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Does your rear end (oo err) take off when pressing-on over a 'crest and dip' in the road? - Ride/Handling/Suspension/Brakes/Wheels/Tyres - The Lotus Forums #ForTheOwners Jump to content


Does your rear end (oo err) take off when pressing-on over a 'crest and dip' in the road?


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Hoping I have phrased the title correctly.  On occasion, when pressing-on a little the rear end will 'hop' when the road surface has a small 'crest' before a 'dip' in the road.  I notice it locally in a couple of places.  My Golf GTI glides over the same sections.  My 911 Turbo used to hop (to a lesser degree) over the same crests/dips.

What needs to be adjusted to compensate for this?  Is it the rebound settings on the Nitron 3-ways? Or should the springs have more travel to be able to be able to ‘fill the void’ between u/s tyre and road surface in dip? 

*Note this is not a bump stop feel where the suspension bottoms out.  It feels more like the springs don’t push the wheel down fast enough into the dip that surprised the car immediately after the crest.

Thoughts? Opinions?

 

 

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  • Jcx changed the title to Does your rear end (oo err) take off when pressing-on over a 'crest and dip' in the road?

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When discussing 410’s with Hoffman’s before buying, the comments were that they felt the standard factory set up on the rear was perhaps a little skittish and I would agree. I played with easy to get at top two setting adjustments and found that when softening, it actually added to the sensation and hardening didn’t really have the desired affect (front end just felt solid rather than nimble) much as you describe with the springs not able to do what was needed. I am lead to believe that Chris at Hoffman’s is very well versed on how to help this phenomenon, but I haven’t asked the question yet, but my thoughts were the ‘rebound’ (the awkward one!) setting is probably what needs attention too.

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I was hoping that the ‘rebound’ (the awkward one!) setting was probably the answer too! 🙂  I suspect the phenomena is also somewhat consistent in cars with engines towards the back as this layout necessitates a firmer spring at the back.

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On 19/02/2021 at 15:28, Jcx said:

I was hoping that the ‘rebound’ (the awkward one!) setting was probably the answer too! 🙂  I suspect the phenomena is also somewhat consistent in cars with engines towards the back as this layout necessitates a firmer spring at the back.

That’s logical. My car will be in a a week or two for oil change at 1200 miles, I’ll see what I can find out and report back.

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If I understand this correctly, do the rears lose contact with the road when this happens? Maybe this is due to the fact that there is a limited droop travel on these cars?

General rule with the rebound is that the more you give, the slower the damper reacts. So in your case you want it to react quicker which means you need to make it "softer" if that makes sense (adjust towards -). That however will not solve anything if there is not enough droop to achieve contact and damper is already fully decompressed. 

Apologies if I didn't really get what you meant. 

 

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Yes, you do understand correctly.  I tweaked the front high-speed compression settings by first one + click on Saturday and then another + click on Sunday.  I subsequently tested the results on a couple of client visits.  I *think* it was improved after the first but not fixed hence the second click.  I think the latter did cure/all but cure the problem.  It was certainly more glued at the front over very uneven surfaces with some subsidence.  and I suspect by keeping better balance at the front, the rear is less able to rotate (up and down rather than side to side) about the front axle.  Net-net the car felt more planted.

I had previously softened my front and rear high-speed compression to make the car softer over bad roads.  it was a success but I suspect I may have induced this rear hop.  having stiffened the front, while leaving the rears in their softer setting, it still rides nicely but feels more glued down.  it also turns in better where on occasion before I felt a little understeer on corner entry when really pressing on into a tight right-hander.

If there are experts out there who have a more educated view to share, I’d love to hear it as I am just feeling my way through trial and error.  I am just a bloke having a go and sharing the reasons trying and the results.

 

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@Jcxso your rear hopping issue over crest is cured by  adding two clicks at front HS?  but wouldn't it make it feel harsh when going over the crest?   I was thinking that if this is an issue of the rear wheel not able to return to the ground fast enough after the crest, woudn't it be softening the rear rebound helping it?   I am having issue in places with manhole cover giving a dipped surface, I feel harsh running over them with the stock setting, I soften it by 1 click both front and rear but I feel it has taken too much and feel too soft, I am going to return the rear back to normal and try again.   

My current settings (from full hard) are:

F/R LSC:  -3/-2
F/R HSC: -11/-12
F/R ReB: -9/-13

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@nordschleife666I so wish i was more knowledgeable about this.  I *think* that firming up the front HS Compression has reduced the car's want to rotate (rear over front) in much the same way that a child might do a forward roll (bum over head). So, if the front can't dip or tuck in like it did, the rear can't rise or hop like it did.  That is my theory.  Likewise if a child can't tuck his head in low, he can't rotate his bum off the ground to do his roll. 

I have lost count what my absolute settings are.  there are two bits of road that are the worst for the hop.  i drove one on saturday and it was better than it was.  i need to drive both again now with the revised settings.

I have not changed the ReB settings from default.

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@Jcx Right, I got your point now.  Keep us posted on the development.  trying all these different settings are so much fun and learn a lot, albeit time consuming :) I firm up the rebound becasue previously I had experienced hopping while exiting and accelerating out of tight corners and also I felt second motion after going over joints on highway.  Firming up the rebound did solve that.  

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Thats great to know about your rebound settings changes.  If i dont cure my issue with the changes to the front i may try the rebound too.

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