitable space in which to work. I don't have any workshop stand, so I needed to be able to lie the bike on its side and work around it.

2. Next I assembled the tools I expected to need. This was rather a guess; spanners and allen keys. I also used a small mallet and a long thin rod, the purpose of which will be described later. The small allen key was only used in disconnecting the brake cable.

3. Like most jobs on a bike, this can be a bit messy, so it's a good idea to put on old clothes. I omitted to do this, and spoilt a favourite shirt!

4. The next task was a quick wipe down of the front end of the bike to remove any surface dirt and grease - even wearing old clothes it's more pleasant to avoid getting unnecessarily dirty.

5. Now the brake cable was detached at the callipers so that the forks could be removed later, and the front wheel was removed.

6. Although I didn't do so on this occasion, I sometimes use a sketch pad and/or Polaroid [digital these days!] camera to record what I'm doing, so that reassembly won't present problems later.

7. The suspension links were now removed on both sides - three nuts on each side.

8. As the parts were removed they were carefully placed on plates so as to help remember the configuration for later assembly. Avoid misplacing any of the washers at this stage, either on the securing nuts or even more importantly on the links themselves. If you have a non-cycling partner, it may be better to use some other type of receptacle in or on which to store the parts!

9. The front forks now slid out of the steerer tube/head tube without any problem. However, the ball joint at the top pulled out of the Nylatron® cylinder between it and the spring, leaving the cylinder in the head tube. If the cylinder comes out with the forks, life is much easier, as the spring is then free to come out too. I suspect that more often than not the cylinder stays in place. If the reason for doing the work had been a jammed front suspension, then the cylinder would certainly have stayed in the tube. When the job is being done to free jammed suspension, I am told that if the cylinder doesn't just drop out, the best thing to do is drill a small hole in it, put in a self tapping screw, and then pull it out with the screw. However, this of course destroys the cylinder. and if it was not faulty and you are merely replacing the spring, this is rather a waste. So I removed the handlebars and used a long thin rod (it needs to be thin to pass the upper locator for the spring) to push the cylinder out from above. A firm push was needed, but no real force. When replacing the cylinder on my AM 7 some years ago I used this approach, and much more force, to remove the cylinder. However, the experts do not recommend this as it risks damaging the inside of the head tube by applying force with the rod.

10. Once the cylinder was removed, the spring simply dropped out.

11. I took the opportunity to clean the bottom end of the head tube. Lubrication is NOT recommended as it can cause the cylinder to expand and jam, but I did apply a little molybdenum grease, which I had been told in the past is safe, to lubricate the tube and reduce the risk of corrosion. [Editor's note: The factory currently recommend only a sparing application of lithium grease if protection from corrosion is required, and NO other alternatives.]

12. The forks and links were cleaned fairly thoroughly, as it was easy to get at parts which are normally rather inaccessible on the bike, and the links were lightly greased. The handlebars were refitted.

13. The new spring and cylinder, followed by the forks, were slid back into the tube, making sure the ball joint correctly located on the cylinder.

14. The links were replaced. making sure they went back exactly as removed (nuts on the outside, the two closer-spaced bolts at the front). The spring needed to be compressed slightly - rather awkward while fitting the links, but made easier by pushing the handlebars against a wall.

15. The front wheel was put back and the brake cable was reconnected. The operation of the suspension was checked, and the setting of the nuts on the links was adjusted to give the required degree of damping (as per normal practice).

16. The ride height was checked, so that the front links were more or less horizontal with the rider on the bike in the normal riding position, as per normal practice.

The job took about 2 - 3 hours, but I had no instructions to work from, and I did unnecessarily dismantle a couple of parts. I reckon that, even without the benefit of both a workstand and ideal working conditions, it should be possible to complete the job in 1 - 1.5 hours. If I need to do it again, I shall have these notes to work from, and I will be able to check that estimate.

And the effect on the ride? I would describe the change as quite a subtle one. The suspension is still significantly harder than on the AM (not necessarily a bad thing in my view), but it is also noticeably smoother than with the original spring.

Related Pages

F-Frame Front Suspension

F-Frame Rear Suspension

Gear Ranges on current Moulton Bicycles

Sturmey Archer FW Hubs

TSR 30 Front Suspension

APB Front Suspension

APB Rear Suspension