coyoteboy
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| posted on 28/7/10 at 10:19 AM |
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Ground clearances and suspension design
Hi all, newbie kit builder here but not newbie car modifier or engineer 
I'm planning a scratch build of my own design but I'm scouting about for opinions and background info from sources other than chassis and
suspension design books as these tend to centre around race car design and as such spec 1-2" clearance.
One thing I'd like to hear opinions on is minimum ground clearance (between the wheels) on a road-going vehicle. My normal road car has 140mm
clearance and doesn't seem to be too problematic on anything but the highest of speedbumps, and I would accept some difficulty such as finding
other routes around such things, but what I don't want is to get so low that I need chassis plates to prevent me bouncing it on the ground in
high speed bumps as per F1 cars
My original plan was to drop clearance to about 100mm?
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TimC
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| posted on 28/7/10 at 10:22 AM |
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quote:
Originally posted by coyoteboy
My original plan was to drop clearance to about 100mm?
Seems sensible to me.. I certainly wouldn't go more than 10mm lower.
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Hammerhead
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| posted on 28/7/10 at 10:28 AM |
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my elise has 110 front 120 rear and is just about ok
Just to clarify the elise heights are measured behind the front wheel and in front of the rear. These are chassis heights. The actual front clam is
90mm at lowest point.
Its a bit too low tbh.
[Edited on 28/7/10 by Hammerhead]
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Miks15
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| posted on 28/7/10 at 10:28 AM |
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firstly welcome
secondly 100mm is about the norm i think, thats roughly where mine will sit
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nitram38
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| posted on 28/7/10 at 10:29 AM |
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100mm is about right, but you can go up to 50mm lower and use a Hydraulic lift system (I supply them btw!  )
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alistairolsen
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| posted on 28/7/10 at 10:45 AM |
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On fwd hatchbacks 100m has never given e a problem, never touched anything with it. 70mm on the other hand saw the exhaust hitted EVERYTHING!
My Build Thread
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procomp
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| posted on 28/7/10 at 11:02 AM |
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Hi
It's all down to what sort of body design your planning up front. Take a typical sevenesq design for example These can run as low as 70-75mm
quite safely due to the nose underside area generally being higher as it protrudes further forward of the front lower chassis.
The biggest issues are the sump and gearbox issues. However depending upon your body style/design protruding forward of the front axle line will
determine the majority of considerations to mull over. And whether its a transverse or in line and of course front or rear engined. Using 15"
wheels/tyres will give you bigger scope for ground clearance without having to compromise suspension geometry unless your using bespoke uprights to
give good geometry and sufficient ground clearance as a package.
Cheers Matt
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Steve Hignett
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| posted on 28/7/10 at 11:05 AM |
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My MAC1 was 90 - 110mm front to rear and was fine over speedbumps...
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coyoteboy
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| posted on 28/7/10 at 12:41 PM |
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I'm considering something atom-esque, using the engine (and uprights, certainly rear) from an MR2 turbo, keeping the mid(rear)-engine RWD layout
but removing the overhangs and body. I'll need to look at modifying the uprights to work with dual wishbone arrangement and pushrods with
reasonable camber control. IIRC the standard wheel size is 15" but with something around a 60 profile tyre. My biggest concerns are the shear
weight of the engine and transmission (looking to be in the region of 180kg combined as far as I can tell, there's a thousand sources out there
each claiming different values) and not bouncing that on the floor while keeping it as low as physically possible without having a virtually rigid
rear end.
I originally wanted to go 4WD with the same engine but the running gear from the celica GT4 but that would effectively give a front-mounted 200kg lump
which looks hard to package and like understeer hell? I still yearn for the 4WD solution, as getting the power to the floor and the rather endless
grip it provides is far more fun to me than the rather dainty and cautiously balanced feel a RWD monster has, but packaging is proving a nightmare.
I've gone through countless drawings, considered diff-flips, considered going down the route of a 4x4 box etc but none have been pretty.
There's just too much stuff to cram in!
[Edited on 28/7/10 by coyoteboy]
[Edited on 28/7/10 by coyoteboy]
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nitram38
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| posted on 28/7/10 at 12:52 PM |
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Buy my car!
Has R1 bike engine, 480kg total weight, hydraulic coilover suspension for ride height adjustment. POA
Comes complete with tonneau covers (4)
 
Description
[Edited on 28/7/2010 by nitram38]
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coyoteboy
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| posted on 28/7/10 at 03:09 PM |
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nitram38 - that's exactly the sort of thing I want to do, but I'm not keen on bike engines (no experience, don't want to deal with
reverse box, not convinced about lifespan and torque problems, don't really like revvy noise - much prefer gobs of torque)!
What are you selling for?
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Miks15
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| posted on 28/7/10 at 03:20 PM |
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quote:
Originally posted by coyoteboy
don't really like revvy noise
most ridiculous thing ive ever heard 
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coyoteboy
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| posted on 28/7/10 at 03:25 PM |
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I get that a lot! I just hate cars I have to thrash to get any guts from. I do appreciate their low power to weight but im just not convinced on
the whole! Plus the reverse/IVA problem...
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Fozzie
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| posted on 28/7/10 at 03:37 PM |
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quote:
Originally posted by nitram38
100mm is about right, but you can go up to 50mm lower and use a Hydraulic lift system ...(I supply them btw! ).....
Oooo did you really want to say ^ ^ ^ that bit? 
'Racing is Life!...anything before or after is just waiting'....Steve McQueen
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nitram38
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| posted on 28/7/10 at 05:20 PM |
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quote:
Originally posted by Fozzie
quote:
Originally posted by nitram38
100mm is about right, but you can go up to 50mm lower and use a Hydraulic lift system ...(I supply them btw! ).....
Oooo did you really want to say ^ ^ ^ that bit?
Yes ask ChrisW, I've been trying to pin him down on trader status
I spoke to him at Uxbridge and emailed him
He said he would sort it out!
[Edited on 28/7/2010 by nitram38]
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coyoteboy
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| posted on 29/7/10 at 01:42 PM |
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nitram - where's your chassis from - did you design it yourself or is it a kit?
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nitram38
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| posted on 29/7/10 at 01:51 PM |
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It was designed and built from scratch, of course using the atom as a guide. Do a search on Motaleira, there are loads of posts and pics
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