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Old 24-08-2012, 02:19 PM   #16
ardonfast
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lol its ok, this only happens one day a year in my garden, the normal roads are not to bad, i was going to invite all you guys or maybe not,lol
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Old 24-08-2012, 02:31 PM   #17
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Quote:
Originally Posted by Birdman View Post
Unfortunately this advice Kaison is not good. You cannot just put soft springs on, because they are inclined at between 30 -45 degrees. At 45 degrees you need to double the spring poundage to get the same effective spring rate. ie: if you want 450lbs effective springing up front you need 900lbs springs when they are acting at 45 degrees. If Shaun were to decrease the spring rates the coilover would bottom out more easily with the consequences that come with that. You get more coilover piston movement for less actual wheel movement, the ratio having been altered. The suspension will have less overall movement and be pretty hard as on a race car. Also there were threads ages back about the rear upper tiebar sustaining damage ( only on the race frame) and this was more to do with using it on the road, from what I can remember. Mininut knows much more about the AMT frame, but it is supposed to be for track and occasional road use.
This is why I said he should ensure there were no issues with bottoming out.
It's a similar argument to the old coil spring craze. - They're meant for track use, people using them on the road were having all kinds of issues.

I know those issues aren't all the same and it's a different ball game but it's all a balancing act at the end of the day.

As long as he avoids potholes at speed and takes his time over speed bumps, it'll be fine. - It's common sense and adjusting your driving style to the environment.
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Old 25-08-2012, 01:18 PM   #18
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ok i have always been dubious about any frame that aint standerd mini.and i fully admit that im in the situation that i would strongly advise against[thats messing with a mini]
so ive started a biuld diary as best i can. i want to lern as i go and always willing to hear any sugestions.then pick or leave them down to my instincts]
and qwite rightly so, the integraty of my amt race frame has been brought to qwestion
i am going to continue useing it.in the worst case it will brake,lol
so without going over ground alredy said obouve[thanks]
CAN SOMEONE ZOOM IN AND STATE WHAT GOESE WRONG AND WHY,thanks
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Old 25-08-2012, 04:56 PM   #19
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You may want to check your maths their Birdman. At 45 dgress you would have 71% (approximately) of the equivalent vertical spring rate. At 30 degrees you would have half.

It doesn't actually matter at what angle the coil overs are set at. To get double the equivalent vertical spring rate then you just double the spring rate. All you are in effect doing is scaling up the force vector. When you scale things you don't change the angle.

Saying that though you are correct in saying that if you soften the springs up too much then it is liable to bottom out. The solution is not to change the spring rate but is to change the angle of them. If you shallow out the angle at which they are mounted at then it would soften the ride without increasing the movement of the dampener.

I'm not familiar with the AMT frame but if it is using standard mini hubs could you not just disconnect the coil overs from the frame and use a normal set that bolt to the shock absorber bracket like most do?
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Old 25-08-2012, 05:45 PM   #20
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Quote:
Originally Posted by M J W J View Post
You may want to check your maths their Birdman. At 45 dgress you would have 71% (approximately) of the equivalent vertical spring rate. At 30 degrees you would have half.

It doesn't actually matter at what angle the coil overs are set at. To get double the equivalent vertical spring rate then you just double the spring rate. All you are in effect doing is scaling up the force vector. When you scale things you don't change the angle.

Saying that though you are correct in saying that if you soften the springs up too much then it is liable to bottom out. The solution is not to change the spring rate but is to change the angle of them. If you shallow out the angle at which they are mounted at then it would soften the ride without increasing the movement of the dampener.

I'm not familiar with the AMT frame but if it is using standard mini hubs could you not just disconnect the coil overs from the frame and use a normal set that bolt to the shock absorber bracket like most do?

I'm afraid you are wrong, nothing wrong with my maths. At 45 degrees the spring rate will be exactly half that of when it was dead vertical.
Here you go:

http://www.rodandcustommagazine.com/..._spring_rates/

Both Shaun and I have angled coilovers. His is the AMT Race frame. I built my own frame with similar setup, only heavy duty type frame.
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Old 27-08-2012, 03:48 PM   #21
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thanks men.food for thought,,thers been talk of breakege. can anyone say what the vularable place is???,pic,s are even better,or a link?? dont get me wrong,thanks for the tipoff,but i would like some evidence of this if poss.at the moment i cant see what can possably go wrong thers loads of thred ajustment on the spring/also oil damping ajustment,ther is no acurate formuler for angels of spings]other than the one that aplyes to your setup,its true that a upwright spring will behave diferantly to the angled one,
however damage will only accur if the spring runs out of travel.
if you allow your car suspention to have no travel your asking for it!!!
im not defending my frame,that was out of my controll.i got my kit before i found this forum. if i had found it sooner my choice would have been diferant.
im tempted to try it as it is.then i can accurately advise others if needed.
i am tempted to do as advised by M,J,W,J i have looked at it. its possable altho the bulkhead to front frame bars are a bit close,and in the way of the large ciolover.
any facts on brakege will be nice,thanks shaun
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Old 29-08-2012, 01:59 PM   #22
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The race frame uses a different top arm mounting arrangement so if you wanted to change to vertical you'd have to change that too.
On my race frame I have maybe 5-10mm of suspension travel? Whats yours like when you bounce it up and down?
As for the question of the breakages - its a can of worms! The recorded failures were the rear top arm, after hitting a bump of some sort. I'd not worry about it just yet!
Looking at you pic the rear top arm is too long anyway, the front arm should be more at 90 degrees to the frame. You may have to chop some off the end, from memory 10-15mm or something like that.
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Old 29-08-2012, 06:47 PM   #23
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Quote:
Originally Posted by ardonfast View Post


If you look at the photo the upper rear tie bar is horizontal and if you run too low or have too much suspension travel this rose joint binds against the frame and this in turn can bend or snap the short tie bar.

Road & Race AMT frames both have this potential failure designed in so don't run too low & try to set things up so you don't have too much susp travel.

The AMT frames are a lovely design other than this wee issue
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Old 29-08-2012, 07:59 PM   #24
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Didn't someone turn them round on their frame?
It's not as much an issue on the race frame as its designed for track use, ie f'all travel anyway.
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Old 30-08-2012, 03:14 PM   #25
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The race frame uses a different top arm mounting arrangement so if you wanted to change to vertical you'd have to change that too.
On my race frame I have maybe 5-10mm of suspension travel? Whats yours like when you bounce it up and down?] richspec thanks i cant try to bounce it coz the 2 front mounts to front valance are not yet finnished/connected i can give it a try when i work out a nylatron bush +[ towing eye],lol t.b.h this is not a good picture ile get a better one,also the frame is on a jack,wheel is of the ground, neather are the rosejiont arms ajusted, this is a minefeild [dont you just love the standerd mini setup] thanks again for your input,,
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Old 30-08-2012, 03:23 PM   #26
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andy S]>>If you look at the photo the upper rear tie bar is horizontal and if you run too low or have too much suspension travel this rose joint binds against the frame and this in turn can bend or snap the short tie bar.

Road & Race AMT frames both have this potential failure designed in so don't run too low & try to set things up so you don't have too much susp travel.

The AMT frames are a lovely design other than this wee issue] THANKS ANDY S ,
i will have to wirebrush it all up/cleen and grease+ ajust as best i can then take some pics that can be seen in some sort of fashtion,ive read all thats said and slowly getin my head around it [thanks shaun
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Old 30-08-2012, 04:42 PM   #27
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Quote:
Originally Posted by ardonfast View Post
The race frame uses a different top arm mounting arrangement so if you wanted to change to vertical you'd have to change that too.
On my race frame I have maybe 5-10mm of suspension travel? Whats yours like when you bounce it up and down?] richspec thanks i cant try to bounce it coz the 2 front mounts to front valance are not yet finnished/connected i can give it a try when i work out a nylatron bush +[ towing eye],lol t.b.h this is not a good picture ile get a better one,also the frame is on a jack,wheel is of the ground, neather are the rosejiont arms ajusted, this is a minefeild [dont you just love the standerd mini setup] thanks again for your input,,
Shaun, the bouncy thing is not really a problem. My front end isn't connected to my frame at the front end by fixings. You will find it hard to bounce the car anyhow with the high poundage springs. I can only get a small amount of bounce on mine. What you can do is get the car on axle stands, remove coilover unit ( for cleaning) , whilst you have it off the car, remove the spring and temporarily replace the coilover without its spring. Then you can jack up that side of the suspension with a trolley jack and see the total suspension travel between full droop and full bump and also see how much travel you will get on that rear tie-bar rose joint before it binds up. If you take a measurement from ground to lowest part of frame and car before you do all this, you can calculate roughly if anything else is going to get dangerously close to the deck on full bump. Just a thought...
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Old 30-08-2012, 06:19 PM   #28
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from memory the top coilover mount is..errrr.....fun.!
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Old 30-08-2012, 06:24 PM   #29
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Shaun, the bouncy thing is not really a problem. My front end isn't connected to my frame at the front end by fixings. You will find it hard to bounce the car anyhow with the high poundage springs. I can only get a small amount of bounce on mine. What you can do is get the car on axle stands, remove coilover unit ( for cleaning) , whilst you have it off the car, remove the spring and temporarily replace the coilover without its spring. Then you can jack up that side of the suspension with a trolley jack and see the total suspension travel between full droop and full bump and also see how much travel you will get on that rear tie-bar rose joint before it binds up. If you take a measurement from ground to lowest part of frame and car before you do all this, you can calculate roughly if anything else is going to get dangerously close to the deck on full bump. Just a thought...
i've not tried this but isnt that going to give a theoretical travel as opposed to real. in reality is not going to achieve that because the springs are so stiff??
and if the springs are soft enough tp permit full travel they'd be too soft??
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Old 30-08-2012, 08:05 PM   #30
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Just been out for a look at mine, as it is now the rose joint is nearly touching the upper most support, i;ve already got the spring quite wound up to gain some height. So thinking about it the coilover is a tad too short, or have i got that the wrong way round?
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