SKS Rennkompressor, Review And Modifications.

[fiks]

Mine in over 25 years old and looks the same as Gazelleer's, with the same push on adapter. The rubber washer wore out years ago, must be 15, and I haven't used the pump since then. I bought a spare from a bike shp but it didn't fit. I always have a Zefal HPX on my bike so I use that.

The gauge is perfectly fine, there's a red needle which you can set. In any case I only used the needle as an approximate guide, mainly as not to over inflate. The final pressure check is done by squeezing the tyre.

I did buy a cheap track pump from Lidl (I think £7* but it was a few years ago), just for the pump head to fit on to my SKS. I only finally got round to using it a few weeks ago! And it seems too good to cut off the head! So my SKS remains unused. The Lidl pump does have a wide barrel though and pumps a lot of air on each stroke so I need to be careful not to over inflate.

I try to use bars (6.5 - 7 bars is usually about right for me) but it seems cyclists in the UK have followed the Americans and use psi.

*about 8 Euros

 

[chrisbeeching]

I have found a source of supply; Zyrofisher is able to supply the 40mm washer required - which they have done. So my pump is up and running again. Brilliant and helpful service: can’t praise them highly enough. www.zyrofisher.co.uk

 

[531Man]

Hi fiks,
Not to be taken too seriously, but I just couldn't let this go unchallenged,
"but it seems cyclists in the UK have followed the Americans and use psi."
I think you will find we in the UK were using psi from the very beginning. The Bar is a metric system unit from meteorologists who have only latterly introduced the Bar.
The USA, like us continue to use our older system of pressure.
Regards,
Robin.
aka 531Man

 

[mortirolo]

Re:

HI! I'm wondering something about the SKS Rennkompressor and this feels like the right place to ask for advice.

I have an SKS pump - really simple wood and steel thing - that I bought over 10 years ago for £10, and I really like how simple it is.

https://www.dropbox.com/s/utrf44qufd62p ... 1.JPG?dl=0

Over the years, SKS have sent me replacement parts when it failed, which I have appreciated. But recently, the head broke, and they have told me that they do not have replacement hoses for this pump any more, but that I can attach a new head.

https://www.dropbox.com/s/rq0yvb1ohte1n ... 2.JPG?dl=0

Which is fine ... but actually I am curious ... is this hose connection to the base really different from the Rennkompressor?

https://www.dropbox.com/s/d0nq5azigvy97 ... 7.JPG?dl=0
https://www.dropbox.com/s/822wl67ouyvju ... 4.JPG?dl=0

I'd say it's about 8mm diameter and 28tpi but please take a look yourself.

I'm a bit skeptical that that SKS designers would randomly change the gauge and threading on their hoses between models, but maybe they did? I don't know.

It would be reassuring to know if I can swap out this hose for a Rennkompressor hose if needed down the line.

In the meantime I'll attach a new head to this one and keep it alive!

 

[EnCee]

In this week's episode of Pimp My Pump ...

I found this thread very useful when I was considering modifying my SKS Rennkompressor pump.

There was nothing fundamentally wrong with the pump I purchased except I found the pressure gauge to be a little hard to read. The first upgrade was therefore to replace the original SKS gauge with a 63mm gauge. The threads on the pressure gauge port at the base of the pump are 1/4 inch BSPP (G) and there are plenty of 63mm gauges available with a suitable male fitting in the centre of the back of the gauge. I bought an old gauge on eBay and made two errors: the threads on the gauge I purchased are NPT and the male fitting is offset rather than centered. Instead of buying a different gauge (which in hindsight would have been cheaper), my solution was to attach the gague using Cejn 320 series quick release fittings. An advantage of this is that in future I can quickly swap out the current gauge for one with a different pressure range (bearing in mind that I understand the accuracy of most pressure gauges is best in the middle third of the gauge).



Not content with changing the pressure gague, I also changed the hose and pump head. The male threaded fitting at the end of the hose that came with my pump is M8 x 0.75. I could not find a suitable replacement hose tail fitting with those specifications, so I decided to change to a more readily avilable 1/8 inch BSPT fitting. This meant having to drill the hole in the base of the pump to make it larger and then use a tap to create 1/8 inch BSPP threads. I had never done this before, but I consulted some drill / tap charts, watched a few YouTube tutorials, bought a suitable drill bit, tap and tap wrench and then gave it a go. It was quicker and easier than I expected and I managed not to mess it up.



For the hose, I used 1/4 inch Flexzilla in a lairy chartreuse colour. For the couplings and adaptors, I used items from the PCL XF Euro range (compatible with Cejn 320 series and many others). The hose and fittings are attached using Oetiker 167 stepless ear clamps or traditional worm drive / Jubilee clamps. Finally, the pièce de résistance at the end of the hose is a fabulous Hirame / Kuwahara pump head which is a real pleasure to use on presta valves.



All in all, the cost of making these changes was considerably more than the cost of the pump itself, but I am very pleased with the outcome and along the way I learned a lot about pipe thread standards, air compressor systems and pneumatic couplings and adpators. As a bonus, I also learned how to drill and tap a hole in metal.

 

[Quotama]

I have been inspired by this thread to upgrade my SKS pump as well. Thank you EnCee and others for giving me the information on the thread diameter. I could now immediately buy a similar looking meter with a center thread in 1/4 (G) bspp, some teflon tape and a 15mm spanner and it threads right in. No need for funky adapters, drilling or tapping if you get the right one. I got a 0-10 bar 63mm one of amazon. I gave it a knock bumper with some layers of old latex innertube. ow the only thing i need is one of those funky Kuwahara pump heads. Its on the wish list and maybe a coloured hose. But the first step was easy, just because of your post.

 

[N-plus-one]

Re:

Nice modification of an already great pump! The only thing I have to do every once in a while is replace the pump head rubber seal (€ 0,65). My over 30-year-old example has no clamping mechanism in the pump head, you just push it onto the valve.

However, you overlooked one essential thing in your excellent work. Cycling is a metric sport, therefore pressure should be measured in bar, not psi. This is very unfortunate because it means you'll have to replace the entire gauge...again.

I am aware of the fact that certain brands of tyres indicate pressure in psi as well as bar but for any serious riding the former should be ignored for being inaccurate.

Fortunately there is a "fix" for the unclean and heretical reference of psi, in place of metric units, which does away with the need to replace the pressure gauge.
Simply apply the conversion factor of 1psi equals 0.0689476bar - a bit of maths that can easily be done in the head without recourse to aids or additives (which always seem to be imperial, the exception being fingers which are generally decimal).

Et voila, mon pute! solution found.

(use of French language to add gravitas to an otherwise tongue-in-cheek post)