Fitting dropper posts

This weekend I fitted two dropper posts.  One was the old Rockshox Reverb that Roy and I had serviced a couple of months ago, fitted to Roy's Whyte. The other was a new Rockshox Reverb Stealth (B1) fitted to my Giant Stance.

Internal Hose Routing

There are plenty of videos showing how to fit dropper posts, so I'm not going to repeat those excellent tutorials, however, what many of them assume is that you are replacing an existing dropper.
https://www.youtube.com/watch?v=f1__XVOjkvo
https://www.youtube.com/watch?v=4Ei6GlmPlAo

I was threading a hose through the frame of a bike that had not had a dropper before. That makes getting the hose in place a whole lot more difficult. The reason I chose the Rockshox over other makes was because, apparently, the hydraulic solution is more tolerant of tight bends. I'm glad I did.

I thought I might be able to use the cable threading fishing tape and rods, that I already have, to get the hose in without removing the bottom bracket from the frame. I was wrong, the local bike shop was right! I had to remove the bottom bracket.

The bottom bracket is a SRAM DUB pressfit and I found a couple of videos showing how to remove and install similar.
https://www.youtube.com/watch?v=yOJAKBQOU9U
https://www.youtube.com/watch?v=E0CDaxwbd5c

Luckily, one of the many articles I looked at mentioned to watch out for the spacer (4.5mm) on the right hand, chain-ring, side. It would have been very easy to miss that. It just pulls off or drops off while you are not looking and rolls under the work bench!

I was glad I had bought a drifting tool designed to remove push fit bottom brackets. Without that I don't think there was any chance I would have got the job done. I only bought a budget tool from Amazon. It needed the splines bent out a fraction but worked fine. I needed to use a lot more force than I was comfortable with but the job needed to be done.

I'm pretty sure that drifting out the bearing housing from the frame is very likely to have misshapen the bearings. They still run, just, but if I was doing it again, I would have bought a new bottom bracket, rather than re-use the one I took out. A new bottom bracket is on order.

Tips: The right hand end of the inner sleeve of the SRAM dub pressfit bracket is fixed to the bearing cup. The left hand cup slides along the tube with a fine washer to seal the gap. That allows the same component to be used for both 89.5mm and 92mm shell widths. (SRAM part number 00.6418.016.000) With the SRAM dub pressfit, it is only necessary to remove the RIGHT hand, chain ring, bearing, along with the inner sleeve, to be able to thread the dropper hose.

I wasted a fair bit of time trying to fish through the frame. Once I had the bottom bracket out, I could see that was never going to work.

There are flanges, lips, where the tubes join. It was hard enough getting past the flanges when I could fish in there from both ends.

With the hose routed, the rest of the jobs were relatively easy. The bearing press I had ordered had not arrived, so I used a long M14 bolt with some big washers, which I had to hand.

It needed some care to ensure it was pushing in straight but the nuts, bolt and washers, worked perfectly as a bearing press.

Everything else was as per the SRAM video.

Sanding the inside of the top tube, using friction paste, torquing up the saddle stem, adjusting the length of the hose for the handlebar remote and fitting the remote.

Not forgetting to slide on the grommet before attaching the remote.

Finally fitting the saddle. By which time it was late and very dark, so I test rode it the following day.

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External Hose

That next day, I fitted the externally routed hose on my brother's bike. That was much easier.

I 3D printed some hose guides so that it did not touch the tyre or anything else when in the dropped position. It needed two guides but they worked well.

As an extra job I tried to adjust the front derailleur because initially it would not move up or down a gear. Again I followed an excellent video.
https://www.youtube.com/watch?v=ZNG7g83lI-s&t=51s

Although I have managed to get it working, it is not very positive. I'm fairly confident that too many of the components, including the chain-rings are just too worn.

As a side note, I found a way to stop the rubber ends falling off my work stand clamp. As simple as a couple of cable ties!

Roy's Whyte is now in a rideable condition and my Giant has a nice new dropper post, ready for those steep hills.

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Download 3D models:
Dropper Tube Guide, STEP, Fusion 360 and STL files (Zip)
Licence attribution - small business exception


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Specialist grease for bikes

A few weeks ago, my brother and I serviced a Rockshox dropper post. The recommended grease for the seals within those posts is a product called SRAM butter.

We didn't have any of that at the time but do now. What I set out to find out is, if it is necessary and would general purpose car grease have had any significant disadvantages for this purpose and, perhaps, the reverse of that question, what actually is SRAM butter.

I'll start by saying, that I am not in any way qualified to talk on this subject. This is all based on what I have been able to find and, as much as I can, understand from articles and adverts on the internet. Not only that but I still don't have definitive answers to either of the questions that I started with. I do, however, know a lot more about grease.

My conclusion:

I know it's odd to start at the end but for most people all they want to know, is what should I use.
The short answers are:

• For all normal bike maintenance, axles, bearings and spindles, general purpose lithium based car grease or the white marine stuff, is all you need.
• For specialist jobs, such as inside dropper posts, suspension forks and on rubber or plastic seals, for the price the manufacturers charge, just buy what they suggest, even if the price does appear a bit over inflated.

If you want a choice, for use on the seals on hydraulic shocks, forks and dropper posts, I'd use one of the following:
If I was in the US, I'd probably use Slickoleum.
In Europe, I can buy SRAM butter and Slick Honey which, as far as I can tell, is the same sort of thing as Slickoleum, just sold in smaller more expensive pots. Even then, it does not cost very much and only a little is needed.
There are plenty of other alternatives available in Europe, which the manufacturers claim, do the same thing. Motorcycle mechanics are a useful comparable source of information. They tend to use a generic, Red Rubber Grease, although, that may be a bit thick for bicycle forks, it will probably work.

It is likely, that general purpose lithium based car grease would dissolve in some hydraulic fluids, so a specialist grease would be required for the seals in those cases.

I liked the sound of :
RSP Slick Kick Grease (Ultra Slick) which is available in 500g tubs. Trouble is, it was more expensive, per gram, than importing Slickoleum from the US!

Technical

Two Components

Grease has two major parts which can be made of many combinations of materials to produce a grease that is best suited for any particular application. The major components are, lubricant and thickener.

Lubricant
This can be oil, synthetic oil or any number of polymers. I found a fairly scientific paper that was still clear enough to understand, at least for the basics.

Thickener
This is where is gets a bit hazy. What I know for sure is that the thickener, in the general purpose grease, used for cars, is lithium. That, however, is just one of many possibilities. In the case of Slickoleum, it is Anhy Calcium.

What to use for each purpose:

• Smooth running of wire cables - silicone grease
• Rubber seals - red rubber grease or perhaps silicone grease but probably not inside hydraulic systems.
• Seals in forks and dropper posts - specialists, such as RSP Slick Kick, Slickoleum, SRAM Butter, Slick Honey
• Rear shocks - includes PTFE - specialists, like Rockshox Dynamic Seal Grease
• Bearings and axles - General purpose lithium grease
• Threads that you need to get apart again - copper grease or anti-seize
• Threads that could work loose - thread lock - do not grease
• Seat posts - friction paste

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Reference:
https://www.sciencedirect.com/topics/chemistry/lubricating-grease
http://slickoleum.com/specifications.html
http://www.redrubbergrease.com
https://silverhook.co.uk/grease
https://www.silkolene.com/motorcycle/grease/pro-rg2-grease/
https://www.greasemonkeydirect.com/blogs/news/grease-guide-what-is-red-rubber-grease-used-for

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Rockshox Reverb service

My brother, Roy, offered to lend me a dropper post to try out. There was a condition. It needed to be serviced because, at the time, it was not working.

There are plenty of existing online tutorials, including the manufacturers videos, to show you how to carry out the service. Roy had already bought the kit of spare parts. Mainly rubber rings and other seals.

The following are bits of information that would have helped us to know, in advance. We might have known this, if we had read other articles!

Read the list of tools. Do not rely solely on the video.

You will need some specialist tools or some way to do the same thing.

None of them are expensive. The bleed tool is the most difficult to find an alternative to. You need something to block the hole but you also need to be able to release it to make sure nothing leaks out.

The 'oil height' tool is only used to suck out any remaining oil up to a level. A carefully held tube in a syringe would be able to do the job adequately. Just don't suck out too much fluid.

The 'IFP height' tool is also not essential but some correctly fitting metal or hard plastic pipe would be necessary. For the price of the tool, I would recommended to use it.

We did not have the appropriate offset spanners to use with a torque wrench. We used care and a guess, based on experience, of how much to tighten. Erring on the side of not breaking anything.

One tricky job is clamping the inner tube without damaging or marking it. We took it apart, very nervously, with it clamped between two flat blocks of wood.
Before we started the re-assembly, I made my own specialist clamp.

For the inner tube of the piston, it needs a 10mm hole, which I drilled in to some hard wood. I cut through the middle of the hole, along the grain, to form the two halves of the clamp. It works well.

 While I was at it, I added different size holes.

It took a few hours but we got everything done and back together and working, first time.

Having seen it apart, we know that the cause of the post getting stuck, was only the outer tube. In future we would probably carry out a service just to clean up the outer slide. That can be done without any specialist tools and may not need any replacement parts. Only if that does not work, would we buy the kit and service the hydraulics.

Once serviced it is necessary to bleed the shocks. Rockshox have another video to explain that.

I have since, fitted it to the bike.

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