Adjustable front top mounts

Discussion in 'Suspension, Brakes, Wheels & Tyres section' started by arch, Jun 9, 2019.

  1. What does everyone do to adjust a top mount in situ. The set up is one of the stupidest designs I have seen if you have to keep dropping the strut to adjust it would be almost impossible to get the camber/castor set up accurately side to side
     
  2. When my BC's were fitted, they cut a bigger hole, about 76mm, so it can be adjusted without dropping the strut
     
  3. Cutout the strut top

    Even then depending how far the adjustment screws are from centre of the top mount it may still be tight
     

    Attached Files:

  4. You got a pic Ian ?
     
  5. Thanks guys had heard about this being done but surely given that is a structural area it has to weaken the strut top. Going out to 76mm is a lot of material to remove
     
  6. -Jamie-

    -Jamie- RSM Moderator

    It isn't structural
     
  7. Done a lot of track days and driven thousands of miles and no problems.
     
  8. Did have on my old phone, can get some tomorrow for you
     
  9. Jamie are you seriously of course it's structural why do you think proper roll cages should pick up on the strut tops.
     
  10. A full roll cage in a Megane 2 or three doesn't use either front or rear suspension mountings.
     
  11. That's not really relevant my point was that the strut tops are used in many cars to tie into a cage to increase rigidity of the front end significantly. There is no debate if you remove material from that area you will weaken it, the amount it is weakened is the question .e is it insignificant or is it enough to cause an issue. The standard hole is approx 48 to 50mm diameter but this is strengthened by the swaged edge cutting that off will weaken this area.
     
  12. I'm not going to argue with you, you obviously know more than me
     
    James275 likes this.
  13. Wasn't trying to argue Ian but I have been moding and racing cars for a long time maybe not Megane's but car structures are not hugely different. Has anyone had experience or seen a modded MK3 strut top deform after hitting a pot hole of kerbs on track
     
  14. -Jamie-

    -Jamie- RSM Moderator

    The turrets are on the firewall. It's not some floppy old car


    Go and ask Charlie at CGR, He'll tell you the same thing and has fitted numerous kits and modified the turrets to suit.

    He kinda knows what he is on about seeing as he builds stuff for LMP cars.

    I only had a bit welded in to tidy it up and make it look OEM


    Literally hundreds of Meganes all over Europe and firther afield doing the same thing, Inc some race spec cars at the Ring and dedicated Ring tools built by the most experiance Megane builders.
    Zero issues.
     
    Last edited: Jun 10, 2019
  15. I had mine done at CGR, Charlie is so knowledgeable on Megane suspension.

    Maybe he is referring to the likes of Ford, Vauxhall's etc, with cheese chassis's :laughing::laughing::laughing:
     
  16. Ok guys let's put this to bed. I am not in anyway and did not suggest any of the individuals mentioned do not know what they are doing and am not saying I am in anyway an expert on car structures but you are also making an assumption that I do not know what I am doing either. I asked a genuine question so not really sure what the issue is. While the Megane is a modern car with a chassis built to meet the various design specs associated with a car of it's age you still cannot ignore what that area is designed to do. I am a licences aircraft engineer and happen to know a fair bit about structures and load paths, the whole strut top area has been designed to withstand the various forces that will be placed on the area. One of those forces will be an upward shock force associated with the suspension bottoming out when hitting a pot hole or during hard track use. The bump stop will absorb some of that force but not it all. If you choose to look at how the top is designed you will see that it has a swaged lip at the normal opening, it also has 3 raised and formed areas 120 deg apart which run into another circular raised and formed area. This is designed to increase the structural strength of the material and dissipate any forces. Taking out any of that area will reduce its ability to withstand some forces which may be placed on it that is not something you can debate it's a fact. What may well be the case is that there is sufficent strength built into that area that removing some of the material does not weaken the area by an amount that is significant. That will however also vary by whatever struts are fitted, the standard strut and spring assembly will have a a fair amount of compression before you get anywhere near the bump stops however once you start adding coilovers and lowering the car then you are then reducing the amount of compression you may have before the strut bottoms out especially on some cheaper kits. So in my opinion it is definately structural because it is strengthened and designed to absorb suspension shock loads is it safe to do this it would seem it is given what people have done and the fact there doesn't seem to have been any issues from varied use on track and road, which was what I was asking so thanks to those who replied.
     
    Chavez likes this.
  17. Does anyone have a guide or suggestion as to how to mark and cut the strut top.
     
  18. You got a pic Jamie showing the welded in bit, what diameter is the cutout ?
     
  19. Did you manage to sort pics Ian ?
     
  20. 76mm
     
  21. -Jamie-

    -Jamie- RSM Moderator

    Can't remember size but bigger than the others posted due to how the AST top mounts are ddb98a2c0f16d89e7dcb97c97670c8b4.jpg 8cf937b4bad12efb196af39d8d2030db.jpg
     
  22. Jamie That thickness of insert will have put a lot of strength back in you can't compare what you have had done to just chopping out an area and is exactly what I would have done. Who done the fabrication for you.
     
  23. Agreed - that's the best I've seen, just a bit more work than cutting a hole !

    I think we are going to either -

    a) Make the existing hole a slot (towards the centre of the car) to allow the topmount nut to protrude and allow increased negative camber. This is probably the easiest but means that the strut will have to come off for camber adjustment !

    b) Drill out to 76-80mm diameter, get all suspension mounted and working as we want it and then in the future make the hole a little larger and weld in a ring
     
  24. I personally would not slot the strut mount holes you have then introduced a 2nd potential fastener tbat can come loose. If you want more castor thete are other routes to doing that.
     
  25. Hi, sorry you miss-understand me. I'm suggesting slotting the 45mm hole say 20mm towards the centre of the car. The mounting holes stay as they are. This would allow the adjustable topmount to move 25mm approx giving negative camber adjustment (but would have to remove the strut from the car to adjust)

    Hope that makes sense

    What are you suggesting regarding increased caster ?
     
  26. -Jamie-

    -Jamie- RSM Moderator

    You won't be be able to move it that far inbound if on stock style springs as itll hit the inner tower
     
  27. Shouldn’t be an issue as using coilovers
     
  28. I think what Jamie has had done is for me the best solution. I am risk averse so would not cut my strut tops wîthout putting some form of strengthening back in. I think if you slot the oem hole you would make it a lot harder to put strength back in. Cutting the hole bigebr and reinforcing it would certainly satisfy my OCD.
     
  29. Ian

    Don't suppose you would check that dimension would you ?
     
  30. What are people using to cut this larger hole ?
    Is anyone able to describe how they have done it.
     
  31. I measured it for someone else, don't think it changed since then :laughing::laughing::laughing:
     
  32. Ah ok thanks it just looks bigger, guess I'll find out on Saturday when I put a 3" punch through the strut top
     
  33. Are you doing the work ???
     
  34. I reckon so
     
  35. Lift the bonnet and disconnect the hydraulic rams, tie a rope to the bonnet loop and secure it to the rear of the car, remove the wipers and the scuttle tray then you will just have enough room.
     
  36. Cheers

    We have a selection of holes saws 76 / 79 / 86mm (86 I believe is too big) but have seen one used on u tube

    Hopefully I'll manage to borrow one of these with a 3" punch, holesaw will be plan B

    https://www.greenlee.com/us/en/hydraulic-hand-pump-767
     
  37. 76mm is plenty big enough, that punch thing will be a lot lot quicker, they took an absolute age to do mine with a drill, about an hour each i was watching so that maybe the reason it took longer :laughing::laughing::laughing:
     
  38. I've done a mock up at 76mm and we won't be able to get full negative camber (3.5 Deg approx) using the gaz top mount as one set of the adjuster screws sits under the strut top. We will be going for 2.5 to 3 deg'
     

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