Slippery When Wet - Wheels, Tyres, Suspension & handling/etc - MX5Nutz Forum

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Slippery When Wet


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#1 JD13

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Posted 12 June 2020 - 07:18 PM

I was out at a track day on Wednesday of this week (Mallory) in my charged mk1, and had real problems in the wet. The track was wet and slippery (constant drizzle, but not heavy rain) and my back end struggled to grip on the corners - so much so that I spun on the first sighting lap hairpin when going very slowly. I'm new to track days (this was my third) so am not sure what the problem is. Could it be that the car is too low (it's a low as I can get it with rolled arches) - the wishbones are pointing up, so far from horizontal. The camber is the minimum I can get it with the car sat so low. Pressure in the Nankang ns2r tyres (when cold) was 30psi. There is however a slight stretch on the 15x8 rims. The Meister R coilovers were set to very hard, but didn't make much difference when I adjusted this to be very soft. Oem ARBs. The car is intended to be a track only car, so just want the best ride height for track use. Am very happy with tyres in the dry, and am led to believe they are also good in the wet. Is it the height that is likely to be the problem (and having it as low as possible is not the best idea), or is it the mild stretch on the tyres - any sensible suggestions welcome!
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#2 Quinvy

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Posted 12 June 2020 - 08:11 PM

I'm no expert, but having the wishbones facing up can't be good? And I can't imagine you have much travel at the back?


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#3 JD13

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Posted 12 June 2020 - 09:01 PM

I've read conflicting things about the wishbones being horizontal- some day it's vital, but others say that for a track car it should be as low as possible, providing there's not too much camber and there's enough travel in the coilovers. I don't think suspension travel was causing the issue, so I guess it comes down to whether the car being so low is somehow causing the problem (I'm not sure why having horizontal wishbones is so important), or if its the minimal tyre stretch and sight camber? I know you can get adjustable arms that would allow the camber to be further reduced whilst keeping the car low, or should I just raise it up, or swap the tyres for ones that aren't stretched?
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#4 Quinvy

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Posted 12 June 2020 - 10:32 PM

I've read conflicting things about the wishbones being horizontal- some day it's vital, but others say that for a track car it should be as low as possible, providing there's not too much camber and there's enough travel in the coilovers. I don't think suspension travel was causing the issue, so I guess it comes down to whether the car being so low is somehow causing the problem (I'm not sure why having horizontal wishbones is so important), or if its the minimal tyre stretch and sight camber? I know you can get adjustable arms that would allow the camber to be further reduced whilst keeping the car low, or should I just raise it up, or swap the tyres for ones that aren't stretched?



As you are using Meisters why don't you message Jerrick. He is an expert on this kind of stuff, and will know how to help you.
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#5 Zed.

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Posted 12 June 2020 - 10:48 PM

how low is the car @JD13?

 

is there any further suspension compression from the static hight?

 

what dampers / springs are fitted?

 

Rich.


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#6 boosted

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Posted 13 June 2020 - 01:54 AM

Pictures of the car will help.
Ive driven on ns2rs in torrential rain and theyre ok... 125 miles on track and no spinning...
Gotta be your set up...sounds like your way to low to me.
2nd pic my mate in a na 5 on same track day on r888r....his set up is flat wishbones white line arbs front n rear.
He only spun once and that was me. I let him think he caught me up and when he went by i sped up...lol...he gonna spin...and he did.
Also on a wet day feed the power on the throttle pedal. 39cda2ad82a7974dfc1672332bbd89f6.jpg6b8c0d25548e5f8a7ba4f4680df3ae74.jpg

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#7 noobie

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Posted 13 June 2020 - 06:37 AM

Also, what is the minimum camber you are actually running?


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#8 JD13

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Posted 13 June 2020 - 07:37 AM

I don't think it's the tyres themselves, but does the stretch on them make a big difference? There's about 2cm of travel in the meisters when I push down on the rear. I've changed the height slightly since the last adjustment, and can't get an accurate measurement with a spirit level and protector! - I'd guess at -2deg. Height at rear from hub to arch lip 290mm. Distance from floor to bottom of pinch weld 85mm. I suppose my question is, can the car be too low, and why? - if I could reduce the camber, by using camber adjusting arms, do the wishbones really need to horizontal?
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#9 JD13

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Posted 13 June 2020 - 07:43 AM

@ boosted. Am jealous of your pics of you driving in the rain - I was struggling to keep the back end from sliding even at very slow speeds (30mph round Gerrards).
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#10 dadbif

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Posted 13 June 2020 - 08:24 AM

Roads/tracks are always extremely slippy when first rained on after a long dry spell
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#11 JD13

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Posted 13 June 2020 - 09:11 AM

I do get that, but none of the other cars at the track day seemed to be having any problems- whilst they weren't going full pelt round the corners, and two cars spun off, they didn't seem to be having the same problems as I was. It was like the back end was on ice (no problems at the front). I felt like I was having to drive ridiculously slow. I'm just not sure what the best way is to diagnose the problem - is it just a case of raising her up and seeing if she settles down?
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#12 Quinvy

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Posted 13 June 2020 - 11:07 AM

Like I said before, speak to Jerrick. He's on here, or you can email him, address on the website.

https://www.mx5nutz....p?showuser=1488
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#13 Zed.

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Posted 13 June 2020 - 11:34 AM

firstly, do you want a car that 'looks' or a car that performs?

 

2 diferent things :yes:

 

I guess from the 'stretch' & ride hight comments its for looks :unsure:

 

 

 

 

 

lowered with little or no remaining suspension travel is same as having no suspension = waste of ~£700 on your misterr kit. 

car needs to be able to move :driving:

 

to hard suspension damping = bouncing or sliding (great for instagram photos BUT slow :rolleyes:  also = spinns :wallbash: )

same with too hard anti-roll bars....

 

 

 

 

Roads/tracks are always extremely slippy when first rained on after a long dry spell

+1 :thumb-up: 


also (to me) 30psi is too much, for wet I'd be running ~23psi (or even less :whistle: )

 

when tyres warm the pressure increases...

 

lower pressures let the tyre warm up so it grips as opposed to being cooled by the the water - from competitive rallying background NOT trackdays :yes:

 

 

Rich.


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50 Shades of Silver. '91 NA6CE, Not a show car :driving: 
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Bodger :ph34r:

https://mighty5s.com...silver-na-eunos


#14 JD13

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Posted 13 June 2020 - 12:15 PM

Thanks for this input. I definitely want handling over looks - shame though, coz the car looks great at the moment. The tyres are almost brand new, but next time the ones I buy won't need to be stretched. Interesting comments regarding pressure - in the dry I find that they need to be about 30psi to grip well, but hadn't appreciated that they needed to be so much less in the wet.

I'd always assumed that being lower would be better, in terms of centre of gravity etc., but I'll now be raising her up so the wishbones are horizontal in time for the next track day - Castle Coombe next week.
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#15 dadbif

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Posted 13 June 2020 - 01:21 PM

I run 25 psi all the time
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#16 boosted

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Posted 13 June 2020 - 01:30 PM

Alignment? After lowering did you get a it checked? Rear toe out is a big no no.

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#17 Slampen

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Posted 15 June 2020 - 06:43 AM

32cm rear and 31cm in front are heights that is known to perform good on Mk1/NA.

That is measured from hub to fender.

 

  1. Adjust your height to 32 and 31
  2. Set alignment to recommendations from FM/SuperMiata.
  3. Report back

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#18 Rasc

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Posted 15 June 2020 - 11:31 AM

Alignment? After lowering did you get a it checked? Rear toe out is a big no no.
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This ^^

All the talk about as low as can go, an estimated camber, readjustment of height and only now we talk about alignment! Get someone that understands MX5 fast road / track settings and get them to set it up. Then as Slampen says report back, it needs a base line.
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#19 JD13

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Posted 15 June 2020 - 09:47 PM

I did have the alignment done once it was lowered, but then I had to raise her up by 0.5cm last week to get out of my garage without scraping the frame rails, so the camber would have changed slightly. Anyhow, I've been out tonight changing the height to 31 at the front and 32 at the rear. Unfortunately won't get chance to get the alignment done again before Friday's track day, but will get that done ASAP. Hopefully raising the ride height and lowering tyre pressure in the wet will solve my problem. Cheers for the advice.
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#20 Rasc

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Posted 16 June 2020 - 08:42 PM

Keep us informed of how it performs.

Also getting the “alignment done” doesn't mean much unless it’s carried out by an experienced place or individual that know how to set a MX5 up. May be worth posting up your proposed settings for comment first.
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