Hodor
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| posted on 23/8/16 at 08:39 PM |
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Bottoming out
My mk indy with a c20xe redtop is prone to hitting the sump off the road when the road dips and you're going fast enough.
My coilovers are wound pretty far up but I'm thinking of going with stronger springs to provide a bit more resistance. Question is, will this
work or will it screw up my handling?
I need to take my coilovers apart to find out the spring rating.
[Edited on 23/8/16 by Hodor]
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theduck
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| posted on 23/8/16 at 08:47 PM |
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How much clearance do you have between the sump and the ground?
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Hodor
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| posted on 23/8/16 at 09:11 PM |
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8.7cm, or about 3 1/2 inches if you're over 40.
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nick-york
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| posted on 23/8/16 at 09:23 PM |
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Hi. I've got exactly 2 3/4 inches clearance at my lowest point and all I ground on are certain types of speedhumps going slow.and yes I'm
just over 40! 😆😆
[Edited on 23/8/16 by nick-york]
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bi22le
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| posted on 23/8/16 at 09:48 PM |
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3.5" should be ok and it helps if that lowest part is between the front wheels. What do you mean by having the springs wound up? The collar is
compressing them loads while parked or that they are quite high on the shock body? Do you know what springs you should have?
Do you have single adjustable socks?
Track days ARE the best thing since sliced bread, until I get a supercharger that is!
Please read my ring story:
http://www.locostbuilders.co.uk/forum/13/viewthread.php?tid=139152&page=1
Me doing a sub 56sec lap around Brands Indy. I need a geo set up! http://www.youtube.com/watch?v=EHksfvIGB3I
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TheHighlander123
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| posted on 24/8/16 at 07:46 AM |
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Have you got a shortened sump?
That's what I have on mine as the roads up here are terrible.
Fitting stiffer springs would change the handling but you could counter it with geometry settings I would think.
Westfield SEIW 1700 Forged crossflow, twin 40s etc etc etc - Now about to do a ZX9R
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adithorp
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| posted on 24/8/16 at 07:47 AM |
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3 1/2" under the sump should be enough. Winding up the platforms just raises the ride height but won't affect the stiffness. If your sumps
hitting on bumps (assume you mean bumps in the surface, not speed humps) from that, it's probable that your springs are too soft. The rate is
normally marked in the top/bottom face if it's not worn off.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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TheHighlander123
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| posted on 24/8/16 at 08:12 AM |
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Also what type of coilovers do you have?
Westfield SEIW 1700 Forged crossflow, twin 40s etc etc etc - Now about to do a ZX9R
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motorcycle_mayhem
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| posted on 24/8/16 at 08:58 AM |
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3 1/2" would result in sump destruction where I am, even with the lowest point aligned with a wheel axle. Some of the calming measures here have
a central hump, wheel passage either side with concrete ledges defining the passage across it.
Plenty of exhaust components left behind by 'normal' cars, let alone sporty types. Most folk around here are doing the school run in
hhuuuuuge SUV's, at very high speed, while texting - obliviously driving over the measures.
You may well have to increase the spring rate/height - change it when you get to the track if it upsets the thing up too much.
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adithorp
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| posted on 24/8/16 at 10:05 AM |
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The op isn't talking about speed humps though is he.
quote:
Originally posted by Hodor
...when the road dips and you're going fast enough...
[Edited on 23/8/16 by Hodor]
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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mackei23b
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| posted on 24/8/16 at 10:52 AM |
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Hi run 6.5cm - 7cm clearance with the Cateringvan.....
The VX is not the lightest of engines, do you know your spring rates front and rear?
The Caterhams run:
150lb and progressive rear springs on the entry level cars
250lb/215lb on the Tracksports and "250lb all round with the R300s.....
Though all the rates will be difference depending on the suspension geometry, for example the rear Dampers are vertical and on a dedion tube in the
Caterham......so it is not a like for like comparison.
It may also be work looking at your damping?
Cheers
Ian
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Hodor
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| posted on 24/8/16 at 11:43 AM |
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Thanks for the input folks. I'll check on the spring rates tonight. I'll also post a picture to clarify my suspension setup. And it is
when travelling along and the road dips then rises again i have the issue, the compression of the springs doesn't prevent the sump from hitting
the road. Probably stands to reason that i need stiffer ones.
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johnemms
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| posted on 24/8/16 at 04:29 PM |
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If your front bottoms out it simply means you got no bump stops fitted in your coil overs..
My front end has little compression but plenty of droop 
Stiffer springs are not a cure for excess travel ...
[Edited on 24/8/16 by johnemms]
Own chassis & Build - First time pass!!
"7's" aren't really "cars", they are 'experiences"
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Hodor
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| posted on 24/8/16 at 08:32 PM |
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quote:
Originally posted by johnemms
If your front bottoms out it simply means you got no bump stops fitted in your coil overs..
[Edited on 24/8/16 by johnemms]
That's a good point, checked and i have some there, although not very big. It's clear that they are never troubled as there are no marks
on the top of the dampers.
Pic below of the front coilover. Couldn't find a marking on the spring to tell me the poundage.
 
Description
Can you elaborate on this please, what do you think is?
quote:
Originally posted by johnemmsStiffer springs are not a cure for excess travel ...
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johnemms
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| posted on 24/8/16 at 09:19 PM |
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A pair of old skateboard wheels fit nicely inside coils and do a great job...
I bottomed out and busted sump and engine mounts...
All sorted now
Own chassis & Build - First time pass!!
"7's" aren't really "cars", they are 'experiences"
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Sam_68
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| posted on 24/8/16 at 09:59 PM |
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quote:
Originally posted by johnemms
Stiffer springs are not a cure for excess travel ...
True to a degree, but if you're regularly using enough of that excess travel to be bottoming out, then it does imply that you spring
rates may be too soft: bump stops should only really come into play as a 'safety net', for the worst of bumps and kerbs.
OP: if you do look at increasing your spring rates, then the best way to avoid badly upsetting handling balance is to keep the same ratio of spring
stiffness front:rear.
So, for example, if you have:
Current springs: 200lb front: 130lb rear
Ratio = 200/130 = 1.54:1
New front spring of 230lb would require new rear spring of 230/1.54 = 150lb (near as makes no difference).
If you've got a front ARB only, then things get a bit more complicated and you may need to compromise between roll and ride rates (or fit a
stiffer ARB in proportion), but it's still a fair starting point.
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Hodor
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| posted on 31/8/16 at 08:52 PM |
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Again, thanks for input.
OK, so one skateboard purchase later and I can now jump on the chassis and the new and improved bump stops are doing what they should and the sump
doesn't hit the ground. All good. so far. Thanks for the tip John.
Because I can't tell my spring rates, I'm going to throw £100 at a new set of springs of the "correct" rating.
However, searching on here reveals that "correct" is subjective. Can anyone running an MK indy with CEC please let me know their spring
rates, front and rear? Holiday snaps of the wife for the winner.
So far I have deduced range would be about 300-350 lb front, 200-250 rear.
Much obliged.
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johnemms
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| posted on 1/9/16 at 06:19 AM |
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Original Rons Locost Zetec - 250lbs front ..
Spring lbs will depend on angle of shocks - my rear are vertical live axle so 150lbs are what i use.
Procomp adjustable dampers all on zero full soft for road.
Can adjust shocks to rock hard but still have a fast droop for max road contact.
Also using A021 185.70.13 for sump clearance with the benefit of extra suspension from 70 sidewalls..
Bump stops fitted to rear after bottoming out and shearing handbrake cables when 2 up..live axle..
Bump stops fitted to front after high speed road compression took out sump and mounts.
Setting too high with little or no droop = no road tyre contact over bumps..
Front has good fast droop.. compression only limited by sump clearance..
Wrong shocks = poor or no adjustment = poor or no droop..
Give Procomp Motorsport a ring.. 0121 350 3258 
Shocks made to measure for a seven with proper dial settings - damper oil - fast droop - springs - can be repaired/rebuilt end of season etc..
Sound like a bloody advert..
[Edited on 1/9/16 by johnemms]
Own chassis & Build - First time pass!!
"7's" aren't really "cars", they are 'experiences"
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40inches
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| posted on 1/9/16 at 07:58 AM |
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My MK has 275 front, 175 rear as supplied by GAZ for a BEC.
After fitting the Jag engine I thought I would have to fit stiffer springs, but they are fine as is
We have some of the roughest roads in the country around here The only problem I have is running out of
travel on full extension on the rear shocks.
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Bluemoon
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| posted on 1/9/16 at 09:25 AM |
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are you using the designed for tire diameter? It could be your static ride hight is lower than intended...
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