macnab
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| posted on 6/2/07 at 12:41 PM |
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How low could you go...?
Carrying on from previous posts, how low could you run a 7? I ask this cos last week I was setting up my front suspension and simply set the lower
wish bone level with the ground but, looking at it last night I’d rather it was a bit lower and as for the back which sticks up in the air about 5
inches at the front of the rear arch I think it looks terrible. Now as with many places we are cursed by speed bumps and I’d usually keep a car above
these but seeing that the 7 has a totally flat bottom and the sumps almost flush. I was thinking of fitting two hardwood runners about an inch thick,
from the front to the back so I could ‘slide’ over any bumps…off course I’d be totally screwed if I never noticed one coming but I should have good
brakes 
So really I was wondering about the wishbones and what the consequences are if the were not level with the ground?
You know I managed to type all that without a single spelling mistake...not bad considering I'm dyslexic 
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nitram38
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| posted on 6/2/07 at 12:45 PM |
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Don't advise anything under 100mm.
No matter how you try to avoid the speed bumps, diversions and police incidents have a habit of taking you down really high bumps! 
Only been on the road since last August and this has happened to me 3 times.
There are certain roads in london that you need a 4 X 4 (Chealsea Tractor) just to get down.
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macnab
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| posted on 6/2/07 at 01:06 PM |
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Hmm I have heard that London has dire roads, though their not great most roads are of decent quality up here, oops now I going to get it...
I'm just not sure if the handling is not going to be ruined if the wishbones slope up.
[Edited on 6/2/07 by macnab]
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westcost1
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| posted on 6/2/07 at 01:10 PM |
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This one from a post earlier today is about as low as possible. My car looks high at the back to that’s with the shocks wound all the way down. The
17” wheels don’t help.
I was thinking of making a big carbon diffuser for the back to make it look lower.
 
Rescued attachment sevGallagher17.jpg
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Humbug
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| posted on 6/2/07 at 01:11 PM |
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quote:
Originally posted by macnab
Carrying on from previous posts, how low could you run a 7? I ask this cos last week I was setting up my front suspension and simply set the lower
wish bone level with the ground but, looking at it last night I’d rather it was a bit lower and as for the back which sticks up in the air about 5
inches at the front of the rear arch I think it looks terrible. Now as with many places we are cursed by speed bumps and I’d usually keep a car above
these but seeing that the 7 has a totally flat bottom and the sumps almost flush. I was thinking of fitting two hardwood runners about an inch thick,
from the front to the back so I could ‘slide’ over any bumps…off course I’d be totally screwed if I never noticed one coming but I should have good
brakes
So really I was wondering about the wishbones and what the consequences are if the were not level with the ground?
You know I managed to type all that without a single spelling mistake...not bad considering I'm dyslexic
...except for spelling "of course" as "off course"
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westcost1
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| posted on 6/2/07 at 01:12 PM |
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 Dyslexia rules ko!
[Edited on 6/2/07 by westcost1]
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David Jenkins
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| posted on 6/2/07 at 01:13 PM |
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I have to ask - why go that low?
A few months ago I watched some Caterham racing on Motors TV - tremendous fun to watch, very entertaing and there were some very skilled and brave
drivers. What was surprising was the amount of clear air under every car; this was probably defined in the regulations, but none of the cars seemed
at a disadvantage because of it.
David
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macnab
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| posted on 6/2/07 at 01:20 PM |
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quote:
...except for spelling "of course" as "off course"quote:
yip I do have BIG trouble with that
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macnab
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| posted on 6/2/07 at 01:22 PM |
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quote:
Originally posted by David Jenkins
I have to ask - why go that low?
A few months ago I watched some Caterham racing on Motors TV - tremendous fun to watch, very entertaing and there were some very skilled and brave
drivers. What was surprising was the amount of clear air under every car; this was probably defined in the regulations, but none of the cars seemed
at a disadvantage because of it.
David
Why, partly the way it looks and also I want to be as close to the ground as possible for that go-karty feel.
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John.Taylor
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| posted on 6/2/07 at 01:38 PM |
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I've modded my pinto sump, but it still sits just below my chasis. I was thinking of adding some 'runners' to the front chasis
either side of the sump but was advised against it as a mid corner compression/bump could cause the car to bottom out on the runner, unsettle it and
cause understeer.
This scared me off a bit but if anyone has added some runners and experienced it bottoming out safely I wouldn't mind knowing if it's a
good idea as I'm not sure I want to end up stranded and sumpless miles from home.
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nitram38
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| posted on 6/2/07 at 01:39 PM |
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I am trying to source some air "low rider"shocks for my next project which will be in addition to my normal inboard coil overs.
I am planning to set the car up very low but have speed bump 'button' to get me over them.
I have searched the web, but most of these kits are for bikes in the US.
The alternative is inflatable pillow type devices but they look too big and heavy for my next car.
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nick205
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| posted on 6/2/07 at 02:10 PM |
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The nominal ride height for any car is determined by the suspension design and geometry. The suspension design and more importantly the rotational
travel of the whishbones will have an ideal "at rest position" - i.e. not in droop or compression. Setting the ride hight of the car so
that the suspension is at rest at the correct point will minimise the effects of camber change of the wheel/tyre as the suspension moves through
it's travel (up and down).
You may be able to lower the car and adjust the suspension (top wishbone joint on the Indy) so that the at rest camber looks Ok on the wheel/tyre, but
when it starts to move through it's travel, the camber and other geometry will be adversely affected - i.e. not as good as they could be.
If you want to read up more about setting up your suspension, I found this book very readable and informative.
HTH - Nick
 
Rescued attachment book2.jpg
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greggors84
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| posted on 6/2/07 at 02:30 PM |
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If the runners are only going to be slightly lower than the sump just to protect it, then without them any bump or roll big enough to make the runners
hit the ground would make the sump hit the ground if they were not there causing the same effects, but causing damage to your sump at the same
time.
quote:
Originally posted by John.Taylor
I've modded my pinto sump, but it still sits just below my chasis. I was thinking of adding some 'runners' to the front chasis
either side of the sump but was advised against it as a mid corner compression/bump could cause the car to bottom out on the runner, unsettle it and
cause understeer.
This scared me off a bit but if anyone has added some runners and experienced it bottoming out safely I wouldn't mind knowing if it's a
good idea as I'm not sure I want to end up stranded and sumpless miles from home.
Chris
The Magnificent 7!
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BenB
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| posted on 6/2/07 at 02:47 PM |
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FWIW, I run a ride-height of 90mm around London (with its love of flipping speed bumps) but to do this the front of the car is cranked quite high. No
problems with cracked sumps so far (not even any nasty noises), but I take it very very carefully over the little buggers and am working on a dry sump
setup so I can have the full 100mm AND horizontal front wishbones....
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3GEComponents
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| posted on 6/2/07 at 03:27 PM |
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The practicle limit would be governed by suspension travel, the idea being that at full compression the chassis shouldn't come in to contact
with the ground.
Obviously this is an extreme situation.
In most cases the lowest you could go would be somewhere around 4".
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C10CoryM
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| posted on 6/2/07 at 04:31 PM |
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If your driving around on rough roads and still want to be able to scoot around I recommend at LEAST 3" of bump travel in the wheel. Anytime
the car bottoms out (suspension to bumpstop, chassis to ground) you will have a severe change in loading and the car will try to bug out. IE If the
front bottoms out it will push to the outside of the corner pretty hard. I would recommend 4" ground clearance if your sump is the lowest
point and you should still expect to smack it sometimes so a little thicker steel on the bottom of the sump to reduce punctures.
The only reason circuit track cars get away with being low is the smooth tracks, and the tires. Forget about building a track car for the street,
build a rally car for the street or you will end up with an un-predictable bastard thats no fun to drive. Been there, done that .
Cheers.
"Our watchword evermore shall be: The Maple Leaf Forever!"
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John Bonnett
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| posted on 6/2/07 at 05:24 PM |
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I would have thought that anything less than 100mm ground clearance for everyday road use would be courting disaster. You can imagine the rivet heads
being planed off the floor as you scrape over speed bumps and then I suppose you could end up with zero ground clearance tee hee!!
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rav
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| posted on 6/2/07 at 07:05 PM |
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Suspension geometry is all a bit mind boggling but as I understand it a horizontal lower bone with a shorter, inclined top one is the usual
compromise people go for - it gives you a roll centre usually just above ground level, a bit of camber gain as the suspension compresses and very
little change in track during normal suspension travel.
If you lower the chassis and keep the outer balljoints on the uprights in the same place the roll centre will be much lower, probably below ground
level.
This will mean the car wants to roll more when cornering, which could be countered by stiffer spring rates and/or an anti-roll bar buts its not an
ideal situation. The roll centre may move around a bit more too, I'm not really sure.
Having a stable roll centre that doesn't move all over the place when the suspension moves is supposed to be quite important. So they say.
Also the track will begin to change a bit which may be noticable when braking hard, I would imagine the front end will start to feel a bit
'skittish'.
It all depends how much you're thinking of lowering and how long the wishbones are really.
I say slam it on the deck and tell us all how much difference it makes!
As an alternative, you could find or make uprights which move the balljoints lower, so that you're effectively lowering the chassis and the
suspension together, or put smaller wheels/tyres on for the same effect.
Mark
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JoelP
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| posted on 6/2/07 at 09:50 PM |
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On track you dont want it too low either - you can save many seconds every lap if you hit the kurbs right, to take as much out of each corner as
possible. You want 3 or 4 inch for this anyway.
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macnab
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| posted on 7/2/07 at 12:38 AM |
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4 inch's! ehem that's like a monster truck!
I can't even get my foot under the front of my beetle...
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JoelP
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| posted on 7/2/07 at 06:59 PM |
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all road locosts ive seen have around 4" at the front, usually a bit more at the back, and some are higher. If you go for just 3 inches at the
front, most sumps hang another inch below this - 2" under your sump is asking for trouble.
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