Drilling hydro top arms for shock absorbers

[rolesyboy]

I have decided to fit front shock absorbers to the front of my Hydro Mini. I need to drill out the bump stop fixing hole from 5/16 to 3/8.
How can I do this. It’s an odd shape and i need to hold it still while I put it under a pillar drill. No, I don’t have a lathe.
Thanks a lot. Mark

[Spider]

No, not a turning operation that one.

You need a Mill

When I used to do them in the Pillar Drill, I'd go through my drill bits and find one that's neat in the existing hole. Put that in the Drill Press and use it as a Pilot to set the existing hole up square, then clamp the arm up in the vice and then clamp the vice down. Swap over to the finished size drill bit, some cutting lube and drill at a slow speed.

But seriously, I now do the in the Mill and move the hole centre up a little

[whistler]

I just put my top arms in a vice and drilled through with my cordless drill to 3/8".

[rolesyboy]

That has crossed my mind but i bottled it in case I went of piste.

[whistler]

That has crossed my mind but i bottled it in case I went of piste.

I drilled up to 3/8" in stages so that the drill followed the existing hole.

[Hipwell]

Be careful to check the holes line up to the buffers first. Mine didn’t

[Rubbersoul]

I am doing the same to my car. Hipwell- What do you mean about holes line up in the buffers?
Don't you just drill through the buffer bracket at the same time? The shock stud goes through both the buffer bracket and the top arm right?
I was going to do it with the arm on the car.

[Hipwell]

https://www.minispares.com/product/Clas ... |Back%20to

If you read the blurb the holes don't line up.

[Peter Laidler]

Some of the top-arm hydro buffer brackets are so poorly made that the mounting holes just don't align with the 5/16" bolt hole in the upper arm. So you've got to sort this out with a file before you can go any further. I presume that most mini DIYers have access to a file or two.

Whistler is right about opening up the hole. the 3/8" drill, presuming everyone has one of course, will use the 5/16" hole as a centre and follow it - given a bit of care and a decent quality drill.

This same subject was aired a year or so ago

Added later..... A properly drained, filled and pressurised hydrolastic system was made and designed to do away with the need for additional damping. It IS its own damper mechanism by design!

['S'-type]

I have done this job in situ with a hand drill and decent bit. As has been said the bit follows the existing hole so it was pretty straight forward. This is coming from some one who has had their fair share of balls ups trying to do accurate drilling with a hand held drill.

What about adding competition bump stops? They are more progressive than the stock ones, and dare I say it, when your hydrolastic gives out you have a little more rubber cushion to get you home. Vizard in 'How to modify etc........' even suggested before adding the front shock kit it is best to try negative camber arms and competition bump stops all round if you have the stiffer post 68 displacers ( especially the blue/silver band ones which basically are unobtainable.)

Vizard also suggested another possible mod. This involved fitting a restrictor valve ( tap) restricting fluid transfer from front to back to slightly increase the systems natural damping that Peter reminds us of.

So a lot depends on which displacers you have as to how far you need to go in adding all the ST bits. But overall it's an easy job to fit it all.

[Peter Laidler]

Funny you should say that Doc.. I fitted comp bump stops as a get-me-home measure when I realised that a hydro failure on standard wheels and tyres and hydro WASN'T going to get me home. Nor would a set of front dampers come to that.

That's when I realised that the dire hole alignment of the modern buffers was totally crap. But solved it with an hours work and a hand file.