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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Originally posted by coyoteboy
My original plan was to drop clearance to about 100mm?

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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]

firstly welcome

secondly 100mm is about the norm i think, thats roughly where mine will sit

100mm is about right, but you can go up to 50mm lower and use a Hydraulic lift system (I supply them btw! )

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!

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

My MAC1 was 90 - 110mm front to rear and was fine over speedbumps...

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]

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]

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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Originally posted by coyoteboy
don't really like revvy noise

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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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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! ).....

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Originally posted by Fozzie

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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! ).....

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Oooo did you really want to say ^ ^ ^ that bit?

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nitram - where's your chassis from - did you design it yourself or is it a kit?

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