Building Haynes Roadster, and i'm on ground to chassis - ground to engine clearances now.
I know that there is no rule how much is enough, but i need few opinions.
By now i have engine sits 10cm above ground and chassis further 4cm up.
It will be great for my plans to lower the engine another 10mm down, to free some space between transm and chassis.....i put entire GB-engine combo as back as possible because my plan is to use rear steering rack and gearbox is worryingly close to the tran tunnel.
Any advice if it's better to rise the chassis up compared to ground, or lower the engine and keep same frame position?
What is you engine to ground and bottom to ground clearances?

Description

From what I've seen of seven type cars I would say that chassis is too high tbh.
The angle of your wishbones will dictate the chassis height once its say on the wheels.
Average chassis height from what I've seen is around 11-12cm.
So if you lower the chassis down to say 11cm your sump will be too near the road,so ideally the engine needs lifting as high as possible in the chassis to give the maximum clearance to the road.
This is limited by the bonnet on the car normally.

I was having a similar nightmare due to the height of the engine in my car. If moved the engine up it would poke out the bonnet, if I left it where it was I would tear the sump off within a week. So settled on cutting down the sump and having 11cm of chassis/floor clearance and 9cm of sump/floor clearance. I also had to modify the transmission tunnel to create a bit of space for the gearbox.

[Edited on 22/10/19 by J666AYP]

My car <<< gearbox was 105 mm off the ground, and I could take chunks out of every speed bump I went over
so, unless you want to ruin an engine every time you drive,

steve

When I first built my car it had 100 mm clearance under the Sump and 125 mm from the chassis to the road.

Then I noticed the steering was VERY twitchy and the bottom wishbone was not horizontal.

So I lowered the car which resolved the steering/wishbone issue but brought the sump to within approx' 75 mm of the road.

I've driven it like that ever since (about 6000 miles) and apart from avoiding speed bumps it doesn't cause me any problems.

I've never hit anything with the sump but it has collected scars from stones etc... Nothing has even come close to puncturing the sump or causing any problems.

[Edited on 23/10/19 by JAG]

My sump is flush with the underside of the chassis rails. I have a cross member just in front of the leading edge of the sump to protect it from stones and suchlike.
The ride height is 100mm at the engine and 110mm at the diff area. 95mm under the nose.

Paul G

Anything lass than 4" 100mm is going to be trouble and you will still need to be careful. I've had light grounding in the past at 4". The worst speed humps are the blobs in the middle of the carriageway - they are by design 6" in height and I have grounded my MX5 more than once. You need to steer to one side of these so two wheels go up the hump to give the required clearance.

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Originally posted by chillis
Anything lass than 4" 100mm is going to be trouble and you will still need to be careful. I've had light grounding in the past at 4". The worst speed humps are the blobs in the middle of the carriageway - they are by design 6" in height and I have grounded my MX5 more than once. You need to steer to one side of these so two wheels go up the hump to give the required clearance.

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quote:

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Originally posted by chillis
Anything lass than 4" 100mm is going to be trouble and you will still need to be careful. I've had light grounding in the past at 4". The worst speed humps are the blobs in the middle of the carriageway - they are by design 6" in height and I have grounded my MX5 more than once. You need to steer to one side of these so two wheels go up the hump to give the required clearance.

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IIRC the sump in my Pintoengined MK Indy was approx. 100mm from the ground and the lowest edge of the T9 bell housing just below. Did 3,000 miles without an issue. Took care driving over speed bumps and avoided pot holes. Might have got away with lowering the car a little, but it drove OK as it was so I chose not to mess around.

Today i moved engine 10mm up and it will sit around 11 - 12cm above ground - reading all this opinions guess it will be OK.....

..don't forget ..take front springs off shocks ..
refit shocks no springs ..
lower car till sump just off ground ..
now shim out your shocks with bump stops (skateboard wheels are good)..
now the car should rest on bump stops no springs with a few cm sump clearance..
refit springs
Also make sure shocks are long enough for good droop ...

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Originally posted by johnemms
..don't forget ..take front springs off shocks ..
refit shocks no springs ..
lower car till sump just off ground ..
now shim out your shocks with bump stops (skateboard wheels are good)..
now the car should rest on bump stops no springs with a few cm sump clearance..
refit springs
Also make sure shocks are long enough for good droop ...

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quote:

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Originally posted by johnemms
..don't forget ..take front springs off shocks ..
refit shocks no springs ..
lower car till sump just off ground ..
now shim out your shocks with bump stops (skateboard wheels are good)..
now the car should rest on bump stops no springs with a few cm sump clearance..
refit springs
Also make sure shocks are long enough for good droop ...

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Complain to the council. The legislation permits a maximum height of 100mm for road humps. The DfT also recommends a height of no more than 75mm, except at Raised Junctions, where the maximum recommended is 100mm. Outside these limits, they can legally be considered an obstruction of the highway.

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My father in laws caterham sits 6" off the ground to the chassis. Caterhams do have a very low hood line so perhaps part of this is to compensate for having to sit the engine down low in the engine bay. My locost is loosely based on his car and sits at the same height. I've got 3 3/4" clearance to the sump